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<tc^ ., 



TUE 

ELECTRO-PLATING 

AND 

ELECTRO-REFINING OF METALS 






o 



THE ELECTRO-PLATING 



AND 



ELECTRO-REFINING OF METALS 



BEING A NEW EDITION 
OF ALEXANDER WATTS ''ELECTRO-DEPOSITION'' 

REVISED AND LARGELY RE- WRITTEN BY 

. ARNOLD PHILIP 

Assoc. K.S.M. B.Sc. A.I.E.E. F.LC. 

PRINCIPAL ASSISTANT TO THK ADMIRALTY CHBMIST, FORMERLY CHIBr CHSMIST TO 
THB BNGINKBRINO DBPARTMBNTS OF THB INDIA OFFICK, AND SOMBTIMB 
ASSISTANT PROPBSSOR OF BLBCTRICAL BNGINBBRING AND APPLIBD 
PHYSICS AT THB HBRIOT-WATT COLLEGB, EDINBURGH 

SBith nnmtroiui iUnstratione 




^^]ui 



NEW YORK 

D. VAN NOSTRAND COMPANY 

23 MURRAY AND 27 WARREN STREETS 

LONDON 

CROSBY LOCKWOOD AND SON 

1902 

\AU Rights Reserve^ 



I 



Us.xx J 7 V0«? .OSL 




-ihtuu^*^ ^im,-/^ 



■H-^.i\^- 



1' *^ r ^ 



JUN 20 i9tr ?. 



PREFACE. 



I UNDERTOOK originally to edit the late Mr. Watt's well- 
known work on Electro-Deposition, and to write a 
farther amount of about one hundred pages, but gradually 
(and, as I think, unavoidably) this amount expanded into 
two hundred and twenty pages of fresh matter. At this 
point the Publishers sympathetically but firmly inteiTened 
by placing their veto upon any further extension. 

The present edition appears under a modified title, and 
has for convenience been divided into two parts — namely, 
Part I, or Electro-Plating, and Part II., or Electro- 
metallurgy. The second part, however, has included in 
it a description of the methods of coating iron with zinc 
electrolytically. It might be considered that this subject 
should be more correctly included in the section on 
Electro-Plating, but the large scale upon which the work 
is conducted nowadays, and the fact that at present it 
represents the only successfully practised process for the 
electrolytic treatment of zinc, have led to its being given a 
place in Part 11. On the other hand, the whole of the 
subject of the electrical extraction of metals from their 
ores has — with the single exception of the electrolytic 
smelting of aluminium — been excluded from the present 
volume, partly because of the want of room, but largely 
because of the unsatisfactory state in which this portion of 
electro-metallurgical technology still exists. 



yiU PBBFAOB. 

That portion of the new matter in this edition which is 
original work, and which I believe to be of some importance, 
is contained in Chapters II. and III. of Part 11., and is an 
attempt to systematise the electro-refining of copper — and 
(it may be added) of all metals, from the financial side — 
for a similar treatment is with very slight modifications 
capable of being applied to the electrolytic refining of any 
other metal, bat owing to want of space has not been 
attempted here. I have to thank Mr. J. H. Brinkworth, 
of Bristol, very heartily for his kind a^ssistance in checking 
some of the numerous calculations contained in the chapters 
dealing with this portion of the subject. 

Two guiding principles which I have endeavoured to 
follow will, it is hoped, be consistently apparent in those 
portions of this work for which I am responsible. The first 
is the neglect of theory, or at least its treatment in the 
most superficial and sketchy manner. This is necessitated by 
the narrow space limits, and is also desirable as enforcing 
the fact that a technical text book cannot, and should not, 
deal with explanations of the underlying theory, but should 
assume them. The second principle of treatment is the 
constant recognition of the importance of the question of 
cost. Financial success is the only basis upon which 
technology can exist. 

The alterations which have been made in this edition 
are chiefly as follows : — Chapters I., II., III., and V. of 
Mr. Watt's 1889 edition have been taken out and replaced 
by Chapters I. and II. of the present edition. The 
remainder of the volume, up to the end of Part I. of the 
Appendix on Electro-Plating, is (with the exception of 



PBBFAOB. * IZ 

page 440) entirely Mr. Watt's work, and only differs 
from the 1889 edition in that the matter in Chapters 
XXVL, XXVII., and XXVIIL, as weU as Part I. of the 
Appendix, has been arranged in a somewhat different 
order. Part II. of the Appendix on Electro- 
Plating is new, with the exception of those parts on cobalt, 
which are from the 1889 edition. The historical remarks 
on the electro-metallurgy of copper, consisting of 19 pages 
in Chapter I. of Part II. of this edition, are retained from 
the thirty-three pages of Chapters XXIV. and XXX. of the 
1889 volume. The remaining seven chapters on electro- 
metallurgy are entirely new, with the exception of an 
account of Keith's process of electrolytically refining lead 
in Chapter YL, an account of Cowles' process of producing 
alloys of aluminium in Chapter YIL, and a description of 
Garcia's and of Montagne*s processes for recoveiing tin from 
waste tinned iron in Chapter V. 

As regards the bulk of the volume, the net result (it 
will be seen) of the revision to which the work has been 
subjected is the enlargement of the text by about one 
hundred pages. Where necessary to bring the work up to 
date, new illustrative diagrams have been freely introduced. 

ARNOLD PHILIP. 

TBM ORBMIOAL LABOBATOBY, 

H.H. DOOXYASD, POUTSMOUTH. 

Juiy ZUt, 1902. 



PREFACE 

TO FIBHT EDITION OF " ELECTBO-DEPOSITION.* 



In contemplating the present work, the Author's desire 
was to furnish those who are engaged in the Electro- 
Dbposition of Metals, and in the equally important 
department of Applied Science ELEcrrRO-METALLURGY, 
with a comprehensive treatise, embodying all the practical 
processes and improvements which the progress of Science 
has, up to the present time, placed at our command. 

While the long-continued success of the Author's former 
work upon this subject, "Electro-Metallurgy Practically 
Treated " — now passing through its Eighth Edition — testi- 
fies to its having filled a useful place in technical literature, 
the art of which it treats has during recent years attained 
such a high degree of development, that it was felt that a 
more extended and complete work was needed to represent 
the present advanced state of this important industry. 

In carrying out this project, the Author^s aim has been 
to treat the more scientific portion of the work in such a 
manner that those who are not deeply learned in Science 
may readily comprehend the chemical and electrical prin- 
ciples of Electrolysis, the knowledge of which is essential to 
those who would practise the art of Electro-Deposition with 
economy and success. He has also endeavoured to render 
the work thoroughly practical in character in all its most 



ZU PBSFAOE TO FIRST EDITION. 

itnportanfc details ; and having himself worked most of the 
operations of the art upon a very extensive scale, he is 
enabled in many instances to give the results of his own 
practical experience. 

Electro-Metallurgy, which is now recognised as a 
distinct branch of electro-chemistry, has been treated sepa- 
rately, and those processes which have been practically 
adopted, such as the electrolytic refining of cmde copper, are 
exhaustively given, while other processes, now only upon 
their trial, are described. In this section also will be found 
a description of the new process of electnc smelting, as ap- 
plied, more especially, to the production of aluminium and 
silicon bronzes. 

In conclusion, the author tenders his best thanks to 
those who kindly furnished him with information, for the 
readiness and promptitude with which they complied with 
his requests. 

ALEXANDER WATT. 

London, Deetmhert 1885. 



CONTENTS. 



PAET I.— ELECTRO-PLATING. 



CHAPTER I. 

PKELIMINARY CONSIDERATIONS.— PRIMARY AND 
SECONDARY BATTERIES.. 

pagh 
The Electric Current. — Electricity Moving Force. — The Electric 
Circuit. — Sources of Electricity Moving Force. — Chemical Electric 
Batteries. — Magnitudes of E.M.F. of Batteries. — Pola^i^ation. — 
Polarity of Batteries. — Primary Batteries. — The Lalande Cell. — ^The 
Daniell Cell. — Amalgamation of Zincs. — Management of Primary 
Batterie:). — Relative Activity of Primary Cells. — Constancy of 
Primary CelU. — General Remarks on Primary Batteries. — Secondary 
Batteries. — Care and Repair of Secondary Batteries. — Annual Cost 
of Uplceep of Secondary Batteries. — Electrolytes. — Short Circuits.— 
Connection of Batteries in Seties and Parallel. — Ammeters and 
Voltmetere « ; i 



CHAPTER II 

THERMOPILES.-DYNAMOS.— THE COST OF ELECTRICAL 

INSTALLATIONS OF SMALL OUTPUT FOR 

ELECTRO-PLATING, ETC. 

The Thermopile. — The Giilcher Thermopile. — The Cox Thermopile. 

The Clamond Thermopile. — The Dynamo. — Points to be considered 
in Buying a Dynamo.— Care of Dynamo.— Driving Belts. — Starting 
and Stopping a Dynamo. — Cost of Small Dynamos. — Cost (if Motor- 
Dynamos. — Specifications for and Choice of Motor-Dynamos. 

Safety Precautions with Motpre oi Motor-Dynamoe.— Choice of 



X17 CONTENTS. 

PAOK 

Electric Generators of Small Output under Various Circumstances. 
— Comparison of Costs of Primary Batteries, Secondary Batteries, 
Dynamos and Motor-Dynamos. — Costa of Gas Engines, Steam 
Engines and Oil Engines. — Gas Engines run on Producer Gas. — 
Regulating Resistances. — Determination of the Polarity of Genera- 
tors • ..• • • . • • . • • 'SQ 



CHAPTER III. 

HISTORICAL REVIEW OF ELECTRO -DEPOSITION. 

A.nnouncement of Jacobi's Discover^'. -^Jordan's Procees Published. — 
Jordan's Process. — Spencer's Paper on the Electrotype Process. — 
Effect of Spencer's Paper. — Vindication of Jordan's Claim. — Mr. 
DirclES on Jordan's Discovery. — Sir Henry Bessemer's Experiments. 
— ^Dr. Golding Bird's Experiments. — Origin of the Porous Cell . 79 



CHAPTER IV. 

ELECTRO-DEPOSITION OF COPPER. 

Electrotrping by Single-Cell Process. — Copying Coins and Medals. — 
Moulding Materials. — Gutta-percha. — Plastic Gutta-percha. — 
Gutta-percha and Marine Glue. — Beeswas:. — Sealing-wax. — Stear- 
ine.— Stearic Acid. — Fusible Metal. — Elastic Moulding Materidl. — 
Plaster of Paris ••...•..•• 99 



CHAPTER V. 

ELECTRO-DEPOSITION OF COPPER (continued). 

Moulding in Gutta-percha. — Plumbagoing the Mould. — Treatment of 
the Electrotype. — Bronzing the Electrotype. — Moulds of Sealing- 
wax. — Copying Plaster of Paris Medallions. — Preparing the Mould. 
— Plumbagoing. — Clearing the Mould —Wax Moulds from PI NHter 
Medallions. — Moulds from Fusible Metal • • • , .107 



CHAPTER VL 

ELECTRO-DEPOSITION OF COPPER {eontinued), 

Eloctrotyping by Separate Battery. — .Arrangement of the Battery. — 
Copying Plaster Busts. — Guiding Wires. — Moulding in Plaster of 



COKTENTS. ZV 

PAOB 

Paris. — Copying Animal Sabetanoes. — ^Electro-coppering Flowers, 
Insects, Ac.— Copying Vegeuble Sulxstances. — Depositing Copper 
upon Glass, Porcelain, <&c. — Coppering Cloih . • • . . zi8 



CHAPTER VII. 
ELECTRO-DEPOSITION OF COPPER (eontinuedi. 

Electrotyping Printers' Set-up Type. — ^Plumbagoing the Forme. — 
Preparation of the Mould. — Filling the Case. — Taking the Impres- 
sion. — ^The Cloth. — Removing the Forme. — ^Building. — Plnmbago- 
ing the Mould.—Knight's Plumbagoing Process. — Wiring. — Hoe's 
Electric Connection Dripper. — Metallising the Moulds. — ^Adams' 
Process of Metallising Moulds. — Quicking. — ^The Depositing Bath. 
— ^Batteries. — ^Treatment of the Electrotype. — ^Finishing. — ^Electro- 
typing Wood Engravings, &c. — Tin Powder for Electrotyping . 130 



CHAPTER VIIL 
ELECTRO-DEPOSniON OF COPPER {continuedj. 

Deposition of Copper by Dynamo-electricity. — Copying Statues, Ac— 
Lenoir's Process. — Deposition of Copper on Iron. — Coppering 
Printing Rollers. — Schlumberger's Process. — Producing Printing 
Boilers by Electricity. — Coppering Cast Iron. — Coppering Steel Wire 
for Telegraphic Purpose^.— Coppering Solutions. — Dr. Eisner's Solu- 
tion. — ^Walenn's Process. — Gulensohn's Process. — Weil's Copper- 
ing Process.— Electro-etching. — Glyphography. — Making Copper 
Moulds by Electrolysis. — Making Electrotype Plates from Drawings. 
— Coppering Steel Shot. — Coppering Notes • , • • •147 



CHAPTER IX. 
DEPOSITION OF GOLD BY SIMPLE IMMERSION. 

Preparation of Chloride of Gold.— Water Gilding.— Gilding by Immer- 
sion in a Solution of Chloride of Gold. — Gilding by Immersion in 
an Ethereal Solution of Gold.— Solution for Gilding Brass and 
Copper.— Solution for Gilding Silver.— Solution for Gilding - 
Bronze.— French Gilding for Cheap Jewellery.— Colouring Gilt 
Work.- Gilding Silver by Dipping, or Simple Immersion. —Pre- 
paration of the Work for Gilding.— Gilding by Contact with Zinc, 
.Steele's Process.— Gilding with the Bag 165 



XVI CONTENTS. 

CHAPTER X. 
ELECTRO- DEPOSITION OF GOLD. 

PAGE 

Gilding by Direct Current, or Electro-Gilding.— I'reparation of Gilding 
Solutions.— Gilding Solutions (Becquerer8.—Fizeau'8.— Wood's,— 
M. de Briant's).— French Gilding Solutions.— Gilding Solutions 
made by the Battery Process (De Ruolz's).— Cold Electro-Gilding 
Solutions.— Observations on Gilding in Cold Baths. — Ferrocyanide 
Gilding Solution.— Watfs Gilding Solution.— Recurd'i Giulii.g 
Bath • . 174 



CHAPTER XI. 

ELECTRO-DEPOSITION OF GOLD {eonUnved), 

General Manipulations of Electro-gilding. — Preparation of the Work. — 
Dead Gilding. — Causes which affect the Colour of the Deposit. — 
Gilding Gold Articles. — Gilding Insides of Vessels.— Gilding Silver 
Filigree Work. — Gilding Army Accoutrement Work.— Gilding 
German Silver. — Gilding Steel. — Gilding Watch Movements . 185 



CHAPTER XII. 
VARIOUS GILDING OPERATIONS. 

Electro-gilding Zinc Articles. — Gilding Metals with Gold Leaf. — Ccld 
Gilding. — Gilding Silk, Cotton, Ac. — Pyro-gilding. — Colour of 
Electro-deposited Gold. — Gilding in Various Cu'uurs. — Colouring 
Processes. — Re-colouring Gold Articles. — Wet colour Process. — 
French Wet-colouring. — London Process of Wet-colouring • , 200 



CHAPTER XIII. 

MERCURY GILDING. 

Preparation of the Amalgam.— The Murcurial Solution. — Applying the 
Amalgam. — Evaporation of the Mercury. — Colouring. — Bright and 
Dead Gilding in Parts. — Gilding Bronzes with Amalgam.— Ormoulu 
Colour. — Red-Gold Colour. — Ormoulu. — Red Ormoulu. — Yellow 
Ormoulu. — Dead Ormoulu. — Gilder's Wax. — Notes on Gilding . a 10 



CONTENTS. XVll 

CHAPTER XIV. 
ELECTRO-DEPOSrnON OF SILVER. 

PAOB 

Preparation of Nitrate of Silver. — ^Obflervations on Commercial Cyan- 
ide. — Preparation of Silver Sblntions. — Bright Plating. — Deposi- 
tion by Simple Immersion. — Whitening A.rticle8 by Simple 
Immersion. — Whitening Brass Cloclc Dials, Ac. , • . . 227 

CHAPTER XV. 

ELECfTRO-DEPOSITION OF SILVER {eontinued). 

Preparation of New Work for the Bath.— Quicking SoluUons, or Mercnry 
Dips.— Potash Bath.— Acid Dip6.—Dipplng.— Spoon and Fork 
Work.— Wiring the Work. — Arrangement of the Plating Bath. — 
Plating Battery.— Motion given to Articles while in the Bath. — 
Cruet Stands, ie. — Tea and Coffee Services.— Scratch-Brushing . 24 1 



CHAPTER XVI. 

ELECTRO-DEPOSrnON OF SILVER {eontinued). 

Plating Britannia Metal, Ac— Plating Zinc, Iron, Ac— Replating Old 

Work Preparation of Old Plated Ware.— Stripping Silver from 

Old Plated Articles.— Stripping Gold from Old Plated Articles.— 
Hand Polishing.— Re-silvering Electro-plate.— Characteristics of 
Electro-plate.— Depositing Silver by Weight.— Roseleur's Argyro- 
metric Scale.— Solid Silver Deposits.- On the Thickness of 
Electro-deposited Silver.— Pyro-plating.— Whitening Electro-plated 
Articles.- Whitening Silver Work .258 



CHAPTER XVII. 

IMITATION ANTIQUE SILVER. 

Oxidised Silver.— Oxidising Silver.— Oxidising with Solution of 
FUUnum.— Oxidising with Sulphide of Potassium.— Oxidising 
with the Paste.— Part-gilding and Oxidising.— Dr. Eisner's 
Process.— Satin Finish.— Sulphuring Silver.— Niello, or Nielled 
Silver.— Pink Tint upon Silver.— Silvering Notes . . .277 

b 



XTIU CONTENTS. 

CHAPTER XVIIL 
ELECTRODEPOSITION OP NICKEL. 

PACE 

Application of Nickel-plating.— The Depoatting Tank.— Conducting 
Bods.— Preparation of tlie Nickel Solution.— Nickel Anodes.— 
Nickel-plating by Battery.— Tlie Twin-Carbon Battery.— Observa- 
tions on Preparing Work for Nickel-plating. — The Potish Bath.— 
Dips, or Steep8.—Dlpping Acid.— Pickling Bath • . « .288 

CHAPTER XIX, 

ELECTRO-DEPOSITION OF NICKEL {continued). 

Preparation of Nickeling Solutions. — Adams' Process.— Unwin's Pro- 
cess. — Weston's Process. — Powell's Process. — Potts' Process. — 
Double Cyanide of Nickel and Potassium Solution. — Solution for 
Nickeling Tin, Britannia Metal, dtc. — Simple Method of Preparing 
Nickel Salts. — Desmur's Solution for Nickeling Small Articles • 299 

CHAPTER XX. 
ELECTRO-DEPOSITION OF NICKEL {coniinuei). 

Preparation of the Work for Nickel-plating.— The Scouring Tray. — 
Brass and Copper Work.— Nickeling small Steel Articles.— Nickel- 
ing small Brass and Copper Articles.— Nickeling by Dynamo- 
electricity.— Nickeling Mnllers, Sausage Warmers, Ac. — Nickeling 
BarFittings,SaniUry Work, dto.— Nickeling Long Pieces of Work. 
—Dead Work.— Nickeling Stove Fronts, Ac— Nickeling Bicycles, 
Ac. — ^Nickeling Second-hand Bicycles, Ac. — Nickeling Sword- 
scabbards, Ac. — Nickeling Harness Furniture, Bits, Spurs, Ac- 
Nickeling Cast-iron Work.— Nickeling Chain Work.— Be-Nickeling 
Old Work.— Nickeling Notes • . 309 

CHAPTER XXL- 

DEPOSITION AND ELECTRO -DEPOSITION OP TIN. 

Deposition by Simple Immersion. — Tinning Iron Articles by Simple 
Immersion.— Tinning Zinc by Simple Immersion.— Tinning by 
Contact with Zinc— Koseleui's Tinning Solutions.— ^Deposition of 
Tin by Single Cell Process.— Dr. Hillier's Method of Tinning Metals. 
— Ilesren's Method of Tinning Iron Wire— Electro-deposition of 



CONTENTS. XIX 

rAOB 

Tin. — Roaelear's Solntlon.— Fearn's Process.— Steele's Process.-- 
Electro-unning Sheet Iron. — Spence's Process. — ^Hecovery of Tin 
from Tin Scrap by Electrolysis ••••.«. 339 



CHAPTER XXII. 

ELECfTRO-DEPOSITION OF IRON AND ZINC. 

Electro-deposition of Iron. — Facing Engraved Copper-plates.— Klein's 
Process for Depositing Iron upon Copper. — Jacob! and Klein's 
Process. — Ammonio-salpbate of Iron Solution. — Boettger's Ferro- 
cyanide Solution. — Ammonio- chloride of Iron Solution. — Sulphate 
of Iron and Chloride of Ammonium Solution. — Electro-deposi- 
tion of Zinc. — Wat^s Solution. — Zincing Solutions. — Person and 
Sire's Solution. — Deposition of Zinc by Simple Immersion. — Her- 
mann's Zinc Process ••••••«•• 348 

CHAPTER XXIII. 
ELECTRO-DEPOSITION OF VARIOUS METALS. 

Electro-deposition of Platinum. — Electro-deposition of Cobalt — Electro- 
deposition of Palladium. — Deposition of Bismuth. — Deposition of 
Antimony. — Deposition of Lead. — Metallo-Chromes. — Deposition of 
Alnminium. — Depositioo of Cadmium. — Deposition of Chromium. — 
Deposition of Manganium. — Deposition of Magnesium. — Deposition 
of Silicon • t • • 336 

CHAPTER XXIV. 

ELECTRO-DEPOSITION OF ALLOTS. 

Electro-depositiou of Brass and Bronze. — Brassing Solutions.- Brunei, 
Bisson, and Co.'s Processes. — DeSalzede'ii Processes. — Newton's Pro- 
cesses. — ^Russell and Woolrich's Process. — Wood's Process. — Morris 
and Johnson's Process. — Dr. Heeren's Process.— Boseleur's Pro- 
cesses. — Walenn's Processes. — ^Bacco's Solution. — Winckler's Solu- 
tion. — American Form||Ue tor Brassing Solutions. — Thicls Brass 
Deposits. — Brass Solution prepared by Battery Process • . . 374 

CHAPTER XXV. 

ELECTRO-DEPOSITION OF ALLOTS {continued). 

Electro-brassing Cast-iron Worlc. — Scouring. — Electro-brsRsingWronght- 
iron Work.— Electro- brassing Zinc Worlc. — Electro-brassing Lead, 



XX CONTENTS. 

PACE 

Pewter, and Tin Work. — Observations on Electro-brassing. — Bronz- 
ing Electro-brassed Work. — French Method of Bronzing Electro- 
brassed Zinc Work. — Green or Antique Bronze. — Bronze Powders. — 
Dipping Electro-brassed Work. — Lacquering Electro-brassedWork. — 
Electro-depottition of Bronze. — Electro-deposition of German Silver. 
— Morris and Johnson*d Process. — Deposition of an Alloy of Tin and 
Silver. — Dftposition of Alloys of Gold, Silver, &c. — Deposition of 
Chromium Alloys. — Slater's Process. — Deposition of Magnesium and 
its Alloys. — Alloy of Platinum and Silver.— New White Aliova. — 
Notes on Electro-brassing . • 387 



CHAPTER XXVI. 

RECOVERY OF GOLD AND SILVER FROM WASTE 

SOLUTIONS, &o. 

Recovery of Gold from Old Cyanide Solutions. — ^Recovery of Silver from 
Old Cyanide Solutions. — Extraction of Silver by the Wet Method. — 
Recovery of Gold and Silver from Scratch-brush Waste. — Recovery 
of Gold and Silver from Old Stripping Solutions. — Stripping 
Metals from each other. — Stripping Solution for Silver. — Cold 
Stripping Solution for Silver. — Stripping Silver from Iron, Steel, 
Znc, &c. — Stripping Silver by Battery. — Stripping Gold from 
Silver Work. — Stripping Nickel-plated Articles. — Stopping-ofF. — 
Applying Stopping-off Varnishes. — Electrolytic Soldering. — Solder- 
ing. — Removing Soft Solder from Gold and Silver Work • . 403 



CHAPTER XXVII. 

MECHANICAL OPERATIONS CONNECTED WITH 
ELECTRO-DEPOSmON. 

Metal Polishing. — Brass Polishing. — The Polishing Lathe. — ^Brass 
Finishing. — Lime Finishing. — ^Nickel Polishing and Finishing. — 
Steel Polishing. — Polishing Silver or Plated Work. — Burnishing. — 
Burnishing Silver or Plated Work. — ^Electro-gilt Work • • •419 



CHAPTER XXVIII. 
MATERIALS USED IN ELECTRO -DEPOSITION. 

Acetate of Copper. — Acetate of Lead. — Acetic Acid. — Aqua Fortis.- 
Aqua Regia. — Bisulphide of Carbon.^Carbonate of Potash,- 



CONTENTS. XXI 

PAOB 

Caustic Potash.— Chloride of Gold.— Chloride of Platinum.— 
Chloride of Zinc. — Cyanide of Potassium. — Dipping Acid. — Ferro- 
cyanide of Potasfiiuin. — Hydrochloric Acid. — Liquid Ammonia. — 
Mercury, or Quiclcsilver. — Muriatic Acid. — Nictcel Anodes. — Nicliel 
Salts.— Nitric Acid.— Phosphorus. — Pickles. — Plumbago. — Pyro- 
phosphate of Soda. — Sal-;immoniac. — Sheffield Lime. — Solution of 
Phosphorus. — Sulphate of Copper. — Sulphate of Iron. — Sulphuric 
Acid. — Trent Sand ..->,»• t • » 429 



APPENDIX (PART I.) ON ELEOTRO-PLATING. 

Electro-deposition of Platinum — Platinising Silver Plates for Smee Cells. 
— Electro-deposition of Iron. — Steel Facing Copper Plates. — Coloura- 
tion and Staining of Metals. — Oxidising Copper Surfaces. — Electro- 
deposition of Alloys. — Test for Free Cyanide. — Antidotes and Eeme- 
dies in Cases of Poisoning • • • 441 



APPENDrX (PART U.) ON ELECTRO-PLATING. 

Effect of Nitrates upon Nickel Deposits.— Da ry's Barrel Method of Nickel- 
plating. — Employment of the Barrel Method of Plating for Metals 
other than Nickel. — The Electrolytic Manufacture of Metal-coated 
Paper. — Electro-deposition of Cobalt. — Professor S. P. Thompson's 
Process of Cobalt Deposition. — The Electrolytic Formation of Para- 
bolic Mirrors for Search-lights.—** Areas" Silver-plating.— An 
Hotel Silver-platirg Plant— Aluminium Plating by Electrolysis 
and Otherwi:ie. — Plating Aluminium with other Metals . . . 46c 



XXII CONTENTS. 



PART II.— ELECTRO-METALLURGY. 



CHAPTER I. 

THE ELECTRO-METALLURGY OF COPPER—CHIEFLY 

HISTORICAL. 

PAGB 

Electro-metallorgy. — ^The Electric Refining of Copper by Separate 
Carrent. — Dr. Kilianrs Observatiuns on Electrolytic Refining of 
Copper. — Progress in Electrolytic Copper Refining up to 1889. — 
Elkington'8 Copper Refinery. — Wohlwill's North Grerman Refinery 
at Hamburg. — ^The Biache Refinery. — Hilarion Ronx's Marseilles 
Refinery.— The Oker Refinery.— The Elliott Metal Refining Com- 
pany's Refinery at Birmingham. — Electrolytic Ifeflning in America. 
— Early Attempts at Estimates of Cost of Refining Copper • . 48c 

CHAPTER IL . 

THE COST OP ELECTROLYTIC COPPER REFINING.— 
CURRENT DENSITY AS A FACTOR IN PROFITS. 

Advances in Electrolytic Copper Refining. — Preparing Estimates of 
Cost of Erection of Refinery. — ^Cost of Offices, Refinery Buildings, 
Power Plant, Dynamos, Electrolytic Yats, Electrolyte, Copper 
Anodes, Stock Copper, Copper Leads, Circulating and Purifying 
Plant. —Total Capital Invested, Annual Running Costs, Interest on 
Capital Invested, Depreciation and Repairs, Labour, Melting Re- 
fined Copper, Casting Anodes, Fuel, Salaries of Management 
and Clerical Staff. Rent of Ground. — Importance of Current 
Density. — ^Annual Total Profits.— Examples of Estimates worked 
out — ^Actual Costs of Electrolytic Copper Refineries. — Further Con- 
siderations on Current Density. — Current Density in Copper Con- 
ductors in Electrolytic Refineries 499 

CHAPTER III 

SOME IMPORTANT DETAILS IN ELECTROLYTIC 

COPPER REFINERIES. 

Arrangement of Vats in a Copper Refinery.— Arrangement of Anodes 
and Cathodes in Electrolytic Vats. — The Hayden System. — Best 
Size and Number of Electrolytic Vats. — Avoidance of Short 
Circuits.— Circulation of the Electrolyte.— Heating the Electrolyte 
Voltage and Output of Dynamos for Copper Refining.— Composition 
of Anode Copper employed in Refineries.— Composition of Electro- 



fX)NTBNTS. XXni 

PAOS 

refined Copper. — Composition of Anode F^liidge. — ^Weight of Anode 
Sludge. — Purification ul Electrolyte. — Effect of Organic Matter on 
Copper Deposits. — Formation of ^oduleR and Tree-like Growths. — 
Production of Finished Refined Copper without Re-melting. — The 
Elmore Process. — Copper Refining at High Current Beusitiee. — 
Dumoulin's Process. — Cowper Coles' Centrifugal Process.— Wilde^s 
Centrifugal Process.— Sander's Process.— David's Process.— Tho- 
fehen's Process. — Alan Williams' Theory of High Current Density 
Processes.— The Price of Copper and its Fluctuations . • .524 

CHAPTER IV. 

ELEOTBOLTTIC GOLD AND 8ILVEE BULLION 

REFINING. 

Electrolytic Refinery of Gold Bullion.— Wohlwill's Procesn.— Pforzheim 
Process of Recovering Gold and Silver from Complex Jewellery 
Alloys. — Electrolytic Silver Refining. — M obi us* Process . . • 563 

CHAPTER V. 
THE ELECTROLYTIC TREATMENT OF TIN. 

The Electrolytic Refining of Tin.— The Recovery of Tin from Waste 
Tin-plate by Acid Processes. — The Recovery of Tin from Waste 
Tin-plate by Alkaline Processes. — Properties of Iron Contaminated 
with Tin.— Cost of Scrap and Waste Tin-pUte.— Cost of Collection 
and Carriage . . . t • • • ... 578 

CHAPTER VL 

THE ELECTROLYTIC REFINING OF LEAD. 

Keith's Electrolytic Lead Refining Process for Base Bullion.— Tommasi's 
Electrolytic Lead Refining Process. — Formation of Spongy Lead. — 
Richly Aigentiferous Lead Treated by Tommasi's Process. — ^Refining 
Argentiferous Lead in Lead Nitrate Solution.— Remarks on the 
JUectro-deposition of Lead • • 595 

CHAPTER VIL 

THE ELECTROLYTIC PRODUCTION OP ALUMINIUM 
AND THE ELECTROLYTIC REFINING OF 

NICKEL. 

Properties of Aluminium. — Effect of Mercury on Aluminium.— Electro- 
lytic Smelting of Aluminium from Alumina. — Beroult's Process. — 



XXIV CONTENTS. 

PAOB 

Hall's Process. — Preparation of Pfire Alirmina. — Increase of Purity 
of Commercial Alumininm in Recent Tears. — Minet's Process of 
Smelting. — Bucherer's Aluminium Sulphide Process. — ^The CowW 
Process of Producing Aluminiom Alloys. — The Electrolytic Refining 
of Nickel. — Secret Processes. — Ludwig Mond's Nickel Refining 
Process , . 613 

CHAPTER VIII. 

ELECTRO-GALVANlSINa. 

Nature of Solutions. — Protective Effect of Electro-deposited Zinc. — Firms 
Electro-ftalvanising prior to 1891. — ^Richter's Process. — Oowper- 
Coles' Process. — Employment of Zinc Dust. — Estimates of Cost of 
£lectro-;^alvanising Plant. — Advantages of Electro-galvanising 
Iron. — Pickling and Cleansing Iron and other Metal Surfaces by 
Chemical and Electrolytic Methods. — Removal of Scale from 
Pickling Vats. — Effect of Pressure on Electro-zincing. — Zinc 
Sponge. — Sources of Zinc Dust. — Price of Zinc and Zinc Dust . 631 

USEFUL TABLES. 

TABLV 

T. — Elements, their Symbols and Atomic Weights . . . .651 

II. — Relative Conductivity of Metals 652 

Til. — Specific Resistance of Solutions of Sulphate of Copper . 653 

JV. — Specific Resistance of Solutions of Sulphate of Copper at 50° 

Fahr 653 

v.— Table of High Temperatures 653 

VI. — Comparative French and English Thermometer Scales . 654 

VII. — ^Birmingham Wire Gauge for Sheet Copper and Lead . . 655 

VlII.*>New Legal Standard Wire Gauge 655 

IX.— Chemical and Electro-Chemical Equivalents .... 656 

X. — Specific Gravides of Metals 657 

XI.— Tables of Weights and Measures 659 

XIL— Specific Gravities corresponding to Degrees of Baume's Hydro- 
meter for Liquids heavier than Water 659 

XIII. — Specific Gravities on Baume's Scale for Liquids lighter than 

Water 659 

XrV.— Degrees on Twaddell's Hydrometer and the corresponding Specific 

Gravities 660 

Electrical Units ....•• ... 660 

SUBJECT INDEX 66z 

NAME INDEX 678 






THE ELECTRO-PLATING 



AND 



ELECTRO-REFINING OF METALS. 



PART L— ELECTRO-PLATING. 

CHAPTER I. 

PRELIMINARY CONSIDERATIONS.—PRIMARY AND 

SECONDARY BATTERIES. 

The Electric Current. — Electricity Moving Force.— The Electric Circuit. 
— Source of Electricity Moving Force. — Chemical Electric Bat- 
teries. — ^Magnitudes ol e. m. f . ol Batteries. — Polarisation. — Polarity 
of Batteries. — ^Primary Batteries. — The Lalande Cell. — The Daniell 
Cell. — Amalgamation of Zincs. — Management of Primary Bat- 
teries.— Relative Activity of Primary Cells. — Constancy of Primary 
Cells. — General Remarks on Primary Batteries. — Secondary Bat- 
teries. — Care and Repair of Secondary Batteries. — Annual Cost of 
Upkeep of Secondary Batteries. — Electrolytes. — Short Circuits. — 
Connection of Batteries in Series and Parallel. — Ammeters and 
Voltmeters. — Regulating Resistances. 

It is not the object of this treatise to enter into discussions on, and 
explanations of, the theories of chemistry, electricity and magnetism, 
or the methods of construction and design of dynamos. Such 
questions must be studied in some one or more of the numerous 
excellent text books now existing which deal especially with these 
branches of pure and applied chemistry, electricity and magnetism. 
The present work is intended above all to deal with the question of the 
chemical action of the electric curreut from a practical standpoint and 
all theory is as far as possible omitted, except in its simplest and most 
generalised form. It must not be imagined, however, that the present 
writer wishes iu any way to induce the student of this particular 
branch of applied electricity to consider that the theory of the subject 
is unimportant. The theory is of the greatest value to guide and 
direct experimental work, and it cannot be too strongly urged that 

B 



a PBIMART AND SECONDARY BATTKRIKS. 

every practical technical worker who Is possessed of little or no theory, 
however successful and excellent he may be in his particular branch of 
applied science, will find himself rendered the more capable in carry- 
ing out improvements and rectifying difficulties the greater the amount 
of soond theoretical knowledge he is able to obtain. 

Tlie Blectrie Gnmnt, — For all practical purposes the electric 
cnirent may be considered as being similar to a current of water, and 
the electric conductors in which it can flow as being analogous to 
water pipes, whilst non-conductors of electricity may be represented, 
by analogy, by the solid materials forming the walls of the pipe 
through which the water flows. 

Bleotro-MotlTe Force, or BUetrleity Bffovliis Force. — In order 
that a current of water may flow through a pipe, it is necessary to have 
a water moving force, such as a pump, or a head of water, arranged 
somewhere in the course of the tube through which the water flows. 
And in order that the electric current may flow, it is always necessary 
that there shall be an electricity moving force (or as it is frequently 
written shortly, an e. m. f .) somewhere in the circuit. 

Tbe Blectrie Ctrcnit. — If the reader wiU consider for one moment 
he will find that in all cases where we have a eontinuoug flow of water 
there must be a closed circuit or path,, round which this flow takes place. 
For instance, if a pump and its attached engine (the source of water 
moving force) is raising water from a mine, which water, as it escapes 
from the pump, runs back again down the shaft, we have a case of a 
continuous circuit. Again ,^ in the case of a river, running continuously 
(or nearly so) into the sea and continuously supplied at its sources with 
water from the clouds (which water has- been extracted from the sea 
by the sun) ; the sun is the water motive force and the closed path of 
flow (or the circuit as it is called in the case of electricity) is down the 
river bed, into the sea, up through the air from the sea,, as water 
vapour, transport by the winds as clouds, again a downward path 
through the air on to the land, and once more along the river bed. In 
the case of the electric current we have a closely analogous arrange- 
ment. There must always be a closed circuit, and as electririty can 
only flow in an electric conductor, such as a metal, carbon, or a con- 
ducting liquid, the circuit throughout must consist of one or more of 
these materials continuously connected ; if at any point the connection 
between the conductors is broken by a non-conductor, such as air, 
ebonite, indiarubber, etc., the current must at once ceaae flowing. 

Thus the necessary conditions for a continuous flow of electricity 
are; — 

iflt. A source of electricity motive force or e. m. f. 
2nd. A continuous closed conducting path in the course of which 
the source of e. m. f . is placed. 



SOURCES OF ELECTRICITY MOTIVE FOBOB. 3 

Bowte^m off Btoetrleity MotlTtt Tore: — Practically there axe 
three different t3rpe8 of sources of electricity motive force : — 

1. The electro-chemical battery, generally known as the electric 
battery. 

2. The thermopile. 

3. The dynamo. 

We shall immediately consider the relative merits and importance 
of these sources. 

For technical purposes the prime oonrideratiou in conducting any 
process is economy of both time and money, and as the cost of the 
electric current obtained from any given source depends upon the 
prime cost of the Kencrator, its rate of depreciation, and the cost of 
maintenance, it is of vital importance to consider these matters with 
every care. 

In the writer's opinion the most advantag^us source of electrical 
energy for small work up to perhaps as large a current as about three 
amperes, if the work is turned out at a steady rate, or im large as 
perhaps twice Uiis amount if the output of work is variable and the 
plating i)lant only intermittently used, is a form of the Lalande 
battery manufactured by Messrs. Umbreit and Matthes of Leipzig. 
This refers to the cases most unfavourable to the employment of 
primary batteries, namely, when either cheap electrical or cheap mecha- 
nical power, or both, is to be easily obtained. Under other circum- 
stances, where neither electrical nor mechanical power is to be had, 
the importance of this form of primary battery is greatly increased, 
and it may be employed with advantage imder the most favourable 
oircumstances for currents up to as large as 20 or perhaps 30 amperes. 
In connection with these statements it may be remarked that 3 
amp(Tes is a current sufficiently large to plate satisfactorily about 500 
square inches of surface with gold, or as much as about i€X> to 300 
scjuare inches with silver, or to electrotype with copper, surfaces as 
large as about 30 to 40 square inches. A fuller discussion of the 
question as to the best form of current generator to employ under 
different conditions is given at the end of the next chapter, after all 
the available current generators have been considered uid their 
efficiency, prime cost, and upkeep noted. 

It is now necessary to describe the various forms of primary electric 
batteries which are available for electro-plating and other electro- 
metallurgical work. In the writer's opinion, none of the primary 
batteries, except the modified Lalande cell already mentioned, should be 
for a moment considered for practical work, but owing to the fact that 
this form of cell is of very recent introduction, and as in the larger 
part of the text of this book other forms of battery are contiuuidly 
zeferred to, it is necessary, in order that the reader may oleac]/ follow 



4 PKUIABT AND BBCOHUABV IIATTEBIB8. 

Mr. Watt's remBrks, that u description of the various fomu of 
batteries mentioned shall be jriven here. Moreover, as no doubt many 
cxperimeutalista, amateuix and others, may have in their posseBsion 
Bume one or more of the older forms of electric: butteries, a few words 
on their eoiiHtnictioD and mana^^cmeut may be found useful. 

aiactrle Battartaa.— Aii electric battery depends for its c. m. f. 
npan a cbemical action occmrring within it, and must have three 
CHsential parts. 

I and 2. IVo diSerent conducting bodies, always solid in practice 

unless mercmy ia employed for one. 
3- A liquid which can conduct electricity, bat whicn is chemically 
changed by the passage of electricity through it. (Such a 
liquid is known as an electrolyte. This clasx of liquids is 
further considered on page 3 j . ) 

The liquid is contained in some vessel 
mude of a material upon which the 
electrolyte bus no action, and one end 
of eauh of the two conducting solids is 
immcrued in the liquid. IIil' solids 

II must be prevented from touching oue 
I another ia the liquid. To each of the 
two ends of the conducting solids or, 
us they are called, elements of the bat- 
tery, which arc not immdrved in the 
liquid, terminal surews are attached, 
and these serve to connect the battery 
by means of wires to the apparatus, 
Fig. I.- Single CeUs, eitema] to the biitlerj-, through which 

it is dmirwi to pass an electric cur- 
rent. SueL a simple arrangement of muteriuls forming a battery cell, 
ao jt IS called, is shotm iu ilg. 1, where Z deDotes a pialc of 
metallic due, and P is a plate of platinum ; these are immeraed in a 
solution of sulphuric acid in water contained in a glass vesw-I. The 
bmding screws are not shown, but the eiteroal conductors of copper 
wire are soldered directly to the ends of the zinc and plaUnum trapeo 
lively, which emerge from the liquid. 

Each particular combination of a pair of solid conductors and elec- 
trolyte solution give a perfectly definite electricity motive foree at any 
given temperature, but if tlie temperature is altered, the electricity 
moving force of the ceU is slightly altered ; this alteration, however, 
IB very slight compared with the alteration which tuny oci!ur due to 
changing the material of either one or both of the conducting solids and 
the electrolyte. 

l>>Knlta4« Of &• BUotco-MMtT* roTM* «f BattolM.— The 



UAONTTUDB OF ELEGTBO-MOTIVB FOR0B3 OF BATTFBTES. 



elechro-motive force of any g^enerator is meaBured in terms of the unit 
of electrical pressure or electro-motive force, which is called the volt. 
The actual value of the e. m. f. of any fdngle cell of any electrical 
battery which is employed in practice varies from the highest value of 
about 2*2 volts in a secondary battery, down to about I'D volt in a 
Smee^s cell. It must bo understood that the unit of e. m. f., or 
electrical pressure, is analogous to the unit of head of water, or 
pressure of water, which is usually expressed in so many feet of head. 
The electrical pressure required in electro-plating work varies from 
about 2 volts lip to as much as nearly 8 volts, whilst for ordinary 
house lighting work pressures usually vary from about lOo volts up to 
as high as 250 volts on the lamps. Most people can hardly feel a 
pressure of 100 direct volts, when applied to the hands acroBS the body, 
whilst it is unlikely that 250 volts could give a dangerous shock, unless 
the hands had been previously well soaked in some conducting liquid. 
It must be remembered, however, that these results only A-pply to dirret 
pressures ; alternating pressures at 100 volts may produce very un- 
pleasant sensations with f>ome persons, and especially if the hands are 
moistened with a conducting liquid. These details concerning the 
value of different voltages, are given in order to familiarise the reader 
with some practical ideas of the order of the electrical pressures which 
are employed for most electro-chemical proceBses. 

Electro-motive Forces op the Chief Chrmtcal Batteries. 
Name of cell. Approximate volts. Bemarks on voltage. 

Secondary battery . . r 8 to 2*2 constant. 

Lalande (Cupron elonient) . 0*75 to 085 constant. 

I'l 

2'I 

x'47 



Danieil . 

Bichromate 

Leclancbe 



constant. 

volts fall with use. 
volts fall with use but 
recover on standing, 
volts fall with use. 



It 



» 



tt 



1} 



)i 



}} 



Smee's . • . • . 0-5 to i-o 
Wollaston . . . 0*5 to I'o 

Grove . . . . . 1*6 to 1*9 
Bunsen . . . . . 1*5 to 17 

Minimum Electro-motive Forces Required for Electro-platino 

Beactions. 

Brass about 4 volts. 

Copper (acid bath) 0*5 to 15 

„ (alkaline bath) . . • 3 to 5 

Gold o'5 to I 

Iron (steel facing of copper plates) . .1 to 1-5 

Nickel (on various metals) . . . i'5 to 8 

Platinum 4 to 6 

Silver 0'5 to i 

Zinc (on various metals) . . . . 3 to 8 



»» 



}i 



»» 



»t 



if 



»> 



ti 



6 PRIHART AND fitECONDART BATTBRIR8. 

It will ho noticed from the ahove given details that there is no inng'ld 
cell which can give the e. m. f ., which is required for many electro- 
plating operations, but this difficulty may be readily overcome by 
arranging the batteries in series as it is termed. This method of 
arrangement will be briefly referred to later on, but in the meantime it 
may be noted that by thus arranging a sufficient number of any cells 
in series, any desired e. m. f . may be obtained, and such batteries of 
cells of even the lowest e. m. f . have been built up until very large 
e. m. fs. have been obtained, sufficiently high indeed to need great 
caution in dealing with them to avoid a dangerous shock. For 
all plating purposes it is therefore clear that it is a very simple 
matter to connect in series a sufficient number of the single cells to g^ve 
a battery luiving an ample e. m. f . 

Polarlsatioa of 0«ll«i — Most electrical batteries, when they have 
been connected in a circuit with a fixed resistance, yield a rurreut 
which, although perhaps of amply sufficient magnitude at first, is 
gradually found to decrease in strength. In some cases this variation 
of strength is very marked, and this is the case although the resistance 
of the circuit remains constant. Now the current in an electric circuit 
flows, as is well known, according to Olun's law, which states that 
the resistance of any circuit, or part of a ciixjuit, is defined as the 
ratio of the total e. m. f . in that circuit, or portion of a circuit, to the 
current caused to flow in the circuit. That is, if the renistance of a 
circuit is represented by the letter R, and the e. m. f . by the letter £, 

E . 

whilst the current is represented by the letter C, then the ratio y^ is 

equal to the resistance Bof the circuit, or the relationship is represented 
by the equation, 

E F 

- = R, or, as it may also be 'written = - 

If E is expressed in volts, and C in amperes, R is expressed in ohms. 
This well known equation enables us to readily calculate out muiy 
useful problems. For instance, in the present case, to explain the 
diminution of the current after a cell has been running some little time 
on a constant resistance R, we see that the only way to account for 
the fall in current is to suppose that the value of the voltage £ of the 
cell has diminished, and this is precisely what investigation shows has 
occurred. This decrease of the current is due to one or all of the three 
following causes : — 

ist. The current given out by the cell causes a chemical action to 
occur in the cell, and if the cell is one containing a single fluid, such 
as dilute sulphuric acid (as in the case with the Smee cell), hydrogen is 
deposited on the platinised silver plate, and this coating of the plate 
outside with hydrogen causes it in effect to act with the e. m. f . of a 



POLARITY OP CHEMICAL BATTERIK9. 7 

cell made up with the elemontH of hydrogen and zinc in dilute sulphnric 
acid instead of platinised silver and zinc in dilute snlphorio ; it has 
already been stated that the e. m. f . of the cell prhctically only depends 
upon the nature of tlie elements and the liquid, and the hydrogen and 
zinc elcment.s in dilute sulphuric hare a smaller o. m. f. thsm the 
platinised silver and zinc in the same li(|uid« Therefore by Ohm's law, 
as the e. m. f. has been decrca8<.'d, the current must decreaae 
proportionately, 

2nd. The depotdtiou of the hydrogen upon the platiuised silver plate 
causes the resistance of the cell to be somewhat increased, and therefore 
as K is increased, we again see that by Ohm's law C must decrease. 
This effect no doubt does exist in the Smee cell to some extent, but it 
is not by any means such a powerful factor in reducing the current as 
the first noticed cause. 

The two above-described actions causing the decrease of the current 
gfivjn by a ceU are included in what is known as the polarisation of the 
cell, a term which has nothing except custom to recommend it, bnt is 
always intended to indicate the actions we have just considered. 

3rd. The third cause of the cell's decrease of activity is due to the 
fact that the chemical or chemicals in the solution of the cell become 
changed. Tliis always occurs to a greater or smaller extent in all cells. 
For instance, in the Smee ceU the dilute sulphuric acid is gradually 
converted into a solution of zinc sulphate. In the Daniell cell the 
same action takes place if dilute sulphuric acid is employed, whilst if a 
zinc sulphate solution is used to conomence with, this solution becomes 
more and more concentrated. In the Bichromate cell this change of 
the character of the solution has a very marked effect, and it is also 
less, bnt still noticeable, in the Bunsen and in the Grove's cells. The 
change in the chemical character of the solutions alters one of the 
three things necessary for a given e. m. f., and therefore, as might 
have been supposed, the e. m. f . itself is altered, and always in all 
practical cases it is altered in such a sense as to diminish the e. m. f . 
This cause of alteration of e. m. f . of a cell is very small in the case of 
the secondary battery and the Daniell cell, it is greater in the Bunsen 
and the Grove's cells, and is probably most marked in the case of the 
Bichromate cell, whilst in the Smee it has very little effect. It must 
be understood, however, that this does not mean that the Smee cell has 
a much more constant e. m. f. than the Bichromate ; as a matter of 
fact their rate of fall of e. m. f. may be much the same, but in the 
Smee it is chiefly due to the polarising hydrogen, whilst in the Bichro- 
mate cell it is chiefly due to the alteration of the chemical nature of its 
exciting fluid. 

Foiarlty of Obaniioml Batt«rl«s. — AH the batteries, with the 
exception of the secondary battery, which have been enumerated in th( 



8 PBIMABY AND SECONDABT Bj^TTBRIES. 

foregfCHiig list contain m^tallif zinc as oue of their elemeotH, and it is 
UBeful to note that in every cajw the terminal of the cell coooef^ted to 
the zinc i« the nepitive terminal, that in to aa;, that when couue«te(l in 
drcuit Uie current will flow out from the other or poiutive tenninal of 
the cell and bock Ofcaia in at the negative or rinc terminal. Aa f ar as 
the Hriter in aware, there ia no primary batterj in general use whii^li 
doi-H not contain ziuc, and the xine in always tiie negative temiiniil. 

In order that the references to different batteries in the folloirin^ 
pages may be intelligible, it in necessary to briefly describe tie varionB 
fomui, biit it muHt be understood that the only essentials in a given 
battery are the nature of its elements and its ciciting fluid or fluids ; 
the Jukrtieular arrangement or form of the vcsstlA containing the fluids, 
and the shape and poiuHun of the elements, may be varied almost 
infloitely to obtain certain advantagcsof pacldogot cells, or portability, 
or clieaput«H, or low rewBtance, or the 
contrary for special purposes. In a 
Daniell's cell, for instance, it is of only 
minor importance whether the cell is flat 
and rectungular, or cylindrical in shape, 
and whether tlie amalgamnled ziuc is 
immersed in zinc sulphate solutian con- 
tained in the porous pot with a copper 
sulphate solution outside, in wliich the 
copper is plaoed, (ir the reverse arrange- 
meut ia adopted, with the copper plato 
inside the porous pot containing the 
Fin. 2.-Ciipron Element solution of copper sulphate, whilst 
Cell (Lalande llattery). the zinc is outside in tlie zioe snlphale 
solution ; in cither case the e. m. f. is 
the same, and the cell is a Dauielt celt. 

Primary BattaHas. — The Lalaude (Cupron element), the Dauiell, 
the BuusCD, the Grove, the Leclanchf, the Smee, the Wollaston, and 
the Bichromate cells are all primary batteries, that is to say, they are 
cells which give an electric current without hanng previously had an 
electric current passed through them to charge them. 

TbaXialanda Oall (Cupron element).- Tliiscelt {Fig. z) consists of two 
amalgamated nliects of zinc, which together form the negative element, 
immemcd in u solution of either caustic soda (170 grams of commercial 
caustic soda per litre] or caustic potash (228 grams of commercial 
caustic potash per litre). The makers state thatcaustic potash or soda 
solution of about 19° to Zl" Beaiimc is employed. The positive plate 
of the cell is formed of a mass of cupric oxide, and it is in the 
mechanicHl construction of this plate of copper oxide that the patent 
for that form of Lalaode cell known as the " Cupron element" exists. 



TBS LALANDB CELL. 9 

When the cell is first put up it has an e. m. f . of as much as T'3 yolts. 
This high voltage is said to be due to the presence of oxygen in the 
gaseous orm present with the cupric oxide. If the cell is short 
circuited for a minute or two, however, the volts fall rapidly to about 
0*82 volts, and ihea remain constant at this value imtil the cell is 
completely discharged, that is, until nearly all the cupric oxide is 
reduced to metallic copper, when the volts fall to slightly uAder 07. 

After complete discharge the cupric oxide plate is regenerated by 
removing the reduced plate from the cell, washing it with water and 
leaving it in a dry and warm place, exposed to the air for a period of 
20 to 24 hours. If a temperature of 80** to 150^ Centigrade is em- 
ployed, the copper is fully re-oxidised in from 20 to 30 minutes. The 
plate can then be replaced in the battery, and the cell can once more be 
used. When the caustic solution is exhausted, a yellowish-grey pre- 
cipitate of zinc hydrate is thrown down. The cell can be worked 
after this precipitate is formed, but the e. m. f. is no longer so 
constant as before. The exhausted solution, which oonsiBts of 
caustio alkali saturated with zinc hydrate, should therefore be 
removed and replaced by a fresh solution. The zinc plates, which 
must be kept amalgamated, must from time to time be cleansed 
from the grey deposit which forms upon them. 

The resistance of this form of cell is extremely low, the voltage is 
very constant (see Figs. 3 and 4), and as it gives off no noxious or 
corrosive fumes, it may be used in any room without any difficulty on 
that acooimt. The cell behaves very much like a secondary battery 
with respect to its discharge voltagfe curve. When it is not being used, 
all chemical action ceases, and in this respect it is far more perfect than 
a secondary battery, for if the cell is kept closed up, it can be left for 
months, and at the end of that time its charge is as large as at the 
beginning. The zinc consumption is from 1*25 to 2 g^rams per ampere 
hour. The consumption of alkali is about 6 grams of commercial caustic 
potaijh, or four grams of commercial caustic soda, per ampere hour, or if 
the chemically pure alkalies are employed, the consumption is only half 
the above weights. If large batteries are employed, and much work 
done with this form of cell, the alkaline solutions, when saturated 
with zinc hydrate, need not be thrown away, as is usually done with 
the smaller batteries, but may be regenerated by means of the addition 
of a suitable quantity of sodium or potassium sulphide, according to 
the equation — 

Naa H2O2 Zn H2O2 + Na2 S =: 2 Na2 H3O2 -f- Zn S. 

Although more expensive, it is rather more convenient to employ 
caustic potash than caustic soda for this battery, for the caustic soda in 
liable to form crusts of sodium carbonate, which creep up over tlic 



10 



PRIMARY AND SEOONDAKY BATTERIES. 



sides of the cell and th(> plat« ; if caustic soda is used, and this incrua- 
tation is observed, it must be removed from time to time. 

The following table is given by Messrs. Umbreit and Matthes of 
Leipzig, the makers of this cell, summarising its chief important points, 
Including output, weight, dimensions and price : — 



Type of evil. 
(Trado numU'r). 



0-85 



Electro-motive force in volts . j 

Terminal potential diflPerence j 
when normal current is taken J 
off I o'78-o'82 , 

Terminal potential difference 
when maximum current is | 

taken off ' o'yo-o'ys 

Normal current output in am- 
peres 

Maximum current output in 
amperes 

Capacity of cell in ampfere 
hours 40-50 

Internal resistance of cell in 
ohms o'o6 

"Water required, in litres i'2 

Caustic soda, weight required 
for one charge in lbs. . . . 044 

Caustic potash, weight re- 
quired for one charge in lbs. . o'66 

Number, and dimensions of the 
copper oxide plates in inches, 
approximate i 4*75X4) 

Length of cell in inches ... 7*5 

Width of cell in inches ... 2*25 

Height of cell in inches ... 7-5 

Weight of cell complete, in lbs. 3*3 

Price in German marks (i 
mark = i shilling, about) . . 



II. 



0-85 



III. 



IV. 



085 0-85 



0-78-0-82 ;o78-o'S2 078-0'82 



o' 70-0* 7 5 

2 

4 
80-100 

003 
23 

0-88 
1*32 

I (6 X 6) 

7-5 
35 
II 

5'82 



o"70-o-75 o"7o-o"75 

4 8 

8 16 

160-200 350-400 

o'ooi5 0*00075 
4*4 7 



i"67 
2-42 



33 
44 



2(6x6) 2(8X8) 
8 i 9 

5 55 

i^ I3'5 

ii"55 19*8 

16 27 



The following are two discharge curves of a No. i '*Cupron" 
element with a nearly constant current, whose mean value = 1*55 
ampc^res. 

The weight of sodium hydrate (conmiercial) was 200 grams. The 
external resistance between the cell tc^rminals zn 0-43 ohms. The 
internal resistance of the cell rr o-o6 ohms. The mean terminal vol- 
tage during discharge =: 0*76 volts. The ampere hour capacity := 53*5. 



The following are the dweharffc ciirve« <ii u No. i "Ciipiroi" 
element with a nearly conHtant current of mean rulue := o'i5 aruptres. 

TlieextfirDBlresi(rt«iice^5'34 ohiOH. The internal resiBtanoe ^ o-o6 
ohms. The mean terminal vo1ta^ zz oSo voltf. The ampere hour 
capacitT := bo. The weig'ht of Hmliiim hydrate employeil vae, of uourxe, 
the aame ax in the laiit case (Fi)r. 3]. 



.. TbuB in hsun 

Fig. 4.— Weftk Current DischarKe Curve. 



19 PRIMART AND SECONDARY BATTERIES. 

]>aiii«ll's (Mil. — This conaists of a rod of amalgamated zine im« 
meraed in either dilute Hulphuric acid (eight of water to one part acid), 
or a dilute nolution of zinc sulphate contained in a pot of unglazed and 
porous porcelain. This pot stands in an onter vesflel of glazed earthen- 
ware containing a saturated solution of copper sulphate, which should 
contain a little free sulphuric acid, and is often provided with a shelf 
partially immersed in the liquid, upon which crystals of copper sulphate 
may he placed, so that the strength of the copper sulphate solution may 
he preserved in spite of the constant removal of copper from it, due to 
the action of the cell. A sheet of metallic copper is bent round the 
porous pot, and stands immersed in the copper sulphate solution. The 
cell terminal screws are attached to the zinc and ox)pper plates respec- 
tively, the zinc being the negative pole. When the c<»ll is not in iwe 
for some time the porous pot should be lifted out. The level of the 
zinc sulphate solution or sulphuric acid solutiou, according 
to which is employed, should be kept an inch or so a>)ovo 
the level of the copper sulphate solution. This cell g^ves 
a remarkably constant e. m. f ., and therefore a very con- 
stant current. It does not polarise. The zinc sulphate 
solution gradually gets stronger, and must from time to 
time be dihited by removing some of the liquid, and filling 
up with water, or dilute sulphuric acid. The copper sul- 
phate solution gets weaker in copper, and its strength 
must be kept up by adding fresh crystals of copper sul- 
phate, either placed on the shelf described above, or by 
Fig. 5. suspending a muslin bag containing crystals immersed in 
Daniell's the solution near the top. A two-pint cell will at the 
Cell. most give a current of not greater than about J ampere 

in practice, even when dilute sulphuric acid is employed 
with Uie zinc. In Fig. 5 is shown a '^iew of a Daniell cell, in which 
the outer glazed earthenware pot, described above, is replaced by a 
solid copper external pot to which i« attached the positive terminal 
of the cell. 

I have been at some pains to find out the particular form of Daniell 
cell which may bo most cheaply and satisfactorily made, in order to 
ascertain how far this form of cell will compare favourably with the 
Cupron element for use in electro -plating, more especially for electro- 
silvering and gilding. Mr. F. Lyne, 8ilver«niith and electro-plater, 
of 5, Perry Road, Bristol, has sliown me a Daniell cell which he uses, 
and in my opinion it i« as cheap and serviceable a form of Daniell as 
can be obtained, and I am indebted to this gentleman for the details as 
to cost, etc., which are here given. The outer vessel or containing pot 
of the cell is made of a glazed earthenware cylindrical vessel, known in 
the pottery trade as a dyer's pot, it has a capm'ity of about four gallons. 




danibll's celEi. 13 

and is about 12 inches high, it costs four shillings. The copper ojlinder 
which stands inside this outer pot is fourteen inches high, and is made 
by bending up a rectang^ar sheet of metallic copper, measuring 14 
inches by 22 inches, into a roughly cyUndrical form. The thickness of 
the copper sheet need only be sufficiently great to permit it to stand 
stiffly after it is bent up. The cost of this copper, -which weighs 
roughly about 3 lbs., is about two shillings and threepence. Inside 
the copper cylinder is placed an unglazed or porous pot, 13 inches high, 
and having a diameter of about 5 inches. These porous pots cost 
twelve shilling^ per dozen. The zinc element which stands inside the 
porous pot consists of a cylindrical rod of zinc about 12 inches long and 
2 inches diameter. It weighs' about 8*5 pounds, and contains 8 pounds 
of zinc and 8 ounces of mercury. The mercury is added to the molten 
zinc just before casting, but this addition should be made when the 
zinc is very nearly cold enough to solidify, otherwise most of the 
mercury is volatilized and lost. The addition should also be made 
under a chimney hood, so that any mercury vapour formed may as 
far as possible be carried off, for it is poisonous. In my opinion the 
mercury can be more easily and safely added to the molten zinc if 
beforehand it is allowed to soak with about a pound of granulated 
zinc, which has been moistened with dilute sulphuric acid (one of add 
to three or four of water), and after this amalgamation has been fairly 
completed, and the acid poured off, and the resulting amalgam thus 
obtained washed and driedy the dried amalgam can be added to the 
remaining melted 7 pounds of zinc, at a moderate temperature, with less 
danger of loss of mercury by volatilization. In any case the mercury 
and zinc alloy obtained is cast into rods of the form above stated. The 
cost of the zinc is about one shilling and twopence, and the mercury 
about one shilling and sixpence. The outer glazed pot contains a 
saturated solution of copper sulphate, to which an addition of about 
2*5 per cent, by volume of sulphuric acid is made, and an equal or 
rather smaller amount of nitric acid. The amount of this copper 
sulphate solution is about 2^ gallons, each gallon contains about 2 
pounds of crystallised copper sulphate, which costs about twopence 
per potmd. The solution in the porous pot consists of dilute sulphuric 
acid, one part of acid to ten parts of water. The total cost of the 
solutions is about one shiUIng and eightpence. The brass terminals, of 
which one is soldered on to the edge of the copper plate, and the other 
has the zinc cast on to it, cost about one shilling. The total cost of 
this cell is therefore about fourteen shillings to make and charge com- 
plete. The resistance of the cell is slightly under 075 ohms. Six of 
these cells in parallel, when short-circuited, g^ve a current of nine 
amperes. The e. nu f . is of course close to I'l volts, and the maximum 
current one cell can give is about i '5 amperes. The total weight of 



t4 FRDUBY AMD SEtXtNDAlty BATTEKIKS. 

thp cell Romplete ih over 50 poimdit. Bjid ita output la lo» than Hut of 
two No. I Cupron clementii, which have in wrieH a voltage of 1 5 volts, 
and give a cnrrent of about i 5 amp^rett, weigh under seven ponnda 
ivmplcte, have an iutemal retuBtanre (the two in 8erie«) of uitder 0*1 
ohma, and fmally take up a Kpuce 75 inches high tmd about 7'5 k 5 
Rquare inches standing room, wh^reau the Daniell cell juat deaciibed 
takes up a space of about 144 square inches standing room, and is over 
13 inchea high, whilst finaUy the Cupron element (yUa oost (iu Ger- 
many) ten ahillingH, a* agunst a coot of aliout fourteen Hhillings for Ote 
Daniel) cell, which has, however, a umidler output. There can there- 
fore be little doubt as to which h the niore advantageous cell to 
employ. 

Bnw Call. — The Smee Cell conaisis of two amolgoniated tino 
ptat«e Birangod on either aido of a thiu sheet of 
platinised silver. The ziuca are roonwted together 
to the negative (enninal of Iho cell, and the 
plutiiiietd silver is coonected to the positive ter- 
minal. There is uo poroun pot. oud the plates, 
which are supported at the top by a piece of 
wood or ebonite, to which they uv attached by 
the terminal hiuding acrewa, are aepurated from 
one auother below by a wooden frame or distance- 
piece, aud the whole uf this arrangement is 
immemed in dilute sulphuric acid (eight parts 
water and one part sulphuric), which is contained 
in an external ghuv, or glazed earthenware pot. 
A form uf the cell is showu in Fig. b. This ceU, 
which has an e. di. f. varjiug from I volt to 0-5 
Fig. 6. volt, ban a low internal rcaistunce, and will, for 

the same rize of positive plalj>, give a larger 
current than tho Daniell, but the current is iioHiiug like so constant. 

Orova's Cell. —This cell coutdBt* of uu exti'mal flat pot of glazed 
eiirthenware iuaidc which is uuuther i-ell of u tumilur Hha[ic, but mode 
of jHiroiui or uuglazcd porcelain. A flat plato of zinc in bent in such 
a fonn that the porous cell may be placed within its folds, by means of 
which ammgemeut a surface of ?inc is eiposed to each side of the 
inner cell. A plate of plutdniun foil is inserted in tlie porous pot, and 
is of sufficient length to be attached to the projecting end of the zinc 
plate of the neit cell (when arranged in a batteryl, or to a jiiece of 
ebonite or piteh-ooated wood when used singly, by means of a laud- 
ing screw or clamp. The inner gioroaa pot, uontaiuiuK the platinum 
element, is filled with strongest nitric acid, aud the uultr, iu which the 
zinc ill [Jaced, is filled with dilute 6ulj>hnric acid ("lie purl sulphuric 
acid, to eight yaxlu wkt«rj. In ]<'ig. ;, ou the right, is snuu-u u cell in 



BtTNBEHB OKLL. I5 

wbioh A a ia th« bent zinc plate, C C ore th« platinum pUt«B of Q\» 
cell and the next one to it, and £ is tbe poroiiH pot. On thp left of 
Rg. 7 IB shown a batteiy of four of the oelU contained in one common 
external glazed earthenware cell D, tbe alternate zinca and 
j^tinmna being oonneoted \>y braiw clamps. Tbie cell hiw a high 
e. m. f. of abont \-<j volte; it, however, gradually falls when a current 
ia generated, owing chiefly to the weakening of the nitric acid in the 
porous pot, doe to tbe chemical action taking place. The cell ban a 
low reustance, and will give a larger current per square inch of jiositive 



Fig. 7.— Grove's Cell. 

plate thsA eillieT the Daniell or the Smee. The objectiona to tliie cell 
are chiefly that it is ezpenBive, it gives oS corrosive and unpleasant 
fumes, and the nitric acid if apilt is liable to do much damage to any 
Bubstance on which it falla. 

Bnnvan'a 0*11. — Thia cell is precisely HJiuilar in its oonstitueuts 
to the Oroye cell, eicept that the platiuiim ia replaced by gas retort 
carbon, which therefore makes it a much cheaper form of cell. Mr. 
Watt, in his original edition of the preM^ct work, praincH it b8 being 
"one a( the moat useful batteries for tlie practical purposes of the 



1 6 PBIUABT AMD SECONDARY BATTBBIES. 

electro -metaJlurgiHt." One form of thu batttry is shown in Fig'. 8. 
Id thiB partirular cell the outer vessel in h cyliudrical stoneware jai 
capable of boldiug about 4 galkniB (but, of couree, amaller celU ore 
madej. A plute of stout sheet zinc U turned up in the form of a 
cylinder -i, and this is well amalganiated with mercury. A suitable 
binding' screw is attached to this cylinder to receive the conducting 
wire. A porous cell about 3 j inches in diameter ia placed within tlie 
zinc, and in thin a block of gaa retort carbon ia stood, and is f umialud 



Fig. 8.— Buiisen'sCell. 

with a suitable clamp B for attaching a eotidm-ling wire. The porona 
cell is then nearly filled with strong nitric arid, and the outer vessel is 
filled to the same height with dilute sulphuric acid— about I part of 
arid to 8 parts of water. This lattery, like the Grove, emits noxious 
fumes, and mu«t bo kept either in a well -ventilated cupboard or 
outside the windows if there are any substances, such as metals, ete., 
which thew fumes mi^ht damage iu the room in which the current is 
being employed. The reason that a n'lindrical porous pot ia employed 
in this battery inntcad of the flat form used in (lie Qrove, is owing to 



BICHBOHATS CELL. If 

the fact that though platiuum U cheapest in a, fhin plate carbon is 
most eipenBiTe aod is much more rcadil; obtaiued in the form of a 
rectangulBT rod. Theoarbou rods are cut fiom retort rorbou, and (his 
ia sometimes rendered still more dense bj immeniiDg in sugar solution 
lUid then heating to a high temperature repeatedly . 
The original form of the battery aud its dinnected parto are «hown 



«( 



J 



f'K 9 — BunBBn's Cell. 



in Fig. 9. The carbon block in the Bunnen cell is more or leas 
porous, and absorbs the nitric acid in which it in immersed by capillary 
attraction, io the same manner that a lamp of sugar hucIch up tea or 
other liquid into which one end ia dipped. This acid will act on the 
braaa clomp shown at B. Fig. S, but to prevent this the outer end of 
the carbon may be made hot and then dipped 
into hot parafiin wax ; this will block the pores at 
the top, but, as the electricity travels along the 
BoUd carbon and not throngh the pores, if the 
outside of the block is scraped free from paraffin 
the clamp can be screwed on and good metallic 
connection obtained. This cell slowly drops it« 
e. m. f. like the Orove, and due to a similar 

BlctaromaM C«U. — The bichromate cell, 
I^. 10, is nsually met with as a mnglo fluid 
cell, and conusts of two plattfl of gas retort 
carbon forming- together the positive element, and 
placed between them, but not touching them, ia a 
single plate of zinc, which is the negative element _ „i'^; '°' . 
..I 1. ™n ... <■ -> . > > ,- Bottle form of 

of the cell. The eiciting- fluid is made by making Bicbromata 

a saturated solution of potassium bichromate and Batterv 

adding to 10 parts by volume of the solution, 
about I volume of strongest sulphuric acid. The acid must be 
added gradually, and wiUi constant stimog, or the heat set at 



1 8 PRIUABT AND SKGONDART BATTERIBB. 

liberty may craok tho pflam vessel in which the mixture must be 
made. Tlie zinc plate is attafhod to a brass rod, which is held in 
position by a thumb-screw. When the battery itt not in use this 
screw muBt be slackened and the zinc raised out of the liquid by 
means of the rod, and must be held in this raised position by again 
tightening up the thumb- screw. When the battery is being used the 
zinc must be lowered and the thumb'tcrew again tightened. The 
neglect of this precaution is not infrequently a cause of considerable 
trouble, as the battery will then give no current. The bichromate 
battery has a high e. m. f ., which is fairly constant, but in time falls, 
owing to the chemical alteration of the exciting fluid. The exciting 
fluid is, when fresh, of a dark orange colour, but becomes after it has 
been used of a darker and darker brown, and then g^reenish brown 
colour, and finally quite dark green; before this complete change 
takes place, however, the e. m. f . of the cell will have fallen con- 
siderably, and the solution should be renewed. As the solution is 
altered it deposits hard dark-coloured crystals of potassium chrome 
alum, which must be removed from time to time. The chemical action 
in the battery goes on whether it is being used or not, if the zinc is 
immersed in the solution, and it is on this account that the zinc plate 
is so made that it can be rcadUy withdrawn directly the cell is out of 
use. The resistance of a bichromate cell is low, and it will give 
about as large a current as a Bunsen cell for the same area of the 
positive element immersed in the exciting fluid. A double fluid 
bichromate battery is also made, in this the carbon plate is placed alone 
in the bichromate solution and the zinc element, which must now be 
amalgamated, is placed in a separate porous pot with dilute sulphuric 
acid (one volume of concentrated acid to ten of water). In this form 
of the cell the zinc need not be withdrawn when the cell is not in 
use, but if it is to remain out of use for some time it is better, as in 
tho Daniell cell, to remove the porous pot and its contents until the 
cell is again required. One marked advantage of the bicliromate 
cell over other cells having high e. m. f . is due to the fact that it does 
not give off corrosive fumes. 

The :Leelanelie OelL— This battery consists of a positive carbon 
element surrounded by some paste or conglomerate of manganese dioxide 
and carbon. The carbon plate and its surrounding carbon and man- 
ganese composition stands in a solution of ammonium chloride, which is 
kept nearly saturated. The solution flows freely through the porous 
pot into contact with the carbon plate and its surrounding manganese 
dioxide, the cell being a single fluid cell. The negative element of the 
cell iu a zinc rod. This cell gives off no objectionable fumes, and has 
a maximum e. m. f . of i '43 volts about, but after use for a short time 
it polarises, and its voltage falls considerably ; if allowed to remain 



VAVAGEMENT OF PBIMABY BATTBBIES. 1 9 

idle, however, for a Rhort time, it quite recovers its original o. m. f . 
The exciting liquid is but slightly poisonous, due to the zinc which 
dissolves in it, and it is non-corrosive ; it is not, however, very suitable 
for any electro-plating work. All the many forms of what are known 
as dry cells are variations on the Ledanche cell, in which the ammo- 
nium chloride solution is made into a thick paste with some inert 
powder, such as plaster of Paris, mixed with some calcium chloride. 

ilinalgamatton of Sine Flatos. — If a plate of ordinary commercial 
metallic zinc, containing perhaps 2 per cent. orjM) of impurities, is placed 
in dilute sulphuric add, it immediately commences to dissolve, large 
quantities of hydrogen gas being given off at its surface, and zinc 
sulphate is formed which dissolves in the liquid. This chemical action 
is due to what is called loaU aetum^ caused by the presence of the im- 
parities in the zinc, for if these are removed, and quite pure zinc, - 
obtained by distillation, is used instead of the impure commercial zinc 
no such chemical action occurs, or at any rate it is extremely slow. 
Perfectiy pure zinc may be employed as one of the elements of any 
electric battery, and the battery will act perfectly, but when not in use 
the corrosion of the zinc will cease. The cost of this pure zinc is, how- 
ever, very high, and it has been found that if the surface of impure 
commercial zinc is coated with a sheet of mercury, or rather an amalgam 
of zinc and mercury, the e. m. f . of the battery is not affected, and 
the battery acts as satisfactorily as before, but the local action is com- 
pletely stopped, and when the battery is not being employed to give 
current the zinc does not dissolve. The coating of the zinc plates 
with mercury, or amalg^amation as it is termed, is perf oimed by rubbing 
the plate with a rag tied on to the end of a stick in a little dilute sulphuric 
acid (one of add to ten of water), which may conveniently be placed in 
a deep saucer, and at the bottom of the saucer, under the add, must be 
placed a little mercury, which must be pushed up over the add-cleaned 
zinc plate : the mercury will be found to wet the zinc, and leave it 
with a bright silvered surface of zinc mercury amalg^am. Only the 
smallest amount of mercury possible to thus completely silver over the 
plate must be employed, as an excess of mercury merely causes the 
plate to become rotten. When in use, if blackish spots appear on the 
zinc plate it must be again further amalgamated. The mercnry 
employed for amalgamating must be kept by itself in a separate jar or 
bottle, as it contains dissolved zinc, and must be on no account mixed 
with mercury it is desired to keep pure. Dirty or blackish zinc plates 
are conveniently scrubbed with a flat piece of pumice before amal- 
gamating. 

IKaiiASOTiMiit of Vtlmarsr Batt«ri«s. — ^The screws and connections 
must be kept scrupulously clean, and the zinc plates must always be 
properly amalgamated. The solutions in the battery must be renewed 



20 PBTMAB7 Ain> 9K00NDART BATTER1V8. 

from time to time, as they are seen "by inspection to be becoming nm 
down, or if the cell does not act snflBciently energetically. Another 
frequent canno of a battery's failnre to act is the contact, however 
slight, of one of the elements with the other inside or outside iho 
liquid, an accident which is known as a short circuit. A loose or 
corroded attachment between the battery terminals and the active 
elements, or a loosely screwed up wire in the terminal may also rause 
the battery to cease to work entirely. In Bunsen batteries the upper 
ends of the carbons and ihe brass clamps should be coated with varnish 
after they have been screwed up, in order to avoid action on the brass 
by the nitric acid. 

The copper plates of the Wollaston and the nlver plate of the Smce 
batteries must be kept clean, and if accidentally spotted with mercury 
from contact with the amalgamated zinc plates, the sheet of metal 
should be heated in a flame to expel the mercury, and then should 
be pickled in dilute sulphuric acid, and scoured after rinsing. Tho 
zinc elements in Daniell cells should not be permitted to touch tho 
porous cells at the bottom, or a deposit of copper may take place both 
inside and outside the cell and render it useless. Porous cells often 
crack from this cause. When porous cells have been used, and are laid 
aside until again required for use, they should first be well rinsed in 
rain or distilled water, and then filled with distilled water. They 
should never be allowed to become dry, or otherwise any sulphate of zinc 
or copper remaining in their pores wiU crystallise, and probably in so 
doing crack the pot in many places. If when a porous pot is removed 
from a Daniell ceU, in which the acid is weak or is entirely replaced 
by zinc sulphate, it is rinsed out and stood in hard water, that is water 
containing calcium carbonate, a green dex)08it, or precipitate of cuprio, 
and lime carbonates will be formed in the pores of the pot, and this 
deposit will, in the course of lime, very greatly increase the resistance 
of the cell. If distilled water or very soft water is used this trouble 
will not occur, but if hard wat^ is the only available variety, it should 
be slightly acidified with sulphuric acid before it is poured into the 
cell, and the cell and contents stood in a sink, then the slow oozing of 
the acid water through the cell's pores will remove the copper and ano 
salts without precipitating them. If a cell whose resistance has been 
raised by the deposit of the basic carbonates, as described above, is 
washed or soaked in dilute sulphuric acid, it is often found that the 
cell becomes cracked all over and perfectly useless, caused by l^e 
chemical action which is set up in its pores. 

Belative Activity of Primary Batteries. — The following experi- 
ments roughly indicate the relative activity of different kinds of 
primary batteries. The zinc plates were the same in each battery, and 
in each battery the positive plates had double tho area of the zinc 



filNDlNO SCllEWS. 



21 



plateB, and there was in each case the same distance between the 
positive and negative plates. The currents obtained for each battery 
BO arranged were passed through solutions of copper sulphate of the 
same strength, with the electrodes of copper of the same tdzc and equal 
distances, each during the period of one hour. The following results 
were obtained : — 



Grove battery . 
Daniell battery . 
Smee battery . 
Wollaston battery 



104 grains of copper deposited. 



33 

22 

18 



11 



II 



OonataiMy of Battertos. — The activity of most batteriet gradually 
alters if they are left unadjusted, so that one kind of battery may be 
useful for a short period, and another kind if the action is to be sus- 
tained for any length of time. This is illustrated by the following 
table, showing the weight of copper deposited, the conditions being 
the same as in the last experiment : — 





One 


Two 


Three 


Four 


Five 


Six 




hour. 


hours. 


hoars. 


hours. 


hours. 


hours. 


Grove battery 


104 


86 


66 


60 


54 


49 


Siagle-cell 


62 


57 


54 


46 


39 


29 


Daniell . . 


33 


35 


34 


32 


32 


30 


Smee . . . 


22 


16 


14 


ZI 


12 


II 


Wollaston 


x8 


14 


J5 


12 


IX 


10 



45 
24 
31 
10 
10 



464 RTS 

311 
227 

96 
90 



II 



II 



II 



In a second experiment of a similar nature, larger plates were used in 
the batteries, and proportionately larger electrodes in the copper sul- 
phate solution, and each battery was kept in action until one pound of 
copper was deposited, the acid being renewed and the zincs brushed 
every twenty-four hours. The time taken to effect this is shown in 
the following table : — 



Grove battery . 


19} hours. 


Smee battery 


. 147 hours. 


Single-cell 


• 45 M 


Wollaston 


• 151 „ 


Daniell 


• 49 II 







I. — These useful and necessary appliances are 
usually made from cast brass, and may be obtained in a great variety 
of forms. A few examples are shown in the accompanying engrav- 
ings. Fig. 1 1 is used for connecting the platinised silver of a Smeo 
battery to the wooden cross-bar, or for casting in zinc bars for Daniell'ii 
battery; Fig. 12 is used as a connection for a zinc or flat carbon 
plate ; Fig. 13 is a binding screw for zinc plates, or for the cylinders 



22 



PRIMARY AND SECONDARY BATTERIES. 



of a Bunsen battery ; Fig. 14 is for uniting the poles of dynamos with 
leading rods: Figs. 15 and 17, are for connecting flat copper bandB to 







Fig. II. 



Fig. 12. 



Fig. 13. 



Fig. 14. 



zinc and platintiin plates, ae in Grove's battery: Fig. 16 is a clamp 
for large carbon blocks, for uniting the zincs of a Smee, or the copper 
plates of a WoUaston battery. 






Fig. 15. 



Fig. 16. 



Fig. 17. 



General lUmarka on Primary Battoriea. — With the exception of 
the '*Cupron element," primary batteries require much more care 
and attention to keep in proper working condition than any other form 
of generator. Their reeistance is as a rule large, and varies with their 
output, and, as lias just been shown, their activity diminuhcs very 
seriously with the time they are left iu circuit. The ordinary forms of 
primary batteries are therefore ou all grouudts, iucluding cost, Uie least 
advantageous form of source of e. m. f ., and sliould if possible never 
be employed for electro -technical work ; and, imless already possessed 
by the experimenter, the writer strongly advises him not to purchase 
them, but either to invest in some form of the Lalande or *^ Cupron 
element," cell, or in a dynamo or secondary battery, according to the 
circumstances of the work it is desired to undertake, a discussion of 
which considerations will be found at the end of the next chapter. 

Secondary Batteries. — Secondary batteries, which are made in a 
large number of diifercnt forms, always consist (at least in all forms 
used commercially up to the present) of a negative element of metallio 



8E00NDABY BATTSBIS8. 9$ 

• 

lead and a posLtiTe element of lead peroxide, sapported on lome f onn of 
lead frame- work. There is always one more negatiye plate than the 
nmnber of positive plates present in a cell. The exciting flnid is a 
solntion of snlphnric acid in water, having a specific gravity which 
varies from 1*170 when the cell is discharged, np to I'2I5 when it is 
folly charged. 

llie voltage of a secondary hattery, when fully charged, should he 
2*2 volts, measured whilst the cell is giving a discharge current of 
about half its normal charging current, and the cell may be used 
without re-charging until its voltage drops to not lower than I '8 volts, 
measured whilst the cell is giving a disc^harge eun.'ent of about half its 
normal charg^g current. 

The voltage of a secondary battery is for all practical purposes very 
constant, and during the greater part of its discharge is very dose to 
2 volts. The resistance of a secondary cell is very much lower than that 
of any other form of cell of equal current output. The current output 
of any cell is always stated by the maker, but in each case the actual 
current output at which the cell is run must depend upon the number of 
hours during which it is required to be used ; for instance, a single plate 
'* Chloride " secondary battery, manufactured by the Chloride Electrical 
Storage Syndicate of Clifton Junction, Manchester, which costs well 
under twenty shillings complete, may be discharged for one hour at 
the rate of 30 amperes, but if it is wished to run it for three hours only 
15 amperes must be taken from it, whilst for a six hours discharge, the 
rate may only be 9 amperes, and if discharged at a imif orm rate for 
nine hours, the current taken out must not be greater than 6} amperes. 
The normal charging current for this cell is stated to be 8 amperes, and 
the wmxiinnTn charging current must not be greater than 15 amperes. 
A six-plate cell of this type is shown in Fig. 18, and Figs. 19 and 20 
give views of the negative and positive plates respectively ; Fig. 2 1 
gives a view of three of the Electric Power Storage Company' h 
secondary cells arranged in series on a Htuud. This particular size 
contains five positive plates. When the voltage of a secondary 
battery cell has fallen to 1*8 volts, as measured by a voltmeter 
whilst the cell is discharging at the rate of about one half its 
normal charging current (that is to say, in the chloride cell wo have 
been considering above, whilst the cell is discharging at the rate of 
about 4 amperes), the cell must not be used any more until after 
re-charge, otherwise it will be more or less permanentiy damaged. 
The cell can be re-charg^, however, and when its voltage has risen to 
about 2*2 (as measured with the discharge current stated above), it is 
completely re-charged, and can be used again and again imder these 
conditions, with alternating charge and discharge, for a very long perioil 
if proper care is taken of it. The chief necessary precautious which 



PftlMjlRY ANb SECONDABT UATTBRtES. 



must bo taken in order to keep u Kcondary oAl in good condition axe 
SB foIlowK :— 

I. Never leave the coll for onf tang period in the duchorged, <a onlj' 



SECOHDARV BATTEBlEa. 25 

partinUy charged oondition. That 19 if it becomes ncccmaiy to Isave U 
without diacharging it for, its.j, a, week, sec tbut it ie charged Dp folly 
to begin Tith, and diaconnect all Icodit from it in order that any leak- 
age may be as much aa poiwible reduced. 

2. Never diacharga below the voltage limit of i'8, meainiredas eped- 
Bed above. 



Fig. 19.— Single Negative Flatti ut Chloride Secondary Cell. 

3. Kever allow the acid in the cell to evaporate below the top edgee 
of the battery plates. The acid in a cell always teudx to decrease, due 
partly to evaporatdon, and partly to what iscalled spraying. Spraying 
is the name given to the ^pray curTied off by the hydrogfen and oxygen 
gascH liberated in the hquid when the cell is charged, and is eHpeciall; 
noticcabli! tuwurds tho end of the churgo. In order to replace euch 
loBt acid, the cell must from time to time be flUed up with either dis- 
tilled water or rain water, until the level of the liquid is about one to 



36 PBIUASY AND SEGOHDARr BATTEBI1C9. 

one and a-half inches above ihe top of tbe edges of the plates. As water 
has a leso demdty thaa the acid liquid in the uelia, the added water will 
tend to Temaiu as a layer at the top of tbe oell, floating upon the 
underlying denser acid. This weak acid at the top tends to damage 
the tope of the plates, and it is therefore u good practice to mix the 
liquid in the cell, aifer adding the water, by blowing through a glass 
tube, pushed duwn to the bottom of the cell, and having a piece of india- 
rubber tubing attached to it for a mouth-pieue. 



Fig. 20.— Single Pofiilive Plate of Chloridt Secondary Cell. 

It isi perhapH hardly iiecexHory to caution the rriuler aguinirt getting 
the acid into the mouth : the result will be diMigreeable in Uie Mgheat 
degree. As the spraj-ing of the acid liquid removes not only water 
but acid, and a» the directions above given for the making up the loss 
only involve the udditjon of water, it is clear that the acid liquid in 
the cell muHt trradually become weaker : this w-cukcning oertaiDly does 
occur, but only slowly, iind when it becomes detcctablo sufiicicnt frceh 



SEOONDAKY BAITEUIKB. 2J 

Butd mnst be added to make good the loea. To do this it is kdiluible 
to ]ieep a mi^ititre of about 3 pnrts hj volume of aulphnriu acid 
{». g. ^ I 85) with 5 parta by volume of distilled water or rain watpr. 



Thin mixture hoe »■ specific: gravity of about I-2S, and Hh(D the 
gravity of tlie iicid in the Minndory cell i" fmiuii ininiediiiU Ij attor a 
full charge to be ua low lu ilij, the otluugcr uuil wlutiuu uiunt be 



28 PBIUAR7 AND SECONDARY BATTEBIBa. 



added ^rraduBUy, a. little at a time, uDtit the strength of the acid m 
the cell rises t« I 1 1 once more. 

4. Never remove the negative, or lead {that is the grey-look ingj 
p1at«e, from their acid mlution, or, at any rate, do not let this be done 
for more than a very diort period when it becomes necesaarj, aa is 
Boiiu!tiuit.-9 the cane, to straighten plates dSLtnaged by accidental short 
circuit or other cause. 

5. The positive or reddiah-choooUte coloured platea, mayberemoTed 
from the acid safely when necessary, but should not be left out longer 
than can be helped. No attempt, however, must be made under any 

i, unless the cell has already been accidentally completely 



Fig. 21.— K. P. S. Portable Q Type Secondary Battery. (Id the particular 
battery shown here four separate cellsare connected ia seiies, each 
separate cell hftving three positive pUtes.) 

Bhort circuiled, to remove either the positive or negative plates from a 
cell whiltit it contuns acid, otherwise a serione short circuit will aJmoHt 
certaiuly occiu-. The best mithod of taking to pieces and overhauling 
a cell will be mentioucd later on. 

6. Be very [^aref ul to see that uu leakage occoth ontade the cell from 
the punitive to the negative terminal, a conunoii but often unnoticed 
cause of leakage L" the acid noaked wooden cover of tlie portable or 
enclosed form of t<ccondary battery. A partly diiwectcd Wow of a 
portable E. P. S. secondary cell is shown in Fig. 12. Do not have a 
metallic liandlc on the lid of nihIi n coll, or if it is plaoed on the cell by 
the uakcT:', iu-\l tliciu to remove it and place metallic handles, one on 



6E0ONDARY BATTERIES. 2Q 

each of the eddes of the cell, and have a sufficiently strong* leather sling- 
handle soaked in paraffin wax attached to these. Thin slin^-handle 
mnst be large enough to }>ermit of its being readily pushed on one side 
to allow the cover of the cell to be removed when desired. 

7. Be very careful that in charging a cell you connect the positive 
pole of the cell to the positive pole of the charge apparatus, and 
Uie negative to the negative. The polarity of the terminals can 
readily be found by inspection, for the positive terminal is attached to 
the lead peroxide plate, which has always a more or less marked dark 
chocolate colour, whilst the negative is of a darker or lighter cool grey 
colour. In cells which are fitted with covers, however, the error of 
mistaking the polarity is rather easily made if care is not taken when 
the lid is replaced after inspection or adjustment, for the lid of these 
o Us has the polarity marked upon it, and it is sometimes not marked on 
the emergent lugs of the plates ; consequently if the lid is placed on in 
reverse position the poles, as judged by inspection, are apparently 
the reverse of what they really are ; this difficulty can be got over by 
never allowing anyone but a reliable and responsible person to remove 
the cover of the cell. 

8. Do not short circuit the cell, that is do not place a very small or 
zero resistance between its poles ; the cell will under these circumstances 
g^ve a very large current and will thereby have its useful life much 
shortened. Some people make a practice of what is called sx)arking 
a cell, that is, rapidly drawing a wire attached to one terminal over 
the other terminal of the cell in order to see if a spark is given. This 
spark is taken to indicate by its brightness the more or less complete 
charge of the cell. The proper test to use to ascertain this, is a small 
oell-testing voltyieter. Such an instrument costs only about thirty 
shillings, it need not read to higher than about 3 volts, and should 
read with an accuracy of not less than 0*2 volts per division. A good 
pocket instrumeijb of this kind (Fig. 23) is put on the market by 
O. Berend & Co., Dunedin House, Basinghall Avenue, London, E.G., 
and good forms are made by many other manufacturers of elective al 
instruments. 

If by any accident any material of any kind falls in between the 
plates, if it is made of a conducting substance, it will probably produce 
a short circuit, and the cell must be taken to pieces to remove it. If, 
however, it is not of a conducting material and it is desired to remove 
it, a rod of wood, glass, or other non-conducting material must be 
employed to fii^ it out. A rod of conducting material must on no 
account be introduced between the plates of a charged cell for any 
purpose whatever. 

9. To keep cells in good condition it is very advisable to rule out a book 
in columns, two columns to each cell, one for the volts 3nd the other 



30 PRIMARY AND SECONDARY 

(or thp Hjipoific gravity, and record the voltage ot esi>li eell (ineamired 
witli the prccautiuuK already Htated) and the Rprcific gravity of itH 
BolutioQ about twi™ a week. Sueh a record iK most lutf-ful for reference 
aod xhnn'N at a pflance the eonditionn of the eellit. The apeciflc gravity 
or tlie iiolutiou Khould 1a> taken by means of a hydrometer {Fig. 24) 
such an in nold hy moKt i«]1 inflniifarluror>> at a price of about two or 
three shilliu>rN iiu;h. In many small seeondary battdieo it i« iropoadble 



Fig. 23.— Portable " Pocket Form " of Cell- Testing VoHmeter. 

to use a hydrometer directly in the liquid of the cell, as there is no 
room for it ; under these cireuiastanceii a nufficient quantity of the 
liquid should be carefully withdrawn from the cell by means of a 
pij*tle ajid traDBteired to a cylindrical tube of Bufficicnt length and 
width to pcnnit the hydrometer to float. 

10. Great care should be taken to prevent any copper or braee 
material (an, fur inBtiince, aalts and oxides from oorroded connecting 
screws) from fulling into the ballery acid, aa the presence ot Balls of 



BUCKLISO OF CELI. PUTES, 31 

Popper and, indeed, moirt other sii>»taiice<i, have a vpry prFJudinal 
effect upon the battery action, und ilU pcnwible noarces of i*oiitaniJnatioD 
nhould bo ax far aa puwiblo aroided. 

II. All conneetionH tn the battery — in, for inntancr, 
bmwi bolts, nuts, waabers, etc.- — must be kept carefully 
clean, and when in uac mast be tightly screwed up. 
Do not clean up the metal parte whilst they are in pota- 
tion over the acid, for it may thereby be contunuaated. 

If the secondary battery is necessarily to be carried 
about B8, for instance, when it has to be charged up on 
other premises, it is adviuable to purchase a portable 
form of battery, but if the battery can be charged 
whilid; in a Sx<d position it is better not to purchase a 
portable form of cell. Quite apart from the fact that 
portable celln are liable to damage somewhat with car- 
riage, the non-portable type gives a better cell, for 
there is better insulation and therefure Ims liability of 
leakage, which is itwlf a very fruitful source of de- 
terioration in a cell. 

BnckUns of 0«11 PlatM. — If a wcondary cell is 
badly short circuited, or if discharges are taken from it 
which are above itn proper capacity, the plaCex arc liable 
to buckle or liend, and the paste or plugs of peroxide of 
lead may fall out, and either or both of these accidents 
may completely short circuit a cell internally. This 
will become evident by the fact that the voltage of the 
cell reads zero on the voltmeter and the cell will give no 
cnirent, nor can it be charged up so us to yield a current. 
Under these drcumstanccs it is absolutely necessary to 
take the cell to pieces and bend the plati'S straight once 
more, or remove the plug of lead pcroiide which is 
CHunng the short circuit. This operation may be per- 
formed as follows : first pull out gently the ebonite, 
glass or celluloid insulators or combe, which will be 
found to be separating the positive plates of the cell 
from the negative ; when these separators are all removed 
lift out the whole of the positive plates and carefully „. 
str^hlen them by gentle bending where necessary. Cell- 
Thifl bending mnst be very carefully performed, and is Xestinff 
best effected by (Jacing a wooden bowd of suitable thick- Hydrometer 
nees between each two poative plates, and gently press- 
ing the whole pile until all the plates are bent flat ami parallel to one 
another. The negative plates are not often found to be buckleJ, but 
if by any chance they are bent they must be lifted out of the acid and 



32 PRTMART AND SECOND ART BATTERIES. 

Btraijfhteiipd in the same maimer as the positives; this operation 
mnst be performed without undue force, but as rapidly as possible, 
for the exposure to the air dumag-cs the negatives, and the straightened 
plates must be returned into the dilute acid as promptly as possible. 
The rapidity and violence of the chemical action of the air upon the 
moist negative plates is shown by the fact that, a iter a very short 
exposure to the air, they will become hot and the dilute acid on 
their surfaces will rise in clouds of steam. When the plates have been 
straightened as de8cril)ed above, they are returned to the acid from 
which, however, any plugs of paste or sediment of lead peroxide should 
be previously removed. The plates sometimes rest upon glass, 
celluloid, ebonite, or even wooden racks at the bottom of the cell, and 
care must be taken that these are in their proper position when the 
plates are replaced. The insulators should next be re-inserted 
between the positive and negative plates, the level of the acid made up 
if necessary with dilute I '21 e. g. acid, and the cell is ready for re- 
charging. It should be charged for a considerable period with a 
current which should be about that of the minimum charging current 
spofdfied by the makers of the cell. This charge may with advantage 
last 30 hours, but usually this i» inconvenient, but it should in any 
case be made as long as possible. Charging and discharging alter- 
nately at low rates of current output over long periods of time, and 
taking care never to discharge below i '8 volts, is a method of treat- 
ment whioh tends to get the plates of a repaired short circuited cell 
into good condition. 

Tr«atiii«iit of 0«lls in Bad Condition. — If a cell is found, when 
charged in series with others of the same size and make, not to effer- 
vesce 80 copiously when the charge is being completed, and if this 
cell drops its volts on discharge after it has been in use for a short 
time, whilst similar cells working at the same output keep their voltage 
for a longer period, it is clear that the cell in question is getting in an 
unsatisfaotory condition. It is said to have a small ampdre hour 
capacity. In order to restore it to condition it is advisable to charge 
it up with the other cells, but not to discharge it or, at any rate, to 
only slightly discharge it : this treatment continued over some half-a- 
dozen charge will usually do much to get the cell back into condition 
once more. 

If the electrolyte of the cell gets into bad condition by reason of 
copper salts or other contamination finding its way into the liquid it 
may become necessary to change the liquid ; this may be done by 
syphoning it out and having at hand some previously prepared cold 
dilute acid of the correct gravity, which can be rapidly added in order 
that the negative plates may remain uncovered for as short a period as 
poi^ible. 



ELVOTBOLYTBB. 33 

If by any chance the electrolyte of the cell is spilt the loss mnst be 
made np, not by the addition of distilled water or rain water, as when 
evaporation is to be made good, but a siifficient quantity of cold dilute 
sulphuric acid of i* 19 to 1*21 s. g. must be added. 

Correet Add 8tr«ngtli for Secondary Batteries. — The proper 
strength of the dilute sulphuric acid to be employed for secondary 
batteries is usually stated by the maker of the cell, but it is always 
closely in the neighbourhood of i-2i, measured at the ordinary air 
temperature. This strength of arid may bo made by gradually pour- 
ing two parts by volume of strong sulphuric acid (1*85 s. g.) into five 
parts by volume of distilled or rain wat^iT. Heat is liberated, and the 
acid must be added in a thin stream to the water, which is kept well 
stirred by a glass rod or a wooden stick. The mixture is best made 
in a glass vessel, but care must be taken that the acid is gradttally 
added, otherwise the rise of temperature will crack the glass ; after 
this mixture has been made it must bo allowed to cool, its specific 
gravity carefully measured and adjasted by the addition of more 
water or more acid acoording as the gravity is above or below the 
desired value of 1 '2 1 . 

Annnal Cost of floeondary Batteries. — If a secondary battery is 
properly attended to, it may be taken that the annual cliarge for 
interest, depreciation, and repairs is not less than twenty per cent., 
reckoned on the prime cost of the battery, but this charge may be con- 
siderably increased if proper care is not taken to superintend the cells. 
A portable battery has usually a higher rate of depreciation than a 
fixed battery. Makers will under certam conditions, which are, how- 
ever, somewhat strict, enter into msdntenance guarantees with pur- 
chasers of their battery. The Cliloride Company, for a fixed battery, 
will enter into such a contract for five years for an annual payment of 
1 2 '3 per cent, of the value of the battery, but for longer periods tliis 
firm requires a larger annual payment, and if we allow interest charge 
at 5 per cent, the total charge will not be appreciably less than 20 per 
cent. 

Blsetrolytes. — ^Liquids may, in so far as their electric behaviour is 
concerned, be divided into two main classes, namely : liquids which will 
allow the electric current to pass through them, and liquids which 
will not allow the current to pass through them. The second of these 
classes, namely, those which will not permit the electric current to flow 
through them, arc of course insulating liquids, such as, for instance, 
paraffin oil, turpentine, rosin oil, and generally imvaj organic com- 
pounds known as hydro-carbons and fatty acids : with this class we 
have practically nothing to do in electrolytic refineries, although it is 
true that insulators for stiitionary secondary batteries, and insulators 
for the support of electric conductors, are frequently filled with some 

D 



34 PBIMABY AND 8BOONDABT BATTBMISB. 

such liquid non-conduotor. The firai clam of liquids, namely, those 
which permit a currezit of electricity to flow through them, may be 
again divided into two other sub-classes : first, liquids which will permit 
an electric current to flow through them, but which suffer no altera- 
tion of composition or chemical change due to the passage of the cur- 
rent. Such liquids are usually molten m(>tal8 or molten alloys, such as 
mercury, or molten iron, brass, Bolder, etc. The second sub-class con- 
sists, howeyer, of liquids which allow the current to flow through 
them, but at the same time the current cauRes a chemical alteration or 
decomposition of the liquid. Such liquids are called electrolytes, and 
usually consist of an aqueous solution of a salt, an acid, or a base, or 
consist of a molten salt, acid, or base. Examples of these electrolytes 
are : — a solution of copper sulphate or of common salt in water ; a solu- 
tion of sulphuric acid or hydrochloric acid in water ; a solution of caustic 
soda or potash in water ; liquid fused zinc or sodium chlorides ; fused 
phosphoric acid, or fused sodium or potassium hydrates. The essential 
difference, which theory and many experiments show exists between 
liquids which are electrolytes and liquids which are not electrolytes, is 
that in the non -electrolyte solution the molecules of matter of which 
the substance dissolved in the liquid Lb made up are all of the same 
nature and chemical composition, whilst in an electrolyte the 
solution consists of a mixture of two or more different kinds of 
molecules. Thus, although common salt or sodium chloride in its 
solid state is probably built up of only one kind of molecule or minute 
unit, each of whichmoleculesoonsistsof thesame combination of sodium 
with chlorine, yet if sodium chloride is fused wo have a solution of sodium 
molecules and of chlorine molecules in a solvent of sodium chloride, whilst 
if common salt is dissolved in water, wo arc dealing with a solution of 
sodium molecules, and chlorine molecules, and sodium chloride molecules 
in water. Thisisthecase with all electrolytes, and the electric current, or at 
any rate the electric di ff erence of pressure at the two electrodes or conduct- 
ing terminals from the current generator, which are immersed in the 
liquid, simply act by attracting these different molecules, into which the 
original compound has split up, into different directions. The electrode 
attached to the negative pole of the generator always attracts the 
metallic element's molecules in an electrolyte, and these molecules are 
sometimes known as the eathions, the electrode which attracts them is 
called the cathode. The electrode attached to the positive pole of the 
generator attracts the non-metallic element's molecules from the elec- 
trolyte ; these molecules are sometimes called the anions, and the 
electrode which attracts them is called the anode. 

Sliort Olreulte. — When an electric generator has its terminals 
joined by a conductor possessing very small or negligible resistance, 
the generator gives out the largest current whi(;h it is capable of yield* 



CONHKCnOH OF BATTRRIBS IN 8EKIK!1 AltD PAIULLEL, 35 

lag, and In nuuij canes, eopcciallj in the cum of b accondar]' electric 
battery, or any tiJI liftving a very low internal roBbtance, or a dynamo 
nndiT the wrae coudition of low iutemiU n'Mistaitee, whieh alwuyii 
existii ill iwiDiwniul maehini'H. inuth duinu)^' muy be dune to the 
geoeratJ^r: thc^-ellurdynaiDo. a^ the euM' muy be, being often ruined un- 
lean the " short " limts a very short tune indeiJ. The d auger nt Hiirh a 
" short circuit" oeeurriug in avoided as far as pos^dble by placing 
fusible eut-Out« in c'ireuit, which will lie melted by the current flowing 
due to the "short eireiiit " if this la«l« for more than a very limited 
time, thuK intemiiitiLg ttie "ahort' ii,;d prcvenling the dumiiK^' to 
the [^■nenitor. 

Thi- U-rm " short circuit" may lUno be npplinl to the ca»i> where a 
cnrrcnt whirh is Mowing through, «ay, an elwtrolytii; bath, by rciwon, 
let UB imajrine, of some piece of metal falling across the mctnl tcrminalB 
of the bath, Qows through this metallic path thiu provided, which hau 



Pig. 25.— Battery nrr&nited (o series 

n very low rwdntance, inslt^ad of throusrh the higher reMBtance path of 
the electrolyte, in whieh ita fimctjon in to produce some I'hemical 
change. Tliiw, whilst this short circuit lnst« the electrolytic vat, which 
is short lirvuited, i« uselcBH, it« duty of providing bo much metal or 
other material JXT hour is comph'toly interrupted until the short 
circuit is removed. Liurtly, a enrrent gencTator may be internally short 
circuited, an has been described iu the rnm of a nerondary battery in 
which a plug of paste ha* fallen between the pisitive and negative platen, 
thus etectrii'ally connecting them inside the ceU tenninals. This is 
called an internal short circuit. 

Oonaaetlon of Battarlaa In Sarlaa atu P«rallal.— Ah haa 
already been remarked, batteries of electrical cells may be arranged 
oonnected in nerics to give a large voltage. This arrangement in 
shown in Figs, j; and 37, where the positive of one cell is connected to 
the negative of the ne^t, and no on, until the desired number of lella 
have been connected, and the linal micounectcd positive and negative 



36 



PBIMART AND 8KGONDART BATTEBIRS. 



of the end cell« form the terminals of the battery. The electro-motive 
force of Biich a battery is equal to the sum of the electro-motive forces 
of all the cells in the series. Usually only one kind of cell is thus 




Fig. 26. — Diagram of Cells arranged in Parallel. 

connected to form a battery, and if so the e. m. f . of the battery is 
equal to that of one cell multipUed by the number of cells in the 
series. 




T. 



T 




T 



T 



T. 



T. 



T 




Fig. 27.— Diagram of Cells arranged in Four Groups in Parallel, 
each group consisting of three in series. 

Cells may also Iw connected in parallel, as shown diagrammatically 
in Fiif . 26, where all the positives are joined together, forming the 
common positive terminal of the battery, and also all the negatives are 



CONNECTION OP BATTBBIES IN SEBIE8 AND PARALLEL. 37 

ojned together, fonoinii; tlie conunon neyBtivu of the battery. The 
. m. f. of tlie batterj thiu comiccted ik that of ouly utiu of the 



Fig. 28.— AtkiufloD'R Fin- ly.— Alkiiis.m'H AiripiTe- 

Ampice- meter or Voltmeter. meter or Volttiiiu-r titti-d witb 

lieiiLIo Icacia and louutvliuR plug! 

ooiutjlucnt celtK, but it if capable of giving n cuirent which is 
laifjer thiin one uell can give, in proportioD to the number of 
colls thmt eonuocled in parallel. The eellx of a batter; may be 



38 PBIMABY AND SUCONDABY BATTERIKS. 

arranjj^ed partly in parallel and partly in series ; thus Fig. 27 shoTirB 
a diagram of twelve cells arranged in four groups, each of thi^e in 
series with each other, the groups being then connected in parallel. In 
the diagrams the usual convention of a thick line for the negative 
element and a thin line to denote the positive element is adopted. 
Large and small cells of any given kind may be arranged in parallel 
with each other, but cells of different kinds should not be so connected, 
that is, a Bunsen cell should not be employed in parallel with a 
Daniell cell. Also in putting groups of cells in scries into parallel 
with each other, as in Fig. 27, the groups must not only be all of 
the same kind of cill, but each group must contain the same number 
of cells. 

Ampdrtt-metora and TToltnMtem. — There is a very large number 
of these instruments of ver}' different prices and construction now upon 
the market. The great point is that they shall be accurate, and also 
that they shall be fairly dead beat, that is, that the needles or indicators 
shall not oscillate about much when the current is changed, before they 
settle down to the position required by the changed current. 

A cheap and ratlier novel form of amp5re-meter and voltmeter which 
appears to fulill these conditions is made by Messrs. Atkinson, of 
Cardiff. Two views of this instrument are shown in Figs. 28 and 29. 
Fig. 29 shows an instrument provided with a flexible lead and plug 
connector for connecting on to different points. These ampere -meters 
and voltmeters are identical in general conslxuction and appearance ; 
they are intended to be attached to the wall, but there is no reason why 
they should not be made portable by attaching tbem to suitable stands. 
For many purposes, especially in a small electro-plating shop, it is an 
advantage, or indeed almost necessary, that the instruments should be 
portable, that is, that they shall be capable of being moved from one 
part of the building to another, and quickly and safely set up at any 
demred point. The price of these Austruments is about £ i . 

B«giilatinK B«tiataneea. — For adjusting the current to any desired 
value from any given source of constant e. m. f . it is very desirable to 
have some form of regulating resistance. Several forms of this class oi 
apparatus are described and figured at the end of the next chapter. 



CHAPTER 11. 

THERMOPILES- DYNAMOS.— THE COST OF ELECTRICAL 

INSTALLATIONS OF SMALL OUTPUT FOE 

ELECTRO-PLATINO, ETC. 

The Thermopile.— The GUlcher Thermopile.— The Cox Thermopile.— 
The Glamond Thermopile. — ^The Dynamo. — Points to be Con- 
sidered in Buying a Dynamo. — Care of Dynamo. — Driving Belts. — 
Starting and Stopping a Djrsamo. — Cost of Dynamos. — Cost of 
Motor-Dynamos. — Specification for and Choice of Motor-Dynamos. 
— Safety Precautions with Motors of Motor-Dynamos.— Choice of 
Electric Generators of Small Output, under Various Circumstances. 
—Comparison of Costs of Primary Batteries, Secondary Batteries, 
Dynamos, and Motor-Dynamos.— Costs of Gas Engines, Steam 
Engines, Oil Engines. — Gas Engines Run on Producer Qaa. — 
Regulating Resistances.— Determination of Polarity of Generators. 

ThmaopUmu. — ^The next form of electric generator which we have 
to ooQaider is that form of apparatus known as a thcrmopUe. An 
apparatus of this nature may be briefly described as one which converts 
the heat-energy of some burning fuel into the energy of tho electric 
current. At one time it appeared as though for all ordinary purposes 
this form of apparatus must completely displace the electric battery in 
which chemical reactions are the source of thee. m. f., and, indeed, tho 
undoubted fact that in the thermopile the energy of the heat of com- 
bustion of a fuel is directly converted into the energy of the electric 
current without any complicated intermediate apparatus such as the 
steam-boiler and the steam-engine, or the gas-engine, with the dynamo, 
seemed to indicate that the thermopile might eventually quite supersede 
the dynamo. These attractive dreams have not, however, up to the 
present been realised in practice, owing to the low efficiency of the 
thermopile, and chiefly to ite high prime cost and the care necessary to 
keep it in satisfactory working order. Until the advent of the 
"Cupron element" primary cell the thermopile might probably have 
had a fairly large field for small plating work and especially for 
laboratory work, but the present writer considers that, unless under 
very special circimistances, the thermopile would be better replaced by 
either *' Cupron elemente," secondary batteries, or dynamos. It is. 



40 THEBHOnu», 

howcviT, drsinible to dcwribe tho funus of thcnuopilc at preMnt 
employed, more eH)ieciuI1y tut it in BtiU quite powublc thut cheaper, 
struuger, aiul moro L'fficiitiiit fomm muy be developed iu thu future, nnd 
if thin improvcmeiit coiild be r^arriiid Hufficieotly far, it in certainly 
poisiHt t)iut the dynamo might be largi^ly or altugt-tlirr ilispluc-ed, hut 
up to the present there doei* not seem great prahabilily of thin deHirable 
end being uttaiued. 

The thermopile con«iKt» esBentially of ft «eri(n of jnnotioiiMof different 
motals, ulloyM, or other condueUng solids, which arc kept ut a hxed 
high t::mperature, and another net of altcraiitely arranged Einiilar 
juuutiouit, which arc maintained at a fixed low tempuruture. Tho 



Fig. 3o.-Giilcher'a Thermopile. 

theory of tho action is quite unnecGsaary for practu:al pnrposep, and aa 
wo are here merely coOHidering the thermopile aa a current gfnerutor 
wo nhall-aay nothiug on tho tluMrctioal uspeets of tlio matter, which 
may, however, by tlie aid of a moderate amount of nuithematicH, be 
oliliiiued from most troutises ou tlieuretlcal elcotricity. 

lu all fumuiof thermopile, then, with whieh the author is acquainted, 
the liut juiu:tiuiiK arc heated by mcauH of a gas burner, or a coke or coal 
fnmai¥, iiud the cool juuctiuus uro kept cold citliir tdniply by dirtv^t 
exposure to tho air or by the circulutiuu of u cumut of cold water from 
a ueighbouring tap. 

Tb« aiiieb«r TbannopUa. — This apparatus, a view of which is 
nbowu iu Fig. 30, is nianufaeturod by Julius Pintseh, Berlin, and 



THE GULOHER THERMOPILE. 



41 



18 listed by Franz Miiller — Dr. Geitfuler's successor — of Bonn am Rhein, 
Germany, at a price of 190 marks for the largest size, with 23 marks 
extra for a gas pressure regulator. 

Dr. G. Langbein, of Leipzig-Sellerhausen, Germany, also lists this 
thermopile at the same price, whilst the same size of thermopile may 
also be purchased of Messrs. O. Berend & Co., of Duncdin House, 
Basinghall Avenue, London, E.G., at a price of £14 $8., or with a gas 
pressure reg^ilator extra, the cost is £15 156. 

It is claimed for these thermopiles that tliey may bo employed con- 
tinuously, and that their efficiency does not vary, neither does the 
apparatus deteriorate. They yield a constant clectro-motivc force 
which may be slightly varied by turning the gas up or down, and the 
internal resistance of the pile is not largo. A thermopile, of course, 
causes no polarisation troubles like a primary battery. 

The following details as to price, etc., of this type of generator are 
given by Messrs. O. Berend & Co. : — 







Bizc 




No.x. 


No. 2. 
50 


No. 3. 


Kumber of elements 


26 


66 


E. M. F. in volts .... 


I "5 


3 


4 


Current strength obtainable when 
the external resistance is equal 














to internal .... 


3 


3 


3 


Internal resistance in ohms 


25 


0-50 


0-65 


Approximate consumption of gas 








in cubic feet per hour 


2 


4'9 


6-4 


Price of thermopiles 


£6 7 6 


;fl2 


£14 5 


Price of gas regulators 


£1 10 


£1 10 


£1 10 



With reference to the foregoing table it must l)c remarked that when 
the thermopile is running with the currents there stated, that is, 
when the external resistance is equal to the internal resistance of the 
generator, it is working at its greatest rate, that is, it is giving out 
electrical energy to the outside circuit at its greatest rate. 

The following instruction.^ are given as to tlio use of this thermo- 
pile: — 

"First place the tubular i)orccliiin chinmeys iu theu* phui-n, ou 
top of the elements, by inserting the projecting mica tube in tlie holes 
until the porcelain rests on the metal ; in tliis position they must 
remain. Thereupon connect the thermopile by a rublx^r tube to the 
gas supply, open the tap, and after a lapse of about half a minute — 
the time it will take for the aii* to csca^)e fi'om the tubes — set light to 



4* 



TBKRHOPIIiES, DYNAMOS, ETO. 



the gas eflcaping from the tubular elementH at the mouth of the porce- 
lain chimneyB. (Sec that all the bumoni are alight to prevent escape 
of ga8, and to ensure full ciiiciency of the thermopile.) When the 
burners are lighted the thermopile is ready for use, and requires no 
further attention. In 8 to lo minutes after lighting up, the pile is 
sufficiently heated to give off a perfectly constant e, m.f. The consumj)- 
tion of gas gpiven in the table is calculated upon a gas pressure of 
30 m/m==i'i8 in. water column. Before packing, each thermopile i^ 
carefully tested, and adjusted to the highest admissible gas pressure, viz. , 
50 m/m = I '96 in. water column. As the gas pressure varies consider- 
ably, it is strongly advisable to always insert a gas pressure regulator 
as quoted in list, but in most instances the gas companies will be able 

to inform users of their normal 
X^ressure, and when such normal 
pressure docs not surpass the 
nuiximum, it is not ne(*«ssary to 
use a regulator. Simply turn 
off the gas tap for putting the 
thermopile out of work. 

*' Caution. — 2)o not interfere 
with the ga» inlet on the ther- 
mopile ; any increase of thie inlet 
will ruin the instrument. 

The thermopile must be kept in 
a dry places and sftould be pro- 
tected from acid vapours^ which 
would attack the metal. It is 
advisable to fix the pile to the waU 
on a Jiorizontal bracket at a heiyht 
suffieient to protect it from inter- 
ference.^* 

Fig. 31.— Cox Thermopile for gas rrv.- .x. 1 • x j i. 

without water-jacket. T^"^ thermopile, mvented by 

Mr. H. Barnngton Cox, is 
manufactured by the Cox Thermo Electric Company, Limited, at 
the Cox Laboratory, St. Albans, Herts, England.* Several general 
views of this form of thermopile are given in Figs. 31, 32, 33. 

The hot junctions are heat«d by means of a Bunsen gas flame as in 
the Giilcher pile, but in the larger sizes of the Cox thermopile the 

* I hear that the English Company has been wound up, but the 
American btisinesB is, I believe, still carried on at 126, Liberty Street, 
New York. -A. t. 




43 

odd juDctknig arc kept cool by mcanB of a stream of water from the 
ordinary bupply tap, whereua in tho Giiluhcr pile, air cooling alone is 
employed. The foltovrtng- directions for usn &re given by llie makeTB 
of this thermopile : — 

I. Direutiuiu for u»c of HmaUer-Bized genpraUir, heated with gtui 
burner, and aot supplied with vinUir cooling mraugenientH [Fig.Jt"). 

The g<eDcrstor with its gut burner should be placed upon Home 
eonvenient mipport, mitb us b table or stand, where the apparatus 
operated can be conveniently 
placed. Use a sufficient length 
of rubber tube to connect the 
burner to the nearest gaa jet in 
the room. Soe that the de< 
fleoina, which are shown at d 
in Kg. 35, are an nearly at po9- 
sble in the centro of tjio gene- 
rator : thia is neccBxary in order 
that the heat from the burner 
shall be supplied equally to all 
parts of tho raorhinp. The 
bamer may be lighted at cither 
tho top of the tube or at the 
top of tho generator. The de- 
flectors require to bo heated up 
to a cherry-red heat, and suf. 
ficient gas must be supplied lo 
do t^iia The gas flame should 
never impinge upon, or strike 
against the interior of the 
clement, that is to say against 
the inside of the disc, which is 
the part that produces the elec- 
tricity. TTii^ last precaution Fig. 3..-C0X Thermopile for j«, 
is extmnely important. The fitted ,v.th water-j.cketand 

pile may be run conKnuously. ''"«'''«' ""Pf"^ 

and provided the gnf supply is Klcndy, the current will not vary in the 
slighlest degree, but, if it i« iiijuired, the strength of tho current may 
be increased or decreased by regulating the amount of gas supplied. 
More gas will give more nurrcnt, less giis less ciuTout, Short circuiting 
thegenerator does not injure it in anyway. It should be remembered 
that the elcmimt under working conditions becomes hot, and must 
not be handled without uidng the fire-proof asbestos pads provided, 
or some other suitable means. To stop the pile actiug simply turn off 



44 



THERMOPILES, DYNAMOS, ETC. 



Heat in the form of stored energy will operate the apparatus for 
some minntes after the gas is put out. The generator should be 
allowed to thorouglily oool before it is handled. 

2. Directions for installing and using the larger sized generators, 
heated with gas and supplied with water circulator. 

Screw the machine upon the wall in a vertical position and in such 
a place that it may be as free as possible from draughts of air. Connect 
the gas burner A, Figs. 34 and 35, on the pile by mcauM of a rubber 
tube to a convenient gas supply, also connect the water tubes E E in 
the same manner with the water supply, taking care that the water 
enters the pile at the bottom opening, following the direction of the 

arrows so as to leave at 
the top as shown in the 
drawing. Bemove the 
string and tag which is 
tied about the deflector 
tripod at the top of the 
machine, and see that 
the deflector rod D rests 
in the centre of the 
burner B. Also note 
that all screws are tight, 
especially the connec- 
tions. The use of small 
lead or compo piping is 
reconmiendod instead of 
rubber tubes. A lead or 
compo pipe is found to 
be more satisfactory, 
especially if a pipe is 
to be kept in constant 
or practically constant 

UiSG. 

To start the generator, 
turn on the g»a and 
water and light the ga«, the flame &om wliich Kliould apx)ear as in 
^^g- 34- Obnerve that the water is running freely tlirough the 
apparatus, though only a small current is necewiary. The correct 
quantity is dotenniutxl by the temperature of the wiwte water, which 
should be kept at a temperature of from 70" to 80"" Fahrenheit. The 
temperature must on no account be permitted to exceed 150"^ Fahr. 
For ordinary purposes the temperatiu^ of the cooling water can be 
determined with sufiicicnt accuracy by placing the hand upon the 
casing, which should not feel more than slightly warm. This, of 




Fig. 33. — Cox Thermopile for Spirit Lamp, 
without water-jacket. 



TSK OOZ THKRHOPtLB. 

oouTBe, niuHt be done when the pile has been lig'htcd up for bc 
orfift«en minutfn, ooJ had had time 
to rcai'h its full temperature. Too 
mnrh water is uselesfl. The actual 
temprDLttire of the wHfte water maj 
of bourse be obtained by platting 
a thetmometor bulb in the itisaing 
dtreain. An electric current may be 
taken from the pile dircttly it 
i4 lighted, but the output steadily 
s with the time until the 
B reached in about ten 



To atop the pile, turn off the gaa 
and wat«r, but do not disconnect 
the wat«r pipen. Always allow the 
water jacket of the pile to rem^ 
full. 

The same precantionN in lighting 
the gas and regnlatitig the height 
of the gas flame apply to the 
water- jacketed thermopile : 



Fig- 34.— Section of Cox Thei^ 
niopile having water-jacket. 
FUme baming correcUy. 

the smaller unjacketcd form. The 

appearance of the flame ehould be 
like that nhown in Figa. 34 and 
36. In Fig. 35 a gnH flume is 
shown burning incorrectly, and in 
such a manner aa to damage the 
{rile. The correct form of flame 
can always be obtained by turning 
the gas up or down, llie pile 
muRt never be used without the 
drculating water running. These 
are the only points which roquire 
attention, and by taking thcHe 
precautions the natural life of 
the machine ia indefinitely long. 
Negligence in regard to their obser- 
vance may spoil the pile In a few 
hours. To observe the gas- 
flame look from the bottom of 
the pile upwards. One form of 
the Cox generator in miule to be 
run with a spirit-bnmer. Fig. 33. 
All forma are claimed by the makera to be economical and 



Fig. 35.— Section of Coi Ther- 
mopile, showing flame burn- 
ing incorrectly. 



4(S THeRMOPtLRS, DTMAHOS, Bid. 

etroDg:. The following details as to price and output have t 
supplied : — 

0«9C MqarKtM' cor Oka wltb Watar-Jaokat. — 



J. 35.— Section of Cox Thermopile tor gas, without 



Prim, nunipli-tp Tiih 



PriceH for Beparate items :- 



Element 

Deflefitora .... 
Spirit or gsB-bunier and stand 



THB OLAMOMD THBBMOPIIjB. 47 

TlM OlaiBoad ThannopU*.— This pile was originally made by the 
Thermo Generator Company in or about 1876, and ihe following are 
details oonceming their oost and output : — 



Volts. 


Internal resist- 
anoe: ohms. 


Short circuit 
current. 


Oas consumption : 
cubic ft. per hour. 


Price. 
£ 8. d. 


2 


i-o 


2 amperes. 


— 


300 


3 


1*5 


2 » 


3 


400 


6 


30 


2 1, 


5 


6 10 



DltS. 


Internal 
reslstanoe. 


Short circuit 
caireat. 


Coal gas oonsumiH 

tion in cubic feet 

per hour. 


3 
10 


o'6 ohms. 

2-0 „ 


5 amperes. 
5 


6 
23 


20 


4-0 n 


5 » 


37 



12 6-0 2 „ 9 13 o o 

34 12- 15 27 „ 37 32 o o 

Piles having a lower resistance were al«o made, of which the foUow- 
ing results were given : — 

Coal eas oonsumiH 

Price. 
£ 8. d. 

800 
20 o o 

32 o o 

The piles were spoken well of by Sir W. H. Preece, and were by his 
directions employed in the Goyemment Telegraph Service, but owing 
to the fact that the junctions after a time were found to fuse by coming 
into direct contact with the burning gas, and to break by too sudden 
cooling and heating, and also because moisture and products of 
oombnstion apparently in time corroded the junctions, the use of the 
piles was discontinued ; but Sir W. H. Preece stated that the pDes 
were far more compact than ordinary telegraph batteries, and 
expressed his belief thai the difficulties mentioned above could be 
overcome. The Company, however, collapsed, and were unable to 
supply a complete set of thermopiles contracted for to the Postal Tele- 
graph Department in 1876. Whether the pile is manufactured under 
the name of Clamond or any other title the present writer is not aware, 
but apparently, with a few not very complicated modifications, this 
pile could be made as successful as any others on the market. 

The following is a description of the orig^al Clamond pile given by 
Mr. Latimer Clark at a meeting of the Society of Electrical Engineers 
in 1876, an account of which, accompanied by an interesting discussion, 
may be found in the Journal of that Society, vol. v., p. 321, et seq, 

Mr. Latimer Clark states that : — 

' ' The mixture employed by Clamond consists of an alloy of 2 parts 
antimony and i of zinc for the negative element, and for the positive 
element he employs ordinary tinned sheet-iron, the current flowing 
through the hot junction from the iron to the alloy. The combina- 
tion is one of great power. Each element consists of a flat bar of 



48 thbemop:-"Eh, ptnamos, xto, 

tho nlln; from 2 inobai to zj indicia in length, and from f to t inch 
in thicfcnpwi. TJieir form ib idiown in Fig. 3?, Ly which it will be 
SP<Ti that, looking- at tho plan, they are Bpindle-shaped or broader in 
tho middle than at the ends. The ahoet-tin ia stiimped out in (he 
fonu shown in Fig. 38 ; the narrow portion in then bent in the forms 
shown, in which ntate they arc ready for being fixed in the mould. 
The melted alloy ia pouted in, and, before it hat cooled, the mould ii 
opi'ntil and the burs removed with the hign »ei™rc!y cast into thcln. 
The mould ia heated nearly \*> the melting point of the alloy, and 10 
or 1 2 baro aro cant at one time. A little zinc is Rdded from lime to 
time to make up for the lotw due to volatilisation. Tlie alloy melts at 
about 500° Fahr. ; it cipaudH coniuderably on cooling. The more 
frccjuently tho alloy is recast the more perfect becomen the miiture, 
BO that old piles can bo reconverted with advantage and with little 
loHs beyond that of the labour. The alloy is extremely wenli and brittle 



t 



and eiuuly broken by a blow— iu fact, » ncarrely stronger than loaf 

"Tlic tin lugH nre bent into form, and tho bam are arrniigcd in a 
rndiul manner round a temporary braHs cylinder, as shown iu Fig. j;, 
a thin slip of mica being ioscrtod between the tiu lug and the alloy, 
to prevent contact, except at tho jimction. Tho number of radial 
bars varies with the sixo of the pile, but for tho usual siKcH eight or 
ten are employed. As fant as tho bars are laid in position, they are 
secured by n paste or cement formed of powdered asbestos and soluble 
glass, or solution of silinato of potaasa ; flat rings are abio formed of the 
same composition, which possesses considerable tenacity when dry ; 
and as soon as one circle of bars Lt completed, a ring of tho dry asbestos 
cement is placed upon it, and another cirole of elementjt is built upon 
this, and so on until the whole battery is formed. Cast-iron frames 
are then placdl at top and bottom of the pile, and drann together by 



THB GLAUOND THKUKOPILB; 49 

screws and rods, so as to oonaolidate the whole, and in this oondition 
the pile is allowed to dzy and harden. Looked at from the inside, the 
faces of the elements form a perfect cylinder, within which the gas is 
burned. The inner face of each element is protected from excessive 
heat by a tin strip or cap of tin bent romid it ; before it is embedded in 
the cement the projecting strips of tin from the opposite ends of each 
pair of elements are brought together and soldered with a blowppe 
and soft solder. The respectiye rings are similarly connected, and the 
whole pile is complete, except as regards the heating arrangements. 
The positive pole of these piles is always placed at the top. Gumming 
was the first to use this stellar arrangement of couples. The pile is 
usually heated by gas mingled with air, on the Bunscn principle ; gas 
is introduced at the bottom of a tube of earthenware, which is closed 
at the top, and is pierced with a number of small holes throughout 
its length, corresponding, approximately, in number and position with 
the number of elements employed. Before entering this tube, the gas 
is allowed to mix with a regulated proportion of air, by an orifice in 
the supply tube, the size of which c^n be adjusted ; the mixed gases 
escape through the holes in the earthenware tube, and there bum in 
small blue jets, the annular space between the gas tube and the ele- 
ments forming a chimney to which air is admitted at bottom, the 
products of combustion escaping at the top. In order to prevent 
injury from over-heating, and to diminish the consumption of gas, 
M. Clamond has introduced a new form of combustion chamber, by 
which he obtains very great advantages. Tills form is shown in 
Fig. 39. The mixture of air and gas is burnt in a perforated earthen- 
ware tube, as before described, but instead of extending the whole 
height of the battery, it only extends to about one-half of its height. 
The earthenware tube is surrounded by an iron tube of larger diameter, 
which extends nearly to the top of the battery, and is open at the top. 
Outside this iron tube, and at some distance from it, are arranged the 
elements in the usual manner. A movable cover fits closely over the 
top of the pile, and a chimney is connected to the bottom of the pile. 
Leading oft from the ftnnnlRr space between the iron tube and the 
intmor faces of the elements, the air enters at the bottom of the iron 
tube, and the heated gases, passing up the tube, curl over at the top, 
and descend on its outside, escaping eventually by the chinmey. 
The elements are heated partiy by radiation from the iron tube, and 
partiy by the hot gases which pass, outside the tube, downwards 
towards tlie chimney. By this arrangement, not only is great economy 
of gas cfifected, the consumption, as I am informed, being reduced by 
one-half; but the great advantage is obtained that the jets of gas 
can never impinge directiy on the elements, and it is thus scarcely 
possible to injure the connections by over-heating. In the event of 

u 



50 IBEBMOPILEB, DYHAHOS, ETC 

a bad ronnectinQ oonurriiifr. it in ettey to find ont the imperfpr.t eInneDt, 
and throw it out of ui« by nhort-cirtiiiliii(r it ovct with n pipce of wiro, 
and the mRkctn huve no diifiriilty in tuttiiifjr out adcfii'tivc element 
and rppliuMntr it by h nound one. Ci)ke aud (iharooiU have iJ«) been 
employed An a xounie of heat, with very );reiit economy oud Buiflxwi ; 
in fai^t, there are many countrie« and plnucs wliere gas would not In 
procurable, but where eharcual or vuke eould bu readily ubtuiued. 



Fig- 35- — Section of Clamond'B Tlieniiopile. 

The tension produced by Clnmond'H thcnuo-clemcuts in EiU'b that each 
twenty elements may be taken an pmcticaUy equal to one Daniuiri) 
cell, or about one volt." 

It in stated that a Clamond pile of lOO l)arB, nith the oousumpliou 
of 5 cubic feet of gas, dcpoMto about i ounce of Hilver per liour. and 
the same machine, amin^d in multiple arc (that in, for ^na'-titii) will 
deposit about I ounce of chopper in the Mime time : 400 large barn, 



THE DYNAMO, 5T 

consuming 2 lbs. of ooke per hour, will deposit abont four times the 
above qaantities in the same period of time. 

Messrs. L. and G. Wray introduced some important improvements 
upon the form of diamond's thermopile as described by Mr. Latimer 
Clark, the descriptions of which were given in the discussion on Mr. 
Clark's paper {loc, eil.), but, as far as I am aware, there axe no pub- 
lished details concerning the output, price, gtus consumption, and life 
of any other thermopiles of sufB.cient magnitude for any electro- 
chemical work beyond those g^ven above. 

Tli« Bjiuuno. — ^Thc third and last, and, for the larger operations, 
the most important current-generator is the dynamo. As was the 
case with the other forms of current-generators, no attempt will be 
made here to treat of the theory of the dynamo, nor its construction. 
The theory is well understood and the art of construction has reached 
a high degree of perfection. Particular information on these points 
dues not concern the elcctro-metallurgiHt, who is merely interested in 
the cost, efficiency, durability, and method of treatment of the finii^hed 
machines. The largo number of modem treatises on the theory and 
construction of the dynamo now available make it an easy matter 
to obtain all details for tho^so anxious to be acquainted with these 
subjects, but (let it be remembered) such knowledge is in no way 
neceMary to the practical electro-metallurgist. 

The dynamo then, in so far as we are concerned, is, like the electro- 
chemical battery and the thermopile, merely a source of e. m. f., 
which when connected up in a conductiug circuit will yield a larger or 
smaller current acxx)rding to the largeness or smallness of its e. m. f. 
and the smallness or largeness of the resistance placed in circuit. 

There are several forms of dynamos available for obtaining an 
electric current, but there is only one fonn which is of any practical 
use fur the electro-metallurgist, and that is the particular form of 
machine known as the shunt wound dynamo. Other forms of 
dynamos may possibly be employed, but they possess no advantage 
in cost or efficiency, and even when used by experienced persons for 
electro-chemical work, are always liable to cause more or less serious 
trouble from time to time. The soundest advice, then, to anyone about 
to purchase a dynamo for electro-chemical work of any other form 
than the shunt wound machine, is '^ Don't.*' 

The dynamo is so largely employed nowadays that it is difficult to 
imagine that anyone who is in any way couneited with tetlmical work 
is not familiar with at least the general apiM'arunce of tlu^ ma(*hinc. 
It is not possible to tell by mere inspection the efficiency and output 
of a machine, and the general details of equaUy good dynamos may be 
very different. Every machine, however, musit contain the following 
ten important parts (see Fig. 40) : — 



52 THERM0PILK8, DYNAMOS, ETC. 

1 . Field-magnets, x, made of steel or inm (of almost any shape). 

2. Field -magnet windings, ic", consisting of insulated copper- wire 
coils carried round the field magnets. 

3. Armature shaft or spindle, e e, which rests on and runs in — 

4. The armature shaft bearings. 

5. The armature, ▲ a. — This consists of a collection of copper 
wires or bars attached to a cylindrical core of iron plates. The 
complete structure ia keyed firmly to the armature shaft. 

6. The commutator, c. — This is a cylindrical assemblage of copper 
or occasionally iron segments, having an insulating layer between 
each segment. It is connected by wires to the armature, and 
is keyed on the armature sliaft at one end of the armature. 

7. The brushes, b b. — These are copi)er-wire gauze or sometimes 
carbon blocks, which are held in what are called brush-holders, 
which in their turn are held on the rocker. There are at least 
two brushes and may be more, but there is always an even 
number. The brushes are held pressing ux>on the commutator 
by means of hold-on springs, and when the dynamo is run- 
ning the commutator slides beneath the brushes, with which 
it is always kept in close contact by the brush springs. 
The brushes are normally held in a fixed position whilst the 
machine is running, but can, if it is desired, be moved forward 
or backward a certain distance by rotating the whole of the 
rocker to which the brushes are attached. The rocker is carried 
on one of the fixed bearings of the armature spindle, on which it 
can rotate, but it can be fixed at any desired position and ren- 
dered immovable by means of a pinching or clamping screw. 

8. The machine terminals. — These are usually fixed to a small 
wooden panel on the side or top of the field-magnets of the 
machine, and it is from these terminals that the current is taken 
off from the machine by means of conductors running to the 
vats direct, or more usually vid a switchboard. The terminals are 
also connected one to each of the brushes of the machine, and 
also one to each of the ends of the field-magnet windings. 

9. The pulley, p. — If the machine is belt-driven this is keyed to 
the armature shaft at the opposite end of the armature to the 
commutator. If the machine is not belt-driven there is a 
coupling for direct coupling to its engine. 

10. In many cases there is also a fly-wheel keyed on to the 
armature shaft, especially when very steady speeds are required, 
but tliis fly-wheel may be, and generally is, absent. A view of 
an electro-plating dynamo made by the Greneral Electric Compauy 
for 10 volts and 280 ampdres is shown in Fig. 41. The price of 
this machine is £^0, 



A dynamo U really only a piece ot apparatus 
mecbanical energy of gome Hteam- or gaB-engine ii 



54 TBERHOFILB9, DVNAMOS, ETC. 

electric current, ami by itself can give out no energy nnlesa it haa 
mechanica! energ-y conntantly given to it by tome engine, rach aa a 
Bltam-engine, gaa-eogine, oil-engine, electric motor, or h *ater or 
wiud turbiuc. In aetting up a dynamo it is therefore ueceseary to see 
that a Houree of a BufHcient amount of mechanical energy is firat 
provided. 

The number of makers of good and reliable dynamos now to be found 
islHt^, and itinditfitult to mention any parliculBr machine or machinea 
ax being apecially good In order, therefore, to purehasp and instal a 
nuituble dynamo and engine for any porpoae involving more than a 



Fig. 41. — G. E. C. Btectro-ptating Dynamo, 10 volta, 280 amperes. 

fimall outlay, it in, if Ihe person deairona of obtaining the plant is not 
an eh'ctrical engineer himiielf, very desirable to obtain the BAraataDce of a 
eonmilting electrical engineer, who will draw out apedficationH and 
obtain tendern for flupply, delivery, and erection ; by thin nieana usuiilly 
a good deal of money and time ia aaved, and satisfaction obtained at 
on outlay of a BmuU pcrccnlJige of the total coat of the plant inittalled. 
For small plants, however, and for porwins having nomc knowledge of 
mechanical, if not of electrical, engineering, it may he worth while 
obtaining the dynamo direct, and in this caiie il in advii<able to write, 
stating the following details, lo a nnmher of firms mauufacturing 
dynamoe, and from their quotaliona a little conuderaUon will enable 



THE DTNAMO. 55 

the piirohaser to select the machine whose prioei output, etc., are best 
suited to his needs and pocket : — 

Details eoneeming Shunt Dynamotfor 



Power available to run dynamo, brake-horse-power. 

Current required not less than ampdres. 

Volts required, about Tolts. 

Speed at which driving engine runs, revs, per min. 

The machine must not spark under any load u^) to full load when 
once the brushes are properly adjusted. 

The manufacturer Ib asked to give the following details conoeming 
the machine offered, for the output above stated : — 

Volts on machine on open circuit at normal speed. 

Volts on machine at fuU load current, at normal speed. 

State what full load current is. 

State whether voltage of machine can be varied by field rheostat, 
and, if so, between what limits. 

State normal speed of machine. 

State diameter and width of face of pulleys supplied. 

State power required to drive dynamo at its full load at normal 
speccL. 

State power required to drive dynamo, when giving the number 
of amperes specified as being required, at normal speed. 

State resistance of machine from brush to brush hot. 

State temperature rise of armature and of field-magnets after 
running for six hours at the full load current at normal speed. 

State direction of rotation. 

State price of machine delivered at with fast and 

loose pulleys, belt fork, and striking-gear complete, and if of 
size requiring above ij horse-power to drive it, also state 
separately extra cost of foundation rails and belt tightening 
screws and field rheostat, if the latter is advisable. 

Other things being equal, the machine with the smallest resistance 
from brush to brush, and the least difference between its voltage at 
zero load and full load will be found the most satisfactory, whilst a 
low speed and a large output ore also good X)oint8 which, however, 
tmf ortunately , usually involve correspondingly good prices. The same 
remark is true of a low temperature rise of both armature and field- 
magnets after a prolonged run at full load (the rise should not be 
greater than about 70"* Fahr.), and also the smallness of the power 
required by the machine to drive it at full load. It is particularly 



56 THERMOPILES^ DYNAMOS, ETC. 

neceroary that the power required by the dynamo to diiye it at full 
load shall be stated in brake-horse-power, as other unita of horse- 
power are misleading. It is desirable that the speed should not be 
greater than about 1,500 per minute. 

Oare of a Hynamo.- — When once a dynamo is erected and running, it 
is necessary to understand that by constantly observing certain simple 
precautions (which are much more readily carried out than is the case 
with the similar precautions required when employing primary or 
secondary batteries, or indeed with thermopiles) the life of the 
dynamo can be indefinitely extended, and, as a matter of fact, the 
repairs and depreciations incidental to running a properly looked after 
dynamo is not a quarter of the amount expended on a secondary 
battery which is equally carefully attended to, whilst the time and 
trouble necessitated in carrying out these precautions with the dynamo 
is very much less than is the case with cells. 

It is, if possible, Tery desirable that a dynamo employed for electro- 
plating shall not be used in the same room as that in which the plating 
tanks are situated, for otherwise the vapours from the vats, more 
especially if these are run hot, are liable to condense on the machine 
and rust it, and reduce its insulation resistance until at last some 
short circuit of tiie machine may occur. It must be carefully 
remembered that probably the most active agent in deteriorating a 
dynamo is damp. 

The bearings should be kept well ofled, and for small machines a light 
mineral oil may be employed : it is, however, necessary to guard against 
the lubricating oil creeping over on to the armature and commutator. 
This mishap is provided against in well-designed macliines by having 
a V-shaped ring shnmk on the shaft just outside the joiimals, which, 
as the oil creeps over it, throws it off on to a curved oil hood cast on the 
bearings. 

Probably the most important point in the wear and tear of a dynamo 
is that involved in the commutator, and every effort must be made to 
keep this small. The copx>er brushes bearing on the rapidly rotating 
bars of the commutator are gradually worn doi^n, and in their turn the 
brushes gradually wear more or less severely the surface of the com- 
mutator. The wear may be kept small by seeing that the surface of 
the commutator is very lightly coated with a thin film of vaseline, and 
the brushes must be carefully trimmed. The most destructive agent 
in tlie wear of the commutator is not, however, the friction between 
the brushes and the commutator surface, but is due to the sparking 
which occurs at the brushes. This sparking tends to pit the siu'fnce of 
the metal where it occurs, and once this pitting has taken place the 
action proceeds at a constantly accelerating rate. The great thing, 
then, is to avoid as far as possible all sparking. As far as the 



OARE OF A DYNAMO. 



57 



attendant ia able to do thin it can be done by Beeing that the bnihhes 
are carefully filed to a flat bearing surface. For this purpose it is 
advisable to make a brush clamp of ca8t iron, as shown in Fig. 42. 

The angle of the slope at the top of the clamp may be set for each 
particular dynamo and particular thickness of brush in the following 
manner :— Draw two parallel lines on a sheet of paper, Fig. 43, having 
the distance l)etwtH}u them equal to the thickness of the brush which is to 
be employed. Then take a compass, and with one \x>hii at A, set off 
an arc whose radius is equal to the thickness of about i| to 1} com- 
mutator segments, cutting the other line at the point B. Join A to B 
and this line gives the angle of 
slope of the top surface of the 
required brush filing clamp. To 
file up the brush place it in the 
groove G of the clamp and place 
the covering piece, C, over the 
brush, and then place in a vice 
and file the top end of the 
copper with a fine file with an 
outward stroke only, until the 
copper surface lies even with 
the sloping cast-iron surface of 
the top of the clamp. The 
brush is tlien fastened in the 
brush-holder, so that the sloping 
surface lies closely on the sur- 
face of the commutator. If the 
machine is a two-pole machine 
the points of contact of the 
brushes are arranged at diame- 
trically opposite points on the 

commutator. The pressure with which the springs hold the brushes 
in contact with the commutator is usually adjustable, and should 
be arranged to be not too heavy or the brushes cut the commu- 
tator severely, and not too light or the vibration of the running 
machine causes the brushes to jump slightly, thus causing bad 
sparking. When sparking is observed at the commutator the brush 
rocker must be slowly rotated backwards and forwards until some 
point is found at which the sparking is absent or at a minimum, which 
should mean a very slight amount of sparking indeed. If this is not 
the case, at the earliest opportunity the brushes must be removed and 
trimmed as already described, and again adjusted. If the sparking 
still continues, and the machine has previously worked sparklessly, or 
nearly so, it is probable that either the machine is b^g overloaded, in 





Fig. 42. — Brnsh Trimming Clamp. 



58 



THBBMOPILES, DYNAMOS, ETO. 



Ar 




which case sparking is often quite unavoidable, or some breakage has 
occurred in the armature windings. Do not overload a machine so as 
to cause sparking, for to run a machine with sparking brushes ie the 
most extravagant method of running it possible. But if the sparking 
is not due to this, but has set in and cannot be stopped by any of the 
means noted above, call in an electrician to put the trouble right. Some 
machines, owing to faulty design, will always spark, and it is particu- 
larly necessary in purchasing a machine to ascsertain by experiment 
that the machine will run at its full or any lower load, with properly 
adjusted brushes, without any sparking. If a machine does not spark 

at the brushes the commutator quickly assumes a 
dark blackish-brown polished appearance, which is 
very characteristic of a properly run dynamo. If in 
spite of all the precautions mentioned above, or 
because of their neglect, a dynamo which did not 
spark when first set up commences to spark, and, as 
a result, the commutator gets out of truth and is 
no longer truly cylindrical, but is worn down at 
certain points, either due to the sparking or to the 
cutting effect of too largo a brush pressure, it is 
advisable to adjust a slide-rest parallel to the arma- 
ture spindle, and with a very sharp and fine-nosed 
tool turn down the surface of the commutator until 
it is once more truly cylindrical. Care must be 
taken in performing this operation : first, that a 
very light cut is* taken ; second, that the rest is 
parallel to the armature spindle, or otherwise the 
surface of the commutator, after turning up, will be 

setting angle of eonical instead of cylindrical ; third, before starting 
Brush Trimmmg , . • i;*. i. • Iv . . 

Clamp. *^® machme agam after turmng up the commutator 

examine the commutator very carefully to ascertain 

whether any metallic copper has dragged across the insulation between 

the commutator bars. If it has, it must be carefully removed. It is 

to avoid the danger of this occurring that a sharp cutting tool and a 

light cut are necessary in the turning operation. Running the dynamo 

with such a piece of copper connecting two neighbouring commutator 

segments may cause very serious damage indeed to the armature and 

necessitate lengthy and expensive repairs. It is only in the ca«e of a 

bad form of dynamo, or very serious neglect of the prox)er precautions, 

that it should lx»come necessary to have recourse to turning the surface 

true again. In any ciise it is evident that only just sufficient metal 

should be removed by the turning process to get to the Ijottom of the 

cavities worn in the commutator. 

The armature shaft may be rotated by hand during the turning, and a 



Fig. 43 
Diagram for 



DniVINO BELTS. 59 

little milk or soap and water may be used as a lubricant. The tool should 
be ooDstantly re-sharpened. If it is noticed that the commutator is getting 
rather rough, but before the trouble has gone so far as to produce real 
inequalities of any aze on its surface, necessitating re- turning to remove 
them, the roughness may be conTeniently removed by means of a 
cylindrical segment cut in a thick piece of board whose internal radius 
is eqiial to the external radius of the oommutator. If this cylindrical 
recess is lined with a piece of the finest glass paper and the dynamo is 
run at its usual speed, the brushes being removed, then, if the cylin- 
drical recess lined with glass-paper is pressed lightly upon the revolving 
commutator, it will rapidly smooth it up bright. This treatment 
may also be used after the commutator has been re-turned, in order 
to give it a laat smooth surface. 

The dynamo must be kept as free as possible from dust, and if the 
presence of dust is unavoidable, then the dynamo itself must be 
closed in in some suitable cover. In any case, dust which gradually 
collects, and especiaUy the copper dust arising from the wear of the 
brushes and the commutator, may be conveniently removed from the 
end windings of the annaturc and other places where it collects, by means 
of blowing with a pair of bellows. The foundations of the dynamo 
must be firm, and the machine bed-plate must not move at all perceptibly 
when the dynamo is being driven. 

Drltrlns Belts. — Concermng driving belts Kr. Watt remarks as 
follows : Most users of dynamo machines, polishing lathes, and other 
machinery driven by steam-power or gas-engines, will have experienced 
some trouble from the breaking, slipping, or slackening of the driving 
belts. Since a few hints upon these matters may prove acceptable, we 
give the following extracts from an interesting and thoroughly prac- 
tical paper, by Mr. John Tullis, of St. Ann^s Leather Works, 
Glasgfow.* 

**Ifain Driving Leather Bella should be manufactured so that when 
the joint is made while the belt is in its place, it ought to present the 
appearance of an endless belt. After having been taken up once or 
twice during the first year, good belts such as these require very little 
attention during the subsequent years of their long life. If the belt 
is driving in a warm engine-room, it ought to get a coating of curriers' 
dubbing three times a year. All belts having much work to do ought 
to present a clammy fore to the pulley, and this condition can be best 
maintained by applying one coating of dubbing and three coatings of 
boiled linseed oil once a year. This oil oxidises, and the gummy sur- 
face formed gives the belt a smooth, elastic driving face. A belt looked 
after in tliis way will always run slack, and the tear and wear will be 
inconsiderable. On the other hand, dry belts have to be kept tighter, 

• Scottish LeciUker Trader ^ July, 1885. 



6o THKRMOPIIiBB, DYNAMOS, ETO. 

because they slip and refuse to lift the work. The friction of the 
running pulley ' bums the life ' out of the belt while this Blippiug ia 
going on." 

Fixing the Belt. — As to which side of the leather ought to be placed 
next the pulley, Mr. TuUia says, " It is well known that by running 
the grain or smooth side next the pulley, there is considerable gain in 
driving power. However, by using boiled linseed oil, as before men- 
tioned, the^f^A side will soon become as smooth as the grain, and the 
driving power fully as good. A belt working with the grain side 
next the pulley reaUy has a much shorter life than the belt running 
on the flesh side. The reason is, the one is working against the 
natural growth of the hide, while the other is working according to 
nature. ... If you take a narrow cutting of belt leather, pull it 
well, and lay it down, you will at once observe that it naturally 
curves flesh side inwards. Nature, therefore, comes as a teacher, and 
tells us to run the flesh side next the pulley, and practice proves this 
to be correct." 

Jointing Beltn. — " Whether the belts are new or old, a properly 
made joint is of the first importance to all users of belting. ... A 
well-made butt joint, with the lace holes punched in row of diamond 
shape, answers the purpose fully as well as any. Care should be 
taken that the holes do not come in line across the belt. A good lace, 
properly applied, with all the strands of the lace running lengthwise 
of the driving side of the belt, will last a long time and costs little. If 
a lap joint is made, time should be taken to thin down the ends of the 
lap. Joints of this sort should be made to the curve of the smallest 
pulley over which the belt has to work." 

Accumulation of Lumps on Pulleys and Belts. — '* Dust should never be 
allowed to gather into a cake either on puUoy or belt, for if so, the 
fibre of the leather geta very much strained. The belt is prevented 
from doing its work becau.se this stranger defies the attempts made by 
the belt to get a pro]>er hold of the ptilley." 

Belts and Ropes coming off Pulleys. — ** When a bearing gets heated, 
the shaft naturally becomes heavy to turn. The belts or ropes, having 
already the maximum of power in hand they are designed to cope 
with, refuse this extra strain, and will leave the pulleys at once, 
or break. This accident directs the attention of those in charge 
to the belts or ropes, when time is taken up in consulting as to what is 
to be done. Meanwhile the cause of all the trouble gets time to cool, 
and the source of annoyance is never discovered. Before a new start 
is made, all bearings are well lubricated. All goes smoothly, yet 
some one is blamed for the break down." 

The aboTO hints, coming as they do from an experienced manu- 
facturer of leather, who is also an extensive user of belting, should be 



PBICB8 OF SMALL HTNAMOS. 6 1 

valuable to those who, though oonstantly using diiyiiig belts, may 
be unacquainted with the principles of their action. 

To Start tlM l>yiuuiiO. — All that is necessary is to run up the 
speed of the engine, see that the brashes of the dynamo are up, and 
the switches open, then throw over the belt from ihe loose to the fixed 
pulley, and when the machine is running adjust the lubricators to 
give about three or four drops of oil per minute, or if the lubricators 
ar<^ not sight-feed, but have worsteds or other adjustments, see that 
these are properly set ; then, having noticed that the machine is running 
in the correct direction, which may be done by touching the conmiutator 
with the finger tip, put down the brushes, and when the machine has 
excited, and the outside circuit is ready, close the switches and the 
current can then be adjusted to its correct value, cither by means of a 
regulating resiitanco in series with the^machine and the plating baths, 
or by means of what is occasionally convenient, a regulating resistance 
or rheostat in the shunt windings of the dynamo, or by both of these 
devices. 

To Stop tb« Dynamo. — ^The main switch is first opened, the belt 
is then thrown on to the loose pulley by the belt fork, and the brushes 
are nused, and the lubricators stopped running. The brushes should 
always be raised before the machine comes to rest, but not while run- 
ning full speed. 

Frle«s of Small Bynamos. — Small dynamos for electro-plating 
can be obtained for as ]ow a prico as about £io, up to very large 
prices for machines of large output. In order to give some rough idea 
of the prices at which the smallest machines may be purchased, the 
following details are g^ven of machines listed by the General Electric 
Company, Ltd., 69, Queen Victoria Street, London, E.G., iu 1895. 
Prices are probably somewhat higher now (1901). One of these 
machines is shown in Fig. 41. 

Catalogue No. , 
Current in amperes . . 
E. M. F. in volts 
Diameter of pulley in inches 
Width of pulley face in inches . 
Approx. revs, per minute . 
Approx. brake-horse-power 
at full load • 

Price • • . . 

The prices of small dynamos, with suitable direct current motors for 
driving them on the same shaft. Fig. 44, or, as they are called, motor- 
dynamos, which are listed by the same firau in an 1899 ^^f *"^ ^ 
follows : — 



200 


aoz 


202 


203 204 205 


32 


56 


72 


96 96 280 


5 


6 


6 


6 10 10 


3 


3 


3 


446 


2 


2 


2 


2i 3 4 


2,400 


1,400 


1,200 


1,200 1,000 750 


i 


i 


i 


li ih 5 


£8 


£1^ 


£19 


£24 £ZO ;f 40 



THEBUOPILEB, 

Pbihabieb woumd wob ioo, 115, and 230 Volts. 

pill in EffldeaOf Piioe. Oier-aL] dimnuli 



375 50 36 10 o 

Ancther form of iiiotor-dytuuuo, known 



Fig. 44—1 H.P. Motor-Dynamo. 



which tlir motor and dyniuno wiudiiigrH )i: 
TiiT.Tiii.ji- in H Hing-le fi^U, Fig. 45, ie, lis(«d ul 



500 62 43 o o 20 X 15 X 1+ 

Tho voitape obtained from thiw nKitor-ityiiamos nr iliTiiiniodmi (iiB 
tboiw in which tliore in a fominon field -niiitruct to tlip motor and 
Uie dynamo armnture ore Homttinii'H called) can W made of any 1 alue 
detdred by the purchaser for hpeciol plating work. The dyuamotor it. 
not BO mutable for electro-plating work an the motor-dynamo, becauae 
the voltatre from the djTiamo nidi" cannot be fo cheaply 'md readiJy 



FRIDES OP SHALL DYtUMOa, 63 

rc)pUated as is the cane with the motor-dynamo. In parrJiaHing a. 
machino of thi" type it is important to obtain pm'ino details before- 
hand of the voltB takpn by the motor, and the volts delivered by the 
dynamo portion. Also the Tariation in the vult«(te of the dynamo 
portion from ^ro load right up to tlie full loud rurrent (whtph muHt 



1 H.P. Dynunotor. For Electro-plating. 



1. Maximimi current required from dyniuno Armature. 

2. Voltagt; required. 

3. Voltaf^e of circuit from which tlie motor portion of tlie machine 

4. Distance of point at which motor-dynamo in to be installed 
from the point where power supply leada enter the building 
(approximately). 

5. Work which the dynamo is to be employed for, t.g., plating, 
metal refinio^, cte. 

The motor-dynamo is not to Hpark either on the motor or the 
dynamo side under any toad up to full load when once the bmahee are 
properly adjusted. Th<- dynamo ride must be shuni woimd. 



64 THEBMOPILKS, DYNAMOS, ETC. 

The manufaoturer shoiilcl be required to give the following details : — 

1. Normal speed at specified voltage of power supply circuit. 

2. Normal dynamo voltage at specified normal speed at zero load. 

3. Normal dynamo voltage, motor being run off specified power 
supply voltage, when the dynamo is loaded to specified full load. 

4. Normal full load current on motor at specified power supply 
voltage. 

5. Normal full load current from dynamo when run at normal 
specified speed. 

6. Temperature rise of field-magnets and also of the armature 
or armatures after the machine has been running at full load for 
six hours. 

7. Price of motor-dynamo or dynamotor delivered and installed in 
purchaser's premises, the price to include starting-gear, switch, 
and safety cut-outs on the motor side. Full details of the 
starting apparatus, main switch, and safety cut-outs, if any, 
which are included, must be given. 

8. State if it is possible to regulate the voltage of the dynamo 
output, and if so, between what limits ; also state whether the 
apparatus necessary for this voltage regxdation is included in 
the price given imder (7), and if not, give the price for this 
reg^ulator installed complete, separately. 

Other things being equal that motor-dynamo or dynamotor is the 
most satisfactory which : — 

1 . Takes the smallest current at full load from the supply main at 
the specified power supply voltage. 

2. Gives out the largest current from the dynamo side at the 
specified plating voltage. 

3. Has the smallest variation of volts on the dynamo side as the 
load is altered from zero to full load. 

4. Has the smallest temperature rise under the conditions stated 
above. 

5. Kuns at the lowest speed. 

It is desirable that the bearings shall all be fitted with automatic 
xing lubricators with oil level sight tubes, or in any case sight feed 
lubricators shoidd be employed. 

It is also very desirable that the motor side of the machine shall be 
fitted with a double pole switch, a starting switch, double pole fuses, 
and also an automatic zero current cut-out. A very convenient and 
largely used form of switch, which combines a starting switch and a zero 
current automatic cut-out, is manufactured and sold by the Sturtevant 
Engineering Company, Limited, of 75, Queen Viotoria Street, London^ 
which is known as the Cutler-Hammer Plain Motor- starting Xtheostat, 



PRICES OP SHALL DYHAUOB. 65 

with autumaliu ztTurjiuTentreleaHe, Figs, 46 and 47. It u made Ht a pnue 
frura £1 lOb. fur } B. H. P. mototn: £2 for ij to i B, H, P. motora; 
£i ion, for u 3 B. U. P. motor ; ^4 for u 5 B. H. P. motor, up to 
£l(> for H 50 B. H. P. motor. 

It in, in the writcr'i upiniou, quite ueHeDliul thut motoru iihalt be fur- 
nished with the luifoty and Bturtlug gear spccitied above, if trouble with 
thp motor or the Kupjily mains is to be avoided. The whole cost of the 
double pole switch, double pole fuse holder uiid fuHee, and incltidiiig 
Uie HtartoDg switch and automatic mH)(iii:tic zero rurreut output 



Fig. 46.— Motor-st»rting Switch. 

mentioDed above, should not cost more than £2 15s. for a ij to 2 
B, H. P. motor, not including the coat of fliting. Fur a motor of 
about J to 1 B. H, P., the coat will be about ids. less. 

Having now TODiddered the various available aourccH of the elwtrit 
corrent with oh full detail as the liuiilo of this treatise pennite, we 
must turn to the queaUoD of the most auitable aouree to selt-rt under 
given conditions of work, Blvrays bearing in mind the important 
questions of prime cost, depreciation, maintenance, and coat of energy 
per given output of the olectiio generator. 



66 



THERMOPILES, DYNAMOS, ETC. 



By the cost of energy wo therefore include the cost of attendance 
together with the cont of the chemicals consumed in a battery, the 
cost of the gaA or fuel burnt in a thermopile, and the cost of gas 
burnt in a gas-engine, oil in an oil-engine, or coal or other fuel under 
the boiler supplying a steam-engine; or li^stly the cost at which 
electrical energy can be obtained from some source of electric supply. 
This source t)f electric supply is usually the public electric power or 
lightiug supply mains, but may also include electric power obtained from 
a neighbouring premises or the electric power obtained in a charged 



D.P. 



H 



iV V 







11 I 



'III ■; 

D.P. jj ' 
Switch ' 



yooo^ 



I 










Fig. 47.— Diagram of Connections of Motor-starting Switch. 

secondary battery supplied from some neighbouring generator. The 
possibility of obtaining power from either water or wind turbines is at 
present so limited (and to all appearances will remain ho) that these 
sources of energy will not be considered in any detail here. 

Bleetrlc Oeneratora fbr Small Outputs. — In any particular case 
where it is proposed to set up some foiin of clwtric generator for a 
small amount of electric current for electro -plating or other small 
electro -metallurgical operations, tiio cinamihtjincos under whic^h the 
installation is to be made ai-e, of course, definitely known, and there 



ELBGTBIO GKNEBATORS FOB SHALL OUTPUTS. 



67 



must be aome definite Holution of the qaetstion aa to what particnlar 
generator to inHtal. In giving general advice, however, it i^ difficult 
to conHider every poHidble condition which may ariae in practice, and it 
huM therefore been thought wiue to seleot some few definite cuvea under 
definite stated conditions, and give the Holutions for these, which, in 
tho writer's opinion, appear most satisfactory, leaving to the reader 
the Uuik of applying one or other or a combination of any of these 
solutions to his own case. 

It must be borne in mind, that throughout this book the prices of 
apparatus which are g^ven are only stated iu order that some idea of 
tho nature of the outlay involved in a g^veu installation may be 
obtained. Prices vary from year to year, and a correct estimate 
can only be made after having obtained a tender to a definite specifi- 
cation. The prices given here, however, are always taken from some 
stated list. 

Case I, — No power, either electrical or mechanical, is available, and 
it is not possible to get secondary batteries charged in the neighbour- 
hood. Under these circumstances it is probably advisable to employ 
the ** Cupron " element up to a current output as large as 20 amperes 
at 5 volts, which will cost probably about £24 los., or if the work is 
not very steady in character, but is required a good deal at one time, 
with periods of littie or no work intervening, it is probably wiiie to 
use the '^Cupron*' element for currents up to as high as even 30 
amperes at 5 volts. The former battery, costing £24 los., may be still 
used for this current, as the normal current output of such a battery 
is 24 ampdres, and the maximum which may be used is 48 amperes, 
although it is advisable to run the battery with currents as near the 
normal as jKHssible, if it is desired to obtain the largest ampere-hour 
efficiency. If the current required is larger than 30 amperes, then 
either a small steam-engine, boiler and dynamo, or a gas-engine and 
dynamo should be purchased. There is not much difference in the 
prime cost of such a combination for small powers, but the room 
rec^uired and also the small attention needed make it desirable to pur- 
chase the gas-engine combination. The total cost f. o. r. of the 
dynamo yielding 32 amperes at 5 volts, is listed by the Greneral Elec- 
tric Company, in 1895, at £8 (see p. 61), and the gas-engines may be 
purchased for the following prices, taken from the Stockport Gas- 
Engine List of 1 9C». 



Brake-horse-power. 


I) 


2i 

• 


2i 

£ 8. 

50 


4 

£ & 
58 10 


1 4^ 

£ 8. 

, 68 


i 1 
, Price . 


£ 8. 

36 10 


£ 8. 

42 



68 



THBBMOPILES, DYNAMOS, ETC. 



The cost of the necetisary water- tanks is included in these prioes. As 
thena machines are fitted for constant speed for electric lighting with two 
fly-wheels, it is probable that cheaper eng^es might be purchased. The 
difference would not, however, be much. The prioes alHO include, 
standard-size pulley, patent anti-pulsating gas bag, exhaust boxes 
and the usual set of spares with spanners. These engines are made 
by J. E. H. Andrew & Co., of Beddish, near Stockport. Agas- 
ougiue dynamo plant therefore, to yield 32 ampdres at 5 volts, can be 
purchased for about £44 lOs., exclusive of erecting, and one to yield 
56 ampdres at 5 volts for £52 los., exclusive of erecting. The cost 
of the *'Cupron" element for various current output is worked out 
in the following table : — 



Volts. 



5 
5 
5 
5 
5 
5 





Cuxrent. 




1 

normal 


8 


maximum 16 




16 




» 32 




32 




» 64 




40 




» 80 




48 




„ 96 




56 




„ 112 



Price 


• 


£ 


8. 


d. 


8 


2 





z6 


4 





32 


8 





40 


10 





48 


12 





56 


14 






It must be remarked that the prices stated for the ' ' Cupron * * element, 
ius given above, arc those given on u Grerman list, and they would, 
no doubt, be more expensive delivered in England. The reason that the 
WTiter would advise a gas-engine dynamo set costing say £45, and 
cspable of yielding 32 amperes at 5 volts, rather than a " Cupron'* 
element set of cells having precisely the same normal output as the 
d>'namo, is bcn-ause the depreciation and upkeep of the *' Cupron" 
elements would be higher than is the case ^nth a properly looked after 
gds-engine and dynamo. A cheap vertical steam-engine and boiler, 
packed and f. o. r., is listed by the General Electric Company, at 
the follovring prices : — 



j 
Brake-horse-power. 


i 


I 


.4 . 

/49 ;f57 


2h 


3 


Price 


£36 


£43 


£bl 


£^2 



It is therefore evident that for very small powers the steam-engine 
has about the same oost as the gas-engine, but that as the powers in- 
crease the gas-engine ha,^ the lowt-r prime cost. For any powers up 
to about ten brako-horsc-ixjwer, the present writer cousidersi partly 



ELECTRIO OBNFR\TORS FOR SMALL OUTPUTS. 69 

for reasons already pointed out, that the ^as-cngine nm on town ga.\ 
ifl better for electro-plating factories than a steam-engine of the same 
output. 

Case II. — If, as in the last case, there is no electrical or mechanical 
power available, and no means for charging a secondary battery, and 
there is further no supply of coal-gas available, then a steam-engine 
dynamo combination with boiler may be purchased to yield 32 amp^s 
at 5 volts for about £44, and a similar combination to yield 56 amp^s 
at 5 volts for about £49, and when the current required is under about 
20 amperes for steady work, or 30 amperes for variable work, the 
'^ Gupron *' element should be employed instead of steam-dynamo 
set. 

Cftw III. — If sufficient power is available, as, for instance, from 
some engine on tlui premises which is only partially loaded, it is 
probably better to purchase a small dynamo costing, say, £8 or £10, 
when the probable quantity of current required is found to be 
greater than about 3 or 4 amperes. Remembering that such a dynamo 
will yield as much as 32 amp<^res. If a current of less than about 3 or 
4 amp^s is required it is probably best to purchase 5 No. II. 
'' Gupron '' elements, costing £2 5s., and yielding, when in series, 2 to 
4 ampdres at 5 volts. (Seep, zi.) 

Caee IV. — If an electric supply company can supply a continuoun 
current on the premises at any reasonable rate, then it is probably 
advisable to purchase a suitable motor-dynamo or dynamotor directly 
it is seen that the current required will be as larg^e as 6 amperes or so, 
for '' Gupron '' elements for this output at 5 volts would cost about 
£3 2s., whilst a dynamotor having an output of 8 amperes would cost 
about £12. Before, however, deciding to instal an electric motor, a 
clear understanding must be arrived at as to the conditions of charge 
for power imder which it will be placed. The charge is reasonably 
low, in many cases about 2d. per Board of Trade unit ; which unit, for 
a motor-driving dynamo, may be looked upon as one horse power used 
throughout one hour, or half that power used steadily for twice the 
time and so on. But in some one or two cases with which the writer 
is acquainted a very large charge is also made per annum or per 
quarter by the supply corporation for each horse-power or fraction of 
a horse-power of the motor installed. This appears to be an arrange- 
ment which must, one would imagine, have a good deal of effect in 
discouraging the use of electricity for small power units, a use which 
is generally understood to be the great object of supply companies to 
foster in order to increase their dividends. This heavy iharge per 
b. h. p. of power taken by the motor installed per annum is precisely 
the Hume whether any power is used or not, and although not iinual, 
must, where imposed, be carefully considered when deciding on the 



70 TIIKRMOPILKS, DYNAMOS* KTC. 

installation of a dynamo driven by electric power. The rare required 
to keep a motor-dynamo or dynamotor running RatiRfactonly Ia Blight, 
and the details are the same as those necessary when running a 
dynamo, described on pages 51 to 61. The cost of about £1 los., or 
perhaps less, must be added to the above price for the motor-dynamo to 
include a satisfactory arrangement of the main switch, starting switch, 
automatic zero current cut out, and fuses, as previously specified for 
any electric motor. (See p, 64.) 

Case V, — If portable secondary cells can be charged in the neigh- 
bourhood at a moderate rate then the secondary battery is cheapo in 
prime cost, and probably in depreciation, than the " Gupron ** element. 
For instance, a portable secondary battery cell, manufactured by the 
Electric Power Storage Co., of 4, Great Winchester Street, E.G., having 
a capacity of 50 ampere-hours, and giving a safe maximum discharge 
at the rate of 9 amperes at 2*2 volts, and which can, therefore, be 
kept up over 5 hours, weighs 21 lbs. complete, and costs 15s., whereas 
3 No. rV. " Gupron " elements, which give a safe diHcharge at normal 
current of 8 amp^s and 2*4 volts, can be run for about nine times 
this length of time, namely, about 45 hours, before they require the 
oopper oxide regenerating. Now each charge of the secondary 
may, perhaps, be made at is. per charge, and, consequently, the cost 
of the secondary battery and nine charges is 24s., whereas the price of 
the 3 No. IV " Gupron " elements is about £4 58. The " Gupron" 
elements can, of course, be regenerated at a small cost, but there can 
be no doubt that secondary batteries are cheaper, both in prime oost and 
up-keep, than "Gupron" element batteries if the battery-charging 
can be performed in the neighbourhood at a reasonable cost and with 
reasonable care of the cells. It must, indeed, be remembered that 
much damage may be in time done to secondary batteries by charging 
them with currents much above their specified charging currents, and 
as the batteries sent in, to anyone undertaking charging, usually vary 
much in size and the current they require, there is a good deal of 
temptation to connect them in series and charge them all with the 
same current. If the maximum current employed, however, is within 
the smallest specified current for any cell in the batch no harm will be 
done to any of the cells charged at too small a current, the only 
trouble being that they will require a longer charge. 

Below is given a table of the details and prices of the Electrical 
Power Storage Go.*s Q type portable cells, also shown in Fig. 22, froni 
their list dated 1898. 



GAS ENOINB8 BUN ON PBODUOEB OA8. 

Q Ttfu Portable Secondabt Battsribs. 
The pricefl j^ven below arc for cellfl in lead-lined wooden boxee. 



71 









Approximate 


1 


.4 




Description of 
Coll. 


Working 
Bate. 


1 


Dimenidons '^^ 
over handlen 'Z 

und ::^ 




1 


1 




^5 


terminals. 


2 


Zi 




1 




>.§ 




^ 


eC 1 I*rioe. 1 






s 






Weight CO 
A 




Number Number of 
of negntive 
1 Cells. Plata's. 


Charge 
Ampiires 


uximum 
soharge 
mperes. 


P Length. 
? Width. 


leight. 


eight in 
lbs. 




* 


f:&< 




1 


1 


1 








1118. 


lbs. 


s. d. 


3 Q Plates 


•5 to 13 


1'3 


7 


2 1 5t 


9i ! -9 


6 


6 6! 


5 » 


I „ 2-6 


2-6 


14 


2i 1 58 


9J 1 1*5 


8 


8 


Single . 7 „ 


2„ 4 


4 


21 


3i ! 58 


9i 1 2-2 


loi 


9 6, 


C6118. 


II n 


4 » 6-5' 65 


35 


5 ; 58 


9i ; 3*4 


16 


12 9 ; 




15 » 


7» 9 


9 


50 1 


68 58 


9* ' 4-5 


21 


15 3 




21 „ 


10 „ 13 


13 


70 ; 


9 58 


93 6-5 


28 


19 0; 



Gate VI. — Supposing that both mechanical power and electrical 
power are available. Then for small currents up to about 10 amp^reb 
the **Cupron" element may be employed, or if cheap secondary 
battery charging is available, secondary batteries may be conveniently 
used probably up to as much as 40 or 50 ampdres, but above this 
amount there is no doubt but that a motor generator costing JS36 los. 
and yielding 75 amperes at 5 volts is the best thing to invest in, for 
the up-keep and depreciation of a motor generator is very small and 
the power used cheap, whilst the up-keep and depreciation of secondary 
batteries is about 20 pei: cent, on their prime cost per annum, whilst 
power obtained by external charging is always expensive. 

The foregoing discussions of several definite cases are, however, 
incomplete, for they do not and cannot take account of several factors 
which must always be considered when deciding the best course 
to pursue. For instance, a very essential point in commencing a 
business may be to keep the capital outlay small, and again, the 
knowledge as to whether a given output is likely to remain steady 
or to increase, or whether the business, although averaging a 
steady output during the year, is likely to vary very mu(*.h 
from time to time during that year, are all points with many 
others to which due weight must be given. It is, how- 
ever, to be hoped that the cases treated of and the information as to 
prices g^veh may prove of assistance in guiding an intending 
purchaser of electric generators. 

on Vrodnc«r CHui. — ^Nothing has been sairl 



72 



THERMOPILES, DYNAMOS, KTO. 



hitherto of the use of gas-engmes run on prodnoer gas, and for thin 
reason, it is not, in the writer^ s opinion, an economical plan to fit a 
gas-engine with a gas pToducer plant unless the output of the engine 
is well over 20 h. h. p., and, therefore, although producer gas is an 
enormous saving for plants of larger output it is not suited to the 
small plants we have hitherto considered. 

Oil BnffliMS. — Oil eng^es are considerahly mor» expensive than 
either gas or steam cng^es of equal output, and they cannot, therefore, 
compete with these generators unless coal gas is not to be had and one 
or more of the following conditions exist : — 

1. Coal is very dear, or there is no facility for its delivery and 
storage. 

2. Space is of great importance. 

3. A boiler and boiler-furnace and flue are, for any reason, 
objectionable. 

As it is possible that such cases may arise, the following prices may 
prove of use. 



Brake horse-power 


i& 


2j 


3l 


5 


6J 


Price, including 
water vessel 


£ 6. 

80 15 


£ fl. 

93 10 


£ fi. 
107 5 


£ H. 

129 


£ s. 
145 



The above prices do not include connections to water vessel, founda- 
tion bolts, piping to silencer, nor pulley. 

The cost of fuel for these engines is stated to be under one half- 
penny per brake horse-power hour. These prices are given in the 
General Electric Co.*s list for 1895, but apply, probably, to Tangye's 
or Prientman's oil engines. The price of either make is about the 
same. 

Adyantages of Portable Cells. — Primary and portable secondary 
battery cells have two distinct advantages over dynamos, and these 
are : — 

1 . Tlicy can be brought close to the work It is intended to treat, 
thus saving long leads. ^ 

2. They can be combined by connecting either in parallel or series 
so that the output from them may be varied considerably with 
regard to the volts in circuit, which is sometimes useful for 
diffcTcnt kinds of work. 

These advantages are, however, not very marked unless the work is 
of an iiTogiilar character. Moreover, the variation of the voltage of 
the d\aiaino may be secured either by a shimt field regulating rheostat, 



mSGULATINO BBBI8TAV0ES. 73 

or by meanfi of a regfulating^ Tenstanoe introdnoed into tbe oircnit in 
■eries witK the plating Tat and the dynamo. 

aagwlating BaatstaneM. — When nrang a dynamo or batteriea for 
electro-plating, It is frequently necesRary to vary the current employed, 
whiliit the e. m. f. of the current generator is constant. Thus, 
supposmg that we have a dynamo driyen by a gas engine whose speed 
we cannot alter appreciably and that work is in course of being put into 
the plating yats, it is dear that the work first put in nuty have a very 
much larger number of amperes per square foot than will be the cafie 
with the work which is put in last, it may, therefore, be desirable to 
somewhat reduce the current on the work first put in the bath, and this 
may be done ^y means of an adjustable resistance placed in circuit with 
the leads running from the dynamo to the bath. Again, the work plated 
by the same d3mamo may be of quite a different type on different days, 
R&yer at one time, gold at another, or sometimes alkaline and some- 
times acid copper baths and sometimes nickel, or it may happen that a 
sihrer, a copper, and a nickel plating yat may all be taking current 
from the same dynamo at the same time. Under each of these 
conditions the e. m. f. required and the current density will be different, 
but if the dynamo has been purchased to yield the highest electrical 
pressure required, any lower pressure at the terminals of the plating-yat, 
and any desired current may be obtained at will by placing a suitable 
regulating resistance in circuit as described. What has been said 
about the reg^ation of dynamos applies equally to electric batteries, 
except that the batteries may be employed, so to speak, to bmld up any 
desiiede. m. f. by connecting them suitably in either parallel or series ; 
notwithstanding the facility which batteries offer in this respect, it is, 
neyeriheless, most desirable that the flexible method of controlling the 
current, which is afforded by the use of a reg^ating resistance, should 
be employed if the best results are to be obtained. 

An electro-plating plant, therefore, should be supplied with 
generators capable of yielding an e. m. f. and a current equal to the 
greatest calls which are to be made upon the establishment, but to 
properly manipulate these quantities in order to get the best results 
under ^e yarying conditions of solution, nature of deposited metal, 
nature of surface upon which deposit is to be made, and the amount 
of cathode surface at any time in the plating yats, it is most desirable 
(eVen when, as should always be the case, a shunt regulator is supplied 
with the dynamo) that some current-regulating deyioe should be pro- 
vided. One of the most generally useful of these is the carbon plate 
resistance. It is shown in Fig. 48, and consists of a series of carbon 
plates, 0, in an insulated support, fitted with a screw h, at one end. 
The current passes through the carbon plates in series, and the resistance 
of the pile yaries with the pressure with which the plates are squeezed 



74 THEBMOPILKS, DTKAUOS, RtO. 

togethcT, Mid this if vnripd liy mf nns of tho \anc hnnd sfrcw at one 
end of tlw n{ipiinitiiH. The uuxt of rnich a n-ftulntiMi' cnrlHiu ri'M^tiuuv 
depeiuU, of i«un<e, npon itH nae, Oue which will take s" amp^iT'ii 
continuoiwly without hesHiig to rednew in made by Measru. Parfitt & 
Webber, of Denmark Street. Brintol, for a priro of £t. It coatainn 
50 carbuD iitatfM, each ahout ] ins. square and il-in. thick. TheH> are 
inualaled fnim the iron riidH at Uio xidm and botlimi by mcaiiH of thick 
shn'tM of ai<lH''>ti>H inillboard, a. Similar iwheHtoti Hheeln proti^^ the east 
iron oiiJ.p]Bti« from cominfC into ooutaet with the carboim or the gim 
metal teiminal plates, B b. To these ptatee the termiimls are screwed. 
There»d»tanceof such a carbon plate resistance may always be halved 
or reduced to any value, at a given taghtncRn of the carbon plftte«. 
Iiy means of a simple device — namely, by taking nut the trun-met^l 
terminal plate and insertinif it between the carbons at any other point 
than the extreme end of the pile where its normal position is. The 
resistance, therefore, of this apparatus may be reduced from that of 
tiie whole pile of carbon plates loosely pressed tOKCther down to that 
of one earbon plate only, tightly clipped between the two end or 



Pig. 48.— Adjiintable Carbon Plate Ile«lEt«nc& 

terminal metal plates of the apparatus. There is DO harm whatever 
to be feared from running such a carbon resistance with a current so 
InrRC and for so loiijf a time that the carbon plates are at a dull ml 
heiit, provkleil that thi> rcwi-tance is Axeii in such a )xisition tlmt there 
is no danxiT of tiro l>ein^ caused by it. If it is atood on sheet iron 
whii^h is supported on bricks, there can be no danger at all on this 
n'munt. even if the brii'ks rest upon wood. 

Another form of carbon resistauce whlcli is a good deal cheaper than 
the one last described is made of electric light carbons, and is shown in 
Fig. 49. It fulfils thc^ eondittonn that sueh a rcaiatance for electro- 
plating requires, namely, Uiat it is cheap, strong, of considerable range 
of adjustment, and not easily damaged by moisturo and fumes. It 
consislH of a fixed rack, A, and a movable rack, B, both of east iron. 
The movable rack b, can be moved nearer to or farther from a, and 
can be clamped in any position on the board c, by means of a clamping 
Borew, not shown in the figure, which passes through the hole n in 
the metal projeution at the right hand side of B. This screw eiortfl 



SEnttl^TINO BKSISTAHCKB. 75 

pn<«i<nrp on thi- strip of tin, e, which is let into the bonrd, but dots 
not iDinc uenrrr than uboiit 2 to 3 inchMi from the rnrJi a. The deprFH- 
MODi' ]□ tht? rack, the mimber of whii^h may be us luxe an ix deidrcd, hut 
which the writer finds may he ctmTBDiently two, ure made of a corvpd 
outline, and ore meant to take ordinary electrii^ ''Kht carbons of from 
to to 15 millimetreH diameter. A good i-ontnit between thrxc carboDH 
und tho metal racks U ubtainid by meunH of two ciut iron slumping 
bare, r f, only one of which is iihown in tho litfure, tbeec ore about 
one inch wide. To clamp the c«rbonii iioQealGd. copper Htrips, one 
inch wide, Ath of an inch thick, with holes H.t the ends, arc slipped on 
the J inch stud Borewn a o q o, the carbons are then laid in iwfdtion 
over thcw strips, and two more similar strips of copper arr pliussl over 
them. Tho clamps are finally placed in position, and are screwed 
down with suffidont pressure by buiterfly nuts, screwing on to the 



fig- 49.— AdjuBtaue i;aTt>on Koa iiesisuuice. 
stud screws. The length of all the copper Btrips between the holes in 
theae ends is leea than the distance measured along the curved surface 
of the iron racks and damps, and hence these copper strips are 
polled into tight contact with the carbon rods when the butterfly nuts 
an screwed down. The terminals of the resistance are at n R. Tho 
resistance may be either employed horizontally as shown, or may be 
hung on the wall by mirror pUtes or boots at e i. This redstani* is 
abw made by Mewrs. Parfltt and Webber, of Denmark Street, Brintol. 
One with four carbons costs 158. complete, whilst two, with two 
carbons each, would cost about lis. or i:?s. each. The four-carbon 
form* gives a range tmrn one carbon a foot long as the highest resia- 

* The resistance ol an electric light carbon, having a diameter of 
about 14 m.m. and not soft cored. I have fonnd to be about 01-12 ohms 
per foot length when carrying a current of 80 ampi'res in air. The 
temperatnre of the carbon under these oonditiani waa just sufficiently 
high to blacken paper pressed against it. — A. P. 



•j6 IHRBHOITLRa, DVN4MOH, ETC. 

UiDro clown tn fonr in pnrnllcl, which may he fihorb^f^ up by nhiftfai^ 
thn rw'k n (o n length of not more that about 4 inchcFi. The two 
double-carbon form given, however, double thin range, i.e., from u 
n resifltaiicc of two foot long ™rbon» in Beriei' down to the 
name value for low resis- 
tanre na the four-oarbon 
form. The pricee given 
above for these reMix- 
taoces include (Jiilo 
boards, which in thnl 
caxe do not reqiiiro tli<' 
strip of tin E, wbich in 
intended to protect tlie 
wood from the end of Uic 
«iTcw. Each carbon will 
carry about 30 nmpcre« 
without becoming wiffi- 
cienlly hot to get light to 

A variable liquid re- 
tdxlance, sold hy the 
General Electric Com- 
pany, of bi). Queen Vic- 
toria Street, ifl nhown iu 
Fig. SO. It is knovfn an 
Lyons' Variable Licjuid 
Kesistance, it will carry 
from 50 to 80 amp^n'fl. 
It connistn of a utoui- 
ware jar 24 iucheti high 
ond 8 inches in dianiet«T. 
Each jar U in a framr'- 
work, to which is at- 
i taohedaraicingorlowiT- 
ing gear tor the purpo*- 

lead in the po-ealled nou- 
nacctie liquid of secret 
Fig. 50— Lyons' Variable 1.i.|UidRcsistauee, coniimsit ion, probably 11 
solution of some neutral 
salt. The price of the cheapest of these resititauccs is high, luring over 
£6. Cheap adjuBtablc liquid resistani^'S can, however, 1» rigfred up 
on a somewhat dimilar prineiplc for temporary purposes by means 
of a larste jam jar and a couple of lead plalus in sodium aiilpbalp 
solution. 



I 



DETBSMINATION OF THE POUSITT OP OBNERATOBS. 77 

Adjiwtable wire naflnUnce*. Bold by MesBrB. 0. Berend & Co., of 

Dunediu Uuiue, Btuiag-liall Avenue, LoniloD, are shawo iu Figs ci 

iiud 52. These rew»t- 

iim.'OB CO j| from [6 to 19 

"hillingH each in tJio 

form of Fig. $1, tsrry- 

iiig a ciinvnt uf fruni 
I to 15 umpi^ruH : wbilnt 

roMiBtuuiMM of the form 

i>howD in Fig 52, io 

whivhthei-lepfiHrcDot HO 

gradual BH iu llie laoBt- 

anccB KhoHTi iu Fig:. 51, 

the price v&ries&om 25 to 

to 45 Hhilliuffs, accardiug 

to nize, the turront uar- Fig. 51.— Adj "-.table Wire Keeistauce. 

ried varying alMi from 

4 amporcH in the analleiit to 10 lunpfrcs in the largest size. 

BttarmlnatlttD of Uu 
VoUzltT ol a«iMntan.— It 
ig not infreqaently neceasary to 
aacertain the polarity of a 
dynamo, or even a buttery, and 
this may lie done, in the i-aao 
of a dynamo, either bypaKtiog 
a current from it through a 
BolutioD of one part of Btron^^t 
Bulphimc: mid and throe parte of 
water coiitsiued in au ordinary 
jam jar from temiinalH of lead 
scraped briglit. The greatcat 
cue must be obecrved, at leiwt 
in testing taiger mauhines in 
this way, to preveut the two 
lead strips coming into con- 
tact. They may be conve- 
niently kept at a distance of 
about three inches from one 
another. The lead strip at- 
taohed to the positive pole of 
the dynflino will become of a 
dark brown or chocolate colour 
in about 5 to 10 minutes. A quicker test, which may be used with 
either bnfterleB or dyimmoH. ih to employ pole finding paper made with 
phcnolphtlialein. This paper is white, but if it in moistened and laid 



jS THERHOPILBS, CVNUIOS, GTO. 

oil II tablt, und the two wires from the tennimUB of the dyoamo or 
biitltiry are pressed upon it at b diatance of nn inch from euth otlier, 
u deep crimson HUin will be ehown uoder the negative wire. Thin 
iii'tion tiilies place ut ouce. Such polo papera may be piinJuued at 
u cheap rate made up into little books. 

OOTMrml ArruxsaoMat of natlns V»tm.— Fig. 52* given a 
Kfoeral pentpective view of two vnU in h plating hhop, ummgcd in 
parallel, with their amp^ra-moten and regulating re ~ 



Fig. 52A.— General Arrangemeut ol Electro, pla ling Vitn 

and a shaft along the aide of each vat which, by means of ecMientnca, 
moves an oscillating frame, cauaiog the work to conatanlly keep in 
gentle movenient, a movement which iw found to be very coodiuive lu 
uniform platin(( dejioiutB. L are tlio anode rodB and c Ihi- nithortiw. 
It need hardly be said that those vain are intended for niekel, mpppr 
or Mlver plating, but not for gold work, which is done in much smaller 
vals. uBually of »tonowaie or china. A somewhat ttituilur 1 icw Ik 
lihown in Pig. loS. 



CHAPTER 111. 

HISTORICAL REVIEW OF ELECTRO-DEPOSITION. 

Auiiuuiicenieiit uf Jacubi's Dbcovery.—* Jordan's Process Published. — Jordan's 
Prucetu.— Spencer's Paper on the ElectroU'pe Process.— Effect of 
Spencer's Paper. — Vindication of Jordan's Claim. — ^Mr. Dircks on 
Jordan's Discovery. — Sir Henry Bessemer's Experiments.— Dr. Golding 
Bird's Experiments. — ^Origin of the Porous Cell. 

Long before the art of Electro-deposition was founded upon a prac- 
tical basis, it was weU known, experimentally, that several metals 
could be deposited from their solutions upon other metals, by simply 
immersing^ them in such solutions ; but this knowledge was of little 
importance beyond the interesting' nature of the results obtained. The 
schoolboy had been accustomed to amuse himself by producing the 
ever-popular *' lead tree," by suspending a piece of zinc attached to a 
copper- wire in a solution of sugar of lead, or the " silver tree," with 
a solution of nitrate of silver and mercury ; or he would coat the blade 
of his penknife with copper, by dipping it for a moment in a weak 
solution of sulphate of copper (bluestone). But these, and the Uke 
interesting facts, were of no practical value in the arts. It was also 
known that articles of steel could be gilt by simple immersion in a 
dilute solution of chloride of gold (that is g^ld dissolved in aqua regia), 
or still better, in an ethereal solution of the chloride, and Uiis simple 
process was sometimes adopted in the ornamentation of engraved 
articles, in imitation of the process of datnateming. The eyes of needles 
were also gilt by a similar process, and ** golden-eyed needles" became 
popular amongst the fair sex. With this exception, however, the 
deposition of metals, even by simple immersion in metallic solutions, 
was regarded as interesting and wonderful, but nothing more. 

As far back as about the year 1820, the author's father covered the 
'* barrels " of quill pens with silver, by first steeping them in a solution 
of nitrate of silver, and afterwards reducing the metal to the metallic 
state in bottles charged with hydrogen gas, the object being to protect 
the quills from the softening influence of the ink. 

In the year 1836, Professor Daniell made known his constant battery y 
and in the same year, Mr. Do la Rue conHtruct^Hl a modification of this 
battexy, in working which he observed that ** the copper-plate is also 



8o mSTOBIOAL REVIEW OF ELEOIBO-DEPOBITION. 

oovered with a coating of metallic copper which is continually being 
deposited ; and so perfect is the sheet of copper thus formed, that, 
being stripped off, it has the counterpart of every scratch of the plate 
on which it is deposited.* Although this interesting observation did 
not lead to any direct application at the time, it is but reasonable to 
presume that in. the minds of some persons the important fact which 
it disclosed would have sugg^ested the possibility of its being suscep- 
tible of some practical application. It was not until the following 
year (1837), however, that the dectro-deposition of metals, experi- 
mentally, seriously occupied the attention of persons devoted to 
research, the first of whom was Dr. Golding Bird, who decomposed 
solutions of the chlorides of ammonium, potassium, and sodium, and 
succeeded in depositing these metals upon a negative electrode of 
mcrcury,t whereby he obtained their amalg^ams. From the time 
when his interesting results became known, many persons repeated 
his experiments, while others turned their attention to electrolysis as 
a new subject of investigation, and pursued it with different objects, 
as will be shown hereafter. 

Mr. G. R. Elkington, in 1836, obtained a patent for *< Gilding cop- 
per, brass, and other metals " by immersing the articles in a boiling 
alkaline solution containing dissolved gold. This was followed, in 
1837, by several other patents granted to Mr. H. Elkington for coat- 
ing metals with gold and platinum, and for gilding and silvering 
articles. In i8j8, Mr. G. R. Elkington, with Mr. O. W. Barratt, 
patented a process for coating articles of copper and brass with zinc, 
by means of an electric current g^erated by a piece of zinc attached 
to the articles by a wire, and immersing them in a boiling neutral 
solution of chloride of zinc. This was the first process in which a 
separate metal was employed in electro-deposition. 

AnnonnoOTmint of Jaoobi's Diocovcry. — ^About the period at 
which the above processes were being developed, it appears that 
several other persons were engaged in experiments of an entirely 
different character and of far greater importance, as wiU be seen by 
the results which foUowed their labours. In St. Petersburg, Pro- 
fessor Jacobi had been experimenting in the deposition of copper upon 
engraved copper-plates, a notice of which appeared in the Athenaunij 
May 4th, 1839. The i>aragraph ran as follows; — *' Galvanic Efigraving 
in Relief, — ^While M. Daguerre and Mr. Fox Talbot have been dip- 
ping their pencils in the solar spectrum, { and astonishing us with their 

* Philosophical Magazine, 1836. 

t ** Philosophical Transactions of the Royal Society," 1837. 
1 1 1 was about this period that the famous Daguerreotype proctti of portrait- 
taking was being developed in England. 



Jordan's process. 8x 

inyentiona [photograpluc], it appears that Profefwor Jacobi, at St. 
PeteTBburg, has abo made a discovery which promisefl to be of little 
less importance to the arts. He has found a method — if we under- 
stand our informant rightly — of conTerting any line, however fine, 
engraved on copper, into a relief by galvanic process. The Kmperor of 
Russia has placed at the professor's disposal funds to enable him to 
complete his discovery." 

Jordan's Froesas Fnbllalisd. — Having seen a copy of the above 
paragraph inike Mcehanic^s Magazincy May nth, 1839, Mr. J. C. 
Jordan, of London, eleven days afterwards sent a communication to 
the editor of that journal, in which he put in his daim — if not to 
priority, as far as Jacobi was concerned, at least to prove that ho had 
been experimenting in electro-dei)08ition some twelve months before 
the announcement of Jacobi's discovery was published in this coimtry . 
Indeed, Jordan's communication did more, for it contained a definite 
procesSf and since this was undoubtedly the first publication of the 
kind which had appeared in England, the merit of originality — so far 
as publication goes — is clearly due to Jordan. As an important item 
in the history of electro-deposition, we give the subjoined extract 
from his letter from ihe Mechanic* a Magazine^ June 8th, 1839. The 
letter was headed ^' Engraving by Gkdvanism." 

Jordan's ProcsM. — '^ It is well known to experimentalists on the 
chemical action of voltaic electricity that solutions of several metallic 
salts are decomposed by its agency and the metal procured in a free 
state. Such results are very conspicuous with copper salts, which 
metal may be obtained from its sulphate (blue vitriol) by simply im- 
mersing the poles of a galvanic battery in its solution, the negative 
wire becoming gradually coated with copper. This phenomenon of 
metallic reduction is an essential feature in the action of suataining 
batteries, the effect in this case taking place on more extensive sur- 
faces. But the form of voltaic apparatus which exhibits this result in 
the most interesting manner, and relates more immediately to the sub- 
ject of the present communication, maybe thus described : — It consists 
of a glass tube closed at one extremity witli a plug of plaster of Paris, 
and nearly filled with a solution of sulphate of copper. This tube and 
its contents are immersed in a solution of common salt. A plate 
of copper is placed in the first solution, and is connected by means of 
a wire and solder with a zinc plate, which dips into the latter. A 
slow electric action is thus established through the pores of the plaster 
which it is not necessary to mention here, the result of which is the 
precipitation of minutely -crystallised copper on the plate of that metal 
in a state of greater or less malleability, according to the slowness or 
rapidity with which it is deposited. In some experiments of thif- 
nature, on removing the oopi)6r thus formed, I remarked that the sur- 



8a HISTORICAL REVIEW OF ELECTRO-DE POSITION. 

face m contact with the plate equalled the latter in Rmoothnesi 
and polish, and mentioned this fact to some individuals of my 
acquaintance. It occurred to me therefore, that if the surface of the 
plate was engrartdy an impression might be obtained. This was found 
to be the case, for, on detaching the precipitated metal, the more deli- 
cate and superficial markings, from the fine particles of powder used 
in xx>lishing, to the deeper touches of a needle or g^raver, exhibited 
their corresponding impressions in relief with great fidelity. It is, 
therefore, evident that this principle will admit of improvement and 
that casts and moulds may be obtained from any form of copper. 

*' This rendered it probable that impressions might be obtained from 
those other metals having an electro -negative relation to the zinc plate 
of the battery. With this view a common printing type was substi- 
tuted for the copperplate and treated in the same manner. This also 
was successful ; the reduced copper coated that portion of the type 
immersed in the solution. This, when removed, was found to be 
a perfect matrix, and might be employed for the purpose of casting 
when time is not an object. 

** It appears, therefore, that this discovery may possibly be turned 
to some practical account. It may be taken advantage of in procuring 
casts from various metals as above alluded to ; for instance, a copper 
die may be formed from a cast of a coin or medal, in silver, tyx>emetal, 
lead, &c., which may be employed for striking impressions in soft 
metals. Casts may probably be obtained from a plaster surface sur- 
rounding a plate of copper ; tubes or any small vessel may aliK) 
be made by precipitating the metal around a wire or any kind of sur- 
face to form the interior, which may be removed mechanically by the 
aid of an acid solvent, or by heat." [May 22nd, 1839.] 

It is a remarkable fact that Jordan^s letter, regardless of the valu- 
able information it contained, conmianded no attention at the time. 
Indeed, the subject of which it treated (as also did Jacobi's announced 
discovery), apparently passed away from public view, until a paper by 
Mr. Thomas Spencer, of Liverpool, was read before the Liverpool 
Philosophical Society on the 12th of September in the same year. 
Omitting the prefatory observations with which the paper commenced, 
its reproduction will form a necessary link in the chain of evidence 
respecting the origin of the electrotype process, and assist the reader 
in forming his own judgment as to whom the merit of the discovery 
is really due. 

Spencer's Paper on the Bleetrotype Frooeee. — '* In September, 
1837, I was induced to try some experiments in electro-chemistry with 
a single pair of plates, consisting of a small piece of zinc and an equal 
sized piece of copper, connected together with a piece of wire of the 
latter metal. It was intended that the action should be alow ; the 



spencer's paper on BLECTROTYPINO. 83 

iluidfl in which the metallic electrodcR were immersed were in oonae- 
quence Hcparated by a thick disc of plaster of Paris. In one of the 
cells was sulphate of copper solution, in the other a weak solution of 
common salt. I need scarcely add that the copper electrode was placed 
in the cupreous solution, not because it is directly connected with what 
I have to lay before the society, but because, by a portion of its 
results, I was induced to come to the conclusion I have done in the 
following paper. I was desirous that no action should take place on the 
wire by which the electrodes were held together. To attain this object 
I varnished it with sealing-wax varnish ; but, in so doing, I dropped 
a portion of it on the copper that was attached. I thought nothing 
of this circumstance at the moment, but put the experiment in action. 

** The operation was conducted in a glass vessel ; I had, conse- 
quently, an opportunity of occasionally examining its progress. 
When, after the lapse of a few days, metallic ciystals had covered the 
copper electrode, ttnth the exception of that portion which had been 
spotted with the drops of varnish, I at once saw that I had it in my 
power to g^ide the metallic deposition in any shape or form I chose 
by a corresponding application of varnish or other non-metallic 
substance. 

** I had been long aware of what every one who uses a sustaining 
galvanic battery with sulphate of copper in solution must know, that 
the copper plates acquire a coating of copper from the action of the 
battery ; but I had never thought of applying it to a useful purpose 
before. My first essay was with a piece of thin copper-plate, having 
about four inches of superfices, with an equal -sized piece of zinc, 
connected tog^ether with a piece of oop})er wire. I gave iAxe copper a 
coating of soft cement consisting of bees-wax, resin, and a red 
earth — Indian or Calcutta red. The cement was compounded after 
the manner recommended by Dr. Faraday in his work on chemical 
manipulation, but with a larger proportion of wax. The plate re- 
ceived its coating while hot. On cooling, I scratched the initials of 
my own name rudely on the plate, taking special care that the cement 
was quite removed from the scratches, that the copper might be 
thoroughly exposed. This was put into action in a cylindrical glass 
vessel about half filled with a saturated solution of sulphate of copper. 
I then took a common gas glass, similar to that used to envelop an 
argand burner, and filled one end of it with plaster of Paris to the 
depth of three-quarters of an inch. In this I put some water, adding 
a few crystals of sulphate of soda to excite action, the plaster of Paris 
serving as a partition to separate the fluidp, but sufficiently porous to 
allow the electro-chemical fluid to penetrate its substance. 

''I now bent the wires in such a form that the zinc end of the 
arrangement should be in the saline solution, while the copper end 



84 HISTORICAL REVIEW OF ELECTRO-l>EI»OSITION. 

should be in the cupreous one. The ga8 glauB, with the wiie, was 
then placed in the vessol containing the sulphate of copper. 

** It was then suffered to remain , and in a few hours I peroeiTed 
that action had commenced, and that the portion of the copper 
rendered bare by the scratches was coated with a pure bright de- 
posited metal, whilst all the surrounding portions were not at aJl acted 
upon. I now saw my former observations realised ; but whether the 
deposition so formed would retain its hold on the plate, and whether 
it would be of sufficient solidity or streng^ to bear working if applied 
to a useful purpose, became questions which I now endeavoured to 
solve by experiment. It also became a question whether, should I be 
successful in these two points, I should be able to produce lines 
sufficiently in relief to print from. The latter appeared to depend 
entirely on the nature of the cement or etching ground I might use. 

'^This last I endeavoured to solve at once. And, I may state, 
this appeared to be the principal difficulty, as my own impression 
then was that little less than Jth of an inch of relief would be 
requisite. 

** 1 then took a piece of copper, and gore it a coating of a modifica- 
tion of the cement I have already mentioned, to about Jth of an inch 
in thickness ; and, with a steel point, endeavoured to draw lines in 
the form of net- work, that should entirely penetrate the cement, and 
leave the surface of the copper exposed. But in this I experienced 
munh difficulty, from the thickness I deemed it necessary to use; 
more especially when I came to draw the cross lines of the net-work. 
When the cement was soft, the lines were pushed as it were into each 
other ; and when it was made of a harder texture, the intervening 
squares of net-work chipped off the surface of the metallic plate. 
However, those that remained perfect I put in action as before. 

** In the progress of this experiment, I discovered that the solidity 
of the metallic deposition depended entirely on the weakness or 
intensity of the electro -chemical action, which I found I had in my 
power to regulate at pleasure, by the thickness of the intervening wall 
of plaster of Fans, and by the coarseness and fineness of the material. 
I made three similar experiments, altering the texture and thickness 
of the plaster each time, by which I ascertained that if the plaster 
partitions were thin and coarse ^ the metallic depositions proceeded with 
great rapidity^ but the crystals were friable and easily separated ; on 
the other hand, if I made the partition thicker, and of a little finer 
material, the action was much slower, and the metallic deposition was 
as solid and ductile as copper formed by the usual methods, indeed, 
when the action was exceedingly slow, I have had a metallic depo- 
sition apparently much harder than common sheet copper but more 
)t)rittle. 



8raNCEB*S PAPER ON ELECTBOTYFIKG. ^5 

** There was one most important (and, to me, discouraging') 
ciromnfitanoe attending these experiments, which was that when I 
heated the plates to get off the covering of cement, the meshes of 
copper net- work invariahly came off with it. I at one time imagined 
this difficulty insuperable, as it appeared to me that I had cleared the 
cement entirely from the surface of the copper I meant to have ex- 
posed, but that there was a difference in the molecular arrangement of 
copper prepared by heat and that prepared by voltaic action which 
prevented their chemical combination. However, I then determined, 
should this prove so, to turn it to account in another manner, which I 
shall relate in a second portion of this paper. I then occupied myuelf 
for a considerable period in malriTig ezperinients on this latter section 
of the subject. 

" In one of them I found on examination a portion of the copper 
deposition, which I had been forming on the surface of a coin, ad- 
hered so strongly that I was quite unable to get it off ; indeed, a 
chemical combination had apparently taken place. This was only in 
one or two spots on the prominent parts of the coin. I immediately 
recollected that on the day I put the experiment in action I had been 
using nitric acid for another purpose on the table I was operating on, 
and that in all probability the coin might have been laid down where 
a few drops of the acid had accidentally fallen. I then took a piece 
of copper, coated it with cement, made a few scratches on its surface 
until the copper appeared, and immersed it for a short time in dilute 
nitric acid, until I perceived, by an elimination of nitrous gas, that 
the exposed portions were acted upon sufficiently to be slightly 
corroded. I then washed the copper with water, and put it in action, 
as before described. In forty-eight hours I examined it, and found 
the lines were entirely filled with copper ; I applied heat, and then 
spirit of turpentine, to get off the cement ; and, to my satisfaction, I 
found that the voltaic copper had completely combined itself with the 
sheet on which it was deposited. 

** I then gave a plate a coating of cement to a considerable thick- 
ness, and sent it to an engraver ; but when it was returned, I found 
the lines were cleared out, so as to be wedge-shaped, or somewhat in 
form of a V, leaving a hair line of copper exposed at the bottom and 
broad space near the surface ; and where the turn of the letters took 
place, the top edges of the lines were galled and rendered raggped by 
the action of the graver. This, of course, was an important objection, 
which I have since been able to remedy in some respects by alteration 
in the shape of the graver, which should be made of a shape more 
resembling a narrow parallelogram than those in common use ; 
some of the eng^vers have many of their tools so made. I did not 
put this plate in action, as I saw that the lines, when in relief, would 



86 HISTORICAL BEVIEW OF ELECTBO-DEPOSITION. 

have been broad at the top and narrow at the bottom. I took another 
plate, guve it a coating of the wax, and had it written on with a mere 
point. I deposited copper on the lines and afterwards had it printed 
from. 

'* I now considered part of the difficulties removed; the principal 
one that yet remained was to find a cement or etching-ground, the 
texture of which should be capable of being cut to the required 
depth, and without raising what is technically termed a buir, and at 
the same time of sufficient toughness to adhere to the plates where 
reduced to a small isolated point, which would necessarily occur in 
the operation which wood-eng^vers term cross-hatching. 

*^ I tried a number of experiments with different combinations of 
wax, resin, varnishes and earths, and also metallic oxides, all with 
more or less success. The one combination that exceeded all others 
in its texture, having nearly every requisite (indeed, I was enabled to 
polish the surface nearly as smooth as a plate of glass), was principally 
composed of virgin wax, resin, and carbonate of lead — the white-lead 
of the shops. With this compound I had two plates, 5 inches by 7, 
coated over, and portions of maps cut on the cement, which I had 
intended should have been printed off and laid before the British 
AjBsociation at its meeting." 

BlliBet of fl!p«iie«r'B Paper. — ^When Spencer*s paper was published 
it at once commanded profound attention, and many persons practised 
the new art either for amusement or scientific research, while others 
turned their attention to it with a view to m^iking it a source of com- 
mercial profit. It was not, however, until Mr. Kobert Murray, in 
January, 1840, informed the members of the Boyal Institution, 
London, that he had discovered a method of rendering non-conduct- 
ing surfaces — such as wax, &c. — conductive of electricity by employ- 
ing plumbago, or black lead, that the art became really popular in the 
fullest sense. This conducting medium was the one thing wanted to 
render the process facile and complete ; and soon after Mr. Murray's 
invaluable discovery had been made known, thousands of persoiLS in 
every grade of life at once turned their attention to the electrotype 
process until it soon became the most popular scientific amusement 
that had ever engaged the mind, we may say, of a nation. The sim- 
plicity of the process, the trifling cost of the apparatus and materials, 
and the beautiful results which it was capable of yielding, without 
any preliminary knowledge of science, all combined to render the new 
art at once popular in eyery home. Every one practised it, including 
the youth of both sexes. 

It is not to be wondered at that an art so fascinating should have 
produced more than an ephemeral effect upon the minds of some of 
those who pursued it. Indeed, it is wiUiin our own knowledge that 



MB. DIBOKS ON JORDAN'S DI8GOVESY. 87 

niany a youih whose first introduction to chemical manipulation was 
the electro -deposition of copper upon a sealing-wax impression of a 
signet-ring or other small object, acquired therefrom a taste for a 
more extended study of scientific matters, which eventually led up to 
his devoting himself to chemical pursuits for the remainder of his 
days. At the period we refer to there were but few institutions in 
this country for the encouragement of scientific study. One of the 
most accessible and useful of these, however, was that founded by 
Dr. Birkbeck, the weU-known Literary and Scientific Institution at 
that time in Southampton Buildings, London. 

Vindication of Jordan's Claim. — ^Although Jordan's letter was 
published, as we have shown, three months prior to the reading of 
Spencer's paper in Liverpool, that important communication was 
overlooked, not only by the editor of the journal in which it appeared, 
but also by the scientific men of the period. Even the late Alfred 
Smee, to whose memory we are indebted for the most delightful work 
on electro -metallurgy that has appeared in any language, failed to 
recognise the priority of Jordan' 8 claim. Lnpelled by a strong sense 
of justice, however, the late Mr. Henry Dircks wrote a series of 
articles in the Mechanic's Magazine in 1844, ^ which he proved that 
whatever merit might have been due to Spencer and Jacobi, Jordan 
was unquestionably the first to publish a process of electrotyping. 
Lideed, he went fiuther, for he proved that the electro-deposition of 
copper had been accomplished practically long before the publication 
of any process. Before entering into the merits of Jordan's priority. 
Mr. Dircks makes this interesting statement : — 

Wtt. Blroks on Jordan's Macovsiy. — **The earliest application 
of galvanic action to a useful and ornamental purpose that I am 
acquainted with was practised by Mr. Henry Bessemer, of Baxter 
House, Camden Town, who, above ten years ago [about 1832] 
employed galvanic apparatus to deposit a coating of copper on lead 
castings. The specimens I have seen are antique heads in relief, the 
whole occupying a space of 3 inches by 4 inches. They have lain as 
ornaments on his mantel-piece for many year^, and have been seen by 
a great number of persons." 

Appreciating — ^from its historic and atiientific interest — the impor- 
tance of the above statement, it occurred to the author that if the 
means adopted at so early a period in electro -metallurgical hi.story 
could become known, this would form an important link in the chain 
of research respecting the deposition of metals by electrolysis. He, 
therefore, wrote to Sir Henry Bessemer, requesting him to furnish 
such particulars of the method adopted by him in depositing copper 
upon the objects referred to as lay in his power after so long a period 
of timo. With kind courtesy, and a generous desire to comply with 



88 HISTORICAL REVIEW OF ELECTRO-DEPOSITION. 

the author' 8 wishes, Sir Henry took the tronble to furnish the infor- 
mation conveyed in the following interesting oommnnicationy which 
cannot fail to be read with much gratification by all who have 
studied the art of electro -deposition, either from its scientific or prac- 
tical aspect. When we call to remembrance the numerouB inventions 
with which the active mind of Sir Henry Bessemer has been associated 
during the greater portion of the present century, culminating in his 
remarkably successful improvements in the manufacture of steel, it is 
pleasing to read that at the youthful age of eighteen — when voltaic 
electricity was but little understood, and DanieU*8, Grove's, and 
Smee's batturies unknown — ^ho was engaged in experiments with 
metals, which were evidently conducted with an amount of patience 
and careful observation which would have been highly creditable in a 
person of more advanced years. 

Sir Huiry 8ttSMm«r's Bzp«rlin«nta. — Replying to the author*s 
inquiry of Sir Henry B?ssemer (in January, 1885) as to the method h- 
had adopted in coating with copper the objects referred to above, Sir 
Henry wrote as follows ; and the minuteness of the details, given after 
so great a lapse of time, will doubtless strike the reader with some 
astonishment : — 

** I have much pleasure in replying to your note of inquiry in 
reference to the deposition of copper from its solutions on white metal 
castings. 

** My first experiments bogfan when I was about eighteen years of 
age, say in 1831-2. At that period, after much practice, I was most 
successful in producing castings of natural objects in an alloy of tin, 
bismuth, and antimony. In this alloy I cast such things as beetles, 
frogs, prawns, &c. ; also leaves of plants, flowers, moss-rose buds ; 
and also medallions, and larger works in basso-relievo. By my 
system of casting in nearly red-hot metal, the metal was retained for 
ten or fifteen minutes in a state of perfect fluidity in the mould, 
and hence, by its pressure, forced itself into every minute portion of 
the natural object, whatever it might be ; thus every minute thorn 
on the stem of the rose was produced like so many fine projecting 
needles. I exhibited several of these castings, coated with copper, at 
* Topliss's Museum of Arts and Manufactures,' at that time occupy- 
ing the site of the present National Gallery, and which museum was 
aften^'ards removed to a large building in Leicester Square, now the 
Alhambra Theatre, where I also exhibited them. 

** Beautiful as were the forms so produced, they had a common 
load-like appearance, which took much from their value and artistic 
beauty, and as a remedy for this defect, it occurred to me that it was 
possible to give them a thin coat of copper, deposited from its solu- 
tion in dilute nitric acid. ThiB I made by putting a few pence [copper 



SIB Ht BESSBMEB*S EXPEDIENTS. 89 

ooizLB were in cuirency in those days] into a basin with water and 
nitric acid. My early attempts were not very successful, for the depo- 
sited metal could be rubbed off, and was in other ways defective. I 
next tried sulphate of copper, both cold and boiling solutions. I 
found the sulphate much better adapted for the purpose than the 
nitrate solution. At first I relied on the property which iron has of 
throwing down copper from its solutions, and by combining iron, in 
comparatively Lirge quantities, with antimony, and using this alloy 
with tin, bismuth, and lead, I succeeded in getting a very thin, but 
even, coating of copper ; but it was not sufficiently solid, and easily 
rubbed off. 

'* In pursuing my experiments, I found that the result was much 
improved by using a metallic vessel for the bath instead of an earthen- 
ware one, such as a shallow iron, tin, or copper dish, as a slight 
galvanic action was set up, but the best results were obtained by using 
a zinc tray, on the bottom of which the object was laid, face upwards, 
and the solution then poured in. By this means a very firm and solid 
coating was obtained, which could be burnished with a steel burnisher 
without giving way. By adding to the copper solution a few crystals 
of distilled verdigris, I obtained some beautiful green bronze deposits, 
a colour far more suitable for medallumt and bwU than the bright 
copper coating obtained by the sulphate when used alone. 

*' I cast and coated with g^reen copper a small bust of Shakespeare, 
which, with many other specimens, I sold to Mr. Campbell, the 
sculptor, who at that time was modelling a life-sized bust of Canning : 
he had arranged that I should cast it from the ** lost-wax,'* and 
deposit green copper thereon. Unfortunately Campbell died before his 
model was completed. But for this incident I might possibly have 
carried the depositing process much further, but at that time my suc- 
cess in casting, in a very hard alloy, dies used for embossing card- 
board and leather, offered a more direct and immediate commercial 
result, and thus the artistic branch was lost sight of. I remember 
showing some of these castings to my friend the late Dr. Andrew 
Ure, about the year 1835-6, with which he was much pleased. In 
referring to them several years later, in the second edition of his 
supplement to his * Dictionary of Arts and Manufactures,' published 
in 1846, he mentions these castings us lead castings^ at page 70, 
imder the head of * Electro-Metallurgy,' which commences in these 
words : — 

** * Electro' Metallurgy. — By this elegant art, perfectly exact copies of 
any object can be made in copper, silver, gold, and some other 
metals, through the agency of electricity. The earliest application of 
this kind seems to have been practised about ten years ago^ by Mr. 
Bessemer, of Camden Town» London, who deposited a coating of 



90 mSTOBIOAL REVIEW OF ELEOTBO-DE POSITION. 

copper upon lead castings so as to produoe antique heads, in relief, 
about three or four inohes in size. He contented himself with form- 
ing a few such ornaments for his mantel-pieoe, and though he made 
no secret of his purpose, he published nothing upon the subject. A 
letter of the 22nd of Hay, 1839, written by Mr. G. Jordan, which ap- 
peared in the Mechanic* a Ma^azitie for June 8th following, contains 
the first printed notice of the manipulation requisite for obtaining 
electro -metallic casts, and to this g^entleman, therefore, the world is 
indebted for the first discovery of this new and important application 
of science to the uses of life.' 

** The first inception of the idea of coating works of art in metal 
with a deposited coating of another metal, if not resting solely with 
me, at least I certainly was within measurable distance of this great 
discovery some three or four years before it was brought forward by 
any other person, but I failed to see its true significance, and conse- 
quently lost a grand opportimity. 

^ *■ You are quite at liberty to make any use you Uke of this informa- 
tion." 

We will now return to Mr. Dircks' vindication of Jordan's claim. 

Referring to Jordan's letter to the Mechanic's Magazincy Mr. Dircks 
says, '* In particular I would direct attention to the fact of the main 
incidents named by Mr. Jordan, published June 8th, 1839, agreeing 
with those published by Mr. Spencer, September 12th, 1839, and, 
curious enough, being called forth by the same vague announcement of 
X'rofessor Jaoobi's experiments which was then niaking the round of 
the periodicals. Both parties described Br. Gliding Bird's small 
galvanic apparatus; one used a printer's type, the other a copiKT 
coin, and both recommend the application of heat to remove the pre- 
cipitated copper. 

'' I was aware of Mr. Jordan's letter at the time of its publication, 
and have frequently been surprised since, that his name has not 
transpired in any discussion I have heard upon the subject. Nothing 
can be clearer than his reasoning, the details of hin experiments, and 
his several concluding observations." 

Dr. Odldliiff Bird's Bzperimenta. — ^There can be no doubt what- 
ever that after Dr. Gk)lding Bird published the results of his interest- 
ing experiments in 1837, and the means by which he obtained his im- 
portant results, many scientific men devoted themselves to investigating 
the new application of electricity, amongst whom was Mr. Henry Dircks. 
" It was particularly in September and October, 1837," wrote Mr. 
Dircks, *' that several parties attached to scientific pursuits in Liver- 
ixx)l, were engaged in repeating the experiments of Dr. Ck)lding Bird, 
and of which he gjive an acconnt before the chemical section of the 
British Association at Liverpool, over which Dr. Faraday presided. 



DR. OOLDINO BIBD 8 EXPEBIMSNT8. 9 1 

The apparatus used on that occasion by myself and others was pre- 
cisely that recommended by Dr. Bird, consisting* of simply any glass 
vessel capable of holding a solution of common salt, into which is in- 
serted a gas lamp chimney, having its lower end plugged up by pour- 
ing into it plaster of Paris ; a solution of sulphate of copper is then 
poured into it, and the whole immersed into the contents of the glass, 
and tightened with pieces of cork. The result expected from this 
arrangement was the deposit of metallic veins of the copper within the 
plaster diaphragm, independent of any connection with the poles of 
the battery. Dr. Faraday, and every other electriciaui expressed 
surprise and doubt at the results in this respect said to have been 
obtained by Dr. Bird ; and Dr. Faraday particularly urged the neces- 
sity and importance of caution in receiving as established a result so 
greaUy at variance with all former experience, and proceeded to 
explain a variety of causes tending to lead to fallacious results in the 
curious and interesting experiments.*' 

Up to this time, the possibility of obtaining electrical effects 
by means of a single metal, in the manner pursued by Dr. Bird, 
would have been considered theoretically impossible. It must not be 
wondered at, therefore, that even the gfreatest of our philosophers — 
Michael Faraday — should have been sceptical in the matter. It is 
clear now, however, that Dr. Grolding Bird's results were based upon 
principles not then understood, and that to this gifted physician we 
ai'e indebted for what is termed the *' single-cell '' voltaic arrange- 
ment — the first, and for some time after the only, apparatus employed 
in producing electrotyx)ee. 

Origin of the Forous Cell, — It appears that whUe Mr. Dircks was 
experimenting (in 1837) in obtaining crystals of copper by Dr. Bird's 
method, he was frequentiy in communication with Mr. John Dancer, 
a philosophical instrument maker in Liverpool, and in October of the 
following year (1838) that gentieman showed him a '' ribbon of copper, 
thin, but very firm, granular on one side, while it was bright and 
smooth, all but some raised lines, on the other." This result, Mr. 
Dancer informed him, was obtained by galvanic action, obser\'ing 
that some specimens were as tenacious as rolled copper, while others 
were crystalline and britUe. Mr. Dancer attributed the superiority 
of the former to the following cause : * ' Having gone to the potteries 
to look out suitable jars for sustaining batteries, and having fixed on 
a lot which he was told would not answer as they were not glazed^ and 
would not hold liquor," it occurred to him that such uttglazed jars 
might be turned to account, and used instead of bladder, brown paper 
plaster of Pans, and other porous substances he had previously em- 
ployed. Having obtained a sample for experiment, he Bubsequentiy 
found that he oould obtain a more firm and compact deposit of copper 



C)2 HISTORICAL REVIEW OF ELECTBO-DE POSITION. 

than in any previous experiment. To the accidental oiroiimstance 
above referred to, we are undoubtedly indebted for that most import- 
ant accessory to the single-cell apparatus and tiie two-fluid battery — 
the porous eelL 

In a letter to Mr. Dircks, relative to Spencer's claim to the discovery 
of a means of obtaining *' metallic casts " by electro-deposition, Mr. 
Dancer says, **I met Mr. Spencer one morning in Berry Street, 
Liverpool, and happened to have one of these precipitated copper 
plates with me, which I showed to him. When I told him how it had 
been formed he would scarcely believe it, until I pointed out the im- 
pressions in relief of all the minute scratches that were on the plate 
against which it had been deposited. The surprise that Mr. Spencer 
expressed very naturally led me to suppose that it was the first com- 
pact piece of precipitated copper he had seen." At this early period 
(1838) Mr. Dancer had not only deposited tough reguline copper, but 
he went a step farther. He attached to a copper plate, by means of 
varnish, ' *■ a letter cut out from a printed bill. The copper precipitated 
on all parts of the plate, except where the letter was fixed ; when I 
peeled the precipitated copper off, the letter came out, not having 
connection with the outside edge. I also obtained an impression by 
stamping my name on a copper cylinder, the impression being the 

reverse way All this happened many months before I was 

aware that Mr. Spencer had been engaged in anything of the kind, 
except that he had Dr. Bird's experiments in action. Some time after 
this Mr. Spencer applied to me for one of my porous jars, and one day 
at his house he told me for what purpose he wanted it." 

It is perfectly eWdent that Mr. Dancer's results were obtained long 
before the publication of Spencer's paper, and that both were indebted 
to Dr. Golding Bird's simple but ingenious contrivance for prose- 
cuting their first experiments ; and it is also clear that Dancer's 
brilliant idea of substituting porous earthenware for the crude plaster 
diaphragms g^reatly facilitated experimental researches in this 
direction ; while at the same time it placed within our reach one of 
the most valuable accessories of the two-fluid voltaic battery — the 
porous cell. 

Being desirous of placing Jordan's claim to priority — ^as the first 
to make publicly known the process of electrotyping, or electrographjfy 
as ho termed it — Mr. Dircks followed up the subject in the Mechamc^a 
Maj/azinCy in a series of papers, in which he not only traced Mr. 
Spencer's experiments to their true origin, namely, Dr. Bird's 
experiments published two years before, and the hints which he had 
derived from Dancer, but he moreover showed that Spencer must 
have been aware of Jordan's published process, for he says, in 
summing up the evidence he had produced against Spencer's position 



DntcKs ON spbnckr's claim. 93 

in the matter thns : ** Lastly, therefore, that through the Meehanie^s 
Magaeme (which Mr. Spencer was regularly taking in) the experimental 
results obtained by Mr. Dancer, and the reports in April and May, 
1839, in public papers, of Jaoobi's experiments, all being broad hints, 
and abundant assistance to aid Mr. Spencer, that he is rather to be 
praised for his expression of what was already known, on a smaller 
and less perfect scale, than to be adjudged a discoverer, much less 
the father of electro -metallurgy, haying a preference to every other 
claimant." Following the paper from which the foregoing extract is 
taken, is a footnote by the Editor of the MeehanieU Magaziney which is 
important as showing how strange it was that Jordan's communication 
not only escaped the attention of scientists, but even that of the con- 
ductor of the journal in which it appeared : ** Mr. Dircks has proved 
beyond all doubt that we have made a great mistake in advocating so 
strenuously the claims of Mr. Spencer to the invention of electro- 
graphy. No one, however, can suppose that we would intentionally 
exalt any one at the expense of our own journal, which we are now 
X^leased to find was the honoured medium of the iirst distinct revela- 
tion of this important art to the public, by an old and esteemed 
correspondent of ours, Mr. Jordan. Whatever Mr. Bessemer, Mr. 
Dancer, Mr. Spencer, or others, may have previously said or done, it 
was in private — made no secret of, perhaps, but still not communicated 
to the public at large — not recorded in any printed work for general 
benefit. For anything previously done by any of them, they might 
li a ve still remained in the prof oundest obscurity . No public description 
of an earUer date than Mr. Jordan's can, we believe, be produced ; 
and when we look upon that description, it is really surprising to see 
with what fulness and precision the writer predicated of an art nearly 
aU that has been since accomplished. In supporting, as we did, the 
claims of Mr. Spencer to be considered as the first discoverer, we had 
lost all recollection of Mr. Jordan's communication. We have no 
personal acquaintance with either of the gfentlemen, and could have no 
motive for favouring one more than the other. We took up the cause 
of Mr. Spencer with spontaneous warmth because we thought him to 
be a person most unfairly and ungenerously used, as in truth he was 
so far as the intention went, by those who, having at the time none of 
those reasons we now have for questioning Mr. Spencer's pretensions, 
yet obstinately refused to acknowledge them. If it should seem to 
the reader more than usually surprising that Mr. Jordan's paper 
escaped the recollection of the editor, through whose hands it passed 
to the public, his surprise will be lessened, perhaps, when he observes 
how it appears to have escaped notice, or been passed over in silence, by 
every one else down to the present moment — even those, not a few, who 
have expressly occupied themselves in electrography. . • . . To us. 



94 HISTORICAL REVIEW OF ELECTRO-DEPOSITION. 

the most Burpriaing' thing of any connected i^nth the case is, that 
neither Mr. Jordan himself, nor any of his friendn, should before now 
have thought it worth while to vindicate hin claims to the promulga- 
tion of an art which justly entitles him to take a high place among 
the benefactors of his age and country. — Ed. M. 3/." 

While Mr. Dircks* ^'ContributionR to the History of Electro-Metal- 
lurgy * * were being published in the columns of the Mechanic^ a Magazine^ 
the arguments and facts which he adduced created a deep impreflsion 
in the minds of scientific men of the day, who had unfortimately 
accepted Spencer as the originator of electrotypy. Of all men, scien- 
tists are the most anxious to accord the merit of dittcorrn/ to those who 
are really entitled to it. Devoting themselves to the investigation of 
natural laws, and their application to the useful purposes of man, 
they are naturally jealous of any attempt on the part of one to appro- 
priate the honour — ^usually the only reward — due to another. It is 
not surprising, therefore, that when it became fully proved that 
to Jordan and not Spencer was due the credit of having been the first 
to publish a process for the practical deposition of copper by electro- 
lysis, that such men should frankly acknowledge their mistake. 
Amongst those who came forward to do justice to Jordan's claim 
were the late Professor Faraday, Dr. Andrew Ure, and Professor 
Brande, then chemist to the Royal Mint. The latter eminent chemist 
and author of the best chemical manual in our lang^uage, sent the 
following letter to Mr. Dircks, which clearly acknowledges the error 
into which, in common with others, he had fallen in attributing to 
Spencer the merit of the electrotype process : — 

*' I am much obliged by your copy of the Meehanie'a Magazine and 
the information it contains respecting Mr. Spencer's pretensions. I 
certainly always gave him credit for much more merit than he appears 
to have deserved." 

When Spencer found that his position was so severely shaken by 
Mr. Dircks' powerful defence of Jordan's claim to priority, he wrote 
several letters in reply, which appeared in the columns of the above 
journal, with a view to refute his opponent's arg^uments, and shake 
his testimony ; but in this he was unsuccessful, for the facts which 
Mr. Dircks had made known were absolutely beyond refutation. It 
is not often that men of science enter into a controversy of this nature, 
but silence under such circumstances would have been an act of injus' 
tice to Jordan, by leaving the question still in doubt. 

Amongst those who ascribed to Spencer the discovery of the elec- 
trotype process was Mr. Greorge Shaw, of Birmingham, in the first 
edition of his ** Manual of Electro -Metallurgy." In the second 
edition of his work, however, he made the ametide to Jordan, by 
frankly aoknowledgfing his mistake. The following letter from the 



DTRCKS ON SPENCEB*8 CLAIM. 95 

late Dr. Andrew lire to Mir. Dircks shown how fully he recognised 
that gentleman's advocacy of Jordan's claim : ''I read with great 
interest your narrative of the discovery or invention of the electrotype 
art, and am much pleased to see justice done to modest retiring merit 
in the persons of Mir. Jordan and Mr. Dancer. The jay will feel a 
little awkward this cold weather, stripped of his peacock plumage.'* 

The following letter from Faraday tends to show that the great 
philosopher, in common with most other persons, had, prior to Mr. 
Dircks' explanation of the facts, believed in Spencer being the origi- 
nator of electrotyping : *^ I am very much obliged by your kindneM 
in sending me your account of the facts, &c., &c. It is very valuable 
as respects the fixing of dates, and has rather surprised me." * 

It is a pity, but none the less true, that while Jordan's communica- 
tion received no attention whatever, although published in a well- 
read journal, Spencer's paper — which had merely been read before a 
local society in Liverpool, and afterwards printed for private eircukttian 
only — commanded the profoundest attention. In short, to use a 
common phrase, it **took the world by storm." The name of 
"Spencer, the discoverer of Electrotjping," was on every lip, and 
men of science of all nations regarded him as one who had made 
a great addition to the long roll of important discoveries which 
science had placed at the disposal of art. Henry Dircks' champion- 
ship of Jordan's just claim, however, eventually broke up Spencer's 
position, and to the first publisher of the electrotype proeessy Mr. G. J. 
Jordan, was at last accorded the merit — for he received no other recog- 
nition — of having published a process, if we may not say discovery, 
which was destined to prove of inestimable advantage to his fellows, 
not only in itself, but as being the means by which the minds of men 
were directed to the deposition of other metals by electrical agency. 
It would not be out of place to suggest that in commemoration of 
Jordan's gift to mankind of so useful and valuable a process, an 
appropriate testimonial should be set on foot — if not by the public, at 
least by those who have directly gained so much by his initiation of 
the art of electro-deposition. 

The success which attended the electrotype process induced many 
persons to turn their attention to the deposition of gold and silver, by 
means of the direct current ; but up to the year 1840 no really suc- 
cessful solution of either metal was available, iln that year Mr. John 
Wright, a surgeon in Birmingham, and Mr. Alexander Farkes, in 
the employment of Messrs. Elkington, were engaged in making 
experiments in electro-deposition, when the former gentleman hap- 



* The three foregoing letters, which we transcribed from the originals, are 
now, we believe, pablished for the first time. 



96 HISTORICAL REVIRW OF BLBCTRO-DErOSTTTON. 

pened to meet with a passage in Scheele's *^ Cliemical Rsmiys/* in 
which he found that cyanides of gold, silver, and copper, were 
soluble in an excess of cyanide of potassium. It at once occurred to 
him that solutions of gold and silver thus obtained might be employed 
in electro*doposition, and ho then formed a solution by dissolving 
chloride of silver in a solution of forro -cyanide of potassium, from 
which he obtained, by electrolysis, a stout and iirm deposit of silver, 
a result which had never before been obtained. A few weeks after, 
Mr. Wright prepared a solution with cyanide of pota.ssium, instead of 
the ferro -cyanide, and although various cyanide solutions of silver 
and copper had already been employed in the simple immersion 
process of depositing these metals, there is no doubt that it is to Mr. 
"Wright tliat we are really indebted for the practical application of 
cyanide of potassium as a solvent for metallic oxides and other stilts 
used in electro -deiwsition. About this time (1840) Messrs. Elkington 
were preparing to take out another patent, when Mr. Wright, haviiiij 
submitted his results to them, agreed to include his process in th(>ir 
patent, in consideration of which it was agreed that he should reccivf^ 
a royalty of one shilling per ounce for all silver deposited under tlie 
patent : on his decease, which took place soon afterwards, an annuity 
was granted to his widow. This patent, with Wright's important 
addition, namely the employment of alkaline cyanides, formed the 
basis of the now great art of electro -gilding and plating : but it was 
some time before the proper working strength of batiis and the pro- 
portion of cyanide could be arrived at, the deposits being frequently 
non-adherent, which caused them to strip or peel off the coated articles 
m the process of burnishing. This was afterwards remedied to some 
extent by dipping the articles (German silver chiefly) in a very dilute 
solution of mercury. About this time, the author, in conjunction 
with his brother, Mr. John Watt, introduced electro-gilt and silvered 
steel pens, which were sold in considerable quantities. 

In the same year, Mr. Murray discovered a means of rendering 
non-conducting surfaces, as wax, &c., conductive, by coating them 
with powdered plumbago, and this important suggestion proved of 
inestimable advantage to those who desired to follow the art of 
electrotyping conmiercially. Indeed, without the aid of this useful 
substance, it is doubtful whether the important art would have greatly 
exceeded the bounds of experiment. At this period, also, another 
important improvement in the electrotype process was introduced by 
Mr. Mason, which consisted in employing a separate battery as a sub- 
stitute for the "single-cell" process up to that time adopted in 
electrotyping. By the new arrangement, a copper plate was con- 
nected to the positive pole of a Daniell Battery, while the mould to be 
coated with copper was attached to the negative pole. When these 
were immersed in the electrotyping bath (a solution of sulphate of 



DIBCKS ON spencer's CLAIM. 97 

copper), under the action of the current the copper-plate became du* 
solved as fast as pure copper was deposited upon the mould, whereby 
the strength of the solution was kept in an uniform condition. It is 
this method which is now almost imiversally adopted (when dynamo 
machines are not employed) in practising' the art of electrotyping upon 
a large scale. 

In 1 84 1, Mr. Alfred Smee published his admirable work on Electro- 
metallurgy, which at that period proved of the gfreatest service to all 
persons interested in the new art. In the year following, Mr. J. S. 
Woolrich introduced his magneto-electric machine, which for many 
years after occupied a useful position as a substitute for voltaic 
batteries, in several large plating works. In this year also, Dr. H. 
R. Leeson took out a patent for improvements in electro-depositing 
processes, in which he introduced the important elastic moulding 
material, ** guiding wires,*' keeping articles in motion while in the 
bath, &c. 

In 1843, Moses Poole obtained a patent for the use of a thermo- 
electric pile as a substitute for the voltaic battery ; but the invention 
was not, however, successful. Many patents were taken out in the 
following years for various processes connected with electro -deposi- 
tion ; but the next most important improvement was due to Mr. W. 
Milward, of Birming^ham, who accidentally noticed that after wax- 
moulds, which had been covered with a film of phosphorus — by apply- 
ing a solution of that substance in bisulphide of carbon to their surfaces 
— had been immersed in the cyanide of silver plating bath, the silver 
deposit upon other articles, such as spoons and forks, for example, 
which were afterwards coated in the same bath, presented an unusually 
bright appearance in parts, instead of the dull pearly lustre which 
g^neraJly characterises the silver deposit. This incident induced Mr. 
Milward to try the effect of adding bisulphide of carbon to the 
plating bath, which produced the desired result. For some time he 
kept l^e secret to himself; but finding that it eventually became 
known, he afterwards patented the process in conjunction with a Mr. 
Lyons, who had somehow possessed himself of the secret. From that 
time the addition of bisulphide of carbon to silver baths for the pur- 
poses of ** bright *' plating has been in constant use. 



In the foregoing sketch of the origin and history of electro-deposi- 
tion we have endeavoured to give such information eu» we hoped would 
be interesting to many who are engaged in the practice of the art, and 
also instructive to those who may be about to enter into a study of the 
subject, believing, as we do, that the present volume would be incom- 

11 



98 UIBTOKICAL liBVIEV/ OP EI.E0TR0-DKP08IT10N. 

plete witiiout some special reference to the interesting origin of so 
great and useful an art — an art which has many widespread appli- 
cations of great commercial and decorative importance. 

Further reference to suheequent inventions connected with electro- 
deposition and its developments in recent years, will be found in the 
later chapters of this volume* 



i 



CHAPTER IV. 

ELECTRO-DEPOSITION OF COPPEE. 

Electrolyping b; Single-call Procen.— Copjiog Coins ind Mcdili.— Moaltl- 
iDg Uateriab.—GuttB-percha.— PluLic GutU-percha.— GutM-petcha 
&D1I Marine Glue.— Beemax.—SeeliQg-wai.—Siearine.— Stearic Acid.— 
Fusible Metal.— EiaMic Uoulding Material.— Piastet of Paris. 

It may fairly be said that the diBoovery of the electrot}^* pro- 
ceHK formed the busia of the wholo electrolytic industry : and, in 
itjt applications to variovut purposes of the arts and to literature, it 
hua proved of inextimable value. While, in its infancy, the electro- 
type prooesH was a source uf ticientific recreation to thousands of 
persons of all claasea, many were those who saw in the new process a 
wide field of researtih, from which much waa expected and more has 
been realiaed. While Faraday, Becquerel and others were investi- 
gating; the pruccsH iu its more scientifio relational practical men were 
tryin); to apply it tu varioua art purposes, until, in course of time, 
electrotyping was added to our list of chemical arts. 

The simplest form of arrangement for electrotyping small objects 
it) known aa the " single-cetl" process, which it will be welt to con- 
sider before deacribing the more ehiborate apparatus employed fur 
larger work. 

Bl*en«t7pinc W tha BlnBla-o«U Pzooms. — In ita moat aimplo 
form, a small jar. Fig. 53, may be used as the outer 
vexael, and in this ie placed a small porous cell, made 
of unglazed earthenware or bi>wuit porcelain, some- 
what taller than the contoining vessel. A strip of 
slout sheet-zinc, with a piece of copper wiiv attached, 
either ty means of solder or bj' a proper binding 
screw, is placed in the porous cell. A mliiriilnf solu- 
tion of sulphate of copper (bluestone), mode by 
diggolviag orystats of that substance in hot water, Fig. 53. 

smd pouring the liquid, when cold, into the outer cell. 
The poroua coll is then filled to the same height oa the copper 
solution with a solution of aal-ummoniat or common salt. To keep 
up the strength of the solution when in iih' 11 few crystalii of sulphale 
of copper arc phiccd in a mualin bag, whiuh iu booked on to the 



lOO ELBOTBO-DEPOSITIOK OF COPPBB. 

cdffe of the veesel bjr meana of a short copper hook, and the bag 
allowed to dip a little way into the liquid. The prepared mould is 
caimected to the end of the wire (which is beat in this C\ form) aad 
gently lowered into the solution, when the whole arraDgement is 
complete. In place of the porous cell the zinc ma; be wrapped in 
several folds uf brown paper, encloeiDg a little conunou salt, but the 
poroiu ccUh are bo readily obtained that it is never worth while to 
seek H HubHtitul* for them. This simple arrangement will easily be 
understood by Feferring to the cut. 
A more convenient single-cell apparatus is shown in Fig. 54, in 
which the containing vessel, or nl!, ie a gloss or 
stoneware jar capable of holding about three pints. 
In this is placed a porous cell (p). A bar or plate 
of zino (;), with binding screw attached, is de- 
posited in the porous cell ; a short piece of copper 
wire (ip), for saBpending the mould {m) or object to 
ho copied, has its nhorter end inserted in the hole 
of the binding-screw. The outer vessel is about 
three parts filled with a taiiiivled Bulution of sul- 
phate of copper (r), and the porous cell is filled to 
the Esame height with a half-Baturated solution of 
Bsl-ammoniBC or common salt. If the zinc is 
amalijamatcd, however, dilute aulphuric acid is used 
p. inntead of the latter Ewlution in the porouH cell, and 

a small qnantity of oil of vitriol (from half an 
ounce to one uuuco of acid to the quart of copper uolution) added. 

Amalgematviii the Zinc. — Four a little dilute sulphuric acid, or un- 
diluted muriatic acid, into a dish, and, having tied a piece of flannel 
t') the end of a Htiuk, lay the nine in the dish and proceed to brush the 
iicid all over the plate ; now pour a Uttle mercury (quick»ilver) on 
the plate, and mb it over the zinc with the little mop, when it will 
readily spread all over the surface, giving the zinc a bright ulvery 
lustre. It is important that the zino should be thoroiighlt) cleaned by 
(ho acid, otherwise the mercury will fail to amalgamate with the 
metal, and dark patehea of unamalgamated zinc will appear. The 
perforated shelf, or tray, in the engraring is a receptacle for crystals 
of sulphate of copper, which, being placed upon it, gradually become 
dissolved while the deposit of copper ia going on, and thus re-supply 
the solution as it becomes exhausted, whereby the operation progreesos 
unifomdy. 

To prepare tho copper solution for small experimental purposes, 
dissolve about 10 ounces of sulphate of rri]ij>rr in i quart of hot 
water and stir until the cryeiAls ,ire all duwilvcrl ; then wt the vewiel 
aside until cold, when the ci^'rii' liiiuor is to be carefully poured into 



COFTING COINS AND BfEDALS. lOI 

the depositing cell. Wlien unamalgamated zinc is used in the siugle- 
oell arrangement the sulphate of copper nhould be simply a saturated 
solution of the salt without that addition of acid, though a few dropn 
onljf may be added with advantage. 

It is of great importance that the sulphate of copper should be 
pure. The crystals should be of a rich dark blue colour and absolutely 
free from greenish cr3r8tal8 [sulphate of iron)^ which not unfrequently 
get mixed with the copper salt by the carelessness of the shopkeepers' 
ansistants. 

Copylnff Ooins and M<Nla1« — Before explaining the various 
methods of obtaining moulds from different objects, for the purpose 
of producing fac- similes in copper, let us see how wo may employ the 
above apparatus in a more dircH^t way. Suppose we desire to obtain a 
copy, in reverse, of some medal or old coi«, or even a bronze penny - 
piece, having decided which side of the coin it is intended to electro- 
type — say the obrerse or "head" side— we must first render the 
surface clean and bright. Tliis may be very readily done by means 
of rottenstone and a little olive oil, applied with a piece of chamois 
leather and briskly rubbed over the face of the coin. In two or three 
minutes the surface will be sufficiently bright, when the oil must be 
wiped off thoroughly either with cotton wool or blotting paper. A 
short piece of copper wire is next to be soldered to the back of the 
coin, and the polished side is then to be brushed over with a soft plate- 
brush and plumbago, or blacklcad, which will prevent the deposited 
copper from adhering to the medal. In order to prevent the copper 
from being deposited upon the back and rim these parts must be 
coated with some non-conduethu; material. For this purpose paraffin 
wax, applied by gently heating the medal and touching it with the 
wax, or red sealing-wax, dissolved in spirit of wine or wood spirit 
(pyroxylic spirit), brushed over the surfaces to be protected, will 
answer well ; but if the latter is employed it must become thoroughly 
dry before being placed in the copper solution. 

Being thus prepared, the end of the conducting wire is to be in- 
serted in the binding screw attached to the zinc and securely fixed by 
turning the screw until it grips the wire firmly. The coin must be 
lowered into the solution steadily, with its face towards the porous 
cell, and if any air-bubbles appear upon its face they must be re- 
moved by means of a camel-hair brush, or, still better, by blowing 
upon them through a glass tube. It is a good plan to breatlie upon 
the face of the coin before placing it in the solution, which, by cover- 
ing it with a layer of moisture, effectually prevents the formation of 
air-bubbles. 

In about twenty -four hours from tlie first immersion of the medal 
the deposit of copper will generally be sufficiently stout to bear re- 



I02 ELECTRO-DEPOSITTON OF COPPER. 

mo\ing from the original, when the extraneous copper, which has 
sj)read round tlie ed^e of tlie deposit, or electrotype, may Ix? carefully 
broken away by means of small pliers ; if the medal be gently heated 
over a small lamp, the electrotyjMJ will readily become detached, 
and will present, in rever»e^ a perfect copy of the original, in which 
even the very finest lines will b© accurately reproduced. In its 
present condition the electrotype is hard and brittle, and will, there- 
fore, require careful handling. To give it the toughness and flexi- 
bility of rolled copper it is only necessary to heat the electrotype to 
dull redness, which may be conveniently done by placing it on a piece 
of sheet-iron, and laying this on the clear part of a fire until red hot, 
when it must be withdrawn and the " type*' set aside to cool. If 
placed in a very weak solution of sulphuric acid for a few moments, 
then rinsed and dried, and afterwards brushed over with a little rouge 
or whiting, its surface may be readily brightened. 

If wo desire to obtain a copy iw reHef from our elec^trotype (also in 
copper) we must now trt^at it as the mouldy following the same routine 
as before in all respects, by which we shall obtain a perfect fac -simile 
of the original coin, which may be mounted and bronzed by any of 
the processes hereafter given. 

Having thus seen what results may be obtained with the most 
simple application of the single-cell process, we will next turn our at- 
tention tx) the different methods of obtaining moulds from various 
objects, but, before doing so, it will bo necessary to consider tho 
nature of the several substances which are employed in mouldwff and 
the methods of preparing them for use. 

Monldlns Materials. — The chief substances used in the electro- 
typing art for making moulds are gutta-percha, wax, and fusible 
metal ; other materials, however, are employed in certain cases in 
which the substances named would bo inapplicable. The various 
materials will be considered under their separate heads, a* follows : — 

autta-perdia. — This most useful moulding material is the concrete 
juice of Isonandra Gnita^ a tree growing only in the Malayan Archi- 
pelago, and of other species of the same genus. The stem of the 
gutta-percha tree, -which sometimes acquires the diameter of 5 or 6 
feet, after being notched yields a milky juice which, when ex- 
posed to the air for some time, solidifies, and this constitutes the 
gutta-percha of conmierce. As imported, it is in irregTilar blocks of 
some pounds in weight, and conmionly containing a large proportion 
of impurities in the shape of bark, wood, stones, and earthy matter. 
To purify the crude article it is first cut in thin slices, which are after- 
wards torn into shreds by machinery. These are next softened by 
hot water and afterwards kneaded in a masticator j by which the im- 
purities become gradually washed away by the water. After several 



MOULDING MATERIALS. 1 03 

honre the gutta-percha is found to be kneaded into a perfectly homo- 
geneous mass, which is rolled or drawn into sheets, bands, &c. 

Gutta-percha becomes soft and plastic at the temperature of boiling 
water (212° Fahr.), when two pieces may be welded together. It is a 
non-conductor of electricity, and is indeed one of the best inwlatiMff 
materialB known ; it is impervious to moisture, and is scarcely at all 
affected by either acids or alkalies. Owing to its plasticity when soft, 
it is one of the most useful materials for making moulds, yielding im- 
pressions which are exquisitely sharp in the very finest lines. When 
used for making moulds from small objects, as coins, medallions, or 
sealing-wax impressions of seals, a piece of gutta-percha of the re- 
quired size is placed in hot water (the temperature of which should be 
al)out 160^ Fahr.), and, when sufficiently soft, it should be rolled 
while still wet in the palms of the hands until it assumes the form of 
a ball ; it should then again be soaked in the hot water for a short 
time, and be again rolled as before, care being taken to observe that 
the surface of the ball exhibits no seams or fissures. When larger 
objects have to be copied stout sheet g^tta-percha is used, and a piece 
of the required size out from the sheet, which is softened as before, 
then applied to the object, and the necessary pressure g^ven to secure 
a faithful impression. 

FUstle Chitta-pcrolia. — ^When gpitta-percha is steeped for a few 
hours in benzol or naphtha it becomes considerably swollen ; if after- 
wards soaked in hot water it is exceedingly plastic, and requires but 
moderate pressure to obtain most perfect copies from even such fragile 
objects as plaster of Paris models. 

Chitta-p«r6ha mad Mnr**'^ OIim. — ^The following has also been 
recommended : gutta-percha 2 parts, Jeffrey's marine glne i part. 
Each of the materials is first to be cut up into thin strips ; they are 
then to be mixed, placed in a pipkin and heated gently, with con- 
tinual stirring, until the substances have become well incorporated : 
the mixture is now ready for use, and should be rolled into the form 
of balls before being applied for taking impressions. A very useful 
mixture is made by melting thin strips of gutta-percha as before, and 
adding one-third part of lard, keeping the mixture well stirred. It is 
applied by pouring it over flat surfaces, as steel plates, &c. 

Be— wajt. — This is a very useful material for moulding, and may be 
applied either in the form of virgin or white wax, or the ordinary 
commercial article — yellow beeswax. Since this substance, however, 
is very commonly adulterated, it may be useful to know something of 
its natural characteristics. At the temperature of 32° Fahr. beeswax 
becomes brittle, at from 80*^ to 90° it becomes soft and plastic, and it 
melts at about 155** Fahr. Mr. B. S. Proctor says: **It becomes 
pUstio or kneadable at about 85° Fahr. , and its behaviour while worked 



I04 ELECTRO-DEPOSITION OF GOFPEB. 

between the finger and thumb is characteriBtic. A pieoe the size of 
a pea being worked in the hand till tough with the warmth, then 
placed upon the thumb and forcibly stroked down with the forefinger, 
curls up, following the finger, and is marked by it with longitudinal 
streaks." Its ordinary adulterants are resin, farina, mutton suet, 
and stearine, though more ponderous substances, such as plaster of 
Paris, have sometimes been detected. White wax is very commonly 
adulterated with spermaceti, sometimes to the extent of two- thirds of 
the latter to one of wax. These sophistications, although not neces- 
sarily fatal to the preparation of good moulds, are certainly objection- 
able, inasmuch as it not unfrequently happens that a wax mould 
splits or cracks, not alone from cooling too quickly, but owing to the 
presence of for^g^ substances which impair its toughness. 

SdnHng-waXi — This substance may be employed for taking impres- 
sions of seals or crests, and was, indeed, one of the first materials used 
in the earliest days of electrotyping. The material, however, should 
be of good qjoality, and only sufficient heat applied to melt, without 
inflaming it. 

BtearliM. Stearic Aeid. — The former substance is the solid con- 
stituent of tallow, and the latter (stearic acid) is the same substance 
separated from fats by chemical processes. Either may be used for 
making moulds instead of wax ;. but the late C. V. Walker recom- 
mended the following mixture in preference to either : — 

ozs. 

Spermaceti 8 

Wax ij 

Mutton Saet i] 

Another formula consists of ; — 

ozs. 

White Wax 8 

Stearine 3 

Flake White or Litharge .... | 

The whole ingredients are put into a pipkin and gently heated over 
a low fire, with continual stirring, for about half an hour, after which 
the mixture is allowed to rest until the excess of litharge (oxide of 
lead) has deposited. The clear residue is then to be poured into a 
shallow dish, and when cold is put aside until required for use. 

rvudbla MetaL— This alloy, which melts at the temi)erature of 
boiling water, and in some preparations very much below that point, 
is very useful for making moulds from metallic and some other objects ; 
and since it can be used over and over again, and is capable of yielding 
exceedingly sharp impressions, it may be considered one of the most 
serviceable materials employed for such purposes. The following 



BIiASTIO UOULDINO MATERIAL. 



toS 



represent the principal fonnulee for fusible metal, the last ol which 
melts at the low temperature of 151" Fahr. or 61° below the boilingc 
point of water : — 

OZS. OZB. ozs. 

8 II. Bismuth . 8 III. Bismuth 8 

4 Lead . 5 Lead . 4 

4 Tin . 4 Tin . 2 

Antimony i Cadmium 2 



I. Bismuth 
Lead 
Tin 



16 18 16 

The metals are to be put into a crucible or clean iron ladle, and 
melted over a low fire ; when thoroughly fused, the alloy is poured 
out upon a cold surface in small buttons or drops, and these, when 
cold, are to be again melted and poured out as before, the operations 
to be repeated several times in order to ensure a perfect admixture of 
the metals. Another and better plan is to gramilate the metal, or 
reduce it to small grains in the following way : — Fill a tall jar or 
other vessel with cold water, and on the surface of the water place a 
little chopped straw (about 3 inches in length). When the metal is 
melted, get an assistant to stir the water briskly in one direction, then 
pour in the metal, holding the ladle at some distance from the surface 
of the water ; by this means the metal will be diffused and separated 
into a considerable number of small grains. The water is then to be 
poured off, and the grains collected, dried, and re-melted, after which 
another melting and granulation may be effected, and the alloy finally 
melted and cast into a mould, or simply poured out upon a flat iron or 
other surface, when it will be ready for future use. By the repeated 
melting, the alloy loses a little by the oxidation of the metals ; but 
since the heat required to fuse it is less than that of boiling water, the 
loss is but trifling, as compared with the importance of obtaining a 
perfect alloy of the various metals. It should be the practice to 
remove the crucible or ladle from the fire the moment the alloy begfins 
to melt, and to depend upon the heat of the vessel to complete the 
fusion. 

Blaatle Monldlns Material. — For making moulds from objects 
which are much uudtr cuty in which case neither of the foregoing sub- 
stances would be available, an elastic material is employed which has 
the same composition as that from which printers* rollers are made, 
that is to saj, a mixture of glue and treacle, the formula for which 



is: — 



Glue of the best quality 
Treacle . 



ozs. 
12 



»5 



I06 ELFCTROI>EP0STTT0N OF COPPER. 

The glue in first to be covered with cold water and allowed to stand 
for at least twelve hours, by which time it should be perfetly soft 
throughout. The excess of water is then to be poured off, and the 
vessel placed in a saucepan or other convenient utensil, containing a 
little water, and heat applied until the glue is completely melted, 
which may be aided by frequent stirring. When quite melted, pour 
in the treacle, and ag^in stir until perfect incorporation of the 
ingredients is effected, when the composition may be set aside to cool 
until required for use. To check evaporation and consequent drying 
of the surface, the vessel, when the material is quite cold, may be 
inverted over a piece of clean paper, by which, aUo, it will be pro- 
tected from dust. The compound thus formed is exceedingly elastic, 
and may readily be separated from models even when severely 
undercut. Owing to the sobthilUy of this composition, however, some 
care is necessary in using it, otherwise it will become partially dis- 
solved in the copper solution or bath. This is more likely to occur, 
however, when the solutions are of less strength than naturatedy by 
which term we understand that the wator present holds as much 
sulphate of copper in solution as it is capable of doing. Various 
remedies for overcoming this disadvantage will be given when 
treating of the methods of obtaining moulds from the material. 

Flast«r of Paris. — This substance is also used for mould -making, 
either from metallic or natural objects ; but the plaster sliould be of the 
finest quality, such as is used by Italian image makers for the mifface 
of their work, and not the coarse material usually sold in the shops. 
The plaster should he fresh when purchased and preserved in a closely- 
covered jar until required for use. 

Having thus far considered the materials used in making moulds 
for electrotype purposes, we will next explain the mothwls of applying 
them, confining our observations to the more simple examples in the 
initial stages of the process. 



CHAPTER V, 
ELECTRO-DEPOSITION OF COPPER {continued). 

Moulding in Gutta-p«rcha. — Plumbagoing the Mould. — Treatment of the 
Electrotype. — Bronzing the Electrotype. — Moulds of Sealing-wax.-— 
Copying Plaster of Paris Medallions. — Preparing the Mould. — Plumba- 
going. — Clearing the Mould. — Wax Moulds from Plaster Medallions. — 
Moulds from Fusible Metal. 

MoQldlnc in Ontta-p«reluL — In the former caAe, we explained 
how a copy of a coin could be obtained, in ' reverse, by making the 
original act as the mould. We will now turn our attention to 
obtaining fac- simile duplicates in relief, from impressions or moulds of 
similar objects, from such of the materials de.«)cribed in the last 
chapter as will best answer the purpose ; and since the application 
of these materials in the simple way we shall indicate will lead to 
an understanding of the general principles of mould-making, it is 
recommended that the student should endeavour to acquire adroitness 
in taking impressions which will be perfectly sharp and clear, before 
he attempts to obtain metallic deposits of copper upon them. 

To obtain a copy of a modal, coin, or other similar object, the most 
convenient material to employ is gutta-percha. Take a small piece 
of this substance and place it in hot but not boiling water for a few 
minutes, or until it is perfectly soft ; while still wet, roll it between 
the palms of the hands until it assumes the form of a ball ; it should 
then be replaced in the water for a short time, and again rolled as 
before. The coin to be copied is now to be laid, face upward, upon a 
piece of plate-glass, slate, or polished wood. Now take the ball of 
gutta-percha and place it in the centre of the coin, and press it firmly 
all over it, from the centre to its circumferrnee, so as to exclude the air, 
and in doing this it may be necessary to occasionally moisten the tips 
of the fingers with the tongne to prevent the gutta-percha from 
sticking to them. A flat piece of wood may now be laid over the 
gutta-percha, and if this be pressed forcibly by the hands this will 
ensure a perfect impression. After about a quarter of an hour or so, 
the gutta-percha mould may be readily removed from the coin, pro- 
vided that the material has set hard. 

Flwm^Seliig tiM BionkL — Having thus obtained a mould from a 



To8 EIJSCTRO-DEPOSITION OF OOPFKB. 

material which in a non-conductor of electricity, we next proceed to 
give it a conducting surface, without which it would be incapable of 
receiving the metallic deposit of copper which constitutes an electro- 
type. For this purpose, plumbago^ or graphite^* is usually employed. 
To plumbago the surface of the gutta-percha mould proceed as 
follows : — Hold the mould between the fingers of the left hand, face 
upwards ; now dip a soft camel-hair brush in finely -powdered plum- 
bago (which should be of good quality) and briskly brush it all over 
the surface, every now and then taking up a fresh supply of plumbago 
with the brush. Care must be taken to well brush the i>owder into 
every crevice of the impression, and it is better to work the brush in 
circles, rather than to and fro, by which a more pci*fe(*t coating is 
obtained. When properly done, the face of the mould haw a bright 
metallic bistre, resembling a well-polished (that is blackleaded) stovt*. 

In order to prevent the deposit of copper from taking place on the 
upper edge (beyond the actual impression), the plumbago which ban 
been accidentally brushed over this surface should be removed, which 
may be conveniently done by rubbing it off with a piece of damp rag 
placed over the forefinger. The mould is now to be attached to the 
conducting wire by gently heating its longer end in the flame of a 
candle or ignited match, and then placing it on the edge of the mould, 
as far as the circumference of the impression ; by giving it goutlo 
pressure it will become sufficiently imbedded ; the wire must not, 
however, be below the flat surface of the mould. If held steadily 
in the hand for a few moments, or until the wire and gutta-percha 
have cooled, the joint will sety and the mould may then be carefully 
laid aside until the point of junction has set firm. A little plumbago 
must now be brushed over the joint, so as to ensure a perfect eiecirical 
eofinection between the wire and the plumbagoed mould. 

The mould being attached to the conducting wire, must now be 
connected to the zinc by its binding-screws as before (Fig. 54), and botli 
should be immersed at the same time in their respective solutions, but 
this must be done with care, otherwise the mould may become separated 
from the wire. It may be well, in this place, to call attention to certain 
precautions which, if carefully followed, will prevent failure, and 
consequent disappointment, in electrotyping. 

Precautions. — I. The solution of copper to be used in the single-cell 
apparatiis must be kept as nearly as possible in a saturated condition, 
which is effected by keeping the shelf or tray constantly supplied witli 
crystals of sulphate of copper. 2. The superficial surface of zinc 
immersed in the porous cell should not be much greater than that of 
the mould to be copied. 3. The solution should be stirred with a 



* Commonly called blacklead, but in reality carbon in a crude state. 



BBONZINO THE ELECTBOTTPE. IO9 

glass rod or strip of wood before immersing the mould, especially if it 
has been previously used for electrotyping ; if this is not done, the 
deposit may become irregular in thickness. 4. The plumbagpoed 
mould should not be disturbed until its entire surface is covered with 
copper. A few moments after inmiersion, a bright pinldsh red 
deposit of c«pper will be observed at the end of the wire, which in a 
short time will radiate in the direction of the plumbagoed surface, 
and this will gradually extend wherever this conducting medium has 
been spread with the brush, provided the operation has been con- 
ducted with proper care, and an uniform coating obtained. 

Tr«atnMnt of th* Btoc U ' oty y. — A sufficiently stout deposit of 
copper, upon a gutta-percha mould of a small coin, may generally be 
obtained in about two days, or even in less time, under the most 
favourable conditions ; but it is not advisable to attempt to separate 
the electrotype from the mould while the deposit is very thin, other- 
wise the former may become broken in the operation. Assuming the 
deposit to be thick enough, the first thing to do is to cut the end of 
the wire connected to the mould with a pair of cutting pliers or a file, 
after which the superfluous copper may be removed from the outer 
edge by breaking it away with the pliers, taking care not to injure 
the '* type '* itself. The mould may then be placed in hot water for 
a moment, when the electrotype will readily separate from the gutta- 
percha. In order to give additional solidity to the electrotype, it should 
be backed up with pewter solder, which may easily be done as follows : — 
Put a small piece of zinc into about a teaspoonful of hydrochloric acid 
(muriatic acid) ; when the cffcrve8(;ence which takes place has ceased, 
brush a little of the liquid, which is a solution of chloride of zinc, 
over the back of the electrotype, and then apply solder by means of a 
moderately -hot soldering iron, until the entire surface is iinnedy as it 
is called, when a further supply of solder should be run on tf) the 
back to give the required solidity. When this is done, the rough 
edge of the electrotype should be rendered smooth with a keen file. 

Bmmmlng Xbm Hla c tr otyp e. — ^To impart an agreeable bronze ap- 
pearance to the type, it should first be cleaned by brushing it with 
a solution of carbonate of potash (about half a teaspoonful in an oimce 
of water), and applying at the same time a little whiting. An 
ordinary tooth-brush may be used for this purpose, and after brisk 
rubbing the type must be well rinsed in clean water. The bronze 
tint may be given by brushing over it a weak solution of chloride of 
platinum (i grain to an ounce of water) ; when the desired tint is 
obtained, the t3rpe is to be rinsed with hot water and allowed to dry. 
The tone may be varied from a delicate olive -brown to deep black, 
arcording to the proportion of platinum salt emplnycd. A few drops 
of sulphide of ammonium in water, or, still better, a few grains of 



I TO ELEGTBO-DEPOSITION OP COPPER. 

sulphide of barium dissolved in water, will give very pleasing bronxe 
tints to the copper surface, the depth of which maj be regulated at 
will by a longer or shorter exposure to the ^action of the bronzing 
material. Jf a solution of sulphide of barium be used, about 5 grains 
to the ounce of water will produce a pleasing tone in a few seconds. 
It is better to immerse the electrotype in the liquid (previously 
filtered) and to remove it the instant the desired tone is reached, and 
to place it at once in clean water. 

Another method of bronzing electrotypes is by the application of 
plumbago, hj which very pleasing effects may be obtained with a 
little care in the manipulation. The surface of the electrotype is to 
be first cleaned with rotten stone and oil ; the oil is then to be par- 
tially removed by a tuft of cotton wool, and the surface is next to be 
brushed lightly over with plumbago (a soft brush being used) until a 
perfectly imiform coating is given. It is next to be heated to a point 
that would singe the hair of the blacklead brush, and then set aside 
to cool, after which it must be brushed with considerable friction. 
The tint will depend upon the quantity of oil allowed to remain, this 
enabling the surface to retain more of the blacklead, consequently to 
appear of a darker colour. The effect is very fine, and gives high 
relief to the prominent parts, from their getting so much more polish 
than the hollows, thus obviating the disagreeable effect which all 
unbronzcd bassi-relievi produce by reason of their metallic glare. — 
Hockin. 

The beautiful red bronze tone which is seen on exhibition and other 
medals is produced by brushing over the medal a paste composed of 
peroxide of iron (jewellers' rouge) and plumbago, after which the 
article is moderatly heated, and when cold is well brushed until it 
acquires the necessary brightness and uniformity of surface. Equal 
parts of fine plumbago and jewellers' rouge are mixed up into an 
uniform paste with water, and the cleaned medal is then uniformly 
brushed over with the mixture, care being taken not to allow the 
fingers to come in contact with the face of the object. The medal is 
then placed on a stout plate of iron or copper, and this is heated until 
it acquires a dark colour ; it is then removed from the fire and allowed 
to become cold. It is next brushed for a long time, and in all 
directions, with a moderatly stiff brush, which is frequently passed over 
a block of yellow beeswax, and afterwards upon the paste of plum- 
bago and rouge. The bronzing may also be produced by dipping the 
cleaned medal in a mixture composed of equal parts of perchloride 
and pemitrate of iron ; the medal is then to be heated until the.'^c 
salts are thoroughly dry. It is afterwards brushed as before with the 
waxed brush until a perfectly uniform and bright surface is obtained. 

Bronzing may alao be effected by dipping the medal in a solution of 



OOFYIMa FLASTBB OF PABIB MEDALLIONS. Til 

sulphide of ammonium, and when this has dried, the plumbago 
and rouge paste is to be applied as before, and the waxed brush again 
employed. If the object be heated after applying the sulphide of 
ammonium, a black bronze, called '* smoky bronze,*' is pijpduoed, and 
if the high lights be lightly rubbed with a piece of chamois leather 
dipped in spirit of wine, a very pleasing effect of contrast is obtained. 

Moulds of ileaUng "WtOL, — This material is, as we have said, very 
useful for obtaining impressions of seals, signet rings, and other small 
objects. A simple way of taking an impression in sealing-wax is as 
follows : Hold a card over a small benzoline lamp, but not touching 
the flame ; now take a stick of the best red sealing-wax and allow it 
to touch the heated part of the paper, working it round and round 
until a sufficient quantity of the wax becomes melted upon the card. 
Now place the card upon the table, and ha^dng gently breathed upon 
the seal or signet ring, impress it in the usual way. Having 
secured an impression, cut away the superfluous portions of the card 
with a pair of scissors, and moisten the wax impression with a few 
drops of spirits of wine. When this has apparently dried, proceed to 
brush plumbago over the surface, using a camel-hair brush, and when 
perfectly coated, gently heat the end of the conducting- wire and apply 
it to the edge of the sealing-wax, allowing the point of the wire to 
approach the edge of the impression. Now brush a little plumbago 
on the point, and connect the short end of the wire to the binding- 
screw. 

After having obtained several electrotypes successfully, and thereby 
become att fait to the manipulation of the single-cell apparatus, the 
student will naturally desire to extend operations to objects of a more 
important nature, such as medallions, busts, statuettes, and natural 
objects, as leaves, fishes, &c. But before attempting the more elabo- 
rate subjects it will be well to select, for our next operation, one of a 
simpler character, such as a plaster of Paris medallion, an admirable 
model to reproduce in metallic copper. 

Copyiag Flastar of Paris Bladallloiis. — These pleasing works of 
art, which may be obtained at small cost from the Italian image 
makers, are specially suited for the elementary study of tlv,e electrotype 
process, while a cabinet collection of such objects reproduced in copper 
forms an exceedingly interesting record of the manipulator's skill and 
perseverance. There are several materials from which moulds from 
plaster medallions may be obtained ; but we will first describe the 
method of preparing a mould with gutta-percha. To render the 
plaster more capable of bearing the treatment it will have to be sub- 
jected to, the face of the medallion should first be brushed over with 
boiled linseed oil, and this allowed to sink well into the plaster. After 
about two days the oil will have sufficiently dried and hardened upon 



112 ELECTBO-DBPOSITION OF OOPFEB. 

tiie sarface to render the plaster less liable to injury. The medallion 
thus prepared is next to be provided with a rim or collar of pasteboard 
or thin sheet tin^ which must be tightly secured round its circumference 
either by means of thin copper wire, jeweller's ** binding- wire," or 
strong twine. The rim should project about half an inch above the 
highest point on the face of the medallion, and must be on a level 
with its base ; it is then to be laid upon a perfectly smooth surface until 
the moulding material is ready. We recommend the student to prac- 
tise upon small medallions at first ; say about two inches or two inches 
and a half in diameter. 

Vrwpartns tb^ Monld. — A lump of gutta-percha is now to be taken 
of sufficient size to cover the medallion, fill the vacant space up to the 
top of the rim, and project above it. The gutta-percha is to be 
softened in hot water and rolled up into the form of a ball, as before 
directed, care being taken to obliterate all seatru or cracks by repeatedly 
soaking in the hot water and rolling in the hands. It must on no 
account be applied until it is perfectly smooth, and as soft as hot water 
will make it. To give additional smoothness to the surface of the ball, 
it may be lightly rolled round and round, with one hand only, for an 
instant upon a polished table just before being used. Now take the 
ball in one hand and place it in the centre of the medallion ; then press 
it firmly from the centre towards the circumference, taking care not 
to shift it in the least degree. The gutta-percha must be pressed well 
into the cavity, and w^hen this is done, a piece of flat wood may be 
placed on the mass and this pressed with both hands with as much 
force as possible for a few moments, when it may be left until the 
gutta-percha has set hard. If convenient, a weight may be placed 
upon the board after having pressed it with the hands. In about half 
an hour the board may be removed, and the mould allowed to rest 
until quite cold, when the rim may be removed and the mould sepa- 
rated by gently pulling it away from the medallion. As a precaution 
against breaking the plaster medallion, it may be well to suggest that 
its back should be examined, and if it be otherwise than perfectly flat, 
it may be advisable to gently rub it upon a sheet of glass-paper, which 
will readily remove all irregularities from the surface. It is also 
important that the surface upon which the medallion is laid, when 
applying the gutta-percha, should be quito level ; and it will be 
still better if several folds of blotting-paper are placed between the 
table and the medallion before the necessary pressure is given. These 
points being attended to, there is little fear of the medallion becoming 
broken. 

ntunbaffoiiis- — The gutta-percha mould is now to be well plum- 
bagoed, for which purpose a soft brush, such as jewellers use for 
brushing plate and jewellery that has been rouged, may be used, and 



CLEARING THE MOtFLD. II 



J 



tliiH being frequently dipped into tlie plumbago is to be lightly but 
brinkly applied, Hpecial care being taken to well plumbago the hoUotca, 
When it in borne in mind that the most delicate line, even if imper- 
ceptible to the eye, will be reproduct*d in the metallic copy, the 
importance of not injuring the face of the mould will become at once 
apparent. It is also absolutely necessary that the gutta-percha should 
be of the best quality, and since the same material may be used over 
and over again, its first cost is of little consideration. 

daarlas tli« Mould. — The mould being well coated with plum- 
bago, all excess of this material which has become spread over the 
outer edges, beyond the impression itself, must be wiped away, and 
the more completely tliis is done the less trouble will there bo after- 
wards in clearing away from the electrotype the crystalline deposit 
which, under any circumstances, forms around the circumference of the 
electrotype. Indeed, when the student has once or twice experienced 
the inconvenience of having to remove the superfluous copper from 
his electrotypc^s, he will not fail to exert his wits to diminish the 
labour which this involves as far as practicable, by every possible care 
before the mould goes into the copper bath. We therefore urge for his 
guidance, that the removal of the excess of plumbago should be deemed 
one of the important details of his manipulation, and that it should never 
l)e neglected. After wiping away the excess of blacklead, it will be 
found a good plan to place a piece of dry rag on the forefinger and to 
rub it on a common tallow candle, so as to make the part slightly 
greasy ; if now the edge of the mould (carefully avoiding the impres- 
pion) be rubbed with the rag-covered finger, this will eifectually 
prevent the deposit from taking place upon such part ; before doing 
this, however, the conducting wire should be gently heated and im- 
bedded in the edge of the mould as before, taking care that the point 
of the wire touches the extreme edge of the impression, and a perfect 
connection between the wire and the latter must be secured by apply- 
ing a little plumbago with a camel-hair brush or the tip of the finger. 
It is sometimes the practice to apply varnish of some kind to the edge^ 
of moulds, and also to the conducting wire as far as the joining, but 
until the student has thoroughly mastered the prtwcss of cop3dng 
simple objects in the way we have indicated, we do not recommend 
him to employ varnishes ; indeed not until dealing with objects of 
a larger and more elaborate kind. 

The mould being now ready, is to be connected to the binding- screw 
by its wire, and since the material of which it is composed is much 
lighter than the copper solution, the wire must be sufficiently rigid, 
when bent at right angles, as in Fig. 54 to keep the mould \iell down 
in the bath. Being placed in the solution, it must be allowed to 
remain undisturbed until the entire surface of the impression i^ 

z 



114 



ELECTKO-DEPOSmON OP COPPEB. 



covered. In from two to three days the deposit should be of sufRciciit 
thi(ikne.ss to allow of its separation froin tlie mould. 

For copying small medallions of the size referred to, the single-cell 
apparatus shown in Fig. 54 may be used, but for larger sizes or for 

depositing upon seyeral moulds at the 
same time, the arrangement shown in 
Fig. 55 will be most suitable. This 
apparatus consists of a wood box well 
varnished in the interior, and divided 
into two cells or compartments by a 
partition of thin porous wood. The 
larger cell is nearly filled with a satu- 
rated solution of sulphate of copper, 
and the smaller cell with a half-satu- 
rated solution of sal-ammoniac. A 
perforated shelf is suspended in the 
larger compartment to contain a supply 
of crystals of the sulphate. A plate 
of pure zinc, connected by a copper 
conducting wire, is suspended in the 
smaller cell, and the mould connected 
to the opposite end of the wire by 
suitable binding-screws. In this ar- 
rangement neither acid nor mercury are used, and although the action 
is not so rapid as in the former arrangements, it is very reliable for 
obtaining good results. 

Moulds finom Plaster Medallions. — Beeswax is 




-1- 



,-iV '-K.i..-:n: 

lis 




i\ 



II 

II 

\l! 



F'g- 55- 



a very 

useful material for preparing moulds from plaster medallions, the 
following simple method being adopted : — The medallion, instead of 
being oiled as in the previous case, is simply soaked in hot water for 
a short time or until it has become completely saturated. First put a 
sufficient quantity of wax into a pipkin and melt it by a slow fire ; 
when melted, place it on the hob until wanted. Place the medallion 
face upwards in a plate or large saucer, into which pour boiling water 
until it reaches nearly half-way up its edge. In a minute or two the 
face of the plaster '^HLll assume a moist appearance, when the excess of 
water is to be poured out of the plate. A rim of card is now to be 
fastened roimd the edge of the medallion, which maybe secured either 
by means of sealing-wax or a piece of twine. As before, the rim 
should extend about half an inch above the most prominent point of 
the image. The medallion being returned to the plate, the wax is 
now to be steadily poured on to the face of the object, the lip of the 
pipkin being placed near the pasteboard rim and nearly touching it, to 
prevent the formation of sir-bubbles. When the caviiy \a filled up to 



WAX MOULDS FROM PLA8TEB MEDALLIONS. TI5 

the top of the rim, if any air-bubblcA appear they muRt be at onoe 
I'emoved with a camel-hair brunh kept for thi0 purpose, or the feather 
end of a quill, or even a strip of paper may be used. The wax 
must now be allowed to cool as slowly as possible, and in order to 
favour this gradual cooling, a clean, dry jar may be inverted over 
the mould and there left until the wax is quite cold. This precaution 
will tend to prevent the wax from cracking, an event which sometimes, 
but not very frequently, occurs. 

When quite cold, the wax mould will generally separate from the 
plaster by the application of moderate force to pull them asunder. If 
8uch is not the case, however, return the medallion to the plate and 
pour in a littie boiling water. After a few »eeon(W* immersion the 
mould will easily come away. If, however, owing to some irregu- 
larity in the face of the medallion, the mould still refuses to separate, 
plunge the whole into cold water, and, if necessary, use the edge of 
a knife as a lever between the two surfaces and force them asunder. 
If it be found that small portions of plaster adhere to the mould these 
may be carefully picked out with a fine-pointed piece of wood, and 
the mould afterwards very lighUy brushed over with a soft plate brush. 
Should it be found that some particles still obstinately adhere to the 
wax, apply a littie oil of vitriol with a thin strip of wood to the parts 
and set the mould aside for about twelve hours, by which time the acid, 
by attracting moisture from the air, will loosen the plaster, which may 
then be brushed away with a soft brush and water. The mould must 
then be put away to dry, or may be laid, face downward, upon a pad 
of blotting-paper or calico. 

The mould is now to be plumbagoed with a very soft brush, but, 
owing to the yielding nature of the wax, the greatest care must be 
taken not to apply the brush too severely, only sufficient friction being 
used to coat the surface uniformly. It is a good plan to sprinkle a 
little plumbagt) over the face of the mould, and then to work the 
brush about in circles, by which means a well plumbagoed surface 
may readily be obtained. This operation being complet-e, the super- 
fluous plumbago is to be brushed off, and, by blowing upon the face 
of the mould, any plumbago remaining in the crevices may be re- 
moved. The conducting wire is to be attached, as in the case of 
gutta-percha, by gently tcarmiuff the end of the wire ; but, if the 
mould be a tolerably large one (say, 3 inches in diameter) it will be 
well to bend the end of the wire so as to leave a length of about an 
inch or more to be embedded in the edge of the mould, by which 
means it will be more effectually supported than if the point of the 
wire only were attached. The joint must now be well plumbagoed, 
and the excess of this material which has been brushed over the 
edges may easily be removed by scraping it away with a pen-knife. 



Il6 ElfiCTRO-DEFOSinON OP OOPPER. 

The same precautions munt be obAexred with regard to wax-moulds 
as with those made from gutta-percha when immersing them in the 
bath, otherwise they will, from their exceeding lightness, be disposed 
to rise out of the solution. In the case of lai'ge moulds made from 
such light materials they require to be weighted in order to keep them 
beneath the surface of the copper solution, as we shall explain when 
treating of them. 

The stearine composition may be employed instead of wax in the 
preceding operation, but we recommend the student to adopt the latter 
material for copying small medallions, since, with a little care, it will 
answer every purpose, and needs no preparation beyond melting it. 

aconlds from Fiuilile M«taL — There are many ways of making 
moulds from fusible metal, but, for our present purpose, we will select 
the most simple. To obtain an impression of a coin or medal, melt a 
sufficient quantity of the alloy in a small ladle or iron spoon, then, hold- 
ing the coin face downward between the forefinger and thumb of the 
right hand, pour the alloy into the rim of an inverted cup or basin, 
and, bringing the coin within a distance of about 2 inches from the 
molten alloy, allow it to fall Jlat upon the metal and there leave it 
until cold. If, when the metal is poured out, there is an appearance 
of dulness on the surface (arising from oxidation of the metals) a 
piece of card or strip of stiff paper should be drawn over it, which 
will at once leave the surface bright. As the metal soon coola, how- 
ever, this may be more conveniently done by an assistant just before 
the coin is allowed to fall. If no other help is at hand a piece of 
card should be placed close to the cup, so that the moment the metal 
is poured out it may be applied as suggested, and the coin promptly 
dropped upon the cleaned surface of the alloy. A very little practice 
will render the student expert in obtaining moulds in this way, and, 
considering how very readily the material is re-melted, a few failures 
need not trouble him. 

The fusible alloy may also be employed in the form of a paste, but, 
in this case, it is advisable to have the assistance of another pair of 
hands, since, in this condition, it soon becomes solid and therefore un- 
usable. The coin should first have a temporary handle attached to 
it, which may readily be done by rolling a small lump of g^tta-percha 
into the form of a ball ; one part of tliis should now be held in the 
flame of a candle until the part fuses, when it is to be pressed upon 
the back of the coin and allowed to remain until cold. This gutta- 
percha knob will serve as a handle by which the coin may be held 
w^hen the impression is about to be taken. The requisite quantity of 
the fusible alloy is now to be poured upon a piece of board and 
worked up into a stiff paste by means of a flat piece of wood — an 
operation that only occupios a few moments. The instant the alloy 



MOULDS FROM FUSIBLE UETAL. II7 

has assumed the pasty condition the coin, being held by its gutta- 
percha handle, is to be promptly and firmly pressed upon the mass 
until it is sufficiently imbedded in it. In the course of a minute or 
so the coin may be withdrawn, when the mould should present a 
perfect and delicate impression of the original — of course in reverse. 
Should any faults be visible, owing to want of dexterity on the part 
of the operator, the metal must be re-melted and the operation con- 
ducted again. A very little practice will enable the student to pro- 
duce moulds in this alloy with perfect ease. The coin, in each of the 
above cases, should be perfectly cold before appl3ring it to the alloy. 
Large medals are moulded by simply dropping them — a little Hide- 
ways — ^into the metal when on the point of solidification. 

Conneciinff the Mould to the Wire. — When a perfect mould is 
obtained the conducting wire in to be attached, which is done by first 
scraping the longer end of the wire so as to render it perfectly 
clean ; it is then to be held in the flame of a candle, but at a little 
distance from the clean end. The mould being now held in the left 
hand, is to be brought near, but not touching, the flame, and, when 
the wire is sufficiently hot, it is to be pressed against the back of the 
mould, when it will at once become imbedded in it, and in a few 
moments will be firmly set. A small portion of powdered resin 
applied to the spot will assist the union of the two metals. The back 
and upper edge of the mould must now be coated with sealing-wax 
varnish or some other quick -drying varnish, or, if carefully applied, 
paraffin wax (which melts at a very low heat] may be applied by first 
gently heating the mould and touching it ivith a small stick of the 
paraffin wax. It is well, also, to varnish that portion of the conduct- 
ing wire abore the joint which has to be immersed in the copper bath, 
in order to prevent it from receiving the copper deposit. 



CHAPTER VL 

ELECTRO- DEPOSITION OF COPPER (eonUnned). 

Elcctrotyping by Separate Battfn\ — ^Arrangement of the Battery. — Copying 
Plaster Busts. — Guiding Wires. — Moulding in Plaster of Paris. — Copj*- 
ing Animal Substances. — Electro-coppering Flowers, Insects, t&c. — Copy- 
ing Vegetable Substances. — Depositing Copper upon Glass, Porcelain, 
&c. — Coppering Cloth. 

glec U rv iy p i ng by Separate Battery. — In employing the single- 
cell apparatus, we have seen that it is necessary to keep up the 
strength of the solution by a constant supply of crystals of sulphate of 
copper, otherwise the solution would soon become exhausted of its 
mctalf and therefore useless. If we employ a separate battery y however, 
this method of sustaining the normal condition of the bath is unneces- 
sary, as we will now endeavour to show ; but in doing so we must 
directt the reader's attention for the moment to the principles of 
electrolysis, explained in a former chapter. The practical application 
of those principles may be readily expressed in a few words : If, in- 
stead of making the mould, or object to be copied, the tiegalivc elemetitj 
as in the single-cell apparatus, we take a separate battery composed of 
two elements — say, zinc and copper, as in Daniell's batt4»ry, we must 
then employ a separate copper solution or electrolytic bath, in which 
case the object to be deposited upon must be connccttKl to the zinc 
element, as before, but the wire attached to the negative element of 
the battery (the free end of which is the positive eleetrodr) must have 
attached to it a plate of sheet copper, which with the mould must be 
immersed in the solution of sulphate of copper. By this arrangement, 
while the copper is being deposited upon the mould, the ^eet copper 
becomes dissolved by the sulphuric acid set free, forming sulphate of 
copper, which continued action re-supplies the bath with metal in the 
proportion (all things being equal) in which it is exhausted by dcjrasi- 
tion of copper upon the mould. 

Anranffeme&t of the Battery.— At Fig. 50 is shown a DanielFs 
battery, a, connected, by its negative cunduoting wire (proctH^ding 
from the zinc), to tlie mould, b, with its face turned towards the 
copper plate or anode, c. The depositing vessel, n, which may be of 



ASBANOEMEMT OF THE BATTEBY. 



IT9 



glass or stoneware, for small operations, is charged with an acid solu- 
tion of sid^>hate of copper, which is composed as follows : — 

Sulphate of Copper i lb. 

Sulpharic Acid i „ 

Water (about) i gallon. 

The sulphate of copper, as before, is dissolved in a sufficient quantity 
of hot water, after which cold water is 
added to make up one gallon ; the sul- 
phuric acid is then added and the so- 
lution is set aside until quite cold, 
when it is to be poured into the 
depositing bath, which should be quite 
clean. When first placing the mould 
to be copied in the bath, a small 
siuiace only of the copper plate should 
be immersed in the solution, and this 
may be gradually iucreased (by lowering the copper plate) as the 
deposit extends over the surface of tho mould. 

In Fig. 54 is shown an arrangement in which several moulds are 
suspended by a brass rod laid across the bath b, the i*od being con- 
nected to the zinc element of the battery, a, by the wire, x. Strips of 
sheet copper are suspended by a brass rod, r, which is connected by a 
binding-screw to the positive conducting wire, c, of the battery, which 




Fig. 56. 




in the woodcut represents a Danicll coll. In this arrangement, the 
sheet copper, by becoming dissolved in the solution during the electro- 
lytic action, keeps up the normal strength of the bath, which in 
the single-cell arrangement is attained by the supply of crystals of 
sulphate of copper. It may bo well to mention that it is always 
preferable, besides being more economical of time, to deposit upon 



I20 ELECTRO-DEPOSITION OP OOPFEB. 

Hcvcral muuldH at a time in the bath, and thiH can be effected even with 
:ipparatu8 of small dimensionB. The more extensive arrangements for 
ilei)()«iting upon large obje<;t8 by means of powerful battery currents 
will be considered in another chapter. 

Copirins Flaster Busts.— For this purpose, the elastic moulding 
m it°rial is us^^d. Suppose we desire to obtain an electrotyjHJ fnjm a 
small plaster bust, the object must first be well brushed over with 
boiled linsood oil, and then set aside for two or three days to allow ♦he 
t'.urfuce t') harden. In applying the oil, cfire should be taken not to 
allow it til touch the lower surface surrounding the orifice at its base, 
over which a pi ere of stout paper must be pasted to prevent the 
elastic material from ciiiLriiig the cavity, but before doing this partly 
fill the cavity with sand, to increase its weight. The bust is next to be 
suspended, upside down, by means of twine or thin copper wire, 
inside a jar sufficiently wide and deep to leave at least half an inch all 
round and at the bottom. When thus placed in its proper position, 
the elastic composition (p. 105), having been previously melted, is 
poured in, and if any air-bubbles appear, thsse must be removed with 
the feather of a quill, when the vessel is allowed to rest until the 
composition is quite cold. 

The vessel is now to be inverted, when the solidified mass and the 
Imbedded bust will gradually slip out. To facilitiite this by prevent- 
ing the composition from sticking to the jar, it is a good plan to 
slightly oil the interior of tlie vessel in the first instance. Having 
removed the moidd, it must now be separatt^l from the plasttT bust. 
This is done as follows :— First place the mould in an eriHt )x>8ition, 
base downward, then, witli a thin knife, make an incision from the 
top to the base of the mould, at the back of the bust. The mould may 
now be readily opened where the incision has In'cn nuido, and while 
being held open, an assistant should be at hand to gently remove the 
bust, when the mould, owing to its plasticity, will readily close itself 
again. It must next be secured in its proper position by l)eing care- 
fully bound round with a bandage of tape. The mould is then to be 
inverted, and returned to the jar. A sufficient quantity of wax ie 
now to be melted at the lowest temperature that will liquefy it, other- 
wise it will injure the mould ; it is then to be poured into the mould 
and allowed to rest until thoroughly cold. A\Tien cold, the elastic 
mould is to be again removed from the jar, and Kcpanited by untyinjf 
the bandages from the wax-C4isting. This latter must now hv well 
plumbagoed, a conducting wire uttached, and the joint coated with 
plumbago as before dirc»<ted. Since it will be difficult, howt»vcr, tn 
obt^iin an uniform deiK>sit over such u conipairatively lar^rc surf arc, it 
will Ih) ne<;es.sark' to apply t/nidiuf/ wires, as they are c^ilieil, and 
to which we must now direct special attention. 



OOPTINO PLABTEK BUSTS. IZl 

Gaidiny iriri-'. — The applicatiun of additional wireti. to fiicilitste 
the depositiou of copper in the cavities, or undemut nurfacen. of 
idouMh van first introduecd by Dr. Leeiwii. A suMtient number of 
lengthx of fine brasB wire nre twiiitcd firmly ntunil the main conduct- 
ing wire, at a nliort diatance from ita junction witli tiie mould, 
and thene. one by one. are bent in such a way that tlieir extreme 
point* may rent, HiiIiI/i/, upon the hollow Burfacefl of the mould, 
whereby tie current is diverted, t« a certain eiteut, from the main 



Fig. 58. 

wire to tbe cavitim or hoUowH, whic^h arc lemt favourably uituat^ tor 
rccei^'ing' Ihe metallic deposit than the plane Hurfaien. The applica- 
tion of guiding' wires is more eBjieeially necoswiry when the object to 
be copied is of considerable dimensions ; the principle of their 
orrangetnont is shown in Fig. 5S. 
The mould, prepared as doKiibed, is to be put in connectioa with 



122 ELECTBO-DEFOBmON OF COPPER. 

the battery, by suspending it from tlie negatiye conducting-tod, and 
then gently lowered into the coppering bath. In the present case only a 
moderately stout deposit, or * * shell, * * of copper will be necessary, since, 
as we shall explain, this dex)06it will, in the next operation, act the 
part of a mouldy in producing a fac-simile of the original. When 
a perfect coating is obtained, of sufficient thickness to bear handling, 
it ifl to be removed from the bath, rinsed, and allowed to drain. It 
must then be heated sufficiently to melt the wax, which is allowed to 
run into any convenient receptacle, and the interior of the electrotype 
(which now represents a mould) must be cleansed from all adhering 
wax, by continuing the heat until the last drop ceases to flow. It must 
then be treated with spirit of turpentine, with the application of 
moderate heat, to dissolve out the remaining wax, the operation being 
repeated so as to entirely remove all traces of the wax. 

The next operation consists in depositing copper upon the interior oi 
the copper mould, which may be readily done in the following way : — A 
small quantity of sweet oil is first to be poured into the mould, which 
must be moved about so that the oil may spread all over the sur- 
face ; it must then be tilted over a vessel to allow the oil to run out, 
and next placed upon several folds of blotting-paper before a fire, for 
several hours, until the oil ceases to flow. The mould must now be 
carefully examined, and if any '^pin-holes," as they are called, are 
visible, thene must be stopped by melted wax dropped upon each spot 
upon the outside of the mould. 

The mould is now to be placed in a jar, in an inverted position, and 
held in its place by a padding of paper or rag, wedged around 
its base. The negative electrode (or wire connected to the zinc of the 
biittery) is now to bo connected to the mould, which may conveniently 
be done by soldering. A strip of stout sheet copper, attached to the 
iiohitivc electrode, is then to be suspended in the cavity of the copper 
mould, but not allowed to touch any part of it, and in this position it 
must be fixed securely, which may be conveniently done by a piece of 
wood laid across the orifice of the mould. The mould is now to be 
filled with the copper solution last mentioned, and the battery is then 
to be set in action. In order to obtain a good solid electrotype from 
the copper mould, it will be necessary to renew the copper plate, or 
anode, from time to time when it becomes worn away, unless it be of 
pufficient thickness to render such renewal unnecessary. The strength 
of the battery must also be well kept up by renewing the acid solution 
in the porous cell. When a deposit of sufficient thickness ix obtained, 
the conducting wires may be diwonnetjted, the copper solution poured 
out, and the interior rinsed with water. 

The next operaticm is to remove the shell of copper constituting the 
mould, which \b done by breakittg it away — beginning at the base — 



MOULDINO IN PLA8TEB OF PABIS. I23 

• 

with a pair of pliers. When the first layer of metal hoH been lifted 
from the underlying deposit, the remainder may generally be peeled 
off with but little trouble, when the electrot}i)e proper will be 
exhibited, and if successfully accomplished it will amply reward the 
operator for the trouble and care devoted to its production. The 
student should not, howev^, undertake the manipulation of the 
elastic moulding composition until he has acquired a skilful aptness in 
the simpler processes of electrotyping. It may be well to mention 
that the elastic composition may be re-used several times, provided it 
has been kept in a covered vessel, to exclude it from the action of 
either a moist or a very dry atmosphere. 

Mcmldlng in Flastar of Favts. — ^This material, especially fur 
copying natural objects, such as leaves, ferns, fishes, &c., is exceed- 
ingly useful, and we will, as in former instances, first give the more 
simple method of applying it, so that the student may have no diffi- 
culty in its manipulation. To obtain a plaster mould from a coin or 
medal, for example, first oil the face of the object slightly by applying 
a single drop of oil, with a tuft of cotton wool, and with a fresh piece 
of wool gently rub the coin all over, so as to leave but a trace of oil on 
the surface, the most trifling quantity being sufficient to prevent the 
adhesion of the plaster to the original. A rim of card is now to be 
fixed roimd the medal, to form a receptacle for the plaster. A little 
cold water is then to be poured in a cup, or other convenient vessel, 
and a small portion oijine plaster dropped into the water. The excess 
of water is now to be poured off and the plaster briskly stirred with a 
spoon. Now fill the spoon with the plaster (which should be about the 
consistency of cream) and pour it carefully over the face of the medal. 
If any air-bubbles appear, disperse them with a feather or camel-hair 
brush, which should be immediately after plimged into cold water, ho 
that the plaster may easily be removed, and the brush thus left ready 
for future use. In about half -an -hour or so, the coin and mould may 
be detached, and the latter should then be placed in a moderately 
warm oven until dry. When perfectly dry, the face of the mould is 
to be well painted over with boiled linseed oil, repeating the operation 
several times ; or the mould may be saturated with wax, by pouring a 
little of this substance, in a melted state, over the face of the mould, 
and then placing it in the oven until the wax becomes absorbed by the 
plaster. When cold, the mould must be plumbagoed in the ordinary 
way, and a copper conducting wire attached by twisting the wire 
roimd its circumference, and forming a connection with the plumba- 
goed surface by means of a drop of melted wax, afterwards brushed 
over with plumbago. That portion of the wire which surroundn the 
mould should be coated with vaniLsh to prevent tlic copper from being 
deposited upon it. The superfluous plumbago should, as in the 



124 ELECTBO-DEPOSITION Of COPPEB. 

former caiies, be removed, by scraping it away with a knife, leaving 
the connection, of course, untouched. The mould is now ready for 
the depositing bath, into which it must be gently lowered, so as to 
avoid breaking the connection between the conducting wire and the 
plumbagoed surface, a precaution which must in all similar cases be 
strictly observed. 

GepyUie Ammal SntMrtane^s.— Suppose we desire to obtain an 
electrotype of a small fish (the scaly roach being very suitable), for 
example. The object is first brushed over lightly with a little linseed oil ; ^ 
we next mix a sufficient quantity of plaster of Paris into a thinnish 
paste, and pour this in a shallow rim of metal or stout cardboard placed 
upon a piece of glass or sheet of paper, previously rubbed over with a 
little oil or grease ; before the plaster has time to aet^ the fish is to be 
held by its head and tail, and laid on its side upon the paste, using 
sufficient pressure to imbed one half of the fish. To assist thisy the 
soft plaster may be worked up or guided to its proper places by 
means of a knife-blade, care being taken to avoid spreading the plaster 
beyond that part which is to form the Jirst half of the mould. The 
plaster is now allowed to set hard, which occupies about half an hour. 
We next proceed to mould the second half of the fish. A small brush, 
say a painter's sash tool, is dipped in warm water, and then well 
rubbed over a lump of soap ; this is to be brushed all over the plaster, 
but avoiding the fish, and the soap and water applied several times to 
ensure a perfect coating. A rim of greater depth, say f of an inch 
deeper, must be fixed round the mould, in place of the former 
rim, and a second quantity of plaster made into a thinnish paste, as 
before, which must then be carefully poured over the fish and upper 
surface of the mould, taking care not to let it flow over the rim. lliis 
second batch of plaster should be sufficient to form a thick half mould, 
as in the former case, otherwise it may break when being separated 
from the first half mould. 

When the plaster has set quite hard, the two moulds may be sepa- 
rated by gently forcing them asunder, the soap and water having 
the effect of preventing the two plaster surfaces from adhering, while 
the oil applied to the fish also prevents the moulding material from 
sticking to it. When the two halves of the mould are separated, the 
fish is to be carefully removed, and the plaster moulds placed in a 
warm, but not very hot, oven, and allowed to become perfrcilt/ dry. 
They are then to be placed faced downwards in a plate or other shallow 
vessel, containing melted bees-wax, and allowed to remain until 
saturated with the material, especially on the faces of the moulds ; 
these are now allowed to become quite cold, when they are ixai^y to 
receive a coating of plumbago, which must be well brushed into every 
part of the impression, until the entire surfaces present the bright 



COPYING ANIMAL SUBSTANCES. 



125 



metallic lustre of a well -polished iire-stove. The conducting wire 
must now be attached^ which ntay be effected in UiiH way : Bend a 
piece of stout copper wire in the form shown in Fig. 59, and pass the 
mould tmder the hook at r/, and beneath the coil of the wire at b ; the 
shorter end of wire at a should just touch the edge of the im- 
pression, near the mouth or tail of the fish. The wire thus adjusted 
must be secured firmly in its place, by being bound to the mould with 
thin copper wire. Before placing the conducting wire in its position, 
as above described, it wiH be advisable to wipe away all superfluous 
plumbago from the face of the mould, carefully avoiding injury to the 
impression, and when the conducting wire is adjusted, it is a good 
plan to coat the wire at all parts but the extreme point at a with 
varnish, or melted parafi&n wax, to prevent tlie copper from 
becoming deposited upon it. The end of the wire at n 
must be put in metal! ic contact, so to speak, with the plum- 
bagoed impression, by brushing a little of that substance 
over the point of junction. Thus prepared, the long end of 
the conducting wire is to be connected to the negative pole of 
the battery, and the mould gently immersed in the batli, the 
copper anode previously being suspended from the positive 
electrode. 

The second half mould may now be treated in same way 
as the above, and when two perfect electrotyx>es, or ahellsy 
are obtained, the superfluous copper should be removed by 
aid of a pair of pliers and a file ; when this is done the 
inner edges of each electrotype may be Untied, by first 
brudhing a little chloride of zinc round the edge, and then 
passing a soldering iron, charged with pewter solder, over 
the surface. When the two halves of the fish are thus 
prepared, they may be brought together and held in posi- 
tion by means of thin iron ** binding wire." The flame of 
a spirit-lamp or ^ blow-pii)e flame may now be applied, 
which, by melting the solder, will soon complete the union, when a 
perfect representation of a fish will be obtained. This may after- 
wards be bronzed, gilt, or silvered by the processes described here- 
after, and, if desired, mounted upon a suitable stand. 

The elastic moulding material may also be used for copying animal 
substances; in this case, one half of the fish must be imbedded in 
moulding sand ; a cylinder of thin sheet tin, bound together with fine 
copper wire, or by soldering, is then placed round the. sand, so as 
to enclose it, and the sand is made as level as possible, by gently 
pressing it with any convenient instrument. The melted elastic 
material is now to Tje poured into the cylinder, which should be about 
two inches higher than the highest part of the object, until it nearly 




FifiT- 59 



126 ELECTRO-DR POSITION OP OOPPER. 

reaches the top ; it is tlien allowed to rent " for at least twelve hours* 
when the metal rim ia to bo removed and the mould withd^aw^l ; the 
obje:t is next to Ik? liberated from the mould, and the other half 
moulded in the same way. The wax and stearine composition is 
to be poured into each half mould, and from the models thus ob- 
tained plaster moulds may be procured in the same way as from the 
natural object, but in this case the wax models must be well brushed 
over with plumbago before being embedded in the plaster. Since 
electrotypes of fishes look exceedingly well as wall ornaments, it will 
be only necessary, for this purpose, to obtain an electrotype of one 
half of the fish, which may, after trimming and bronzing, be cemented 
to an oval board, stained black and polished, and, if desired, mounted 
in a suitable frame. 

Bleetro-Copperlns Flowars, Xnseets, Ac — Fragile objects, to 
which the ordinary methods of plumbagoing could not be applied, 
may be prepared to receive a deposit of copper in the sul- 
phate bath by either of the following methods : — 

I . The object, say a rose-bud or a beetle, for instance, 
is first attached to a copper wire ; it is next dipped in a 
weak solution of nitrate of silver (about forty grains of the 
nitrate dissolved in one ounce of distilled water), and after 
being allowed to drain, but before it is dry, it is to be ex- 
posed to the vapour of phosphorus under a bell-glass. To 
produce the vapour a small piece of phosphorus is dissolved 
in a little alcohol ; this is poured into a watch-glass (chemi- 
cal ** watch-glasses ** are readily procurable), which is then 
placed in a plate containing hot sdnd. The object being 
O fixed by its wire in such a position that it cannot shift, the 

Fig. 60. bell-glass (an ordinary fern-glass will answer admirably) 
is to be placed over the whole, and allowed to remain undis- 
turbed for about half an hour. The sand should not be hot enough 
to endanger the bell-glass. By this process, the silver of the nitrate 
is reduced to its metallic state, causing the object to become a 
conductor of electricity ; it is then ready for the coppering bath, 
in which it must be immersed with great care. Since very light 
objects will not sink in the solution bath, it is a good plan to form a 
loop in the conducting wire, as shown in Fig. 60, to which a piece of 
strong sUk thread or twine, having a small leaden weight connected to 
the opposite end, may be fastened, as in the sketch. By this simple 
contrivance light objects sxtdi floating monM»^ as those made of gutta- 
percha, wax, &c., may be easily sunk into the bath, and retained 
therein until sufficiently coated. 

2. The most cflPcctive application of phosphorus for the above pur- 
pose consists in dipping the object in a solution of phosphorus in 



ELECTRO-COPPEBING FL0WEB8, ETC. 12 J 

bisulphide of carbon. This highly volatile and inflammable subatance 
dlHHolves phosphorus very freely; the solution, known as "Greek 
fire," is a most dangerous compound to handle, and if any of it 
drop upon the skin it may produce sores of a serious nature ; more- 
over, if it be incautiously allowed to drop upon the clothing, or upon 
the floor, it may afterwards ignite and do much mischief. In employ- 
ing the solution of phosphorus, therefore, the greatest possible care 
must be observed. The object, being attached to a wire, is dipped into 
the solution, and after being allowed to rest for a few seconds, is next 
immersed in a weak solution of nitrate of silver, and afterwards allowed 
to dry in the light. If the object, after being dipped in the phosphorus 
solution, be allowed to remain in the air for more than a few seconds 
before being placed in the nitrate solution, it is very liable to become 
ignited. The solution of phosphorus is prepared by dissolving a small 
portion of the substance in bisulphide of carbon, about one part of 
phoNphoms by weight being sufficient for the purpi>8e in 20 of 
bisulphide of carbon. 

3. A safer method of producing a conducting surface on tliese objects 
is to employ an alcoholic solution of nitrate of silver, made by adding 
an excess of powdered nitrate of silver to alcohol, and heating the 
mixture over a hot- water bath. The object is to be dipped in the 
warm solution for an instant, and then exposed to the air for a short 
time until the spirit has evaporated. If now submitted to the fumes 
of phosphorus, as before described, the fllm of nitrate of silver soon 
becomes reduced to the metallic state, when the object is ready for the 
coppering bath. 

To render non -metallic substances conductive, Mr. Alexander 
Parkes introduced the subjoined ingenious processes. 
I. A mixture is made from the following ingredients : — 

Wax or tallow i ounce 

India-rubber .1 drachm 

Asphalte x ounce 

Spirit of turpentine xi fl ounce 

The india-rubber and asphalte are to be dissolved in the turpentine, 
the wax is then to be melted, and the former added to it and in- 
corporated by stirring. To this is added one ounce of a solution of 
phosphorus in bisulphide of carbon, in the proportion of one part of 
the former to fifteen parts of the latter. The articles, being attached to 
a wire, are dipped in this mixture ; they are next dipped in a weak solu- 
tion of nitrate of silver, and when the black appearance of the silver is 
fully developed, the article is washed in water ; it is afterwards dipped 
in a weak solution of chloride of gold, and again washed. Being now 
poated with a film of gold, it is ready for inmiersion in the copper bath. 



rsS EL.ECTR0-DEP08ITT0N OP COPPER. 

2. In this process, the solution of phosphorus is introduced into tho 
materials used for making the mould, thus :— 

Wax and deer's fat, of each .... J pound 

Melt together and then add : — 

Phosphorus . . . . .10 grains 

Dissolved in bisulpliide of carbon . . . 150 „ 

The wax mixture must be allowed to become nearly cool, when the 
phosphorus solution is to be added very carefully, through a tube 
dipping under the surface of the mixture ; the whole are then to be 
well incorporated by stirring. Moulds prepared from this comp)sition 
are rendered conductive by being first dipped in a solution of nitrate 
of silver, then rinsed, and afterwards dipped in a weak solution of 
chloride of gold, and again washed, when they are ready for the 
coppering solution. 

CopyinuT Vegetable flnbataneas. — The leaves of plants, seaweeds, 
ferns, iS:c., may be reproduced in electrotype, and form very pleasing 
objects of ornament when successfully produced. If we wish to 
copy a vine-leaf, for example, the leaf should be laid face down- 
wards upon a level surfac*e, and its back then covered with several 
layers of thin plaster of Paris until a tolerably stout coating is given ; 
the leaf is then to be inverted and embedded in a paste of plaster, 
care being taken not to allow the material to spread over the face of 
the leaf. When the plaster has become hard, finely powdered plum- 
bago is to be dust-ed over the entire surface from a muslin bag. A 
rim of pasteboard, slightly greased on one side, is now to be fixed 
round the outer edge of the plaster, and secured by a piece of twino. 
To render this more easy, the plaster may be pared away with a knife, 
80 as to leave a broad flat edge for the card rim to rest against. 
Melted wax is now to be poured into the pasteboard cylinder thus 
formed, in sufiicient quantity to make a tolerably stout mould. "VVTien 
thoroughly cold, the rim is to be removed and the mould liberated 
carefully. It is then to be plumbagoed, connected to the negative 
electrode of the battery, and immersed in the copper bath. The 
clastic material may also be employed in making moulds from vege- 
table objects. 

D«poBitiiiff Copp«r upon Olaas, Foreelaln, ftc — The article 
should first be brushed over with a tough ramish, such as copal, or 
with a solution of gutta-percha in benzol ; when dry it is to be 
well plumbagoed. In some cases it may be necessary to render the 
surface of the glass rough, which is effected by submitting it to the 
fumes of hydrofluoric acid ; this is only necessary, however, when the 
vessel is of such a form that the deposited copper might slip away 



DBFOSITINa COPPFIi UPON OLABS, ETC. 1 29 

from the glass. Poroelain capsules, or evaporating dishes, may receive 
a ooating of copper at the ontside, bj varnishing this surface, extend- 
ing the coating to the upper rim of the vessel, then applying the 
plumbago and depositing a coating of copper of sufficient thickness. 
Another and more effectual way of obtaining an adhesive deposit 
upon glass or porcelain is to send the article to a glass or poroelain 
gilder, and have gold burnt into its surface, and then depositing upon 
the gold coating in the usual manner. MM. Noualhier and Prevost 
patented a process for producing a conducting surface upon glass or 
vitreous substances, which consists in first coating the object with var- 
nish or g^ld size, and then covering it with leaf copper. By another 
method they triturated bronze powder with mercury and common salt, 
and then dissolved out the salt with hot water, leaving the bronze 
powder to settle. When dry, this powder is to be applied to tlie 
varnished object in the same way as plumbago. For this purpose, 
however, Bessemer bronzes, which are exquiRitdy impalpable, and 
produce a very good conducting surface, may Im? employed with or 
without being mixed with plumbago. 

Copp«iiiic; Clotb. — In 1843, Mr. J. Schottlaonder obtained a patent 
for depositing either plain or figured copper upon felted fabrics. The 
cloth is passed under either a plain or engraved copper roller, immersed 
horizontally in a sulphate of copper bath, containing- but little free 
acid. The dejwsit takes place upon the roller as it slowly revolves ; 
the meshes of the cloth are thus fiUod with metal, and the design of 
the roller copied upon it. The coppered cloth is slowly rolled ofl:' and 
passes through a second vessel filled with clean water. Tlic roller 
is previoualy prepared for a non-adhesive deposit. 



K 



CHAPTER VIL 

ELECTRO-DEPOSITION OF COPPER {continued). 

Electrotyping Printers' Set-up Type. — Plambajping the Forme. — Prepara- 
tion of the Mould. — Filling the Case.— Talcing the Impression. — The 
Cloth. — Removing the Forme. — Building. — Plumbagoing the Mould. — 
Knight's Plumbagoing Process. — Wiring. — Hoe's Electric Connection 
Gripper. — Metallising the Moulds.— Adams' Process of Metallising 
Moulds. — Quicking. — The Depositing Bath. — Batteries. — Treatment of 
the Electrotype. — Finbhing. — Electroiypini; Wood Engravings, &c, — 
Tin Powder for Electrotypin^^ 

Of aU the purposes to which the art of electrotyping is applied, 
none is of greater importance than its application to letterpress print- 
ing and the copying of wood engravings to be printed from instead of 
from the wooden blocks themselves. Although this latter branch of the 
art is very extensively adopted in this country, in the reproduction of 
large and small engraved blocks for illustrated works and periodicals, 
newspaper titles, &c., the application of electrotyping as a substitute 
for stereotyping in letterpress printing has not, as yet, attained the 
dignity of an art in England. In America, however, the art of re- 
producing set-up type in electrotype copper has not only acquired a 
high state of development as a thoroughly practical branch of electro - 
deposition, but it has almost entirely superseded the process of stereo- 
typing. There are several reasons why this art has boon more fully 
developed in tho States than here. In tho first place our transatlantic 
kindred are more prompt in recognising and adopting real improve- 
ments ; they are less mindful of cost for machinery when the object to 
be attained is an important one ; they are not so munh under tho 
influence of so-called " practical men" as to ignore scientific help ; 
finally, they do not wait until all their competitors have adopted a 
procass before they run the risk of trying it for themselves. 

During the pa.st few years wo have been much impressed by the 
extreme beauty of the American printing, and the exquisite brilliancy 
of their eng^ving^. Being printed from copper surfaces, the ink 
delivers more freely than from stereotype metal, while, we believe, a 
smaller amount of ink is required. Again, the Americans extensively 
employ wood pulp in the manufacture of their paper, and this material 
being less abaorbant than cotton -pulp, causes the ink to remain on the 



ELBCTBOTTPINO FRINTEBS* SBT-UP TYPE. I31 

mrfaee rather than to sink into the substance of the paper — a fact 
which was established by the author's father, the Ute Mr. Charles 
Watt (the inventor of the wood-paper process), when it was first 
exhibited in London in the year 1853,* in the presence of the present 
Earl of Derby and many scientific men and representatives of the 
prcsH. 

With a full belief that the American system of clectrotyping, as 
applied to letterpress printing, will eventually be adopted in this 
country — at first by the more enterprising members of the printing 
community — ^we propose to explain as concisely as the subject will 
admit the method which has been practically adopted in* the United 
States, and we have to thank the distinguished firm of R. Hoe and 
Co., of New York, the well-known manufacturers of printing and 
clectrotyping machinery, for much of the information we desire to 
convey, as also for their courtesy in fumisliing us, at our request, 
with electrotypes of their machinery for the purposes of illustration. 
We are also indebted to Mr. Wahl t for additional information on 
this subject. 

"As applied to letterpress printing, electrotyping is strictly an 
American art." This is the claim put forward by the firm referred 
to, and we freely acknowledge the fact. We gave our cousins the art 
of electrotyping, and in exchange they show us how we may apply it 
to one of the most useful of all purposes — the production of gx)od 
printing from a more durable metal than either ordinary type or 
stereotype metal. 

Blectrotypins Fttntem' 8et-iip Tjrpo- — In pursuing the art of 
electrotyping, as applied to letterpress printing, the compositor , electro- 
typer, and mounter must work with one common object, each having a 
knowledge of what the other requires to perform his part of the work 
properly. In carrying out the operation on an extensive scale, the 
dex)ositing room should be on the ground floor, owing to the weight 
of the vats, and the flooring should be cemented and well drained. 
The apartment should be well lighted, and provided with an ample 
supply of water. The depositing vats may be of wood, lined with 
pitch ; and where a magneto or dynamo-electric machine is employed, 
this should be fixed at such a distance from the vats as not to be in 
the way, but at the same time to be as near to them as possible with- 
out inconvenience. 

* Manufacturers in this country refused to adopt this process. It was, 
however, *' taken up *' in America in the same year, where it has been worlced 
ever since. It is now used in this country to some extent, as also in many 
other parts of the world. 

t '* Galvanoplastic ManipulatioDB." By W. H. WahL 



132 ELEOTBO-DBFOBinON OF OOVPMSL 



Txtipurlng ttaA Fonaas. — ^When the formes, or pages of set-np 
type, have to be electrotyped, it is nedessarj that great oare should be 
exercised in selecting the types, roles, &o., m justifying the same, and 
in locking-up the forme. When the art of eloctrotyplng comes to be a 
recognised substitute for stereotyping, it is probable that some modi- 
fications in the structure of printers' type may be made to suit more 
fully the requirements of the eleotrotyper than the ordinary type. 
The following suggestions are given relative to the composition of the 
type for reproduction in electrotype, and these should be well under- 
stood by those who may hereafter be called upon to produce electro- 
types from printers' formes. 

Compositioii. — ^Every quadrat, space, lead-slug, reglet, or piece oi fur- 
niture should be high. Some leads have one or both edges bevelled ; but 
even though the bevel is small it is sufficient to cause considerable 
trouble, and such leads should not be used in moulding, as the wax is 
sure to be forced into the space of the bevel, to be broken off, and to 
require extra labour in distributing the type, besides making it neces- 
sary to scrape the wax from the leads before they can be used again. 
So far as possible, use thick rules and those having a bevel on each 
side of the face. Thin rules make so small an opening in the wax 
that there is great difficulty in blaokleading the mould, and in the 
bath the copper may bridge across a small opening, leaving the face 
and sides of the rule uncovered, or at most with but a thin, imperfect 
deposit that is useless. For this reason, type having considerable 
bevel, is best for electrotyping. English type has more bevel than 
American. Bevelled rules also make impressions in which the hairs 
of the blaokleading brush can penetrate more deeply. Type-high 
bearers, or guards, about ^ of an inch thick, should be put around 
each page, and scattered through blank spaces, to prevent the wax 
from spreading while the forme is pressed in it, and also to facilitate 
the operation of '* backing." If there are several pages in a forme, 
separate them by two guards ; one g^uard does not give sufficient room 
to saw between the pages and leave enough of the bearer to protect 
the edges of the plate in '* shaving." When the matter occupies but 
a {wrtion of a page, or the lines are shorter than the full width of the 
page, as in poetry, an em dash or a letter should be placed bottom up 
in each comer of the page, as a guide to the finisher in trimming the 
the plate. When the folio is at one comer, that will answer for one 
of the g^des. Ail large blanks, chapter heads, and lines unprotected 
by other matter, should have type-high bearers so placed as to guard 
the exposed parts from injury. 

^ooklnff-iipto— The formes must be looked much tighter than for 
printing, for, in order that the mould shall be perfect, the wax must 
enter and fiU solidly all the interstioes of the f onne. This requires 



KLBCTROTTPINO FBINTEBS' SET-UP TTOB. 133 

great pfeesurei and Khe movement of the wax canaed hy the entering 
of the type in taking the impression^ or mould, is very likely to dis- 
place any portions of the forme that may be loose. A proof should 
always be taken after the foime is looked up for the foundry, 
and both should be examined to make sure that no part has shifted in 
driving the quoins. Sometimes the matter is set -with high spaces but 
low leads, or vice vertd, or low spaces but no leads ; frequently copper- 
faoed and white-faced type are used in the same forme. None of 
these combinations should be allowed, but the whole forme should be 
either high spaces and high leads or low spaces and low leads. In 
offices having no high quads, &c., low material must be used ; but 
greater care is necessary in preparing the forme, more labour required 
of the electrotyper, and the plate is much less satisfactory than when 
high material is used. Woodcuts which are locked up with the type 
must be perfectly cleaned with naphtha or benidne, and dried 
thoroughly before the forme is blackleaded, and great care must be 
taken not to clog the fine lines of the engraving. 

Moulds should not be taken from electrotype outs, since much better 
ones can be obtained direct from the woodcut. 

O o n fc t to g tiM Xattar. — ^When necessary to make alterations in 
electrotype plates, the matter for corrections i^ould be setup and elec- 
troiyx)ed, but the compositor should separate each correction by a space 
about a pica, in order that there may be room to saw between them. 
If the alteration is but a single letter or short word, it is usual to 
solder the type to the plate. By setting up corrections in their regular 
order, the labour and cost of plate alterations may frequently be much 
)!educed. 

The above technical hints will aid the electrotyper into whose hands 
a printers' forme may be placed for reproduction in electrotype 
copper. 

Tlaakhagolng tli« FoniM. — ^The forme of type must first be 
cleansed from printing-ink, if very dirty, either with potash ley or 
benzine ; or, if not very dirty, with water distributed from a rubber 
pipe with rose sprinkler, after which it must be dried. The forme is 
next to be well brushed over with plumbago, to prevent the wax from 
sticking. This is applied with a soft hand-brush, the plumbago 
being made to penetrate every crevice. In doing this, great care 
must be taken not to fill up the fine lines of the forme with the 
plumbago. 

Vsroparatlon of tbe SOonUL — ^For this purpose a moulding ease 
(Fig. 6i) is employed, which is a flat brass pan about three-sixteenths 
of an inch in depth, with two flanges, which fit into the clamps of the 
moulding press. This is fitted with an *^ electric connection gripper." 
The tnoulding eomposiiion consists of the best pure yellow beeswax, to 



'34 ELxcTBO-DapoemoN op oopteb. 

-wMoh ig added from five to twenty per cent, of yirgia tnrpentine, to 

prevent it from crsckiiig. If the temperature of the apartment ix 

from Q0° to 9j° Fahr., the wax ma; not 

require any addition. The compoaiUon 

Bbould be melted b; steam heat.* 

nuins ttM Caa*.— The moulding case 

haring been slightly warmed, on the ifeom- 

heaiinff table, o, Pig-. 6?, la placed on tho 

eate-filling table, b, truly levelled, and tho 

melted wax, contaitiod in the Hmall jacketed 

pan, ia poured intu it n-ich a clean iron 

or ot^lper ladle, great care being token \i> 

run the wax entirely over the case while 

it is hot, so that it may not, by cooling too 

quickly in any part, oaose irregnlarities. 

Fi(j. 5i.-MouUllng Caw. .j-j^^ air-bubblea which rise to the auriaco 

must bo* touched with the healed buildiag-iroii. Fig. 64, when they will 

disappear. If, on cooling, the wax ahrinks away from tho cdgee 

of the case, it can be re-melted (here by running the point of the 

healed bnilding-iron over it, bo as tn close up any fiasnre. When 

cool, the wax ahonld present a gnuxith, oven surf aoe ; if this be not 



Fig. 61.— Case-fiHiog and StMm-heatirig Tables. 

tlie case it in useless, and most be put back into the pot and te- 
meltcd. llie whole surface ix now to 1k' cnrefiilly niid tlioniuffhiy 
niblwd ovcrwith plumbago, and j-ili.-linl with s. .ft hand -bnish ; whcii 
this is cffwstcil, tlie wax is ready to rei'cive tbe impre-sion. 

TaklDg tlw Improaaliin, or ggonliUng. — Fur this purpnxoton- 
siderablc and nteody girewiure is necessary, and Ihix is given either by 

* Gut^perchs is seldom used ia America for making mouldi* 



ELECraOTYPING PRIWTEBB SET-UP TYPE. 135 

means of b, hydraulio presa, or bj tlie " toggle " press, one fonn ot 
which, OS manufactured by Hoe & Co, , is shown in ¥ig. 63. This 
form of pre«8 congiats of a masBive frame, having a planed bod, otbt 
which is a fixed head. There is a projecting table, on which the 
forme and case may be oiranj^ before sliding tliem to receive the 
prcBaure, which In put upon them by raiaing the bed by means of the 
hand wheel and screw, and the two toggles. Id this way enormoiIB 
is obtained wiUi bat little manual exertion. 



^g- 65.— Toggle Press for Electrotype Mould. 

Vha Oloth.^ — Where low spaces arc used, it is customary to make a 
preliminary impression with a thin sheet of gutn cloth interposed ; 
this is then removed and the prensure piit on again. Where the cloth 
ia not uHcd, it ia neccaiuiry lo shave <>if, with a wide, thin knife, the 
projtotiug wan ridgea. 

BemoTlnc Uia rorma.— In case the forme should stick to the wax, 
it may be relieved by touching the ohaso gently in two or three places 
with a lunp: screw driver, taking core not to break the face of t^ wax. 
The case is now tu bu placed upon a tablu, leady for the prooeos of 
iitUding. 



s$6 



ELEGTBO-DEPOSinON OF OOPFBB. 



Bnildlaff. — ^The mould is now laken in hand bj a workman wbo, 
with the wide, thin bladed knife, sharee off the projecting wax ridgee 
forced up about the edges and low parts of the mould by the press, 
and which, if not removed, would impede the separation of the * ' shell ' ' 
from the face of the moidd, when removed from the depositing tank. 
The operation of ** building *' is thus performed : the workman takes 
an implement such as is shown in Fig. 64 (called a ** building-iron "), 
several of which are laid on a rack in a small oven 
heated by gas, and applies to it from time to time a 
thin strip of wax, allowing the melted wax to run from 
. the point of the tool on to the open spaces or blanks of 
the mould. The operation requires a skilful and steady 
hand of a practised workman. Upon this point Wahl 
says, " It is essential, in order to avoid the chiseling 
(routing or deepening of the open spaces) that would 
otherwise be necessary to perform upon the finished 
electrotype, for, unless these open spaces are consider- 
ably lower than the spaces between the fine lines of 
the subject, they are apt to smut in the printing pro- 
cess. To cut these out with the chisel, or routing ma- 
chine, from the finished electrotype would be a difficult 
and dangerous operation, difficult because of the com- 
parative hardness of the copper surface, and dang^erous 
because the breaking of the continuity of the copper 
surface will be liable to curl up on the edge of the cut, 
and to gradually destroy its attachment to the stereo- 
type metal with which it is backed up.*' To avoid the necessity of 
chiseling, with the risks which it entails, a ridge of wax is built up 
on those parts of the mould which require to be depressed in the 
finished electrotype, but g^reat care is necessary to prevent the wax 
from running whcsre it is not wanted. The wax used for the above 
purpose is cut into strips of six or eight inches in length, and about 
half an inch in thickness. 

Flumliaipoliic tlia Konld. — ^The wax mould being prepared as 
above, is next coated with plumbagfo, the material used in America 
being obtained from Ceylon graphite. The plumbag^ing is generally 
performed by a machine, the most approved form of which is repre- 
sented in Fig. 65, its cover being removed to show its construction. 
The machine has a travelling carriage, holding one or more forms, 
which passes to and fro under a laterally-vibrating brush. An apron 
is placed below to receive the loose plumbago, which is used over and 
over again. As soon as the mould is sufficiently plumbagoed, it is 
removed from the press, and the surplus material is either dislodged by 
a hand-brush or with broad-nosed bellows. It is essential that all 




Fig. 64. 



KNinHTS PLCMBAOOIHO PBCMJESa. I37 

exoen of plumbago be removed, oOierwiBe a coarse and boltj 
decffotype will b« obtained. 

Owing to the unavoidable diul created b) the dry plumbagoing 
machine, bj the impalpable graphite powder, aome eUotnitypiatB 
prefer to adopt the wet pnxxaa invented by Mr. 3ilaa P. Knight, d 



Fift. 6;. — Plnmbagolng Machine. 

the eleotrotyping department of Ueeare. Harper Brothers, New 
rent. This pTooeea is said to irork more speedilj' and delioat«lj than 
the fonner, the moulds being thinly and uniformly coated, ueithw 
omitting the dot of an i, nor allowing the bridging over of fine lines. 

KUcht's Flnmbasalns riuu— By this method, the mouldn 

are placed npan a eheU, in a auitable receptacle, and a rotary pump 
foTcee an emnlsion of plumbago and water over their face», through a 
travelling fine-rose nozzle. This process is Boid to be "rapid, ufii- 
oieat, neat, and economical." 

'Wlrlns. — When the plumbagoing is complete, the workman takes 
one or Tnore lengths of stout copper wire, the ends of which are first 
oleaned, and thon gently heated ; the wires are then embedded in the 
wax oompoeition on the lide of the mould, and the joints arc then 
plmabagaed with the finger so as to ensure a perfect rleclrical cmmtclion 
between the wire and the plnmbagoed surface. In order to prevent 
the copper deposit from taking place upon such surfaces beyond the 



138 ELECTRO DEPOSITION OP COPPER. 

face of the moxild as may have become coated with the graphite, the 
workman takes his hot building-iron, and passes it over these outlying 
parts of the mould so as to destroy the conductibility of the superfluous 
plumbago ; this is termed stopping. 

When moulds of large size have to be treated, it is necessary to 
place a series of copper wires on the edges of the mould, by which 
means the deposit commences uniformly at the several points of 
junction ; these wires are then brought in contact with the slinging 
wires by which the mould is suspended, and thus receive the current 
from the conducting rod connected to the dynamo-electric machine or 
batteries. 

Boa's Bleetrle OoniMetlon Orlpper. — ^A very practical airange- 
ment for conducting the current to several points, or parts of the 
mould, is effected by the ** electric connection gripper *' of Messrs. B. 
Hoe and Co., which is represented in Fig. 61, as connected to the 
moulding case. " This arrangement is designed to hold and sustain 
the moulding cafo, and at the same time to make an electric connection 
with the prepared conducting face of the mould itself, consequently 
leaving the metal case itself entirely out of the current (circuit), so 
that no copper can be deposited on it.** 

MetalHrtng the Konlda. — Plumbago being but a moderately good 
conductor, many attempts have been made both to improve its con- 
ductibility, and to provide a substitute for it altogether. With the 
former object, we have mixed moderate proportions of Bessemer 
bronze powder with advantage, as also copper reduced from the 
sulphate by metallic zinc, and afterwards triturated with honey, an 
impalpable powder, or bronze^ being obtained by washing away the 
honey with boiling water, and afterwards collecting the^c*«^ particles 
of the reduced metal by the process of elutriation ; that is, after 
allowing the agitated mixture of water and metallic powder to repose 
for a few seconds, the liquid, holding the finest particles in suspension, 
is i)oured off and allowed to settle, when an exceedingly fine deposit 
of metallic copper is obtained. The process of coppering the mould, 
devised by Mr. Silas Knight, is generally adopted in America. By this 
method, a thin film of copper is deposited on the mould in a few seconds, 
the operation being conducted as follows : *' After stopping out those 
portions of the mould that are not to receive the deposit, it is laid in a 
shallow trough, and a stream of water turned upon it from a rose jot, 
to remove any partiohm of blaoklead that may ixanain in the lines or 
letters. The workman then ladles out of a conveniently placed vessel 
some sulphate of copper solution, pours it upon the face of the mould, 
then dusts upon it from a pepper box some impalpably fine iron 
filings, and brushes the mixture over the whole surface, which thus 
becomes coated with a thin, bright, adherent coat of copper. Should 



ADAMS* PROCESS OP METALLISING MOULDS. 139 

any portion of the surface, after such treatmenti remain uncoppored, 
the operation is repeated. The excess of copper is washed oiff, and 
the mould is then ready for the bath.'* The washing of the mould is 
effected by means of a stream of water applied from a rubber hose and 
pipe, and the mould must be placed in the bath directly after the 
washing is complete. 

Adams' ProcMM of BSatallisins Konlds. — This process, which 
was patented in America in 1870, is said to give a perfect conducting 
surface to wax moulds with greater certainty and rapidity than any 
other, and will accomplish in a few minutes that which plumbago 
alone would require from two to four hours. The process is con- 
ducted as follows : WhlLe the mould is still warm in the moulding 
case, apply freely powdered tin (tin bronze powder, or white bronze 
powder) with a soft brush until the surface presents a bright, metallic 
appearance ; then brush off the superfluous powder. The forme of 
type or wood-cut is then plumbagoed, and an impression or mould 
taken in the wax as before described, the mould being built up and 
connected as before. The tin powder is now to be brushed over it 
either by hand or machine, and the superfluous tin blown away by the 
bellows, after which the building-iron is applied for stopping all parts 
upon which copper is not to be deposited. The mould is then to bo 
immersed in alcohol, then washed with water **to remove the air 
from the surface," when it is ready to be immersed in a solution pre- 
pared as follows : FiU a depositing tank nearly full of water, keeping 
account of the number of gallons poured in ; hang a bag of crystals 
of sulphate of copper until the water is saturated ; for every gallon of 
water used add from half a pint to three gills of sulphuric acid, and 
mix the whole thoroughly. In this solution hang a sheet of copper, 
connected to the positive pole of the battery, and when the solution 
becomes cool and settied, immerse the mould and connect it with tike 
negative electrode, when the surface of the mould wlU be quickly 
covered with thin copper. Then remove for completion to another and 
larger depositing vat, containing a solution made in the proportion of 
one pound of sulphate of copper and one gill of sulphuric acid to each 
gallon of water. If crystals of sulphate of copper form on the copper 
plate in the first depositing vat, disconnect it and dissolve them ofl;, 
substituting for it a clean plate. 

Since, in the above process, the tin powder becomes disscilved ami 
enters into the solution, when this liquid becomes satunited with trQ, 
after being l6ng in use, it must be cast aside and replaced by fresh 
solution. The tin powder may be employed, as a substitute fur 
plumbago, without changing from one bath to another, thus : After 
the mould has received the desired impression, it is taken to the plum- 
bago table, and held face downward with one end resting on the 



I40 ELEOTBO-DBPOSITION OF OOPFEB. 

table, while the other is supported by the hand. It is then stniok on 
the back several times to loosen the blaoklead that is pressed on the 
wax while moulding, and all the fine duet that may cUng to the 
mould must be blown away. After building up and making all con- 
nections, it is to be placed in the hand-case or plumbagoing machine, 
and the tin powder applied in the same way as plumbago. Both the 
machine and hand -case should be kept free from plumbago, the 
tin powder only being used to metallise the surface of the mould. If 
the machine be used, place the mould, or moulds, on the carriage, 
cover well over with tin jpowder, close the door, and ran once forward 
and backward under the vibrating brush ; then turn the moulds round, 
put on more tin powder, and run through again. It takes three 
minutes for the whole operation. The tin powder is to be beaten out 
on the table used for this powder as before, and then thoroughly well 
blown out. Instead of using the building-iron for stopping off, any 
suitable varnish, or an aloohoUc solution of sealing-wax, may be used. 

Qaiekinff. — ^To prevent the copper deposit from being broken over 
lines of set-up type, the lines may be wetted with a dilute solution of 
nitrate of mercury, or with the cyanide quioking solution used in pre- 
paring work for plating. A further deposit is then given in the sul- 
phate of copper bath. 

The Pepoirttfiig BaUi. — ^The solution employed is a saturated solu- 
tion of sulphate of copper, acidulated with sulphuric acid, and lai^ 
copper anodes are suspended in the bath, between which the cases 
containing the prepared moulds are suspended, back to back, so that the 
faces of the moulds may be directly opposite the anodes. The time 
occupied in obtaining the electro deposit of copper depends upon the 
power of the current employed and the thickness of metal desired. 
For ordinaiy book or job work, the shell of copper should be about the 
thickness of good book paper, and this should be obtained in from 
three to five hours. Electros for newspaper, titles, and such blookB as 
are subjected to much use, should receive a stouter deposit. 

Battsriaa. — Several modifications of the Smee battcffy have been ex- 
tensively adopted in the United States, including copper plates, 
deotro -silvered, and platinised ; but the most g^eraUy accepted im- 
provement consists in employing platinised platinum plates for the 
negative element instead of platinised silver of the Smee battery. The 
battery plates, instead of nearly touching the bottom of the cell, as in 
the ordinary Smee battery, whereby, after being in use some time, 
they become immersed in a saturated solution of sulphate of zinc, 
causing gpreat diminution of the current, only extend to about one- 
third of the depth of the battery cell. By this arrangement, which 
was devised by Mr. Adams, of America, in 184 1, an equal action of the 
battery is kept up for a much longer period than would be possible 



TREATMENT OF THE BIAOTBOTTFB. 



141 



wiih a Smee battery of ordinaiy oonstractloii. Wahl aays that a 
Smee battery of twenty-six pairs, each 12 by 12 inches, will deposit 
from six to six-and-half square feet of copper upon prepared moulds 
in four hours. Batteries, however, are not now much used in the 
States, having^ been greatly superseded by the dynamo-electric 
machine, whereby the electrotyping and electro-depositing arts in 
general have become enormously increased. 

Tr ^ alm mt of th* Bte e ir o type. — When the mould has received the 
requisite deposit, it is to be removed from the bath, and is next to be 
separated from the wax composition. This is done by placing the 
mould in an inclined position, and passing a stream of hot water over 
the copper surface, which, by softening the wax, enables the copper 
shell to be stripped off, by raising it from one comer while the hot 
water is passing over the mould. The shell should be removed with 
care and must not be allowed to bend in the least deg^ree. The thin 
film of wax which adheres to the face of the electro is removed by 
placing it upon a wire rack, resting on a vessel containing a solution 
of caustic potash, which is poured over the electro by means of a ladle, 
the liquor returning to the vessel beneath. The potash has the effect 
of dissolving the wax in a short time, after which the electro is woU 
rinsed in cold water. 

Ttmiliis and Haoklng Ul^ BloetTotype. — The first of these opera- 
tions, tinninfff is necessary in order to ensure a perfect union between the 
"baoking-up metal" (stereotype metal) 
and the electrotype. The back of the 
electro is first brushed over with a solution 
of chloride ofzinCy made by dissolving zinc 
in muriatic acid, and diluting it with 
about one-third of water, to which, some- 
times, a little sal ammoniac is added. The 
electrotype is now laid, face downwards, 
upon an iron soldering plate, floated on a 
bath of melted stereotype metal, and when 
sufficiently hot, melted solder, composed of 
equal parts lead and tin, is poured over the 
back, by which it acquires a clean bright 
coating of solder. Another method is the 
following: The shell being placed face 
downward, in the haeking'pan, is brushed 
over with the *' tinning liquid " as before, and alloyed tin foil is spread 
over it, and the pan again floated on the hot baoking-up metal until tho 
foil melts and covers the whole back of the electrotype. When the foil 
is melted, the backing-pan is swung on to a levelling stand, and the 
melted backing metal is carefully poured on the back of the shell from 




Fif^. 66. 



14* BLECTRO-nEFOflFtlOS OF COPIVB. 

an iron ludlo, oommencing at one of the comers and f^nidually nm- 
iiin^r over the surface until it is covered with a backinp: of sufficient 
thickncsa. A convenient fiirm uf )iitokin)^-paD and stand is xhnwn in 
Fig. 66. The thiplmrs3 of the bjicltiiif* is about onc-ei^htli of an inch, 
orsnfficient to enable the electro, when trimmed and mounted, towith- 
ntund the preBBUrrr of the printina' presii. The baokinR-up alloy a 
rnrioualy compowd, hnt thp fnllowinjr is a good practioal formula : — 



— As thoy pass from the hands of the "backer," 
the phttca present a rough and uneven surface on the back, and the 
bbinkw are higher than they bhould be for mounting. It in the finisher' h 



Flff. 67.— S»w Table. Hill. Hqunring Table. 

duty tj> remedy all such defects. If the backed elcetrntypo conxiftH of 
Hcveral pages, it is first taken tii the saw table. Fig. 67, where it is 
roughly sawn apart by a eirenlar saw, the eyes of the workman being 
protected from the particles of Hying metal by a iquarc plale of yliv", ai 
shown in the figure. Eocb phit<> is then trimmed all round to remove 
tough adges. and if there arc any projectiona which would proYpnt it 
from lying flat, these aro carefully ont down with a small chisel. The 
pktc is oezt lAavtd to rmooio the loaghneM from the bauk and tnako 



FINTSHINa TBB ELEOTROTVPB. T43 

it of uniform thiokncnx in all parts. Thin is effcotcil in Hmall eata'b- 
IJahtnenta by the hand diaving machinB. Fig. 68, but since tUs opera- 
ig the most laborious part of the flninhinR prooesa, it i« far preferable 
to employ a power machine for this purpoxo. The plate bcin^ now 
brought to nearly ita proper thickness, anit almost true, is next tested 
with a ntraigbt-eiige, and all uneFcnnceucs bcnCen down with a light 
hammer and p]aiipr, preparatory to the final shaving : the platf 1^ 
then pnsHpd through the hand shaving machine, accurately ndjiistM, 
and two or three hght euta are taken off. The face ia then tested by 
rubbing with a flat p\eve of willow charcoal, which, by not blackening 
the low piirts, or hollows, ennhle<i the workman to see if ati; such 
eiiat, in which case he put« 
a correBponding mark lo 
indicate these places on the 
back with a suitable tool. 
The plate ia then laid, face 
downward, and the marked 
places arcstruek with a ball- 
faced hammer which forces 
up the printing aurface be- 
neath to its proper level, 
Tho plate is next subjected 
to the hand nhnving machine 
(Fig. 68), by which the back 
becomes shaved down tn ita 
proper thickness and ren- 
dered perfectly level and 
smooth. The cdgoaare neit 
planed wguarc and to tho 
proper sixe. after which they 

aro tranrfeiTcd to tlio car- ff^ 68.— Hand ShavinR Machine, 

pentcr, who moutita them, 

type-high, on bloclta of wood, which maylie cither of cherry, mahogany, 
or other suitable wood, which in cut perfectly Inio and oquaro in every 
direction. The plates, when mountiHl, aro rcpidy for the printer. 

Bookwork is uaunlly not mounted on wood, the plates heing left un  
mounted, and llnishod with bevellod edges, by which they are secured 
on auitablo plate blocks of wood or iron, auppliod with gripping pieeaii 
which hold them firmly at the proper height, and enable them to be 
properly locked up. 

Fig. 69 represents Ueeats. E. Hoe * Co.'b power planing and 
sawing machine, which is intended for roughing off plates before 
■ending them lo the shaving machine, and ia said to be very aimple, 
qniek, and efficient in operation. A circular saw runs in an olevatinf 



'44 ELBCTBO-r'BPOBITION OP COPPBE. 

table at one comer, for sqoaring' np, and an outside cutter, with 
sliding' tabic, is sttoclied fur Bquariog up metal bodies, &c. 

lUactrotnrtiis fi?om Flutar MonUa. — Plaster of P&ria may be em- 
ploytd for □utking' electrotype moulds Instead of wax, in which caae 
the phmter mould is firat soalitd in «ax ; it is then coated with a min- 
tiiro composed as follows : nitrate of silver i gramme, diiwolved in 
water, 2 grammes ; to this is added :^ grammos of ammonia, and then 
3 grammes of absolute alcohol. The mould is then to be exposed to 



!''■)(■ £9. — Power Planing and Sawing Machine. 

sulphuretted hydrogen (fae — made by pouring ililute suiphurio acid on 
powdered sulphide of iron. 

aU elt o typl ng Wood BncraTliisB, fte.— One of the most uncful 
and exteniiive applications of eledzotypiug is in the copying of «-ood 
engravitig^ in electrolytic copper, to form metallic printing sorfacea in 
liau of printing from the lewi durable material, wood. The value and 
importance of electrotype blocks to the proprietors of illustratotl 
pubhcations — many of which have an enormone aale — will be at OTU-'O 
recognised when we state that the electrotype heading of T/ie Tuf,et 
newspaper is repnted to have produced no less thantwenty millions of 
copies or imprensionii before it required renewal. It would be difficult 
to estimate hnn' Tnunj- wood block:: would have been reijuirod to 



ELEOTROTYPINO WOOD ENGRAVINGS. 1 45 

f umitth so largo a number of impressions, equally perfect. Indeed, if 
we take the trouble to examine some of the illustrations of our 
periodical literature which have been produced direct from wood 
blocks, we cannot fail to notice the gradual depreciation of the 
original engraved blocks. 

In copying an eng^ved wood block, it is first well brushed over 
with plumbago, or simply moistened with water ; it is then placed 
upon a level bench, and a metal frame somewhat higher than the block 
is fastened round it. A lump of softened gutta-percha is then placed 
in the centre of the engraving, and forcibly spread outward (towards 
the frame), by which air becomes excluded. A plate of cold iron is 
now placed over the gutta-percha, with gentle pressure, which is 
afterwards gradually increased, by moans of a press, as the gutta- 
percha becomes harder. When the mould has cooled, it is carefully 
separated from the block, and well plumbagoed, after which the con- 
necting wire and " guiding wires " are attached ; it is then ready for 
the depositing bath, where it is allowed to remain until a shell of 
sufficient thickness is obtained, which will depend upon the size of 
the mould and the strength of the current employed. Under lavour- 
able conditions, a shell of copper, say, of about one square foot of 
surface, will be obtained in about eight or ten hours, or even less ; it 
is commonly the practice to put a series of moulds in the bath towards 
the evening, and to leave them in the bath all night ; on the following 
morning the deposit is found to be ready to separate from the mould. 
In electrotype works where magneto or dynamo machines are em- 
ployed (as in some of our larger printing establishments), a good shell 
is obtained in from three to five hours,* according to the dimensions 
of the mould. After removing the mould from the bath, it is rinsed 
in water, and the shell carefully detached, and the electrotype is 
next backed-up with solder or a mixture of type metal and tin, the 
back of the electrotype being first brushed over with a solution of 
chloride of zinc. The edges of the electrotype are next trimmed with 
a circular saw, and are afterwards submitted to the planing machine, 
by which the backing metal is planed perfectly level and flat ; the edges 
are then bevelled by a bevelling machine, when the plate is ready 
for mounting on a block of cedar or mahogany, which is effected by 

* An American electrotypist, on a visit to London, told the author, about 
five years ago, that, having adopted the Weston dynamo machine in place of 
voltaic batteries, he could deposit a shell of copper upon fifteen moulds, 
each having about two square feet of surface, in about two and a half hours ; 
that is to say, by the time the fifteenth or last mould was put into the 
bath the one which had first been immersed was sufficiently coated for 
backing up. 



146 ELECTRO-DEPOSITION OF COPPEB. 

meoDB of small iron pins driven into the bevel edges of the backing 
metal. When oomplete, the blook, with its mounted electrotyjDe, 
should be exactly ti/pe high. Respecting" electrotjrpes from wood 
engraving's, or *' electros/' as they are commonly called in the print- 
ing trade, we may mention that many of omx larger illustrations 
are produced from electrotypes. Engraved steel plates are copied in 
the same way as above, and their reproduction in copper by the elec- 
trotype process is extensively practised. 

Tin Fowd«r toot Btoetrotjpias. — Grain tin may be reduced to an 
impalpable powder by either of the following methods : — i . Melt the 
grain tin in an iron crucible or ladle, and pour it into an earthenware 
mortar, heated a little above its melting point, and triturate briskly 
as the metal cools. Put the product in a muslin sieve and sift out 
the finer particles, and repeat the trituration with the coarser par- 
ticles retained in the sieve. To obtain a still finer product place the 
fine powder in a vessel of clean water and stir briskly ; after a few 
seconds' repose, x)our off the liquor in which the finer particles are 
suspended, and allow them to subside, when the water is to be again 
poured off and a fresh quantity of the powder treated as before. The 
impalpable powder is finally to be drained and dried, and should be 
kept in a wide-mouthed stoppered bottle for use. 2. Melt grain tin 
in a graphite crucible, and when in the act of cooling, stir with a 
clean rod of iron until the metal is reduced to a powder. The powder 
should then either be passed through a fine sieve or elutriated as above 
desoribed, which is by far the best method of obtaining an absolutely 
impalpable product. In using this powder for electrotyping pur- 
poses in the manner previously described, it must not be forgotten 
that the tin becomes dissolved in the copper bath ; it should therefore 
only bo employed in a bath kept specially for the purpose, and not 
be suffered to enter the ordinary electrotyping vat. 



CHAPTER VIII. 

BLEOTKO-DEPOSITION OF COPPER (eontinued). 

Deposition of Copper by Dynamo-eleGtricity. — Copying SUtue«, Ac.— Lenoir'a 
Prooen. — Deposition of Copper on Iron. — Coppering Printing Rollers. — 
Sehlumberger's Process. — Producing Printing Boilers by Electricity. — 
Coppering Cast Iron. — Coppering Steel Wire for Telegraphic Purposes. 
—Coppering Solutions. — Dr. Eisner's Solution. — Walenn's Process. — 
Gulensohn's Process. — ^Weil's Coppering Process.— Electro-etching. — 
Glyphography. — ^Making Copper Moulds by Electrolysis. — Making Elec- 
trotype PUtes from Drawings. — Coppering Steel Shot. — Coppering 
Notes. 

]>«pmltioii of Copper by Byiuuno-eloetrleitsr. — Within the past 
few years, owing to the great advance made in the production of 
powerful and reliable magneto and dynamo-electrio maohinas, the re- 
duction of copper by eleotrolysiB in the various branches of eleotro- 
deposition has assumed proportions of great magnitude ; and while 
nickel-deposition— which fifteen years ago was a comparatively un- 
developed art — ^has quietly settled down into its legitimate position as 
an important addition to the great electrolytic industry, the eleotro- 
deposition of copper, and its extraction from crude metal, have pro- 
gressed with marvellous rapidity, both at home and abroad, but more 
especially so within the past five or six years, and we may safely 
predict from our knowledgfe of the vast number of magneto and 
dynamo machines which are now being constructed, under special 
contracts, that in a very short time the electrolytic reduction 
of copper will reach a scale of magnitude which will place it 
amongst the foremost of our scientific industries in many parts of 
the world. Before describing the processes of coppering large metallic 
objects, we must turn our attention to the production of electrotypes 
of larger dimensions than those previously considered. At a very early 
period of the electrotype art, Russia, under the guidance of the famous 
Professor Jacobi, produced colossal statues in electrolytic copper, which 
at the time created profound astonishment and admiration. About the 
same period our own countrymen directed their attention to this appli- 
cation of electrotypy, and at subsequent periods electrotypes of con- 
siderable dimensions were produced not only in this country but on 
the Continent. Some exceedingly fine specimens have been produced 
by Messrs, . Elkington & Co., one of the most notable of which is 



It48 ELKOTBO-DEPOBinON OF COPPBB. 

that of the Earl of Eglinton, 13^ feet high and weighidjgf two tons, 
while Bomc other equally good specimena of life-size busts and baa- 
reliefs are to be seen in Wellington College, the House of Lords, &c. 
The well-known Paris firm, Messrs. Christofle & Co., have also 
produced colossal electrotype statues, one of which is 29 feet 6 inches 
in height, and weighs nearly three tons and a half ; the oompletion of 
the deposit occupied about ten weeks. 

GopyiBS Btatoesy See, — ^When very large objects have to be repro- 
duced in electrotype, the method adopted is usually as follows : The 
original, formed of plaster of Paris, produoed by the modeller or 
sculptor, is first brushed aU over with boiled linseed oil, until the sur- 
face is completely saturated with the drying oil. After standing for 
two or three days, according to the temperature and condition of the 
atmosphere, the object, which is thus rendered impervious to moisture, 
and readily receives a coating of plumbago, is thoroughly well brushed 
over with blacklead until the entire surface is perfectly coated with 
the conducting material. The model is next connected to conducting 
wires, assisted by g^ding wires, and placed in a sulphate of copper bath, 
where it receives a deposit of about one-sixteenth of an inch in thick- 
ness, or a shell sufficiently stout to enable it to retain its form after 
the inner plaster figure has been removed, which is effected in this 
way : the electrotype, with its enclosed model, being taken out of the 
batii, is first thoroughly well rinsed, the copper shell is then cut 
through with a sharp tool at suitable places, according to the form of 
the original figure, by which these various parts, with their guiding 
wires attached, become separated ; the plaster figure is then carefully 
broken away, and all parts of it removed. After rinsing in hot water, 
the outer surface of the copper ** formes " are well varnished over to 
prevent them from receiving the copper deposit in the next operation. 
The formes are next exposed to the fumes of sulphide of hydrogen, or 
dipped in a weak solution of sulphide of potassium (liver of sulphur), 
to prevent the adhesion of the copper deposit. These *' formes," or 
parts of the electrotjrpe shell, constitute the moulds upon which the 
final deposit, or electrotype proper, is to be formed, and these are re- 
turned to the depositing tank and filled with the solution of sulphate 
of copper, anodes of pure electrolytio copper being suspended in each 
portion. Deposition is then allowed to take place until the interior 
parts or moulds receive a coating of from one-eighth to one-third of 
an inch in thickness. The various pieces are then removed from the 
bath, and after well rinsing in water, the outer shell, or mould, is 
carefully stripped off, and the respective parts of the electrotype 
figure are afterwards fixed together when the operation is complete. 

Jtenolr's Proeass. — A very ingenious method of electrotyping large 
figures was devised by M. Lenoir, which consists in first taking im- 



COPPERING PSIKTINO BOLLSBS. X49 

» 

preesions in gutta-percha of the object in several pieoee, which may 
afterwards be put together to form a perfect figure ; the inner sur- 
faces of these impressions, or parts of the mould, are then well coated 
with plumbago. A "dummy" of the form of the interior of the 
mould, but of smaller dimensions, is now formed of platinum wire, to 
act as an anode, and the several parts of theplumbagoedgpitta-peroha 
mould axe put together to form a complete mould all round it. The 
mould, with its platinum wire core (the anode) — which is insulated 
from metallic contact with the mould by a covering of india-rubber 
thread — ^is then placed vertically in the bath, weights being attached 
to allow the mould to sink into the solution. The platinum anode 
and the plumbagoed mould are then put in circuit and deposition 
allowed to progress. To keep up the strength of the copper solution 
within the mould, in the absence of a soluble anode, a continual flow 
of fresh copper solution is allowed to enter the mould, from a hole at 
the top of the head, which makes its escape through holes in the feet 
of the mould. When a sufficiently stout deposit is obtained, the 
flexible wire anode is withdrawn through the aperture in the head, 
after which the various portions of the gutta-percha mould are re- 
moved, and the seams at the junctions of the electrotype are cleared 
away by appropriate tools. 

Dmpoaitkaa of Copper on Xron. — Since iron receives the copper 
deposit from acid solutions without the aid of a separate current, and 
the deposit under these conditions is non-adherent, it is the practice 
to give a preliminary coating of copper to iron objects in an alkaline 
bath, ordinary cyanide solutions being most generally adopted for 
this purpose. Many other solutions have, however, been recom- 
mended, some of which may deserve consideration. In any case, the 
iron article is first steeped in a hot potash bath, when the presence 
of greasy matter is suspected, and after rinsing, is immersed in a 
pickle of dilute sulphuric acid, ^ lb. of acid to eAsh gallon of water. 
After well rinsing, the article is scoured with coarse sand and water, 
applied with a hard brush, and after again rinsing, is immersed in the 
allcaUne bath until perfectly coated with a film of copper. It is then 
again rinsed, and at once placed in a sulphate of copper bath, where 
it is allowed to remain imtil a sufficiently stout coating of copper is 
obtained. In some cases, where the object is of considerable propor- 
tions, it is kept in motion while in the solution, by various mechanical 
contrivances, as in Wilde's process, to be referred to shortly. 

Copp«rins mntUiff BoUmts. — Many attempts have been made, 
daring the past thirty years or so, to substitute for the costly solid 
copper sellers used in calico-printing, iron roll^l^ coated with a layer 
of copper by electrolysis, llio early efforts were conducted with the 
ordinary/voltaic batteries, but the cost of the oleotricity thus obtained 



E50 ELECTTBO-'D&POSITION OF OOPFBB. 

was far too great to admit of the piooefls being practically suooessfnl, 
while at the same time the operation was exceedingly alow. A method 
which was partially successful consisted in depositing, in the form of 
a flat plate, an electrotype bearing the design, which was afterwards 
coiled up in a tubular form, and connected to an iron cylinder or roller 
by means of solder, the seam being afterwards touched up by the 
engrayer. A far better system, however, is now adopted, which is in 
every way perfectly successful ; and printing rollers are produced in 
large quantities by electro-deposition at about one-half the cost of 
the soEd copper article. Before describing the methods by which 
cast-iron rollers are faced with copper at the present time, it may be 
instructive to consider briefly some of the means that have been 
adopted to deposit a sufficient thickness of copper upon a oast-iron 
core to withstand the cutting action of the engraver's tools. 

Beliliiinb«rg«r's Froe«ss. — This consists in depositing copper upon 
previously well-cleaned cast-iron cylinders by means of the ** single- 
cell " process. The solution bath consists of a mixture of two solu- 
tions composed of (i) Sulphate of copper, i part; sulphate of soda, 
2 parts ; carbonate of soda, 4 parts ; water, 16 parts. (2) Cyanide of 
potassium, 3 ; water, 12 parts. The interior of the bath is surrounded 
by porous cells containing amalgfamated zinc bars with copper wires 
attached, and dilute sulphuric acid. The solution is worked at a 
temperature of from 59" to 65° Fahr., and the iron cylinder, being 
put ia contact with the zinc elements, remains in the bath for twenty- 
four hours, at the expiration of which time it is removed, well washed, 
rubbed with pumice -powder, ag^ain washed in a solution of sulphate 
of copper having a specific gravity of i * 161 , containing ji^th part of its 
volume of sulphuric acid ; scraps of copper are kept in the bath, to sup- 
ply the loss of copper, and prevent the liquid becoming too acid. The 
cylinder is then returned to the bath, or placed in a mixture composed 
of the following two solutions : (i) Acetate of copper, 2 ; sulphate of 
soda, 2 ; carbonate of soda, 4 ; water, 16 parts. (2) Qyanide of po- 
tassium, 3 ; liquid ammonia, 3 ; water, lO part^. The cylinders are 
to be turned round once a day, in order to render the deposit uniform, 
and the action is continued during three or four weeks, or until the 
deposit is ^th of an inch thick. 

Another method consists in first coppering the well-cleaned cast- 
iron cylinder in an ordinary alTraliTift coppering bath, and then trans- 
ferring it to an acid bath of sulphate of copper, the cylinder in each 
case being surrounded by a hollow cylinder of copper for the anode ; 
Uie process is allowed to proceed slowly, in order to obtain a good 
reguliue coating, and when this is obtained of sufficient thickness to 
bear engraving upon, the surface is rendered smooth by turning at 
the lathe. 



OOPPEBINO PRINTING BOLLEBS. X5t 

Vfeodneiiis VrlnUns BoUsrs by BlaeiMto-elMtrleity. — Wildest 
Process. — It is obvious that the cloctrical power obtained from mag- 
neto and dynamo -electric machines is more capable of depositing econo- 
mically the requisite thickness of copper upon cast-iron cylinders to form 
printing rollers than could be expected from voltaic electricity, which 
necessarily involves the solution of an equivalent of zinc and the con- 
sumption of sulphuric acid to deposit a given weight of copper. It 
is well known that deposition takes place more freely upon the lower 
surfaces of the cathode, and consequently, when the deposited metal 
is of any considerable thickness, the irregular, surface thus produced 
is often a source of great trouble to the electro -depositor ; in the case 
of printing rollers, however, in which a perfectly uniform thickness 
of the deposit is absolutely indispensable, some means must be adopted 
to render the deposit as uniform as possible from end to end of the 
cylinder. To accomplish this, Mr. Henry "Wilde, of Manchester, 
effected an arrangement for which he obtained a patent in 1875, 
which consists in ** giving to the electrolyte or depositing liquid in 
which the roller to be coated is immersed, or the positive and nega- 
tive electrodes themselves, a rapid motion of rotation, in order that 
fresh particles of the electrolyte may be brought successively in con- 
tact with the metallic surfaces. By this, ' ' says the patentee, * * powerful 
currents of electricity may be brought to bear upon small surfaces of 
metal without detriment to the quality of the copper deposited, while 
the rate of thd deposit is greatly accelerated. 

*' Motion may be communicated to the electrolyte, either by the 
rotation of the electrodes themselves, or when the latter are stationary, 
by paddles revolving in an annular space between them. The iron 
roller to be coated with copper is moimted on an axis, the lower end 
of which is insulated, to prevent its receiving the deposit of copper at 
the some time as the roller. The roller, after having received a film 
deposit of copper from an alkaline solution in a manner well under- 
stood, is immersed in a vertical position in a sulphate solution of 
copper, and a motion of rotation is given to the roller or rollers by 
means of suitable gearing. The positive electrodes are copper roUerF 
or cylinders, of about the same length and diameter as the roller to 
be coated, and are placed parallel with it in the sulphate solution. 
The electrical contacts are made near the upper and lower extremities 
of the electrodes respectively, for the purpose of securing uniformity 
in the thickness of the deposit. The sulphate solution may be main- 
tained at an uniform density, from the top to the bottom of the bath, 
by rotating a small screw propeller, enclosed in a tube communicatiug 
with the liquid, and driven by the same gearing that imparts motion 
to the roller." 

The electric current employed for depositing copper by the above 



153 ELEGTBO-DBPOSITION OF OOPFEB. 

meihod may be obtained from Wilde's magneto -electric machine, 
which has been very extensively adopted for this purpose, or from 
any dynamo electric machine capable of yielding an adequate current. 
Mr. Wilde says, in the specification above quoted, *^ Although I have 
only mentioned cast-iron as the metal upon which the copper is 
deposited, the process is applicable to rollers made of zinc or other 
metals, and their alloys. The method of accelerating the rate of de- 
posit, by giving to the electrolyte, or to the electrodes, a motion of 
rotation, may be applied to the electrolytic method of refining copper 
described in Mr. J. B. Elkington*s patent." Mr. Wilde's system of 
coppering cast-iron rollers was established in 1878, but he subse- 
quently disposed of his patent rights to the Broughton Copper 
Company, who carry on the process successfully, and have extended 
it to the coating of hydraulic rams, &c. 

Ooppoias Oast tton. — The great ptogrem which haa been made 
in the production of artistic castings in iron during the past thirty 
years or so, not only in this country, but on the Continent, has always 
created a desire that some economical and reliable method of coating 
such work with copper could be devised, not alone to preserve the 
iron from atmospheric influence, but also to enhance the beauty of 
the work by facing it with a superior metal. To deposit a protective 
coating of copper upon large pieces of cast iron, however, has gene- 
rally been a matter of considerable difficulty, owing to the almost 
inevitable presence of sand-holes and other flaws which, even when 
not of large size, are often of sufficient depth to retain padddes of 
silicious or other matter which cannot readily be dislodged by the 
ordinary methods of pickling and scouring ; and since these defective 
spots do not receive the deposit of copper, the underlying metal must 
always be liaible to corrosion at sodh parts, when subjected to the 
effects of moisture. These observations are chiefly directed to the 
coppering of cast-iron work destined to be exposed to the vicissitudes 
of the weather, as street lamp -posts, for example; and though we 
have not yet devoted much attention to this branch of industry in 
this country, it has received a good deal of attention in France, but 
more especially in Paris. To overcome the difficulties above men- 
tioned, copper is not deposited direct upon the iron, as will be seen 
below, but upon a coating of varnish, rendered conductive by the 
application of plumbago. The system adopted by M. Oudrey, at 
his works at Auteuil, may be thus briefly described : — The cast-iron 
object IB first coated all over with a varnish composed of resinous 
matters dissolved in benzol, to which is added a sufficient quantity of 
red or white lead, the varnish being then allowed to dry. The surfact^ 
thus prepared is next brushed over with plumbago, and the artide 
then coated with coppar in the ordinary sulphate bath by the * ' single- 



OOPPEBIKG CAST IRON. 1 53 

cell '' method, for whtdh very large porous cells are employed^ In 
about four or five days a sufficiently thick coating of copper is 
obtained, when, after rinsing and drying, a bronzed appearance is 
given to the work by the application of a solution of ammonio- 
ncetate of copper. With respect to this process M. Fontaine observes : 
*^ It is evident that a coating of copper so deposited can be x)os6es8ed 
of no other solidity than its own, and the latter is entirely dependent 
on the thickness and tenacity of the deposit M. Oudry was accord- 
ingly led to effect depositions having one-half a millimetre on ordimiry 
objects and one millimetre or more on fine works. If to that thick- 
ness is added those of a layer of plumbago and three layers of insu- 
lating coating material, it will be readily conceived that such a system 
of coppering is only suitable in the case of very large objects. In 
the case of small objects— such as a bust, for example — the nicety of 
the details would be irretrievably spoiled by these five layers, and it 
would amoimt to sacrificing to too great an extent the artistic worth 
of the object for the purpose of attaining its preservation. It is, 
nevertheless, certain that this process has really become a branch of 
industry, and that it is the first one which has been applied on a large 
scale. All the lamp-posts of the city of Paris, the beautiful fountains 
of the Place de la Concorde and of ihe Place Louvois, and a consider- 
able number of statues and bas-reliefs, have been coppered at Auteuil, 
in the inventor's factory." It appears that M. Oudry' s son subse- 
quently modified the above process by substituting for the coatings 
of paint and plumbago an immersion of the oast-iron objects in a 
thick paint composed of hot oil and copper-dust suspended in the 
liquid. The objects, when removed from this bath, are first dried in 
an oven and then rubbed with a wire-brush and copper dust. They 
are afterwards immersed in a sulphate of copper bath. 

It is obvious that in either of the above processes a quantity of 
copper far in excess of what would be required as a protective coating 
for iron — provided it could be deposited direct upon the metal — must 
from necessity be deposited upon the plumbagoed, or copper-dusted 
surface ; and it is also clear that sruce the copper represents merely a 
thin shell upon the surface, that a very moderate amoimt of rough 
usage, such as the Parisian gamiti or Loodon street Arab could inflict 
on very easy terms, by the simple process of climbing the lamp -posts 
with metal- tipped boots, would quickly break this *' shell *' and ex- 
pose the underlying layer of plumbagoed varnish. When all these 
objections are taken into consideration — the partial obliteration of the 
finer details of the object, tlio labour, cost of material, the hngth of 
time required to complete a single article before it is ready to be placed 
in position, and add to this the constant liability to damage from 
accident or mischief, this method of coppering iron does not appear to 
have much to reconmicnd it. 



154 ELBCTBO-DEPOSTTION OF GOPPEB. - 

Oold Oosvmriim flotntioii. — One of the chief reasons why alkaline 
coppering solutions seldom work Tigorously when used at the ordinary 
temperature, is that they are too frequently prepared with oheap com- 
mercial cyanide, containing but a small percentage of real cyanide, and 
consequently overloaded with carbonate of potash, a salt which has no 
solvent action on the anode, and is of little or no service in the copper- 
ing bath. While experimenting in this direction some time since, wc 
found that a g^ood coppering solution, to be worked in the cold, could 
be prepared from the following formula ; but it is essential that the 
cyanide be of good quality. For each gallon of solution required, 
3 ounces of chloride of copper are to be dissolved in about a pint and 
a-half of cold water ; 12 ounces of soda crystals are next dissolved in 
about a quart of water. The latter solution is then to be gradually 
added to the chloride of copper solution, with gentle stirring after each 
addition, until the whole of the alkaline liquid has been added, when 
the resulting carbonate of copper is allowed to settle. After an hour or 
so the supernatant liquor is poured off and fresh water added to wash 
the precipitate, which is again allowed to subside as before, the wash- 
ings being repeated several times, and the precipitate then dissolved 
in a solution of cyanide of potassium composed of six ounces of the 
cyanide dissolved in about a quart of water, the whole being well 
stirred imtil the copper salt has become dissolved. The solution thus 
formed is now to be set aside for several hours and the clear liquor 
then carefully decanted from any sediment that may be present ; 
water is then added to make up one gallon of bath. This solution 
will coat cast or wrought iron very readily with a current from two 
to three Daniells, in series, and may be used to give a preliminary 
coating to iron work which is to be afterwards thickly coppered in an 
ordinary sulphate bath. The anode used in this, and all other alkaline 
coppering baths, should be of pure electrolytic copper. 

OoFPevinff 8t««l Wlro for Telegraphle PnxpoMS. — It had 
always been held that if iron wire could be successfully and economi- 
cally coated with copper, it would be of incalculable service in tele- 
graphy ; and, indeed, many attempts to accomplish this were made at 
a period when magneto and dynamo -electric machines were unknown. 
It soon became apparent, however, that, independent of other difficulties, 
the object could never be practically attained by means of the voltaic 
battery. Now that we are enabled to obtain electricity simply at the 
cost of motive power, that which was impossible thirty years ago has 
been to some extent accomplished, and the copi>ering of steel wire for 
telegraph purposes forms an extensive branch of manufacture in con- 
nection with one of the telegraph systems of America. The manu- 
facture of ** compound wire," as it is called, has been carried out on 
a very large scale at Ansonia, Connecticut, by the Postal Telegraph 



OOPPfiRTKO 1EI0LDTI0N8. 155 

Company, who, Profeeeor Silliman, of Yale College, U.S.A., statos, 
ha,re acquired "the largest electro-plating establishment in the 
world ; yet its (capacity is soon to be trebled. The works are em- 
ployed in coppering steel wire used in the company*8 system of 
telegraphy, and now deposit two tons of pure copper per day. The 
steel core of the wire gives the required tensile strength, while the 
copper coating gives extraordinary conducting power, reducing the 
electrical resistance enormously. The compound wire consists of a 
steel wire core weighing 2cx> lbs. to the mile, and having a tensile 
strength of 1650 lbs., upon which copper is deposited, by dynamo- 
electricity, of any required thickness. Twenty-five large dynamo 
machines are employed, which deposit collectively 10,000 lbs. of 
copper per day, representing 20 miles of 'compound wire,' carry- 
ing 500 lbs. of copper to the nule. When the works are completed, 
three 300 horse-power engines will drive dynamo machines for sup- 
plying the current to deposit copper upon 30 miles of wire per day. 
In the process of deposition the wire is drawn slowly over spiral coils, 
through the depositing vats, until the desired thickness is obtained.** 
The advantages of coppered steel wire over ordinary galvanised iron 
wire for telegraph purposes cannot well be over-estimated, and if 
the process prove as successful as it is stated to be, it will un- 
doubtedly be a great electrolytic achievement. 

Oopparlntf Bolnttons. — In preparing alkaline coppering solutions, 
for depositing a preliminary coating of copper upon iron, and for 
other purposes of electro-coppering, either of the formulse for brass- 
ing solutions may be used,* by omitting the zinc salt and doubling the 
quantity of copper salt ; or either of the following formulfie may be 
adopted. As a rule, copper solutions should be worked hot, say at a 
temperature of about 130° Fahr., with an energetic current, especially 
for cast-iron work, since even with the best solution deposition is but 
slow when these solutions are worked cold. It is important to bear 
in mind in making up copper solutions — and the same observation 
applies with at least equal force to brassiag solutions — that commer- 
cial cyanide of potassium is largely adulterated with an excess of car- 
bonate of potash, and unless a cyanide of known good quality be 
employed, the solution will be not only a poor conductor of the cur- 
rent, but the anodes will fail to become freely dissolved, whereby the 
solution will soon become exhausted of a greater portion of its metal 
in the process of deposition. The cyanide to be used for making up 
such solutions should contain at least 75 per cent, of real cyanide. 

Solution I. — Dissolve 8 oiuicea.of sulphate of copper in about 
I quart of hot water ; when cold, add liquid AmmnTtifl. of the specific 
gravify of -880 gradually, stirring with a glass rod or strip of wood 
S^ier each addition, until the precipitate which ut first forms becomes 



* See pp. 374 et aeq. 



y I 



156 



BLBCTBO-DBPOSITION OF OOPPER. 



re-diasolved ; dilate the solution by adding i quart of cold water. 
Sow prepare a solution of cyanide of potassium by dissolving about 
1} lb. of the salt in 2 quarts of water, and add this gradually to the 
copper solution, with stirring, until the blue colour of the ammonlo- 
sulphate entirely disappears ; finally add the remainder of the cyanide 
solution, and allow the mixture to rest for a few hours, when the 
clear liquor may be decanted into the depositing vessel or tank, and 
is then ready for use. This solution may be used cold, with a 
strong current, but it is preferable to work it at about 1 10° to 130* 
Fahr. 

Solution 2. — The acetate or chloride of copper may be used instead 
of the sulphate in making up a coppering bath, the latter salt being 
pfeferable. 

Solution 3. — ^A solution prepared as follows has been recommended : 
I>1uhu1tu cyanlfle of copper in a solution of cyanide of potassium, con- 
sisting of 2 pounds of cyanide to I gallon of water, then adding about 
4 ounces more of the salt as free cyanide ; the solution is then ready, 
and should be worked at a temperatiu'e of about 150° Fahr. Cyanide 
or copper is not freely soluble in a solution of cyanide of potassiunu 
and the liquid does not readily dissolve the anodes, nor is it a good 
conductor. It has also a tendency to evolve hydrogen at the cathode ; 
this, however, may be lessened or wholly prevented by avoiding the 
use of free cyanide, employing a weaker current, and adding liquid 
ammonia and oxide of copper. From our own experience, the addi- 
tion of liquid ammonia to copper solutions, if not applied in the first 
instance, becomes a necessity afterwards. 

Solution 4. — ^Boseleur gives the following formula for a coppering 
solution : 20 parts of crystallised acetate of copper are reduced to a 
powder, and formed into a paste with water ; to this is added 20 parts 
of soda crystals, dissolved in 200 parts of water, the mixture being 
well stirred. To the green precipitate thus formed, 20 parts of bisul- 
phite of sodium, dissolved in 200 parts of water, are added, by which 
the precipitate assumes a dirty yellow colour. 20 parts of pure cyanide 
of potassium, dissolved in 600 parts of water, are finally added, and 
the whole well stirred together. If the solution does not become 
colourless, an addition of cyanide must be given. It is said that this 
solution may be worked either hot or cold, with a moderately strong 
current. 

Dk, Slaner's ftolntion. — In the preparation of this solution, i part 
of powdered bitartrate of potassium is boiled in 10 parts of water, and 
as much recently prepared and wet hydrated carbonate of copper, 
which has been washed with cold water, stirred with it as the above 
solution will dissolve. The dark blue liquid thus formed is next fil- 
tered, and af terwuiHls rendered still more alkaline by adding a small 



WALENN^B OOPPERIMG SOLUTIONS. T $7 

quantity of carbonate of potash. This solution is stated to be appli- 
cable to coating iron, tin, and zinc articles.* 

WalAim's Copperiiiff Bointioii. — ^This solution, to be employed 
for coppering iron, consists in dissolving cyanide of copper in a solu- 
tion composed of equal parts of cyanide of potassium and tartrate of 
ammonia. Oxide of copper and ammoniuret of copper are added in 
sufficient quantity to preyent the eyolution of hydrogen at the surface 
of the work during deposition. The soluticm is worked at about i8o° 
Fahr. The current from one Smee cell may be used with this solution. 
It has been found that i^ ounce of copper per square foot will pro- 
tect iron from rust. 

Another process of Mr. Walenn's is as follows : — 

The first part of this invention ''relates to electro-depositing 
copper upon iron, or upon similar metals, so that the coating 
may be soft and adherent. This consists in using the solution at 
a boiling heat, or near thereto, namely, from 150° Fahr. to the 
boiling point of the solution. The second part is to provent the 
evaporation of a solution which is heated during deposition. A 
cover, with a long condensing worm tube, is used in the depositing 
bath ; the other end of the tube opens into a box containing 
materials to condense or appropriate the gases that escape. The 
liquids flow back down the tube into the tank. The third part 
of the invention consists in working electro-depositing solutions in a 
closed vessel under known pressure, being applied by heating the 
solution or otherwise. The closed vessel may be used for solutions in 
which there is free ammonia, or where other conditions arise in which 
it is necessary to enclose the solution, although neither appreciable 
increase of pressure arises nor is heat applied. If thero be much gas 
coming ojf , the condensing tube, opening into a box of the second 
part of the improvements, may be employed." The fourth part of the 
invention consists in adding to the charged, and fully made, copper, 
brassing, or bronzing solution, oupric ammonide in the cold, until tlie 
solution is slightly green. 

Chiimaolm'a Frooaas. — ^A bath is made by first obtaining a solution 
of chloride of copper, the metal from which is precipitated in the form 
of phosphate, by means of pyrophosphate of soda. The precipitate 
is then thoroughly washed until all traces of the chloride of soda 
formed have been removed ; the phosphate of copper is next dissolved 
in a solution of caustic soda, and, if necessary, a small quantity of 
liquid ammonia is added to assist the solution of the phosphate, and 
to render the deposit brighter and moro solid. The strength of the 
solution must be regulated according to the strength of the current 



* J%e Chemitt, vol. vii. p. 124. 



/ 



15^ ELECTBO-DBPOBinON OF OOPPEB. 

employed in the deposition. The bath may bo used for depoeituig 
upon iron or other metals. 

Well's Oopp«rinip riucsMaa. — (i.) For coating large objects, as 
cast-iron fountains, lamp-posts, &o. M. Weil's patent gives the fol- 
lowing process : Dissolve in [,ooo parts of water, 150 of sodio- 
potassic tartrate (Bochelle salt), 80 of caustic soda, containing from 
50 to 60 per cent, of free soda, and 35 of sulphate of copper. Iron 
and steel, and the mellis whose oxides are insoluble in alkalies, are 
not corroded in this solution. The iron or steel articles are cleaned 
with dilute sulphuric acid, of specific gravity 1*074, by immersing 
them in that liquid from five to twenty minutes, then washing with 
water, and finally with water made alkaline by soda. They are 
next cleaned with the scratch-brush, again washed, and then 
immersed in the cupreous bath, in contact with a piece of zinc 
or lead, or suspended by means of zinc wires ; the latter is the 
most economical way. The articles must not be in contact with 
each other. They thus receive a strongly -adherent coating of copper, 
which increases in thickness (within certain limits) with the dura- 
tion of immersion. Pure tin does not become coppered by contact 
with zinc in this solution ; it oxidises, and its oxide decomposes the 
solution, and precipitates red sub-oxide of copper, and by prolonged 
action, all the copper is thus removed from the liquid. The iron 
articles require to be immersed from three to seventy-two hours 
according to the colour, quality, and thickness of the required deposit. 
The copper solution is then run out of the vat, and the coated articles 
washed in water, then cleaned with a scratch-brush, washed, dried in 
hot sawdust, and lastiy in a stove. To keep the bath of uniform 
strength, the liquid is renewed from below, and flows away in a small 
stream at the top. After much use, the exhausted liquid is renewed 
by precipitating the zinc by means of sulphide of sodium (not in 
excess), and re-charging the solution with cupric sulphate. Weil 
also suppUes to the bath hydrated oxide of copper. 

(2.) A coppering bath is prepared as follows : 35 parts of crystal- 
lised sulphate, or an equivalent of any other salt of copper, are 
precipitated as hydrated oxide by means of caustic soda or potash. 
The oxide of copper is to be added to a solution of 150 parts of 
Roohelle salt, and dissolved in 1,000 parts of water. To this, 60 parts 
of caustic soda, of about 70 per cent., is to be added, when a clear 
solution of copper will be obtained. Other alkaline tartrates may be 
substituted for the Bochelle salt above mentioned, or even tartaric acid 
may be employed ; but in the case of tartaric add, or acid tartrates, 
a smaU additional quantity of caustic alkali must be added, sufBlcient 
to saturate the tartaric acid or acid tartrate. Oxide of copper may 
also be employed, precipitated by means of a hypochlorite, but in all 



ELEGTBO-BTCHIMO. 1 59 

cases the propoitions between the copper and tartaric acid ahonld be 
maintained as abbve, and it is advantageous not to increase to any- 
notable extent the proportion of the caustic soda. 

The object to be coppered is to be cleaned with a scratch-brush and 
then placed in the bath, when it will become rapidly coated with an 
adherent film of metaUio copper. As the bath gradually loses its 
copper, oxide of copper as above prepared should be added to main- 
tain it in a condition of activity, but the quantity of copper introduced 
should never exceed that above prescribed, as compared with the 
quantity of tartaric acid the bath may contain. If the copper notably 
exceeds this proportion, certain metallic iridescences are produced on 
the surface of the object. These effects may be employed for orna- 
mental and artistic puzposes. According to the time of the immersion, 
the strength of the current, and the proportion of copper to the tartaric 
add, these iridescences may be produced of different shades and tints, 
which may be varied or intermingled by shielding certain parts of the 
object by a coating of paraffin or varnish, the iridescent effect being 
produced on the parts left exposed. All colours, from that of brass to 
bronze, scarlet, blue, and green, may be thus produced at will. 

BXeetro-Btebins. — ^When we bear in mind the fact that, with few 
exceptions, the anodes employed in electrolytic processes become dis- 
solved in the bath during electro-deposition, it is evident that if 
certain portions of an anode were protected, by means of a suitable 
varnish, from the solvent action of the solution, that such parts, after 
the plate had been subjected to electro-chemical action in the bath, 
would, on removal of the varnish, appear in relief, owing to the 
exposed surfaces having been reduced in substance by being partially 
dissolved in the solution. Suppose a smooth and bright plate of cop- 
per, for instance, were to have a design sketched upon it with a 
suitable varnish, and the plate then connected to the positive electrode 
of a voltaic battery and immersed in a solution of sulphate of copper, 
a cathode of the same metal being suspended from the negative elec- 
trode ; if, after a few hours' immersion, the plate be taken from the 
bath, and the varnish removed, the design will appear in bright re- 
lief, while the unvarnished parts will have been eaten away, or 
dissolved, leaving hollows of a comparatively dull appearance ; the 
design now forms a printing surface, from which copies may be im- 
pressed upon paper in the usual way. 

The process of voltaic etching is performed in various ways, but the 
following will explain the general principle upon which the art is con- 
ducted. A copper wire is first soldered to the plate, and the back is 
then coated with a tough varnish ; when this is dry, the face of the 
plate is coated with engraver ^s *' etching-groimd," a composition of 
beeswax 5 parts, linseed oil i part, melted together ; it is sometimes 



l6o ELECTRO-DEPOSITION OF COPPER. 

the practice to jwioke the surface, before applying the etching' needle, 
in order to render its tracings more visible. The detdgn is then 
drawn upon the face of the plate, catting through to the clean surface 
of the copper. When the etching is complete, the plate is made the 
anode in a sulphate of copper bath, while a plate of copper is im- 
mersed as the cathode. The electric current, passing out of the 
engraved lines, causes the copper to be dissolved from them, whereby 
they become etched, much in the same way, and with the same effect, 
as when aoid is used in the ordinary etching process. The required 
gradations of light and shade are produced by suspending cathodes 
of different forms and sizes opposite the plate to be etched, in various 
positions, and at different distances from it, thus causing the plate to 
be acted upon in unequal depths in different parts, the deepest action 
being always at those portions of the electrodes which are nearest 
to each other. 
Instead of using wax, or other etching-g^round, as an insulating 

material, the plate may be coated with a film of some metal which 
will not be dissolved in the bath. For example, the plate may be first 
strongly gilt by electro-deposition, and the design then produced by 
means of a graver, the tool cutting just sufficiently deep to expose the 
copper ; if now the plate be used as an anode, the copper will become 
dissolved, as before, leaving the gilt surface unacted upon, since the 
sulphuric acid set free during the voltaic action has no effect upon gold. 

Again, the design may be made with lithographic ink or varnish, 
and the exposed parts of the plate then strongly gilt ; if, thereafter, 
the varnish, or other insulating material be cleaned off the plate, the 
voltaic etching will follow the ungilt portions, causing them to be- 
come hollowed out as before. 

The baths used for etching by electrolysis should be composed of the 
same metal as that to be etched ; thus, a sulphate of copper bath is 
employed for etching copper plates, sulphate of zinc for zinc plates, 
and gold or silver solutions when their metals are to be treated in the 
same way. Copper and zinc plates, however, may be etched by 
means of the voltaic battery, in dilute solutions of nitric, sulphuric, 
hydrochloric, or acetic acid, a process which is said to be coming very 
much into practice. 

Olirpbograpliy. — ^This process was invented by Mr. £. Palmer, and 
consists in first staining copper plate black on one side, over which a 
very thin layer of a whit^ opaque composition, resembling white wax, 
is spread. The plate is then drawn upon with various etching needles 
in the usual way, which remove portions of the white composition, by 
which the blackened surface becomes exposed, forming a strong con- 
trast to the surrounding white ground. When the drawing is com- 
plete, it is carefully inspected, and then pasijes into a third person's 



MAKING ELEOTBOTTEB PLATES FBOM DBAWING8. l6l 

hands, ** by whom it is brought in contact with a substance having a 
chemical afiSnity for the remaining portions of the composition, by 
whom they are heightened, ad libtium. Thus, by careful manipula- 
tion, the lights of the drawing become thickened all over the plate 
equally. . . . The depths of these non-printing parts of the block 
must be in some degree proportionate to their width ; consequently 
the larger breadths of lights require to be thickened on the plate to a 
much greater extent. It is indispensably necessary that the printing 
surfaces of the block prepared for the press should project in such 
relief from the block itself as shall prevent the inking roUer touch- 
ing the interstices ; this is accomplished in wood engraving by cutting 
out these intervening parts, which form the lights of the print, to a 
sufficient depth ; but in glyphog^phy the depth of these parts is 
formed by the remaining portions of the white composition on the plate, 
analogous to the thickness or height of which must be the depth on the 
block, seeing that the latter is in fact a cast or reverse of the former.*' 
The plate, thus prepared, is weU plumbagoed all over, and is then 
placed in a sulphate of copper bath, and a deposit of sufficient thick- 
ness obtained, which, on being separated, will be found to be a perfect 
cast of the drawing which formed the cliche. The metallic plate thus 
obtained is afterwards backed up with solder and mounted in the 
same way as a stereotype plate, and is then ready for the printing press. 

MaVtng Oopp«r asoulds 1»y Slaetrolysli. — ^A drawing is made 
upon a varnished copper plate, as before described ; the plate is then 
dipped into a weak ** quicking " solution, and then laid upon a. flat 
and level surface. The mercury attacks the surfaces exposed by the 
graver or etching needle, and takes the meniscus^ or curved form, that 
is, the relief is greater as the etching lines are larger ; the drawing, 
therefore, is reproduced in relief by the mercury. The plate is next 
covered with a thin paste of plaster of Paris, and when this has 
set, the two moulds are to be separated. A counter mould may 
now be taken from this, or it may be prepared in the usual way, 
and, after being weU plumbagoed, receive a deposit of copper. By 
the following plan a mould is produced, which is at once ready 
for the bath. A copper plate is varnished and etched as before. A 
neutral solution of chloride of zinc is then poured upon the plate, and 
after this a quantity of fusible metal, which melts at from 175" to 
212** Fahr. The flowing of the fusible metal over the surface of the 
plate is aided by the application of a spirit-lamp held beneath the 
plate, or by spreading the metal over the surface with a hot iron rod. 
The mould thus obtained may then be reproduced by the ordinary 
electrotype process. 

MaMwg Btoo tr o iyv Flatas tmoL Brawings. — This invention 
relates to an improved process of forming matrices of designs for the 

u 



1 62 ELECTRO-DEPOSITION OP COPPER. 

production of electrotype plates directly by the hand of the artist or 
deoigner, in which the design is produced by means of a pointed tool 
upon a thin sheet of soft metal supported upon a peculiar backing of 
semi -plastic inelastic material of sufficient body or consistence to sup- 
port the metal without pressure, but sufficiently yielding to give to 
the slightest touch of the artist, and allow the material to be depressed 
under the tool for the formation of the lines of design. In carrying 
out this inTention a mixture is made of plaster of Paris i lb., chro- 
mate of potassa ^ oz., and conmion salt, I oz., which forms a com- 
pound tliat will give the most delicate touch of the artist, and will 
allow the finest lines to be produced upon the metal by the tool. 
These ingredients may be mixed in various proportions, which will 
depend somewhat upon the boldness or delicacy of the design to be 
produced. The mixture may be brought to a semi-plastic state by 
the addition of about i pint of water, or sufficient to bring it to the 
proper consistence, and the plasticity of the compound DMiy be modi- 
fied to suit various requirements by using more or less water. The 
semi-plastic composition is moulded or otherwise formed into a flat 
tablet of suitable size, and a sheet of soft metal is carefully secured on 
the upper face of same, projecting edges being left, which are after- 
wards turned down over the sides of the tablet. The metal is then 
ready for the artist, who, with a pointed tool or tools, produces the 
required design by indenting the lines thereon. "Wherever touched by 
the tool the metal will be depressed into the backing, which has just 
sufficient body to support the untouched parts, but yields to the 
slightest pressure of the tool. When the design is finished, the 
metal is carefully removed from the backing, having the design in 
relief on one side and in intaglio on the other, and is ready for the 
production of the electrotype plate in the ordinary way, which may 
be taken from either side, as circumstances require. 

Copperins Steel Bitot.— The electro-dejiosition of copper is being 
extensively applied by the Nickel Plating Company, Greek Street, 
Soho, London, to the coating of large and small steel shot with copper 
for the Nordenfelt gun. 

Oopperlns ITotes. — i. In preparing cast-iron work for electro- 
coppering, after the pieces have been pickled and scoured, they should 
be carefully examined for sand-holes, and if any such cavities appear 
upon the work, they must be well cleared from bla<ik or dirty matter, 
wliich may have escaped the brushing, by means of a steel point. It 
nmst always be borne in mind that copper, and indeed all other metals, 
refuse to deposit upon dirt. After having cleared out the objectionable 
matter from the sand-holes, and again well brushed the artic^le with 
sand and water, it is a good plan to give tho piece a slight coating of 
copper in the alkaline bath, and then to uxaniino it again, when if 



COPPERING NOTES. 1 63 

any oavitiefi show signs of being foul, they must be cleared with the 
steel point as before. The article should then have a final brushing 
-with moist sand, and after well rinsing be placed in the alkaline 
coppering bath and aUowed to remain, with an occasional shifting of 
position, until sufficientlj coated. If the piece of work is required to 
have a stout coating of copper, it should receiye only a moderate 
deposit in the cyanide bath, and after being well rinsed suspended in 
the sulphate of copper, or acid bath, as it is sometimes termed, and 
allowed to remain therein until the desired coating is obtained. To 
secure an uniform deposit, however, the object should be occasionally 
shifted while in the bath, except when mechanical motion is applied, 
as in coppering iron rollers and other similar work. 

2. Respecting the working of copper solutions, Gore makes the 
following observations : '* If the current is too great in relation to 
the amount of receiving surface, the metal is set free as a brown or 
nearly black metallic powder, and hydrogen gas may even be deposited 
with it and evolved. In the sulphate solution, if the liquid is too 
dense, streaks are apt to be formed upon the receiving surface, and 
the article (especially if a tall one) will receive a thick deposit at its 
lower part, and a thin one at the upper pcMlion, or even have the 
deposit on the upper end redissolved. If there is too little water, 
crystals of sulphate of copper form upon the anode, and sometimes 
even upon the cathode, at its lower part, and also at the bottom of 
the vessel. If there is too much acid the anode is corroded whilst 
the current is not passing. The presence of a trace of bisulphide of 
carbon in the sulphate solution will make the deposit brittie, and this 
continues for some time, although the solution is continually deposit- 
ing copper ; in the presence of this substance the anode becomes black, 
but if there is also a great excess of acid, it becomes extremely bright. 
Solutions of cupric sulphate, containing sulphate of potassium, and 
the bisulphide of carbon applied to them, are sometimes employed for 
depositing copper in a bright condition. The copper obtained from 
the usual double cyanide of copper and potassium solution, by a weak 
current, is of a dull aspect, but with a strong current it is bright." 
For depositing copper from alkaline solutions, we prefer the Bunsen 
battery to all others. 

3. The anodes used in electrotyping, as also those employed for depo- 
siting copper generally, should consist of pure electrolytic copper, in 
preference to the ordinary sheet metal, which invariably contains 
small traces of arsenic and other metals, which are known to diminish 
its conductivity considerably. Clippings and other fragments of cop- 
per from elcctrotjrpes n^y be used up as anodes, either by suspending 
tiiem in a platinimi-wire cradle or in a canvas bag, the fragmenb: 
being put in connection with the poaitive electrode of the battery by 



1 64 ELECTRO-DEPOSITION OF COPPER. 

meanB of a stout rod or strip of copper. Hiese make-shift anodea, 
however, should be used for thickening the deposit (if an eleotiotype) 
after the mould is completely coated with copper, and not in the earlier 
stage of the process. 

4. When it is desired to obtain an electroiype of considerable thick- 
ness, this may be hastened in the following way : After the complete 
shell is obtained, clean copper filings are to be sifted oyer the surface, 
and deposition allowed to proceed as usual, when the newly deposited 
metal will unite with the copper filings and the original shell, and 
thus increase the thickness of the electrotype. By repeated additions 
of copper filingps, followed by further deposition of copper, the back 
of the electroty})e may be strengthened to any desired extent. 

5. For coating with copper non-conducting substances, such as 
china or porcelain, the following process has been adopted in France : 
Sulphur is dissolved in oil of spike lavender to a sirupy consistence, to 
which is added either chloride of gold or chloride of platinum, dissolved 
in other, the two liquids being mixed under gpentle heat. The com- 
pound is next evaporated until it is of the consistency of ordinary 
paint, in which condition it is applied with a brush to such parts of a 
china or porcelain article as it is desired to coat with copper ; the 
article is afterwards baked in the usual way, after which it is immci*sed 
and coated with copper in the ordinary sulphate bath. 



CHAPTER IX. 
DEPOSITION OF GOLD BY SIMPLE IMMERSION. 

Prepartion of Chloride of fJold.— Water Gilding.— Gilding by Immersion in 
a Solution of Chloride of Gold. — Gilding by Immersion in an Ethereal 
Solution of Gold. — Solution for Gilding Brass and Copper. — Solution 
for Gilding Silver. — Solution for (Hiding Bronze.— French Gilding for 
Cheap Jewellery.— Colouring Gilt Work. — Gilding Silver by Dipping, 
or Simple Immersion.— Preparation of the Work for Gilding. — Gilding 
by Contact with Zinc, Steele's Proces.4. — Gilding with the Rag. 

nr^panttton of GblOKidm of Oold. — Since for all gilding purpofles 
by ihe wet way^ an we may term it in contradistinction to the process 
of mercury g^ding, thlA metal requires to be brought to the state of 
tolutioHt it will be well to explain the method of preparing the salt 
of gold commonly known as the chloride of gold, but which is, strictly 
speaking, a terehhride of the metal, since it contains three equivalents 
of chlorine. The most convenient way of dissolving the precious 
metal is to carefully place the required quantity in a glass flask, such 
as is shown in Fig. 70, and to pour upon it a mixture consisting of 
about 2 parts of hydrochloric acid and i part 
nitric acid hy meamre. This mixture of acids was 
called aqtta reyia by the ancients because it had 
the power of dissolving the king of metals — grold. 
To dissolve i ounce of gold (troy weight) about 
4 ounces of aqua regia will be required, but this 
will depend upon the strength of the commercial 
acids. Soon after the mixed acids have been 
poured on the gfold, gas is evolved, and the 
chemical action may be accelerated by placing 
the flask upon a sand-bath moderately heated. 
It is always advisable, when dissolving this or 
other metal, in order to avoid excess of acid. Fig. 70. 

to apply less of the solvent than the maximum 
quantify in the first instance, and, when the chemical action has 
ceased, to pour off the dissolved metal and then add a further portion 
of the solvent to the remainder of the undissolved metal, and so on 





t66 deposition of gold by simple immrrston. 

until the entire quantity is dissolved without any appreciable excess 
of acid, after which the various solutions are to be mixed together. 

The solution of chloride of gold is to be carefully poured into a 
porcelain evaporating dish* (Fig. 71), and this, placed on a sand-bath 
or otherwise, gently heated until nearly all the acid is expelled, when 
the solution will assume a reddish hue. At this period the author 
prefers to move the evaporating dish round and round gently so as to 
spread the solution over a large surface of the interior of the vessel ; 

in this way the evaporation of the acid is hastened 
considerably. When the solution assumes a blood- 
red colour the dish should be gently, but repeatedly, 
moved about as before until the semi-fluid mass — 
Fig. 71. which gradually becomes deeper in colour and more 

dense in substance — ceases tojfow. Towards the end 
of the operation the last remaining fluid portion flows torpidly, like 
molten metal, until it finally ceases altogether, at which moment the 
dish should be removed from the sand-bath and allowed to cool. It 
is necessary to mention that if too much heat be applied when the 
solution has acquired the blood-red colour the gold will quickly become 
reduced to the metallic state. If such an accident should occur the 
reduced metal, after dissolving out the chloride with distilled water, 
must be treated with a little aqua regia^ which will again dissolve it. 

The red mass resulting from the above operation (if properly con- 
ducted) is next to be dissolved in distilled water, in which it is readily 
soluble, and should form a perfectly clear and bright solution of a 
brownish-yellow colour. If, on the other hand, the evaporation has 
not been carried to an extent sufficient to expel all the acid the solu- 
tion will be of a pure yellow colour. It invariably happens, after 
the chloride of gold is dissolved in water, that a white deposit re- 
mains at the bottom of the evaporating dish — this is chloride of silver, 
resulting from a trace of that metal having been present in the gold. 

Watar-Oildiiis. — Previous to the discovery of the electrotype pro- 
cess and the kindred arts of electro-gilding and silvering to which it 
gave rise, a process was patented by Mr. G. R. EUdngton for gilding 
metals by the process of simple immersion or *' dipping, ^^ and this 
process, which acquired tlie name of water 'gilding, was carried on by 
Messrs. Elkington at Birmingham for a f^'^nsitlerable time with snooess 
for a certain class of cheap jewellery. The solution was prepared as 
follows: A strong solution of chloride of gold was first obtained, to 
which aeid carbonate of potash was added in the proportion of i part of 
gold, in the form of chloride, to 3 1 parts of the acid carbonate ; to this 
mixture was added 30 parts more of the latter salt previously dis- 



* Evaporating dishes made from Berlin porcelain are the bent for this 
purpose, siDCA thev are not liable to 'track when heatod. 



SOLUTION FOR OILDTNO RTLVER. l6j 

flolved in 200 parts of water. The mixture was then boiled for two 
hours, during which period the solution, at first yellow, assumed a 
green colour, when it was complete. To apply the above solution the 
metal articles, of brass or copper, are first well cleaned and then 
immersed in the solution, which must be hot, for about half a minute. 
Articles of sUver or German -silver to be gilt in this solution must be 
placed in contact with either a copper or zinc wire. 

Olldliis 1»y XmnMnlon In a Solutloii of tbe Cliloride of Gold. 
— ^Articles of steel, silver, copper, and some other of the baser metals, 
may be gUt by simply immersing thom in a weak solution of the 
chloride of gold ; this is, however, more interesting as a fact than of 
any practical value. 

CMldlns 1»y TmnKwnrtoB In an Btli«real Solution of Oold. — 
Chloride of gold is soluble in alcohol and in ether. The latter solu- 
tion may be obtained by agitating a solution of gold with ether, after 
which the mixture separates into two portions ; the upper stratum, 
which is of a yellow colour, is an ethereal solution of chloride of 
gold, while the lower stratum is merely water and a little hydrochloric 
acid. Steel articles dipped in the ethereal solution become instantly 
covered with gold, and, at one time, this method of g^ding steel was 
much employed for delicate surgical instruments, as also for the orna- 
mentation of other articles of steel. After being applied, the ether 
speedily evaporates, leaving a film of gold upon the object. If 
the ethereal solution be applied with a camel-hair brush or quill pen, 
initials or other designs in g^ld may be traced upon plain steel 
surfaces. Or, if certain portions of a steel object be protected by 
wax or varnish, leaving the bare metal in the form of a design, the 
ethereal solution may then be applied to the exposed surfaces, which 
will appear in gold when the wax or varnish is dissolved or otherwise 
cleared away. Various ways of applying this solution for the orna- 
mentation of steei will naturally occur to those who may be desirous 
of utilising it. 

Bolntlon Ibr CMldlns Brafls and Oovp«r. — The following formula 
has been adopted for ^'water-gilding " as it is termed : — 

Fine gold 6} dwts. 

Convert the gold into chloride, as before, and dissolve it in i quart of 
distilled water, then add 

Bicarbonate of potassa . . . i lb. 

and boil the mixture for two hours. Immerse the articles to be gilt 
in the worm solution for a few seconds up to one minute according to 
the activity of the bath. 

861ntlon Ibr CHldlns Sllvar. — Dissolve equal parts, by weight, of 
bichloride of mercury (corrosive subUmate) and chloride of ammonium 



l68 DEPOSITION OF GOLD BT SIMPLE IMMERSION. 

(flal-ammoniao), in mtrio aoid ; now add some grain gold to the mixtore 
and evaporate tiie liquid to half its bulk ; apply it, whilst hot, to the 
surface of the silver article. 

■otatlon fbr CMldins Bvons^, Sto, — ^A preparatory film of gold 
may be given to large bronze articles that are to be fully gplt by either 
of the prooesses hereafter described, or small articles of *< cheap" 
work may be g^t by immersing them in the following solution, which 
must be used at nearly boiling heat : — 

Caustic potash x8o parts 

Carbonate of potash ... 20 „ 

Cyanide of potassium ... 9 „ 

Water 1,000 „ 

Bather more than 1} part of chloride of g^ld is to be dissolved in 
the water, when the other substances are to be added and the whole 
boiled together. The solution requires to be strengthened from time 
to time by the addition of chloride of gold, and also, after being 
worked four or five times, by additions of the other salts in the pro- 
portions gfiven. This bath is recommended chiefly for g^ding, 
economically, small articles of cheap jewellery, and for giving a pre- 
liminary coating of gold to large articles, such as bronzes, which are 
to receive a strongfer coating in the pyrophosphate bath described 
further on, or in cyanide solutions by aid of the battery. In this 
bath articles readily receive a light coating of gold, and it will con- 
tinue to work for a very long period by simply adding, from time to 
time as required, the proper proportions of gold and the other sub- 
stances comprised in the formula. By keeping the bath in proper 
order a very larg^ number of small articles may be gilt in it at the 
expense of a very small proportion of gold. 

Another method of gilding by simple immersion, applicable to brass 
and copper articles, is to first dip them in a solution of proto- 
nitrate of mercury (made by dissolving quicksilver in nitric acid 
and diluting with water), and then dipping them into the gilding 
liquid — ^this plan being sometimes adopted for largfe articles. It is 
said that copper may be gilded so perfectly by this method as to 
resist for some time the corrosive action of strong acids. During the 
action which takes place, the film of mercury, which is electro- 
positive to the gold, dissolves in the auriferous solution, and a fil^n of 
gold is deposited in its place. 

Franeli aUdlns fbr Ohmap J^wttUtry. — The bath for gilding by 
dipping, recommended by Boseleur, is composed of — 

Pyrophosphate of soda or potassa 800 grammes 

Hydrocyanic acid of I (prusAic acid) . 8 „ 

Oold in the form of chloride (crystallised) 20 „ 

pistilled water .•.,,, lo litres. 



FBBNCH OILDINO. 169 

The pjrrophosphate of soda is generally employed, and this may be 
prepared by melting, at a white heat, ordinary crystallised phosphate 
of soda in a crucible. The quantity of g^ld given in tlie above 
formula represents the grammes of the pure metal disaolved by aqua 
reg^. In making up the bath, 9 litres of water are put into a por- 
celain or enamelled-xron vessel, and the pyrophosphate added, with 
stirring, a little at a time, moderate heat being applied until all the 
salt is dissolved. The solution is then to be filtered and allowed to 
cool. The chloride of gold must not be evaporated to dryness, as 
previously described, but allowed to crystallise ; the crystals are to be 
dissolved in a little distilled water, and the solution filtered to keep 
back any chloride of silver that may be present in the dissolving flask, 
derived from the gold. The filter is next to be washed with the 
remainder of the distilled (or rain) water. The chloride solution is 
now to be added to the cold solution of pyrophosphate of soda, and 
well mixed by stirring with a glass rod. The hydrocyanic acid is 
then to be added, with stirring, and the whole heated to near the 
boiling point, when the solution is ready for use. If the pyrophos- 
phate solution is tepid, or indeed in any case, Boseleur thinks it best 
to add the prussic acid before the solution of chloride of gold is poured 
in. The employment of prussic acid in the above solution is not 
absolutely necessary, indeed many persons dispense with it, but the 
solution is apt to deposit the gold too rapidly upon articles immersed 
in it, a defect which might be overcome by employing a weaker solu- 
tion. If the solutions are cold when mixed, the liquor is of a yellow- 
ish colour, but it should become colourless when heated. It sometimes 
happens that the solution assumes a wine-red colour, which indicates 
that too littie prussic acid has been used ; in this case the acid must be 
added, drop by drop, until the solution becomes colourless. An excess 
of prussic acid must be avoided, since it has the efPect of retarding the 
gold deposit upon articles immersed in the solution. The proper con- 
dition of the bath may be regulated by adding chloride of gold when 
prussic acid is in excess, or this acid when chloride of gold predomi- 
nates. In this way the bath may be rendered capable of gilding 
without difficulty, and of the proper colour. 

Respecting the working of this solution, Roseleur says, ** The bath 
will produce very fine gilding upon well-cleaned articles, which must 
also have been passed through a very diluted solution of nitrate of 
mercury, without which the deposit of gold is red and irregular, and 
will not cover the soldered portions. The articles to be gilded must 
be constantly agitated in the bath, and supported by a hook, or placed 
in a stoneware ladle perforated with holes, or in baskets of brass 
gau2e, according to their shape or size." 

In gilding by dipping, it is usual to have three separate baths 



lyo DEPOSITION OF GOLD BY SIMPLE IMMEBSION. 

placed in succession, and close to each other, all being heated upon 
the same furnace by gas or otherwise. The first bath consists of an 
old and nearly exhausted solution in which the articles are first 
dipped to free them from any trace of acid which may remain upon 
them after being dipped in aqua fortis. The second bath, somewhat 
richer in gold than the former, is used for the next dipping, and the 
articles then receive their final treatment in the third bath. By 
thus working the baths in rounds^ *' the fresh bath of to-day becomes 
the second of to-morrow, and the second takes the place of the first, 
and so on. This method of operating allows of much more gilding 
with a given quantity of gold than with one bath alone,** and con- 
sequently is advantageous both on the score of economy and con- 
venience. The gilding is effected in a few seconds, when the articles 
are rinsed in clear water and dried by means of hot sawdust, prefer- 
ably from white woods ; they are afterwards burnished if necessary. 
Boseleur does not approve of boxwood sawdust for this purpose, since 
it is liable to clog the wet piec^ of work, besides being less absorbent 
than the sawdust of poplar, linden, or fir. The sawdust should 
neither be too fine nor too coarse, and kept in a box with two par- 
titions, with a lining of zinc at the bottom. The box is supported 
upon a frame of sheet- iron or brickwork, which admits, at its lower 
part, of a stove filled with bakers* charcoal, which imparts a gentle and 
uniform heat, and keeps the sawdust constantly dry. After drying 
very small articles in sawdust, they are shaken in sieves of various 
degrees of fineness, or the sawdust may be removed by winnow- 
ing. 

The above process of gilding by dipping, or "pot grilding,** as it 
was formerly called, is applied to articles of cheap jewellery, as 
bracelets, brooches, lockets, &c., made from copper or its alloys, and 
has been extensively adopted in France for gilding the pretty but 
spurious articles known as French jewellery. 

Colouring Gilt Work. — In working gold solutions employed in the 
dipping process, it may sometimes occur that the colour of the de- 
posit is faulty and patchy instead of being of the desired rich gold 
colour. To overcome this, certain " colouring salts'* are employed, 
the composition of which is as follows : — 

Nitrate of potash . ^ 

Sulphate of zinc • f ^- , 

Sulphate ofiron . . >• Of each equal p.rto. 

Alum ....-' 

These substances are placed in an earthenware pipkin, and melted 
at about the temperature of boiling water. When fused, the mixture 
18 ready for use. The articles are to be brushed over with the com- 



FBENCH OILDIHO. I^I 

positioD, sod are then placed in a charooal furnace in which the fuel 
bumn between tho nideg and a vertical and cylindrical grate, as Hhnwn 
inFigB. :2-3). 

The work is pkced in the hollow oentral por- 
tion where the heat radiateB. A vertical section 
of the furnace is shown in Fiff. ~J. When put 
into the furnace, the salts upon the articles flrst 
begin to dry, after which they fuse, and acquire 
a dull, yellowish-red colour. On applying the 
moistened tip of the finger to one of the pieces, 
if a slight biasing sound is heard, this indicate:* 
that the heat has been sufBcicnt, when the 
articlex are at once removed and thrown briskly 
into a very weak aulphoric acid picUe. which in 
a short time dissolves the salts, leaving the work 
clear and bright, and of a fine gold ivloiu'. It pj^ .^ 

must be borne in mind that this " colouring" 
process has a rather severe action upon gilt work, and should the gild- 
ing be a mere film, or the articles only gilt in parts, the fused salts 
will inevitably act up<m the copper of which the 
articles are made, and strip the greater portion 
of the gold from the surface ; as it would be a 
great risk to submit a large number of in- 
differently gilt articles to the colouring prooesH 
unless it was known that sufficient gold had 
been deposited upon them, although of inferior 
colour, it would be better to operate upon one or 
two samples first, when, if tho result prove 
satigfaotory, the bulk of them may then be pii-. 73. 

treated as above. Some operators, when the 
" dipping " has not been satisfactory as to colour, give the artictes a 
momentary gilding with tho battery in the usoal way. 

When it is desired to gild articles strongly by the dipping process, 
they are gilt several different times, being passed through a solution 
of nitrate of mercury previons to eooh immersion ; the film of mercury 
thus deposited on the work becomes dissolved in the pyrophoBphate 
bath, being replaced by the subsequent layer of gold. In this way 
articles may be made to receive a substantial coating of gold. In 
France, largo articles, such as clocks, ornamental bronzes, &c., are 
gilt in this manner, by which they acquire the beautiful colour for 
which French clocks and goods of a similar character are so justly 
famed. Roseleur states that he has succeeded in gilding copper by 
thia method sufficiently strong to resist the action of nitric acid for 
several hours. When articles ate strongly gilt t^ the dipping prooeaa. 



172 DEPOSITION OF GOLD BT SIMPLE IMBfBRSION. 

they may be scratoh-braBhed, or subjected to the procesfl called 
oftnouluing described in another place. 

Gilding Silver by Dipping, or Simple Immersion. — The articles are 
first cleaned and scratch-brushed, after which they are boiled for 
about half an hour in the pyrophosphate gilding bath, to which a few 
extra drops of prussic acid or sulphurous acid have been added. The 
former acid dissolves a small portion of silver from the articles, which is 
replaced by an equivalent proportion of gold, while the sulphurous acid 
acts as a reducing agent in the gold solution, and causes the metal 
to deposit upon the silver from the affinity existing between the two 
metals, especially when one of them is in the nascent state, that is, just 
disengaged from a combination. This gilding is very fine, but with- 
out firmness. The deposit is rendered more rapid and thicker when 
the articles of silver are continually stirred with a rod of copi^er. zinc, 
or brass. — Roaeleur. The deposition by contact of other metals, in, how- 
ever, due to voltaic action set up by the pyrophosphate solution, and 
is altogether different to the action which takes place during the 
simple dipping process, in which a portion of the metal of which the 
article is composed is dissolved by the solution, and replaced by an 
equivalent proportion of gold. 

Preparation of the Work for Gilding — ^As a rule, the articles should 
first be placed in a hot solution of caustic potash for a short time, 
to remove greasy matter, then well rinsed, and afterwards either 
scratch-brushed, or dipped in aqua fortis or *' dipping acid'* for an 
instant, and then thoroughly well rinsed. If the articles merely 
require to be brightened by scratch -brushing, after being g^t, it is 
only necessary to put them through the same process before gilding, 
which imparts to the work a surface which is highly favourable to the 
reception of the deposit, and which readUy acquires the necessary 
brightness at the scratch-brush lathe as a finish. Articles which are 
to be left with a dead or frosted surface, must be dipped in dipping 
acid and rinsed before being placed in the gilding bath. It is com- 
monly the practice to *' quick " the articles, after dipping in acid, by 
immersing them in a solution of nitrate of mercury until they become 
white ; after this dip, they are rinsed, and at once put into the bath. 

aUdinc by Contact wttb Zinc — Bt6«le'8 TrocMv. — In this process, 
a solution is made by adding chloride of gold to a solution of cyanide 
of potassium : in this the articles to be gilt are placed, in contact with 
a piece of zinc, which sets up electro -chemical action, by which the 
gold becomes deposited upon the articles ; but since the metal also 
becomes reduced upon the zinc, the process would not be one to re- 
commend on the score of economy. In some cases, however, in which 
it is necessary to deposit a film of gold upon some portion of an article 
which has stripped in the burnishing, a cyanide solution of gold may 
be dropped on the spot, and this touched by a zinc wire, when it will 



aiLDIMO WITH THE BA0. Z73 

receive a slight coating of gold, and thus save the necessity of re- 
gilding the whole article. This system of ** doctoring " is sometimes 
necessary, but should be avoided if possible, as it is undoubtedly a 
fraud upon the customer, since the doctored spot must, sooner or 
later, ^deld up its film of gold and lay bare the metal beneath. 

aUdiiis wltli thB Baff. — This old-fashioned process, which was at 
one time much used for gilding the insides of snuff-boxes, bowls of 
mustard and salt spoons, &c., is conducted as below. Instead of 
forming the chloride of gold in the ordinary way, the following in- 
gredients are taken : — 

Nitric acid .... 5 parts. 

Sal-ammoniac (chloride of ammonium) . . 2 „ 
Saltpetre (nitrate of potass^i) . . . . i „ 

A quantity of finely rolled gold is placed in a glass flask, and the 
other substances are then introduced ; the flask is next heated over a 
sand-bath. During the action which takes place, the nitric acid de- 
composes the chloride of ammonium, liberating hydrochloric acid, 
which combines with the nitric acid, forming aqua regia, which dis- 
solves the gold, forming chloride ; the nitrate of potash remains mixed 
with the chloride of gold. The flask is then set aside to cool : when 
cold, the contents of the flask are poured into a flat-bottomed dish, 
and pieces of linen rag, cut into convenient squares, are laid one 
above anotlier in the solution, being pressed with a glass rod, so that 
they may become thoroughly impregnated with the liquid. The 
squares of rag are next taken up, one by one, and carefully drained, 
after which they are hung up in a dark closet to dry. When nearly 
dry, each piece of rag, supported upon glass rods, is placed over a 
charcoal fire imtil it becomes ignited and burnt to tinder, which is 
promoted by the nitrate of potash ; the burning rag is laid upon a 
marble slab imtil the combustion is complete, when the ashes are to be 
rubbed with a muller, which reduces them to a fine powder. The 
powder is now collected and placed between pieces of parchment, 
round which a wet cloth is to be folded ; it is thus left for about a 
week, being stirred each day, however, to ensure an equal damping 
of the powder by the moisture which permeates the parchment. 

To apply tile powder, a certain quantity is placed on a slab and 
made into a paste with water ; the workman then takes up a small 
portion with his thumb, which he rubs upon the cleaned surface of the 
part to be gilt ; the crevices, fillets, or grooves are rubbed with pieces 
of cork cut to the shape required, for the purpose, and the comers, or 
sharp angles, are rubbed with » stick of soft wood ; such as willow or 
IX)plar. When the articles have been gilt in this way, they are 
finished by burnishing in the usual manner. When a red-coloured 
gold is required, a small portion of copper is added to the other 
ingredients when preparing the salt of gold as above described. 



CHAPTER X. 
ELECTRO-DEPOSITION OF GOLD. 

GildiDg by Eirect Current, or Electro-Gilding.— Preparation of Gilding Solu- 
tions. — Gilding Solutions : Becquerel's. — Fizeau's. — Wood's. — M. de 
Briant's. — French Gilding Solutions. — Gilding Solutions made by 
the Battery Proce»«. — De Ruolz*s. — Cold £lectro-Gilding Solutions. 
— Observations on Gilding in Cold Baths. — Ferrocyanide Gilding Solu- 
tion.— Watt's Gilding Solution.— Record's Gilding Bath. 

Oildins by IMreet Cnnrant, or BlAetzo-glldias- — ^lu gilding by 
dipping, or simple iimnersion, it is obvious that, as a rule, only a 
limited amount of gold can be deposited upon the work, and that 
the application of this method of gilding, therefore, must be confined 
to cheap classes of work, or to articles which will not be subjected to 
much friction in use. In g^ding by the separate current, on the other 
hand, we are enabled to deposit the precious metal not only of any 
required thickness, but also upon many articles which it would be 
practically impossible to gild properly by simple immersion in a solu- 
tion of gold. 

Electro -gilding is performed either with hot or cold solutions ; but 
for most practical purposes hot solutions are employed. When gold 
is deposited from cold solutions, the colour of the dei>osited metal is 
usually of a yellow colour, and not of the rich orange -yellow tint 
which is the natural characteristic of fine gold , the deposit, more- 
over, is more crystalline, and consequently more porous in cold than 
hot solutions, and is therefore not so good a protective coating to the 
underlying metal. The gold deposited from hot solutions is not only 
of a superior colour and of closer texture, but it is also obtained with 
much greater rapidity ; indeed, from the moment the articles are im- 
mersed in the gilding bath, all things being equal, the colour, thick- 
ness, and rapidity of the deposit are greatly imder the control of the 
operator. In a few seconds of time an article may bo gilded of the 
finest gold colour, with scarcely an appreciable quantity of the 
precious metal, while in the course of a very few minutes a coating of 
sufficient thickness may be obtained to resist a considerable amount 
of wear. 

The superior conductivity of hot gilding solutions enables tlie ox>crator 



GILDING SOLUTIONS. 1 75 

to gild many metallic surfaces, as tin, lead, Britannia metal, and steel, 
for example, which he could not accomplish satisfactorily with cold 
solutions ; moreover, hot gilding solutions readily dissolve any trace 
of grea^j matter, or film of oxide which may be present on the sur- 
face of the work, through careless treatment, and thus dean the 
surface of the work for the reception of the gold deposit. 

Since cold gilding solutions are occasionally used in electro -de- 
position, these will be treated separately, as also the hpecial purposes 
to which they are applied. 

Virqparation of Oildins BotntloiM. — In making up gpUding baths 
from either of the following formulae, except in such cases as will be 
specified, the gold is first to be converted into chloride, as before 
directed ; but the actual weight of the pure metal required for each 
specified quantity of solution will be given in each case. 

Of all the solutions of gold ordinarily employed in the operations of 
electro-gilding by the direct current, the double ct/anide of gold and potas- 
siufHj when prepared from pure materials, is undoubtedly the best, 
and has been far more extensively employed than any other. It is 
very important, however, in making up gold solutions, to employ the 
purest cyanide that can be obtained. A very good article, commonly 
known as ** gold cyanide,*' if obtained from an establishment of 
known respectability, is well suited to the purpose of preparing these 
solutions. The following formulae are those which have been most 
exteuKively adopted in practice ; but it may be well to state that some 
persons employ a larger proportion of gold per gallon of solution than 
that given, a modification which may be followed according to the 
taste of the operator ; but we may say that excellent results have 
been obtained by ourselves when employing solutions containing much 
less metal than some extensive firms have been known to adopt. 

aUdlBS Solnttons. — I. To make one quart of solution, convert 
I J dwt. of fine gold into chloride as before, then dissolve the mass 
in about half a pint of distilled water, and allow the solution to rest so 
that any trace of chloride of silver present may deposit. Pour the 
clear liquor, which is of a yellow colour, into a glass vessel of con- 
venient size, and then dissolve about half an ounce of cyanide in four 
ounces of cold water, and add this solution, gradually, to the chloride 
of gold, stirring with a glass rod. On the first addition of the cyanide, 
the yellow colour of the chloride solution will disappear, and on fresh 
additions of the cyanide being made, a brownish precipitate will be 
formed, when the cyanide solution must be added, gradually, until 
no further precipitation takes place. Since the precipitate is freely 
soluble in cyanide of potassium, great care must be exerciM}d not to 
add more of this solution than is necetwarv iv thn»w down the metal 
in the form of cyanide of gold. To determine the right point at which 



176 ELEOTBO-DEPOSITION OF GOLD. 

to stop, the precipitate ahould now and then be allowed to fall, ao 
that the clear supernatant liquor may be tested with a drop of the 
cyanide solution, delivered from one end of the glass rod; or a portion 
of the clear liquor may be poured into a test tube, or other glass vessel, 
and then tested with the cyanide. If cyanide has been accidentally 
added in excess, a little more chloride of gold must be added to neutralise 
it. The precipitate must be allowed to settle, when the supernatant 
liquor is to be poured off, and the precipitate washed several times 
with distilled water. Lastly, a little distilled water is to be added to 
the precipitate, and a sufficient quantity of cyanide solution poured in 
to dissolve it, after which a little excess of cyanide solution must be 
added, and the solution then made up to one quart with distilled 
water. Before adding the final quantity of water, however, it is a 
good plan, when convenient to do so, to pour the concentrated solu- 
tion into an evaporating dish, and to evaporate it to dryness, which 
may be most conveniently done by means of a sand-bath, after which 
the resulting mass is to be dissolved in one quart of hot distilled 
water, and, should the solution work slowly in gilding, a little more 
cyanide must be added. The solution should be filtered before using, 
and must be worked hot, that is at about 130° Fahr. 

II. Take the same quantity of gt)ld, and form into chloride as 
before, and dissolve in half a pint of distilled water ; precipitate the 
gold with ammonia, being careful not to add this in excess. The pre- 
cipitate is to be washed as before, but must not be allowed to become 
dry^ since it will explode with the sHghtest friction when it is in that 
state. A strong solution of cyanide is next added until the precipi- 
tate is dissolved. The concentrated solution is now to be filtered, and 
finally, distilled water added to make one quart. Of course it will 
be understood that the quantity of solution given in this and other 
f ormulee merely represents the basis upon which larger quantities may 
be prepared. This solution must not be evaporated to dryness. 

III. BccqtiereVs Solution. — This is composed of — 

Chloride of gold .... i part 

Ferrocyanide of potassium 10 parts 

Water 100 „ 

The above salts are first to be dissolved in the water ; the liquid is 
then to be filtered ; 100 parts of a saturated solution of ferrocyanide 
of potassium are now to be added, and the mixture diluted with 
once or twice its volume of w^ater. **• In general, the tone of the 
gilding varies according as this solution is more or less diluted ; the 
colour is most beautiful when the liquid is most dilute, and most free 
from iron [from the ferrocyanide]. To make the surface appear 
bright, it is sufficient to wash the article in water acidulated with 
sulphuric acid, rubbing it gently with a piece of cloth." 



FRENCH GILDING flOLUTIONS. (77 

rV. Fizeau*8 Solutiwu. — (i.) i part of dt}' chloride of gold is 
dissolved in i6o parts of distilled water ; to this is added, gpraduallj, 
solution of a carbonated alkali in distilled water, nntil the liquid 
becomes cloudy. This solution may be used immediately. (2.) i 
gramme of chloride of gold and 4 grammes of hyposulphite of soda 
are dissolved in i litre of distilled water. 

y. Wood* 8 Solution, — 4 ounces (troy) of cyanide of potassium 
and I ounce of cyanide of gold are dissolved in i gallon of dis- 
tilled water, and the solution is used at a temperature of about 90*^ 
Fahr., with a current of at least two cells. 

VI. M. de BriantU Solution. — ^The preparation of this solution is 
thus described: ''Dissolve 34 grammes of gold in aqua regia, and 
evaporate the solution until it becomes neutral chloride of gold ; then 
dissolve the chloride in 4 kilogrammes of warm water, and add to it 
200 grammes of magnesia ; the gold is precipitated. Filter, and wash 
with pure water ; digest the precipitate in 40 parts of water mixed 
with 3 parts of nitric acid, to remove magnesia, then wash the 
remaining [resulting] oxide of gold, with water, until the wash-water 
exhibits no acid reaction with test-paper [litmus-paper]. Next 
dissolve 400 grammes of f errocyanide of potassium [yellow prussiate of 
potash] and 100 grammes of caustic potash in 4 litres of water, add 
the oxide of gold, and boil the solution about twenty minutes. When 
the gold is dissolved, there remains a small amount of iron precipitated 
which may be removed by filtration, and the liquid, of a fine gold 
colour, is ready for use ; it may be employed either hot or cold." 

VII. French Gilding Solutions. — ^The following solutions are recom- 
mended by Roseleur as those which he constantly adopted in practice 
— a sufficient recommendation of their usefulness. In the first of these 
both phosphate and bisulphite of soda are employed, with a small 
percentage of cyanide. The first formula is composed of — 

Phosphate of soda (crystallised) 
Bisulphite of soda . 
Cyanide of potassium (pure) . 
Gold (converted into chloride) 
Distilled or rain water 

The seoond formula consists of — 

Phosphate of soda . 
Bisulphite of soda . 
Cyanide of potassium (pure) . 

Gold 

Distilled water 

In making up either of the above baths, the phosphate of soda is 
first dissolved in 800 parts of hot water ; when thoroughly dissolved, 
the solution should be filtered, if not quite clear, and allowed to cool. 

N 



60 parts 


10 „ 


I part 


I » 


1,000 parts. 


50 parts 


I2i „ 


ipart 


I » 


i/xx> parts. 



^ 



178 ELKCTRO-DEPOSmON OF GOLD. 

The gold having been converted into solid chloride, is next to be dis- 
solved in 100 parts of water, and the bisulphite of soda and cyanide 
in the remaining 100 parts. The solution of gold is now to be poured 
slowly, with stirring, into the phosphate of soda solution, which 
acquires a greenish-yellow tint. The solution of bisulphite of soda 
and cyanide is next to be added, promptly, when the solution becomes 
colourless and is ready for use. If the solution of phosphate of soda 
is not allowed to become cold before the chloride of gold is added, a 
portion of this metal is apt to become reduced to the metallic state. 
Boseleur considers it of great importance to add the various solutions 
in the direct order specified. 

The first-named bath is recommended for the rapid gilding of 
articles made from silver, bronze, copper, and German silver, or other 
alloys of copper. The second bath is modified so as to be suitable for gild- 
ing steel, as also cast and wrought iron directly ; that is, without being 
previously coated with copper. The solutions are worked at a temper- 
ature of from 122° to 176° Fahr. In working the first bath, Boseleur 
says, " Small articles, such as brooches, bracelets, and jewellery -ware 
in gpencral, are kept in the right hand with the conducting wire, and 
plunged, and constantly agitated in the bath. The left hand holds 
the anode of platinum wire, which is immersed more or less in the 
liquor according to the surface of the articles to be gilt. Large pieces 
are suspended by one or more brass rods, and, as with the platinum 
anode, are moved about. The shade of the gold deposit is modified 
by dipping the platinum anode more or less in the liquor, the paler 
tints being obtained when a small surface is exposed, and the darker 
shades with a largfer surface. Gilders of small articles generally 
nearly exhaust tiieir baths, and as soon as they cease to give satisfac- 
tory results, make a new one, and keep the old bath for coloured gt)lds, 
or for beginning the gilding of articles, which are then scratch- 
brushed and finished in a fresh bath. Those who gfild large pieces 
maintain the strength of their baths by successive additions of 
chloride of gold, or, what is better, of equal parts of ammoniuret of 
gold and cyanide of potassium." Articles of copper or its alloys, 
after being properly cleaned, are sometimes passed through a very 
weak solution of nitrate of mercury before being immersed in the 
gilding bath. 

The above system of working without a gold anode is certainly 
economical for cheap jewellery, or such fancy articles as merely 
require the colour of gold upon their surface ; but it will be readily 
understood that solutions worked with a platinum anode would be 
useless for depositing a durable coating of gold upon any metallic 
surface, unless the addition of chloride of gold were constantly 
made. 



GILDING SOLUTIONS HADE BY THE BATTERY PROCESS. 1 79 

VIII. Gilding Sohdionn Made by the Buttery Proergg. — The HyRtom 
of forming gold aolutions by cW'trolyflis hafl mnoh to rec;ominoii(l it ; 
the procefis is simple in itself : it requiren but little manipulation, and 
in inexperienced hands is less liable to involve waste of gold than the 
ordinary chemical methods of preparing gilding solutions. A gold 
bath made by the battery process, moreover, if the cyanide be of good 
quality, is the purest form of solution obtainable. To prepare the 
solution, dissolve about I pound of good cyanide in i gallon of hot 
distilled water. When aU is dissolved, nearly fill a p^ectly clean 
and fiew porous cell with the cyanide solution, and stand it upright in 
the vessel containing the bulk of the solution, taking care that the 
liquid stands at the same height in each vessel. Next attach a clean 
block of carbon or strip of clean sheet copper to the negative polie of a < 
voltaic battery, and immerse this in the porous cell. A gold anode 
attached to the positive pole is next to be placed in the bath, and the 
voltaic action kept up until about i ounce of gold has been dis.sf)lved 
into the solution, which is easily determined by weighing the gold 
both before and after immersion. The solution should be maintained 
at a temperature of 130^ to 150° Fahr. while it is under the action 
of the current. 

Another method of preparing gold solutions by the battery process, 
is to attach a large plate of gold to the positive, and a tsimilar plate 
of gold or block of carbon to the negative electtrode, both being im- 
mersed in the hot cyanide solution as above, and a current from 2 
Daniell cells passed through the liquid. The negative electrode 
should be replaced by a clean cathode of sheet Grerman silver for a few 
moments occasionally, to ascertain whether the solution is rich 
enough in metal to yield a deposit, and when the solution is in a con- 
dition to g^d German silver promptly, with an anode surface of about 
the same extent, the bath may be considered ready for use. The 
proportion of gold, per gallon of solution, may be greatly varied, 
from } an ounce, or even less, to 2 ounces of gold per gallon of solution 
being employed, but larger quantities of cyanide must be used in 
proportion. While the gold is dissolving into the solution, the liquid 
should be occasionally stirred. The bath should be worked at from 
130° to 150° Fahr., the lower temperature being preferable. In 
making solutions by the battery process, the position of the anode 
should be shifted from time to time, otherwise it is liable to be cut 
through at the part nearest the surface of the solution (the tcaterline) 
where the electro -chemical action Ls strongest. A good way to 
prevent this is to punch a hole at each comer of the gold anode, and 
also a hole midway between each of the comer holes, through which 
the supporting hook may be Buccei<sively passed ; this arrangement 
will admit of eight shiftings of the anode. Another plan is to connect 



l8o ELBCTBO-DEPOSmON OF GOLD. 

a stont platinam wire or a bundle of fine wiree to the anode by meann 
of g^Id solder, and to immerse the whole of the anode in the cyanide 
solution ; this is a very good plan for dissolving the gold uniformly, 
since the platinam is not acted upon by the cyanide. Sometimes 
gold wires are used to suspend the anode, in which case the wire 
should be protected from the action of the cyanide by slipping a glass 
tube or piece of vulcanised india-rubber tubing over it. 

IX. 3e Huolz^t Solution. — lo parts of cyanide are dissolved in lOO 
parts of distilled water, and the solution then filtered ; i part of 
cyanide of gold, carefully prepared and well washed, and dried out of 
the influence of light, is now added to the filtered solution of cyanide. 
It is recommended that the solution be kept in a closed vessel at a 
temperature of 60° to yy"" Fahr. for two or three days, with frequent 
stirring, and away from the presence of light. 

X. Cold Eleetro-gilding Solutions, — ^The cold gilding bath is some- 
times used for very large objects, as clocks, chandeliers, &o., to avoid 
the necessity of heating g^reat volumes of liquid. As in the case of 
hot solutions, the proportions of gold and cyanide may be modified 
considerably. Any double cyanide of gold solution may be used cold, 
provided it be rich both in metal and its solvent^ cyanide of potassium, 
and a sufficient surface of anode immersed in the bath during electro- 
deposition. For most practical purposes of cold gilding, the following 
formulsB are reconmiended by Boseleur : — 

Fine gold 10 parts 

Cyanide of potassium of 70 per cent . . 30 „ 

Liquid ammonia • 50 » 

Distilled water 1,000 „ 

Thegfold is converted into chloride and crystallised, and is then dis- 
solved in a small quantity of water ; the liquid ammonia is now to 
be added, and the mixture stirred. The precipitate, of a yellowish 
brown colour, is aurate of ammonia^ ammoniuret of gold, or fulminating 
gold, and is a highly explosive substance, which must not on any 
account be allowed to become dry, since in that state it would detonate 
with the slighest friction, or an accidental blow from the glass stirrer. 
Allow the precipitate to subside, then pour off the supernatant liquor 
and wash the precipitate several times ; since the waehing waters will 
retain a little gold, these should be set aside in order that the metal 
may be recovered at a future time. The same rule should apply to 
all washing waters, either from gold or silver precipitates. The 
aurate of gold is next to be poured on a filter of bibulous paper, that 
is filtering paper specially sold for such purposes. The cyanide 
should, in the interim, have been dissolved in the remainder of the 
water. The cyanide solution is now to be added to the precipitate, 



CX>LD ELEGTBO-OILDING 80LUTI0N& x3l 

which it readily dissolyes, and this may be oonveniently done, if a 
large filter is used, by pouring it on to the wet precipitate while in 
the filter, a portion at a time, until the aurate of ammonia has disap- 
peared, and the whole of the cyanide solution has passed through 
the filter. This will be a safer plan than removing the precipitate 
from the filter ; or the filter may be suspended in the cyanide solution 
until the aurate is all dissolved. The solution is finally to be boiled 
for about an hour, to drive off excess of ammonia. 

After this solution has been worked for some time it is apt to 
become weaker in metal, in which case it must be strengthened by 
additions of aurate of ammonia. For this purpose, a concentrated 
solution of the gold salt in cyanide of potassium is kept always at 
hand, and small quantities added to the bath from time to time when 
necessary. It is preferable to employ good ordinary cyanide in 
making up the bath, ajad pure cyanide for the concentrated solution. 

2. This solution is composed of — 

Fine gold lo parts 

Pure cyanide of potassium . . 20 „ 

Or commercial cyanide . . . 30 to 40 parts 

Distilled water .... 1,000 parts. 

The gold is to be formed into chloride and crystallised, as before, 
and dissolved in about 200 parts of the water ; the cyanide is next to 
be dissolved in the remainder of the water, and, if necessary, filtered. 
The solutions are now to be mixed and boiled for a short time. When 
the solution becomes weakened by use, its strength is to be aug- 
mented by adding a strong solution of cyanide of gold, prepared by 
adding a solution made from i part of solid chloride dissolved in a 
littie water, and from I to i^ parts of pure cyanide of potassium, 
also dissolved in distilled water, the two solutions being tiien mixed 
together. 

3. This solution oonsLsts of — 

Ferrocyanide of potassium (yellow prussiate of potash) 20 parts 
Pure carbonate of potash . .... 30 „ 

Sal-ammoniac 3 „ 

Gold ... 15 „ 

Water i/xx> „ 

All the salts, excepting the chloride of g^old, are to be added to the 
water, and the mixture boiled, and afterwards filtered. The chloride 
of gold is next to be dissolved in a littie distilled water and added to 
the filtered liquor. Some persons prefer employing the aurate of 
ammonia in place of the chloride of gold, and sometimes small 



iSa ELECTRO-DEPOSITION OF GOLD. 

quantities of pnissio acid are added to the bath, to improve the bright- 
116.48 of the deposit ; but this acid makes the bath act more slowly. 

The deposit of g^ld from cold solutions varies greatly as to colour. 
When the bath is in its best working* condition, and a brisk current 
of electricity employed, the gold should be of a pure yellow colour ; 
sometimes, however, it is several shades lights, being of a pale 
yellow ; it sometimes happens that the gold will be deposited of an 
earthy grey colour, in which case the articles require to be cautiously 
scratch-brushed, and afterwards coloured by the or-moulu process to 
be described hereafter. The proportion of cyanide in these baths 
should be about twice that of the chloride of gold ; but since the 
cyanide is of variable quality, it may often be necessary to employ an 
excess, which is determined by the colour of the deposit ; if the gold 
is in excess the deposit may be of a blackish or dark red colour ; or if, 
on the contrary, cyanide preponderates, the operation is slow and 
the gold of a dull grey colour, and not unfrequently, when the bath 
is in this condition, the gold becomes re -dissolved from the work in 
solution, either entirely or in patches. 

When the bath is not in good working order, the gold anode must 
be withdrawn from the solution, otherwise it will become dissolved by 
the cyanide. It is a "remarkable phenomenon," says Roseleur, 
" that solutions of cyanides, even without the action of the electric 
current, rapidly dissolve in the cold, or at a moderate temperature, all 
the metals, except platinum, and that at the boiling point they have 
scarcely any action upon the metals." 

Obftervationa on Gilding in Cold Baths. — When a pure yellow colour 
is desired, a newly -prepared double cyanide of gold solution, in 
which a moderate excess only of cyanide is present, and containing 
from I to 2 ounces of gold per gallon, will yield excellent results with 
the current from a single WoUaston or Daniell battery; but suffi- 
cient anode must be exposed in the nolution to admit of the deposit 
taking place almost immediately after the article is immersed in the 
bath. The anode may then be partially raised out of the solution, 
and the deposition allowed to take place without further interference 
than an occasional shifting of the object to coat the spot where the 
slinging wire touches. After the article has been in the bath a 
minute or so, the operator may assure himself that deposition is pro- 
gressing satisfactorily by dipping a piece of clean silvered copper wire 
in the bath and allowing it to touch the object being gilt, when, if 
the end of the wire becomes coated with gold, he may rest assured 
that dex>o.sition is proceeding favourably. . Care must be taken, how- 
ever, that the deposit is not taking place too rapidily, for it is abso- 
lutely ueces^sary that the action should be gradual, otherwise the gold 
may strip off under* the operation of the scratch-brush. If any 



OB8SBVATION8 ON GILDING IN COLD BATHS. 183 

portioiis of the work appear patchy or spotted, the pieces must be 
removed from the bath, rinsed, and well scratch-brufihed. As in hot 
gilding, the plater will find the soratch-brosh his best friend when 
the work presents an irreg^ular appearance. 

It is not advisable to employ a current of high intensity in cold 
grilling; the Wollaston or Daniell batteries, therefore, are most 
suitable, and when a series of cells are required to g^d large surfaccn 
or a considerable number of objects, the poles of the batteries should 
be connected in parallel, that is all the positive electrodes should be 
connected to the anodes, and all the neg^ative electrodes put in com- 
munication with the conducting-rod supporting the work in the bath. 
After deposition has taken place to some extent, an extra cell may hv 
connected, followed by another, if necessary, and so on ; but while 
only a thin coating of gold is upon the work, the strengih of the 
current shotdd be kept low ; deposition takes place more slowly upon 
gold than upon copper or its alloys, therefore an increase of batter}' 
power becomes a necessity after a certain thickness of gold has been de- 
posited. If the current be too weak, on the other hand, the deposit is 
apt to occur only at the prominent points of the article, and upon thoso 
portions which are nearest the anode. It Hometimes happens, with 
newly made baths, that when the articles are shifted to expose frcish 
surfaces to the anode, the gx)ld already deposited upon the work 
becomes dissolved off ; when such is the case, it generally indicates 
that there is too great an excess of cyanide in the solution, although 
the Kame result may occur if tliere be too little gold or the current too 
feeble. 

When the gold deposited in a cold bath is of an inferior colour, the 
article may \xi dipped in a weak solution of nitrate of mcrciuy until it 
is entirely white ; it is then to be heatwl to cxi)i'l the mercury, and 
afterwards scratch -bruHhed. Or the articlo umy be bruKh«Mi over with 
the "green colour," de»cribcd in anoUier chajitcr, and treated in the 
same way as bad-coloured gilding from hot solutions. 

XI. Fenocyanide Gilditiy i^lution. — To avoid the use of large (quan- 
tities of cyanide of potassium in gilding solutions, the following 
process has been proposed : In a vessel, capable of holding 4 litres, 
are dissolved in distilled water 300 gimmes of ferrocyanidc of 
potassium, and 50 grammes of sal-ammoniac; icx) grammes of gold, 
dissolved in aqua regia and evaporated to expel the acid as usual, 
are dissolved in i litre of distilled water. Of this solution, 200 
cubic centimetres are added, little by little, to the ferrocyanide solu- 
tion, when oxide of iron (from the ferrocyanide) is precipitated. 
The liquid is allowed to cool, and is then filtered and made up to 5 
litres, when the bath is ready for use. Since it is not a good con- 
ductor, however, and deposits oxide of iron upon the anode, a small 



184 XLEOTBO-DEPOSinON OF GOLD. 

quantity- of cyanide is added, but not suffioient to evolve hydrocyanio 
acid on boiling. The bath should be worked at from loo"* to 150" 
Fahr. When the bath ceases to yield a good deposit, 200 c.c. of the 
gt>ld solution must be added g^radually, as before ; if it is desired to 
increase this proportion of gold, one-tenth of the quantity of the 
other salts must also be added to the bath. 

*KII. WatVs Gilding Solution. — ^A gilding solution which the author 
has usccl very extensively, and which he first adopted about the year 
1838, is formed as follows : i^ pennyweight of fine gold is converted 
into chloride, as before described, and afterwards dissolved in about 
\ pint of distilled water. 8ulphide of ammonium is now added 
gradually with stirring, until all the gold is thrown down in the form 
of a brown precipitate. After repose the supernatant liquor is poured 
off, and the precipitate washed several times with distilled water ; it 
is then dissolved in a strong solution of cyanide of potassium, a 
moderate excess being added as free cyanide, and the solution thus 
formed is diluted with distilled water to make up one quart. Before 
using this solution for g^ding it should be maintained at the boiling 
point for about half an hour, and the loss by evaporation made up 
by addition of distilled water. This bath yields a fine gold colour, 
and if strengthened from time to time by a moderate addition of 
cyanide, will continue to work well for a very considerable period ; it 
should be worked at about 130° Fahr. The above solution gives very 
good results with a Daniell battery, and the articles to be g^t do not 
require quickingy as the deposit is very adherent. 

XIII. RecordU Gilding Bath, — ^This solution, for which a patent was 
obtained in 1884, is formed by combining nickel and gold solutions, 
by which, the patentee avers, a considerable saving of gold is effected. 
To make this solution, he dissolves 5 ounces of nickel salts in 'about 
2 gallons of water, to which 12 ounces of cyanide of potassium is 
added, *' so that the nickel salts may be taken up quite clear." The 
solution is then boiled until the ammonia contained in the nickel salts 
is entirely evaporated. This solution is then added to the ordinary 
gold solution containing i ounce of gold. The proportions given arc 
preferred, but may be varied at will. 



CHAPTER XI. 

ELECTRO-DEPOBITION OF GOLD {continued). 

Geaeral ManipulatioQB of Electro-gilding. — Preparation of the Work. — Dead 
Gilding. — Causes which affect the Colour of the Deposit. — Gilding 
Gold Articles. — Gilding Insides of Vessels. — Gilding Silver Filigree 
Work. — Gilding Army Accoutrement Work. — Gilding German Silver.— 
Gilding Steel. — Gilding Watch Movements. 

OMMral Manlpnlitiona of Btoetro-CMldins. — In small gilding 
operations, the apparatus and arrangements are of an exceedingly 
simple character, and need not involve more than a trifling outlay. 
A i2-inoh DanieU cell, or a small battery (say a half -gallon cell), con- 
structed as follows, will answer well for gilding such small work as 
Albert chains, watch oases, pins, ringfs, and other work of small 
dimensions. This battery consists of a stone jar, 
within which is placed a cylinder of thin sheet- 
copper, having a binding screw attached. Within 
this cylinder is plaoed a porous ceQ, furnished with 
a plate or bar of amalgamated zinc, to the upper end 
of which a binding screw is connected. A dilute ^' ' 

solution of sulphuric acid is poured into the porous cell, and a 
nearly saturated solution of sulphate of copper, moderately acidified 
with sulphuric acid, is poured into the outer cell. This simple battery 
costs very little, is very constant in action, and may readily be 
constructed by the amateur or small operator. The gfilding bath 
may consist of one quart of solution, prepared from any of the for- 
mulae given; a square piece of rolled gold, about 2 by 2 inches, 
weighing about five i>ennyweights, or even less, will serve for the 
anode ; and an enamelled iron saucepan may be used to contain the 
solution. Since gilding baths reqtiire to be used hot (about 130' 
Fahr.), except for special purposes, the solution may be heated by 
means of a small 4-bumer oil lamp, such as is shown in Fig. 74, 
the gilding vessel being supported upon an iron tripod or ordinary 
meat stand. 

With this simple arrangement, it is quite possible to gild such 
articles as we have named, besides smaller articles, such as brooches, 
lockets, and suarf-pins ; and providfnl the gold anode be replaced, as 




1 86 ELECTBO-DEPOSITION OF GOLD. 

it becomes ''worn away*' in use, and the solution kept up to its 
normal height by additions of distilled water to make up for loss by 
evaporation, the same bath will be capable of gilding a g^ood amoimt 
of small work. The bath will, however, require small additions of 
cyanide every now and then, that is when it shows signs of workin^- 
slowly , or yields a deposit of an indi£Ferent c jlour ; the battery, also, will 
need proper attention by renewal of the dilute acid occasionally. In 
working on the small scale referred to, in the absence of a proper scratch - 
brush lathe, the hand " scratch-brush," Fig. 76, may be resorted to : 
this consists simply of a single scratch-brush, cut open at one end, and 
spread out before using, by well brushing it against some hard metal 
substance ; to mollify the extreme harshness of the newly cut brass 
wire, of which the brush is composed, it may advantageously be rubbed 
to and fro upon a hard flagstone, after which it should be rinsed before 
using. To apply the hand scratch-brush, prepare a little warm soap 
and water, into which the brush must be dipped frequently while being 
used. In brushing Albert chains or similar work, the swivel may be 
hooked on to a brass pin, driven into the comer of a bench or table, 
while the other end of the chain is held in the hand ; while thus 
stretched out, the moistened brush is dipped in the suds, and lightly 
passed to and fro from end to end, and the position of the article must 
bo reversed to do the opposite side ; to brush those parts of the links 
which cannot be reached while the chain is outstretched, the chain is 
held in the hand, and one part at a time passed over the firnt finger, by 
which means the uubrightened parts of the links may be readily 
scratch -brushed. It is important, in scratch-brushing, to keep the 
brush constantly and freely wetted as above. 

Gilding on a somewhat larger scale— say with one or two gallons 
of gold solution — may be pursued without any very jj^rcat outlay, and 
yet enable the gilder to do a considerable amount of wcirk of various 
kinds and dimensions in the coiirse of an ordinary working day. The 
arrangement we would suggest may be thu** briefly explained : for 
the battery, a one-gallon Bunsen, or Smee, or an 1 8 -inch Daniell 
cell ; for the anode, two or more ounces of fine gold rolled to about 
6 by 3 inches, to which a stout piece of platinum wire, about 4 inches 
in length, should be attached by means of gold solder. A small 
binding screw may be employed to connect the platiuum wire with 
the positive electrode of the battery. The object of using platinum 
wire is to enable the whole of the anode to be immersed in the solution 
when a large surface is necessary, and which could not be properly 
done if copper wire were used, since this metal (unlike platinum, 
which is not affected by the solution) would become dissolved by the 
bath, and affect the colour of the deposit. A simple method of heat- 
ing the gilding solution and keeping it hot while in use will be 



ELEOTBO-GILDING. 



187 




Fig. 75. 



in the aooompanying engraving, Fig. 75. The gilding bath rests 
upon a short-legged iron tripod, beneatii which is a perforated gas 
burner, supplied with gas by means of flexible india-rubber tubing 
connected to an ordinary 
g^-bumer. Perforated 
burners are readily pro- 
curable, and are of trifling 
cost. For brightening 
small articles the hand 
scratch-brush referred to 
(Fig. 76) may be used, 
but, for the convenience 
of handling, it should be 
tied to a stick, to prevent it from bending in the hand. The brush 
is to be dipped in soap-suds or stale beer frequently while being ap- 
plied to the work. 

In g^ding upon the above moderate scale, however, the lathe 
soratoh-bruah, described further on, will be as necessary as in still 
larger operations : an ordinary foot lathe, such as is used in silver 
plating (which see), is the nuushine generally used for this 
purpose, and is of very simple construction. Such lathes, or 
their chief parts, may often be procured second hand for a 
very moderate sum. As in scratch -brushing electro-silvered 
or plated work, stale beer is employed to keep the brushes 
constantly wet while the lathe is being used, and the work 
in pressed very lightly against the revolving brushes. It is 
important, however, when the scratch-brushes are new, 
that they should have some hard metallic surface pressed 
against them while in brisk motion for a few minutes, to 
spread them well out or make them brushy , and to reduce 
the extreme harshness of the newly-cut brass wire ; if this pj ^ 
precaution be not followed, the gold, if the coating be 
thin, may become partially removed from the gilt article, rendering 
its surface irregular and of an indifferent colour, necessitating regild- 
ing and scratch-brushing. 

Fr^patatton of the Wodc — In electro-gilding watch chains of 
various kinds, brooches, lockets, scarf-pins, and other small articles 
of jewellery, it is generally sufficient to well scratch-brush and rinse 
them, after which they are at once put into the bath. A preparatory 
dip in a hot potash bath, however, may be resorted to. After scratch- 
brushing, a short length of copper <* slinging^* wire is attached to 
the article, and the free end is connected to the negative electrode of 
the battery by simply coiling it around the stouter wire several timoH : 
the ends of both wires, however, should previously be cleaned by 



1 88 BLEOTBO-DKPOSrnON OF GOLD. 

meanB of a pieoe of emefy doth. When ihe articles are fint clipped 
into the solution, thej should be gently moved about, so that the 
deposit may be rogpilar. Chains should be shifted from their position 
oocaaionally, so that those portions which are in contact with each 
other may become gilt ; this may generally be done by giving tlie 
chain a brisk shake from time to time, and also by slix^ping the chain 
through the loop of the slinging wire. If brooches and other similar 
articles are slung by a loose loop of wire, gentie shaking is all that is 
necessary to shift tlieir position on the sling^g wire. 

Some operators, when gilding metal chains or other work manufac- 
tured from copper or its alloys — ^brass, gilding metal, and German 
silver — ^prefer to quick them after steeping in the potash bath and 
scratch-brushing. In this case it will be necessary to have a qidcking 
bath or ** meroury dip " always at hand. The mercury dip consists 
of a very dilute solution of nitrate or cyanide of meroury, and after 
the articles have been whitened in this bath, they must be well rinsed 
in clean water before being immersed in the gilding bath. The object 
of meroury dipping is to ensuro a perfect adhesion of the gold deposit. 
The author has never, either in electro-gilding or silvering, found it 
necessary to apply the quioking process, but the solutions both of 
gold and silver wero not prepared in the same way as those ordinarily 
adopted by the trade. The solutions which the author worked for a 
great number years without the aid of the mercurial coating aro men- 
tioned in tiie chapters describing the preparation of gilding and 
silvering baths. 

D«ad OMldinff. — ^There aro several methods of preparing the work so 
that the deposit instead of being more or less bright when removed from 
the gilding-bath,may prertcnt a dead or /ro«/^ appearance, which is not 
only exceedingly beautiful in the rich dulness of its lustre, but is 
absolutely necessary for certain classes of work, portions of which are 
relieved by burnishing. To obtain a deposit of a somewhat dead 
lustre, copper and brass articles are dipped for a moment in a mixture 
of equal parts of oil of vitrei and nitric add, to which is added a 
small quantity of common salt. The articles are slung on a stout wire, 
coiled into a loop, and dipped in the nitro-sulphuric acid ** dip *' for 
an instant, and immediately rinsed in clean water, kept in a vessel 
close to the dipping acid : if not suificientiy acted upon during the 
first dip, they must be again steeped for a moment, then rinsed in 
several successive waters, and at once put into the gilding bath. 
There shoidd be as littie delay a possible in transferring the articles 
to the gold bath, after dipping and rinsing, since copper and its alloys, 
after being cleaned by the acid and rinsed, are very susceptible of 
oxidation, even a very few moinpnt« being sufficient to tarnish them. 
If the meroury dip is employed, the work must be dipped in the 



CAUSES WHICH AFFSCT THE COLOUR OF THE DEPOSIT. 189 

quicking bath immediately after they have been rinsed from the acid 
dip. 

Hie surfaoe of articles may be rendered BtQl more deady or frosted, 
by slightly brushing them over with finely powdered pnmioe, of, still 
better, ordinary bath brick reduced to a powder. By this means the 
extreme point of dulness, or deadness, may be reached with very little 
trouble. Work which requires to be burnished after gilding should 
first be steeped in the potash bath, and after rinsing be well scratch- 
brushed, or scoured with silver sand, soap, and water, when, after 
again rinsing in hot water, it is ready for the bath. In scouring the 
work with sand and soap, it is necessary to use warm water freely ; 
the soap may be conveniently applied by fixing a largfe piece of this 
material — say \ lb. of yellow soap — ^to the scouiing-board by means 
of four upright wooden pegs or skewers, forming a square about 
H inches each way, within which the soap may be secured firmly, 
and will retain its position until nearly used up. By this simple plan 
the soap, being a fixture, may be rubbed with the scouring-brush, as 
occasion may require, without occupying a second hand for the 
purpose. 

Oan— wliitib AfllMt Ohm Oeloar off tlM ]>6posit. — In the opera- 
tion of gilding, the colour of the deposit may be infiuenced almost 
momentarily in several ways. Assuming that the current of elec- 
tricity is neither too strong nor too weak, and the bath in perfect 
order, if too small a surface of anode is immersed in the bath, the 
gold deposit wiU be of a pale yellow colour. Or, on the other hand, 
if too large a surface of anode is exposed in tolutiotif the deposit 
may be of a dark brown or <<foxy*' colour, whereas the mean be- 
tween these two extremes wiU cause the deposit to assume the rich 
orange-yellow colour of fine or pure gold. Again, the colour of 
the deposit is greatly affected by the motion of articles while in 
the bath ; for example, if the g^ding be of a dark colour, by briskly 
moving the articles about in the bath, they will quickly assume the 
proper colour. The temperature of the solution also affects the colour 
of the deposit, the tone being deeper as the solution becomes hotter, 
and vice verad. The colour of the gilding is likewise much affected 
by the nature of the current employed. A weak current from a 
Wollaston or Daniell battery may cause the deposit to be of a paler 
colour than is desired, whereas a Smee, Grove, or Bunsen (but more 
especially the latter) wiU produce a deposit of a far richer tone. The 
presence of other metals in the solution, but copper and silver more 
particularly, will alter the colour of the deposit, and therefore it is 
of the gfreatest importance to keep these metals out of the ordinary 
grilling solution by careful means. When gilding in various colours 
IB needed, recoTirse must be had to the solutions described elsewhere. 



190 KLKCTRO-DErOSinON OP GOLD. 

but on no account ishould the gildllig bath used for ordinary work be 
allowed to become impregnated with even small quantities of any 
other metal. When we state that trifling causes will sometimes inter- 
fere with the natural beauty of the pure gold deposit, the importance 
of preserving the baths from the introduction of foreign matters will 
be at once apparent. Another thing that affects the colour of the 
gilding is the accumulation of organic matter^ that is, vegetable or 
animal matter, which is introduced into the bath by the articles im- 
mersed in it ; thus, greasy matter from polished work, and beer from 
the scratch -brush, will sometimes lodge in the interstices of hollow 
work, and escape into the bath even after the articles have been 
rinsed ; each in their turn convey organic matter to the gold solution, 
by which it acquires a darkened colour ; indeed, we have known solu- 
tions acquire quite a brown colour from these causes. In our expe- 
rience, however, the presence of a small amount of such foreign 
matter, in moderation, has often proved of advantage, especially in 
the gilding of insides of vessels, when a rich and deep -toned gilding 
is required : a solution in this condition we should prefer, for insides 
of cream ewers, sug^-bowls, and goblets, to a newly -prepared gold 
solution ; indeed, when a bath works a little /oxy, it is, to our mind, 
in the best condition for these piurposes, since the former is apt to yield 
a deposit which is too yellow for such surfaces. There is an extreme, 
however, whidi must be avoided, that is when the bath yields a ^vum- 
yeUow deposit, which is very unsightly, though not uncommonly to be 
seen in our shop windows. 

When the gilding upon chains or articles of that class is of a deep 
brownish-yellow colour when removed from the bath, it will, when 
scratch-brushed, exhibit a fine gold appearance, specially suited to 
this class of work, and more like jewellers' ** wet colour work " than 
electro-gilding, which will render it more acceptable to those who 
are judges of gold colour. Indeed, when the electro -gilding process 
was first introduced, it was a general complaint amongst shopkeepers 
that electro -g^ding was too yellow, and that electro-gilt work could 
easily be distinguished from coloured gold in consequence, which was 
admitted to be a serious defect, since a person wearing a g^t article 
would naturally wish it to be assumed by others to be of gold. In 
gilding such articles, therefore, the aim of the gilder should be to 
imitate as closely as possible the colour of g^ld jewellery, whether it 
be dry or wet coloured work. In the latter there is a peculiar depth 
and softness of tone which is exceedingly pleasing; in dry coloured 
work a rich dead surface is produced which it is not so difficult to 
imitate in electro -gilding. The processes of *• colouring" articles of 
gfold win be given in another chapter, since a knowledge of these 
processes is not only useful but often necessary to an electro-gilder, 



OrLDINO TNBIDEB 

in whoHC hands such work niBy Hometiiaes be placed for restoratiiin 
or reoolouriiip:. 

Olldlns Oold JUUolss. — Although "pninting tlie IU7" would 
not be a very profitable or aucccusful operation, artidea nudo from 
inferior giili alloys are frequently Bent to the elootro- gilder to 
be " coloured," that is, to receive a slight film of pure gold, to 
make them look like gold of a miperior quality, like coloured gold, 
in tact. Although such an imposition is a positive fraud upon the 
purchaser, the electro -gilder has little choice in the matter; if hia 
natural scruples irould tempt him to refuse such unfair work, aa it 
may be called, he knows full wdl that othem will readily do the work 
and " ask no questions ; " he must therefore undertake it or lose a 
cufltomer — perhaps an important one. Albert chains, rings, pins, 
bloocheH, and a host of other articles manufiictared from gold aUoys 
of very low standard, are frequently " coloured" by electro -deposition, 
simply because the process of colonring by means of the " colouring 
■alts " would rat them, if not diHsolve them entirely. 

OUdlns IiiaM** Of V— — !■ — SUver or electro-plated cream ewers, 
sugar-basins, mugs, ir,, are electro-gilt inside in the following way; 
The inaide of the vessel is first well scrateh- brushed, for which pur- 
pose a epedal scratch -brush, called an end-bitah, is used. Or this 
iutfaoe may be scoured with soap and 
water with a piece of stout flannel ; tho 
vessel, after well rinMng, is then placed 
apon a level table or bench ; a gold 
■node, turned up in the form of a 
hollow cylinder, is now to be connected 
to the pomtivG electrode of a battery, and 
lowered into the vessel, and supported in p| 

this position, care being taken that it 

doee not tonch the vessel at any point. The negative electrode is 
to be placed in contact witli the vessel (Fig. 77), and hot gold solu- 
tion then carefully poured in, up to its extreme inner edge, below 
the mount, if it have one. A few moments after pouring in the 
gold solution, the anode should be gently moved to and fro, without 
coming in contact with the vessel itself, so as to render the depoat 
more unifonn ; it may then be allowed to remain without interruption 
for a minute or so, when the gentle movement of the anode may he 
renewed for a few moments, these altemationB of motion and repose 
being kept up for about live or six minutes — or periiaps a little longer 
— by which time a sufficiently stout ooatiog is generally obtained. 
Moving the anode occasionally has the effect of rendering the deposit 
more regular, while it aim exposes fresh surfaces of the solu- 
tiiai to the metal surfaoee under treAtment ; great care, how- 



192 ELECTRO-DEPOSITION OP GOLD. 

ever, is neoeesary to avoid driving the solution over the orna- 
mental mount on the rim of the vessel. The lipt of cream ewers, 
which the gold solution cannot reach when the vessel is filled with 
solntion, are gilt by condooting the solution to such parts as follows : 
A small gold anode, with a short pieoe of copper wire attached, 
is enclosed in a piece of rag or chamois leather ; the end of this wire 
is then connected to the positive electrode (the article itself being in 
direct contact with the negfative), and the pad, or "doctor/' as it is 
sometimes called, is dipped in the gold solution and applied to the part 
to be gilt ; in this way, by repeatedly dipping the pad in the solution 
and conducting it over the surface, this part in a short time becomes 
sufficiently gilt ; since the lip of a cream ewer, however, is the most 
important part of the gilt surface, the application of the pad should be 
continued until a proper coating is obtained, and care must be taken 
that the point of junction between the two deposits of gold is not 
viMble when the gilding is complete. We should prefer to gild the 
lip of such vessels first, and after well scratch -brushing, or scour- 
ing the interior, and especially the line where the two gildings will 
meet, then to gild the interior of the body of the vessel, and finally to 
scratch-brush the whole surface. In gilding the insides of vessels, it 
is important that the outsides and mounts, or mouldings, should be 
perfectly dry, otherwise the gold solution may, by capillary attraction, 
pass beyond its proper boundary and gold become deposited where 
it is not required, thus entailing the trouble and annoyance of re- 
moving it. 

OUdlns BUver niigrve D^ork. — ^A dead surface of silver is very 
apt to receive the gold deposit ununiformly, and this is specially so in 
the case of silver filigree work, the interstices of which cannot fully 
be reached by the scratch -brush ; the surfaces brightened by the 
scratch-brush readily receive the deposit, while those portions of the 
article which escape the action of the wire brush will sometimes fail to 
'* take " the gold. When this is found to be the case, a large surface 
of anode should be immersed in the bath, and the article briskly moved 
about until the whole surface is coated, when the anode may be par- 
tially withdrawn, and a sufficient surface only exposed in the bath to 
complete the article as usual. In gilding work of this description it is 
necessary that a fair amount of free cyanide should be in the bath, but 
the excess must not be too great, or the deposit will he foxy — a colour 
which must be strenuously avoided, since the brown tint will be visible 
more or less upon those interstices (especially the soldered parts) 
which the scratch-brush cannot reach. As a rule, filigree work 
should not bo risked in an old gold solution in which orgfanic matter or 
other impurities may be present. It is a good plan, after giving the 
article a quick coating in the way indicated, to rinse and ** scratch " it 



OILDING ARMY ACCOUTREMENT WORK. ig$ 

aguin, and then to re-immerse it in the bath. A solution for gilding 
filigree work fihould also be tolerably rich in gold — about 5 penny- 
weights to the quart of solution being a good proportion, though some 
gilders use a still larger proportion of metal. In gilding filigree work 
a rather intense current is necessary ; a Bunsen battery, therefore, 
should be employed, or two Baniell cells arranged for intensity. 

OildlBcr Army Aecontrvmant D^ork. — In the early days of 
electro- g^ding, great difficulty was experienced by eleotro-g^ders in 
imparting to sword-mounts, the threaded ornamentation of scabbards, 
and other army accoutrements the rich dead lustre, as the French term 
it, which the mercury g^ders produced with so much perfection, and 
for a long period electro-gilders, in their anxiety to obtain contracts 
for gilding this class of work, made many unsuccessful attempts and 
suffered much disappointment from the repeated rejection of their 
work by the goyemment authorities. At the period referred to, there 
was a great desire, if possible, to render the pernicious art of mercury 
grilding unnecessary, since it was too well known that those engaged 
in the art suffered seyerely from the effects of mercurial poisoning, by 
which their existence was rendered a misery to them, and their lives 
abbreviated to a remarkable degree. It may be stated, however, that 
the operations of g^ding with an amalgam of gold and mercury were 
frequentiy conducted with little or no regard to the dangerous nature 
of the fluid metal which the workpeople were constantiy handling, and 
the volatilised fumes of which they were as constantiy inhaling. It 
was a happy epoch in the gilding art when deposition of gold by elec- 
tricity rendered so baneful a process, incautioudy practised, compara- 
tively unnecessary. We say comparatively, because amalgam or 
mercury gfOding is still adopted, though with a littie better regard to 
the health of the workmen, for certain classes of work, for which, even 
up to the present period, electro-gilding is not recog^nised as a perfect 
substitute. 

To grild army accoutrement work, so as to resemble, as closely as 
possible, mercury gilding, the colour and general appearance of the 
matted or dead parts must be imitated very closely indeed. There are 
no articles of gilt work that look more beautiful by contrast than 
those in which dead surfaces are relieved by the raised parts and 
surrounding edg^s being brightened by burnishing, and this effect is 
charmingly illustrated in the mountings of the regulation sword of the 
British officer. Indeed this class of work, when properly finished, 
may be considered the perfection of beauty in gilding. 

To give the necessary matted surface to the chased portions of sword 

mounts, and work of a similar description, these parts should be 

brushed over with finely-powdered pumice, or bath-brick reduced to a 

powder and sifted, the latter subetanoe answers the purpose very 

o 



194 EliEOTBO-DS POSITION OF OOU). 

irelL The application of either of these materials should be oonfined, 
as far as is practicable, to the chased parts of the article, so as to avoid 
rendering the surfaces to be afterwards burnished rough by the 
action of the pumice powder. The plain surfaces of the article may 
then be scoured with sQver-sand, soap and water, or scratch- 
brushed ; but great care must be taken not to allow the scratch-brush 
to touch the surfaces that are to be left dead. Sometimes it is the 
practice to add a little aurate of ammonia to the gilding solution to 
produce a dead lustre in gilt work. When it is preferred to adopt 
the quieking process, in gilding this class of work, the articles, after 
being quioked in the usual way, are placed in the bath until they have 
nearly reoeiTed a sufficient deposit, when they are removed, rinsed, 
and the chased parts qidokly brushed with pumice, as before, after 
which they are returned to the bath for a short time, or until the 
proper colour and matted appearance are imparted to the work. 

aUdlDS (Kmiaii 81lT«r. — ^This alloy of copper, as also brass, will 
receive a deposit of gfold in strong and warm cyanide solutions of gold 
without the aid of the battery; this being the case, in order to 
prevent the deposit from taking place too rapidly, when electro- 
g^ding articles made from these alloys, the temperature of the 
solution should be kept rather low — that is not beyond 120® Fahr. — 
and only sufficient surface of anode immersed in the solution to enable 
the article to become gilt with moderate speed when^r«^ placed in the 
bath. It is also advisable that the gold solution should be weaker, 
both in gold and cyanide, than solutions which are used for g^ding 
silver or copper work. If, however, quieking be adopted, these pre- 
cautions are not so necessary, since the film of mercury checks the 
rapidity of the g^ding. Either method may be adopted according to 
the fancy of the gilder ; but for our own part, we would not suffer a 
partide of mercury to enter the gilding-room (except upon the amal- 
gamated plates of a battery) under any circumstances. 

CHldlBfir 8t««l. — The rapidity with which this metal receives a 
deposit of gold, even with a very weak battery current, in ordinary 
cyanide solutions, renders it imperative that a separate solution should 
be prepared and kept specially for steel articles. We have obtained 
excellent results by employing a bath composed of 

Ordioaiy doable cyanide of gold solution . . i part. 
Water 4 to 6 parts. 

To this weakened solution a small quantity of cyanide of potassium 
may be added, and the current employed should be of low tension — a 
WoUaston or Daniell battery being preferable. The temperature of 
the bath should be warm, but not hot. The surface of anode in 
solution must be just so much as will enable the gold to deposit soon 



GILDING 8TBXL. X95 

after the artiole is placed in the bath, but not immediately after its 
immersion. In other words, if the gold is allowed iojump on, it will 
most assuredly as quickly jump off when the scratch-brush is applied. 

In preparing steel articles for g^ding, the author has found that by 
scratch-brushing the work with Tineg^, or yery dilute hydrochloric 
acid, instead of sour beer, a Tery fine coating of copper (deriyed from 
the brass wire of the brushes) has been imparted to the articles, to 
which the gold deposit, from a weak bath, adhered with great 
firmness. 

A very successful method of gilding steel is to first copper or brass 
the articles in the alkaline solutions of these metals, as recommended 
for silvering steel and iron.* The brass or copper solutions should be 
used warm, and be in good working order, so as to yield bright 
deposits of good colour. Before electro-brassing the articles, howeyer, 
they must be thoroughly cleansed by scouring with silver-sand, soap 
and water, or scratch-brushed. Bright steel articles which are not 
required to have a durable coating of gold, but merely a slight film or 
<< colouring'* of the precious metal, generally need no preparation 
whateyer, but may receiye a momentary dip iu the g^ilding bath, then 
rinsed in hot water, and at once placed in hot boxwood sawdust. In 
doing this cheap class of work, howeyer, it is better to use a copper 
or platinum anode in place of the gold anode, and to make small 
additions of chloride of gold when the solution shows signs of 
becoming exhausted. It must be remembered, however, that the 
very dilute gold solution we have recommended for gilding steel con- 
tains in reidity but yety littie gold, therefore, as it becomes further 
exhausted by working without a gold anode, additions of the chloride, 
in very small quantities, will require to be made so soon as the bath 
exhibits inactiviiby. 

For gilding polished steel, a nearly neutral solution of chloride of 
gold is mixed with sulphuric ether, and well shaken ; the ether will 
take up the gold, and the ethereal solution float above the denser 
acid. If the ethereal solution be applied by means of a camel-hair 
brush to brightly-polished steel or iron, the ether evaporates, and 
gold, which adheres more or less firmly, becomes reduced to the 
metallic state on the steel, and may be either polished or burnished. 

In gilding upon an extensive scale, where laige objects, such as 
time-pieces, chalices, patens, and other work of large dimensions, have 
to be gilt, the depositing tanks are generally enamelled iron jacketed 
pans, heated by steam. These vesseLs are placed in rows near the 
wall of the gilding-room, in a good light, and suitable iron piping 
oQuveys the steam to the various tanks, each of which is provided with 
a suitable stoi)cock to admit or shut off the steam as required ; an exit 
pipe at the bottom of each '* jacket " allows the water from the oon- 

* See Chaps. XVI., XXIV., and XXV. 



196 ELEOTBO-DEPOSITION OF GOLD. 

densed steam to escape into a drain beneath. Each of these tanks is 
provided with the usual conducting rods, and the ouirenty which is 
sometimes deriyed from a magneto or dynamo machine in large estab- 
lishments, is conveyed by suitable leading wires or rods, attached to 
the wall at a short distance from the series of depositing vessels. In 
gilding large quantities of small articles, as steel pens, for example, a 
oonsiderable number of gilding tanks, of an oblong form, are plaoed 
in a row, at a moderate distance apart, and the pens or other small 
objects are introduced into these as the gilders receive the work pre- 
pared for them. 

aildlns Watcb MOTWBMita— Oonttnental MsiUiod. — The re- 
markable beauty of the Swiss watch movements has always been the 
finibject of much admiration, and for a long period this pleasing indus- 
try was solely confined to Switzerland ; France, however, eventually 
got possession of the method, and the art has been extensively 
practised in that country, but more especially at Besan9on and Mores, 
in Jura, and in Paris. M. Pinaire, a gilder at Besan^on, g^erously 
communicated the process to the late M. Boseleur, to whom we ate 
indebted for the process. 

Pinaire*8 Method of Gilding Watch Movementt. — In gilding watch 
parts, and other small articles for watchmakers, gold is seldom applied 
directly upon the copper. In the majority of cases there is a pre- 
liminary operation, called graining, by which a vary agreeable g^rained 
and slightly dead appearance is given to the articles. If we examine 
oarefully the inside of a watch we may see the peculiar pointed dead 
lustre of the parts. 

This peculiar bright dead lustre, if it may be so expressed, is 
totally different from that ordinarily obtained. For instance, it does 
not resemble the dead lustre obtained by slow and quick electro- 
deposition of gold, silver, or copper, which is coarser and duller 
than that of watch parts. Neither does it resemble the dead 
lustre obtained with the compound acids, which is the result of a 
multitude of small holes formed by the juxtaposition, upon a previ- 
ously even surface, of a quantity of more or less large grains, always 
in relief. 

The gaining may be produced by different methods, and upon 
gold, platinum, and silver ; and since the latter metal is that preferred 
we shall describe the process applied to it. 

This kind of gilding requires the following successive operations : — 

1 . Preparation of the Watch Parts. — Coming from the hands 
of the watchmaker, they preserve the marks of the file, which are 
obliterated by rubbing upon a wet stone, and lastly upon an oil- 
stone. 

2. The oil or grease which soils them is removed by boiling the 



(GILDING WATCH MOVEMENTS. tQf 

watch parts for a few minutes in an alkaline solution made of 
100 parts of water and lo of caustic soda or potassa, and rinsing them 
in clean water, which should wet them thoroughly if aU the oil has 
been remored. The articles are threaded upon a brass wire. 

3. A few gilders then cleanse them rapidly by the compound acids 
^ for a bright lustre ; others simply dry them carefully in sawdust from 

white wood. 

4. Holding the Farts. — ^The parts thus prepared are fastened by 
means of brass pins with fiat heads upon the even side of a block of 
cork. 

5. The parts thus held upon the cork are thoroughly rubbed over 
with a brush quite free from greasy matters, and charged with a 
paste of the finest pumice-stone powder and water. The brush is 
made to move in circles in order not to abrade one side more than the 
other. The whole ia thoroughly rinsed in clean water, and no particle 
of pumice dust should remain upon the pieces of the cork. 

6. Afterwards we plungpe the cork and all into a mercurial solution, 
which yery slightly whitens the copper, and is composed of — 

Water 10 litres. 

Nitaite of binoxide of mercury 2 grammes. 

Sulphuric acid .... 4 ^ 

The pieces are simply passed through the solution, and then rinsed. 
This operation, which too many gilders neglect, gives strength to the 
graining, which without it possesses no adherence, especially when 
the watch parts are made of white Crerman silver, dig^nified by the 
name of nickel by watchmakers, or when the baths contain tin in 
their composition. 

7. Oraininff, — In this state the parts are ready for the graining — 
that is to say, a silvering done in a particular manner. 

Nothing is more variable than the composition of the graining pow- 
ders ; and it may be said that each gilder has his own formula, accord- 
ing to the fineness of the g^rain desired. 

The following formulse are used in the works of M. Pinaire : — 

Silver in impalpable powder. • 30 grammes. 

fiitartrate of potaasa (cream of tartar) finely 

pulverised and passed through a silk sieve 300 „ 

Chloride of sodium (common salt) pulver- 
ised and sifted as above . . . . i kilogramme. 

It is stated that the majority of operators, instead of preparing 
their gpraining-silver, prefer buying the Nuremburg powder, whieh is 
produced by grinding a mixture of honey and silver-foil with a muUer 



igi £LECTttO-D£POSlflON OF GOLD. 

iipoD a gfroimd-glaw plate, until the proper fineness is obtained. The 
flilver is separated by dissolving the honey in boiling water, and wash- 
ing the deposited metal in a filter untQ there is no remaining trace of 
honey. The silver is then carefully dried at a gentle heat. This 
silver, like bronze powder, is sold in smaU packages : — 

Silver powder 30 grammes. 

Cream of tartar .... 120 to 150 „ 
Common salt (white and clean) . 100 „ 

Or— 

Silver powder 30 „ 

Cream of tartar 100 „ 

Common salt i kilogramme. 

All these substances should be as pure as possible, and perfectly 
diy. Cream of tartar is generally dry, but common salt often needs, 
before or after it has been pulverised, a thorough drying in a 
porcelain or silver dish, in which it is kept stirred with a glass rod or 
a silver spoon. 

The mixture of the three substances must be thorough, and effected 
at a moderate and protracted heat. 

The gfraining is the coarser as there is moro common salt in the 
mixture ; and conversely, it is the finer and more condensed as the 
proportion of cream of tartar is greater ; but it is then more difficult 
to scratch-brush. 

8. The Graining Proper. — ^This operation is effected as follows : A 
ihin paste of one of the above mixtures with water is spread by means 
of a spatula upon the watch parts held upon the cork. The cork itself 
is fixed upon an earthenware dish, in which a movement of rotation 
is imparted by the left hand. An oval brush with close bristles is 
held in the right hand, and rubs the watch parts in every direction, 
but always with a rotary motion. A new quantity of the paste is 
added two or three times, and rubbed in the manner indicated. The 
moro we turn the brush and the cork, the rounder becomes the grain, 
which is a good quality ; and the more paste we add, the larger the 
grain. 

The watchmakers generally require a fine grain, ciroular at its 
base, pointed at its apex, and close — ^that is to say, a multitude of 
juxtaposed small cones. A larger grain may, however, have a better 
appearance, but this depends on the nature and the size of the articles 
grained. 

9. When the desired gfrain is obtained, the watch parts are washed 
and then scratoh-bmshed. The wire brushes employed also come 
from Nuremburg, and are made of brass wires as fine as hair. As 
these wires are very stiff and springy, they will, when out, bend and 



GILDING WATCH MOVEMENTS. X99 

m 

turn in every direction, and no work can be done with them. It is, 
therefore, absolntelj necessary to anneal them more or less upon an 
even fire. An intelligent worker has always three scratch-brushes 
annealed to different degrees : one which is half 90ft, or half annealed, 
for the first operation of uncovering the grain ; one harder, or little 
annealed, for bring^g up lustre ; and one very tofty or fully annealed, 
used before gilding, for removing the erasures which may have been 
mAde by the preceding tool, and for scratch-brushing after the gild- 
ing. Of course the scratch-brushing operation, like the graining 
proper, must be done by striking circles, and giving a rotary motion 
between the fingers to the tool. The cork is now and then made to 
revolve. After a good scratch-brufihing, the grain, seen through a 
magnifier, should be regular, homogeneous, and with a luatre all over. 
DecoctionB of liquorice, saponaire (soapwort), or Panama wood are 
employed in this oi)eration. 



CHAPTER XII. 

VARIOUS GILDING OPERATIOlrt. 

Electro-gilding Zinc Articles.— Gilding Metals with Gold Leaf.— Cold QUd- 
ing.— Gilding Sillc, Cotton, Ac.— Pyro-gilding.^Coloar of Electro- 
deposited Gold. — Gilding in various Colours. — Colouring Processea. — He- 
colouring Gold Articles — Wet-Colour Process. — French Wet-Colouring. 
— London Process of Wet-Colouring. 

Bl«etro-slldlii8 Zinc Arttelas. — ^About thirty years ago a very 
important industry was introduced into France, whicli at onoe com- 
manded universal admiration, and a rapid sale for the beautiful pro- 
ducts wbioh were abundantly sent into the market. We allude to the 
so-called eleetro-bronzea. These exquisite works of art, many of which 
would would bear comparison with the finest of real bronzes, were in 
fact zinc castings or copies from original works of high merit, coated 
with brass, or, as it was then called, electro-hronze^ and artificially 
coloured, so as to imitate as closely as possible the charaoteristio tone 
of real bronze. At the time we speak of, articles of every conceivable 
form, from the stag beetle, mounted upon a leaf, electrotyped from 
nature, and reproduced in the form of a zinc casting, each object being 
electro-bronzed, to a highly-finished statuette or massive candelabrum, 
appeared in our shop windows and show-rooms, and presented a really 
beautiful and marvellously varied and cheap addition to our rather 
meagre display of art metal work. It was soon discovered by those 
who had the taste for possessing bronzes, but not the means to satisfy 
it, that the imitation bronzes lacked nothing of the beauty of the 
originals, while they presented the advantage of being renmrkably 
cheap, and thus within the reach of many. The process by which 
the electro -bronzing upon zinc castings is conducted is considered in 
another place, and we will now explain how articles of this description, 
that is zinc castings, may be electro-gilt, and either a bright or dead 
surface imparted to the work according to the artistic requirements of 
the article to be treated. 

Preparatton of Zinc Castings for Gilding. — In order to obtain the best 
possible results, the zinc casting — presuming it to be a work of art 
which deserves the utmost care to turn it out creditably — should first 
be examined for air or sand-holes, and these, if present, must be 



ELECTRO-GILDING ZiNC ABTICLES. 001 

stopped or plugfped with eaty-running pewter solder, and the spot 
afterwards touched up so as to resemble the surrounding surface, 
whether it be smooth or chased. When the whole article has been 
carefully examined and treated in this way, it is to be immersed for a 
few minutes only in a moderately strong potash bath, after which it 
must be weU rinsed. It is next to be placed in a weak sulphuric 
add pickle, consisting of — 

Sulphuric acid .... lo parts 

Water loo „ 

bat should not remain in the acid liquor more than a minute or two, 
after which it is to be thoroughly weU rinsed in clean water. The article, 
having a copper wire attached, is now to be placed in either a cold or 
warm brassing solution or alkaline coppering bath for a short time, 
or until it is covered with a thin deposit of either metal.* If on 
removing it from the brassing bath it is found that the soldered spots 
have not received the deposit, and present a blackish appearance, the 
artiole must be well scratch-brushed all over, and again placed in the 
bath, which, by the way, will deposit more readily upon the solder if 
the bath be warm, a brisk current employed, and gentle motion given 
to the article when first placed in the bath. The object, when placed 
in the bath a second time, should be allowed to remain therein for about 
half an hour or somewhat longer, by which time, if the solution be in 
good order, and the current sufficiently active, it will yield a deposit 
sufficiently thick either for bronzing or gilding. It is a common 
practice to deposit a slight coating of brass or copper upon zinc-work 
in a warm solution in the first instance, and then to complete the 
operation in a cold bath. 

When the object is to be left bright, that is merely scratch-brushed, 
after being coated with copper or brass as above, it is simply gilt in 
an ordinary cyanide gilding bath, and is then treated in the same way 
as ordinary brass or copper work. If, however, the article is to be 
left dead, the following method may be adopted : After being well 
rinsed, the object is to be immersed in a silvering bath in which 
it is allowed to remain until it assumes the characteristic white and 
dead lustre of electro -deposited silver. When the desired effect is 
produced, the article must be well rinsed in warm (not hot) water 
and immediately placed in a gilding bath which is in a good condition 
for yielding a deposit of the best possible colour. 

Another method, which has been much practised on the Continent, 
is thus described byKoseleur: ''Add to the necessary quantily of 
waiter one-tenth of its volume of sulphuric acid, and dissolve va. this 
add liquor as much sulphate of copper as it will take up at the 
ordinary temperature. This solution vrill mark from 20"* to 24° Baum4 

• See Chaps. XXIV. and XXV. 



aoa VABious oildino operations. 

(about I' 1600); now add water to reduce its specific gnmty to 
16** or 18° B. (about 1*1260). This galvano -plastic * bal^ is 
generally contained in large vessels of stoneware, slate, wood, or 
gutta-percha, and porous cells are immersed in it, which are filled 
with a weak solution of sulphuric acid and amalgamating salts. Plates 
or cylinders of zinc are put into these cells, and are connected with 
one or more brass rods, which rest upon the sides of the vat, and 
support the articles which are to receive the dead lustre." 

The articles of zinc, previously coated with copper or brass in an 
alkaline solution, are suspended in the above bath until they have 
acquired the necessary dead lustre, after which they are treated as 
follows : After being thoroughly well rinsed, they are immersed for 
a moment in a bath composed of — 

Nitrate of mercury ... i part 

Sulphuric acid .... 2 parts 

Water z,ooo „ 

After again rinsing, the artides are steeped in the following solu- 
tion : — 

Cyanide of potassium ... 40 parts 

Nitrate of silver zo „ 

Water 1,000 „ 

The articles are well rinsed after removal from this bath, and aie 
then ready for g^ding, the solution recommended for which is com- 
posed of — 

Phosphate of soda .... 60 parts 



Bisulphite of soda . 


10 „ 


Cyanide of potassium 


I to 2 parts 


Neutral chloride of gold . 


2 parts 


Water 


• 1,000 „ 



This batb is used at nearly the boiling point, with an intense voltaic 
current. The anode consists of platinum wire, which at first is dipped 
deeply into the solution, and afterwards gfradually raised out of the 
bath, as the article becomes coated with gold, until, towards the end 
of the operation, but a small surface of the wire remains in the bath. 
It is said that the colour of the gilding by this method is remarkable 
for its *' freshness of tone.** Some operators first gild the article by 
the dipping process before described, and then deposit tlie requisite 
quantity of g^ld to produce a dead surface by the electro process in a 
bath specially suited to the purpose. Other gilders first half -gild the 

* This term, though never a correct one, is still generally used on the con- 
tinent to designate the art of electrotyping, or the deposition of copper from 
its sulphate. 



1- 



GtLDlNO llETALS WITH OOLD LBAF. 36^ 

artiole with the battery, then dip it in the mercury bath, and after 
well rinsing, finish the operation by a second deposit of gold. In 
either case, the article is finally well rinsed in warm water, and after- 
wards dried in hot sawdust or a warm stove. Great care is taken to 
avoid handling the article so as not to stain it with the fing^ers, or to 
scratch it in any way, since the delicate frosted surface is very readily 
injured. It is also very important that the rinsing, after each opera- 
tion, should be perfectly carried out, and that the final drying is 
complete ; for if any of l^e gold solution remain upon any part of the 
work, voltaic action will be set up between the zinc and copper at the 
spot, and the article disfigured by the formation of verdigris. The 
foregoing process is specially applied to articles of zinc, such as clock- 
cases, &c., which are generally kept under glass, but may be applied 
to smaller ornamental articles which are not liable to friction in use. 

In our own praotioe we have found when g^ilding zinc, that the best 
results were obtained when all the various stages of the process, from 
the first pickling to the drying, were conducted with rapidity, the 
greatest possible attention being devoted to the various rinsing opera- 
tions. If all baths are in proper order, the various dip8 and electro- 
deposits should each only occupy from a few seconds to a few minutes, 
while the drying should be effected with the greatest possible despatch, 
so that the object, being but thinly coated with metals which are 
electro-negative to itself, may not be subjected to electro-chemical 
action in parts owing to the presence of moisture or traces of the 
gilding solution. 

OUdlns Metals iritli Gold &mi£ — ^Articles of steel are heated until 
they acquire a bluish colour, and iron or copper are heated to the same 
degree. The first coating of gold leaf is now applied, which must be 
gently pressed down with a burnisher, and again exposed to gentle 
heat ; the second leaf is then applied in the name way, followed by a 
third, and so on ; or two leaves may be applied instead of one, but the 
last leaf should be burnished down while tibe article is cold. 

Cold CMldlni;. — A very simple way of applying this process is to 
dissolve half a pennyweight of standard gold in aqua regia ; now 
steep several small pieces of rag in the solution until it is all absorbed ; 
dry the pieces of rag, and then bum them to tinder. To apply the 
ashes thus left, rub them to a powder, mix with a little water and 
common salt, then dip a cork into the paste thus formed, and rub it 
over the article to be gilt. 

Oildlns 811k, Cotton, Sbc — ^There are several methods by which 
textile fabrics may be either gilt or silvered. One method is to 
stretch the fabric tightly upon a frame, after which it is immersed in 
a solution of acetate of silver, to which ammonia is added until the pre- 
oqiitate at first formed becomes dissolved, and a clear solution obtained. 



2C4 TABIOUS OILDiHa OFEBATIO^d. 

After immersion in tMs solution for an hour or two, the thread or 
fabric is first dried, and then submitted to a current of hydrogen gas, 
bj which the silver becomes reduced and the surface metallised. In 
this condition it is a conductor of electricity, and maybe either gilt or 
silyered in any ordinary cyanide solution. By another method, the 
piece of white silk is dipped in an aqueous solution of chloride of 
gfold ; it is then exposed to the fumes of sulphurous add gas, pro- 
duced by burning sulphur in a closed box, when in a very short time 
the entire piece will be coated with the reduced metal. 

Fyro-gUdlas. — ^This procesfl, which is recommended for coating 
iron and steel, is conducted npon the same principle as pyro -plating,* 
except that the preoioui metal is deposited in sereral layers, instead 
of , as in the former case, depositing the required coating in one 
operation. The steel article being prepared as recommended for 
pyro-plating, first receives a coating of gold in the g^ding-bath ; it 
is next heated until the iilm of gold disappears ; it is then agnin g^t, 
and heated as before, these operations being repeated until the last 
layer remains fully on the surface. 

Ool0iir of Blaetro-dapoBlted OOUL — It might readily be imagined 
that gold, when deposited from its solution upon another metal, 
would necessarily assume its natural colour, that is, a rich orange 
yellow. That such is not the case is well known to all who have 
practised the art of gilding, and the fact may easily be demonstrated 
by first g^ding a piece of German silver in a eold cyanide solution of 
gold, and then raising the temperature of the solution to about 130*^ 
Fahr. If now a similar piece of metal be gilt in the warm solution, 
and the two gilt surfaces compared, it will be found that while the 
deposit from the cold solution is of a pale yellow colour, that obtained 
by the warm solution is of a deeper and richer hue. The colour of 
the deposit may also be influenced by the nature of the current, the 
same solution being used. For example, the g^ld deposited by the 
current from a Bunsen battery is generally of a finer and deeper colour 
than that obtained by the Wollaston battery. In the former case, 
the superior intensity of the current seems to favour the colour of the 
deposit. This difference, however, is not so strongly marked in the 
case of some other gold solutions, as that prepared by precipitating 
gold with sulphide of ammonium, and redissolving the precipitate 
with cyanide, for example, which yields an exceedingly good coloured 
deposit with copper and zinc elements (Wollaston or Daniell). Since 
the colour of the gold deposit is often of much importance to the 
electro -gilder, we purpose g^\dng below the various means adopted 
for varying the colour of the deposit to suit the re<iuirements of what 
we may term faney gilding. 

OUdins In Varioas Ooloora. — A very deep coloured deposit of 

* Sec p. 274* 



GILDINO IN VABIOUS COLOURS. 205 

gold may be obtained in an old gold solution, in which organic 
matter has accumulated from imperfect rinsing of the work after 
scratch - brushing, and in which there is a good proportion of 
free cyanide, by employing a strong current and exposing a huge 
surface of anode. In this case the deposit is of 9k foxy colour, as it is 
tenned, and when scratch -brushed exhibits a depth of tone which, 
while being unsuited for most purposes, may be useful as a variety in 
some kinds of fancy gilding where a strong contrast of colours is a 
requisite. The colour of the deposit is also much influenced, as before 
observed, by the extent of oimde mrfaee exposed in the bath during the 
operation of gilding ; if a larger surface be exposed than is propor- 
tionate to the cathode surface (or work being gilt) the colour is dark, 
whereas when the anode surface exposed is heUno the proper propor- 
tion, the deposit will be of a pale colour. Motion also affects the 
colour of the gold deposit — sometimes in a very remarkable degree 
— the colour being lighter when the article is moved about in the 
solution, and darker when allowed to rest. These differences are more 
marked, however, with old and dark coloured solutions than with 
recently prepared solutions, or such as have been kept scrupulously 
free from the introduction of organic impurities. 

For ornamental gilding, as in cases where chased or engraved silver 
or plated work is required to present different shades of colour on its 
various surfaces, solutions of gold may be prepared from which gold 
of various tints may be obtained by electro -deposition. These solu- 
tions are formed by adding to ordinary cyanide gilding baths vary- 
ing proportions of silver or copper solution, or both, as also solutions 
of other metals ; but in order to insure uniformity of results, the solu- 
tions should be worked with anodes formed from an alloy of the same 
character ; or at least, if an alloy of silver and gold, for example, is 
to be deposited, an anode of gold and one of silver should be employed 
in order to keep up the condition of the compound solution. 

Oreen Gold. — This is obtained by adding to a solution of double 
cyanide of gold and potassium a small proportion of cyanide of silver 
solution, until the desired tint is obtained. The solution should be 
worked cold, or nearly so. 

Med Gold. — To a solution of cyanide of gold add a small quantity 
of cyanide of copper solution, and employ a moderately strong current. 
It is best, in making these additions, to be^in low, by adding a very small 
proportion of the copper solution at first, and to increase the quantity 
gradually until the required tone is obtained, since an excess of the 
copper solution would produce a deposit of too coppery a hue. The 
tint generally required would be that of the old-fashioned gold and 
copper alloy with which the seals and watch cases of the last, and 
earlier part of the present, century were made. 



206 VARIOUS GTLD^^j/q OPERATIONS. 

Pink G^oW.— This may be o;btamed by firet gilding the article in the 
nsual way, then depositing- a slight coating in the preceding bath, and 
afterwards depositing ajtnere pellicle of silver in the silvering bath. 
The operation requires great care to obtain the desired pink tint. 
The article is afterwards burnished; but since the silver readily 
becomes oxidised (unless protected by a colourless varnish) the effect 
will not be of a permanent character. 

Fale Straw-coloured Gold. — Add to an ordinary cyanide solution 
a small quantity of silver solution, and work the compound solution 
eold, with a small surface of anode and a weak current. 

OAkrarlns Troe%am9B, — ^When the g^ding is of an inferior colour 
it is sometimes necessary to have at command some method by which 
the colour may be improved. There are several processes by which 
this may be effected, but in all cases there must be a sufficient coating 
of gx>ld upon the article to withstand the action of the materials 
employed. This condition being fulfilled, the artificial colottring 
processes may be applied with advantage, and gold surfaces of great 
beauty obtained. Of the processes given below, the first formula 
will be foimd exceedingly useful, since it may be applied to work 
which, though fairly well gUt, need not be so stoutly coated as is 
necessary when employing the second formula. It is specially useful 
for bringing up a g^ood colour upon brooches, albert chadns, and small 
articles generally. It ia technically known by the name **greefD. 
colour," and is composed as follows : — 

0Z8. dwts. gra. 
I. Sulphate of copper ...020 
French verdigris o 4 la 

Sal ammoniac ....040 

Nitre 040 

Acetic acid (about) ... 100 

The sulphate of copper, sal ammoniac, and nitre are first to be pulver- 
ised in a mortar, when the verdigris is to be added and well mixed 
with the other ingredients. The acetic acid is then to be poured in, 
a little at a time, and the whole well worked up together, when a 
thin mass of a bluish green colour will result. The article to be 
coloured is to be dipped in the mixture and then placed on a clean 
piece of sheet copper, which is next to be heated over a clear fire, 
until the compound assumes a duU black colour ; it is now allowed to 
cool, and is then plunged into a tolerably strong stdphuric acid 
pickle, which soon dissolves the colouring salts, leaving the article of 
a fine gold colour. It is generally advisable to well scratch-brush 
the article before colouring, when it will come out of the pickle 
perfectly bright. When removed from the pickle, the article must 
be well rinsed in hot water, to which a small quantity of carbonate of 



BBOOLOURINa GOLD ABTIGLBS. ao7 

potash should be added ; it should next be brushed with warm soap 
and water, a soft brush being employedi and again rinsed in hot 
water, after whioh it may be placed in warm box sawdust, being 
finallj brushed with a long-haired brush. 

II. When the work is strongly gilt, but of an indifferent colour, 
the following mixture may be used : — 

Powdered alnm .... 3 oonces 

„ nitre .... 6 „ 

„ sulphate of zinc • • 3 n 

„ common salt . . . 3 ,, 

These ingredients are to be worked up into a thiokish paste, lind the 
articles brushed over with it ; they are then to be placed on a pieoe 
of sheet iron, and heated oyer a clear charcoal or coke fire until they 
become nearly black ; when cool they are to be plunged into dilute 
muriatic or sulphuric acid pickle. 

B d c o l o ii ring Oold Artlclea. — It not unfrequently happens that 
an electro-g^der is required by his customers to renovate articles of 
gold jewellery, so as to restore them to the original condition 
in which they left the manufacturers. Although it has been the 
common practice, with some electro-gilders, to depend upon their 
baths to give the desired effect to what is called " coloured '* jewellery, 
in some cases it would be better to apply the methods adopted by 
goldsmiths and jewellers for this purpose, by which the exact effect 
required can be more certainly obtained. There are two methods of 
colouring gold articles ; namely, *' dry colouring,'* which is applied 
to articles made from 18 -carat gold and upwards, and '* wet-colour- 
ing," which is adopted for alloys of gold below that standard, but 
seldom lower than 12 -carat. 

The mixture for dry-eolouring is composed of 

Nitre 8 ounces 

Alum 4 „ 

Common salt 4 „ 

16 „ 
Or the following : — 

Sal ammoniac 4 ounces 

Saltpetre 4 ^* 

Borax An 



Z2 



ft 



The Ingredients must first be reduced to a powder, and then put 
into an earthen pipkin, which is to be placed over a alow fire to allow 
the Sfklts to fuse gradually; to assist this, the mixture should be 



ioS VABIOUS GILDING OPERATIONS. 

fltiirod with an iron rod. When the fused salts begin to rise in the 
Teeseli the pieces of work, suspended bj a fine silver or platinum wire, 
should be at once immersed, and kept moved about until the liquid 
begins to sink in the colouring-pot, when the work must be removed, 
and plunged into clean muriatic acid pickle, which will dissolve the 
adhering salts. The colouring mixture will ag^ain rise in the pot, 
after the withdrawal of the work, when it may be reimmersed (when 
dry) for a short time, and then pickled as before ; it is then to be 
rinsed in a weak solution of carbonate of soda or potash, and after* 
wards well washed in hot soda and water, next in clean boiling water, 
and finally put into warm box sawdust to dry. Previous to colouring 
the work, it should be highly polished or burnished, although the 
latter operation may be performed after the work has been coloured ; 
the former method is, however, the best, and produces the most 
pleasing effect. 

Wet'Colotiring Process. — This is applied to gold articles made from 
alloys below 1 8 -carat, and though there are many formulae adopted 
for colouring gold of various qualities below this standard, we 
must limit our reference to one or two only, and for ample infor- 
mation upon this subject direct the reader's attention to Mr. Gee's 
admirable Goldsmith* s Handbook* The ordinary ** wet colour," as 
the jewellers term it, consists chiefly in adding a little water to the 
ingredients formerly given, the proportions of the salts being gene- 
rally about the same ; that is, nitre 8 ounces, alum and common salt 
of each 4 ounces. These ingredients being reduced to a fine powder 
and mixed together, are worked up into a thick paste with a little hot 
water in a good-sized pipkin or crucible, which is placed over a slow 
fire and heat^ gradually, the mixture being stirred with a wooden 
spoon until it boils up. The work is now to be introduced as before 
and allowed to remain for several minutes, when it must be withdrawn 
and plunged into boiling water, which will dissolve the colouring 
salts and show how far the colouring has progressed. When the 
mixture exhibits a tendency to boil dry, an occasional spoonful of 
hot water must be added to thin it, but never while the work is in 
the pot. When the work is first put into the colour it becomes nearly 
black, but assumes a lighter tone after each immersion until the 
characteristic colour of fine gold is obtained. When the operation is 
complete, the work will bear a uniform appearance, though somewhat 
dead, and may be brightened by burnishing or scratch-brushing. 
After each dipping the work must be well rinsed in clean boiling 
water. It must be finally plunged into hot water, and, after weU 
shaking, be put into warm boxwood sawdust. 

* " The Goldsmith's Handbook," by George E. Gee. London : Crosby 
Lookwood and Son. 



RECOLOUBING GOLD ABTIOLES. SOQ 

Fronck Wet CoUntring. — The fonnula for this is : — 

Saltpetre 8 ounces 

Common salt 4 >» 

Alum An 

The ingredients must be finely pulverised, as before, and intimatelj 
mixed ; they are then to be put into a good-sized pipkin or crucible, 
and sufficient hot water added to form the whole into a thick paste. 
The mixture should be slowly heated, and stirred with a wooden 
spoon, when it will soon boil up. The work is then to be immersed 
for several minutes, then withdrawn and plunged into boiling water, 
which, dissolving the salts, will allow the work to be examined, when, 
if not of a sufficiently good colour, it must be reimmersed for a short 
time. As the mixture thickens by evaporation small quantities of 
boiling water must be added occasionally, but only after the work has 
been withdrawn. On the first immersion the work assumes a blackish 
colour, but at each successive immersion it becomes lighter, as the 
baser metals become removed from the surface of the work, until it 
finally assumes the characteristio colour of fine gold. This process 
should be applied to gold of less than 1 6 carats. 

London Froeesa of Wet Colouring. — For gold of not less than 15 carats 
the foUowing mixture is used : — 

Nitre 15 ounces 

Common salt 7 » 

Alum 7 » 

Muriatic acid i » 

30 
The salts are to be powdered, as before ; into a crucible about 
8 inches high and 7 inches in diameter, put about two spoonfuls of 
Water, then add the salts, place the crucible on the fire, and heat 
gradually until fusion takes place, keeping the mixture well stirred 
with a wooden spoon. The article, which should first be boiled in 
nitric acid pickle, is then to be suspended by a platinum wire, and 
immersed in the fused mixture for about five minutes, then withdrawn 
and steeped in boiling water. The muriatic acid is now to be added 
to the mixture, and when it again boils up the article is to be immersed 
for about five minutes, then again rinsed in boiling water. A spoon- 
ful of water is now to be added to the mixture, and the work again 
put in for about three minutes, and again rinsed ; now add two spoon- 
fuls of water to the mixture, boU up, and immerse the work for two 
minutes, and rinse again. Finally, add about three spoonfuls of water, 
and, after boiling up, put in the work for one minute, then rinse in 
abundance of clean boiling water, when the work will present a beau- 
tiful colour. The work should then be rinsed in a very dilute hot 
solution of potash, and again in clean boiling water, after which it 
should be placed in dean, warm boxwood sawdust. 

r 



CHAPTER XIIL 
MERCURY GILDINa. 

Preparation of the Amalgam.— The Mercurial Solution.— Applying the 

Amalgam — Evaporation of the Mercury. — Colouring.— Bright and Dead 

Gilding in Parts— Gilding Bronzes with Amalgam.— Ormoulu Ck>1our. 

-Red-Gold Colour.— Ormoulu. — Red Ormoulu.— Yellow Ormoulu.— 

Dead Ormoulu.— Gildere* Wax. — Notes on Gilding. 

Ai/THOITQH the process of gilding metals with an amalgam of gold and 
mercury, or quicksilyer, is not, strictly speaking, an electro -chemical 
art, it is important that this system of g^ding should be known to 
the electro-gilder for several reasons : it is the chief process by which 
metals were coated with gold before the art of electro -gilding was 
introduced ; it is still employed for certain purposes, and many arti- 
cles of silver which have been mercury gilt occasionally come into the 
electro-depositor*8 hands for regilding, and which are sometimes 
specially required to be subjected to the same process, when the voltaic 
method is objected to. 

Mercury -gilding, formerly called wash -gilding, water-gilding, or 
amalg^am-gilding, essentially consists in brushing over the surface of 
silver, copper, bronze, or brass, an amalgam of gold and quicksilver, 
and afterwards volatilising the mercury by heat. By repeated appli- 
cations of the amalgam and evaporation of the mercury, a coating of 
gold of any desired thickness may be obtained, and when properly 
carried out the gilding by this method is of a far more durable 
character than that obtained by any other means. As we have before 
observed, the process, unless conducted with great care, is a very 
unhealthy one, owing to the deleterious nature of the fumes of mer- 
cury to which the workmen are exposed, if these are not properly 
carried off by the flue of a suitable furnace. 

Preparation of flM A*wig«™ — Mercury, as is well known, has 
the peouliar property of alloying or amalgamating itself with gpold, 
silver, and some other metals and alloys, with or without the aid of 
heat. To prepare the amalgam of gold for the purpose of mercury 
gilding, a weighed quantity of fine or standard gold is first put into a 
crucible and heated to dull redness. The requisite proportion of 
mercury — 8 parts to i part of gold — is now added, and the mixture ia 



APPLTINO THE AMALOAM. 21 E 

Rtirred with ft slightly crooked iron rod, the heat being kept up until 
the gold is entirelj dissolved by the mercnry. The amalg^am is now to 
be poured into a small dish about throe parts filled with water, in 
which it is worked about with the fingers under the water, to squeeze 
out as much of the excess of mercury as possible. To facilitate this, 
the dish is sUghtly inclined to allow the superfluous meroury to flow 
from the mass, which soon acquires a pasty condition capable of 
receiving the improssion of the fingers. The amalgam is afterwards 
to be squeezed in a chamois leather bag, by which a further quantity 
of meroury is liberated ; the amalgam which remains after this final 
treatment consists of about 33 parts of mercury and 67 of gold m 100 
parts. The meroury which is prossed through the bag retains a good 
deal of gold, and is employed in proparing fresh batches of amalgam. 
It is very important that the meroury employed for this purpose be 
puro. The g^ld employed may be either fine or standard, but 
water-gilders generally use the metal alloyed either with silver or 
copper ; if to be subjected to the after process of colouring, standard 
alloys should be employed, since the beauty of the colouring process 
depends upon the romoval, chemically, of the inferior metals, silver, 
copper, or both, from the alloy of gold, leaving the puro metal only 
upon the surface. The amalgfam is crystalline, and produces a peculiar 
crackling sound when prossed between the fingers close to the ear. 

It is usual to keep a moderate supply of gold amalgam in hand 
when meroury-gilding forms part of the guilder's ordinary business, 
and the compound is divided into a series of small baUs, which are 
kept under water ; it is not advisable, however, to allow the amalgam 
to remain for a long period before being employed, since a peculiar 
phenomenon known as liquation takes place, by which the amalgam 
loses its uniformity of composition, the g^ld being more dense in some 
parts than in others. 

TlM IK«r6iirlal Bolntton. — To apply the amalgam, a solution of 
nitrate of mercury is employed, which is prepared by dissolving, in a 
glass flask, 100 parts of meroury in no parts of nitric acid of the 
speoifio gravity i -33, gentle heat being applied to assist the chemical 
action. The red fumes which are given oft during the decomposition 
must be allowed to escape into the chimney, since they are highly 
deleterious when inhaled. When the meroury is all dissolved, the 
solution is to be diluted with about 25 times its weight of distilled 
water, and bottled for use. 

Apptyins t]i« Awijr»«» — The pasty amalg^am is spread with the 
blade of a knife, upon a hard and flat stone called the gilding stom^ 
and the article, after being well cleaned and scratch-brushed, is 
treated in the following way : the gilder takes a small scratch* 
brush, formed of stout brass wire, which he first dips in the solutioi) 



2X2 HEBCURY OILDINa 

of nitrate of mercury, and then next draws it over the amalgam, by 
which it takes up a small quantity of the composition ,* he then passes 
the brush carefully over the surface to be g^t, rei>eatedly dipping the 
brush in the mercurial solution and drawing it oyer the amalgam 
until the entire surface is imiformly and sufficiently coated. The 
article is afterwards well rinsed and dried, when it is ready for the 
next operation. 

BTaporation of th* BSarenry. — For this purpose a charcoal fire, 
resting upon a cast-iron plate, has been generally adopted, a simple 
hood of sheet iron being the only means of partially protecting the 
workmen from the injurious effects of the mercurial vapours. M. 
D'Arcet, of Paris, invented a furnace, or forge, with an arrangement 
by which the workman could watch the progress of his work through 
glass, and thus escape the injurious effects of the mercury vapours. 
The difficulty of seeing the process clearly, however, during the more 
important stages of the operation (owing doubtless to the condensa- 
tion of the mercurial vapour upon the glass), caused the arrangement 
to be disapproved by those for whose well-being it was specially 
designed, and the simple hood, regardless of its fatal inadequacy, is 
still preferred by many mercury gilders. When the amalgamated 
article is rinsed and dried, the gilder exposes it to the glowing char- 
coal, turning it about, and heating it by degrees to the proper point ; 
he then withdraws it from the fire by means of long pincers or tong^, 
and takes it in his left hand, which is protected with a leather or 
padded glove, and turns it over the fire in every direction, and while 
the mercury is volatilising, he strikes the work with a long-haired 
brush, to equalise the amalgam coating, and to force it upon such 
parts as may appear to require it. 

When the mercury has become entirely volatilised, the gfilding has 
a dull gTeenish-ycUow colour, and the workman examines it to ascer- 
tain if the coating is uniform ; if any bare places are apparent, these 
are touched up with amalgam, and the article again submitted to the 
fire, care being taken to expel the mercury gradually. 

Colonrlas. — The article is next well scratch -brushed, when it 
assumes a pale greenish colour ; it is afterwards subjected to another 
heating to expel any remaining mercury, when, if sufficient amalg^am 
has been applied, it acquires the characteristic orange -yellow colour 
of fine gold. It is next submitted to the process of colouring. If 
required to be bright, the piece of work is burnished in the ordinary 
way, or, according to the nature of the article, is subjected to ilie 
ormoulu process described further on. When the surface is required 
to be dead, or frosted, the article is treated somewhat in the same way 
as ** dry coloured" gold jewelleiy work, that is, it is brushed over 
with a hot paste composed of common salt, nitre, and alum, fused in 



BRIGHT AND DEAD GILDING IN PABTS. 31 3 

the water of orystallifiation of the latter, after whioh it is heated upon 
a brisk charcoal fire, without draft, and moved about until the ^ts 
become first dried and then fused ; the article is then plunged into a 
Tossel containing a large quantity of cold water, in which the colour- 
ing salts are dissolved, and the dead or matted appearance of the 
work becomes at once visible. When applying the amalgam for dead 
gilding, great care must be exercised to insure a sufficiently stout 
coating of g^ld upon the work, otherwise the colouring salts will 
surely attack the underlying metal. When about to colour the work 
as above, the operator binds the article by means of iron wire to a 
short rod of the same metal ; he then either dips the article in the 
colouring paste or applies it with a brush, and after gentiy drying it, 
holds the piece over the fire until the perfect fusion of the composition 
has taken place, when it is at once dipped in water. The coloured 
marks left by the wire are removed by a weak solution of nitric acid. 

Brlsbt and Head CMldlns In Farts. — ^When it is desired to have 
some parts of an article burnished and other parts left dead, the 
former are protected by a mixture of Spanish white (pure white chalk], 
bruised sugar candy, and either gum or glue, dissolved in water. The 
mixture of alum, nitre, and common salt is then applied to the parts 
to be left dead, the article afterwards dried, and heated over the char- 
coal fire as before until the dried salts have been fused, when it is at 
once plunged into cold water, and subsequentiy in dilute nitric acid, 
being finally well rinsed and dried. The protected parts are then 
subjected to the operation of burnishing, when the article is complete. 

Another method adopted in France, in which electro -g^ilding takes 
a part, is described as follows : Those parts which are intended for 
a dead lustre are first gilt with the amalgam ; the article is then 
heated, scratch-brushed, and re-heated to the orange-yellow colour. 
Then, with the battery, a sufficientiy strong gold deposit is given to 
the whole, without regard to the parts already mercury-gilt. AU the 
surfaces are next carefully scratch-brushed, and the electro-gilt por- 
tions are brushed over, first with a thin mixture of water, glue, and 
Spanish white, and afterwards with a thick paste of yellow clay. 
After drying, the mercury -gilt portions are covered with the paste 
for dead-gilding (alum, nitre, &c.), and the article heated until the 
salts fuse, when it is plunged into water and treated as above. 

Boeeleur, however, considers this method open to several objections, 
among which is, red spots are apt to be produced upon such places as 
may have been too much heated, or where the g^ld has not been suffi- 
cientiy thick. He recommends the following by preference : '*Gild 
with amalgam, and bring up the dead lustre upon those jmrtions 
which are to receive it, and preserve [protect] them entirely with a 
stopping-ofif varnish. After thorough drying, cleanse the object by 



214 MERCURY GILDINO. 

dipping it into acida in the usual manner, and gild in the electro- 
bath. The vamiBh withstands all these acids and solutions. When 
the desired shade is obtained, dissolve the varnish with gasoline or 
benzine, which, unless there has been friction applied, do not injure 
in any waj either the shade or velvety appearance of the dead lustre. 
Wash in a hot solution of cyanide of potassium, then in boiling water, 
and allow to dry naturally. . . . G-Hding with dead lustre, whatever 
process be employed, suits only those objects which will never be sub- 
jected to friction ; even the contact of the fingers injures it." 

OUdlBiT Bronses wltb Amalgam. — The article is first annealed 
very carefully, as follows : The gilder sets the piece upon burning 
charcoal, or peat, which yields a more lively and equal flame, covering 
it up so that it may be oxidised as little as possible, and taking oare 
that the thinner parts do not receive an imdue amount of heat. This 
operation is performed in a dark room, so that the workman may see 
when the desired cherry-red heat is reached. He then lifts the piece 
from the fire, and sets it aside to cool in the air g^radually. When 
cold, the article is steeped in a weak sulphuric acid pickle, which 
removes or loosens the coating of oxide. To aid this he rubs it with 
a stiff and hard brush. When the article has been thus rendered 
bright, though it may appear uniform, it is dipped in nitric aoid and 
nnsed, and ag^in rubbed with a long-haired brush. After washing 
in clean water, it is dried in hot sawdust or bran. This treatment 
somewhat reduces the brightness of the surface, which is favour- 
able to the adhesion of the gold. The amalgam is next applied with 
the scratch-brush, as before, and the object then heated to expel the 
mercury. If required to be dead, it is treated with the oolouring- 
salts, as before described. 

Ormonln Colour. — To obtain this fine colour upon bronze or other 
work, the gilt object is first lightly scratch-brushed, and then made 
to cotne back again ^ as it is termed, by heating it more strongly than if 
it were to be left dead, and then allowed to cool a little. The oimoulu 
colouring is a mixture of hematite (peroxide of iron), alum, and sea- 
salt, made into a thin paste with vinegar, and applied with a brush 
until the whole of the gilded surface is covered, except such parts as 
are required to be burnished. The object is then heated until it 
begins to blacken, the proper heat being known by water sprinkled 
over it producing a hissing noise. It is next removed from the fire, 
plunged into cold water, and washed, and afterwards rubbed with a 
brush dipped in vineg^ if the object be smooth, but if it be chased, 
dilute nitric acid is employed for this purpose. The article is finally 
washed in clean water, and dried at a gentle heat. 

Sed (iold Oolonr. — To produce this colour, the composition known 
as gUdert* wax is used. The article, after being coated with amalgam^ 



OBHOtfLn. 21$ 

ifl heated, and while stOl hot is soBpended by an iron wire, and 
ooated with guilders' wax, a composition of beeswax, red ochre, ver- 
digris, and alum. It is then strongly heated over the flame of a wood 
fire ; sometimes small quantities of the gilders* wax are thrown into 
the fire to promote the burning of the fuel. The object is turned 
about in every direction, so as to render the action of the heat uni- 
form. As soon as all the wax has become burnt off, the flame is 
put out, and the article plunged into cold water, weU washed, and 
brushed oyer with a scratch -brush and pure yinegar. Should the 
colour not be uniform or sufficiently good, the article must be coated 
with yerdigris dissolved in vinegar, dried over a gentle fire, then 
plunged into cold water and brushed over with vinegar ; and if the 
colour is of too deep a tone, dilute nitric acid may be substituted for 
the vinegar. After well washing, the article is burnished, then again 
washed, and finally wiped with soft linen rag, and lastly dried at a 
gentle heat. 

Ormonlii. — ^The beautiful surface noticeable on French clocks and 
other ornamental work is produced by the process called ormouiu. 
The article is first g^t, and afterwards scratch-brushed. It is then 
coated with the thin paste of saltpetre, alum, and oxide of iron before 
mentioned, the ingredients being reduped to a fine powder, and 
worked up into a paste with a solution of safEron, annatto, or other 
colouring matter, according to the tint required, whether red or 
yellow. When the gilding is strong, the article is heated until the 
coating of the above mixture curls over by being touched with a wet 
finger. But when the gilding is only a slight film of gold, the mix- 
ture is merely allowed to remain upon the article for a few minutes. 
In both cases, the article is quickly washed with warm water containing 
in suspension a certain quantity of the materials referred to. The article 
must not be dried without washing. Such parts as may have acquired 
too deep a colour are afterwards struck with a brush made with long 
bristies. By a series of vertical strokes with the brush the uniformity 
of surface is produced. If the first operation has not been successful, 
the colouring is removed by dipping the article in dilute sulphuric 
acid, and after well rinsing, the operation is repeated until the desired 
effect is obtained. 

£ed Ormouiu is produced by employing a mixture composed of alum 
and nitre, of each 30 parts ; sulphate of zinc, 8 parts ; common salt, 
3 parts ; red ochre, 28 parts ; and sulphate of iron, i part. To this 
may be added a small quantity of annatto, madder, or other colouring 
matter, g^round in water. 

Yellow Ormouiu is produced by the following : red ochre, 1 7 ; 
potash alum, 50 ; sulphate of zinc, 10 ; common salt, 3 ; and salt- 
petze 20 parts, made up into a paste as before. 



2l6 BfERCUBT OILDINO. 

Dead Ormoulu^ for clocks, is composed of saltpetre, 37 ; alum, 42 ; 
common salt, 12 ; powdered glass and sulphate of lime, 4 ; and water, 
5 parts. The whole of these substances are to be well ground and 
mixed with water. 

Oildera' Wax^ for producing a rich colour upon g^t work, is made 
from oil and yellow wax, of each 25 parts; acetate of copper, 13 parts; 
and red ochre, 37 parts. The oil and wax aro to be united by melt- 
ing, and the substances, after being well pulverised, added gradually. 

ITotes on OMldlns- — When gilding single small articles, it is a 
gpood plan to hold the anode by its conducting wire in the left hand, 
so as to be able to control the amount of surface to be immersed in 
the bath, which must be considerably lees (with hot solutions 
especially) than that of the article to be gilt. The object being slung 
by thin copper wire, the free end of the wire is to be twisted round 
the negative electrode (the wire issuing from the zinc of the battery), 
and the article then dipped into the bath. The article should 
gradually become coated, that is, in a few seconds, but not immediately 
after it is immersed. Gentle motum will secure an tmiform deposit. 
After the article has become gfilt all over, the anode may be lowered a 
little deeper into the bath, and the gfentle motion of the article kept 
up for a short time, say from three to five minutes, or until it appears 
to be fairly coated. The length of time the article is to remain in the 
bath must be regulated by the price to be paid for the g^ding. If a 
really gr^xMl gilding is required, it may be necessary, after about five 
minutes* immersion, to rescratch-brush the article, dip it in the mer- 
curial solution for a moment, or until it is white, and then, after well 
rinsing, gfive it a second coating. Ordinary gilding, however, is 
generally accomplished in a single immersion. 

1, Gilding Jewellery Articles. — Ohaios, brooches, rings, pins, and 
other small articles of silver or metal jewellery should first be slung 
upon thin copper wiro, then dipped for a few moments only in a warm 
potash bath. The articles are then to be rinsed in warm water and 
scratch-brushed, after which they are again rinsed, and at once 
immersed in the gold bath. When sufficientiy gfilt, the work should 
be rinsed in a vessel kept specially for the first rinsing, which should 
be saved, and afterwards in clean water. It is then to be properly 
scratch-brushed, and plunged into hot water ; next shaken about to 
remove as much water as possible, and finally put into warm boxwood 
sawdust. After moving it about in the boxdust for a few moments, 
the artide requires to be shaken or knocked against the palm of the 
hand, to dislodge the sawdust. It is now ready to be wrapped up for 
the customer, pink tissue paper being preferable for gilt work, and 
blue or white tissue paper for silver or plated work. 

2. Treatment of Gilding Solutions. — ^When the gilding bath has been 



KEEPING THE SOLUTIONS UNIFOBM. 21 7 

heated for a few hours, it will have lost a considerable proportion of 
its water, which must be made up bj adding an equivalent of hot 
water. If this is not done, the bath, being stronger than it was 
origpinallj, will probably 3rield a non-adhering deposit, and the gold 
m&j strip oif the work under the soratoh-bmsh. The solution should 
be kept up to its standard height in the gpilding vessel by frequent 
additions of hot water during the whole time it is subjected to evapo- 
ration by the gas-burner, or other heating medium. The solution- 
line of the bath should be marked upon the inside of the vessel when 
the liquid is first poured in. 

4. Gilding different Metals, — Silver and metal articles should not be 
dung upon the same wire and immersed in the bath at the same time, 
sinoe brass, gilding metal, and copper receive the deposit more readily 
than silver. The latter metal should first receive a coating, after 
which, if time is an object, the metal articles may be placed in the 
bath with the partly-gilt silver articles. 

5. En^layment of Impure Gold. — When it is desired to make up a gold 
solution from impure material, as from *' old gold," for instance, the 
alloy should first be treated as follows : To i ounce of the alloyed 
gold, if of good quality — say 18 -carat gold, for example — add 2 ounces 
of silver, which should not be below standard ; melt them in a crucible 
with a little borax, as a flux. When the alloy is thoroughly melted 
it is to be poured into a deep vessel containing cold water, which 
must be briskly stirred in one directum, while the molten alloy is being 
poured in. This operation, termed granulation, causes the metal to 
assume the form of small lumps, or grains, as they 

are called. The water is now to be poured off and 
the g^ins of alloy collected and placed in a flask, 
such as is shown in Fig. 70. To remove the silver 
and copper from the granulated metal, a mixture of 
two parts water and one part strong nitric acid is 
poured into the flask, which is then placed on a 
sand-bath, moderately heated, until the red fumes 
which at first appear have ceased to be visible 
in the bulb of the vessel. The clear liquid is now ^'S* 7^' 

to be carefully poured off into a suitable vessel — a 
glass *' beaker,'* such as is shown in Fig. 78, being a convenient 
vessel for the purpose. A small quantity of the dilute acid should 
then be poured into the flask, and heat again applied, in order to 
remove any remaining copper or silver. If, on the addition of the 
fresh acid, red fumes do not appear in the flask the operation is com- 
plete, and the grains of metal will have assumed a dark brown colour. 
The acid must now be poured off, and the grains well washed, while 
in the flask, with distilled water. The residuum is pure gold and 




2l8 NOTES ON OILDING. 

may be at once dissolved in aqua regia, and treated in the same way 
as reoommended for ordinary g^rain gold. The silver may readily be 
recovered from the decanted liquor, which, owing to the presence of 
copper removed from the orig^al alloy, will be of a green colour, by 
immersing in it a strip of stout sheet copper, which in the course of a 
few hours will reduce the silver to the metallic state, in the form of a 
grey, spongy mass. When all the silver is thus thrown down, the 
green liquor is to be poured off and the silver deposit well washed with 
hot water. Being now pure silver, it may be used for making up 
solution, or fused with dried carbonate of potash into a button. 

6. Oilding Filigree Work. — Silver filigree work which has been an- 
nealed and pickled assumes a dead-white surface, which does not 
readily ** take *' the g^ding unless the bath is rich in gold and free 
cyanide, and the current strong. If such parts of the article as can 
bQ reached by the scratch-brush are brightened by this means, the 
interstices which have escaped the action of the brush will sometimes be 
troublesome to gild, while the brightened parts will readily receive 
the deposit. In this case, if the bath is wanting in free cyanide, an 
addition of this substance must be made, and the article must be kept 
rather briskly moved about in the solution, and a g^)od surface of 
anode immersed until the dead- white portions of the article are gilt. 
The anode may then be raised a little, and the piece of work allowed 
to rest in the bath, without movement, until the desired colour and 
thickness of coating are obtained. Some persons prefer dipping this 
kind of work in the mereury solution before gilding, by which a more 
uniform deposit is obtained. This plan is useful when the gold bath 
has been recently prepared. It must not be forgotten, however, 
that in gilding filigree work the battery current must be brisk. 

7. Oilding Insidea of Ve$8els. — It sometimes happens, when gilding the 
interior of silver or electro-plated tankards, mugs, &c., which have 
been highly embossed or chased, that the gold, while depositing 
freely upon the prominent parts, refuses to deposit in the hollows. 
To overcome this, and to render the deposit uniform, the solution 
should be well charged with free cyanide ; the current must be of 
high tension (a Bunsen, for example), and the anode should be kept 
in motion during the first few moments. In this way very little 
trouble will be experienced from the causes referred to. It is im- 
portant, however, that insides of such embossed work should be very 
thoroughly scratch -brushed in the first instance ; indeed, as a mecha- 
nical assistant, the scratch -brush lathe is the gilder's best friend. 

8. Old Soluliona. — When a gold solution has been much used 
it acquires a dark colour, from being contaminated by impurities 
as beer from the scratch -brush lathe, &c., and in this condition 
IB likely to yield a deposit of a dull red-brown colour, which. 



MANAOEMBNT OF QGLD BATHS. 219 

while being favoiirable to oertain dassee of work which can bereadOj 
got at by the scratch -brush, is very objectionable to articles of jeweUeiy 
whioh are required to present a dear orange-yeUow colour in aU parts, 
indnding the interstioes and soldered joints which cannot be reached 
by the lathe-brash. When the solution is in this condition we hare 
found itadYantageous to evaporate it to dryness, then to re-dissdre it 
in hot distilled water, filter the solution when cold, and add a small 
proportion of free cyanide, finally making up the bath to about three- 
fourths of its original rolume. llie solution thus treated yidds a rery 
ridi colour in gilding. It is necessary to mention, however, that gold 
solutions which have been prepared by precipitating the g^ld from its 
chloride with ammonia should not be evaporated to dryness, since the 
explosive fulminate of gold may be present to some extent, which 
would render the operation hazardous. 

9. Management of Oold Bath$. — ^The colour of the gilding may be 
varied from a pale straw or lemon colour to a dark orange-red at the will 
of the operator ; thus, when the solution is cold, a pale lemon-coloured 
deposit will be obtained. If the bath be warm, a very small surface 
of anode exposed in the solution, and the article kept in brisk motion, 
the deposit will also be of a pale colour. If, on the other hand, there 
be a large excess of cyanide in the bath, a considerable surface of 
anode immersed and a strong current, the gilding will be of a dark 
red colour, approaching a brown tone, and the article, when scratch- 
brushed, will assume a rich orange-yellow colour, specially suited to 
oertain classes of work, as the insides of cream-ewers, giblets, &c., and 
diaSnsof various kinds. In order to obtain uniform results in any desired 
shade, when gilding a large number of articles of the same class, care 
must be exercised to keep the temperature of the bath uniform ; the 
anode surface immersed in the solution the same for each batch of 
work, consisting of an equal number of pieces of the same dimensions ; 
the battery current as uniform as possible, and, lastly, fresh additions 
of warm distilled water must be added frequently to the bath to make 
up for loss by evaporation. If these points be observed there will be 
no trouble in obtaining uniform results. It is scarody necessary to 
state that a large bulk of gilding solution will keep in an uniform 
condition for a longer period than a smaller quantity, since the effect 
of evaporation is less marked than in the latter case. 

10. Worn Anodet. — It is not advisable to employ anodes which have 
become ragged at the edges for gilding the insides of vessels, since 
particles of the metal are liable to be didodged during the gfilding 
ptDcees, and, falling to the bottom of the vessd, protect those parts 
upon which they drop from receiving the depodt ; indeed, the smaller 
ffmgments will sometimes become electro'soldered to the bottom of the 
vessel, causing some trouble to remove them. When the edges of an 



t20 NOTES ON OILDINO. 

anode are very ragged it is well to trim them with shean or a pair of 
sharp Boissors before usmg the anode for g^ding insides. The anode 
should always be formed into a cylinder, and not used as a flat plate 
for these purposes, otherwise the deposition will be irregular, and the 
hollow surfaces of chased or embossed work may not receive the 
deposit at all. 

1 1 . Defect* in Gilding. — When the gold becomes partially dissolved off 
portions of an article while in the gilding-bath, it generally indicates 
that there is too great an excess of cyanide in the solution. The same 
defect, however, may be caused by the current being too weak, the 
liquid poor in gold, too small a surface of anode in the solution, or 
by keeping the articles too briskly in motion in a bath containing a 
largB excess of cyanide. Before attempting an alteration of the solu- 
tion, the battery should be looked to, and, if necessary, its exciting 
liquids renewed. The solution should then be well stirred and tried 
again ; if the same defect is observed an addition of chloride of gold 
should be made to the bath to overcome the excess of cyanide. If the 
deposit is of a very dark red colour, and of a dull appearance, this 
may be caused by employing too strong a current, by excess of cyanide, 
or too g^reat a quantity of gold in the bath. If from the latter causes, 
the solution must be diluted ; if from the former, the articles should 
be suspended by a very thin slinging wire, or the positive element 
of the battery partially raised out of the battery-cell. 

12. Gilding Pewter Solder. — Gonmion jewellery is frequently repaired 
with pewter solder, which does not so readily take the g^ding as the 
other parts. A g;YX>d plan to overcome this is first to well scratch- 
brush the articles, after which the solder may be treated as follows : 
Make a weak acid solution of sulphate of copper, dip a camel-hair 
brush into the solution and apply it to the soldered joint, and at the 
same time touch the spot with a steel point ; in a few seconds the 
solder will become coated with a bright deposit of copper. Now rinse 
the article, and proceed to the gilding as usual, when it will be found 
that the soldered part upon which the film of copper has been deposited 
will readily receive a coating of gold, more readily, in fact, than the 
body of the article itself. The article, when gilt, is then scratch- 
brushed and treated as usual. The copper solution for the above 
purpose may be prepared by dissolving about \ oz. of sulphate of 
copper in \ pint of water, and adding to the solution about \ oz. of 
oil of vitriol. 

13. Gilding Cheap Jewellery. — ^This class of work, whether of French 
or Birmingham manufacture, seldom requires more than a mere dip to 
meet the requirements of the customer ; indeed, the prices obtainable 
for gilding articles of this character will not admit of gilding in the 
pioper sense of the term. In France it is usual to employ a platinum 



STRIPPING GOLD FROM SILVER* 221 

anode, and to renew the gilding solution as it becomes exhausted of 
its metal by fresh additions of gold salt. The author has found it a 
▼617 economical plan to use a copper anode for gilding work of this 
description, and by making small additions of chloride of gold when 
the bath exhibited signs of weakness, he has been able to gild a yeiy 
large number of articles, of a very fine colour, with an infinitesimal 
amount of the precious metal. The only preparation such work 
recelTed was a good scratch-brushiag before gilding, and a very 
slight scratch-brushing after. In his experience, although the prices 
weie very low, the result was exceedingly profitable. Against the 
employment of a copper anode, it has been argued that the solution 
must of necessity become highly impregnated with copper. To 
which we may reply that we did not find such to be the case in 
praotioe. 

14. OUding German Silver. — Since this alloy of copper, &c., will gene- 
rally receive a coating of g^ld in ordinary cyanide solution, without the 
aid of the battery, the solution should be somewhat weaker, and the 
battery current also, otherwise the gold will not firmly adhere. The 
temperature of the solution should also be lower than is required for 
gilding articles of silver or electro-plate. When German silver articles 
are first placed in the gilding-bath a small surface of anode only should 
be immersed, and the deposit allowed to take place gradttally. If these 
precautions be not observed the operator may suffer the annoyance of 
finding the work strip when the scratch-brush is applied, or at all 
events under the operation of burnishing. 

15. Stripping Gold from Silver. — This may be done by making the 
article the anode in a strong solution of cyanide of potassium, or in an 
old gold solution containing a moderate amount of free cyanide. A 
quicker process, however, consists in immersing the articles in strong 
nitric acid, to which a little dry common salt is added. Care must be 
taken not to allow the article to remain in the stripping solution one 
moment after the gold has been removed, and the articles should be 
moved about in the liquid, especially towards the close of the opera- 
tion, to facilitate the solution of the gold from the surface. The gold 
may afterwards be recovered from the exhausted acid bath by im- 
mersing in it several stout pieces of sheet zinc or iron, which will 
precipitate the gfold in the metallic state, and this may be collected, 
dried, and fused with a little dried carbonate of potash. Or the 
exhausted stripping solution may be evaporated to dryness, and the 
reeidnum fused with dried carbonate of potash or soda, a little nitre 
being added towards the end of the operation, to refine it more 
completely. 

16. Spuriotis Gold — ^^ Mystery Gold. ' ' — Many attempts have been made 
from time to time to form an alloy which, having somewhat the colour 



33a NOTES ON GILDING. 

of gold, would also withstand the action of the usual test for gold — 
nitric acid. The introduction of the electro-gilding art greatlf 
favoured such unscrupulous persons as desired to prey upon the publio 
by selling as gold electro-gilt articles, which had not a fraction of the 
predous metal in their composition. An alloy of this kind entered the 
market many years ago, in the form of watch-chains and other artlulea 
of jewellery, ^e composition of which was, copper i6 parts, platinum 
7 parts, and zinc i part. This alloy, when carefully prepared, beam 
a dose resemblance to i6-car^t gold, and when electro-gilt would 
readily pass for the genuine article. The manufacture of this yariety 
of spurious g^ld seems to have received a check for a certain period ; 
but somewhat recently, in a modified formula, it has reappeared, not 
only in the form of articles of jewellery, but actually as current coin, 
and from its highly deceptive character, being able to resist the usual 
test, it has acquired the name of ** Mystery Grold." It appears that, 
when converted into jewellery, the chief aim of the *^ manufacturers " 
is to defraud pawnbrokers, to whom the articles are offered in pledge ; 
and, since they readily withstand the nitric acid test, the *' tnmaao- 
tions " are often successful. According to Mr. W. F. Love, in a 
oommunication to the Chemical News, a bracelet made from an alloy of 
this character had been sold to a gentleman in Liverpool, and when 
the gilding was removed the aUoy presented the colour of 9-oarat 
gold. The qualitative analysis proved it to be composed of platinum, 
copper, and a little silver. A quantitative analysis yielded the following 
result: — 

Silver 2*48 

Platinum 32'02 

Copper (by difference) 65*50 

It was found that strong boiling nitric acid had apparently no effect 
upon it, even when kept in the acid for some time. 

17. Oilding Watch Dials. — To prepare a silver watch dial (for ex- 
ample) for gilding, it should be laid, face upward, upon a flat piece 
of cork, and the face then gently rubbed all over with powdered 
pumice, sifted through a piece of fine muslin, and slightly moistened 
with water, using the end of the third finger of the right hand for the 
purpose. The fing^ being dipped in the pumice paste, should be 
worked with a rotary motion over the surface of the dial, so as to pro- 
duce a perfectly imiform and soft dulness. When this is done, a 
piece of copper slinging wire is passed through the centre hole of 
the dial, and formed into a loop ; the dial is then to be rinsed, and 
placed in the bath, care being taken not to touch the face of the 
article either before or after g^ding, except in the way indicated. 
The dial must afterwards be repainted. 



SUNeiNO WIBES. 323 

18. Gilding aolutions which have been worked with but a small 
excess of cyanide are apt to deposit more gold than is dissolved from 
the anode, by which the action of the bath becomes lessened, while the 
colour of the gilding is indifferent. It must always be borne in mind 
that in all cyanide solutions, but more especially such as are worked 
hot, the cyanide of potassium gradually becomes converted into car- 
bonate of potassium by the action of the atmosphere, and therefore 
loses its solvent power. 

19. For producing a dead or matted surface upon brass articles of 
jewdlery, as brooches, lockets, &c., they are first dipped for an 
instant in a mixture composed of equal parts of sulphuric and nitric 
acids, to which a small quantity of common salt is added, and imme- 
diately plunged into cold water. After being rinsed in one or two 
other waters, they are promptly immersed in the gOding-bath, in 
which, after a moment's immendon, they acquire the desired colour of 
gold. After rinsing in hot water, they are finally dried in hot box- 
wood sawdust. In treating thii class of work, care should be taken 
to avoid handling the pieces ; after they have been removed from the 
sawdust they should be at once wrapped up ready for delivery. 

20. When it is desired to give a stout coating of gold to an article, 
it should be occasionally removed from the g^ding-bath, then scratch- 
brushed, rinsed, and returned to the bath. If the article were allowed 
to remain in the bath undisturbed imtil a thick coating was deposited, 
the surface would probably be rough and crystalline, and moreover 
liable to strip when being scratch-brushed. It is sometimes the prao- 
tioe to dip the article for an instant in the quicking solution after 
each gilding, by which the respective layers of gold are less apt to 
separate in scratch-brushing or burnishing. 

21. The wires used for slinging articlen in the gilding-bath should, 
never be reversed, but one end only employed for suspending the 
articles, the other being used for connection with the negative elec- 
trode of the battery. By adopting this system, the gold deposited 
upon the ends of the sling^g wires is less liable to become wasted 
than when both ends of the wires are used indiscriminately. After 
the slinging wires have been used a few times, and before the g^ld 
upon them begins to chip or peel off, they should be carefully laid 
aside, with all the gilt ends in one direction, so that the gold may 
be removed, by stripping, at any convenient time. After stripping off 
the gold, the wires should be annealed, then pulled out straight, and 
placed in bundles. Before being again used, each end of the bundle 
of wires should be dipped for a few moments in an old dipping- bath, 
and then rinsed, when they will be ready for future use. It is better to 
treat slinging-wires thus carefuUy than to suffer them — which is 
commonly the case — to be scattered about. 



224 NOTES ON aiLDlNO. 

22. Gilding Lead, Britannia Metal, <^r. — ^When artioleB oompoeed of 
lead, tin, Britannia metal, iron, or steel are required to be g^t, it ia 
best to give them a preliminary coating of copper in an alkaline bath, 
or to electro-brass them, after which they may be gilt with perfect 
ease, and with but little liability to strip when scratch-bnished. The 
softer metals, however, will require to be bnmiahed with great care, 
owing to their yielding nature under the pressure of the burnishing 
tools. The same observation also applies, inyersely, to silvered or 
gilt steel work, in which case the superior metals, being softer than 
steel, become expanded under the influence of the burnishing tools, 
and are consequently liable to become separated, in blisters, from the 
underlying harder metal. 

23. Excess of Cyanide Injurioits. — When a newly prejMured gilding 
solution is first used (hot), the deposit is usually of a rich, fine gold 
colour, if a sufficient quantity of free cyanide has been employed in 
its preparation, a proper surface of anode immersed in the solution, 
and the current brisk. If, on the other hand, the colour is pale — ^that 
is yellow, without the characteristic orange tint — this indicates that 
one or other of the above conditions is wanting. Before venturing 
to increase the amount of free cyanide, the condition of the battery 
should be examined, the temperature of the solution raised a littie, 
and a larger anode surface immersed, when, if the solution still yields 
a light-coloured deposit, an addition of strong cyanide solution must 
be given gradually until the gilding assumes the proper orang^e-yellow 
colour. The addition of cyanide must always be made with caution, 
for if too great an excess be applied, the solution is apt to jrield 
brown deposits, quite unsuitable for many articles of jewellery ware. 
This quality of gilding, however, is frequentiy taken advantage of 
for articles which are required lo have a deep g^ld colour after 
scratch-brushing, as the insides of tankards, &c., and also Albert 
chains and work of a similar description. If a gold solution is 
in really good working condition, and the current sufficiently brisk, a 
copper or brass article should gild readily, in hot solutions, with an 
anode surface considerably less than that of the cathode, or article 
being gilt, especially if no motion be given to either electrode. A 
silyer article, however, would require, in the same bath, a much larger 
surface of anode, but more especially if tiie surface were frosted, as in 
filigree work. In gilding articles of this description it is better to 
expose a large anode surface and keep the article in g^itie motion 
when first put into the bath, after which a portion of the anode 
may be withdrawn, and the object allowed to rest undisturbed until 
the coating is sufficiently thick. 

24. In working small baths, additions of hot distilled water must 
be given frequently to make up for the loss by evaporation ; but where 



DIS00L0T7SED SOLUTIONS. 22$ 

large qnantitieB of Bolution are employed, this addition need not be 
made more than onoe a daj, or at the close of the operation. With 
this exception, a good gilding solution will continue to give uniformly 
good results for many days — especially if large in bulk — ^without 
alteration. When it begins to work tardily, however, which may 
readily be seen by the extra anode surface required to gild the articles 
promptly, moderate additions of cyanide must be given until the bath 
acquires its normal activity. 

25. After working gfilding-baths for a lengthened period, they 
generally assume a brown colour, and the gilding is, under such 
circumstances, of an indifferent colour. The chief causes of this dis-- 
coloration have been already explained, and can be to a great extent 
avoided, by thoroughly rinsing the articles before putting them in 
the bath. When a solution is in this condition the best remedy is to 
evaporate it as before, and then redissolve the dried mass in distilled 
water, using about one -third less water than the original bulk. A 
littlo fresh cyanide must also be added, and the solution filtered, after 
which it will generally yield a deposit of excellent colour. Old solu- 
tions which give deposits of a greenish -black colour may be improved 
by evaporation, but the heating of the dried product should be carried 
somewhat farther than in the former cases. It is better, however, to 
abandon such a solution altogether and to make a fresh one. The gold 
from the waste solution may afterwards be recovered by the processes 
given in another chapter. When gilding solutions, after being worked 
some time, yield a pale straw-coloured gilding, this is attributed by 
some to the gradual accumulation of silver from the gold anodes 
(which always contain a trace of silver) ; we are, however, disinclined 
to accept this view, owing to the exceedingly small quantity of silver 
present in fine gold ; moreover, since silver deposits first, if present 
in a gold solution, we doubt its liability to accumulate in the bath. 
We would rather attribute the paleness of deposit referred to, to one 
or both of the following causes : — I . To the presence of a large excess 
of carbonate of potash in the bath from using an inferior cyanide ; 
2. To the presence of tin derived from pewter soldered articles, imper- 
fectly prepared for gilding. 

26. The Bunsen battery is most generally used for gilding, and 
indeed the current from this source produces a gold deposit of very 
fine colour. It must be used with caution, however, when gilding 
articles at a low price, since it deposits the metal very freely from hot 
solutions, and would soon yield a coating of gold of greater thickness 
than would pay for ordinary cheap work. In gilding with this 
battery, the regnil&tion of the anode surface in solution should bo 
Btrictiy observed, only a sufficient surface being exposed to enable the 
article to become gilt almost immediately after immersion ; the anode 



236 N0TB8 ON OILDINd^. 

may be gradually lowered a little as the deposition progresses. Articles 
tliat only reqxiire to receive a mere colour of gold upon them (as in 
cheap jewellery) should be first scratch -brushed, then well rinsed in 
hot water ; dipped for a moment in the gold bath, then rinsed, and 
lightly scratch-brushed ag^in, and after again rinsing receive a 
momentary dip in the g^ding bath ; they are to be finally rinsed in 
boiling water, then shaken well, and placed in hot boxwood sawdust, 
from which they are afterwards removed and well shaken to deanse 
them from this material. 



CHAPTER XIV. 

ELECTRO -DEPOSITION OF SILVER. 

Preparation of Nitrate of Silver.— Observations on Commercial C3*anide.— 
Preparation of Silver Solutions. — Bright Plating. — Deposition by Simple 
Immersion. — Whitening Articles by Simple Immersion.— Whitening 
Brass Clock Dials, &e. 

The process of ** electro-plating " may be considered the most impor- 
tant branch of the great art of electro-deposition. Not only is it 
invaluable in giving to articles manufactured from German silver, 
Britannia metal, and other metallic surfaces, a beautifully white 
coating of the precious metal even superior in brilliancy to that of 
standard silver, but old plated and electro -silvered articles, from which 
the silver has worn off, may be resilvered by this process and miade 
to look nearly equal to new, which there was no practical means of 
doing before the introduction of electro-plating. This term, by-the- 
bye, though generally used, is erroneous, since the process of plating 
consists in attaching two plates, or ingots of metal, and rolling them 
into sheets, from which, as in the old manufacture of Sheffield plate, 
various articles of utility are, or rather were, made. 

TxmpBxation of Hltrato of 811y«r. — Since the silvering or ** plat- 
ing *' solutions — with one exception — are prepared from the nitrate of 
silver, it will be necessary to consider its preparation previous to 
explaining the various ways in which silver baths are made up from 
this salt of silver. To prepare nitrate of silver, the required quantity 
of grain silver is carefully put into a glass flask * or evaporating dish, 
the former by preference, since during the chemical action which 
ensues while the solution of the metal is taking place, a portion of the 
metal may be lost by the spitting of the solution when the chemical 
action is at its height. In dissolving silver, take, say — 

Grain silver 2 ounces. 

Pure nitric acid 3i •? 

Distilled or rain water ^h n 

* When dissolving large quantities of silver, a stoneware vessel may be 
•mploved. 



228 eLEGTRO-DSPOSmOM OP STLVEB. 

Put the silver carefnlly into the flask, then add the water, and lastly 
the acid. In a few moments vigorous ebullition takes place, with the 
disengagement of red fumes of nitrous gas, which should be allowed 
to escape through the chimney. When the action begrins to quiet 
down a little, the flask must be placed on a warm sand-bath. For 
small operations, or where a proper sand-bath is not provided, an 
ordinary frying-pan nearly half-fllled with silver-sand will answer 
the purpose well. The flask should remain upon the sand-bath until 
the red fumes cease to appear in the bulb, at which period the chemical 
action is at an end. It may be well to mention that, in dissolving 
silver, it is advisable in the first instance to use rather less of the acid 
than is necessary to dissolve the whole of the silver, and to treat the 
imdii!UK)lved portion separately, by which means excess of acid is 
avoided. The nitrate of silver solution must now be decanted into an 
evaporating dish and placed in the sand-bath, where it is allowed to 
remain until a film or pellicle forms on the surface of the liquor, when 
the vessel must be set aside to cool. A few hours after, crystals of 
nitrate of silver will have deposited, from which the remaining liquor 
is to be poured off, and this again evaporated as before. Instead of 
crystallising the nitrate, it may simply be evaporated to nearly dry- 
ness, by which the free acid will become expelled. 

Should the nitric acid used in dissolving silver contain even a slight 
portion of hydrochloric acid, an insoluble white precipitate will be 
found at the bottom of the flask, which is chloride of silver. This, 
however, will not be injurious to the plating solution. Sometimes, 
also, a slight deposit of a brownish -black colour is found at the 
bottom of the vessel in which silver is dissolved ; this is goMy left in 
the grain silver through imperfect parting in the refining process. We 
have occasionally discovered more than a mere trace of gold at the 
bottom of the dissolving flask ; indeed in several instances an appre- 
ciable quantity. 

When dissolving the crystals of nitrat-e of silver, for the preparation 
of either of tlie following plating solutions, distilled or rain water 
only should be used, since river water always contains traces of sub- 
stances which form a white precipitate in the presence of nitrate of 
silver. 

In describing the silver solutions, the proportion of silver in the 
metallic state will be given, and it will be understood that in each case 
the weighed metal must be first converted into nitrate. We may also 
state that the proportion of silver to each gallon of solution may be 
varied according to the practice of the plater, some persons preferring 
solutions in which there is a moderate percentage of the metal, while 
others employ much greater quantities. The proportion of silver per 
gallon of solution ranges from ^ an ounce to 5 or 6 ounces, and even 



COMMSBOIAL OTAMIDB OF POTASSnTM. 22^ 

more ; but for moHt practical purposes fTom i^ to 2 otinccs will be 
quite sufficient ; indeed, some of our best results haye been obtained 
with I ounce of silver per gallon. 

In most of the formulae given, i gallon of solution will be taken as 
the basis for making up any required quantity of silvering bath ; and 
it will be readily understood that when larger proportions of silver to 
the gallon are preferred, a proportionate increase of cyanide must be 
used, not only to dissolve the precipitated metal, but also to play the part 
of free cyanide in the solution. It must be remarked here, that unless 
the silvering-bath contains an excess of cyanide of potassium, the 
anode, or dissolving plate^ whose function it is to resupply the solution 
with silver in the proportion in which it is deposited upon the articles, 
will not keep up the metallic strength of the bath, and consequently it 
will deposit the metal slowly. A large excess of cyanide, on the other 
hand, is not only unnecessary, but is liable to cause the deposited 
silver to blister and strip, or peel off the work under the pressure of 
the burnishing tools ; and when very greatly in excess, the coating 
will be so non-adherent that it may even yield to the scratch -brush, 
and separate from the underlying metal. 

ObMrratioiui on ComiiMreial Osranida of Pota—ltiin. — Since 
the cyanide of potassium is one of the most important and useful sub- 
stances that come under the command of the electro-depositor, while 
the success of his operations greatly depends upon its active quality, it is 
advisable to state that ordinary commercial cyanide varies considerably 
in thid property ; so much so, indeed, as to render it absolutely neces- 
sary that the user should be put on his guard, lest in purchasing a 
cheap and worthless article, he should commit an error which may 
cost him much trouble and annoyance, as also pecuniary loss. Before 
making up any solution in larg« quantity, in which cyanide of potas- 
sium is the solvent, we advise him first to obtain samples of the com- 
mercial article, and to test them by either of the processes given in 
another chapter.* We may state that some of the cheap cyanides con- 
tain a larg^ excess of carbonate of potash. This substance, while 
being a necessary ing^redient in the manufacture, is also frequently 
used greatly in excess to produce a cheap article, and may be called 
its natural adulterant. This salt (carbonate of potash), however, 
unless specifically recommended in the preparation of certain depositing 
solutions, is not only useless, but when greatly in excess reduces the 
conductivity of both silvering and gilding baths. 

Prsparatlon of SllT«r Solntloiui. — Solution I. The solutions of 
silver most generally used for electro-plating are those commonly 
oaUed *' cyanide solutions,'* the foremost of which is the dottble cyanuie 
of silver and potassium, which is prepared as follows : i ounce of silver 
is oonverted into nitrate, as previously described, and the crystals dis- 



* See P.43Z-, eiseq. 



23O ELECTRO-DEPOSITION OF SILVES. 

solved, with stirring, in about 2 quarts of distiUed or rain water, which 
may, in the case of small quantities, be effected in a glass vessel or 
glazed earthenware pan. For large quantities a stoneware vessel 
should be used. When the orystals are all dissolved, a strong solution 
of cyanide (about } a pound, dissolved in i quart of water) is added, 
a little at a time, when a precipitate of cyanide of silver will be formed, 
which will inorease in bulk upon each addition of the cyanide. Each 
time, after adding the cyanide solution, the mixture must be weU 
stirred with a glass rod or strip of wood free from resin. When it is 
found that the addition of cyanide produces but little effect, it must 
be added very eautiouelyy since an excess will redissolve the precipitate, 
and cause waste in the after process of washing this deposit. To 
avoid adding too much cyanide, the precipitate should be allowed to 
fall down an inch or so, when a glass rod may be dipped in the cyanide 
solution, and the clear liquor touched with this, when if a milkiness 
is produced, a little more C3ranide must be added, and the stirring 
resumed. After a short repose, the same test may be appHed, and so 
on, until a drop of cyanide solution produces no effect. Grreat care 
must be taken not to add more cyanide than is absolutely necessary to 
throw down the silver. As an additional precaution, when nearly 
the whole of the silver is precipitated, the vessel may be allowed to 
rest for an hour or so, and the clear liquor then poured off and treated 
separately, by which means the bulk of the precipitate will be saved 
from the risk of coming in contact with an excess of cyanide. If, 
through accident or faulty manipulation, too much cyanide has been 
added, more nitrate of silver solution must be poured in, which, com- 
bining- with the surplus cyanide, will again produce the characteristic 
milkiness ; and if the additions of nitrate are made with care, the 
clear liquor will be perfectly free from silver, and after allowing the 
cyanide of silver to deposit, may be poured off and thrown away. 

Wathing ike Precipitate, — In all such cases the precipitate should be 
allowed f uUy to settle; the supernatant liquor, or "mother liquor,*' 
is next to be poured off slowly, so as not to disturb the soUd matter 
(cyanide of silver) y a large quantity of fresh water— which for this 
purpose may be common drinking wat^ — is now to be poured on to 
the precipitate with brisk stirring, and the vessel again left to rest, 
after whbh the clear liquor is to be poured off as before, these washing t 
being repeated three or four times. 

Dissolving the Precipitate. — ^To convert the cyanide of silver into the 
double cyanide of silver and potassium, the strong solution of cyanide 
must be added in moderate portions at a time, constantly stirring as 
before, until the precipitate appears nearly all dissolved, at which 
period the additions of cyanide must be made with more caution. In 
this case^ as in the fonder, it is a good plan, when nearly the whole 




PREPABATION OF SILVEB SOLUTIONS. 33 1 

of the precipitate is disflolved, to allow the yesflel to stand for a short 
time, then to pour off the clear liquor — which is now a solution of the 
double cyanide of silver and potassium— and to treat the remainder of 
the precipitate with cyanide solution ; by this means too great an 
excess of the solvent is avoided. When aU the precipitated silver is 
lediBsolved, add about one-fourth more cyanide 
solution than that originally used, and pass the 
solution through a filter into the plating vat or 
depositing vessel, which may be conveniently 
done by means of a piece of unbleached calico 
(previously washed in lokewaxm water to 
remove the *' dressing ") stretched over three 
strips of wood bound together in the form of Fig. 79. 

a triangle either with copper wire or string, 
as in Fig. 79. When all the solution has passed through the filter, 
this may be washed by pouring a little vrater over it while resting 
over the bath. The solution is finally to be made up to the full quan- 
tity by adding the necessary proportion of water, when its preparation 
is complete ; it will be better, however, to allow it to rest for twenty- 
fotir hours before using it for electro-plating. 

Fre% Cyanide, — ^This term is applied, as we have before hinted, to a 
moderate excess of cyimide of potassium which it is always necessary 
to have in the bath, to dissolve the insoluble cyanide of silver which 
forms on the anode, but since the ordinary commercial article is of 
very variable quality, the addition of this substance must to a great 
extent depend upon the judgment of the plater, subject to the precau- 
tions we have previously given ; from one-fourth to one-half the quan- 
tity of cyanide used in dissolving the precipitate of cyanide of silver may 
be added to the solution as free cyanide, and water then added to make 
up I gallon. If the cyanide, in the first instance, be dissolved in a 
definite measured quantity of water, say at the rate of half a pound to 
a quart of water (40 ounces), the proix>rtion of cyanide used in each of 
the former cases can be readily ascertained by simply measuring the 
balance of the solution and deducting its proportion of cyanide from 
the original weight taken. A fair quality of ordinary commercial 
cyanide should not contain less than 50 per cent, of pure cyanide, but 
we have frequentiy met with an article which contains a very much 
lower percentagfe, which should never be used for making up plating 
solutions, but maybe employed in the less important process of dipping 
in the preparation of work for nickel-plating. Of course it will be 
understood that when cyanide containing a high percentage of the pure 
substance is obtained, a proportionately smaller quantity must be used. 

Solution II. — One ounce or more of silver is converted into nitrate 
fw beforo, and the crystals dissolved in from three to four pints of di^- 



23 a BUECmO-DBPOSmON OF BILVBR. 

tilled water. A solution of carbonate of potash (salt of tartar), oon* 
sisting of about six or eight ounces of the salt to a pint of water, is to 
be gradually added to the solution of nitrate of silver, with constant 
stirring, until no further precipitation takes place. After settling, 
the clear liquor is poured off, and the precipitate (carbonate of ailrer) 
washed with water several times, as before directed. A strong solu- 
tion of cyanide is then to be added until all the precipitate is thoroughly 
dissolved, when a moderate excess is to be added as free cyanide. 
The solution should now be filtered and water added to make up one 
gallon, or such quantity in the same proportion of materials as may be 
required. In adding excess of cyanide to this and other solutions, it 
is always preferable to add it moderately at first, otherwise the work 
is very liable to strip. After working the bath for some time, an 
addition of cyanide may be made, but so long as the anode keeps 
perfectly clean while the work is being plated, the less free cyanide 
there is in the bath the better. A solution which has been worked 
for a considerable time acquires a good deal of organic matter, becom- 
ing dark in colour in consequence, and is then capable of bearing, 
without injury to the work, a larger proportion of free cyanide than 
newly prepared solutions. 

Solution III, — ^Mr. Alexander Parkes, in 187 1, patented a solution 
for depositing solid articles. One ounce of silver is first converted 
into nitrate, from which the silver is thrown down in the form of 
oxide of silver, by means of a solution of caustic potash gradually 
added, imtil no further precipitation takes place. After washing the 
oxide, it is dissolved in 2 gallons of water containing 16 ounces of 
cyanide of potas.<dum. 

Solution IV, — ^The best solution for depositing sQver upon Gkrman 
silver without recourse to the process of '* quicking,** is one which the 
author employed upon an extensive scale for many years with great 
success ; it is composed as follows, and although it is rather more 
expensive in its preparation than many other solutions, it is, so far as 
he is aware, the best solution in which German silver work may be 
plated without being pr^ously coated with mercury, as in the 
♦* quicking " process hereafter referred to. To prepare the solution, 
I ounce of silver is converted into nitrate and dissolved in two or three 
pints of distilled water as before. About three ounces of iodide of 
potassium are next to be dissolved in about half a pint of distilled 
water. The iodide solution is to be gradually added to the nitrate 
solution, the operation being performed in a dark comer of the 
room, or preferably by feeble gaslight, when a bright lemon yellow 
precipitate will be formed. The liquid must be briskly stirred 
upon each addition of the iodide, and care must be taken not 
to add the latter salt on any account in excess, otherwise it will 



FBEPABATION OF SILVER SOLUTIONS. 333 

rediflsolTe ihe praoipitate. When the precipitation is nearly oom- 
pletCi it is better to allow the vesflel to rest, and to put a little of the 
dear liquor in a test tube, Fig. 80, and to add a drop or two of the 
iodide solution, whdn if a cloudiness is produced, a moderate 
quantity of the iodide is to be added to the bulk and weU ^ 
stirred in. The clear liquor should be repeatedly tested in this 
way, until a single drop of the iodide solution produces no 
further effect upon it. In case of an accidental addition of 
too much iodide, nitrate of silver solution must be added to 
neutralise it. When the precipitation is complete, the yessel 
must be set aside — ^in a dark place, since the iodide of silver is  1 
affected by light — ^for an hour or so, after which the clear li 
liquor must be poured off, and the precipitate repeatedly pjggo, 
washed with cold water. Lastly, the iodide of silver is to be 
dissolved in a solution of cyanide of potassium, and a moderate exoees 
added as before recommended. In working this solution, whenever 
the anode becomes coated with a greenish film, an addition of cyanide 
must be made to the bath. 

Since the system of working the above solution differs in several 
respects from that adopted with other solutions, it may be well to 
describe our own practice in the treatment of G^eiman silver work. 
The articles are first placed in a warm solution of caustic potash, to 
remove greasy matter, after which they are well rinsed. Each article 
is then well scoured all over with powdered pumice and water, or 
finely powdered bath brick — an excellent substitute for the former — 
and water. As each artide is brushed, it is to be well rinsed in clean 
water, and is then ready for the plating bath, in which it should be 
suspended without delay. 

Solution V. — ^Mr. Tuck obtained a patent, in 1842, for ^' improve- 
ments in depositing silver upon German silver,** in which he recom- 
mends, for plating inferior qualities of Ckrman silver, a liquid com- 
posed of atUphats of aiher dissolved in a solution of carbonate of 
ammonia. Sulphate of silver is formed by adding ^ solution of 
sulphate of soda (Glauber's salt) to a solution of nitrate of silver, or 
by boiling silver with its weight of sulphuric acid. For plating the 
better qualities of G^erman silver, cyanide of silver is dissolved in a 
solution of carbonate of ammonia. The proportions used are : — 

Sulphate of silver 156 parts. 

Carbonate of ammonia (dissoWed in distilled water) . 70 „ 

Or, 

Cyanide of silver ^34 yt 

Carbonate of ammonia 70 ,, 



254 



BUSGTBO-DBFOBrnON OF BILyBB. 



The silTer salt in each case is boiled with the solution of the osr- 
bonate of ammonia until it is dissolved. For ooating common Grennan 
silver, he adds half an ounce of sulphate of silver to a solution con- 
taining 107 grains of bicarbonate of anunonia. 

Solution VI. — ^For producing very- white deposits of silver, the 
following may be used : — One ounce of silver is dissolved and treated 
as before, and the orystalB of nitrate rediseolved ia about half a gallon 
of distilled water. A moderately strong solution of common salt is 
then prepared, and this is gradually added to the former, when a 
copious white precipitate of chloride of silver is formed, which must be 
well washed with cold water. After pouring off the last wash water, 
a strong solution of cyanide is to be added to the precipitate until it is 
all dissolved, when a moderate excess is to be added, and the solution 
carefully filtered through filtering paper, the first runnings to be 
passed at least twice through the same filter. Lastiy, add water to 
make up i g^on. The solution may be used immediately, but will 
work better after a few hours* rest. This solution is veiy useful for 
obtaining delicately white deposits, but is not suitable for ordinary 
plating purposes, since the deposited silver is liable to strip under the 
action of the bumifiher. If used somewhat weaker than in the above 
proportions, with a moderate current and small anode surface, the 
deposit will adhere to most metals with tolerable firmness ; it is, how- 
ever, most suitable for coating articles which are either to be merely 
scratch-brushed or left a dead white. Chased figfures and cast metal 
work receive a brilliant white coating in this solution, but to retain 
their beauty they must be kept beneath a glass case, since the fine 
silver surface soon discolours in the atmosphere. 

Solution VII. — ^This plating solution, which is one of the best for 
most; purposes, is prepared by dissolving tdlver in a solution of cyanide, 

by aid of the electric cur- 



rent. Suppose we wish the 

solution to contain i ounce 

of silver per g^on. The 

required quantity of water 

is first put into the bath, 

and for each gallon of 

liquid about 3 ounces of 

g^ood cyanide is added, 

and allowed to dissolve. 

A porous cell is now to be 

nearly filled with this 

solution, and stood upright in the vessel containing the bulk of 

cyanide solution, the liquid being at the same height in both vessels. 

A fitarip of sheet copper is next to be connected to the negative 




Fig. 81. 



FREPABATIOK OF SILVER SOLUTIONS. 235 

electrode of a strong yoltaic battery, and placed in the porouB cell. 
A large sheet of silver is next to be connected to the positiTe elec- 
trode, and immersed in the larger vessel. The arrangement is shown 
in Fig. 81. The weight of the sheet silver being ascertained before- 
hand, the battery is allowed to remain in action for several hours, 
when the silver plate may be weighed to determine how much of it 
has been dissolved in the solution, and the action is to be kept up 
until the proper proportion has been dissolved by the cyanide in the 
outer vessel. When this point has been reached tiie porous cell is to 
be removed, and its contents may be thrown away. 

Another electrolytic method of preparing a silver bath is the follow- 
ing : — ^To make a bath containing, say, one ounce of silver per gallon, 
the cyanide should be of known strength. Assuming the commercial 
article to contain 50 per cent, of real cyanide, about 3 ounces are to 
be dissolved in each gallon of water ; a larg^ silver anode connected 
to the positive pole of a battery is to be suspended in the solution, 
and a smaller plate of silver as a cathode. A strong current should 
be used, and the anode weighed from time to time until the desired 
proportion of silver has become dissolved into the solution. The con- 
dition of the bath may then be tested by suspending a clean plate of 
brass from the negative rod, at the same time immersing about an 
equal surface of anode, using a moderate current, when if the solu- 
tion be in good working order, the cathode will at once receive a 
bright deposit of silver. During the action some caustic potassa is 
formed in the liquid, which may be converted into cyanide, by 
adding a moderate quantity of hydrocyanic acid, which must be done, 
however, with exceeding care, owing to the deadly nature of the acid, 
the vapour of which must not on any account be inhaled. Respecting 
the use of this acid, however, we must strongly recommend that its em- 
ployment should never, under any circumstances whatever, be placed in 
the hands of persons unacquainted with its highly poisonous character. 

Besides the foregoing, many other processes for preparing silver 
solutions have been proposed ; but since they are comparatively of 
littie or no practical value, they deserve but a passing reference. By 
one of these processes ohloride of silver is dissolved in hyposulphite of 
soda. The salt of silver thus formed {hyposulphite of Hirer) is readily 
acted upon by light, and the silver, being thus converted into an 
insoluble sulphide, gradually becomes deposited at the bottom of the 
bath. Solutions have also been prepared by employing ferrocyanide 
of potassium (yellow prussiate of potash) as the solvent of cyanide of 
silver. Again, the silver has been precipitated from its nitrate solu- 
tion by lime-water, forming oxide of silver ; as also by ammonia, 
rada, magnesia, &c. : the various pr^ipitates being subsequentiy dis- 
solved in a solution of cyanide of potassium. The ordmaiy double 



236 ELBCTBO-DEFOSITION OF SILYSB. 

cyanide of sUrer and potafisium solution, however, will be found most 
useful for the gfeneral purposes of electro-plating. 

Brislit Plating. — ^The silver deposited from ordinary cyanide solu- 
tions is of a pearly white or dull white, according to the condition and 
nature of the silver solution, and the strength of the current ; and it 
is necessary to brighten the work by scratch-brushing before it is 
subjected to the operations of burnishing or polishing. It is possible, 
however, by adding to the plating-bath a small quantity of bisulphide 
of carbon^ to obtain deposits of silver which are bright instead of dull, 
for the discovery of which important improvement we are indebted to 
Mr. W. Milward, of Birmingham, who made the discovery in the fol- 
lowing way : — He had observed that when wax moulds for electro- 
typing, which had been coated with a film of phosphorus by applying 
a solution of that substance in bisulphide of carbon, were put into the 
o}ranide plating solution to receive a deposit of silver, that other 
articles — as spoons and forks, for example — silvered in the same solu- 
tion, assumed a brightness more or less uniform, sometimes extending 
all over the articles, and at others occurring in streaks and patches. 
This led him to try the effect of adding bisulphide of carbon alone to 
the plating solution, which produced very satisfactory results. The 
improvement was worked as a secret for some time, but eventually 
leaked out, in consequence of which Mr. Milward and a person named 
Lyons (who had become acquainted with the secret) took out a patent 
in March, 1847, for bright silver deposition by adding ''compounds 
of sulphur and carbon,*' bisulphide of carbon being preferred. From 
that time the bisulphide of carbon has been constantiy employed 
for producing bright deposits of silver. 

To make up the solution for ''bright plating," the following 
methods are adopted: i. "6 ounces of bisulphide of carbon are put 
into a stoppered bottie, and i gallon of the usual plating solution 
added to it ; the mixture is first to be well shaken, and then set aside 
for 24 hours. 2 ounces of the resulting solution are then added to 
every 20 gallons of ordinary plating solution in the vat, and the whole 
stirred together ; this proportion must be added every day, on account 
of the loss by evaporation, but where the mixture has been made 
several days, less than this may be used at a time. This proportion 
gives a bright deposit, but by adding a larger amount a dead surface 
may bo obtained, very different to the ordinary dead surface." 

Another method of preparing a solution for bright plating is the 
following : — Put i quart of ordinary silver plating solution into a 
large stoppered bottle ; now add I pint of strong solution of cyanide 
and shake well ; 4 ounces of bisulphide of carbon are then to be added, 
as also 2 or 3 oimces of liquid ammonia, and the bottle again well 
shaken, which operation must be I'cpeated every two or three hours, 



BRIGHT FL/LTING. 2^J 

The solution is then set aside to rest for about 24 hours, when it 
Trill be ready for use. About 2 ounces of the clear liquid may be 
added to every 20 gallons of ordinary plating solution, and well mixed 
by stirring. A small quantity of the brightening solution, or '* bright,'* 
as it is termed in the plating-room, may be added to the solution 
every day, and the liquid then gently stirred. In course of time the 
bisulphide solution acquires a black colour, to modify which a quantity 
of strong cyanide solution, equal to the brightening liquor which has 
been removed from the bottle, should be added each time. In adding 
the bisulphide solution to the plating bath an exoees must be avoided, 
otherwise the latter will be spoilt. Small doses repeated at intervals 
is the safer procedure, and less risky than the application of larger 
quantities, which may ruin the bath • 

A very simple way to prepare the brightening solution is to put 
from 2 to 3 ounces of bisulphide of carbon in an ordinary " Winches- 
ter " bottle, which holds rather more than half a gallon. Now add 
to this about 3 pints of old silver solution, and shako the bottle well 
for a minute or so ; lastly, nearly fill the bottle with a strong solution 
of cyanide, shake well as before, and set aside for at least 24 hours. 
Add about 2 ounces (not more) of the ** bright*' liquor, without 
shaking the bottle, to each 20 g^ons of solution in the plating vat. 
Even at the risk of a little loss from evai>oration, it is beet to add the 
brightening liquor to the bath the last thing in the evening, when 
the solution should be weU stirred so as to thoroughly diffuse the 
added liquor. The night's repose will leave the bath in good working 
order for the following morning. 

Other substances besides the bisulphide of carbon have been used, 
or rather recommended, for producing a bright deposit of silver, but 
up to the present no really successful substitute has been practically 
adopted. Amongst other compounds which have been suggested, arc 
a solution of iodine and gutta-jiercha in chloroform, which is said to 
have a more permanent effect than the bisulphide ; carbonate, and acid 
carbonate of potassium, i^ ounce of each, added once every nine or 
ten daya to a plating solution containing 12 ounces of cyanide and 
3^ ounces of silver per g^allon. According to Plante, bright silver 
deposits may be obtained by adding a little sulphide of silver to the 
plating solution. 

Although the solution for '* bright plating " is useful for some pur- 
poses, it is not adopted as a substitute for the ordinary cyanide of 
silver bath for the general purposes of electro-plating. For articles 
which have deep hollows and interstices which cannot be burnished 
without considerable difficulty, and for the insidcs of tea and coffee- 
pots, and articles of a similar description, which are required to be 
bright, but which cannot be rendered so by mechanical methods, a 



238 ELEGTBO-DSPOBinON OF SILVEB. 

slight coating of bright silver is an advantage. A bath of brightening 
solution is usually kept for this purpose, in which the articles, after 
being plated in the ordinary way, are immersed for a short time, by 
which they receive a superficial coating of the bright deposit. In the 
'* bright solution'* the articles first become bright at their lower 
surface, the effect gradually spreading upward, until in a short 
time they become bright all over, when they are removed from the 
bath and immediately immersed in boiling water, otherwise the silver 
would quickly assume a dark colour. 

B^poiitloa toy Blmpto XmaMiVBlon. — Articles of brass and copper 
readily become coated with a film of silver, without the aid of the 
battery current, in tolerably strong solutions of the double cyanide of 
silver and potassium ; the deposit, however, is not of such a degree of 
whiteness as to be of any practical use. Other solutions of silver are 
therefore employed when it is desired to give a slight coating of this 
metal to small brass or copper work which will present the necessary 
brilliant white colour. Silver may also be deposited upon these 
surfaces by means of a paste of chloride of silver, to which common 
salt or cream of tartar is added. The following processes are those 
most generally adopted : — 

^Tliitenlns JkrtLeHbm Xny Slinpl* Tmnmralon, — For small brass 
and copper articles, as buttons, hooks and eyes, cofBn-nails, &c., 
silvering by simple immersion is employed ; and in order to produce 
the best possible effect, the solution bath should not only be prepared 
with care, but kept as free as possible from contamination by other 
substances. To prepare a bath for this purpose, a given quantity of 
fine grain silver is dissolved in nitric acid. The solution of nitrate of 
silver thus formed is added to a large quantity of water, a strong 
solution of common salt is then poured in, which precipitates chloride 
of silver in the form of a dense white precipitate. When the whole 
of the silver is thrown down (which may be ascertained by adding a 
drop or two of hydrochloric acid or solution of salt to the clear liquor) 
the precipitate is allowed to subside, after which the supernatant 
liquor is to be poured off, and the precipitate washed several times. 
The last rinsing water should be tested with litmus paper, when, if 
there be the least trace of acid, further washing must be given. The 
precipitate, which is very readily acted upon by sunlight, should be 
prepared in a dull light, or by gaslight, and, if not required for imme- 
diate use, it should be bottled and kept in a dark cupboard. The 
chloride of silver is to be mixed with at least an equal weight of bi- 
tartrate of potassa (cream of tartar), and only sufficient water added 
to form a pasty mass of the consistency of cream. In this mixture 
the articles, having been previously cleaned or dipped f are immersed, 
and stirred about until they are suf&ciently white, when they are to 



WHITENIMO ARTIOLBB BT SIMPLE XSIMEB8I0N. 239 

be rinBed in hot water, and shaken up with boxwood sawdust. These 
preparations are also used for silvering olock -faces, thermometer and 
barometer scales, and other brass and copper articles, by being rubbed 
over the surface to be whitened with a cork. 

Anotiier chloride of silver paste, for whitening articles of brass or 
copper, may be made by taking chloride of silver and prepared chalk, 
of each one part, common salt i} part, and pearlash 3 parts, made 
into a paste, as before. A third mixture is prepared by taking 
chloride of silver i part, cream of tartar at least 80 parts, to which is 
sometimes added about 80 parts of common salt. The whole are 
dissolved in boiling water. This solution acquires a greenish tint, 
from the presence of copper, which takes the place of the silver in the 
liquid. In using this solution the articles are introduced by means of 
a perforated basket, which is briskly stirred about in the hot liquid 
until unifonnly white. Some operators modify the above solution by 
adding common salt, Glauber's salt, corrosive sublimate, caustic lime, 
&c., but it is doubtful whether any advantage is derived therefrom. 

A process, which is to be applied cold, was proposed by Boseleur. 
and seems to have worked exceedingly well in his experienced hands. 
A solution of the double sulphite of silver is formed in the following 
way : Four parts of soda crystals are dissolved in five parts of distilled 
water, sulphurous acid gas (prepajfed by heating in a glass retort 
strong oil of vitriol witii some small pieces of copper wire) is then 
passed through the liquid, by allowing it to bubble through mercuiy 
at the bottom of the vessel, to prevent the exit tube from becoming 
clogged with crystals; the ghs is allowed to pass until tiie fluid 
re-dissolves the crystals of bicarbonate, and slightiy reddens blue 
litmus paper. It is then allowed to repose for twenty -four hours, so 
that some of the bisulphite of sodium formed may crystallise. The 
liquid portion is then to be poured off, and stirred briskly to expel the 
carbonic acid. If alkaline to test paper, more sulphuric acid gtL8 
must be added ; or if acid, a littie more carbonate of soda. After well 
stirring, the solution should only turn blue litmus paper violet, or at 
most slightiy red. A solution of nitrate of silver is now to be added 
to the above liquid, with stirring, until the precipitate at first produced 
begins to dissolve slowly, when the bath is ready for use. The solution 
thus prepared is said to be always ready for work, and " produces, 
quite instantaneously, a magnificent silvering upon copper, bronze, or 
brass articles which have been thoroughly cleansed, and passed through 
a weak solution of nitrate of binoxide of mercury, although this is 
not absolutely necessary.'' To keep up the strength of the bath fresh 
additions of nitrate of silver must be made from time to time, and 
after awhile some bisulphite of soda must also be added. In working 
this bath the solution is placed in a copper vessel, which also receives 



t40 ELS0TBO-DBP08ITION OF SILVBB. 

a deposit of silver. Boselenr states that he used this bath for &ve 
years, during whioh period he daily silvered ** as many articles as a 
man could conveniently carry/' He also states that, without the aid 
of a separate current, the deposit from this solution may become nearly 
as thick as desired, and in direct ratio to the time of immersion. 

'Whltenlns Brass dock-IMalSy Ac, witli tlis Vasts. — For this 
purpose chloride of silver and cream of tartar, with or without the 
addition of common salt, is made into a paste, as before described, and 
this should be well triturated in a mortar until it is impalpable to the 
touch. The paste is then spread, a little at a time, upon the brass 
surface — which may be a clock-face or thermometer-scale, for instance 
— and rubbed upon the metal surface with a piece of soft cork, or 
** velvet " cork as it is called. By thus working the silver paste over 
the metal it soon becomes silvered, and a coating of sufficient thickness 
for its purpose obtained in a very short time, according to the size of 
the object. When the silvering is complete the article is to be rinsed 
and dried in the hot sawdust. Although a very slight film of silver 
only is obtained in this way, its somewhat dull tone is specially ap- 
plicable to barometer and galvanometer scales, cl<)ck-dials, and objects 
of a similar nature, and, as far as its non-liability to tarnish is con- 
oomed, it may be considered superior to all other methods of silvering. 



CHAPTER XV. 

BLECTRO-DEPOSmON OF SILVER {continue^. 

Preparation of New Work for the Bath. — Quieking Solutions, or Mercury 
Dips. — Potash Bath. — Acid Dips. — Dipping. — Spoon and Fork Work. — 
Wiring the Work. — Arrangement of the Plating Bath. — Plating Battery. 
— Motion given to Articles while in the Bath. — Craet Stands, dtc. — ^Tea 
and Coffee Services. — Scratch-brushing. 

ft<9paration of If cw IVork fbr tlM Bath. — In order to insure 
a perfect adhesion of the silver deposit to the surface of the article 
coated, or platedf as it is erroneously termed, with this or any other 
metal, the most important consideration is abtoluU eleanliness. By this 
term we do not mean that the article should be merely clean in the 
ordinary sense, but that it must be what is termed ehemicaUy elean^ 
that is, perfectly and absolutely free from any substance which would 
prevent the silver from attaching itself firmly to the metal to be coated. 
As evidence of the extreme delicacy which it is necessary to observe in 
this respect, ve may mention that if, after an article (say a German 
silver spoon, for example) has been well scoured with powdered 
pumice and water, it be exposed to the atmosphere even for a few 
seconds, it becomes coated with a slight film of oxide — owing to the 
rapidity with which copper (a constituent part of German silver) 
attracts oxygen from the air ; this effect is still more marked in the 
case of articles made from copper and brass. Now, this slight and 
almost imperceptible film is quite sufi&cient to prevent perfect contact 
between the deposited metal and that of which the article is composed. 
This fact, in the early days of electro-plating, created a great deal of 
trouble, for it was found that the work, after being silvered, was very 
liable to strip under the pressure of the burnisher. To overcome the 
difficulty, and to secure a perfect adhesion of the two metals, a third 
metal — ^mercury or quicksilver — ^which has the power of alloying itself 
with silver, gold, German silver, copper, and brass, was employed, and 
though the author for many years obtained most successful and per- 
fectiy adherent deposits of silver without its aid, the process of 
quieking was, and still is, practised by the whole of the electro-plating 
trade. The silver solution which the author employed, however, and 
which is clesrsribed in the foregoing chapter, was differenUy prepared 



242 ELEGTBO-DEFOSinON OF 8ILVEB. 

to those ordinarilj adopted by the trade. Since the process of 
<< quioking " is generally adopted, it will be necessary to describe it in 
detail. 

Qaiokins BotatloiiSy or Mereury Dips. — This term is applied, as 
before hinted, to coating articles made of brass, copper, or German 
silver — the metals most usually subjected to the process of electro- 
plating — ^with a thin film of quicksilver, which may be effected by 
either of the following solutions : — Nitrate of Mercury Dip.^-Pui an 
ounce of mercury into a glass flask, and pour in an ounce of pure 
nitric acid diluted with three times its bulk of distilled water ; if, 
when the chemical action ceases, a small amount of undissolved mercury 
remains, add a little more acid, applying gentle heat, until the whole 
is dissolved. The solution is then to be poured into about i gallon of 
water, and well mixed by stirring. It is then ready for use, and is 
termed the quicking ioliUiony or mercury dip. Articles of brass, copper, 
or German silver dipped into this solution at once become coated with 
a thin bright film of mercury. 

Cyanide of Mercttry Dip. — ^Dissolve one ounce of mercury as before, 
and dilute the solution with about i quart of distilled water. Now 
take a solution of cyanide of potassium, and add this gradually, 
stirring after each addition, imtil the whole of the mercury is 
precipitated, which may be determined by dipping a glass rod in the 
cyanide solution, and applying it to the clear liquor after the 
precipitate has subsided a little, when, if no further effect is produced, 
the precipitation is complete. The liquor is next to be separated by 
filtration. When all the liquor has passed through the filter, a little 
water is to be poured on to the mass, and when this has thoroughly 
drained off, the precipitate is to be placed in a glass or stoneware 
vessel, and strong solution of cyanide added, with constant stirring, 
until it is all dissolved, when a small excess of the cyanide solution is 
to be added, as also sufficient water to make up one gallon of solution. 

Another mercury dip is made by dissolving red precipitate (red oxide 
of mercury) in a solution of cyanide, afterwards diluted with water. 

Fernitrate of Mercury Solution. — ^This solution is composed of — 

Pernitrate of mercury i part. 

Sulphuric acid 2 parts. 

Water 1000 „ 

A very good mercury dip may be made by simply dissolving two 
ounces of mercury in two ounces of nitric acid, without the aid of heat; 
the solution thus formed is to be diluted with about three gallons of 
water. 

The quicking bath should contain just so much mercury in solution 
9A will render ^ clean copper surface white almost immediately after 



QUTCXIMO SOLUnONB, OR BHSBOUBT DIP8, 243 

imineraion ; if the solution be too strong, or too acid (when the nitrate 
of mercuiy solution is used), or if the solution has become nearly 
exhausted by use, when copper is dipped it may turn black or dark 
coloured instead of white, in which case the quicking bath must be 
rectified, otherwise it will be impossible to obtain an adherent coating 
of silver upon the article treated in it. As a rule, the articles merely 
require to become perfectly and uniformly white from the coating of 
mercury, but the practice is to give a stronger film to work which is 
required to receive a stout deposit of silver, or gold, as the case may be. 
When the mercury dip becomes nearly exhausted and the mercurial 
coating, in consequence, becomes dark coloured, the liquor should be 
thrown away and replaced by a new solution, which is considered 
better than strengthening the old liquor ; indeed, the small amount of 
mercury which remains in the bath after having been freely used is of 
so little consideration, that the liquor may be cast aside without sacri- 
fice the moment it gives evidence of weakness by the dark appearance 
of the work instead of the characteristic Inightness of metallic 
mercury. 

It is a good plan to keep a quantity of concentrated mercurial solu- 
titm always in stock, so that when a bath becomes exhausted it may 
be renewed in a few minutes by simply throwing away the old liquor 
and adding the due proportions of strong solution and water to make 
up a fresh **dip." 

Petaali Batlu — ^To remove greasy matter communicated to the work 
by the polishing process, all articles to be plated must first be steeped 
for a short time in a hot solution of caustic potash, for which purpose 
about half a pound of American potash is dissolved in each gallon of 
water required to make up a bath, and as this solution becomes ex- 
hausted by use it must receive an addition of the cauBtic alkali. The 
workman may readily determine when the solution has lost its active 
property by simply dipping the tip of his finger in the solution and 
applying it to the tip of the tongue, when, if it fails to tingle or 
** bite *' the tongue, the solution has lost its caustic property, and may 
either be thrown away or strengthened by the addition of more caustic 
potash. When the bath has been once or twice revived in this way 
it is better to discard it altogether, when inactive, than to revive it. 
Indeed, when we conaider that the object of the caustic alkali is to 
convert the gpreasy matters on the work into soap, by which they 
become soluble and easily removed by brushing, it will be apparent 
that the bath can only be effective so long as the eattaticity of the 
alkali remains. Many persons, from ignorance of this matter, have 
frequently used their potash baths long after they have lost their 
activity, and as a natural consequence the work has come out of such 
baths Bearly in the same state as they entered it, greasy and dirty. 



*44 ELBCTRO-DEFOBinON OF SILYEB. 

Those who cannot convenientlj obtain caustic potash (American potash, 
for example) may readily prepare it as follows : Obtain a few lumps 
of fresh lime and slake them by pouring water over them, and then 
covering tiiem with a cloth ; soon after, the lime will fall into a powder, 
which must be made into milk of Hmc, as it is called, by mixing it with 
water to the consistence of milk or cream. A solution of pearlash is 
then made in boiling water, to which is added the cream of lime, and 
the mixture is to be boiled for at least an hour, in an iron vessel. 
About half or three-quarters of a pound of pearlash tu each gallon 
should be employed, and about one-fourth lees lime than potash. If 
the solution is thoroughly catuiicisedy no effervescence will occur in the 
liquor if a drop or two of hydrochloric acid are added ; if, on the con- 
trary, effervescence takes place on the addition of the acid, the boiling 
must be continued. 

Aoid Dips. — In the preparation of certain kinds of work, acid solu- 
tions or mixtures are employed which may be advantageously men- 
tioned in this place. It is well to state, however, that after dipping the 
work in acid solutions it should be thoroughly rinsed in clean water, since 

the addition of even small quantities of acid to the 
alkaline plating or gilding baths would seriously 
injure these solutions. Indeed, careless and im- 
perfect rinsing must always be avoided in all de- 
positing operations, otherwise the baths will soon 
become deteriorated ; the rinsing waters should 
be frequently changed, and the workman taught 
that in this item of his labour his motto should 
be "water no object." 
pj Q2. Nitric Acid Dip. — This is frequently used for 

dipping copper, brass, and German silver work, 
and is the ordinary aquafortis of commerce, or fuming nitric acid {nitrous 
acid). Stoneware jug« of the form shown in Fig. 82 are used for 
conveying strong acids. A dipping acid, composed as follows, is also 
much used for producing a bright and clean surface upon certain 
classes of work : — 

Nitric acid, commercial (by measure) . . . i part. 

Sulphuric acid 2 parts. 

Water 2 „ 

To tills mixture some persons add a little hydrochloric acid, and others 
a small quantity of nitrate of potassa (nitre). 

Dip for Bright Lustre. — To g^ve a bright appearance to copper, &c., 
the following mixture may be employed : — Old aquafortis, or nitric 
acid dip which has been much used, i part ; water, 2 parts ; muriatic 
acid, 6 parts. The articles are immersed in this solution for a few 




ACID DIPS. 



«45 



minutes, when they are to be briakly shaken in clean oold water, and 
if not sufficiently bright must be dipped ag^ain. If they become 
covered with a dirty deposit, the articles should be sooured with pumice 
and water, then immersed in the dip for a short time and again rinsed. 
Another method is to first dip the articles in a weak piekle, formed by 
diluting old and nearly exhausted nitric acid dip with water for a few 
minutes, after which they are to be dipped in the same old acid dip in 
its undiluted condition, and finally in strong aquafortis for a moment ; 
they are next to be well rinsed in several waters. 

I>ip for Dead Lustre. — ^To produce a dead or matted surface upon 
copper, brass, or German silver work, the following mixture is used : — 



Brown, or fuming aquafortis (by measure) 
Oil of vitriol 



2 parts, 
z part. 



To the above mixture a small quantity of common salt is added. The 
articles are allowed to remain for some time in the dip, after which 
they are withdrawn and promptly dipped in the preceding liquid and 
immediately weU rinsed. 

Bespecting old aquafortis dips, Qore says these may be ** revived to 
a certain extent by addition of oil of vitriol and common salt ; the sul- 
phuric acid decomposes the nitrate of copper in it, and also the common 
salt, and sets free nitric and hydrochloric acids, and 
crystals of sulphate of copper form at the bottom 
of the liquid. All the nitric acid may be utilised in 
this manner." This is perfectly true, but as a rule 
acid '*dips*' which have become exhausted seldom 
produce the required brilliancy or tone of colour (when 
that is an object), even if strengthened by fresh ad- 
ditions of the concentrated acids with which they were 
first pre]>ared. Zinc, tin, and lead, as also organic 
matter, generally find their way into these dips, and 
more or less interfere with the direct action of the 
nitric acid. 

Dipping. — ^The articAC to be dipped should be sus- 
pended by a wire of the same metal, or by a wire 
covered with gutta-percha or india-rubber tubing, 
and after a moment's immersion in the acid solution, 
promptly plunged into clean cold water ; if the desired 
effect — a bright or a dead lustre — ^is not fully pro- 
duced by the first dip, the article must be again dipped for a 
moment and again rinsed. In order to remove the acid effectu- 
ally, several washing vessels should be at hand, into each of which 
the article is plunged consecutively, but the last rinsing water, 
more especially, should be renewed frequently. When a number of 




Fig. 83. 



246 



EliECTBO-DEPOSmON OF SILYEB. 



small articlee require to be dipped, they may be suspended from a 
wire, looped np as in Fig. 83, or they may be placed in a per- 
forated stoneware basket (Fig. 84), provided with a handle of the 
same material. These perforated baskets are specially mannfao- 
tured at the potteries for acid dipping and other purposes, and if 
carefully treated will last for an indefinite period. The basket con- 
taining the articles to be dipped is plunged into the dipping acid, and 
moved briskly about, so as to expose every surface of the metal to the 
action of the acid ; as the vessel is raised the liquid escapes through 
the perforations, and after a brisk shaking the basket and its contents 





Fig. 84. 



Fig. 85. 



are plunged into the first washing water, in which it is again vigour- 
ously shaken, to wash away the acid as far as possible ; it is then 
treated in the same way in at least two more rinsing waters. The 
dipped articles are then to be thrown into a weak solution of crude 
bitartrate of potash, called argol\ to prevent them from becoming 
oxidised or tarnished. From this liquid they are removed as required, 
and again rinsed before being quicked and plated. For dipping pur- 
poses, stoneware and gputta-peroha bowls (Fig. 85) are also used, and 
sometimes platinum wire trays, supported by a hook, as in Fig. 87, 
are employed for very small articles. Hooks of the same kind, but in 







Pig. 86. 



various forms, are likewise used for supporting various pieces of work 
during the dipping operations. One of these is shown in Fig. 86. 

Spoon and FosIl Work. — In large establishments this class of 
work may be said to hold the leading position, since, as articles of 
domestic utility, the spoon and fork are things of ahnost universal 
requirement. As in all other kinds of electro-plated ware — and we 
may add everything else under the sun — ^the silvering, or plating, is 
accomplished according to the requirement of the customer and the 
price to be paid for the work when done. In other words, the actual 
deposit of silver which each article receives depends upon whether it 
is intended to wear well, or merely required to eelL In the former 



SPOON AND FOBX WOBK. '47 

o«ae, it U nnul for tiie cnatomer to wtagh the spooDS and forkg beforo 
he sends them to the plater, and aicitiii on dieir return, and he psjs to 
much per miDce for the silTer deposited, allowing a moderate ditcxiant 
from the original weight to cover an^ loss which may be sustained in 
preparing the work for the plating ba^. When the goods, however. 



S1g.87. 
are nerelj required to look "marketable," the amount of ailrer 
deposited upon such a elasa of work often ranges from little or nothing 
to less, if possible. 

WiTxng Ihe Wort.— Spoons and forks are first wirni, as it Is 
termed. For this purpose copp^ wire is cut into lengths of about 
iz inches. Alengthof the wire is coiled once round the shank or narrow 
part of the article, and secured by twisting it several times ; the loop 
thus formed should be quite loose, so that the podtion of the f^>oon or 
fork may be easily reversed or shifted while in the plating vat, to 
equalise the deposit, and to allow the parts where the wire has been 
in contact to become coated with silver. The copper wire used for 
"slinging" is usually about No. 20 B.W.G. (Birmingham "Wire 
Gauge), which is the gauge most generally adopted in this country. 
The spoonii, &c., are next placed in the hot potash bath, where they 
are allowed to remain for a short time, when 
they are removed, a few at a time, and 
rinsed in cold water. They are next to be 
hrosbed or scoured all over with fine 
pumice-powder moistened with water, and 
then thrown into clean water, where thej 
remain until a sufficient number have 
been scoured, when these arc taken out by their wires and im- 
Diersed in the qiiiclting solution, which, for spoon work, may con- 
veniently be in a shallow oval pan of the form shown in Fig. SS. 
After remaining in the quicldiig bath a short time, they arc 
examined, and if sufficiently qKvlced, and uniformly bright, like 
qnioksilver, they are rinsed in water and at once sospended in tha 



248 ELECTBO-DKPOSITION OP 8ILVEB. 

plating tank, as bloae together as possible without tondhing. When 
the bath is filled with work, the spoons or forks should be turned 
upside down by slipping the shank through the loop ; and the work- 
man who does this must be verj careful to handle them as little as 
possible, and only to grip them with the fingers by the edget^ which 
an experienced plater will do with great smartness, and with very 
trifling contact with his fingers. The objects of thus changing the 
position of the work are twofold, namely, to allow the wire mark to 
become coated with silver, and to equalise the deposit, which always 
takes place more energetically at the U>%oer end of the article while in 
the bath. This system of shifting should be repeatedly effected until 
the required deposit is obtained. When shifting the spoons, &c., all 
that is necessary is to raise the straight portion of the suspending 
wire which is above the solution with one hand, which brings, say, the 
handle of the spoon, out of the solution; if this be now gripped 
between the finger and thumb of the other hand at its edges, and 
raised until the bowl end touches the loop, by simply turning the 
spoon round its bowl will be uppermost, in which position the article 
is carefully but quickly lowered into the bath again. 

Another method of suspending spoons and forks in the plating bath 
is the following : Copper wire, about the t^ckness of ordinary bell 
^ wire, is cut up into suitable lengths, and which will depend 

upon the distance between the negative conducting-rod and 
the surface of the silver solution. These wires are next to 
be bent into the form of a hook at one end, and at the other 
end is formed a loop, as in Fig. 89, leaving an opening 
through which the shank of a spoon or fork may pass into 
the ring or loop and be supported by it. To prevent the 
sHver from being deposited upon the vertical portion of 
the wire, where it would be useless and unnecessary, this 
portion of the wire should be protected by means of glass, 
Fig. 89. gutta-percha, or vulcanised india-rubber tubing, which is 
slipped over the wire before the upper hook is formed. 
After being some time in use, the lower ring becomes thickly coated 
with a crystalline deposit of pure silver, when these wires must be 
replaced by new ones, and the insulating tubes may be again applied 
after removal from the old wires. 

Ordinary slinging wires, as those previously described, should never 
be used more than once, and for this reason : when a certain amount 
of silver or other metal is deposited upon wire — except under certain 
conditions — it is invariably more or less brittle, and in attemptiag to 
twist it round an article it is very liable to break, often causing the 
article to fall from the hand — perhaps into the bath — and rendering 
the silver-covered fragments of wire liable to be wasted by being 



ABSUiaEHZNT OF THK FIATIHB B4TH. 149 

nrept amj with tlie dirt of the floor. It is more economioal to 
emplor freah wires for each batch of work, and to ttrip Oie olver or 
other metal {mm the wires by either of the prooeaaes hereafter given, 
bj which not only mtij all the metal be recovered, bnt by aantalutg, 
cleaning', and straighteiiiii^ tJie wires, they may be used agtiiii and 
again. Uoreover, a wire that has been twisted once becomes hardened 
at that part, and cannot with «aie(y be twisted again without being 

lArraasanunt of th» TlaMag BatlL — The size and form of depoflit- 
ing; tanks far (diver plating vary in different establiahments, sa also 
does the material of which they are constructed. For small quanti- 
ties of silver salntian, say from ten op to thirty gallons, oval stone- 
ware pani may be used, and with ordinary care will last a great 
number of years. Wooden tubs, if absolutely clean, may also bo em- 
ployed for small operations, but since that material absorbs tlie silver 
solntioD, aneh vessels 
should be well soaked 
with hot water before 
pouring in the solution. 
Tanks made from slate, 
wiUi india-rubber joints, 
have also been much 
used in nlver- plating. 
Very good platii^ tanks 
may be made in the same 
way as directed for 
nickel - plating baths, 

Ihat is, an outer vessel pi„_ „ 

of wood, secured by 

screwed bolts, lined witii sheet lead, and re-lined with matched board- 
ing. Wrought-ijon tanks, lined with wood, are, however, greatly pre- 
ferred, and when properly constructed and lined, form the most durable 
of all vessels for solutions of tlds desoriptiou. Depodting tanks for large 
operatious are nsually about six feet in length, three feet in width, 
and about two feet six inches in depth, and hold from two to three 
hnndred gallons of solution ; tanks of greater length are, however, 
sometimes employed. An ordinary wrought-iron plating tank is 
shown in Fig. 90, in which also the arrangement of the silver anodes 
and sundry articles in solution is seen. The upper rim of the tank is 
furnished with a flange of wood, firmly &kbA in its position, upon 
which rest two rectangles of brass tubing or stout copper tod. The 
outer rectangle frequ«itly consists of brass tubing about an inch m 
one comer of which a binding screw is attached, by 
IS of solder, for connecting it with the positive pole of the battery 



250 ELaonto-DBPOfiinoN op siltes. 

or other generator of eleotrioity. The inner rectangle nhniild be of 
etout copper rod, or wire — usually abont one-half the tUoknees of the 
former, and is also provided with a binding screw at one oomer, to 
oonnect it with the negatlTe pole of the hattet?. A series of brass 
rods, from half to one inch in diameter, and each about the length of 
the tank's width, are laid mtosb the outer rectangle, and from these 
are snspended the stiver anodes ; similar but shorter rods of brass 
are plaoed between each pair of anodet, and rest upon the inner 
rectangle ; from theee rods the articles to be plated are suspended, 
as diown in the engraving. Before the respeotive oondnotdng 
rods are plaoed in position, they mnst bo tlioroaghly well cleaned 
with emery doth, as also must be the rectangular conductors and 
wire holes of binding screws which are to receive the positive and 
negative oondncting wires, the ends of which must likewise be cleaned 
with emery doth each time before making connection with the 
battery. It may be well here to remark that all the points of connec- 
tion between the various ttxls, wires, and binding screws must be 
kept perfectly clean, otherwise the electric current will be obatrncted 
in itii passage. When the conducting rods become foul by being 
sploshed with the cyanide solntion, they should be well deanod with 
emery cloth, and the operntioii of cleaning these rods should 
always be performed each morning before the first batch of work is 
placed in the solution ; the emery cloth should only be applied when 
the condacting rods ore perfectly diy. It is always a characteriedoof 
a roolly good plater that all his conducting rods are kept bright and 
dean, and every appliance in its proper place. 

Flatbis BB.tt«TT. — The most useful form of battery for depositing 

silver, either upon a large or smaH scale, ia a modification of the 

WoUaston battery shown in Kg- 9'- ^'^ 

depositing upon a large scale, a stone jar 

capable of holding about ten gallons forms 

the battery cell. A bar of wood, d, having a 

" groove cut in it, bo as to allow a stout plate 

of zino to pass freely through it, rests 

across the battery jar, 4. Two sheets of 

copper, B b, connected by strips of the same 

metal soldered to the upper comers, are plaoed 

over the wooden bar, and a binding screw 

_ connected to one of the copper plates, either 

by means of solder or by a side screw. The 

copper plates should nearly reach to the bottom of the Jar. A suitable 

binding screw is attached to the rinc plate, c, which muBt be well omol- 

gamatel. The exciting fluid consists of dilute aulphnrio acid, in the 

proportion of one part of the latter to fifteen parts of oold water. To 



PLATING SATTEKT. Sgl 

^e«ent tlie tino from oomiog in ooatoct with the ooppar pl&t«, a 
small block of wood, luLTing tt tolembly deep groove of Uia Boma 
widtli u the thiokneM of the sheet of oopper, maj be fixed on to eaoh 
ed^ of the pair of plstee about midirmj between t^e top and the bot- 
tom. In order to regulate tlie amount of omreitt in working' theee 
batteries, it ia oommonlj the praotioa to drill a hole in the centre of 
the apper port of the nno piste, to which a strong cord ia attached, 
and allowed to poos oyer a pulley, the other end of the oord being oon- 
neoted to a oonnterweight. A windlass 
ansngement, aa in Hg- 9'< ^ '^ i^Bed 
for this purpose, by which the line 
plate GOD be raised and lowered by 
amply timing a handle oonneoted to a 
rerolving spindle, supported by np- 
righta of wood, round which the oord 
beoomea wound or unwound according 
to the motion (pTen to the handle. 

When the bath U about to be filled i 
with work, the zinc plate shonld only 
be lowered a short distance into the pj^ -^^ 

acid solution, and the aarfHoe is to be 

increased as the filling of the bath progreBsee ; if this precaution 
ia not observed, the depomtdon will take place too rapidly upon the 
work, and the deposited metal will Msnme a grey colour instead 
of the characteristic white, besides which the silver will be liable to 
strip or separate from the underlying metal in the subsequent pro- 
oeeseeof acratcb-brushing and bumidiing, or even under the less severe 
process of poliflhing. A very safe way to check tie too rapid deposit, 
ia to suspend an anode from the negative oondncting rod as a cathode 
when the first batch of articles is beingplacedin the bath. Whenvery 
powerful batteries or dynamo -machinee are used, the remstance coil 
(iiide Nickel -plating) must be employed. 

MottoB BlvMt to AxUolsa wUU la th* BattL — In order to insure 
uniformity of deposit while employing strong electric power from 
magneto or dynamo machines, it has been found that by keeping the 
articles sbwiy in motion while deposition is taking place, this deajrable 
cud can be effectually attained. There are several ingeniouB devices 
adopted for this purpose, to several of which we may now direct 
attention. It is a fact that depositbn takes place first at the exlraae 
end of the article in solation — that is the point /ar(AM(/n>m the source 
of electricity ; * and this being so, we may be sure that the deposition 



SJ3 BI^OTRO-DKPOSITION OF SILVKR. 

progTtC8«s in ike same ntjo dnriiig the whole tdme the articlea Bra 
ceoaTin^ the deposited metal provided the wlnticm and the work 
remain nndisturbed. Indeed, in the oase of table forks, if we buSot 
them to remain, with their prongs doamuiartl, undigturbod for a oon- 
riderable time, we Hhall find, on removing them from the bath, that 
the prongB, from the extreine tips upward, will be coated with a 
oiysUUine or grsDular deposit, while the extreme upper portion of thF 
article will be but poorly coated. In no oaae is the fact of the depoiil 
taking place from the lowest part of an article upward more practi- 
cally illuHtrsted than in the process of " fltripping " (to which we 
shall refer hereafter) or dissolving the silver from the snrf ace of platsd 
artiolet, when, after they have been in the stripping eolation for soma 
time, we find that the latt particles of ailrer which will yield to the 



Fig- ga- 
ll action of the liquid are the points of the prongs of a fork, 
the lowest part of the bowl of a epoon, as also (it the articles have 
been duly shifted during the plating) the extreme ends of the handles 
of either article. 

To keep the articles in gent^ motioa while in the bath, one method 
ia to connect the suspending rods to a frame of iron, having four 
wheels about three inches in diameter connected to it, which slowly 
bavel to and fro to the extent of three or four inches upon inclined 
rails attached to the upper edges of the tank, the motion, which is both 
hoiizontsl and vertical, b«ng given by means of an eccentric whed 
driven by steam power. By another arrangemeiit, the articles are 
Bnspend^ from a frame (as in Fig, 9,1), and the motion given by the 
ecceutrio wheel as shown in the engraving. The simplicity of the 
former anangement, however, will be at once apparent. 

Omat BtiMiM, fte. — Before being submitted to tbe cleansing opera- 



CBUET STANDS, ETC. 353 

tioiw, quiekinf^, Sec, before described, the ** wires '* of oruet and liqneur 
stands must be separated from the bottoms, to which they are 
generally connected by small nuts, and these latter should be slung 
upon a wire and laid aside until the other parts of the article are ready 
for plating. A wire is then to be connected to each part of the cruet 
frame, and iLese are then to be immersed in the hot potash liquor, 
being left therein sufficiently long to dissolve or loosen any greasy 
matter which may attach to them. After being rinsed, they are to be 
well brushed with powdered pumice and water. The brushes used for 
this and similar purposes are made from hog hair, and are supplied 
with one or more rows, to suit the various purposes for which they are 
required ; for example, a one-rowed brush is very useful for cleaning 
the joints connecting the rings with the framework of cruet stands, as 
also for all crevices which cannot be reached by a wider tool ; a two- 
rowed brush is useful for crevices of g^reater extent and for hollows ; 
and three, four, five, and six -rowed brushes for flat surfaces, embossed 
work, and so on. One of these useful tools is shown in Fig. 94. 




Fig 94. 

After scouring and rinsmg, the parts of the cruet stand or liqueur 
stand are to be immersed in the quiddng solution until uniformly 
white in every part, after which they must be well rinsed and immedi- 
ately put into the plating bath ; after a short immersion, the pieces 
should be gentiy shaken, so as to shift the sling^g wire from its 
point of contact, and thus enable that spot to become coated with 
silver ; it is always advisable to repeatedly change the position of the 
wire so as to avoid the formation of what is termed a wire mark, 
and which is of course due to the deposit not taking place at the 
spot where the wire touches the article, thereby leaving a depression 
when the article is fully plated. The flat base of the oruet stand 
should be suspended by two wires, each being passed through one 
of the holes at the comer, and it should be slung sideways and 
not leng^wise ; its position in the bath Bhould be reversed occa- 
sionally, so as to render the deposit as uniform as possible ; 
the same observation applies to the ** wire " part of the cruet 
stand. When mounts are sent with the cruet stand, not sepa- 
rate, but cemented to the cruets, which is often the case, it will be 
well, if it can be convenientiy done, to remove the pin which connects 
the top or cover with the rim of the mustard mount, so as to plate 
these parts separately, otherwise the cover will require shifting 



254 BLEOTBO-DEPOSTTION OF tflLVES. 

repeatedly in order to allow thoee parts of ihe joint which are pro- 
tected from receiving the deposit when the cover is cpen, to become 
duly coated. 

Tea and OofDM Barvlcas.— Like the foregoing articles, these are 
of very variable design, and are either plain, chased and embossed, or 
simply engraved. Unless sent direct from the manufacturer in the 
proper condition for plating — that is, with their handles and covers 
unfixed — it will be better to remove the pins connecting these parts 
with the bodies of tea and coffee pots before doing anything else to 
them, unless, as is sometimes the case, they are so weU riveted as to 
render their severance a matter of difficulty. The disadvantages 
attending the plating of these vessels with their handles and lids on 
are that the solution is apt to get inside the sockets of the handles, 
and to ooze out at the joints when the article is finished, while the 
joint which unites the lid with the body can only be properly plated 
when the lid is shut, at which time the interior of the lid can 
receive no deposit. When sent to the plater by the manufacturer, 
the various parts are usually either separate, or merely held to- 
gether by long pins, which may readily be withdrawn by a pair of 
pliers, and the parts again put together in the same way when the 
articles are plated and finished — that is burnished or polished, as the 
case may be. 

In plating work of this description, the articles are potashed, scoured 
and quicked as before, and when ready for the plating bath, the tea 
and coffee pots are generally wired by passing the slinging wire through 
the rivet-holes of the joints ; but in order to equalise the deposit as 
far as possible, it is a grood plan, after the article has received a certain 
amount of deposit, to make a loop at one end of a copper wire, and 
to pass it under one of the feet of the teapot, then to raise the vessel 
somewhat, and connect the other end of the wire with the oonduoting 
rod ; care must be taken, however, not to let the wire touch the body 
of the vessel, or if it does so, to shift it frequently. 

Since deposition always takes place more fuUy at the points and 
projections of an article, it will be readily understood that the inte- 
riors of vessels — ^being also out of ehett%cal nght^ so to speak, of the 
anodoH — will receive little if any deposit of silver. This being the 
case, if we wish to do the work thoroughly well in every part, it will 
l)e necpBsary to deposit a coating of silver upon the inside eitlier before 
or after the exterior has been plated. To do this, the vessel being 
well cleaned inside, is placed upright on a level bench, and a wire 
connected to the negative pole of the battery is slipped through the 
joint as before. A small silver anode, being either a strip of the 
metal or a narrow cylinder, is to be attached to the positive i)ole, and 
the anode lowered into the hollow of the vessel, care being taken that 



soSATOB-BxnsHiMa. 355 

it does Dot toooh in any pMt. llie veeael u tli«n to be filled to the 
top with eilver Bolatioa dipped out of the bath witli a jug, and die 
whole allowed to rest for half an hour or so, at the end of which 
time the interior will ^nerall; have received a miffident coating of 

■ozawb-bnulil&s. — Ooe of the most important mechanical opera- 

tiona oonneoted with idlver-plating is that of scratch -brushing. For 

this purpose skems of thin bren wire, bonnd round with stout brass or 

eopper wire (Fig-. 97), are used. When the p1at«d articles are removed 

from the bath, they present a pearlj white appeaiance not unlike very 

fine porcelain ware, but still more 

cloHely reaemblin^ standard ailTer 

that baa been healed and pickled 

in dilute Bulphurio acid, ae in the 

process of KhUetiing watch dials. 

The dead white lustre of clcctro- 

depodted ailver is due to the metal 

beang deposited in a etygtalline 

form, and the dulnees is of Bo 

fugitive a natnre that even scraEch- 

ing the surface with the finger nail 

will render the part more or leas 

bright by bumiiihing the soft and 

delicate crystalliiie texture of the 

depoat. The object of scratcb- 

bmshing is to obliterate the wbit« 

" burr," as it is called, before the 

work ia placed in the hands of the 

bumUher or polisher, otherwise 

it would be apt to show in such 
parte of the finished article as 
could not be reached by the tools ^g. 95. 

employed in those operations. As 

in the case of gilding, the revolving wmtj'h-brui'hcH are kept con- 
stantly wetted by a thin stream of elale liccr, or half beer and 
wBt<T, supplied, by means of a tap, from a small vk-sioI (which may 
conveniently be a wooden bucket) placed on the top of the scratch- 
brush box. A tin can, or other light veseel, sitandH upon the finer, 
beneath the bon, to catch the beer runnings, which escape through 
a pipe let into a hole in tbe bottom of the box. A stdll more handy 
plan is to have a small hook fixed below the r^ht-hand comer of 
the Bcrateh-bmsh box, for supporting a tin can or other vessel ; and 
I^ giving the box a slight inclination forwards, and towards tbe right- 
hand oomar, the liijuor will fiow out through a hole at the comer, in 



aS^ 



ELECTBO-DEPOBITION OF SILYEB. 




which a ahort piece of lead pipe should be inserted. By this aixaage- 
ment (Fig. 95], the workman can empty the can into theyeflsel above, 
wheneyer the beer liquor ceases to drip upon the scratch-brushes, 
without allowing* the driving wheel to stop. Much timemay be saved 
in this way, especially when the liquid happens to run short, at which 

tune the can requires to be emptied 
frequently. To prevent the beer 
runnings from overflowing, and 
thus making a mess on the floor, 
while wasting the liquor, no more 
liquor should be put into the 
p. ^^ cLBtem above than the vessel be- 

low will contain. A quart or 
three-pint can full will be quite sufficient for ordinary work, and a 
vessel of this latter capacity will be quite as large as the workman 
can manipulate readily without stopping the lathe. 

The lathe scratch-brush consists of a series of six or eight scratch- 
brushes (according to the number of grooves in the '* chuck ") bound 
to the chuck by strong cord, as in Fig. 96. Previous to 
fixing the brushes, the skein of fine brass wire forming a 
single scratch -brush. Fig. 97, is to be out with a pair of 
shears or strong scissors. Before applying the compound 
brush — which is connected to the lathe-head by means of its 
screwed socket — to the plated work, the brushes should be 
opened, or spread, by pressing rather hard upon them, while 
revolving, with a piece of stout metal, or the handle of one 
of the cleaning brushes ; this will spread the bundles of wire 
into a brush-like form suitable for the purpose to which they 
are to be applied. It may be well to state that the revolving 
scratch-brush should on no account be applied to the work in 
a dry state, but only when the beer liquor is running suffi- 
ciently free to keep the brushes wei. 

In working the scratch -brush, it must be allowed to re- 
volve to the right of the operator, otherwise the ** chuck " will 
be liable to come unscrewed ; moreover, this is the most con- 
venient motion for enabling the workman to guide the articles 
without risk of their being jerked out of his hand — an acci- 
dent that might readily occur if he inadvertently turned the 
PI wheel the wrong way. In scratch -brushing spoons and forks, 

' a very moderate pressure is all that is necessary to render 
the surface bright; a little more pressure, however, is required 
for the edges of salvers, dishes, handles and feet of cruet stands, and 
other work in which hollows of some depth form a necessary feature 
of the ornamental moimts. 



PLATIKa BT DYVAMO-ELECTBICITY. 257 

nattniT Ivj ]>]rBaiBO-BlMtvioit3r. — In the larg^er electro-plating 
ertabliahmentB, magneto or djnamo-electrio machines are employed, 
and the cnirent from these poweifal machines is conveyed by- 
stout leading wires to the Tazions baths, the foroe of the current 
entering the baths being regnlated by resistances. In works of 
moderau dimensions, a good machine, either of the magneto or 
dynamo-eleotrio tjrpe, will supply sufScient electricity to work a large 
bath of each of the following solutions: nickel, silver, brass and 
copper, as also a good-sized gold bath. In working with these 
machines, it is of the greatest importance that they should be driven 
at an uniform speed ; and though some machines require to be 
driven at a higher rate of speed than others, the nn^-gimnm allowed 
by the respective makers should never be exceeded, or the machine 
may become considerably heated and seriously injured. When start- 
ing the machine, the number of its revolutions should be ascertained 
by means of the tpeed indicator referred to elsewhere, and as far as 
practicable the noimal speed should be maintained without sensible 
variation while the current is passing into the vats. Although this 
uniformity of speed is more certainly obtained, we believe, with gas 
engines than with steam power, if proper care and attention are gfiven, 
and frequent examination of the speed of the dynamo-annature made by 
the plater, tolerable regularity may be attained from the latter source 
of power. It must always be remembered by the plater, that when 
the engine which drives the dynamo is also employed for driving 
polishing lathes, emery wheels, &o., when very heavy pieces are being 
treated in the polishing shop the speed of the dynamo may be greatly 
influenced ; indeed we have frequently known the belt to be suddenly 
thrown off the pulley of a dynamo from this cause, and the machine, 
of course, brought to a full stop. 



<r 



CHAPTEE XVI. 

ELECTRO-DEPOSITION OF SILVER {continued). 

Plating Britannia Metal, iic. — Plating Zinc, Iron, <bc.— Replating Old Woric 
.-Preparation of Old Plated Ware.— Stripping Silvei from Old Plated 
Articles. — Stripping Gold from Old Plated Articles.— Hand Polishing. 
— Resilvering Electro-plate. — Ctiaracteristics of Electro-plate. — Deposit- 
ing Silver by Weight. — Boseleur's Argyrometric Scale. — Solid Silver 
Deposits. — On the Thiclcnees of Electro-deposited Silver. — Pyro-plating. 
—Whitening Electro-plated Articles.— Whitening Silver Work. 

Plattns Britannia Bletal, *e. — It was formerly the practice to 
give a coating of copper or brass to articles made from Britazmia 
metal, tin, lead, or pewter, since it was found difficult otherwise to 
plate such metals and alloys successfully, that is without being liable 
to strip. It is usual now, however, to immerse the articles first in the 
hot potash solution, and to place them, with or without previous 
rinsing, in the depositing- bath. Since the potash bath dissolves a 
small quantity of metal from the surface of articles made from these 
metals, a favourable surface is left for the reception of the silver 
deposit, to which the metal adheres tolerably well — indeed sufficiently 
so to bear the pressure of the burnishing tools. Since Britannia 
metal, pewter, &c., are not such good conductors of electricity as 
German silver, copper, or brass, an energetic current must be applied 
when the articles are first immersed in the bath, and when the whole 
surface of each article is perfectly coated with silver, the amount of 
current may be somewhat diminished for a time, and again augmented 
as the deposit becomes stouter ; care being taken not to employ too 
strong a current, however, in any st&ge of the plating process. It 
may be mentioned that articles made from Britannia metal — which 
are gpenerally sold at a very low price — are seldom honoured with more 
than a mere film of silver, in fact just so much as will render them 
marketable, and no more ; still, however, a very extensive trade is 
done in work of this description, much of which presents an exceed- 
ingly creditable appearance. 

Plating Zinc, Iron, See. — ^To coat these metals with silver, it is 
best to first give them a slight coating of brass or copper, in an alka- 
line solution, which docs not occupy much time, neitiier is it a costiy 



BEPLATINO OLD WOBK. 259 

proceeding. Both these metals adhere pretty firmly to zinc, iron, 
and steel, while silver attaches itself freely to brass and copper. 
If hot solutions of copper or brass arc used, the trifling deposit 
required to enable the subsequent coating of silver to adhere to the 
zinc, &c., can be obtained in a very few minutes. Each opera- 
tion, however, should follow in quick and unbroken succession, for if 
the brass or copper- coated article be allowed to remain, even for a few 
seconds, in the air before being placed in the silver bath, it will 
rapidly oxidise, and render the deposited silver liable to strip when the 
article is scratch-brushed. Moreover, if the brassed or coppered 
articles are allowed to remain for a short time in the air while in a 
moist condition, voltaic action will be set up between the zinc and the 
metallic covering, by which the latter will become loosened, and will 
readily peel off under the action of the scratch-brush. Each article, 
after being brassed or coppered, should, after rinsing, be placed at 
once in the silvering-bath. 

»1»latlng Old Work. — Under this head must be considered not 
only the old Sheffield and Birmingham ware, the manufacture of 
which became superseded by the electro-plating process, but also the 
moro modem article known as ** electro -plate *' (the basis of which is 
G^erman silver), which has, by domestic use, become unsightly in con- 
sequence of the silver having worn off the edges and other prominent 
parts most subject to friction in the process of cleaning. In the busi- 
ness of replating, thero must ever be a constant if not a growing 
trade, if we consider the enormous quantity of plated goods which 
annually flow into the market, and which must — even the best of it — 
requiro rosilvering at some time or other, while the inferior classes of 
goods may requiro the ser\'icc8 of the electro-plater at a much earlier 
period than the purchaser of the articles expected. 

Prfparation of OU ^'Vlatod" "War* fbr BmUtotIbs.— These 
articles, whether of Sheffield or Birmingham manufacturo, have a 
basis of copper. The better class of plated waro, which was originally 
sold at about half the price of standard silver, and some of which may 
be occasionally met with, though doubtless becoming rarer every year, 
is of most excellent quality, both as to design and workmanship, and 
when properly prepared for replating, and well silvered and finished 
after, is well worthy of being roplaced upon the table by the side of 
the moro modem articles of electro-plate. Such articles, however, 
should never be roplated with an insignificant coating of silver, since 
the copper surface beneath would soon reappear and expose the indif- 
ferent quality of the plater's work. It may be well to state, however, 
that by far the greater proportion of old ** plated '' articles aro not of 
the same quality as the old Sheffield plate and the equally admirable 
work formerly manufactured by the distinguished firm of Boulton and 



26o ELECTBO-DBFOSinON OF StLVER. 

Wdtty of Birmingham, some specimens of which may also be coca- 
aionallj met with ; but a very inferior class of g^oods, which maj 
generally be recognised by their having lost nearly the whole of their 
silver covering — which was never very much — ^whereas in the better 
class of old plated ware the silver has worn off chiefly at the extreme 
edges, while the remainder of the article retains a sound coating of silver. 

In preparing old plated cruet frames, &c., for replating, the wires, 
which are g^enerally attached by soft solder to the stands, must be 
separated by first scraping the solder clean, and then applying a hot 
soldering-iron (using a little powdered resin), which must be done 
very carefully, otherwise the solder which connects the feet of the 
stand may become melted, causing them to drop off ; it is safer, when 
applying the hot iron, to have an assistant at hand, who with a brush 
or harems foot should wipe away the solder from the joint when it is 
melted. All the joints being treated in this way, in the first instance, 
the ground is cleared, when by a fresh appUoation of the soldering- 
iron the legs of the wire may be loosened, one at a time, until the 
whole series have become partially displaced, after which, by ag^ain 
applying the hot iron, the legs, one after another, may be forced out. 
If the two parts of the frame are not taken asunder in this cautious 
way, the workman may involve himself in much trouble from the 
melting of the lead mounts (called ** silver *' mounts], the dropping 
off of legSf feet, &c., all of which may be avoided in the way we have 
suggested. It must be understood that our suggestions are specially' 
made for the g^dance of those who, though good platers, may not be 
experts in the application of the soldering-iron. It is usually the 
practice to remove what silver there may be upon old plated articles 
by the process termed " stripping." This consists in immersing the 
article in a hot acid liquid which, while dissolving the silver from the 
surface, acts but little upon the underlying metal, whether it be of 
copper, brass, or German silver. The process of stripping being an 
important auxiliary in connection with the replating of old work, as 
also in cases in which an imsuccessful deposit has been obtained upon 
new work, we may advantag^usly describe the process at once ; but 
previous to doing so, we may state that the silver removed by stripping 
from the better class of old plated articles is sometimes an important 
gain to the electro-plater, if he be fortunate enough to receive a 
liberal amount of such work, while, on the other hand, the inferior 
qualities of plated ware will yield him no such satisfaction. 

BtrippliiS Bllvar from. Old Flatod .AirtielM. — A stripping -bath is 
first made by pouring a sufficient quantity of strong oil of vitriol into 
a suitable stoneware vessel, which must be made hot, either by means 
of a sand bath, or in any other convenient way. To this must be 
added a small quantity of either nitrate of potash, or nitrate of soda, 



tnopMxG ou> PLktmD ABticuca. 261 

and the mixtnve stined witha stout glaas rod until the telts are di»- 
eolTod. The article to be stripped is first slung upon a stout copper 
wire ; it is then to be lowered in the liquid, being held by the wire, 
until wholly immerBed. LeaTe the artide thus for a few moments, 
then raise it out of the solution, and obeenre if the sQver has been 
partially removed ; then redip the article and leave it in the bath for 
a short time longer, then examine it again ; if the action appears 
rather slow, add a little more nitre, and agfain immerse the article. 
When the silver appears to be dissolving off pretty freely, the opera- 
hon. must be watched with care, by dipping the article up and down in 
the solution, and looking at it occasionally, and the operation must be 
kept up until all the sQver has disappeared, leaving a bare copper 
surface. When a large number of articles have to be stripped, a good 
many of these may be placed in a hot acid bath at the same time, but 
since they will doubtless vary greatly in the proportion of silver upon 
them, they should be constantly examined, and those which are 
first stripped, or desiheeredy must be at once removed and plunged into 
cold wai^. When all the articles are thoroughly freed from silver, 
and weU rinsed, they are to be prepared for plating by first bvffing 
them, as described in the chapter on polishing, after which they are 
cleaned and quicked in ihe same way as new work. 

A Cold Stripping SoluHon^ which is not so quick in its action as the 
former, is made 1^ putting in a stoneware vessel a quantity of strong 
sulphuric acid, to which is added concentrated nitric acid in the pro- 
portion of I part of the latter acid to 10 parts of the former (by 
measnre). In this mixture the articles are suspended until they g^ve 
signs of being nearly deprived of their silver, when they are somewhat 
more closely attended to until the removal of the silver is complete, 
when they are at once placed in cold water. The articles must be 
perfectly dry when placed in this stripping liquid, since the presence 
of even a small quantity of water will cause the acid to attack the 
copper, brass, or Gterman silver, of which the articles may be made. 
The vessel should also be kept constantly covered, since sulphuric acid 
attracts moisture from the air. The silver may be recovered from old 
stripping solutions by either of the methods described elsewhere. 

Buffing Old Work after Stripping. — ^The stripped articles, after being 
thoroughly well rinsed and dried, ore sent to the polishing shop, where 
they are buffed and finished, and the cavities, caused by the action of 
vinegar or other condiments upon the base of cruet stands, as far as 
possible removed. Sometimee these depressions are so deep that they 
cannot be wholly removed without rendering the surface so thin that, 
in buiniahing this portion of the article, it is liable to warp or become 
stretched, rendering the fiat surface unsightly for ever after. The 
back of the stand, which is usually coated with tin, should be roughly 



862 BLEOTfiO-DfiPOSmOK OF filLVltft. 

** bobbed " with sand until all the tin is removed. The next items, 
which usually give some trouble, are the so-called ** silver mounts," 
which are commonly of two Hnds. The edge, or border of the stand, 
being originally a shell of silver foil, struck in design, and fiUed or 
backed up with lead or solder, is generally more or less free from 
silver, except in the hoUows ; and since the soft metal does not receive 
the silver deposit so favourably as the metal of which the rest of the 
article is composed, these edges must receive special treatment, other- 
wise the sUver deposited upon them will be brushed off in the after- 
process of scratch-brushing. There are several ways of treating ''lead 
edges, ^* as they are properly called. Some persons remove them alto* 
gether, and replace them by brass mounts, which are specially sold for 
this purpose. If this plan be not adopted, we must endeavour to 
induce the silver to adhere to the lead mounts by some means or other. 
The edge of the article, after being cleaned, may be suspended, one 
angle at a time, in a brassing bath, or alkaline coppering solution, 
until a film of either metal is deposited upon the leaden mount, when, 
after being rinsed, a second angle may be treated in the same way, 
and so on, until the entire edge is brassed or coppered. The small 
amount of brass or copper, as the case may be, which may have 
deposited upon the plain portions of the work, may be removed by 
means of a soft piece of wood, powdered pumice, and water. Edges 
treated in this way generally receive a good adherent coating of 
silver. Sometimes, but not always, the ordinary ''quioking*' will 
assist the adhesion of the silver to the lead mounts. Another method 
of depositing a firm coating of copper upon lead edges is to put a 
weak acid solution of sulphate of copper in a shallow vessel, and having 
a small piece of iron rod in one hand, to lower one portion of the edg^e 
of the cruet bottom into the solution ; then touching the article under 
the liquid, in a short time a bright coating of copper will be deposited 
upon the leaden surfaces, by means of the voltaic action thus set up, 
when this portion may be rinsed, and the remainder treated in the 
same way. Or take a small piece of copper, and connect it by a wire 
to the positive electrode of a battery, envelop this copper in a piece of 
chamois leather or rag, then put the article in connection with the 
negative electrode. By dipping the pad, or *' doctor,'* in either an 
acid or an alkaline solution of copper, or in a warm brassing solution, 
and applying it to the part required to be coated, a deposit will at 
once take place, which may be strengthened by repeatedly dipping the 
pad in the solution and applying again. In this way, by moving the 
pad containing the small anode of copper or brass along the edge, the 
required deposit may be effected in a very short time with a battery of 
good power — a Bunsen 'cell, for example. 
Old ** pl&ted " tea and coffee pots are invariably coated inside with 



OLD PLATBD ABTIOLBS. 263 

tin ; and if this part of thd article Is required to be Hilvcred — which is 
sometimes, though not always, the case — ^the tin should first be 
removed by dissolving it in some menstruum which will not dissolve 
the copper beneath. For this purpose either hydrochloric acid or a 
solution of caustic potash may be used. If the former, the inside of 
the vessel should first be filled with a boiling hot solution of potash, 
and after a time the liquid is to be poured out and thoroughly rinsed. 
It must then be filled with strong muriatic acid, and allowed to rest 
until the upper surface, upon being rubbed with a strip of wood, 
exposes the copper, when the acid is to be poured out, and the vessel 
again rinsed. The inside must now be cleaned by brushing with 
silver sand and water as far as the brush will reach, when the bottom 
and hollow parts of the body may be scoured with a mop made with 
rag or pieces of cloth and silver sand. If it is preferred to dissolve 
the tin from the inside of the vessel by means of potash, the hot liquid 
must be poured in as before, and the vessel placed where the heat can 
be kept up until the desired object — ^the removal of the tin — is attained, 
when the vessel must be cleaned aj before. Dissolving the tin from 
the Inside of such old plated articles should be the first preparatory 
process they are subjected to ; indeed, the interiors of all vessels to be 
electro-plated should be attended to first, in all the preliminary opera- 
tions, but more especially in the operations of scouring, in which the 
handling of the outside, though a necessity, is liable to cause the work 
to strip (especially in nickel-plating), unless the hands are kept well 
charged with the pumice or other gritty matter used in scouring. To 
remove tin from copper surfaces, a hot solution of perehhride of iron 
may also be used, for although this iron salt acts freely upon copper, 
voltaic action is at once set up when the two metals, tin and copper, 
come in contact with the hot solution of the perchloride, which 
quickly loosens the tin so that it may be brushed away with perfect 
ease. From the rapidity of its action, we should prefer to adopt the 
latter mode of de- tinning copper articles, but either of the former 
would be safest in the hands of careless or inexperienced manipu- 
lators. 

Old ''plated " — we use the term in reference to Sheffield ware more 
especially — sug^-bowls, cream-ewers, mugs, goblets, &c., which have 
been gilt inside, should have what gold may still remain upon the 
article ** stripped off ** before other operations are proceeded with ; 
and since these articles were originally mercury ffiU, in which a liberal 
amount of gold was often employed, it is frequentiy worth while to 
remove this by dissolving it from the insides of the vessels ; and the 
same practice should be adopted with all silver-gilt articles which are 
merely required to be whitened, to which we shall refer in another 
place. 



264 EliECTSO- DEPOSITION OP 8ILVEB. 

•trIpplBS Oold ftom Vim Tnrid— ot Vlattd Arttfltoa. — ^The 

sagar-bowl or other veesel is placed on a level table or benoh, and pat 
in oonneotion with the positiye electrode of a battery. A strip of 
sheet copper or platinum foil is next to be attached to the negative 
electrode, and placed inside the vessel, without touching at any point. 
By this arrangement the article becomes an anode. The vessel must 
now be filled with a moderately strong solution of cyanide of potas- 
sium, consisting of about 4 ounces of cyanide to i quart of water. 
Since the metal beneath will also dissolve in the cyanide solution, the 
operation must be stopped as soon so the gold has disappeared from 
the surface. The solution should then be poured out, and bottled for 
future use. When the stripping solution, from frequent use, has 
acquired sufficient gold to make it worth while to do so, the metal may 
be extracted by any of the processes given in another chapter. 

Old plated table candlesticks, some of which are of admirable design 
and well put together, may be occasionally met with, as also a very 
inferior article, the parts of which are mainly held together by a 
lining or *' filling " of pitch, or some resinous compound. In treating 
old plated candlesticks, the removal of the JUling should be the first 
consideration, since it will give the plater a vast amount of after 
trouble if he attempts to plate them while tiie resinous or other matter 
remains in the interior. In the first place, the silver solution will be 
sure to find its way into the hollow of the article, from which it will 
be next to impossible to entirely extract it when the article is plated, 
for the liquid will continue to slowly exude for days, or even weeks, 
after the article is finished. Again, if the article be plated without 
removing the filling material, this, being freely acted upon by the 
cyanide solution, will surely harm it. After removing the socket, the 
green baize or cloth should be removed from the base of the candle- 
stick, when it should be placed before a fire imtil the whole of the 
resinous matter or pitch has run out. To facilitate this, the article 
should be slightiy inclined in an iron tray or other vessel, so that the 
resinous matter may freely ooze out and be collected. In dealing with 
the inferior varieties of candlesticks — which may be known by aU or 
nearly aU the silver having worn from their surface — the plater may 
find, to his chagrin, that before all the stuffing has run out the candle- 
stick will have literally fallen to pieces. The various parts, not having 
been originally put together with solder, but held in position merely 
by the filling material, readily come asunder when the internal lining 
is loosened. In such a case as this he should, without losing his 
temper (if possible), determine to prepare and plate all the parts 
separately (keeping the parts of each *' stick " together), and after 
scratch -brushing, carefully put them together again. The candlestick 
should now be turned upside down, and held in this position by an 



HAND POLIBHINO. 265 

aaaiBtani, while a Biii&oient quantify of pitch (previonalj melted in an 
earthenware pipkin) is ponred in. The candleatiok must be left in 
the erect position until the filling haa nearly set, when the hoUow 
formed by the oontnotion of this sdbetanoe must be filled np with the 
same material, and the artide then left until quite cold, when it may 
be handed over to the burnisher. When burnished, the surface of the 
pitch should be levelled with a hot iron, and then at once brought in 
contact with a piece of green baize, placed upon a table, and gentle 
pressure applied to cause the uniform adhesion of the two surfttces. 
When cold, the remainder of the baize is cut away by means of a 
sharp pair of scissors, when, after being wiped with a dean or slightly 
rouged chamois leather, the article is finished. 

Band gftliahlng. — ^When the electro-plater is unproyided with a 
proper polishing lathe and the yarious appliances ordinarily used in 
polishing metals, he must have recourse to the best substitute he can 
command for polishing by hand. To aid those who may be thus cir- 
cumstanced, and who may haye no special knowledge of tlie means 
by which the rough surfaces of old work may be rendered suifidentiy 
smooth for replating, we will g^ye the following hints : Ftocure a few 
sheets of emery-doth, from numbers o to 2 indusiye ; one or two 
lumps of pumice-stone ; a piece of Water-of-Ayr stone, about { inch 
square and 5 indies long ; also a littie good rottenstone, and a small 
quantity of sweet oil. Suppose it is necessary to render smooth the 
base, or stand, of an old cruet frame, deeply marked on its plane sur- 
face by thecorroeiye, or, rather, yoltaic action of the yinegar dropping 
from the cruets upon the plated surface. The artide, after being 
stnppedj as before, should be laid upon a solid bench, and a lump of 
pumice (preyioudy rubbed flat upon its broadest part) frequentiy 
dipped in water and well rubbed over the whole surface, that is, not 
merdy where the cayities are most yidble, but all over. After thus 
rubbing for some time, the stand is to be rinsed, so that the operator 
may see how far his labour has succeeded in reducing the depth of 
the ** pit-marks." The stoning must then be resumed, and when the 
surface appears tolerably uniform, the article should be well rinsed, 
dried, and again examined, when if the marks are considerably 
obliterated, a piece of No. 2 emery-cloth may be briskly applied to 
the suiface by being placed oyer a large cork or bimg, after which a 
finer emery-cloth should be applied. The article should next be 
thoroughly rinsed, and brudied with water to remoye all particles of 
emery ; and while still wet, the Water-of-Ayr stone must be rubbed 
oyer the surface. The stone should be held in an inclined position, 
frequently dipped in water, and passed from end to end of the artide. 
The effect of this wiU be— and mmt be — to remove all the scratches or 
mad» produced by the pumice and emeiy-doth. Until these have 



266 EIAOTBO-DBFOSITION OF SILVER. 

disappeared, Uie smooth bat keenly-cutting stone must be applied. 
After having rendered the surface perfectly smooth, the article is to be 
ag^in rinsed and dried. It must now be briskly rubbed with rotten - 
stone, moistened with oil, and applied with a piece of buff, or belt 
(such as soldiers' belts are made of), glued to a piece of wood. When 
sufficiently rubbed or buffed with the rottenstone, the surface will be 
bright, and in order to ascertain how the work progresses, it should 
occasionally be wiped with a piece of rag. In very old plated articles, 
the pit-holes axe frequently so deep that to entirely obliterate them 
would render the metal so thin as to spoil the article. It is better, 
therefore, not to go too far in this respect, and to trust to the cruets, 
when in their places, disguising whateyer remains of the blemishes, 
after the foregoing treatment, rather than to endang^ the solidity of 
the stand itself. By employing pieces of pumice of various sizes 
(keeping the flattened piece for plane surfaces), strips of emery-cloth 
folded over pieces of soft wood, Water-of-Ayr stone, and ordinary 
hand ''buff-sticks" of various kinds, the ''wires'* of old cruet 
and liqueur frames may be rendered smooth enough for plating. With 
perseverance, and the necessary labour, many old articles may be put 
into a condition for plating by hand labour with very creditable 
results ; and it may be some consolation to those living at a distance 
from large towns, if we tell them that during the first ten years of the 
electro-plating art, the numerous host of " small men " had no other 
means of preparing their work for plating than those we have men- 
tioned, many of whom have since become electro-depositors upon an 
extensive scale. 

S^BUvwrliis lll«etro-plate. — ^This is quite a distinct class of ware 
from the preceding, inasmuch as the articles are manufactured from 
what is called white tnctal, in contradistinction to the basis of Sheffield 
plate, which, as we have said, is the red metal copper. The better 
class of electro-plate is manufactured from a good quality of the alloy 
known as German silver, which, approaching nearly to its whiteness, 
does not become very distinctly visible when the silver has worn from 
its surface. Inferior qualities of this alloy, however, are extensively 
used for the manufacture of cheap electro-plate, which is very little 
superior, as far as colour goes, to pale brass, while the latter alloy is 
also employed in the production of a still lower class of work. The 
comparatively soft alloy, of a greyish-white hue, called Britannia 
metaly is also extensively adopted as a base for electro-plate of a very 
showy and cheap description, of which enormous quantities enter the 
market, and adorn the shop -windows of our ironmongers and other 
dealers m cheap electro-plated goods. To determine whether an 
electro-plated article has been manufactured from a hard alloy, such as 
German silver, or from the soft alloy Britannia metal, it is only neces- 



OBAftikOTEBISTlCS OF BLECrBO-PLATE. 267 

saiy to stzike the artido with any hard substance, when a ringing, 
yilnratory sound will be produced in the former case, while a dull, 
unmusical sound, with but little vibration, will be observed in the 
latter. 

Oharaetortotles off BUoetro-Vlate. — ^Electro -plated articles of the 
best quality are invariably hard-soldered in all their parts ; the wires 
of cruet and liquor frames are attached by Grerman silver nuts to the 
screwed uprights, or feet of the wires, instead of pewter solder, as in 
plated ware, and the bottoms of the stands are coated with silver, 
instead of being tinned, as in the former case. The mounts are of the 
same material as the rest of the article, and the handles and feet of 
cream-ewers and sugar-bowls are frequently of solid cast Q«rman 
silver. With these advantages the electro -plater should have little 
difficulty, if the articles have received fair treatment in use, in re- 
plating them and turning them out nearly equal to new, which it 
should be his endeavour to do. It sometimes occurs that ' * ship plate * ' — 
that is, plated work which has been used on board ship — when it 
reaches the hands of the electro-plater exhibits signs of very rough 
usage ; comer dishes are battered and full of indentations, while the 
flat surfaces of the insides are scored with cuts and scratches, sugges- 
tive of their having been frequently used as plates, instead of mere 
receptacles for vegetables ; the prongs of the forks, too, are frequently 
notched, cut, and bent to a deplorable extent. All Uiese blemishes, 
however, must be removed by proper mechanical treatment, after 
the remaining silver has been removed by the stripping-bath. It is 
not unusual for those who contract for the replating of ship work to 
pay hy the ounce for the silver deposited, in which case they will not 
allow the electro-plater to reap the full advantage of the old silver 
removed by stripping, but will demand an allowance in their favour, 
which, if too readily agreed to by an inexperienced plater, might 
greatly diminish his profit if the cost of buf&ng the articles happened 
to be unusually heavy ; he must, therefore, be upon his guard when 
undertaking work of this description for the first time, since, other- 
wise, he may suffer considerable loss, for which the present rate of 
payment for each ounce of silver deposited will not compensate. 

After stripping and rinsing, the articles require to be well polished, 
or buffed, and rendered as nearly equal to new work as possible ; they 
are then to be potashed, quicked, plated, and finished in the same way 
as new goods. Since there is now a vast quantity of nickel-plated 
work in the market, some of which is exceedingly white even for nickel, 
inexperienced or weak-sighted platers must be careful not to mistake 
such articles for silver-plated work. When in doubt, applying a single 
drop of nitric acid, which blackens silver while producing no imme- 
diate effect upon nickel, will soon set the mind at rest upon this point. 



268 BLBOTBO-DBPOSmOK OF SlLYltfi. 

Electro-tiimed artaoleB, which very mndh reaemble silvered work, may 
also be detected in this way. We are tempted to make one other 
BQggestion upon this subjeot, which may not be deemed out of place, 
it is this: a considerable quantity of nickel-plated German silyer 
spoons and forks are entering the market, which, should they eventoaUy 
fall into the hands of the electro-plater to be coated with silver, may 
cause him some trouble if he inadvertently treats them as German 
silver work, which in his haste he might possibly do, and attempts to 
render them smooth for plating by the ordinary methods of hand or 
lathe-buffing ; the extreme hardness of nickel — even as compared with 
German silver — ^wiU render his work not only laborious, but unne- 
cessary, for if he were aware of the true nature of the surface he 
would naturally remove the nickel by means of a stripping solution, 
and then treat the article as ordiuary German silver, work. The 
stripping solution for Hiis purpose wOl be given when izeating of 
nickel rtf-plating. It must be understood that in making sugg^estions 
of this nature, in passing, that they are intended for the guidance of 
those who may not have had the advantages of much practical expe- 
rience, of whom there are many in every art. 

D«positliis 8iiv«r by UtTclglit. — In this counlzy the silver deposit 
is frequently paid for by weight, the articles being carefully weighed 
both before and after being placed in the plater's hands. The price 
charged for depositing silver by the ounce was formerly as high as 
14s. 6d. ; at the present period, however, about 8s. per ounce only 
could be obtained, and in some cases even less has been charged. But 
unless dynamo-electricity be employed this would be about as profitable 
as giving ten shillings for half-a-sovereign. In France electro-plating 
is regulated by law, all manufacturers being required to weigh each 
article, when ready for plating, in the presence of a comptroller 
appointed by the Grovemment, and to report the same article for 
weighing again after plating. In this way the comptroller knows to 
a fraction the amount of precious metal that has been added, and puts 
his mark upon th& wares accordingly, so that every purchaser may 
know at a glance what he is buying. In Birmingham there is a class 
of electro-depositors called ** electro-platers to the trade," who work 
exclusively for manufacturers of plated g^ds and others who, though 
platers, send a great portion of their work to the *' trade" electro - 
platers, whose extensive and more complete arrang^^nents enable 
them to deposit larg^ quantities of the precious metals with consider' 
able economy and dispatch. 

In depositing silver at so much per ounce, the weighed articles, 
after being cleaned, quicked, and rinsed, are put into the bath, in 
which they are allowed to remain until the plater deems it advisable 
to re-weigh them, when they are removed from the bath, rinsed in 



DXP081TINO 8ILVBB BT WBiaBT. 269 

hot water, and placed in boxwood aawduafc ; they are then lightly 
bmahed oyer to zamoye any sawdmit that may adhere to them, and 
carefully weighed. If still insufficiently coated the articles are again 
scratch-brushed, quicked, rinsed, and replaced in the bath ; the re- 
weighing and other operations being repeated as often as is necessary 
until the required deposit is obtained. This is a tedious and trouble- 
some method, and is sometimes substituted by the following : Suppose 
a certain number of spoons and forks have been weighed for the 
plating-bath, one of these articles is selected as a test sample, and is 
weighed separately ; being placed in the bath with the others, it is 
remoYcd from time to time and re- weighed, to determine the amount 
of silver it has acquired in the bath. Thus if 24 dwts. of silver are 
required upon each dozen of spoons or forks, when the test sample 
has received about 2 dwts. of silver it is known that the rest have 
a like proportion, provided, of course, that each time it has been 
suspended in the bath the sUng^g wire and that part of the conduct- 
ing rod from which it was suspended were perfectly clean ; it is 
obvious, however, that even this method is open to a certain amount 
of doubt and uncertainty, if the workmen are otherwise than very 
careful. To render the oi>eration of depositing by weight more certain 
and less troublesome, some electro-platers in France adopt what is 
termed a ** plating balance." The articles are suspended from a frame 
connected to one end of the beam, and a scale pan, with its weights 
from the other end ; the balance, thus arranged, is placed in communi- 
cation with the negative electrode of the electric generator, and the 
anodes with the positive electrode. When the articles, as spoons and 
forks, for example, are suspended from the frame, and immersed in 
the bath, counter-balancing weights are placed in the scale-pan. A 
weight equivalent to the amount of silver to be deposited is then put 
into the pan, which, of course, throws the beam out of balance ; when 
the equilibrium becomes restored, by the weight of deposit upon the 
articles in solution, it is known that the operation is complete. The 
plater usually employs scales for each bath, especially when silvering 
spoons and forks. If preferred, the supporting frame may be circular, 
so that the soluble anode may be placed in the centre of the bath, and 
at equal distance from the articles. The centre anode need not prevent 
the employment of other anodes round the sides of the vessel, so that 
the articles receive the action of the current in front and behind them. 
A sounding bell may be so connected that it will indicate the precise 
moment when the equilibrium of the scale takes place. In working 
the silver baths for this purpose, the anode surface immersed in solu- 
tion is much greater than that of the articles. When the solution 
loses its activity additions of cyanide of silver are given to it, and 
when the cyanide is found to have become partially converted into 



3fO XLEOTBO- DEPOSITION OT SILTER. 

ottrboiiAte of potaasa, hydrooyBmo aold Ib added, which combinefl witb 
oarbonate, and. liberstea oarboma acid gaa. This method is prefened 
to that of adding freiih cyanide, since an accumulation of the car- 
bonated alkali retards the conductirity of the solution, as also doea 
the hydrocyanic acid when added in ciceSB. 

ila.— This 18 an antomatic apparatus 
and is desired for 
obtaining deposits of 
silver "without supv- 



accuracy, and which 
spontaneously loailu the 
electric current when the 
operation is terminated . " 
The apparatus is made 
in TarioOB sizes, suitable 
for small or large opera- 
tions; Fig. 98 repre- 
aenle the apparatus to 
be en^loyed for the 
lattel purposes. 

It consists of: — i. A 
wooden vat, Qio upper 
ledge of which carries a 
brass winding rod. hav- 
ing a binding screw at 
one end to receive die 
poutive conducting wire 
F'B' ^- of the battery ; from 

this rod the anodes are 
snspenoed, which ore entirely immersed in the solation, and commu- 
ntcate with cross brass rods by means of platinum wire hooks. These 
urosa rods are flattened at their ends so that thoy may not roll, and at 
the same time have a better contact with the "winding rod." I. A 
caat-iron column screwed at its base to one of the sides of the baih, 
carriee near the top two projecting arms of cast iron, the extremitJee 
of which are vertical and forked, and may be opened 01 closed by iron 
clamps, these forks bein^ intended to maintain the beam and prevent 
the knives from leaving their bowls when the beam oscillatea too 
greatly. In the middle of the two arms are two bowls of polished 
steel, hollowed out wedge-shaped, to receive the beats knives. One 
arm of the pillar has at ita end a horizontal iron ring, in which is 
ftxed a heavy glass tube which supports and insulates a polished iron 
ono to contain meronry ; beneath this cnp is a small pad of India- 



ABGYBOMBTBIO 80ALB. Tjl 

mbber, which, by means of a screw beneath, may be raised or lowered, 
by which means the mercury in the cup is levdled. A second lateral 
binding screw connects the negative electrode of the batteiy. 3. A 
cast-iron beam, carrying in its centre two sharp polished steel knives ; 
at each end are two parallel steel bowls, separated by a notch, intended 
for the knives of the scale pan and of the frame for supporting the 
articles. One arm of the beam is furnished with a stout platinum 
wire, placed immediately above and in the centre of the mercury cup, 
and as the beam oscillates it dips into, or passes out of, the cup. 
The scale pan is furnished with two cast-steel knives fixed to the 
metallic bar, which is connected to chains supporting the lower 
wooden box for the tare ; the smaller pan, for the weight representing 
the amount of sQver to be deposited, is placed between these two. 
4. The frame for supporting the work is also suspended by two steel 
knives, the vertical of which is of stout brass tubing, and is equal in 
size to the opening of the bath, and supports the rods to which the 
articles are suspended. The slinging wires are formed into a loop at 
one end for supporting the spoons or forks, and the vertical portion of 
each wire is covered with india-rubber tubing, to prevent it from 
receiving the silver deposit. 

In adjusting the apparatus, the pillar must be set perfectly upright 
by aid of a plumb line ; the clamps are then withdrawn from the 
forkSf and the beam is carefully put in its place, care being taken to 
avoid injuring the knives that rest in the bowls in the centre of the 
pillar. The clamps are now replaced, and the beam should oscillate 
freely upon the knives without friction. The knives of the frame are 
next put in their places, as also those of the scale pan ; mercury is 
then poured into the six bowls, where the knives rest, until all the 
polished parts of the latter are covered. The insulated steel cup is 
then filled with mercury so high that the point of the platinum wire 
just touches it, when the beam is level ; the small elastic pocket is 
used for raising and lowering the mercury cup, so as to place it at the 
proper height for bringing the mercury in contact with the end of the 
platinum wire. When the articles have received the amount of silver 
corresponding to the weight in the pan at the opposite side of the 
beam, the equilibrium 'will be established, and the platinum wire will 
then leave the mercury, and thus break the circuit and stop the opera^ 
tion. By this automatic arrangement the operation needs no atten- 
tion, since the moment tiie platinum wire loses contact with the 
mercury electricity ceases to pass ; if, however, the articles are allowed 
to remain in the bath after they have received the proper amount of 
silver, a portion of this metal may be dissolved by the free cyanide in 
the solution, in which case the end of the platinum wire would again 
dip into the mercury and complete the circuit, when deposition would 



27* BLEOTBO-DBPOSinON OF SIL7BB. 

be renewed and oontdniie untQ the inoreased weight of sUtst again 
caused the platinum wire to lose contact with the meroury. 

solid flUver Deposits. — ^Although it is possible to deposit silver, 
from a cyanide solution rich in metal (say eight oxmces of sQver per 
gallon), upon wax or gutta-percha moulds, this method is not practi- 
cally adopted. The usual method is to first obtain a copper electro- 
type mould or shell of the object in the ordinary way ; silver is then 
deposited within the mould (supposing it to be a hollow object) until 
of the required thickness ; the copper is afterwards dissolved from the 
aQver either by boiling the article in hydrochloric acid, or, still better, 
a strong solution of perchloride of iron, either of which substances 
will dissolve the copper mould without in anyway injuring the silver. 
The perchloride of iron for this purpose may be readily formed by 
dissolving peroxide of iron (commercial *' crocus") in hot hydro- 
chloric acid. The method of dissolving the copper recommended by 
Napier, is as follows : " An iron solution is first made by dissolving 
a quantity of copperas in water ; heat this till it begins to boil ; a 
little nitric acid is then added — ^nitrates of soda or potash will do ; the 
iron which is thus peroxidised may be precipitated either by ammonia 
or carbonate of soda ; the precipitate being washed, muriatic acid is 
added till the oxide of iron is dissolved. This forms the solution for 
dissolving the copper. When the solution becomes almost colourless, 
and has ceased to act on the copper, the article is removed, and the 
addition of a litUe ammonia will precipitate the iron along with a 
portion of the copper ; but after a short exposure the copper is redis- 
solved. The remaining precipitate is washed by decantation ; a little 
ammonia should be put into the two first waters used for washing. 
When washed, and the copper dissolved out, the precipitate is redis- 
Bolved in hydrochloric acid, and the silver article returned until the 
copper is all dissolved off. It is convenient to have two solutions of per- 
chloride of iron, so that while the iron in the one is being precipitated, 
the article is put into the other. The persalt of iron will be found to 
dissolve the copper more rapidly than muriatic acid alone ; persul- 
phate of iron must not be used, as it dissolves the silver along with 
the copper. 

'* The silver article is now cleaned in the usual way, and heated to 
redness over a clear charcoal fire, which gives it the appearance of 
dead silver, in which state it may be kept, or, if desired, it may be 
scratched and burnished.*' A very simple and economical method of 
producing perchloride of iron is to reduce the native peroxide of iron, 
known as ** redding," to a powder, and digest it in hot hydrochloric 
acid, by which the salt is obtained at a cost but little exceeding that 
of the acid employed, the native ore being worth only about 25s. per 
ton. 



THI0XKBB8 OF SLBOTBODBPOfllTED 8ILVBB. 273 

One great objection to solid eleotro-depoeits of silver (and gold) is 
that the articles have not the metallic ** ring,'* when strack with any 
hard substance, as silyer ware of ordinary manufacture. ''This 
disadvantage, *' says Napier, '< is no doubt partly due to the crystalline 
character of the deposit, and partly to the pure character of the silver, 
in which state it has not the sound Uke standard or alloyed silver. 
That this latter cause is the principal one appears from the fact that 
a piece of silver thus deposited is not much improved in sound by 
being heated and hanmiered, which would destroy all crystallisation." 
This is quite true, but when electro -deposited silver has been melted^ 
and cast into an ingot, by which its crystalline character is completely 
destroyed, and which is only partially affected by simply annealing 
and hammering, the characteristic '* ring ** of the pure metal is re- 
stored. The absence of a musical ring in electro-deposited silver is 
not of much consequence, however, since this method of reproduction 
would only be applied to raro works of art, such as antique figures, 
and richly chased articles kept solely for ornament. 

On thm Tlilnlrm— of Bl«etro-]>«po«ited StlTcr. — ^This may be 
considered a somewhat delicate theme to expatiate upon when we 
reflect that some articles of commerce, but niore especially export 
g^oods and articles sold at mock auctions, frequently receive a coating 
of silver which not only defies measurement by the most delicate 
micrometer, but also renders estimation by any other means all but 
impossible. This class of work includes spoons and forks, cruet- 
frames, toast-racks, &c., manufactured from a very inferior descrip- 
tion of Gkrman silver or brass, while Britannia metal tea services, 
salt-cellars, and many other articles made from the same alloy enter 
the market in enormous quantities, with a mero blush of silver upon 
them, the thickness of which might be more readily estimated by 
imagination than by any practical test. As to the amount of silver 
which should be deposited upon articles of domestic use, to enable 
them to withstand ordinary wear and tear for a reasonable x>eriod, 
from I to 3 ounces per dozen for spoons and forks may be deposited. 
Taken as a guide, with the smaller quantity of silver upon them, such 
articles, with careful usage, should present a very creditable appear- 
ance after five years' use ; with the larger proportion, the articles 
should look well, though probably somewhat bare upon those parts 
most subject to friction, at the end of twenty years. The same arti- 
cles, if used in hotels or on board ship, would become imsightly in 
less than half the periods named. German silver tea and coffee 
services, to be fairly well plated or silvered, should not have less than 
2 ounces of silver upon the four pieces, which may be distributed in 
about the following proi)ortions : for a 5 -gill coffee-pot 12 dwts. ; 
5 -gill teapot 12 dwts. ; sugar ^basin 10 dwts. ; cream-ewer 6 dwt8. 



274 EliBOTBO-DBPOSITION OP SILVBB. 

When the same articles are required to he fully well plated, the pro- 
portions should be about as follows : For coffee and teapot, about 
i^ ounce of silver each ; sugar-basin i ounce, and cream-ewer about 
10 to 15 dwts. 

The proportion of silver which should be deposited per square foot, 
for plating of good quality, is from i to i^ ounce. With the latter 
proportion the electro-silvered work would nearly approach in quality 
the old Sheffield plate, and would last for a great number of years 
without becoming bare, even at the most prominent parts, unless the 
article were subjected to very severe treatment in use. 

Fyro-plAttni;. — It is well known that when a silver-gilt article — ^as 
a watch-chain, for example — ^hasbeen broken, and afterwards repaired 
by hard soldering, that the film of gold almost entirely disappears 
from each side of the soldered spot, under the heat of the blow-pipe 
flame, to the extent of i or 2 inches on either side of the joining. The 
film of gold has, in fact, sunk into the body of the silver, as though 
it had become alloyed with this metal. By some persons this is really 
believed to be the case. We are, however, disposed to think that the 
absorption of the gold under these circumstances is due, not to an 
actual alloying of the two metals in the ordinary sense, but to the 
expansion of the silver by the heat, by which its molecular structure 
becomes disturbed, and the film of gold, being thus split up into 
infinitely minute particles, these become absorbed by the silver as the 
metal contracts on cooling, and consequently disappear from the sur- 
face. We hold this view because we do not think that the heat of the 
blowpipe fiame required to fuse the solder would be sufiScient to form 
an aUoy in the proper sense ; indeed, the heat required to **run '| 
silver solder would not be sufficienUy high even to '* sweat " the silver 
of which the article is composed. The fact of a film of metal becom- 
ing absorbed by another metal under the influence of heat has been 
taken advantage of, and a process termed ^* pyro-plating " has been 
introduood, and has been worked to some extent in Birmingham. The 
process, which has been appUed to coating articles — of steel and iron 
more especially — with gold, silver, platinum, aluminium, copper, &c., 
may be thus briefly described : The article is first steeped in a boUing 
solution of caustic potash ; it is then brushed over with emery- 
powder, and afterwards with a steel brush and a solution of common 
soda, in which it is allowed to remain for some time. It is next con- 
nected to the negative electrode of a strong battery, and immersed in 
a hot solution of caustic potash, abundance of hydrogen being evolved, 
and is allowed to remain until it has a *' silvery ^* appearance. After 
rinsing, it is suspended in a silver bath, with a previously weighed melal 
plate of the same amount of surface placed as a cathode by its side ; 
this plate ic taken out and weighed from time to time until sufficient 



WHlTENtKa StLVEil WOM. 27 j 

silver Las been deposited, T^hich indicates approximatelj the amount 
of deposit upon the article itself. The article is then removed and 
rinsed, and afterwards heated in a furnace until the silver is ^* driven" 
into the surface of the metal. If the steel article requires to be tern' 
pered, it is quenched in water, and then brought to the proper temper 
in the usual way. 

'Wbitoniiis Btoetro-platad Artieltts. — It is well known that 
articles which have been electro -plated tarnish more rapidly than 
silver goods ; and while this has by many persons been attributed to 
the extreme purity of the electro-deposited metal, which, it was 
believed, was more susceptible of being attacked by sulphurous fumes 
and other impurities in the air, by others it is believed to be due to a 
small quantity of undecompoeed salt remaining in the pores of the 
deposited metal, which undergoes decomposition, and causes the work 
to tarnish. In order to render electro-plate less liable to discolora- 
tion, the following method has been adopted, but, as will readily be 
seen, it could not be applied to all classes of work : The article is first 
dipped in a saturated solution of borax and then allowed to dry, when 
a thin layer of the salt remains upon the surface ; the article is then 
dipped a second or even a third time (drying after each dipping) until 
it is completely covered with a layer of borax. When large articles 
are to be treated this way, the borax may be applied with a soft 
brush. The article is next to be heated to a dull red heat, or until 
the hoTSJi fuses. When cold, it is to be put into a pickle of dilute sul- 
phuric acid, which rapidly dissolves the borax ; after rinsing iu hot 
water it is placed in hot boxwood sawdust, and then treated in the 
usual way. 

'Wbitanins BUver TRTork. — ^Articles of silver which in their original 
finished state were left either wholly or in part a dead white, and have 
lost this pleasing effect by wear or oxidation, may be restored to their 
original condition by the process termed whitening. The article is first 
brought to a dull red heat (not sufficiept to melt the solder) over a 
charcoal fire — if it be a brooch, watch-dial, or other small silver 
article, by means of the blowpipe flame, the article being placed on a 
large and flat piece of charcoal. When the piece of work has thus 
been heated uniformly all over, it is allowed to become cool, after 
which it is placed in a glazed earthenware vessel (an ordinary white 
basin wiU do), containmg a sufficient quantity of very dilute sulphuric 
acid. In a short time the acid will dissolve the oxide from the surface, 
together with a smaU quantity of oxide of copper derived from the 
copper with which the silver was alloyed, and which, with the silver, 
becomes oxidised by the heat and subsequent action of the atmosphere. 
When the article is removed from the pickle — in which it should 
rsmein for at least twenty minutes to half an hour — if not of a suffi- 



2f6 )SLEGTltO-D£POSITION OF SILVfiB. 

oiently pure whiteness it may be heated and pickled again. When 
the whitening is properly effected, the surface should present a beauti- 
ful pearl-white appearance, and be perfectly uniform in its lustrous 
dulness. Directly the article is removed £rom pickle, it should be 
rinsed in two sex)arate waters, the last water (which should be 
distilled water, by preference) being boiling hot. The article, after 
bdng removed from the rinsing -bowl, should be allowed to dry spon- 
taneously, which it will do if the water is boiling hot. It is not a 
good plan, though it is frequently done, to put work which has been 
whitened in boxwood sawdust, since if it has been much used it Im 
liable to produce stains. 



CHAPTER XVII. 

IMITATION ANTIQUE SILVER. 

Oxidised Silver.— Oxidising Silver.— Oxidising with Solution of Platinum.— 
Oxidising with Sulphide of Potassium. — Oxidising with the Paste.— 
Part-gilding and Oxidising.— Dr. Eisner's Process.— Satin Finish.— Sul- 
phuring Silver.— Niello, or Nielled Silver.— Pink Tint upon Silver.— 
Silvering Notes. 

OilrtI— d BHwtae, — Soon after the art of electro-plating had become 
an establiahed industry, the great capabilities of the ** electro " pro- 
oefls, as it was called, received the serious attention of the more gifted 
and artistic members of the trade, who, struck with the great beauty 
of electro -deposited silver, and the facilities which the process offered 
for the reproduction of antique works, induced some electro-platers of 
the time to make experiments upon certain classes of work with a view 
to imitate the effects seen upon old silver ; some of the results were 
highly creditable, and in a short time after '' oxidised " silver became 
greatly in vogue, and has ever since been recognised as one of the 
artistio varieties of ornamental silver or electro-plated work. We 
Boaroely think we shall err, however, if we venture to say that much 
of the ''oxidised ^' silver-plated work of the present time is far inferior 
in beauty and finish to that with which our shops and show-rooms 
were filled some thirty years ago. Indeed, when visiting the Paris 
Exhibition of 1878, we were much displeased with the very slovenly 
appearance of some of the plated goods which had been part-gilt and 
oxidised in the exhibits of some of the larger English and French 
firms. The specimens referred to had the appearance of having done 
duty as specimens in all the exhibitions since 1851, and had suffered 
by being repeatedly '' cleaned up *' for each occasion ; they were cer- 
tainly far from being creditable. 

" Ozldlaiiis " SllT«r. — This term has been incorrectly appUed, but 
universally adopted, to various methods of darkening the surface of 
silver in part8, by way of contrast to burnished or dead-white sur- 
faces of an article. Oxygen, however, has little to do with the 
discoloration, as will be seen by the following processes, which are 
employed to produce the desired effect. The materials used are various, 
and they arc generally applied with a soft brush, a camel-hair brush 



2'jS IMITATION ANTIQUE 6ILYEB. 

being suitable for small surfaces. In applying either of the materials 
the article should be quite dry, otherwise it will spread oyer portions 
of the work required to be left white, and thus produce a patchy and 
inartistic effect. The blackening substances are generally applied to 
the hollow parts or groundwork of the object, while the parts which 
are in relief are left dead, or burnished according to taste. 

Ozidlsliis wltb flotation of Plattnum. — Dissolve a sufficient 
quantity of platinum in aqua regia, and carefully evaporate the result- 
ing solution (chloride of platinum) to dryness, in the same way as re- 
commended for chloride of gold. The dried mass may then be dissolved 
in alcohol, ether, or water, according to the effect which it is desired 
to produce, a slightly different effect being produced by each of the 
solutions. Apply the solution of platinum with a camel-hair brush, and 
repeat the operation as often as may be necessary to increase the depth 
of tone ; a single application is frequently sufficient. The ethereal or 
alcoholic solution of platinum must be kept in a well- stoppered bottle, 
«uid in a cool place. The aqueous solution of platinum should be 
applied while hot. 

Oaddkting wltb flol^lilde of Potaoaliiiii. — ^Liver of sulphur (sul- 
phide of potassium) is often used for producing black discoloration, 
enoneously termed oxidising. For this purpose four or five grains of 
the sulphide are dissolved in an ounce of hot water, and the solution 
applied with a brush, or the article wholly immersed if desired. The 
temperature of the solution should be about 1 50° Fahr. After a few 
moments the silver surface assumes a darkened appearance, which 
deei)ens in tone to a bluish-black by long^ treatment. When the 
desired effect is produced the article is rinsed and then scratch -brushed, 
or burnished if required, or the blackened hollow surfaces are left dead 
according to taste. When it is desired to produce a dectd surface upon 
an article which has been electro-silvered, the article may be placed 
in a sulphate of copper bath for a short time, to receive a slight coat- 
ing of copper, after which it is again coated with a thin film of silver 
in an ordinary cyanide bath. It has then the dead- white appearance 
of frosted silver. Where portions of the article are afterwards oxidised 
a very fine contrast of colour is produced. In using the sulphide of 
potassium solution it should be applied soon after being mixed, since 
it loses its activeness by keeping. Fresh solutions always gpive the 
most brilliant results. Since the sulphide dissolves the silver, it is 
necessary that it should be applied only to surfaces which have received 
a tolerably stout coating of this metal, otherwise the subjacent metal 
(brass, copper, or German silver) will be exposed after the sulphide 
solution has been applied. 

Ozidistns with ttie Paste. — ^For this purpose a thin paste is formed 
by mixing finely-powdered plumbago with spirit of turpentine, to 



OXIDISING PB0C1S88S8. 279 

wLioh mixture is rometimes added a small quantity of red obhre or 
jewellers' rouge, to imitate the warm tone sometimes observed in old 
silvor articles. The paste is spread over the articles and allowed to 
dry, after which the article is brushed over with a longc-haired soft 
brush, to remove all excess of the composition. The parts in relief 
are then cleaned by means of a piece of rag, or chamois leather, dipped 
in spirit of wine. This method of imitating old silver is specially 
applicable to vases, tankards, chandeliers, and statuettes. In case of 
failure in the manipulation, the dried paste may be readily removed 
by placing the article in a hot solntion of caustic potash or cyanide, 
when, after rinsing and drying, the paste may be reapplied. To give 
the old silver appearance to small articles, such as buttons, for example, 
they are first passed through the above paste, and afterwards revolved 
in a barrel or <* tumbler " containing dry sawdust, until the desired 
effect is produced. 

Part-gllrting and Ozldlaliiff. — To give this varied effect to work, 
the articles are first g^t all over in the usual way ; certain parts are 
then stopped off^ as it is termed, by applying a suitable varnish. When 
the varnish has become dry, the article is placed in the silvering bath 
until a sufficient coating, which may be slight, has been obtained. 
After rinsing, the object is immersed in a solution of sulphide of 
potassium until the required tone is given to the silvered parts, when 
the article is at once rinsed, carefully dried, and the protecting varnish 
dissolved off, when it is ready to be finished. 

Br. BlflnWa Piuue—  — ^A brownish tone is imparted to plated 
goods by applying to the surface a solution of sal-ammoniac, and a 
still finer tone by means of a solntion composed of equal parts of 
sulphate of copper and sal-ammoniac in vinegar. To produce a fine 
black colour. Dr. Eisner recommends a warm solution of sulphide of 
potassium or sodium. 

flnlplilda of Aminonlnni. — This liquid may also be applied to the so- 
called oxidation of silver, either by brushing it over the parts to be 
oxidised, or by immersion. It may also be applied, with plumbago, 
by forming a thin paste with the two substances, which is afterwards 
brushed, or smeared over the surface to be coloured, and when dry a 
soft brush is applied to remove the excess of plumbago. If preferred, 
a littie jewellers' roug^e may be added to the mixture. 

Satin Flnlali. — ^This process is thus described by Wahl : The sand- 
blast is in use in certain establishments to produce the peculiar dead, 
lustrous finish, known technically as tatin Jlnish^ on plated goods ; a 
templet of some tough resistant material, like vulcanised india-rubber, 
is made of the proper design, and when placed over the article, pro- 
tects the parts which it is desired to leave bright from the depoHshing 
aotiaa of the sand, while the only open portions of the templet are 



2So IMITATION ANTIQUE BILVEIt. 

exposed to the blast. The apparatoB employed for this pmpoee oon* 
sists of s wooden hopper, with a longitudinal slit below, through 
which a stream of fine sand is allowed to fall, by opening a sUding 
cover. Closely surrounding the base of the hopper is a rectangular 
trunk of wood, extending some distance below the base of the hop- 
per, and tapering towards the bottom, to concentrate the sand- jet. 
This trunk is closed about the sides of the hopper, and open below, 
and is designed to direct the stream of sand upon the surface of the 
article presented beneath its orifice. To increase the rapidity of the 
depolishing action of the sand, a current of air, under regulated pres- 
sure, is admitted into the upper part of the trunk, which, when the 
sand-valve is opened, propels it with more or less accelerated velocity 
upon the metallic surface below. For this purpose, either a '* blower," 
or an air-compressor with accumulator, may be used : and the pressure 
may be regulated at will. The sand is thus driven with more or less 
velocity down the trunk by the air-blast admitted above, and, falling 
upon tiie surface of the article presented at the bottom, rapidly 
depolishes the exposed parts, while those protected by the templet are 
not affected. The articles are presented at the orifice of the trunk by 
the hands of the operator, which are suitably protected with gloves ; 
and as rapidly as the depolishing proceeds, he turns the artide about 
till the work is done. The progress of the work is viewed through a 
glass window, set in a horizontal table, which surrounds the apparatus 
and which forms the top of a large box, into which the sand falls, and 
which is made tight to prevent the sand from flying about. A portion 
of this box in front, where the workman stands, is cut away, and over 
the opening is hung a canvas apron, which the operator pushes aside 
to introduce the work. The sand that accumulates in the box below 
is transferred ag^in to the hopper, as required, and is used over and 
over again. The satin-finish produced by the sand-blast is exceed- 
ingly fine and perfectly uniform, and the work is done more rapidly 
than with the use of brushes in the usual way. 

Snlplitixliitf flXhnr. — ^A very fine blue colour, resembling *' blued '* 
steel, may be imparted to silver or plated surfaces, by exposing the 
article to the action of sulphur fumes. For this purpose, the article 
should be suspended in an air-tight wooden box ; a piece of slate or 
a flat tile is laid upon the bottom of the box, and upon this is placed 
an iron tray, containing a small quantity of red-hot charcoal or 
cinders ; about a teaspoonful of powdered sulphur is now quickly 
spread over the glowing embers, and the lid of the box immediately 
closed. After about a quarter of an hour, the lid may be raised (care 
being taken not to inhale the sulphur fumes) and the article promptly 
withdrawn ; if the article is not sufficiently and unifonnly blued, 
it must be again suspended and a fresh supply of hot ohaix)oal and 



NIELLO, OR NDSLLED 8ILVEB. 38 Z 

solphiir introduced. It is iieoesaarj that the articles to be treated in 
this way should be absolutely clean. 

SleUo, or wummd SItvir. — ^These terms* are applied to a process 
which is attributed to Maso Finniguerra, a Florentine engraver of the 
fifteenth century, and somewhat resembles enamelling. It consists, 
essentially, in inlaying engraved metal surfaces with a black enamel, 
being a sulphide of the same metal, by which very pleasing effects are 
produced. The * ' nielling *' composition may be prepared by malring 
a triple sulpliide of silver, lead, and copper, and reducing the resulting 
compound to a fine powder. The composition is made as follows : A 
certain proportion of sulphur is introduced into a stoneware retort, or 
deep crucible. In a second crucible, a mixture of silver, lead, and 
copper is melted, and when sufficientiy fused the alloy thus formed is 
added to the fused sulphur in the first vessel, which converts the 
metals into sulphides ; a small quantity of sal-ammoniac is then 
added, and the compound afterwards removed from the retort or cru- 
cible and reduced to a fine powder. The following proportions are 
given by Mr. Mackenzie : — 

Put into the first crucible — 

Flowers of salphnr 750 psrts. 

Sal-ammoniac 75 9 

Put into tiie second crucible— 

Silver 15 parti. 

Copper 40 „ 

Lead 80 „ 

When fused, the alloy is to be added to tlie contents of the first 
crucible. Boseleur recommends diminishing the proportion of lead, 
which impairs the blue shade of the nielling, and corrodes too deeply. 

To apply the powder, obtained as above, it is mixed with a small 
quantity of a solution of sal-ammoniac. After the silver work is en- 
gfraved, the operator covers the entire surface with the nielling compo- 
sition, and it is then placed in the muffle of an enamelling furnace, where 
it is left until the oompomtion melts, by which it becomes firmly 
attached to the metal. The nieUing is then removed from the parts in 
relief, without touching the engraved surfaces, which then present a 
very pleasing contrast, in deep black, to the white silver surfaces. 
This process, however, is only applicable to engpraved work. 

Wahl describes a cheaper process of nielling, which consists ** in 
engraving in relief a steel plate, which, applied to a sheet of silver, 
subjected to powerful pressure in a die, reproduces a faithful copy of 
the engraving. The silver sheet thus stamped is ready to receive the 

* The art was formerly called working in nie^o^ 



282 IMITATION ANTIQUE 8IL^*£R. 

nielling. A larg® nnmber of copies may be obtained from the same 
mahr^. Such is the method by which a quantity of nielled articles are 
manufactured, as so-called Russian snuff-boxes, cases for spectacles, 
bon-bon boxes, &c. 

Roseleur suggests the following to produce efPectJ? similar to niel- 
ling : A pattern of the design, cut out of thin paper, such as lace 
paper, is dipped into a thin paste of nielling composition, or into a con- 
centrated solution of some sulphide, and then applied upon the plate 
of silver, which is afterwards heated in the muffle. The heat destroys 
the organic matter of the paper, and a design remains, formed by the 
composition which it absorbed. 

A solution of chloride of lime (bleaching powder) will blacken the 
surface of silver, as also wHl nitric acid. For all practical purposes, 
however, chloride of platinum and weak solutions of the sulphides 
before mentioned will be found to answer very well if applied with 
proper judgment. 

Pink Tint npon BUver. — Feam recommends the following for pro- 
ducing a fine pink colour upon silver : Dip the cleaned article for a 
few seconds in a strong hot solution of chloride of copper, then rinse 
and dry it, or dip it in spirit of wine and ignite the spirit. 

BUvarlns Ifotes. — i. The anodes, if of rolled silver, shonld always 
be annealed beforo using them. This may easily be done by placing 
them over a clear charooal, or even an ordinary dear fire, until they 
acquire a cherry-red heat: when cold, they are ready for use. If 
convenient to do so, it is a good plan to hard solder a short length of 
stout platinum wire (say about three inches long) to the centre of one 
edge of the anode, which may be united to the positive electrode of 
the battery, or other source of electricity, by a binding scrow, or by 
pewter solder. The object of attaching Uie platinum wire is to enable 
the anode to be wholly immersed in the bath, and thus prevent it from 
being cut thi'wtgh at the water lincy which is generally the case where 
anodes aro only partially immersed. 

2 . TFbm Anodes. — ^When the anodes have been long in use, their edges 
frequently become rotgged^ and if these irregularities are not removed 
fragments of the metal will fall into the bath, and, possibly, upon the 
work, causing a roughness of deposit. It is better, therefore, to trim 
the edges of anodes whenever they become thin and present a ragged 
appearance. 

3. Precautions to be Observed when Filling the Bath with Work, — ^Assum- 
ing the suspending rods to have been cleaned, the battery connections 
adjusted, and the preparation of the articles to be plated commenced, 
some means must be adopted to prevent the articles Jirst put into the 
bath from receiving too quick a deposit while others are being got 
ready. In the first instance, the full force of the current must be 



SILVEBINO NOTES. *°3 

checked, wbidb may be done by exposing a small surface of anode in 

solution or suspending a plate of brass or a small silver anode as a 

" stop," or oheck, to the negative rod, untQ a sufficient number of 

articles (say spoons or forks, for example) have been suspended, when 

the stop may be removed and the remamder of the articles immersed 

until the conducting rod is full ; the rest of the suspending rods 

should then be treated in the same way. When magneto or dynamo- 

electrio machines are employed, the full strength of the current is 

checked by the employment of the reaiatanee coil, a description of 

which will be found fa Chapter III. A dmple way of diminishing the 

amount of current, when filling the bath with work, is to inteipoae 

a thin iron wire between the podtive electrode and the suspending 

rod, which must be removed, however, when the cathode surface 

(the articles to he plated) m the bath approaches that of the anode 

surface. 

4. Plating Different Met ah at the Same Time. — ^It is not good practice 
to place articles composed of different metals or alloys indiscriminately 
in the bath, since they do not all receive the deposit with equal facility. 
For example, if two articles, one copper or brass, and another Britannia 
metal or pewter, be immersed in the solution simultaneously, the 
former will at once receive the deposit of silver, while the latter will 
scarcely become coated at all, except at the extremities. Since the 
best conductor receives the deposit most freely, the worst conductor 
(Britannia metal, pewter, or lead) should first be allowed to become 
completely coated, after which copper or brass articles may be intro- 
duced. It is better, however, if possible, to treat the inferior con- 
ductors separately than to run the risk of a defective deposit. 

5 . ExeeM of Cyanide. — ^When there is a large excess of cyanide in the 
plating bath, the silver is very liable to strip, or peel off the work 
when either scratch-brushed or burnished ; besides this, the anodes 
become dissolved with greater rapidity than is required to merely 
keep up the proper strength of the bath, consequently the solution 
becomes richer in metal than when first prepared. The depositor 
must not confound the terms "free cyanide" with "excess" of 
cyanide : the former refers to a small quantity of cyanide beyond that 
which is necessary to convert into solution the precipitate thrown down 
from the nitrate, which is added to the solution to act upon and 
dissolve the anode while deposition is going on ; the latter term may 
properly be applied to any quantity of cyanide which is in excess of 
that which is necessary for the latter purpose. 

In preparing plating solutions from the double cyanide of silver 
and potassium, great care must be taken, when precipitating the 
nlver from its nitrate solution, not to add the cyanide 'ji excess, other- 
wise a portion of the precipitated cyanide of sH^or will be ro-dissol ved, 



284 IMITATION ANTIQUE SILYEB. 

and probably lost when deoanting the supematant liquor from the 
precipitate. When the precipitation is nearly completei the last 
additions of cyanide solution should be made very cautiously, and 
only so longp, as a turbidity, or miUdness, is produced in the clear 
liquor above the precipitate. Instances have been known in which 
not only silver, but gold precipitates also, have been partially re- 
dissolved by excess of cyanide and the solutions thrown away by 
ignorant operators as waste liquors. If by accident an excess of 
cyanide has been used during the precipitation of gold or silver 
solutions, the difficulty may be overcome by gradually adding a solu- 
tion of the metallic salt until, in its turn, it ceases to produce turbidity 
in the clear supematant liquor. Again, in dissolving precipitates of 
silver or gold, care is necessary to avoid using a larg^ excess of 
cyanide ; a moderate exoees only is necessary. 

6. Articles Falling into the Bath. — ^When an article falls into the bath, 
from the breaking of the slinging wire or otherwise, its recovery 
generally causes the sediment which accumulates at the bottom of the 
vat to become disturbed, and this, settling upon the work, produces 
roughness which is very troublesome to remove. If not immediately 
required, it is better to let the fallen article remain until the rest of 
the work is plated ; or if its recovery is of immediate importance, the 
rod containing the suspended articles should be raised every now and 
then during about half an hour, in order to wash aw%y any sediment 
that may have settied on the work. By gently lifting the rod up and 
down, or raising each piece separately, the light particles of sediment 
may readily be cleared from the surface of the work. When very 
large articles, as salvers, for example, are immersed in the bath, they 
should be lowered very gentiy, so as not to disturb the sediment 
referred to ; if this precaution be not rigidly followed, especially if 
the vat be not a very deep one, the lower portion will assuredly 
become rough in the plating, which the most skilful burnishing will 
be incapable of removing. We have frequentiy known it to be neces- 
sary to strip and replate articles of this description from the cause 
referred to. It must also be borne in mind that when anodes become 
very much worn minute particles of silver fall to the bottom of the vessel, 
which, when disturbed in the manner indicated, rise upward, settle 
upon the work, and become attached, by what may be termed eleciro' 
soldcrinr/, to the work, causing the deposit to be rough, and when 
such am-face is afterwards smoothed by polishing, the part exhibits 
numerous depressions, or is " pitted," as the Sheffield burnishers 
term it. 

7 . dean 1 nff Suspending Ro<h . — It is a very common practice with care- 
less workmen to clean the suspending rods with emery cloth while 
they arc in their places across the sides or ends of the plating vat* 



BILVBBtNO N0TB8. 2$$ 

This is a pmctioe which ahonld be striotly diBaUowed, for it is evident 
that the particlen of bran, emery, and Tnetallic oxides which beoome 
dislodged by the rubbing prooess, must enter the solution, and being 
many of them exceedingly light, will remain suspended in the solution 
for a considerable time, and finally deposit upon the articles when 
placed in the vat, while some i>ortions of the dislodged matter will 
become dissolved in the bath. All suspending rods should be cleaned 
at some distance from the plating vat, and wiped with a clean dry 
rag after being rubbed with emery cloth before being replaced aoroBs 
the tank. 

8. Eleetro'sihering Pewter Solder, — Besides the methods recommended 
elsewhere, the following may be adopted : After thoroughly cleaning 
the article, apply to the soldered spot with a camel-hair brush a weak 
solution of cyanide of mercury ; or if it be a large surface the soldered 
part must be dipped for a short time in the mercury solution. In 
either case the article must be well rinsed before being immersed in 
the silver bath. 

9. Metal Tankt, — ^When working solutions in iron tanks, the plater 
should be very careful not to allow the anodes, or the work to be 
coated, to come in contact with the metallic vessel while deposition is 
taking place, since this will not only cause the current to be diverted 
from its proper course, but will also cause the anodes, especially if 
there be a large excess of free cyanide in the bath, to become eaten 
into holes, and fragments of the metal will be dislodged and fall to the 
bottom of the vat, and possibly small particles of the metal will settie 
upon the work. We remember an instance in which several wooden 
nickel-plating tanks, lined with stout sheet lead, coated with pitch, 
yielded very poor results from some cause unknown to the plater. 
Having becoi consulted on the matter, the author soon discovered the 
source of mischief : the copper hooks supporting the heavy anodes 
had become imbedded in the pitch, and were in direct communication 
with the lead lining, from which a greater portion of the pitch had 
scaled off, leaving the bare metal exposed below the surface of the 
solution. Upon applying a copper wire connected to the negative 
electrode of the large Wollaston battery, at that time used at the 
establishment, to the leaden flange of each tank the author obtained bril- 
liant sparks, to the g^reat astonishment of the plater and his assistants, 
and subsequenUy caused strips of wood to be placed between the side 
anodes and the lead lining, after which nickel-plating proceeded with- 
out check. 

10. Bright Plating. — ^Even in the most skilful hands the bright solu- 
tion is very liable to yield ununiform results. When the solution has 
remained for some time without being unxL it is apt to give patchy 
zwidts, the work being bright in some parts only ; if the solution is 



^86 IMITATION ANTIQITE SILVER. 

disturbed, by taking out work or by putting in fresh work, sometimeB 
the hitter will refuse to become bright, and the remainder of the work 
in the bath will gradually become dull. To obviate this the bath 
should be well stirred over night, and all the work to be plated at one 
time put into the bath as speedily as possible, and all chances of 
disturbance avoided. When the work is known to have a sufficient 
coating of the bright deposit, the battery connection should bo broken 
and the articles then at once removed from the bath. On no account 
must an excess of the ** bright '' liquid be allowed to enter a bath. 

1 1 . Dirtr/ Anodes. — When the anodes, which should have a greyish 
appearance while deposition is taking place, have a pale greenish film 
upon their surface, this indicates that there is too little free cyanide in 
the bath, or that the currant is feeble ; the battery should first be 
attended to, and if found in good working order, and all the connec- 
tions perfect, an addition of cyanide should be made ; this, however, 
should only be done the last thing in tho evening, the bath then well 
stirred and left to rest untQ the following morning. 

.12. Dtut on the Surface of the Bath. — Sometimes in very windy weather 
the surface of the bath, after lying at rest all night, will be covered 
with a film of dust ; to remove this spread sheets of tissue paper, one 
at a time, over the surface of the liquid, then take the sheets up one by 
one and place them in an earthen vessel; the small amount of solution 
which they have absorbed may be squeezed from the sheets, passed 
through a filter, and returned to the bath, and the pellets of paper 
may then be thrown amongst waste, to be afterwards treated for the 
recovery of its metal. 

13. Old Slinging JFires. — It is not a good plan to use a slinging wire, 
one end of which has received a coating of silver or other metaJ more 
than once, without first stripping olf the deposited metal , in the first 
place the coated end of the wire becomes very brittle, and is liable to 
break when twisting it a second time, possibly causmg the article to 
fall into the bath, or on a floor bespattered with globules of mercury 
and other objectionable matter , again, the broken fragments of silver- 
covered wire, if allowed to fall carelessly on the floor, get swept up 
with the dirt, and the silver thus wasted. The wires which have been 
used once should be laid aside, with the plated ends together, and at a 
convenient time these ends should be dipped in hot stripping solution, 
until all the silver is dissolved off, and after rinsing, the ends should 
be made red hot, to anneal tliem ; the wires may then be cleaned with 
emery cloth and put in their proper place to l>e used again. Those 
minor details should always be attended to, since they do not neces- 
sarily involve much time and are assuredly advantageous from an 
economical view. It is too commonly the pmctice witli careless opera- 
tors to ncglact such simple details, but the consequence is that tlieir 



SILVEBIN6 NOTES. 287 

plating operationB are often rendered unnecessarily troubleeome, while 
their workshops are as unnecessarily untidy. 

14. Battery Connection*. — Before preparing work for the bath, the 
binding screws, clamps, or other battery connections should be ex- 
amined, and such orifices or parts as form direct metallic communication 
between the elements of the battery and the anodes and cathodes 
should be well cleaned if they have any appearance of being oxidised 
or in any way foul. The apertures of ordinary binding screws may bo 
cleaned with a small rat-tail file, and the fiat surfaces of clamps 
rubbed with emery cloth laid over a flat file. When binding screws, 
from long use or careless usage, become very foul, they should be 
dipped in dipping acid, rinsed, and dried quickly. Previous to put- 
ting work in the bath, a copper wire should be placed in contact with 
the suspending rod and the opposite end allowed to touch the anode, 
when the character of the spark will show if the current is sufficiently 
vigorous for the work it has to do : if the spark is feeble, the connec- 
tions should be looked to, and the binding screws tightened, if neces- 
eary ; the hooks and rods supporting tho anodes should also be 
examined, and if dirty, must be well cleaned, so as to insure perfect 
contact between the metal surfaces. 

15. Gutta-percha Lining for Flating Tank*, — This material should 
never be used for lining the insides of tanks which are to contain cyanide 
solutions, since the cyanide has a solvent action upon it, which, after a 
time, renders the solution a very bad conductor. The author once 
had to precipitate the silver from an old cyanide solution which had 
remained for a long period in a gutta-percha lined bath, and soon after 
the acid (sulphuric) had been applied to throw down the silver, there 
appeared, floating upon tho surface of tlie liquid, numerous clots of a 
brown colour, which proved to be gutta-percha, although greatly 
altered from its original stfale. 



CHAPTER XVIII. 
ELECTRO-DEPOSITION OF NICKEL. 

Application uf Nickel-plating. — The Depositing Tank.— Conducting Rods. — 
Preparation of the Nickel Solution.— Nickel Anodes. — Nickel-plating by 
Battery. — The T?nn-Carbon Batter}\ — Observations on Preparing Work 
for Nickel-plating. — The Potash Bath. — Dips or Steeps. — Dipping Acid. 
— PicUing BaUi. 

Applioattoa off Hidfl-plating. — ^Wlien applied to purposes for 
which it is specially adapted, nickel-plating may be considered one of 
the most important branches of the art of electro -deposition. In the 
earlier days of nickel-plating too much was promised and expected 
from its application, and, as a natural consequence, frequent disap- 
pointments resulted from its being applied to purposes for which it 
was in no way suited. For example, it was sometimes adopted as a 
substitute for silver-plating in the coating of mug^ or tankards used 
as drinking vessels for malt liquors, but it was soon discovered that 
those beverages produced stains or discolorations upon the polished 
nickel surface, which were not easily removed by ordinary means, 
owing to the extreme hardness of the metal as compared with silver or 
plated goods. Again, nickel-plated vegetable -dishes became stained 
by the liquor associated with boiled cabbage or spinach, rendering the 
articles unsightly, unless promptly washed after using— a precau- 
tionary measure but seldom adopted in the best-regulated sculleries. 
It was also found that polished nickel-plated articles when exposed 
to damp assumed a peculiar dulness, which after a time entirely 
destroyed their brilliant lustre, whereas in a warm and dry situation 
they would remain unchanged for years, a fact which the mullers of 
our restaurants and taverns which were nickel-plated many years ago 
bear ample testimony at the present day. 

While practical experience has taught us what to avoid in connec- 
tion with nickel-plating, it has also shown how vast is the field of 
usefulness to which the art is applicable, and that as a protective and 
ornamental coating for certain metallic surfaces, nickel has at present 
no rival. Its great hardness — which closely approximates that of 
steel — renders its surface, when polished, but little liable to injury 
from ordinary careless usage : while, being a non-oxidisable metal, 
it retains its natural whiteness, even in a vitiated atmosphere. 



THE DEPOSITINO VAT. 289 

The metals ordinarily coated with nickel bj deotro-depoflitjon are 
copper, bTBBx, steel, and iron, and since these require different jtri- 
paralory treatment, as also different periods of immersion in the nickel 
batk, thej will be treated separately. The softer metala, a» lead, tin, 
and Britannia nietal, are not suited for nickel -plating', and should 
never be allowed to enter the nickel bath. 

Vila ItapoBltlns Vat, or tbdIe. - The depositing' Teesel maj be made 
from slate or wood, but the following method of cODSbucting^ a Tat is 
that moBt generall; adopted, and when proparlj carried oat prodncei a 
vessel of great permanency. The tank ia made from zj-inch deal, 
planed on both aidcH, the boards forming the sides, ends, and tiottoia 
being grooved and tflng^ed, so 
as to make the jointa, when pat 
together, water-tight ; they are 
held together bj long bolts, 
tapped at one end to receive a 
not. The sides and ends, as 
also the bottom, are likewise 
seoared in their position by 

in Fig. 99. When the tank ia '''tf- 99- 

well screwed together, as in the 

engraving, the interior is to be well lined with pure thin sheet lead. It 
is of great importance that the lead used for this purpose be as pore u 
poshible, for if it contain zinc or tin it will be liable to be acted apon by 
the nickel solution which it is destined to hold, and pin-holes will be 
formed, through which the solution will eventually escape. The j'ointa 
of the leaden lining muBt not be united by means of solder, but by the 
mUi^eiKia pmceu, or " burning," as it is called. tliBt is, its seoms are 
fiited together by the hydrogen flame — an operation with which intel* 
ligent plumbers are well aojuaintod. If solder were osed for this 
poipose voltaic action would soon be set up between the lead and the 
tin of the solder by the action of the nickel solution, and in time a 
msAee of holes would be formed, followed by leakage of the vat. When 
the lead lining is complete the vessel most be lined throughout with 
matched boarding, kept in its position by a rim of wood fastened 
nmnd the upper edge of the tank. These tanks are usually 3 feet 
wide. 3 feet deep, and about 6 feet long, and hold about 150 

Before nmng the tank it should be well rinsed with clean water. It 
is a good plan to quite fill die tank with -water, and allow it to remain 
tbtrein for aeverul hoars, hj which time the pressure of the liquid wiU 
toon indicate if there be a leakage at any port ; it should then be 
emptied and examined, to ascertHin if thoroughly water-tight. 



ago 



ELECTRO-DEPOSITION OP NICKEL. 



We ynJl assume that it is desired to make up loo gallons of nickel 
solution — ^in which case the dexx>siting tank should be capable of 
holding not less than 120 gallons, to allow for the displacement of 
liquid by the anodes and articles to be immersed, as also to allow 
sufficient space — say 3 inches — above the solution to prevent the 
liquid from reaching the hooks by which the anodes are suspended, 
when the bath is full of work. Although we have taken 100 gallons 
■of solution as a standard^ we may state that, for large operations, 
tanks capable of holding 250 up to 500 gallons, or even more, are 
commonly employed. 

Oondvetiiic XodB. — These rods, which are used for supporting the 
nickel anodes, as also the articles to be nickeled, generally consist of 
I -inch brass tubing, with a core of iron rod ; they are commonly laid 
across the bath, leng^wise, extending about 3 inches beyond the 
extreme ends of the vessel. Sometimes, however, shorter rods are 
employed, and these are laid across the bath from side to side. For a 
nickel bath of 100 gallons and upwards three such suspending rods 
are used, one rod being laid from end to end, close to eadi side of the 
tank, upon which the requisite number of anodes are suspended by 
their hooks ; a third rod is laid, also longitudinally, along the centre 

of the tank, midway between 
the other two, for suspending 
the articles to be nickeled; 
the anode rods am to be con- 
nected together by a stout 
copper wire at one end by 
soldering. These rods are 
termed respectively the pMt- 
tive and negative conducting 
rods, the former receiving 
the anodes, and the latter 
the work to be nickeled. Fig. 
100 represents a cast nickel 
anode and its supporting hook 
of stout copper wire, which 
latter should not be less than 
\ inch in thickness. In order 
to insiire a perfect connection 
between the copper hook and the 
anode, the author has found it 
▼ery advantageous to unite the two by means of pewter sclder, in the 
following way,* and which it may be useful to quote here : The holes 





Fig. 100. 



* ** Electro-MeUUurgy Practically Treated.'' By Alexander Watt. 



FBKPARATION OE NICK2L SOLUTIONS. 29 1 

being cleaned with a rat-tail file, the hooks were clipped into ordinary- 
dipping' acid (sulphuric and nitric acid) for one instant, and rinsed. 
One end of each hook was then moistened with chloride of zinc, and 
immediately plunged into a ladle containing molten tin or pewter 
solder. The tinned hook was next inserted into the hole in the anode, 
and a gentie tap with a hammer fixed it in its place. The anode being 
laid flat on a bench, with a pad of greased rag beneath the hole, the 
ncKt thing to do was to pour the molten solder steadily into the 
hole, and afterwards to apply a heated soldering iron. It is better, 
however, before pouring in the solder, to heat the end of the anode, so 
as to prevent it from chilling the metal, and a littie chloride of zinc 
solution should be brushed over the inner surface of the aperture, so 
as to induce the solder to " run '* well over it, and thus insure a 
perfect connection between the hook and the anode. The importance 
of securing an absolutely perfect connection between these two 
surfaces will be reoog^sed when we state that we have known 
instances in which more than half the number of anodes, in a bath 
holding 250 gallons, were found to be quite free from direct contact 
with the supporting hooks, owing to the crystallisation of the nickel 
salt within the interior of the perforation having caused a perfect 
sei>aration of the hooks from their anodes. It was to remedy this 
defect that the author first adopted the system of soldering the con- 
nections. 

PMparatloii off tlM HlekA Boluttoa. — ^The substance usuaUy 
employed is the double sulphate of nickel and ammonia (or '* nickel 
salts," as they are commonly called), a ciystalline salt of a beautiful 
emerald green colour. This article should be ^r«. For 100 gallons 
of solution the proportions employed are : — 

Double sulphate of nickel and ammonia . . 75 lbs. 
Water 100 gallons. 

Place the nickel salts in a clean wooden tub or bucket, and pour upon 
them a qimntity of hot or boiling water; now stir briskly with a 
wooden stick for a few minutes, after which the green solution may 
be poured into the tank, and a fresh supply of hot water added to the 
undissolved crystals, with stirring, as before. This operation is to be 
continued until all the crystals are dissolved, and the solution trans- 
ferred to the tank. A sufficient quantity of cold water is now to be 
added to make up 100 g^ons in all. Sometimes particles of wood or 
other floating impurities occur in the nickel salts of commerce ; it is 
better, therefore, to pass the hot solution through a strainer before it 
enters the tank. This may readUy be done by tying four strips of 
wood together in the form of a frame, about a foot square, over which 
a piece of unbleached calico must be stretched, and secured either by 



29^ ELECTRO-DEPOSITION OF NICKEL. 

means of tacks or by aimplj tying it to each comer of the frame with 
string. 

Ifiekel Anodes. — It is not only necessary that the nickel salts 
should be perfectly pure — which can only be relied upon by purchas- 
ing them at some well-known, respectable establishment — but it is 
equally important that the nickel plates to be used as anodes — ^which 
may be either of cast or rolled nickel — should be of the best quality. 
A few years ago there was no choice in this matter, for rolled nickel 
was not then obtainable. Now, however, this form of nickel can be 
procured of almost any dimensions, of excellent quality, and any 
degree of thinness, whereby a great saving may be effected in the first 
cost of a nickel-plating outfit. Again, some years ago it was im- 
possible to obtaia cast nickel anodes of moderate thickness, conse- 
quently the outlay for this item alone was considerable. Such anodes 
can now be prooiured, however, and thus the cost of a nickel-plating 
plant is greatly reduced, even if cast anodes are adopted instead of 
rolled nickel. 

Ifickrt-platlng liy Battary. — ^For working a loo-gallon bath, four 
ceUs of a 3-gaUon Bunsen battery will be required, but only two of 
these should be connected to the conducting rods until the bath is about 
half full of work, when the other cells may be connected, which should 
be done by uniting them for intensity; that is, the wire attached to the 
carbon of one cell must be connected to the zinc of the next cell, and 
80 on, the two terminal wires being connected to the positive and 
negative conducting rods. If preferred, however, the batteries may 
be united in series, as above, before filling the bath with work, in 
which case, to prevent the articles first placed in the solution from 
''burning," as it is termed — owing to the excess of electric power — ^it 
will be advisable to suspend one of the anodes temporarily upon the 
end of the negative rod farthest from the battery, until the bath is 
about half filled with work, when the anode may be removed, and the 
remainder of the articles suspended in the solution. In working 
larger arrangements with powwful currents — to which we shall here- 
after refer — ^resistance coils are employed, which keep back the force 
of the electric current while the bath is being supplied with work, 
and even when such coils are used it is usual to suspend an anode or 
some other " stop,'* as it is called, from the negative rod during the 
time the work is being put into the solution. 

TwlB-Oai^bon BatUvy.^ — ^A very useful modification of the Bunsen 
battery, and well suited for nickel-plating upon a small scale, is the 
American twin-carbon battery, introduced by CSondit, Hanson and 
Van Winkle, of New Jersey, U.S.A., which, in its dissected condition, 
in represented in Fig. tor. A pair of carbon plates are united by a 
damp, with binding screw attached, as shown at ▲. A plate of stout 



IWIH-OUBUN BiTTKHV. 393 

sheet line, U cot ont so as to le&ve a projecting piaoe, to whiob 
a binding screw is also conneeted, as at D, tnA the ana is tnnud ap 
into an oval loTin to admit the poron* Cell, D. The lino bemg pat 
into the outer cell, a (which is made of stoneware), the poro'u cell ii 



i 



Fig.. 



plao«d within the zino cylinder, and the twin carbona thai deposited 
in the porous cell. The exciting fluids are, for the zinc, which must 
of ooiiTse be well amalgamated, I port oil of vitriol to 1 1 parta water. 
The porona cell ia filled to the aame height with a mixture oompoaed 
of equal measures of oil of vitriol and water, to which 1 ounces of 
nitric acid arc added. This is an exceedingly useful and compact 
batter;, and ia apecially serriceable in nickel-plating upon a moderate 
scale. When great electro-motive force ia required, strong nitric acid 
is used instcttd of the above mixture in the porous Cell. 

Obaomitlana on rraparlnc tha ITork Mr Mlekal-plattnc. — For 
several reasons, it is of greater importance that the articles to be 
coated with nickel should be what is termed ehemieally clean, than in 
any other branch of electro-depoeition. The eioess of cyanide used in 
gilding, silvering, and braadng solutions is capable of dissolving from 
the work such slight traces of organic matter as might be accidentally 
communicated by the hands, and being a powerful solvent of metallio 
oxides, the delicate fllm of oxide which quickly forms upon the surface 
of recently scoured work becomes at once dissolved in a cyanide solu- 
tion. In the case of a nickel solution, however, which ia prepared 
from a neutral salt, no such solvent action would take phuie, and the 
slightest trace of organic matter or of oxide resulting from Qie action 
of the air upon the prepared article, would prevent the adhedon of 
the nickel to the underlying metal, and the work would consequently 
iliip. In some estabUshroentfl, to prevent the possibility of direct 
contact of the hands with the work while being soonred, the men 
are required to hold the work with a clean piece of rag, which is 
frequently dipped in water during the operation of sooaring ; a good 
substitute for this ia to keep the hand holding the work, while 



294 



ELECTBO-DEPOSITION Oif NICKEL. 



brushing it with powdered pumioe or other material, well oiiarflred 
with the substance by dipping the fingers oooasionally in the powder. 
Before explaining the operation of scouring, it wiU be necessary to 
describe the yariouB solutions, or ''dips," as they are termed, in 
which the articles are immersed before and after being scoured. The 
first and most important of these is the potash bath, in which aU 
articles to be nickel-plated are immersed before undergoing any other 
treatment. 

The Fotaali Bath. — ^The vessel in which the solution of potash is 
kept for use generally consists of a galvanised wrought-iron tank 
capable of holding from 20 to 150 gallons, according to the require- 
ments of the establishment. An iron pipe, or worm, is placed at the 
bottom of the tank, one end of which communicates with a steam 
boiler, a stopcock being connected at a convenient distance for turn- 
ing the steam on or off ; or the tank may be heated by gas jets, by 




Fig. 102. 



means of perforated piping fixed beneath it. An ordinary form of 
potash tank is shown at a in Fig. 102, in which the worm-pipe is 
indicated by the dotted Unes, &c., a 0, the vertical pipe 6, with its 
stopcock Cy being conveniently placed at one comer of the tank, as 
shown in the engraving. The waste steam from the worm-pipe 
escapes into a second tank b, partly filled with water, which thus 
becomes heated, and is used for rinsing. A rod of iron, or brass tube 
with an iron core, rests upon the bath, longitudinally, for suspending 
the articles in the caustic liquor. 

The potash solution is made by dissolving half a pound of American 
potash in each gallon of water required to make up the bath, and the 
solution is always used hot. The object of immersing the work to be 
nickeled in the potash bath, is to render soluble any greasy matter 
which may be present, as, for example, the oil used in the various 
processes of polishing. In a freshly made solutiun (which must 



DIPS, OR STEEPS. 295 

always be kept hot), the work will only require to be immerfled for a 
few minutes, by which time the g^reasy matter will have become con- 
yerted into soap, and being thus rendered soluble, may easily be 
removed by the subsequent operations of brushing with pumice, &c.; 
but we must bear in mind that the eauatieity of the solution (and 
consequently its active property) gradually becomes diminidied, not 
only in consequence of the potash having combined with the gpreasy 
matter, but also owing to its constantly absorbing carbonic add from 
the air. When the bath has been some time in use, therefore, it will 
be necessary to add a fresh quantity of potash, say about a quarter 
of a pound to each gallon. It is easy to ascertain if the potash has 
lost its caustic property by dipping the tip of the finger in the solu- 
tion, and applying it to the tongue. As the bath becomes weakened 
by use, the articles will require a long^ immersion, and, with few 
exceptions, a protracted stay in the bath will produce no injurious 
effect. Articles made from Britannia metal, or which have pewter 
solder joints, should never be suffered to remain in the potash bath 
longer than a few minutes, since this alkali (caustic potash) has the 
power of dissolving tin, which is the chief ingredient of both. Again, 
articles made from brass or copper should never be suspended from the 
same rod as steel and iron articles, in case the potash solution should 
have become impregnated with tin dissolved from solder, &o. ; for if 
this precaution be not observed it is quite likely (as we have frequently 
seen in . an old bath) that the steel articles will become coated with 
tin, owing to voltaic action set up in the two opposite metals by the 
potash solution. Cast-iron work, in which oil has been used in the 
finishing, should, owing to its porous character, be immersed in the 
potash bath for a longer period than other metals in order to thoroughly 
cleanse it from greasy matter. 

Dips, or BtenNi. — ^Besides the potash solution, certain other liquids 
are employed in nickel-plating after the work has been '* potashed " 
and scoured, which may be properly described in this place ; and we 
may here remind the reader that the employment of these dipty as 
they are called, is based upon the fact that the neutral solution of 
nickel has no power (unlike cyanide solutions) of dissolving even slight 
films of oxide from work which, after being scoured, has been exposed 
to the air and become slightly oxidised on the surface. In order, 
therefore, to remove the faintest trace of oxidation from the surface 
of the work — ^the presence of which would prevent the nickel from 
adhering — ^it is usual to plunge it for a moment in one or other of the 
following ouxtures after it has been scoured, then to rinse it, and 
immediately suspend it in the nickel bath. 

The Cyofiide Dip. — This solution is formed by dissolving about half 
a pound commercial cyanide of potassium in each gallon of water ; for 



396 ELECTRO-DB POSITION OV NICKEL. 

operatioaa on a moderate scaile, a Htuaovaire Fessel capable of holding 
about fifteen gallons may be supplied witb about twelve galloiu of tlu 
aolation. Baths of the form shown in x, fig'. 103, and which ai« to 
be obteined at the Lambeth potteries, are well suited to this purpoae. 
A:Qothar form of stoneware vessel is seen in Fig. 104, wbioh, being 




Tib- 103- ^W- ' 



deepw, is useful for calaiu classes of work. In applying the eyontib 
dip to artdclea of great length, it ia commonly the praotioe to employ a 
oommoD earthenware jug, kept near the dipping batii ; this, bdng 
filled with the cyanide solution, ia hold above the highest point of Qu) 
HTticle (a brass tube, for inatonce) and tilted so that ita oonteota may 
flow downward aud pass all over the tube, which ia then qoiokly 
taken to the water trough or traj and well rinsed, when it is at 
oooe placed in the nickel bath. On using the oy anide dip, it mn«t be 
ranembered that ite only object ia te dissolve from the surfttoe of the 
recently scoured work an alaioil imaginari/ _film of oxide , therefore the 
mere contact of the cyanide solution ia amply sufflcient to aooomplish 
the object ; on no account should brass or copper artiolea be eipoaed 
to tbe action of the dip for more than a /etc itcmdi ; indeed, if the 
solution is in an active condition, the quicker the opention is con- 
ducted the better. It will readily be nnderstood, however, that the 
weak cyanide bath will gradually lose its actdvily, when the dipping 
may be effected somewhat more leisurely. It is a oommoa fault, 
however, to use theae dips long after they have jrielded up their active 
power, and we have frequently known them to be anployed, and 
relied upon, when they were utterly useless. 

The Acid Dip. — This solutioD, which is used for dipping steel and 
iron articles aHer they have been scoured, is composed of hydrochlorio 
(muriatio) acid and water, in the proportion of half a pound of the 
acid to each gallon of water. The solution is generally contained in • 
ahaUow wooden tub, which may conveniently bo the half of a brandy 
cask or rum puncheon ; but since the acid eventually finds its way 
to the iron hoops by which such vessels are held together, it is a good 



DIPPING ACID. 397 

plan, in the first instanoe, to have a couple of wooden hoops, secured 
by copper rivets, placed over the vessel so as to prevent it from leak- 
ing in the event of the iron hoops giving way in consequence of the 
corrosive action of the acid liquor. PKoautions of this nature will 
prevent leakage and the inconvenience which it involves. 

IMppliiS Add. — This name is given to a mixture which is frequently 
used for imparting a bright surface to brass work, and which is 
variously composed according to the object to be attained. When 
required for dipping brass work preparatory to nickel-plating, it is 
oommonly composed of — 

Sulphuric acid 4 lbs. 

Nitric acid 2 „ 

Water 4 pints. 

In making up the above mixture, the nitric acid is first added to the 
water, and the sulphuric acid (ordinary oil of vitriol) is then to be 
g^radually poured in, and the mixture stirred with a glass rod. When 
cold, it is ready for use. The mixture should be made, and kept, in a 
tUmeware vessel, which should be covered by a sheet of stout glass 
each time after using, to prevent its fumes from causing annoyance 
and from injuring brass work within its vicinity. The '' dipping" 
should always be conducted either in an outer yard, or near a fire- 
place, so that the fumes evolved during the operation may escape, 
since they are exceedingly irritating when inhaled by the lungs. 
When it is convenient to do so, it is a good plan to have a hood of 
wrought iron, painted or varnished on both sides, fixed above an 
ordinary fireplace in the workshop, and to have a hole made in the 
brickwork above the mantelpiece to conduct the fumes into the chim- 
ney ; this arrangement, however, will be of little use, unless there is 
a good draught in the chimney. It is well to ascertain this, there- 
fore, before the dipping is proceeded with, which may be readily done 
by holding a large piece of ignited paper above the grate, when, if 
the flame persistently inclines towards the chimney, the draught may 
be considered perfect ; if, however, it shows any inclination to come 
forward^ it may be assumed that the draught is imperfect, owing to 
the chimney being filled with cold air. In this case lighted paper 
should be applied as before, until the flame and smoke of the ignited 
material have a direct tendency upward, or in the direction of the 
chimney. We are induced to give these precautionary hints more 
especially for the g^dance of those who may be necessitated to work 
in apartments of limited space. In all cases, a vessel of clean water 
should be placed close to the dipping bath, into which the articles are 
plunged thf instant after they have been removed from the dipping 
acid. 



298 ELECTRO-DEPOSITION OF NICKEL. 

noklinc Bath. — Cast iron, before being nickeled, requiree to be 
placed in a cold acid solution, or pickle, as it ia called, to dissolve or 
loosen the oxide from its surface. The pickle may be prepared in a 
wooden tub or tank, from either of the following formulie : — 

Sulphuric acid (oil of vitriol) . . . ) lb. 
Water i gallon. 

• 

Cast-iron work immersed in this bath for twenty- minutes to half 
an hour will generally have its coating of oxide sufficiently loosened 
to be easily removed by means of a stiff brush, sand, and water. 

When it is desired that the articles should come out of the bath 
bright, instead of the duU black colour which they present when 
pickled in the plain sulphuric acid bath, the following formula may 
be adopted : — 

Sulphuric acid i lb. 

Water i gallon. 

Dissolve in the above two ounces of zinc, which may be convenientiy 
applied in its granuUited form. When dissolved, add half a pound of 
nitric acid, and mix well. 



CHAPTER XIX. 

ELECTRO-DEPOSITION OF NICKEL (eontimted). 

Preparation of Nickeling Solutions. — Adams' Process. — Unwinds Process 
— Weston's Process. — Powell's Process. — Potts* Process. — Doable Cyanide 
of Nickel and Potassium Solution. — Solution for Nickeling Tin, 
Britannia Metal, Ac. — Simple Method of preparing Nickel Salts. — 
Desmur's Solution for Nickeling Small Articles. 

VMparatlon of llickiiling Bolntloiu. — ^Although many solutions 
have been proposed, we may say, with confidence, that for all prao- 
tioal purposes in the electro-deposition of nickel, a solution of the 
double sulphate of nickel and ammonium, with or without the addition 
of common salt, will be found the most easy to work and the most uni- 
form in its results, while it is exceedingly permanent in character if 
worked with proper care and kept free from the introduction of foreign 
matter. The prex>aration of a nickel bath from the pure double salt is 
exceedingly simple, as we have shown, and only needs ordinary care to 
keep such a solution in good working orderfor a very considerable period. 
In order that tiie reader may, however, become conversant with tiie 
various solutions and modifications which ingenious persons have from 
time to time introduced, we will, as briefly as possible, explain such 
of tiiese processes as may appear to deserve attention, if not adoption. 
Boettger's original process having been already referred to, we will 
now describe Mr. Adams' modification of it, for which he obtained 
patents in this country, in France, and tiie United States, and which, 
after much costiy litigation, and consequent loss to those who had 
become possessed of tiiem, were proved to be unnecessary to the success- 
ful deposition of nickel by electrolysis. When the ordinary simple 
methods of preparing the double salts of nickel and ammonium are taken 
into consideration, it seems marvellous that Adams' exceedingly round- 
about process — ^which no one witii practical chemical knowledge would 
dream of following — should have been considered worth contesting ; 
not to defend the process as such, which no one infringed, but to 
secure tiie sole right to deposit nickel by electro-chemical means, by 
any process whatever. And what was the real " bone of contention " ? 
It was based upon the most absurd '' claim " ever allowed to become 
attached to a patent, which runs as follows :— 



300 ELECTRO- DEPOSITION OF NICKEL. 

"The electro-deposition of nickel by means of a solution of the 
doable sulphate of nickel and ammonia, or a solution of the double 
chloride of nickel and ammonium, prepared as [below] described, and 
used for the purposes [below] set forth, in such a manner as to be free 
from the presence of potash, soda, alumina, lime, or nitric acid, or 
from any acid or alkaline reaction.*' 

According to this, if any solution of nickel, no matter how pre- 
pared, which could be proved by analysis to be free from the sub- 
stances named (not one of which would be a necessary associate of 
nickel or of its double salts), such solution, if used in nickel-plating, 
would be an infringement of the patent! This tee know was the 
impresBion of those who held the English patent, and we vainly 
endeavoured to show its fallacy. '* Any solution of nickel which is 
free from these substances and used for plating purposes is an infringe- 
ment of our patent.'* That was the contention, and the owners of 
this patent believed themselves entitled to an absolute monopoly of the 
right to nickel-plate within the four quarters of the United Kingdom. 

Adams' Pirocaas. — In preparing the solution, the inventor prefers 
to use pure nickel, but commeroial nickel may be used. *'Commeroial 
nickel," says the patentee, ** almost always contains moro or less of 
the reagents employed in the purification of this metal, such as sul- 
phate of lime, sulphide of calcium, sulphide of sodium or potassium, 
chloride of sodium, and alumina. When any of these substances are 
present, it is necessary to remove them. This can be done by melting 
the nickel, or by boiling it in water containing at least i per cent, of 
hydrochloric acid. The boiling must be repeated with fresh acid and 
water until the wash -waters give no indication of the presence of lime 
when treated with oxalate of ammonia. When the metal is purified 
by melting, the foreign substances coUect on the top of the metal in 
the form of slag, which can be removed mechanically. If the nickel 
contains zinc, it should be melted in order to volatilise the zinc and 
drive it ofiP. The crucible in such a case must not be closed so tightly 
as to prevent the escape of the zinc fumes. If copper, arsenic, or 
antimony be present in the nickel, they can be removed, after the 
nickel is dissolved, by passing sulphuretted hydrogen through the 
solution. The acid to be used in dissolving the metal consists of 
I part strong nitric acid, 6 parts muriatic acid, and T part water. 
Nitric acid or muriatic acid may be used separately, but the above is 
preferred. A quantity of this acid is taken sufficient to dissolve any 
given amount of the metal, with as little excess of the former as pos- 
sible ; a gentle heat is all that is required. The resulting solution is 
filtered ; and to prepare the solution of the double sulphate of nickel 
and ammonium, a quantity of strong sulphuric acid, sufficient to con- 
vert all the metal into sulphate, is added, and the solution is then 



ADAMS PROCESS. 



301 



evaporated to dryness. The mass is then again dissolved in water, 
and a much smaller quantity- than before of sulphuric acid is added, 
and the whole again evaporated to dryness, the temperature being 
raised finally to a jMsint not to exceed 650** Fahr. This temperature is 
to be sustained until no more vapours of sulphuric acid can be 
detected. The resulting sulphate of nickel is pidverised, and thoroughly 
mixed with about one-fiftieth of its weight of carbonate of ammonia, 
and the mass again subjected to a gradually increasing tempera- 
ture, not to exceed 650® Fahr., until the carbonate of ammonia 
is entirely evaporated. If any iron is present, the most of it will be 
converted into an insoluble salt, which may be removed by filtration. 
The resulting dry and neutral sulphate of nickel is then dissolved in 
water by boiling, and if any insoluble residue remains, the solution is 
filtered. From the weight of nickel used before solution, the amount 
of sulphuric acid in the dry sulphate can be calculated. This amount 
of sulphuric acid is weighed out and diluted with four times its weight 
of water, and saturated with -pxae ammonia or carbonate of ammonia 
— ^the former is preferred. This solution, if it is at all alkaline, should 
be evaporated until it becomes neutral to test-paper. The sulphate 
of ammonia of commerce may Hkewise be used, but pure sulphate of 
ammonia is to be preferred. The two solutions of the sulphate of 
nickel and sulphate of ammonia are then united, and diluted with 
sufficient water to leave i^ to 2 ounces of nickel to each gallon of solu- 
tion, and the solution is ready for use. The object of twice evaporat- 
ing to dryness and raising the temperature to so high a degree is, in 
the first place, to drive oS the excess of sulphuric acid ; and secondly, 
to convert the sulphate of iron, if it exists, into basic sulphate, which 
is quite insoluble in water. 

*' In order to give the best results, it is necessary that the solution 
should be as nearly neutral as possible, and it should in no case be 
acid. The inventor prefers to use the solution of a specific gravity of 
about i'052 (water i-ooo), though a much weaker or still stronger 
solution may be used. At temperatures above the ordinary the solu- 
tion still gives g^ood results, but ia liable to be slowly decomposed. 
An excess of sulphate of ammonia may be used to dilute the solution, 
in cases where it is desirable to have it contain much lees than t ounce 
of nickel to the gfallon. 

** In preparing the solution of double chloride of nickel and ammo- 
nium, the nickel is to be purified and dissolved in the same manner as 
is described for the previous solution ; and it is to be freed from copper 
and other foreign matters in the same manner. The solution is then 
evaporated to dryness ; it should be rendered as anhydrous as possible. 
The salt is then placed in a retort, and heated to a bright red heat. 
The salt sublimes, and is collected in a suitable receiver, the earthy 



302 ELECTRO-DEPOSITION OF NICKEL. 

matter being left behind. The salt, thus purified, is diigaolved in 
water, and to the solution ia added an equivalent quantity of pure 
chloride of ammonium. The solution is then ready for use ; it may 
have a specific g^vity of 1*050 to i-ioo.*** 

The repeated evajMsrationB recommended by Adams are wholly 
unnecessary in the preparation of the double sulphate of nickel and 
ammonium or the double chloride, for if the nickel be pure (and there 
is no difficulty in obtaining it in this condition), the ordinary method 
of dissolving the metal or its oxide, and subsequent addition of the 
ammonia salt and careful crystallising the double salt, would give the 
same result, with far greater economy, both of time and iiouble. 

m&win'a Process. — This ingenious process, for which Mr. XJnwin 
obtained a patent in 1877, and in which crystallisation of the salts 
18 rendered unnecessary, is conducted as follows :— He first prepares 
the sulphate of nickel *^by taking three parts of strong nitric acid 
(sp. gr. about 1*400), one part of strong sulphuric acid (sp. gr. 
about 1*840), and four parts of water, all by measure, mixing them 
cautiously, and about half filling an open earthenware pan with the 
mixture. To every gallon of this mixed acid, I then add about two 
pounds of ordinary grain or cube nickel, and I heat the liquid by a 
sand-bath or other suitable means. If during the process of solution 
the action becomes inconveniently violent, I moderate it by the addi- 
tion of a little cold water. If the nickel entirely dissolves (except a 
small quantity of black matter), I add more of it, in small portions at 
a tune, and continue the addition at intervals until it is in excess. 
When the production of red fumes has nearly, or entirely, ceased, or 
when the liquid becomes thick and pasty, from the separation of solid 
sulphate of nickel, I add a moderate quantity of hot water, and boil 
and filter the solution ; the deep green liquid so obtained is a strong 
solution of sulphate of nickel. If, from the circumstance of its pro- 
duction, I consider that it requires purification, I concentrate the 
solution by evaporation, until on cooling it yields a considerable 
percentage of crystals of sulphate of nickel ; these crystals I collect, 
wash with a little cold water, and redissolve in a moderate quantity 
of hot water, filtering again if necessary. When cold, the liquid is 
ready for further treatment. 

'* I next prepare a strong solution of sulphate of ammonia, by dis- 
solving the salt in hot water, in the proportion of about four pounds 
of the salt to each gallon of water, and then filter the liquid if neces- 
sary, and allow it to become cold. I then obtain the pure double 
sulphate of nickel and ammonia by adding the above solution of 
sulphate of ammonia to that of the sulphate of nickel ; but I do not 

* For further remarks upon Adam's process, see pp. 460, 461. 



UNWIN 8 PROCESS. 303 

stop the addition of the solution of sulphate of ammonia, when suffi- 
cient has been added to combine with all the sulphate of nickel 
present, but I continue to add a large excess. I do this because I 
have discovered that the double sulphate of nickel and ammonia is far 
less soluble in the solution of sulphate of ammonia than in pure 
water, so that it is precipitated from its solution in water on adding 
sulphate of ammonia. I therefore continue adding the solution of 
sulphate of ammonia, continually stirring, until the liquid loses 
nearly all its colour, by which time the double sulphate of nickel and 
ammonia will have been precipitated as a light blue crystalline 
powder, which readily settles to the bottom of the vessel. I then 
pour off the liquid from the crystalline precipitate of double sulphate 
of nickel and ammonia, and wash the latter quickly with a strong, 
cold solution of sulphate of ammonia, as often as I consider necessary 
for its sufficient purification ; but I do not throw away this liquid 
after use, but employ it at my discretion for combining with fresh 
sulphate of nickel, instead of dissolving a further amount of sulphate 
of ammonia. If I desire to make a further purification of the double 
sulphate of nickel and ammonia, I make a strong solution of it in 
distilled water, and add to the liquid a strong solution of sulphate of 
ammonia, by which means the double sulphate is precipitated in a 
very pure condition, and is separated from the Uquid by filtration, or 
by other convenient means, and then dried, or used direct as may be 
desired ; the liquid strained away can be employed, instead of fresh 
solution of sulphate of ammonia, for combining with more sulphate 
of nickel, or for washing the precipitate of the double sulphate." 

Weston's Froesss. — Mr. Edward Weston, of Newark, N.J., 
having observed that boric acid, when added to nickel solutions, pro- 
duced favourable results in the electro-deposition of nickel, obtained 
a patent for '* the electro-deposition of nickel by means of a solution 
of the salts of nickel containing boric acid, either in its free or com- 
bined state. The nickel salts may be either single or double." The 
advantages claimed for the boric acid are that it prevents the deposit 
of sub-salts upon the articles in the bath, which may occur when the 
bath is not in good condition. Mr. Weston further claims that the 
addition of this acid, either in its free or combined state, to a solution 
of nickel salts renders it less liable to evolve hydrogen when the solu- 
tion is used for electro -deposition ; that it increases the rapidity of 
deposition by admitting the employment of a more intense current, 
while it also improves the character of the deposit, which is less 
brittle and more adherent. Mr. Wahl, after extended practical trials 
of Mr. Weston^s formula, states that they have ** convinced him of the 
substantial correctness of the claims of the inventor," and he adds, 
"Where the double sulphate of nickel and ammonia is used, the addi- 



304 ELECTRO-DEPOSITION OF NICKEL. 

tion of boric acid, in the proportion of from i onnce to 3 onnoee to the 
g^on of solution, gives a bath less difficult to maintain in grood 
working' order, and affords a strongly adhesiye deposit of nickel. The 
deposited metal is dense and white, approaching in brilliancy that 
obtained from the solution of the double cyanide." The formula for 
preparing the solution ii 



Double sulphate of nickel and ammonia . . . zo parts. 

Boric acid, refined 2} to 5 „ 

Water 150 to 200 „ 



Tow^Hl'M Piuoeai. — ^This inveiitor claims to have discovered that 
benzoic acid, added to any of the nickel salts, arrests, in a marked 
deg^ree, the tendency to an imperfect deposit, prevents the decompo- 
sition of the solution, and consequent formation of sub-salts. The 
proportion of benzoic acid to be added to the bath is said to be one- 
eighth of an ounce to the gallon of solution. This bath has been 
favourably spoken of. Powell also gives the following formulse for 
nickel baths : — 

1. Sulphate of nickel and ammonia . . . zo parts. 

Sulphate of ammoniu^ 4 »y 

Citric acid z „ 

Water . ' 200 „ 

The solution is prepared with the aid of heat, and when cool, a 
mnall quantity of carboziate of ammonia is added until the solution is 
neutral to test paper. 

2. Sulphate of nickel 6 parts. 

Citrate of nickel 3 »» 

Phosphate of nickel 3 n 

Benzoic acid 1} n 

Water 200 „ 

3. Phosphate of nickel zo parts. 

Citrate of nickel 6 „ 

Pyrophosphate of sodium zo) „ 

Bisulphite of sodium x) n 

Citric acid 3 »f 

Liquid ammonia 1 5 » 

Water 400 „ 

These solutions are said to give good results, but the very compli- 
cated ziature of the latter almost takes one's breath away. 

Pons' rirooeas.— In 1880, Mr. J. H. Potts, of Philadelphia, 
patented an improved solution for the electro-deposition of nickel, 
which oonsists in employing acetate of nickel and acetate of lirne^ 



POTTS PROCESS. 305 

with '* the addition of sufficient free acetic acid to render the Bolntion 
distinctly acid." The formula is given below : — 

Acetate of nickel 2} parts. 

Acetate of calcium 2| » 

Water 100 „ 

To each gallon of the above solution is added i fluid ounce of aoetio 
acid of the sp. gr. i'047. Mr. Potts first precipitates the carbonate 
of nickel from a boiling aqueous solution of the sulphate, by the 
addition of bicarbonate of soda, then filters and dissolves the well- 
washed precipitate in acetic acid, with the aid of heat. 

*^ To prepare this bath, dissolve about the same quantity of the dry 
carbonate of nickel as that called for in the formula (or three-quarters 
of that quantity of the hydrated oxide) in acetic acid, adding the acid 
cautiously, and heating until effervescence has ceased and solution is 
complete. The acetate of calcium may be made by dissolving the 
same weight of carbonate of calcium (marble dust) as that called for 
in the formula (or one-half of the quantity of caustic lime), and treat- 
ing it in the same manner. Add the two solutions together, dilute 
the volume to the required amount by the addition of water, and then 
to each gallon of the solution add a fluid ounce of free acetic acid as 
prescribed." 

In reference to the above solution, Wahl says that he has worked 
it under a variety of circumstances, and has found it, in many 
respects, an excellent one. " It gives satisfactory results," he states, 
'* without that care and nicety in respect to the condition of the 
solution and the regulation of the current which are necessary with 
the double sulphate solution. The metallic strength of the solution is 
fully maintained, without requiring the addition of fresh salt, the 
only point to be observed being the necessity of adding from time to 
time (say once a week) a sufficient quantity of acetic acid to maintain 
a distinctly acid reaction. It is rather more sensitive to the presence 
of a large quantity of free acid than to the opposite condition ; as in 
the former condition it is apt to produce a black deposit, while it may 
be run down nearly to neutrality without notably affecting the 
character of the work. The deposited metal is characteristically 
bright on bright surfaces, and requiring but little buffing to finish. 
It does not appear, however, to be so well adapted for obtaining 
deposits of extra thickness as the commonly used double sulphate of 
nickel and ammonium. On the other hand, its stability in use, the 
variety of conditions under which it will work satisfactorily, and the 
trifling care and attention it caUs for, make it a useful solution for 
nickeling." 

Boubto Oyanld* of molMl and PotaMtmn Soltitton. — ^This was 

X 



3o6 ELEGTBO-DEPOSITION OP NICKEL. 

one of the earliest solutions used for depositing nickel, and is capable 
of yielding an exceedingly white deposit. Though neither so eoono- 
mical nor so susceptible of yielding stout deposits of nickel as the 
ordinary double sulphate or double chloride, it may be advantageously 
employed when only a thin coating of a fine white colour is desired. 
It is stated to be somewhat extensively used in some large nickel- 
plating works in the United States. To prepare the solution, pfure 
nickel or oxide of nickel is dissolved in either of the mineral acids ; 
a mixture of hydrochloric and nitric acids, in the proportion of four 
parts of the former to one of the latter, may be used, an excess of the 
metal being taken to fully neutralise the acid. The solution is then 
evaporated and set aside to crystallise. The crystals, after being well 
drained and quickly rinsed in cold water, are next dissolved in water 
by the aid of heat, and when the solution has become cold a solution 
of C3ranide of potassium is carefully added, with stirring, until all the 
metal has been thrown down in the form of cyanide of nickel. Care 
must be taken not to add an excess of cyanide. The supernatant 
liquor is now to be poured off, and the precipitate washed repeatedly 
with water. A strong solution of cyanide is next added, with stirring, 
until all the cyanide of nickel is dissolved. A small excess of cyanide 
is then to be added, when a reddish-brown solution of double cyanide 
of nickel and potassium will result, which, after filtering, is ready for 
use. The solution should be as concentrated as possible, abnost to the 
point of saturation. 

flOtatfoift ilBr HlolMiHng Tin, Brttaimia Btotal, *o.— The follow- 
ing formula has been reoonmiended for coating tin, Britannia metal, 
lead, and zinc, as also brass and copper : — 

Sulphate of nickel and ammonium . xo parts. 

Sulphate of ammonium 2 „ 

Water 300 „ 

The salts are to be dissolved in boiling water, and when cold the 
solution is ready for use. For nickeling cast and wrought iron and 
steel the following bath is recommended : — 

Sulphate of nickel and ammonium .10 parts. 

Sulphate of ammonium i) „ 

Water 250 „ 

Wmpla Matliod ofPnpaxkng Hlekal Baits.— To make the double 
chloride of nickel and ammonia take, say, 2 ounces of pure cube nickel, 
or oxide of nickel, and dissolve in hydrochloric acid, to which a little 
nitric acid may be added, taking care not to have an excess ; apply 
gentle heat to assist the chemical action. When the evolution of gas 
has ceased dilute the resulting solution with cold water to make about 
I quart of liquor ; now add liquid ammonia gradually, stirring after 



DBSMUB S SOLUTION. 307 

each addition, until the solution is neutral to test-paper ; now disaolyo 
I ounce of chloride of ammonium (sal-ammoniac) in sufficient water, 
and add this to the former solution ; evaporate the mixture until 
crystals begin to form, then allow it to cool and crystallise gradually ; 
next pour off the clear liquor, and repeat the evaporation to obtain 
a second batch of crystals ; in the latter operation the solution may 
be evaporated to dryness. ^ Finally, mix all the resulting products 
together and dissolve in about three pints of hot water, filter, and 
make up to about one gallon by the addition of cold water. The 
solution should have a specific g^ravity of 1*050 to 1*075. 

The Double Sulphate of Nickel a$ul Ammonium may readily be formed 
by dissolving oxide or carbonate of nickel in dilute sulphuric acid 
(l part acid to 2 parts water). The resulting solution is then to be 
neutralised with ammonia and crystallised. To each pound of the 
dry crystals add i pound of pure sulphate of ammonia, dissolve the 
mixed salts, evaporate the solution, and re-crystallise. Cube or grain 
nickel may also be dissolved in a mixture composed of i part sulphuric 
acid and 2 parts water, with the addition of a small quantity of nitric 
acid, moderate heat being applied as before. The solution is then to 
be evaporated and set aside to crystallise, and to convert the sulphate 
of nickel into the double salt, sulphate of ammonia is to be added in the 
same proportion as before ; the mixed salts must be dissolved, filtered, 
and crystallised. In making up a bath from the double sulphate 
prepared by either of the above methods, about 12 ounces of tiie dry 
crystals are to be taken for each gallon of bath, and the crystals 
should be dissolved in sufficient hot water, the solution filtered, and 
the requisite quantity of cold water added to make up the full quantity 
of the solution in the proportions given. At the temperature of 60** Fahr. 
the bath should have a speoiflo g^Tity of about 1*052. It is neces- 
sary to state that the nickel employed should be pure^ which can only be 
relied upon by obtaining it from some well-known respectable house. 

P eai um' a Solution for HlelMUiiff Small Artloles.— The author 
is indebted to M. Desmur for the following formula for coating small 
articles, which we recommend to the attention of those whose trade 
chiefly lies in nickeling struck work, such as umbrella-mounts, and 
the like : — 

Double sulphate of nickel and ammonium . 7 kilogrammes 

Bicarbonate of soda 800 grammes. 

Water 100 litres. 

The bicarbonate of soda must be added when the nickel solution is 
warm, in small quantities at a time, otherwise the effervescence which 
occurs may cause the solution to overflow. The bath is to be worked 
up to nearly boiling point. If, after working for some time, the 
deposit becomes of a darkish colour, add a small lump (about the size 



3o8 ELECTBO-DEPOSITION OF NICKEL. 

of a nut) of sulphide of sodium, which will remedy it. '* Of all the 
solutions of nickel which I have tried,*' says M. Desmur, ** this has, 
without doubt, given me the best results, both as to quickness of 
working and whiteness of deposit, which is equal to that of silver. 
Nickel deposited from this solution can be burnished. If the nature 
of the articles to be nickeled will not allow them to be either polished 
or bumished, they may be rendered bright by first dipping them in 
nitric acid and afterwards passing them rapidly through a mixture of 
old nitric acid dip (already saturated with copper), sulphuric acid, 
greasy calcined soot, and common salt." 



CHAPTER XX. 

ELECTTRO-DEPOSITION OF NICKEL (eontinueO). 

Preparation of the Work for Nickel-plating.— The Scouring Tray.— Brass and 
Copper Work.— Nickeling small Steel Articles.— Nickeling small Brass 
and Copper Articles. — Nickeling by Dynamo-electricity. — Nickeling 
Mailers, Sausage Warmers, &c. — Nickeling Bar Fittings, Sanitary Work, 
^.—Nickeling Long Pieces of Work.— Dead Work —Nickeling Stove 
Front?, Ac. — Nickeling Bicycles, Ac. — Nickeling Second-hand Bicycles, 
Ac — Nickeling Sword-scabbards, Ac. — Nickeling Harness Furniture, 
BitB, Spurs, Ac. — Nickeling Cast-iron Work. — Nickeling Chain Work. — 
Re-Nickeling Old Work.— Nickeling Notes. 

Preparation of thm Work tor Hlekol-platliis. — Since the yarions 
metals ordinarily coated with nickel require different trentment, it 
will be more oonyenient to 
treat them under their re- 
spective heads, by which 
the intending nickel-plater 
will become more readily 
conversant with the mani- 
pulation requisite in each 
particular case. All the pig. 105. 

preliminary arrangements 

of nickel bath, batteries, dips, Ac, being complete, the work, as it 
is received from the polishing shop, should be placed in regular 
order upon a bench, the name of each customer being indicated by a 
ticket for each group of work, so as to prevent confusion. Small 
work is generally handed into the plating-room upon shallow trays, 
of the form indicated in Fig. 105. These trays are usually about 
2 feet long by 15 inches wide, and about 3 inches deep ; they are 
made of ordinary inch deal, planed on both sides, and the comers are 
boimd with stout sheet iron. The trays are made of various sizes to 
suit the different classes of work to be conveyed in them. The 
reader is referred to another chapter for a description of the process 
of polishing. 

Tho BoowBiug Tray. — This apparatus, which has to be subjected 
to much wear and tear, requires to be well put together, and must be 




il6 



ELEGTBO-DEPOSITION OF NICKETa 



thoroughly water-tight. A sketcli of the scouring traj generally- 
adopted is shown in Fig. io6. It is usually made from two-inch deal, 
planed on both sides ; the joints are rendered water-tight by means of 
india-rubber, and the various parts are well bound together by screwed 
bolts and nuts. The dimensions may be 6 or 8 feet long (inside), 
2 feet 6 inches wide, and about 15 or 18 inches deep. It is divided 
into two equal compartments by a wooden partition, and a stout shelf 
is fixed across one compartment, upon which is a small block of wood 
— about 7 or 8 inches long, and 2 inches square, secured to the shelf, 
by screws, from beneath, for scouring small articlei^. A water-tap, 




Fig. 106. 

with india-rubber hose, is placed at a convenient distance above the 
tray, by which means either compartment may be filled at pleasure. 
At the comer ot either compartment of the scouring tray is a flang^ 
exit pipe, let into the bottom at the tar comer, to allow the tray to be 
emptied when required. The second compartment is used as a rinsing 
trough The exit pipes are furnished with a wooden plug, which the 
workman withdraws when he desires to run off the water from either 
compartment. A wooden shelf is generally fixed at a convenient dis- 
tance above the back of the scouring tray, to hold various brushes, 
pumice-box, or other tools required in preparing work for the bath. 
and Oopp«r Work.— The articles are first suspended, by 



BRASS AND COPPER WORK. 3II 

means of short lengihs of copper wire, in the hot potash bath, whera 
they are allowed to remain until ready for scouring. The ** slinging 
wires" for this purpose, as also for suspending the articles in the 
nickel hath, should be of various thicknesses, according to the weight 
they have to sustain, and it is a good plan to keep bundles of these 
wires, cut up into regular leng^ths, bound togeth'er by a piece of the 
same wire, so that they may be readily withdrawn as required. The 
articles being taken out of the potash bath, one by one, or a few at a 
time, according to their size, are at once plunged into the water in 
either compartment of the scouring tray. They are next subjected to 
the operation of Kouring. 

Scouring. — ^This usually consists in well brushing the work with 
finely powdered pumice and water, by means of hog-hair brushes. 
Some platers prefer a mixture of pumice and rottenstone for brass 
work, as being rather less cutting, and therefore less liable to scratch 
the work so severely as the pumice and water alone. The author's 
son, Mr. A. N. Watt, has succeeded well in employing ordinary 
whiting in scouring brass and copper work, which, while suffi- 
ciently cleaning the articles, enables them to come out of the nickel 
bath in a much brighter condition than when pumice is used, and as a 
natural consequence the work requires less time and trouble in finish- 
ing. We believe that recentiy slaked lime, either alone or mixed 
with whiting, would be better still, were it not for the fact that the 
caustic lime would be iajurious to the hands of the workmen. 

In scouring the work it is placed on the shelf across the scouring 
tray ; the brush is then dipped in water and afterwards in the powdered 
pumice, or other material — which is kept in a wooden box upon the 
back shelf —and the article is well brushed all over, beginning at one 
end, and then turning the article round to brush the other ; a final 
brushing is then given all over, as quickly as possible, so as to render 
the surface uniform. As each article is brushed it is rinsed in clean 
water, the sling^g wire is then attached, and the article next dipped, 
for an instant, in the cyanide dip, again well rinsed, and immediately 
after suspended in the nickel bath, where it is allowed to remain from 
four to eight hours, according to whether the work is to be moderately 
or thoroughly coated with nickel. 

As we have before observed, all work which is to be bright when 
finished must be polished before being nickel-plated. If, however, it 
were to be immersed in the nickel bath without any further preparation 
(unless a verg slight coating of nickel were gfiven), even if perfectiy free 
from greasy matter and oxide upon its surface, the nickel would surely 
strip or peel off. Hence the operation of scouring is adopted — ^not 
alone to render the surface of the metal absolutely clean, but to give it 
an almost imaginary degree of roughness. It is a fact well known to 



3X3 ELEGTRO-DEFOSmON OF NICKEL. 

electro-depositors that when a surface of metal is perfectly bright any 
other metal deposited upon it will readily separate. The surface may 
be all but brighty and the two metals will adhere more or less firmly ; 
but if it is absolutely brighty the metals have little or no cohesion. In 
scouring, therefore, great care must be taken that the application of 
the brush and pumice has been perfectly imiform all oyer the work, 
and that the bright lustre given to it by the polisher has been 
thoroughly removed. To produce this result, the work does not 
entail laborious scrubbing y but is accomplished by a brisk brushing, 
taking care to keep the brush well charged with tiie pumice. We have 
seen men, improperly instructed in this respect, who have first dipped 
the brush in water, then in the pumice powder, and finally in the 
water again, before applying it to the work, whereby they actually 
washed away the material before the brush was applied ! Again, it is 
a common error to dip the brush in the pumice before shaking the 
superfluous water from it, which not only causes the powder to 
become deluged with water, and a considerable portion of it to be 
wasted, but in this extremely wet condition it has little effect upon 
the surface to be cleaned. The brush should only be moist when 
dipped in the powder, in which state it will take up sufficient material 
to spread over a considerable surface, and will then do its required 
work effectually, with very little waste. Some scourers are very 
wasteful in this respect, and as a rule their work is neyer properly 
deaned, or pumiced. The brushes employed in scouring are made 
from hog bristles, and are supplied, for the general purposes of the 
plater, of various widths, and are known as one-rowed, two-rowed, 
three-rowed, and four-rowed brushes, each terminating in a suitable 
handle (see Fig. 94). The brushes, in their separate sizes, may belaid 
upon the shelf behind the scouring tray, so as to be ready to hand 
when required for use, and they should on no account be used for any 
other purpose than scouring the work. New brushes may be dipped 
for an instant in the potash bath, and immediately rinsed, by which 
any greasy matter communicated to the' hairs or bristles during the 
manufacture will be rendered soluble, and will afterwards wear away 
in use. This precaution is not altogether unnecessary, since these 
brushes have frequently been used by workmen for brushing their 
dothes, and sometimes even their hair. 

Immersing the Work in the Bath. — When we bear in mind that the 
nickel anodes have a stationary or fixed position in the bath, and that 
consequently a very large surface of the positive electrode is exposed, 
it will be at once apparent that some means must be adopted, when 
the first batch of articles are being placed in the bath, to prevent the 
deposit from taking place too rapidly (owing to the excess of anode 
surface), and thereby causing tiie work to ** bum," as it is called. 



NIOKELINa SMALL STEEL ARTICLES. 3X3 

When dynamo or ma^eto -electric machines are employed, reaiatanee 
coils are used to regulate or control the force of the current, as we shall 
explain hereafter ; but although such coils are less necessary when 
depositing by battery power, some other equally effective means must 
be adopted. The most simple plan is to hook one of the anodes on the 
negative conducting rod, at its farthest end from the battery, and 
there to leave it until the rod is nearly supplied with work, when it 
may be removed and put in its proper place on the positive rod. By 
adopting this practice with each suspending rod in turn the " buxn- 
infiT '' of the work is prevented, and depotdtion takes place gradually. 

When work of moderate dimensions — as brass taps, for example — and 
very small articles are in hand for nickeUng, the larger work should 
be put into the bath first, and the smaller work 
then introduced between other pieces of larger work. 
It is also usual to commence suspending the work 
from the end of the rod nearest the battery (where 
the power is weakest) rather than from the opposite 
end. Small articles — such as screws, for example 
— should not be slung singly, but several of them 
suspended from the same wire, as in Fig. 107, in 
such a way as not to be in contact with each other. 

Mlek«Uiis Bmmri StMl ArtielM.*— This class of 
work, after deaniug, immersion in the acid dip, and Fig. 107. 
rinsing, should be suspended in the bath, ii prac- 
ticable, between other articles of larger dimensions, so that depo- 
sition may take place slowly and gradually; otherwise the articles 
are very liable to strip. This precaution is specially necessary in 
nickeling small dentists' tools, as excavators, &c., which, when ex- 
posed to too strong a current, are apt to bum at the lower end and 
strip. In nickeling such work the rule is, after the article has be- 
come ** struck " (that is, coated all over), to allow the deposit to take 
place very slowly, especially during the first half -hour's immersion. 
When battery power is used, from one to two hours* immersion will 
be sufficient for a serviceable coating upon the smaller dental tools, but 
a somewhat longer period — ^say, up to three hours — should be given to 
dental forceps. When a dynamo-machine is employed, about half this 
time will be sufficient. It is very important that steel work shoiild be 
placed in the bath immediately after being cleaned, since even a few 
moments' exposure to the air or immersion in water will cause an 
invisible film of oxide to form on the surface, which will prevent the 
nickel from firmly adhering to the steel. After nickeling, the articles 
are rinsed in hot water and handed to the finisher, who gives them the 




* See also pp. 461 et seq. 



314 SLBCTRO-DEPOBinON OF NICKEL. 

necessary high polish. Small steel or iron articles which are not 
required to receive a stout coating of nickel are first steeped for & 
short time in the potash bath, and after being rinsed are dipped for a 
moment in the hydrochloric acid dip, ag^ain rinsed, and put into the 
nickeling bath, without any preparatory scouring, and given a short 
immersion only — say, half -an -hour. Such work is generally finished 
by being dollied only, which brings up the surface to its proper 
brightness. 

llljikrting flmaU Braas and Oopptr Artlelts. — ^When these have 
to receive a good coating and afterwards to be finished bright, they 
must be scoured after polishing, and treated in all respects the same 
as larger work. Articles which are not required to be stoutly mckded, 
however, but only moderately well coated with this metal, may be 
polished with the rouge composition referred to in another chapter, 
instead of with lime in the usual way, and then placed in the bath 
without previous scouring. When they have received a moderate coat- 
ing of nickel they are rinsed in hot water, and afterwards finished 
with the mop, or dolly, with the aid of the same composition. This 
method of treating small brass work — ^whioh we believe is of American 
orig^ — is especially suitable for umbrella mounts, reticule and purse 
frames, cheap fancy work, and such articles as are not liable to much 
friction in use. Small brass articles which are not required to be 
bright are first put into the potash bath for a short time, and after 
rinsing they are dipped in ordinary dipping acid, again well rinsed 
in several waters, and then put into the nickel bath, in which they 
receive a deposit according to the nature and quality of the work and 
the price to be paid for it, a short immersion, in many oases, being all 
that is given when the price is low. 

HlolfHng toy Hjnuuiio-ctoetrielty. — Although a very consider- 
able amount of work of all kinds is coated with nickel by battery 
current, by far the greater portion passes through the hands of those 
who adopt dynamo or magneto-electric machines as the source of 
electricity. Lideed, if it were not for the gfreat advantages which these 
machines present in the deposition of this metal, the art of nickel- 
plating would never have attained its present magnitude. In arrang- 
ing a nickeling plant upon a large scale, the baths should be placed 
parallel to each other, having sufBcient space between each vat for 
the free passage of the workmen ; and the dynamo-machine should be 
stationed conveniently near the vats, so as to be under the immediate 
control of the plater. The conducting wires should be so arranged 
that the current may be applied to one or more of the baths, as 
occasion may require, and this may be most conveniently effected by 
fixing two stout brass or copper rods, by means of insulating brackets, 
to the wall of the apartment nearest the nickel tanks ; these leading 



3I<S EI.ECT&O-D1JPOBITI0I1 OF NICKCL. 

wiTM or condudJng rods mustihavo attaohed to them a Beriee of binding 
screws, correspouding in number ta tho connecting' screws of the 
suspending rods. A large form of nickel tank, capable of holding 
from 130 to 50a gallons of BolutJon, is shown in Fig. 109. To couneoC 
the machine with the leading rods stout copper wire is used, die 
thickness of which is regulated according to the power of the machine. 
For a medinm-sized Weston, half-inch copper vire ia generally used, 
but for larger machines the wire emplojed is usually three-fourths to 
one inch in thickness. To convey the current from the leading rods to 
the baths, the wire need not be so stout as in the former case, about one- 
haJf the thickness being aufflcient. To give motion to the machine 
a couater-ehaft is usually flied overhead, with its driving puU^ 
immediately in a line with the pulley of the machine, the two being 
connected by a belt in the usual way. The coimter-ahaft, an im- 



Fig, 109. 

proved form of which has been introduced by Carlyle, ia shown in Rg. 
I to, is furnished with a long iron handle within reach , by the raising 
or lowering ot which the belt in placed on the fast or loose pulley of the 
shaft, according to whether the machine is required to run or stop. 
To regulate the amount of current entering the respeotive baths, a 
resistance coil is either attached to the end of each bath or fastened 
to the wall facing the end of each vat, and thene coils are int^posed 
in the circuit by means of short conducting wires. (See Fig. 108.) 

In working large tanks of nicket Bolution for coating articles of 
moderate size, as taps, spurs, bits, table lamps, &c., three rows of 
anodes are generally used, which are thus disposed : one row of anodea 
is suspended from a conducting rod on each side of the tank, and the 
third row is placed in the centre of the bath, midway between the 
other two. Two rods tor supporting the work to be nickeled are 
pUced between the fide and centre rows of anodes, by which atlBngo- 
ment the Buspi^ded artirlcs will be exposed to the action of two anode 
surfaces. The three anode rods miiKt be united at their ends by means 



mOKELINO BY DYMAMO-ELECTRICITr. 317 

of tMok copper wire, in nhich case one binding screw only, attached 

to the end of one of the Bide tmU, nill be necessary to connect tho 

anodee with the podtiTe le&ding: wire of the machine ; or a separate 

^^_^__^^________^_^^__ binding screw may be 

connected to the end of 
 each Tod, and the con- 
neetioD with the leading 
roda completed witli 
short lengths of stout 
wire. The latter plan 
is the boat, since on< 
or more rows of anodes 
can be more readily 
thrown out of circnit 
from the binding sorew at 

I Wannasa, Jtc— Large 

&B beer and wine mullers, 
it of BUrface they present, 
e a different arrangement 
iopted for ordinary work, 
mown that all metals re- 
on the enifaoes facing the 
, silvering, and coppering 
'ate extent upon those aur- 
directly face the anode, in 
ferent, ft» under the same 
lid take place at the oppo- 
an anode wexe suspended 
.rrangament we have de- 
scribed. Since mnllerH, and articles of the class to which thoy belong, 
prcoant an extensive convex enrfaoe, it is neceesary, in order to secure 
a uniform coating of nickel, to turmund snch work witb anodee as far 
as is practicable. This is ordinarily done in the following manner : — 
The centre row of anodes is first removed ; two short brass rods are 
thm placed across the other positive rods, about 2 feet apart, and upon 
each of these is suspended one or more anodes, according to their width. 
The centre conducting rod. lately occupied by the anodes, is now used 
as the suspending rod for the muller. Where more than one nickel batb 
is employed, it is best to keep one of these speoially for mullers and 
other large work, in which case two rows of anodes only and one 
centre negative rod, should be applied. The bath ua xl for nickeling 
mullers should be kept covered with a frame, upon which oiled calico is 
Btretehed, to protect tliewoik from dust The drawing (Fig. iit) 



3^8 ELECTRO-DEPOSITION OF NICKEL. 

shows the relative position of the muUer and the suTroiinding anodee. 
When the article has been in the bath some time, its position must be 
reversed — ^that is to say it must be inverted — so as to equalise the coat- 
ing as far as possible, since the deposit always occurs most energetic- 
ally at the lower surface of the article in the solution. In a loo-gallon 
bath only a single mullet, or similar article, could be nickeled at one 
time ; in other words, it should have the whole bath to itself. When 
dynamo-machines are employed, however, the baths seldom consist of 
less than 250 gallons of solution. 

In nickeling the above class of work gfreat care and smartness of 
manipulation are necessary. The work requires to be well and briskly 
btushed with pumice after removal from the potash bath, and after 
being rinsed is passed through the cyanide dip for a moment, and 
again well rinsed, and no time should now be lost in getting it into 
the nickel bath, and connecting it to the conducting rod. Soon after 
immersion the characteristic whiteness of the nickel should be visible 
upon its surface, as evidence that cur- 
rent is sufficiently strong to do the work 
required of it. Such being the case, the 
article must be left for awhile, after 
which it may be gently moved up and 
down by its aling^g wires (but not out 
of the solution) to disperse any dusty 
particles that may have settled upon 
jij„ ^ its upper surface, since these, how- 
ever slight and imperceptible, will 
sometimes cause a rough and irregular deposit, which wiU g^ve some 
trouble to the polisher when finishing the article. When plating 
work of this description in a bath which has been long in use, the 
anodes should be arranged as described some time before a muller is 
placed in the bath, so that the sediment (which always accumulates 
at the bottom of the vessel), if disturbed, may have time to subside ; 
and in placing the article in the bath care should be taken to lower it 
gfently, so as not to disturb the '* mud,'* if we may call it so, at the 
bottom. The opposite of this careful treatment needs only to be tried 
once to make the plater exceedingly particular thereafter. 

However careful the operator may be, it sometimes happens that 
certain parts of the article will become bare, or *< out through," as it 
is termed, during the process of finishing, in which case it is sent back 
from the polishing-room to the plater, who must in some way deposit 
nickel upon the exposed surface. This is accomplished by applying 
the '* doctor," by which means a coating of metal is deposited upon 
the naked spot in the following way : a piece of stout copper wire, 
about a foot in length, is bent in the form of a hook at each end ; a 



NICKELING BAR FITTINGS, ETC. 3^9 

small piece of nickel, about an inoli and a half square, is attached to 
one of the hooks, and this is wrapped up in several folds of rag, secured 
to the wire by twine. The other hook is connected by a long copper 
wire to the anode rod, and the article to be doctored connected in the 
same way to the negative rod. Now dip the rag-end of the wire in the 
nickel bath, and apply it to the bare spot (which should be previously 
brushed over lightly with pumice), keeping it in contact for a few 
seconds, then dip it in the bath again and apply as before, repeating 
the operation every half -minute or so, until a sufficient deposit of nickel 
has been given to the spot to enable the finisher to apply the *' dolly,'* 
and thus render this part as bright as the rest of the article. Although 
this may not be considered a very conscientious method of getting 
over the difficulty, unless performed with patience, so as to impart 
something more than a mere film upon the bare place, it must be borne 
in mind that if the entire article were to be re-nickeled this would 
involve an amount of trouble and expense of labour which would never 
be compensated for. The 'Moctoring," however, should always be 
done welly and since the articles to which it is usually applied are 
rarely subjected to such friction as would affect so hard a metal as 
nickel, the defective portion of the work may cause little or no annoy- 
ance to the owner. 

mdMUiiff Bar nttliissy Sanitary Work, *g. — ^Articles of this 
description require to be thoroughly well coated with nickel, and finished 
in the best possible manner. Before submitting such work to any 
preparatory process, the plater should carefully examine each piece to 
ascertain if it has been properly polished and all scratches and file 
marks obliterated, since if any of these be present after the article is 
nickeled and finished they will g^atly impair the appearance of the 
work, while the finisher will be quite powerless to remove them 
without cutting through the nickel deposit. A careful examination 
of all work should be made by the plater before allowing it to enter 
the potash bath, and since in most establishments the polishing and 
finishing are done on the establishment, a proper understanding should 
exist between the finisher and plater as to the absolute necessity of 
having the work finished in the best possible manner. The articles, 
after being approved by the plater, are handed to the scourer, who con- 
nects a stout copper wire to each piece, and slingv them to the suspend- 
ing rod of the potash bath ; after a short time these are removed, one 
or more at a time, according to their size, and after rinsing are taken 
to the scouring tray, where they are well brushed with pumice, then weU 
rinsed in the water-trough of the scouring tray, and dipped for a 
moment in the cyanide dip. After being again well rinsed thev are 
promptly suspended in the nickel bath. The articles should be 
thoroughly rinsed after being in the cyanide dip to prevent the intro- 



320 



EJLECTBO 1>EP0SITI0N OF NICKEL. 



duction of this gnbstance into the nickel bath. About two and a half 
hours* immersion in the bath, when a dynamo-machine is used, will be 
sufficient time to obtain a good deposit. It may be well to remark here, 
that however desirous a nickel-plater may be to give a good thick 
coating to his work, there is a limit, as far as nickel is concerned, 
which must on no account be exceeded ; otherwise the deposited will 
strip or peel ofP the work, even without touching. Indeed, we have 
known the nickel, when the articles have been too long in the bath, to 
separate from the work and curl up in flakes, while a second deposit 
has taken place upon the parts thus deprived of metal. 

If tcK»ltng Iiong Pl<!e— of IW'ork. — Hand-rails, cornice poles, the 
framework of shop fronts, and other long pieces of work, require to be 
nickeled in a bath of suitable dimensions : for this purpose a tank of 
the form shown in Fig. 1 12 is generally used, which is supplied with 
a series of short anodes to suit the form of the vessel. Such a 
tank should be about 12 feet long, 20 inches deep, and about 
18 inches wide. Since articles of this character do not very fro- 




^ 



Fig. 112. 

quently come into the hand of the plater, it is unnecessary to employ 
special dipping baths for potash and cyanide ; the hot potash liquor 
may be poured over the article from a jug, beginning at one end, and 
continuing Uie operation until the whole surface has been washed 
over with the hot liquor. After rinsing and scouring, the cyanide dip 
may be applied, quickly, in the same way. The article must now be 
well rinsed and got into the bath as promptly as possible. 

l>«ad Work. — Ships* deck lamps, and many other classes of work, 
which are not required to be polished, but left dead — that is, just as they 
come out of the nickel bath — are potashed, as usual, and after scour- 
ing and rinsing placed in the bath and allowed to remain until suffi- 
ciently coated. Since work of this kind should look as white as 
deposited nickel is capable of becoming, it is necessary, more 
especially during the last few minutes' immersion, to employ a 
strong current. When the articles are sufficiently coated they must 
be taken out of the bath, one at a time, and at once plunged into 
perfectly clean hot water for a few moments, and then placed aside to 
dry spontaneously. Since dead nickel is very readily stained or soiled 
even when touched with clean hands, the work should be handled as 



MICXXUNO BICYCLES, ETO. 32 I 

little iM powble before being' sent home to the customer. We havo 
known iustancea in vhich dead nickel work, Thich from its silvery 
whiteneu was pleaaiiie: to behold after remoTal from the bath, looked 
dirty and patchy before delivery to the cuatomer, merely through the 
careless fingering to which it had been subjected by the warehouse- 
man and others. 

WlckdlBc mtaw* Bronte, *«. — These are usually nickeled in a vat 
spooially constructed for the purpose, the fonn of which is shown in 
Fig. 1 1 J. It oonmsts of a wooden vessel about 5 feet deep, 4 feet 
long, and about iS inches wide, held 
together by bolts and screws, and is 
sometimes lined with pitch owing to the 
difficulty of lining such a vessel witb 
lead. The anodes should be at least 
30 inches long, and since only the fronts 
of stoves require to receive the coating 
of nickel, a single row of anodes only ii 
necessary. This class of work is usually 
sent to the plating works in a polished 
state — that is, auch parts as are to be 
bright are pnt in this condition by the 
manufactuiers. To prepare the front 
tor plating, it is first put into the potash 
bath as usual, and after a short immeniion ^>S' "3- 

is well rinsed and scoured with pumice ; 

it is next dipped in the hydrochloric add dipping bath, again rinsed, 
and then put into the nickel vat with all poxnililc de>-patch. After 
about two to three hours' immersion, the article is steeped in hot 
water, and when dry is handed to the finisher. Large pieces of orna- 
mental iron work which have to be left dead may be also nickeled in 
the "stove bath." 

Hlekalinc Bteyel**, Jtc — When this class of work in sent to the 
plater in parts, these may be nickeled in the ordinary bath with the 
exception of the rim of the wheel, and all parts must be polished and 
treated in the same way as other steel work. A convenient method 
of suspending bicycle spokes in the bath is shown in Fig. 1 14. The 
copper alinging wire is simply coiled into a series of equidistant 
loops, through which the wires of the spokes pass freely, and when 
a sufBcient number have been wi'cd in this way the two ends of 
the slinging wire are pulled with both hands, t^ which the loops becomt 
tightened and the spokes held firmly. They are then lowered into the 
hnlh and suspended from Qie negative rod as shown in the engraving. 
After a short immersion, each spoke is shifted a little, so as to allow 
the wire mark to be coated, and this operation is repeated several 




0- 



322 ELECTRO-DEPOSITION OF NICKEL. 

times during their immersion in the bath, so that the ooating may be 
as regular tia possible. With a dynamo-machine a sufficient coating 
will be obtained in about an hour and a half. In nickeling the back- 
bone and fork of a bicycle, and the larger parts of tricydee, these 
pieces should be frequently shifted in the bath to ensure uniformily 
of deposit, for it must be borne in mind that from the peculi^* 
curved form of the backbone, for example, the parts farthest from 

the anodes will receive the least de- 
-^ posit. In cases where the bath is not 
large enough to take in the entire rim 
of a large bicycle wheel, it is usual to 
nickel one-half at a time ; when this 
has to be resorted to, great care must 
be taken to well clean the line where 
the deposited metal and the bare steel 
meet, otherwise, when depositing upon 
the second or third portion of the jrim. 
Pig J j^ the nickel will strip at the junction of 

the separate deposits. In each case, a 
portion of the nickeled part should be immersed in the bath with the 
uncoated surface. When finishing the rim the polisher should be par- 
ticularly careful with these junctions of the separate deposits, otherwise 
he may readily cut through the nickel and expose the underlying 
metal. In establishments where the nickeling of bicycles forms a 
special branch of the business, baths of suitable dimensions are em- 
ployed for depositing nickel upon the larger pieces of bicycle and 
tricycle work. 

Wiokullng Bd o o n d-toand Bleydes. — Some few years agt), when 
nickel-plated bicycles first appeared in the market, the whole bicycle 
fraternity, who had been accustomed to plain steel or painted wheelen-., 
looked with admiration, if not with envy, upon those who appeared 
amongst them upon their brilliant and elegant nickel-plat'cd roadstern. 
At the time we speak of there was a rush of bicyclists at the various 
nickel-plating works, and anxious inquiries were made as to the possi- 
bility of nickeling bicycles which had become hideously rusty from 
neglect, or even those which had been more carefully treated . Gould not 
a bicycle be popped in the solution, or whatever it was, and covered 
with the stuff, so as to come out bright like those in the shop win- 
dows? Questions such as these were asked, even with apparent 
seriousness. One firm, after consulting the foreman, determined to 
undertake the task of nickeling one of these second-hand bicycles, and 
after a good deal of trouble — since it was probably the first time such 
a thing had been att<»mpted — the task was accomplished with consider- 
able success, and the owner cheerfully paid the cost of its transniutii^ 
tlon, three pounds ten shilliugs — a price that in these days of Itrisk 



NICKEUNO SWOBD SCABBABDS. 3^3 

competition would scarcely be thought of. Since ihe period leferred 
to, the nickeling of bicycles has become an ordinary matter of detail in 
most nickel-plating works. 

In preparing a bicycle for nickeling, the principal parts must first 
be taken asunder. The head nut is first unscrewed to liberate the 
backbone ; the bolt which runs through the fork of the backbone 
must next be removed, by which the small wheel becomes dislodged ; 
the bolt is next withdrawn from the hub of the large wheel, which 
liberates the fork ; the spring is next disconnected by removing the 
screws at the head and back of the spring. All these parts, with the 
exception of the wheels, must pass through the hands of the polisher. 
It is not usual to remove the spokes, which in the case of a much-used 
machine would entail considerable risk, since much difficulty would 
occur not only in removing but in replacing them. The wheels arc, 
therefore, nickeled entire, but before doing so they must be polished 
in the best way possible by hand, since it would not only be dangerous, 
but impracticable, to polish them at the lathe. The spokes and other 
parts of the wheel are first well rubbed with emery-cloth of various 
degrees of fineness, and then hand-buffed with chamois-leather, first 
with trent-sand, and afterwards with lime, as good a surface as 
possible being produced by these means. The wheels and other parts, 
when poliflhed, are placed in the hot potash bath, where they are 
allowed to remain for a considerable time to remove the large amount 
of grease which invariably hangs about this class of work. To assist 
in the removal of this, the pieces are brushed over while in the potash 
tank ; it is important that the potash liquor be in an active condition — 
that is, rich in the caustic alkali — or it will fail to kill the grease, as it 
is termed, or convert it into soap. After being thus cleansed in the 
potash bath, the work is removed piece by piece and rinsed, after 
which it is briskly scoured, and, after again rinsing, is passed through 
the acid dip for an instant, again well rinsed, and put into the nickel 
tank. When all parts of the machine are nickeled they are handed 
to the finisher, who *' limes'' them ; that is, the backboDfi, fork, and 
other pieces, excepting the wheels, are polished and dollied with 
Sheffield lime at the lathe. The wheels, as before, are finished 
with lime, applied, by means of chamois-leather, by hand. The 
various parts are then readjusted, the machine carefully wiped all 
over, and it is then ready for the customer. Should the india-rubber 
tyre come off the wheel after being in the nickel bath, it may be 
replaced by fusing india-rubber cement upon the periphery of the 
wheel by heating over a gas-burner. While the cement is hot the 
tyre should be replaced in its position. 

IflclinHng Sword Scabbards, Ac. — It not unfrequently occurs that 
a nickel-plater receives a sword and sheath with instruction to nickel 
the latter only. When Huch is the case, the sword should be with- 



1(24. ELECTRO-DEPOSITION OF NICKEL. 

drawn and placed where it cannot become moistened by the steam from 
the potash tank or otherwise injured. To prepare the scabbard for 
plating, the thin laths of wood with which it is lined must first be 
removed, since if the sheath were placed in the nickel bath without 
doing so, these pieces of wood, by absorbing the nickel solution, would 
become so completely saturated that much difficulty would afterwards 
occur in drying them. We have heard of instances in which this 
precaution has not been observed, and as a consequence the sword, 
after being sheathed for some time — probably for some months — was 
not only thickly coated with rust, but deeply corroded, owing possibly 
to voltaic action set up by the nickel solution absorbed by the wooden 
lining ; in one such instance the sword had become so firmly fixed in 
the scabbard, through the oxidation of its blade, that it was unsheathed 
with great difficulty, and when at last withdrawn it was thickly 
coated with rust. The strips of wood referred to must, therefore, in 
all cases be removed before the sheath is immersed in either of the 
liquids employed. To do this, remove the screw which unites the collar 
to the upper part of the sheath ; remove the collar, and with the blade 
of a knife loosen the strips of wood and withdraw them from the 
sheath, taking care to remove all of them. The two parts of the 
sheath and the screw must then be handed to the polisher, and when 
returned to the plating-shop they are first to be potashed, and after- 
wards scoured, passed through the acid dip, and after well rinsing put 
into the nickel bath, in which the scabbard should be slung horizon- 
tally, so as to get as uniform a deposit as possible. The collar and 
screw, slung upon separate wires, should then be placed in the bath, 
care being taken that the latter does not receive too heavy a coating, 
or some difficulty may arise in replacing it. To avoid this, the head 
of the screw only should bo put into the bath. To prevent the nickel 
dei>osit from entering the screw-hole of the scabbard, a small plug of 
wood may be forced into the hole before the latter is put into the 
bath. "V^Tien the several part« nre sufficiently c^oated, whitjh occupies 
about two hours, they are removed from the bath, rinsed in hot 
water, and well dried ; they are then sent to the finisher, after 
which any lime that may have got into the screw-hole must be 
removed with a brush ; the strips of wood and collar are then re- 
adjusted, the scabbard carefully wiped with a chamois-leather, and 
the sword replaced. 

HlokaUag H a mi » Fnniltare, Bits, 8pim, Ac.— This class of 
work, when properly nickeled, may be considered one of the most use- 
ful applications of the nickel-plating art, but unfortunately— as is also 
the case with many other articles — a good deal of indifferent nickel- 
ing, the consequence, in a great measure, of unwholesome competi- 
tion:, has appeared from time to time, which has had the effect of 



NIOKELING HABME88 FUBKITTJBB, ETC. 395 

shaking the confidence of manufacturers who were at one time much 
disposed to encourage this branch of electro-deposition. That com- 
petition may be carried too far is evidenced by the extremely low 
prices which are asked for nickeling articles at the present time, as 
compared with, say, five years ag^ ; in many instances (if the work 
were done conscientiously) below the fair cost of polishing. When it 
is borne in mind that bits, spurs, stirrups, and all kinds of harness 
work are necessarily subjected to severe treatment in use, and that to 
nickel -plate such articles badly, for a temporary advantage, has a 
poKitive tendency, if not to close this market entirely against nickel- 
plating, at least to confine it solely to those who have a known repu- 
tation for doing their work properly, and can therefore be relied upon. 
We are led to make these remarks, m passant, because we have an 
earnest desire that nickcl-pkting should not lose its character for 
absolute usefulness for the temporary advantages of competition. We 
say temporary f because we know that much mischief has accrued to the 
art generally in consequence of work undertaken at prices that could 
not yield a profit being so badly nickel-plated, that some manufac- 
turers have ceased to avail themselves of this branch of industry except 
in cases of absolute necessity. 

In nickeling the class of work referred to, all the parts which are to 
be bright when finished must, as in all other cases, be previously well 
polished. Sometimes the articles are sent from the manufactory in this 
condition, but when such is not the case the pieces must be first handed 
to the polisher, and when returned to the plater they are to be 
potashed, scoured, and passed through the acid dip, and rinsed as be- 
fore, and then placed in the nickel vat, where they should remain (with 
an occasional shifting) for about an hour and a half, by which time, with a 
good dynamo, they will have acquired as thick a coating as may be given 
without fear of peeling. After removal from the bath and rinsing in 
hot water, the articles are placed in the finisher's hands, and when 
finished, the lime which lodges in the crevices should be brushed away 
and the articles then wiped with a chamois-leather and wrapped up. 
The bru.shing of work after finishing is too often neglected, and 
we have known of many complaints having been made by customers of 
the '' filthy state'' in which nickel-plated work has been received, 
owing to tile lime falling out of tubes and hollows and from other 
parts of articles when they have been unpacked and examined on the 
counter. All work, after lime-finishing, should be well brushed, and 
wiped with a leather ; it does not occupy much time, and should be 
considered a necessary detail of the busiQess. 

melMUns Cast-iron VTotlL* — Articles of this class — as kilting 
machines, for example — are first potashed in the usual way, and after 
rinsing they are immersed in a pickle composed of half -n pound of 



3*^ ELECTRO-DEPOSITION OF NTCKRL. 

milphuric acid to each gallon of water used to make up the bath. In 
thifl they are allowed to remain for about half-an-hour, when they 
are removed, well rinsed, and scoured : for this purpose the author 
prefers sand to pumice powder, from the fact that when the former is 
used the articles have a brighter or more lustrous appearance when 
nickeled than if pumice be employed, besides which sand is cheaper. It 
frequently occurs, in oast-iron work, that numerous cavities, or *' sand- 
holes,*' of greater or less magnitude, become visible after pickling and 
scouring the work, and since the nickel will probably refuse to enter 
these hollows — which is generally the case — ^it may be advisable in 
the first instance to give the article a coating of copper in an alkaline 
coppering bath, by which these cavities, if they are clean after sand- 
brushing, will become oopx>ered with the rest of the article and the 
nickel will follow. Sometimes, however, the sand -holes are filled with 
flux or oxide of iron, in which case the former must be picked out with 
a hard steel point, and the hollow discoloured by oxide of iron should 
be scraped out with a small steel scraper. This being done, the 
article must be again sand-brushed and put into the coppering bath 
until coated all over with a slight iilm of copper. We have seen large 
iron castings in which the sand-holes have been so large and deep that 
the workmen at the foundry have been compelled to plug them with 
lead. Such defects as these should be looked for by the plater, and if 
any of these leaden stoppings appear it will be undoubtedly advisable 
to coat the article with copper before nickeling it, otherwise the nickel 
will not firmly adhere to the leaden stoppings. We should in all 
cases prefer to give a coating of copper to cast-iron work in the alka- 
line bath, since the cast metal is a very indifferent conductor, and re- 
quires, when not coated with copper, a very strong current ; indeed, a 
few tolerably large pieces of cast iron uncoppered will often monopo- 
lise the whole of the current from a dynamo -electric machine, and 
thereby hinder the progress of the other work. 

lfick#Hng Clialn WotIl. — It sometimes happens that steel, iron, 
and brass chains of considerable length are required to be nickeled, in 

which case the object must be 
treated according to the di- 
rections given for the respective 
metals. A convenient method 
of slinging a chain in the nickel 
bath is shown in Fig. 1 15. A 
number of pieces of stout cop- 
per wire, of uniform length, 
Fig. 1 15. ^yg p^^ while the chain is beinjr 

scoured, and both ends of the wires are dipped in dipping acid for 
a moment, and then well rinsed. The wirea are then turned up into 




RE-NICKELIKO OLD WORK. 7,2 'J 

the form of a liook at one end, and when the chain is ready for nling- 
ing, the hoolu are passed through the links one at a time and at equal 
distances apart, each portion heing lowered into the bath and sus- 
pended by bending the end of the wire over the conducting rod, as in 
the figure ; in this way two men can immerse a chain of considerable 
length in a very few moments. After a short immersion, each hook 
may be shifted one Unk, to allow the wire mark to be nickeled, or the 
same link may be inverted, as preferred. 

Br»-Hlek«lliis Old Work. — When goods which have been nickel- 
plated require to be re-nickeled, it is always better to first remove the 
old coating by means of a stripping solution, for the reason, as we have 
before remarked, that nickel will not adhere to a coating of the sanio 
metal. A stripping bath for nickel may be composed as follows : — 

Oil of vitriol i6 pounds. 

Nitric acid 4 m 

Water 2 quarts. 

Add the oil of vitriol to the water (not the reverse, which it is danger- 
ous to do) gradually, and when the mixture has cooled down add the 
nitric acid, and stir the mixture with a glass rod. When cold, it is 
ready for use. The articles to be stripped should be attached to a 
piece of stout brass or copper wire and placed in the stripping liquid, 
and after a few moments they should be lifted by the wire and 
examined. If the articles are of a cheap class of work, the small 
amount of nickel upon them may become dissolved off in less than half 
a minute : this is generally the case with American, French, and 
German goods. The better qualities of English nickel-plating will 
sometimes occupy many minutes before the whole of the nickel will 
oome off. This great difference in the thickness of the nickel-plating 
necessitates much caution and judgment on the part of the workman, 
for if he were to treat all classes of work alike, the metal of which the 
thinly-coated articles are made would become severely acted upon if 
left in the stripping bath while work of a better class was being dc' 
nickeled, as we may term it. The operation of stripping should be 
conducted in the open air, or in a iire-place with good draught, so 
that the acid fumes may escape through the chimney. From the 
moment the articles are immersed in the stripping bath they should be 
constantly watched, being raised out of the bath frequently to see 
how the operation progresses, and they should not on any account be 
allowed to remain in the liquid one moment after the nickel has been 
dissolved from the surface, but should be immediately removed and 
plunged into cold water. On the other hand care must be taken to 
remove all the nickel, for if patches of this metal be left in parts it 
wiU give the polisher some trouble to remove it,, owing to the gre it 



^23 ELECTRO-DEPOSITION OF NICEBL. 

hardness of nickel as compared with the brass or copper of which the 
article may be composed. When the stripping of brass work has been 
properly conducted, the surface of the stripped article presents a 
smooth and bright surface, but little affected by the acid bath. 

Nickel may be removed from the articles by means of ihe battery or 
dynamo -machine, by making them the anodes in a nickel bath ; but 
in this case a separate solution should be employed for the purpose ; or 
a bath may be made with dilute sulphuric or hydrochloric acid ; the 
stripping solution, however, when in good condition and used with 
care, is not only quick in its effect, but comparatively harmless to the 
underlying metal, if proper judgement and care have been exercised. 
Work which is in any way greasy shoidd be steeped in the potash bath 
before stripping. 

After the work has been stripped and thoroughly well rinsed, it 
should be dipped in boiling water, and then laid aside to dry sponta- 
neously ; it is next sent to the polishing room, where it must be 
polished and finished in the same way as new work, and afterwards 
treated in the nickeling room with as much care and in the same way 
as new goods. 

Wickl-flictng Slaetrotypes. — In printing from electrotypes with 
coloured inks, but more especially with vermilion inks, which are 
prepared from a mercurial pigment, not only is the surface of the 
electrotype injuriously affected by the mercury forming an amalgam 
with the copper, but the colours are also seriously impaired by the de- 
composition which is involved. To avoid this it is frequently the 
practice to give electrotypes to be used for such purposes a coating of 
nickel, which effectually protects the copper from injury. In some 
printing establishments a nickel bath Ls kept specially for this purpose. 
The electrotypes, after being backed up and prepa^^d for mounting 
iu the usual way, are lightly brushed over with a ley of potash, and 
after well rinsing are suspended in the nickel bath for about an hour 
or so, by which time they generally receive a sufficient coating of 
nickel. Great care should be taken, however, not to employ too 
strong a current, lest the lower comers of the electrotype should be- 
come burn if as it is called, by which a rough surface is produced, from 
which the ink, in subsequent printing, would fail to deliver properly ; 
this defect, however, is readily avoided with care, and by occasionally 
reversing the x>o8ition of the plate while in the bath. 

For nickel-facmg electros of moderate dimensions, an oval stone- 
ware pan, capable of holding about ten to fifteen gallons of solution, 
miiy be used. The nickeling bath should consist of about three- 
quarters of a pound of good nickel salts (double sulphate of nickel 
and ammonia) to each gallon of water. The salts should be dissolved 
in hot water and tiltered into the containing vessel thro.igh a piece of 



NICKEUNO FBIMTINO ROLLEB& 329 

unbleached calico. The anodes may consist of two plates of rolled 
nickel, each about 12 inches long by 6 inches wide, these being 
suspended in the bath by hooks from a brass rod laid across the vat. 
A Bunsen battery of about one g^on cax>acity will give a current 
sufficient for nickeling electros of moderate Hize. The positive elec- 
trode (the wire proceeding from the carbon of the battery) is to be 
connected to the brass rod supporting the anodes, and a similar rod, 
connected to the zinc of the battery, is to be laid across the vat in 
readiness to receive the prepared electros to be nickeled. The suspend- 
ing rods and all binding screw connections must be kept perfectly 
clean. 

When putting an electro in the bath, care must be taken to expose 
its face to the anodes, otherwise little or no deposit wiU take place 
upon this surface. If desired, a second row of anodes and an additional 
negative rod for supporting electrotypes may be employed, in which 
case the electros must be all suspended back to back, so as to face the 
anodes. An additional battery will be required. The faces of the 
electros may be placed within 3 or 4 inches of the anodes, and 
each should be supported by two wires passed through the nail holes 
in the backing metal which are nearest the comers. 

niokalliiff Wlr* Oaiis«. — Hessrs. Louis Lang & Son obtained a 
patent in 1 88 1 for a method of nickeling wire gauze, or wire to be 
woven into gauze, more especially for the purposes of paper manufac- 
ture. These wires, which are generally of copper or brass, are liable 
to be attacked by the small quantities of chlorine which generally re- 
main in the paper pxdp, by which the gauze wire eventually suffers 
injury. To nickel wire before it is woven, it is wound on a bobbin, 
and immersed in a nickel bath, in which it is coated with nickel in the 
usual way ; it is then unwound and re-wound on to another bobbin, 
and re-immersed in the nickel bath as before, so as to coat such 
surfaces as were in contact with each other and with the first bob- 
bin. To deposit nickel on the woven tissue, it may either be coated 
in its entire length, as it leaves the loom, or in detached pieces. For 
this purpose the wire gauze is first immersed in a pickle bath, and 
next in the nickel solution. On leaving the latter it is rinsed, and 
then placed in a hot-air chamber, and when thoroughly dry may be 
rolled up again ready for use. 

HlelfHng Pilntliis XoUmts. — Mr. Appleton obtained several 
patents in 1883 for coating with nickel the engraved rollers used for 
printing and embossing cotton and other woven fabrics, to protect 
them from the chemical action of the various colours and chemical 
matters used in calico printing, &c., by which the copper rollers be- 
oomo deteriorated. Nickel-plated roUers, moreover, presenting a much 
harder surface than copper, are far more durable. The rollers are first 



330 KLECTRO-nEPOSITlON OF NICKEL. 

engraved as usual, after which they are immersed in any ordinary 
nickel bath. The inventor finds it advantageous, in order to secure 
a uniform coating of nickel, to ** vibrate, agitate, oscillate, or rotate 
the roller continuously, or intermittently,** while the deposition is 
taking place. He has found, however, some difficulty in obtaining a 
firm deposit, *' owing to the formation of gas bubbles upon the surface 
of the roller, and the difficulty in dislodging them. To obviate this 
he finds it advantageous to employ " a brush, which is in contact with 
the roller during the plating operation, the roUer being rotated con- 
tinuously, or intermittently, as preferred." The brush is suspended 
from the cathode rod, so that the bristies may touch the surface of the 
roller, and thus remove any adhering bubbles. He prefers a brush 
made with vegetable fibre or spun glass, or other substance not 
liable to be acted upon by the solution. 

mclf Hng Votes. — I . It may be taken as a rule that only a limited 
quantity of nickel can be deposited upon either brass, copper, steel, or 
iron ; if this limited amount of metal be exceeded the deposited metal 
will assuredly separate from the underlying metal. It has also been 
found in practice that a greater thickness of nickel can be deposited 
upon brass and copper without spontaneously peeling off than upon 
steel or iron. Since nickel, however, is an exceedingly hard metal, 
and will bear a considerable amount of friction, a very thin coating 
indeed is all that is necessary for most of the articles to which nickel- 
plating is applied. We may, however, state that too much advantage 
has been taken of this fact, for many articles of American and conti- 
nental manufacture enter the market upon which a mere film of nickel 
has been deposited, and consequentiy they soon become unsightiy from 
the rapidity with which the flimsy coating vanishes with even moderate 
wear. As a rule, the nickel-platers of this country deposit a very fair, 
and in many instances a very generous, coating of nickel upon their 
work, which has caused the home nickel-plating industry to hold a 
high position both as regards the ^ni»A of tiie work and its durability. 
It will be a thing to be regretted if price-competition should cause 
this useful branch of electro-deposition to become degraded by coating 
well-manufactured articles with a mere skin of nickel ! 

2. Nickeling Steel Articles. — When small steel work, such as purse 
moimts, book-clasps, &c. , have to be nickeled, it is better first to suspend 
larger articles of brass or copper upon one end of the conducting rod, 
and to reserve the other end of the rod for the steel articles, or to sling 
them between the larger pieces of work : when it is not convenient to 
do this, one of the anodes should be slung from the end of the rod 
farthest from the battery, as a cathode, so as to take up a portion of 
the current. When steel articles are placed in the bath they should 
b€K3ome ** struck," as it is tonned — that is, receive a slight coating of 



NICKELTNG NOTES. 33 1 

nickel — ^almost immediatelj after immenion, bnt from that moment 
the depoRition muHt be allowed to progfress slowly, otherwise the work 
will surely strips and this it will sometimes do even while in the bath : 
we have known steel work peel, when removed from the bath, by 
simply striking' it gently against a hard sabstanoe. It is also of much 
importance that steel work should be placed in the bath directly after 
it has been passed through the hydrochloric acid pickle and rinsed, 
since even a few moments* exposure to the air — especially if there be 
any acid fumes given off by the batteries — will cause a film of oxide to 
form on the surface and render the deposit liable to strip. 

3. Rinatng the Articles. — It wiU be readily understood that if articles 
are imperfectly rinsed after dipping, the acid or cyanide, as the case 
may be, which may still hang about them must be a source of injury 
to the nickel bath. It is therefore advisable not to depend upon one 
rinsing water only, but to give the work a second rinsing in perfectly 
clean water. It is very commonly the practice to give the final rinsing 
in one division of the scouring tray, the water of which can be readily 
changed by simply removing the plug and turning on the tap when 
it is replaced. 

4. Lime tmed in Finishing Niekel-plated Work. — The lime used for 
finishing work which has been nickel-plated is generally obtained from 
Sheffield, and since this substance becomes absolutely useless after it 
has been exposed to the air — ^by which it attracts carbonic acid and 
falls to an impalpable powder possessing littie or no polishing 
effect upon nickel — it must be preserved in air-tight vessels. For 
this purpose olive jars, or large tin canisters such as are used by 
grocers, answer well. Small quantities may be preserved in stone 
jars, covered with a well-fitting bung. The general practice is to 
take a lump of lime from the jar, cover the vessel immediately, and 
after breaking off a sufficient supply from the selected lump, to return 
it to the jar, which is again securely covered. The fragments of lime 
are thoTi powdered in a mortar, and after sifting through a fine sieve 
or muslin bag, the powder is handed to the finisher, who informs the 
assistant (gfenerally a boy) a short time before he requires a fresh 
supply of the powdered lime. By this arrangement the lime then 
always gets into the hand of the finisher in good condition for his 
purpose. 

5. Niekelittff Dental Work. — One of the most successful purposes to 
which nickeling has been applied for many years, is in coating den- 
tist*8 tools, including forceps, excavators, and other implements used 
in dental practice. These articles, which are made from fine steel, 
are usually sent by the makers to the nickel-plater in a highly- 
finished condition, and therefore require but a moderate amount of 
labour in the plating and polishing shops to turn them out of hand. 



332 ELECTRO-DEPOSITIOM OF MICKBL. 

To prepare this class of work for the bath, the pieces axe first wired, 
after which they are suspended in the potash bath for a short time, or 
until required to be scoured. They are now removed, a few at a time, 
and rinsed, after which they are taken to the scouring bench, where 
they are brushed over with pumice and water ; each piece, after 
rinsing, is dipped for a moment in the hydrochloric acid dip, again 
rinsed, and immediately suspended in the vat. To prevent these 
small pieces from receiving the deposit too quickly and thus becoming 
** burnt " they are usually suspended between articles of a larger size 
which are already in the bath. When battery power is used for coat- 
ing articles of this class (with larger work), from two to three hours* 
immersion in the bath will be required to obtain a fair coating ; with 
a dynamo about half that period will be sufficient. Dental forceps 
require a somewhat longer immersion than the smaller tools. When 
the work is sufficiently nickeled, it is removed from the bath, rinsed 
in hot water, and sent into the polishing room to be lime-finished, 
after which it should be thoroughly well brushed to remove the lime, 
especially from the interstices. Some packers, or warehousemen, are 
apt to be rather careless in this respect, and are satisfied with giving 
nickel-plated and finished work a slight rub up with a leather, so that 
when the articles are received by the customer, the first thing that 
attracts his attention, when unpacking the work, is the appearance of 
a quantity of dirty lime which has fallen from the goods after they 
were wrapped in paper. This negligence has often been the cause of 
complaint, and since it can be so readily avoided by a little extra care, 
this should always be impressed upon the packer of finished work. 

6. lUcorery of Nickel from Old Solutions. — This is most readily 
effected by following Mr. Unwin's ingenious method of preparing the 
double salts of nickel and ammonia, namely, by taking advantage of 
the insolubility of the double sulphate of nickel and ammonia in con- 
centrated solutions of the sulphate of ammonia. To throw down the 
double salts from an old solution, or from one which fails to yield a 
good deposit, prepare a saturated solution of sulphate of ammonia, and 
add this, with constant stirring, to the nickel solution, when, after a 
little while, a granular deposit of a green colour will form, which will 
increase in bulk upon fresh additions of the sulphate being given. 
The effect is not inmiediate, on adding the sidphate of ammonia solu- 
tion, but after a time the green deposit will begin to show itself, and 
when a sufficient quantity of the ammonia salt has been added, the 
supernatant liquor will become colourless, when the operation is com- 
plete. The additions of sulphate of ammonia should be gradually 
made, and the mixture allowed to rest occasionally, after well stirring, 
to ascertain if the green colour of the nickel solution has disappeared. 
The clear liquor is to be poured off the granular deposit — which is 



NICKELING NOTES. 333 

pure double sulphate of nickel and ammonia— and this should be 
allowed to drain thoroughly. It may afterwards be dissolved in water 
and used as a nickel-plating bath. The solution of sulphate of 
ammonia may bo evaporated, and the salt allowed to crystallise ; and 
if the crystals are afterwards re-dissolved and again crystallised, the 
resulting product will be sufficiently pure for future use. 

7. ** Doctoring. ^^ — This term is applied to a system of patching up 
an article which has been " cut through," or rendered bare, in the pro- 
cess of lime- finishing, and it is adopted to avoid the necessity of 
re-nickeling the whole article, which would often entail considerable 
loss to the plater. When the faulty article is sent back from the 
polishing room the first thing to do is to arrange the *' doctor,*' which 
is performed as follows : — ^A pieoe of stout copper wire is bent in the 
form of a hook at each end ; a piece of plate nickel, about one and a 
half inch square (or a fragment of nickel anode) is now bound firmly 
to one of the hooks with a piece of twine ; the lump of nickel is then 
wrapped in several folds of calico, or a single fold of chamois-leather. 
The second hook is now to be connected by a wire to the anode rod of the 
bath, and the article put in contact with the negative electrode. The 
rag end is now to be dipped in the nickel bath, applied to the defec- 
tive spot (which should be first lightly scoured with pumice and water) 
and allowed to rest upon it for a few moments, then dipped again and 
reapplied. By repeatedly dipping the rag in the nickel bath and 
applying it in this way a sufficient coating of nickel may be given in 
a few minutes to enable the finisher to apply the '^ dolly ** to the re- 
nickeled spot, and thus render it as bright as the rest of the article. 
When the operation is skilfully performed, both by the plater and 
finisher, no trace of the patch will be observable. 

8. Common Salt in Xickel Solutions. — Owing to the inferior conductivity 
of nickel baths, various attempts had been made to improve the con- 
ducting power of these solutions by the addition of other substances, 
but the most successful of these, of French origin, was the introduc- 
tion of chloride of sodium (common salt), which is a very good con- 
ductor of electricity. The addition of this substance was subsequently 
adopted by a well-known London firm, the character of whose nickel - 
plated work was much admired for its whiteness as compared with 
some other specimens, of a more or less yellow tone, which appeared 
in the market at that time. The advantages to be derived from the 
addition of common salt to nickel solutions have been very clearly 
demonstrated by M. Desmur, who, in a communication to the author, 
in June, 1880, made the following interesting statement,* which he 

* Electro- Metallurgy, Practically 'i'reated. By Alexander Watt Eighth 
edition, p. 229. 



334 ELBOTBO-DEPOSITION OF NICKEL. 

deems it adyiaable to reproduce in this place from its importance to 
those who follow the nickel-plating industry : — 

9. Attffmentation of the Conductivity of Nickel Bathe — M. Desmur 
says : ** The resistance of nickel baths as they are usually prepared, 
i.e. by dissolving double sulphate of nickel and ammonia in water, 
is yery great. I would advise persons engaged in the trade to intro- 
duce into their baths ten per cent, of chloride of sodium (common salt). 
I have observed, by means of a rheostat, that the addition of this salt 
augments the conductivity by thirty per cent., and that the deposit is 
much whiter and obtained under better conditions. The diminution 
of resistance is in proportion to the quantity of chloride of sodium 
added, for the conducting power of a solution of this salt increases 
with its degree of concentration up to the point of saturation. I 
mention this fact because it is not the case with all saline solutions. 
For example, saturated solutions of nitrate of copper, or sulphate of 
zinc, have the same conductive power as more diluted solutions, be- 
cause the conductibility of these solutions increases as the degree of 
(concentration reaches its maiimnm, and diminishes as the concen- 
tration increases.'* 

In our own experience we have observed that not only is the nickel 
deposit rendered much whiter by the addition of chloride of sodium, 
but it is also tougher and more reguline ; indeed, we have known a 
stout deposit of nickel upon sheet brass or copper to allow the metal 
to be bent from its comers and flattened without the least evidence of 
separation or even cracking — a condition of deposit not often obtained 
in plain double sulphate solutions. 

10. Nickeling Small Articlee by Dynafno-electrieity. — Small steel pieces, 
such as railway keys, for example, should not be kept in the bath 
longer than an hour, or an hour and a half at the most. About twice 
this period will be necessary when battery power is employed. Brass 
and copper work, as a rule, may remain in the bath about double the 
length of time required for steel work. 

11. Nickeling Small Screws — When a large number of small screwn 
have to be nickeled, they may be placed in a brass wire-gauze basket, 
made by turning up a square piece of wire-gauze in the form of a tray, 
and overlapping the comers, which must then be hammered flat and 
made secure by soldering. A piece of stout copper wire, bent in the form 
of a bow and flattened at each end, is then to be soldered to the centre 
of each side of the tray, forming a handle, by which it may be sus- 
pended in the bath by the negative wire of the battery or other source 
of electric power. The screws, having been properly cleaned, are 
placed in the basket, which is then immersed in the bath, and while 
deposition is taking place the basket must be gentiy shaken occa- 
sionally to allow the parts in contact to become coated : this is espe- 



NICKELING NOTES. 335 

oiaUy necessary during the first few moments after immersion. When 
nickeling such articles in the wire basket, they should be placed in a 
single layer, and not piled up one above another, since nickel has a 
strong objection to deposit round the eoitter. It is better, however, to 
sling screws by thin copper wire than to use a basket ; and though 
the operation is a rather tedious one, a smart lad can generally " wire " 
screws, after a little practice, with sufficient speed for ordinary de- 
mands. The simple method of wiring screws before described will be 
found very useful, and if the necessary twist is firmly given there need 
be no fear of the screws shifting ; the wire used for this purpose 
should never be used a second time without stripping the nickel from 
its surface and passing it through a clear fire to anneal it. When 
nickeling screws, it is beet to sling them between other work of a 
larger size, otherwise they are liable to become burnt, which will 
necessitate stripping ofF the deposited nickel or facing them upon an 
emery wheel. 

1 2 . Dead Nickel-plating . — Certain classes of work, as ship deck lamps, 
kilting machines, and various oast-iron articles, are generally required 
to be left dead — that is, just as they come out of the nickel bath. All 
such work, when removed from the bath,* should be at once rinsed 
in very hot and perfectly clean water. Care should be taken not to 
allow the work to be touched by the fingers at any part that catches 
the eye, since this handling invariably leaves an unsightly stain. 
Cast-iron work, when properly nickel-plated, presents a very pleasing 
appearance, which should not be marred by finger*markfl before it 
reaches the hands of the customer. 

13. "Dry" Nickel'plaiing . — This method, which is of American 
origin, has sometimes been adopted in this country for umbrella mounts 
and other small work, but it is only applicable to very cheap work, 
upon which the quantity of nickel is of secondary importance. Work of 
this character is generally dollied with a ** composition " consisting of 
crocus (oxide of iron) mixed up into the form of a hard solid mass with 
tallow. The workman takes a lump of the composition, which he 
presses against the revolving dolly until it has acquired a small 
amount of the composition upon its folds (as in Ume-finishing). He 
now holds the piece of work to the dolly, which quickly becomes 
brightened. When a sufficient number of pieces have been prepared 
in this way, they are suspended by any suitable means and at once 
placed in the bath, and so soon as they have become sufficiently coated 
for this class of work, that is in about half -an-hour or so, the articles 
are removed, rinsed, and dried, and after a slight dollying are ready for 
market. A convenient arrangement for suspending umbrella mounts, 
and articles of a like description, is shown in Fig. 1 16. 

14. Retnoving Nickel from SuMpcndiiig Jpplianeet. — When wire- 



33^ 



ELECTRO- DEPOSITION OF NICKEL. 



gtkVLze trays, wire suspenders, and other contrivanoes by which articles 
have been supported in the bath have been used many times, they 



f-^ 



^s 



>< 



>< 



ES 



Fig. ii6. 

naturally become thickly coated with nickel, and since this metal 
when deposited upon itself has no adhesion, the various layers of 

nickel which the tray, &c., have received from time 
to time generally curl up and break off with the 
slightest touch, and the fragments are liable not only 
to fall into the bath, but upon any work which may be 
in the solution at the time. It is better, therefore, to 
remove the nickel from these appliances, either by 
means of a stripping solution or by connecting them 
to the positive electrode of a battery and dissolving 
the metal off by electrolysis, for which purpose a 
small bath may be specially kept. 

15. Beeovery of Dropped Articles from the Bath. — 
When an article is accidentally dropped into the 
nickel vat, the workman should have at hand a 
ready means of recovering it without resorting to the 
unhealthy practice of plunging his bare arm into the 
solution. Many contrivances have been adopted for 
this purpose, amongst which may be mentioned an instrument of 
which a sketch is shown in Fig. 117. This simply consists of a per- 




Fig. 117. 



NICSELINO NOTES. 337 

forated iron plate, fitted with a suitable handle, which may be oon- 
yeniently attached by means of a socket brazed on to the perforated 
plate. If this tool, or /t/V, be gently lowered into the bath, in the 
direction in which the article is supposed to lie, and carefully moved 
about, 80 as not to disturb the sediment more than can be avoided, 
the lost article will probably soon come in contact with the lift, which 
should then be guided so as to draw the article to the side or end of 
the bath, when it may be shovelled on to the perforated plate and 
gradually lifted to the surface of the bath and taken off the plate, 
and the instrument hung up in its proper place ready for use another 
time. When small steel or iron articles fall into the bath, they may 
be recovered by means of a horse-shoe magnet. For this purpose 
a tolerably large magnet, having a cord attached to its centre and 
allowing the poles to hang downward, may be employed, and if 
allowed to drag along the bottom of the vat slowly, so as to avoid 
disturbing the sediment as much as possible, the lost article may 
gfenerally be recovered and brought to the surface, even when the 
bath is full of work, without stirring up the sediment to any serious 
extent. When the recovery of the dropped pieces is not of any 
immediate consequence, this is better left till the evening, after the 
last batch of work has been removed. 

16. tolled Nickel Anodes. — The cost of a nickel-plating outfit, when 
e(ut anodes are employed, is in this item alone excessively heavy, since 
in many cases such anodes, for large operations, frequently weigh more 
than a quarter of a hundredweight each ; and when it is borne in mind 
that for a 250-gfallon bath from sixteen to twenty-four anodes would 
be required — except when a dynamo or magneto-electric machine is 
employed, when about half that number would be sufficient — it will 
be at once seen that the agg^gate weight of metal would be consider- 
able. Since rolled nickel anodes can now be obtained of almost any 
required thinness, from one-fourth to one-eighth of the quantity of 
metal only would be required to that of the cast metal. It is a 
common fault with cast nickel anodes that after they have been in 
use a short time they become soft and flabby while in the depositing 
vat, and will even fall to pieces with the slightest handling and become 
deposited — ^not in the electrolytic sense — at the bottom of the vat. It 
is not an uncommon circumstance, moreover, to find a considerable per- 
centage of loose carbon — graphite — interspersed with the badly-cast 
nickel, and which, of course, if paid for as nickel, entails a loss upon 
the consumer. We have seen samples of such anodes containing 
nearly thirty per cent, of graphite, which could easily be scooped out 
with a teaspoon ! Some very good specimens of cast nickel, however, 
enter the market in which neither of the above faults are to be found ; 
indeed, we have examined samples containing 99 per cent, of nickel, 

Z 



^^S ELECTRO-DEPOSITION OF NICKEL. 

which for all practicAl purposes may be said to be pure. We should, 
in any case, give our preference to roNed nickel anodes ; and for the 
following reasons : — They are less costly ; they become more uniformly 
dissolved in the bath ; they are generally more pure ; they do not 
soften in the solution, and are less cumbersome to handle itum cast 
anodes, which is an advantage when these require to be shifted, as in 
plating mullers and other larg^ pieces. 

17. Xxekeling Cast B rasa Work. — It sometimes occurs that work of 
this description is full of sand-holes ; when such is the case, the 
polisher should receive instructions to obliterate these as far as 
possible, for nothing looks more unsightly in nickel-plated and 
finished articles than these objectionable cavities. It not unfre* 
quently happens, however, that some sand-holes are too deep to be 
erased by the polishing process, with any amoimt of labour, while 
sometimes, in his endeavour to obliterate these defects the polisher 
finds that they extend in magnitude, and are found to enter deep into 
the body of the work. In such cases all attempts to eradicate them 
will be futile, and must therefore be abandoned. Polishers and 
finishers accustomed to prepare work for nickel-plating are fully aware 
of the importance of a fair face on the work, and they generally do 
their best to meet the requirements of the nickeling process, and 
many of them are exceedingly careful to prepare the work so that, 
when nickeled and finished, it shall look creditable 



CHAPTER XXI. 

DEPOSITION AND ELECTRO-DEPOSITION OF TIN. 

Deposition by Simple Immeraion. — Tinning Iron Articleii by Simple Immer- 
sion.— Tinning Zinc by Simple Immersion. — Tinning by Contact with 
Zinc. — RoseleuHs Tinning Solutions. — Deposition of Tin by Single Celt 
I'rocess.— Dr. Hillier's Method of Tinning Metals.— Heeren's Method of 
Tinning Iron Wire.— Electro-deposition of Tin. — Roseleur's Solutions. — 
Fearn's Process. — Steele's Process. — Electro-tinning Sheet Iron. — 
Spence's Process.— Recover}^ of Tin from Tin Scrap by Electrolysis. 

Thebe are three different methods of coating brass and other metals 
with tin in what is termed the wet tcat/y in contradistinction to the 
ordinary method of tinning by immersion in a bath of molten metal. 
By two of these methods a beautifully white film of tin is deposited, 
but not of sufficient thickness to be of a durable character. By the 
third method, a deposit of any required thickness may be obtained, 
although not with the same degree of facility as is the case with gold, 
silver, and copper. 

XMpodtioii by Btmpto Tmimirrion, or "Dippliii;." — For this pur- 
pose, a saturated solution of cream of tartar is made with boiling 
water : in this solution small brass or copper articles, such as brass 
pins, for example, are placed between sheets of grain tin, and the 
liquid is boiled until the desired result is obtained — a beautifully white 
coating of tin upon the brass or copper surfaces. Ordinary brass pins 
are coated in this way. Some persons add a little chloride of tin to 
the bath to facilitate the whitening , as it is termed. The articles are 
afterwards washed in clean water, and brightened by being shaken in 
a leathern bag with bran, or revolved in a barrel. 

Tinning Iron Articles by Slmplo Xmmerslon.— A solution is 
first made by dissolving, with the aid of heat, in an enamelled pan — 

Protochloride of tin (fused) ... 2} grammes. 

Ammonia alum 75 v 

Water 5 litres.* 



^ Tables of French weights and measures are given at the end of the 
volume. 



340 DEPOSITION AND ELBOTBO-DEPOSITION OF TIN. 

The chloride of tin (which may be obtained at the dryBalters) is 
readily made by dissolving grain tin in hydrochloric acid, wiUi the aid of 
heat, care being taken to have an excess of the metal in the dissolving 
flask. When tiie bubbles of hydrogfen g^ which are evolved cease to 
be given off the action is complete. If the solution be evaporated at 
a gentle heat until a pellicle forms on the surface, and the vessel then 
set aside to cool, needle-like crystals are obtained, which may be 
separated from the *' mother liquor*' by tilting the evaporating 
dish over a second vessel of the same kind. When all the liquor has 
thoroughly drained, it should in its turn be ag^in evaporated, when a 
fresh crop of crystals will be obtained. The crystals should, before 
weighing, be gently dried over a sand bath. 

The ammonia alum is an article of commerce, and is composed of 
ammonia, 3*75 ; alumina, 11*34; sulphuric acid, 35*29; and water, 
49*62, in 100 parts. It may be prepared by adding crude sulphate of 
anunonia to a solution of sulphate of alumina. 

When the solution of tin and alum has been brought to a boil, the 
iron articles, after being well cleaned and rinsed in water, are to be 
immersed in the liquid, when they quickly become coated with a deli- 
cately white film of a dead or matted appearance, which may be 
rendered bright by means of bran in a revolving cask, or in a leathern 
bag shaken by two persons, each holding one end of the bag. The 
scratch-brush is also much used for this purpose. To keep up the 
streng^ of the tinning or whitening bath small quantities of the fused 
chloride of tin are added from time to time. Articles which are to 
receive a more substantial coating of tin by the separate battery may 
have a preliminary coating of tin in this way. 

Tinning Zinc \fj Btmplo Tmnn<wlon. — To make a bath for 
tinning zinc by the dipping method, the ordinary alums of commerce 
(potash and soda alums) may be used. In other respects, the solution 
is prepared and used in the same way as the above ; and it may be 
stated that the proportions of the tin salt and ammonia in water need 
not of necessity be very exact, since the solution, after once being used, 
becomes constantly weakened in its proportion of metal, still giving* 
very g^ood results, though somewhat slower than at first. 

For coating articles made of brass, copper, or bronze, a boiling solu- 
tion of ][>eroxide of tin in caustic potash makes a very good bath, 
yielding a coating of extreme whiteness. A still more simple solution 
may be made by boiling grain tin, which should first be granulated, in 
a moderately strong solution of caustic potash, which in time will 
dissolve sufficient tin to form a very good whitening solution. 

Tlniiliis \gj Contact witli Zinc. — Deposits of tin upon brass, 
copper, iron, or steel may easily be obtained from either of the fol- 
lowing solutions by placing the articles, while in the hot tinning 



BOSELEUB's tinning solutions. 341 

bath, in contact with fragments of clean zinc, or with granulated zino. 
To granulate ziac, tin, or other metals, have at hand a deep jar, or 
wooden bucket, nearly filled with cold water, upon the surface of 
which spread a few pieces of chopped straw or twigs of birch. When 
the metal is melted, let an assistant stir the water briskly in one direction 
onhj^ then, holding the ladle or crucible containing the molten metal 
high up above the moving water, pour out gradually^ shifting the 
position of the ladle somewhat, so that the metal may not all flow 
down upon the same part of the vesseFs bottom. When all the metal 
is poured out, the water is to be run off, and the granulated metal 
collected and dried. It should then be put into a wide-mouthed bottle 
or covered jar until required for use. 

H owft A mar'm Tf lining' Bolvtlona. — ^Boseleur recommends either of 
the two following solutions for tinning by contact with zinc : I . Equal 
weights of distilled water, chloride of tin, and cream of tartar are 
taken. The tin salt is dissolved in one-third of the cold water ; the 
remaining quantity of water is then to be heated, and the cream of 
tartar dissolved in it ; the two solutions are now to be mixed and well 
stirred'. The mixture is dear, and has an acid reaction. 2. Six parts 
of crystals of chloride of tin, or 4 parts of the fused salt, and 60 parts 
of pyrophosphate of potassium or sodium are dissolved in 3,000 parts 
of distilled water, the mixture being well stirred ; this also forms a 
clear solution. Both the above solutions are to be used hot, and kept 
constantly in motion. The articles to be tinned are immersed in 
contact with fragments of zinc, the entire surface of which should be 
equal to about one-thirtieth of that of the articles treated. In from 
one to three hours the required deposit is obtained. To keep up the 
strength of the bath equal weights of fused chloride of tin and pyro- 
phosphate are added from time to time. Boseleur gives the preference 
to this latter solution if the pyrophosphate is of good quality. He 
also prefers to use coils of zinc instead of fragments of the metal, as 
being less liable to cause markings on the articles than the latter, which 
expose a greater number of points. It is evident from this that 
granulated zinc shoidd not be used with these solutions, since metal 
in this form would exhibit an infinite number of points for contact. 
For tinning small articles, such as nails, pins, &c., these are placed 
in layers upon perforated zinc plates or trays, which allow of the 
circulation of the liquid ; the edges of the plates are turned up to keep 
the articles from faUing off the zinc surfaces. These plates are placed 
upon numbered supports, in order that they may be removed from the 
bath in the inverse order in which they were immersed. The plates 
are scraped clean each time before being used, in order that a perfect 
metallic contact may be insured between the plates and the articles to 
be tinned. During the tinning the small articles are occasionally 



342 DEPOSITION AND ELEOTRO-DE POSITION OF TIN. 

stirred with a three-pronged iron fork, to ohange the points of contact. 
After the articles have been in the bath from one to three hours an 
addition of equal parts of pjxophosphate and fused chloride ia made, 
and the articles are then subjected to a second immersion for at least 
two hours, by which they receive a good deposit. Larg^ articles (as 
culinary utensilB, &c.} coated in the above solution are scratch- 
brushed after the first and second immersions. The final operations 
consist in rinsing the articles, and then drying them in warm sawdust 
In reference to the working of the above solutions, Roseleur says : — 
'* If we find that the tin deposit is grey and dull, although abundant, 
we prepare [? strengthen] once or twice with the acid orystaUised 
protochloride of tin. With a very white deposit, but blistered, and 
without adherence or thickness, we replace the acid salt, by the fused 
one. In this latter case we may also diminish the proportion of tin 
salt, and increase that of the pyrophosphate." For tinning zinc in a 
pyrophosphate bath, the following proportions are recommended : — 

Protochloride of tin (fused) . . i kilogramme. 
Pyrophosphate of soda ... 5 Icilogrammes. 
Distilled water .... 300 litres. 



Deposition of Tin by BingU CMll Frooew. — ^WeH makes a tinning 
solution by dissolving a salt of tin in a strong solution of caustic 
potash or soda ; a porous cell nearly filled with the caustic alkali (with- 
out the tin salt), and in this metallic zinc, with a conducting wire 
attached, is placed, the end of the wire being put in contact with the 
articles to be tinned. The solution of zinc formed in the porous cell 
during the action is revived by precipitating the zinc with sulphide of 
sodium. 

Dr. HilHOT^g Bi«tliod Off Tinning Metals. — A solution is pre- 
pared with I part chloride of tin dissolved in 20 parts of water ; to 
thin in added a solution composed of 2 parts caustic soda and 20 parte 
of w^ater ; the mixture being afterwards heated. The articles to be 
tinned are placed upon a perforated plate of block tin and kept in a 
state of agitation, with a rod of zinc, until they are sufficientiy coated. 

Be«ren's M«tbod off Tinning Dron Wire. — ^This consists in first 
cleaning the wire in a hydrochloric acid bath in which a piece of zino 
is suspended. The wire thus cleaned is then put in contact with a 
plate of zinc in a bath composed as follows : — 

Tartaric acid 2 parts. 

Water 100 „ 

To this is added, 3 parts of each, chloride of tin and soda. After 
remaining in the above bath about two hours, the wire is brightened 
by drawing it through a hole in a steel plate. 



sisoTBO-rEPOBinoN OF TIN, 343 

\ of na. — Although the depoHUtun of tin b; 
Biiii| le dipping, or by oonblct with zino, is exceedingly useful for 
small articles, and maj be pursaed bj persona totally ignoTant of 
aleobo-depoaition, the deposition of this metal by the direct ottirent 
is far mora reliable when deposits of considerable thickness are desired, 
besideB being applioable to aiticleB of large dimensionB. There have 
been many diSereot processes recommended— some of whioh have 
been patented — for the electro-depoaition of this metal, and serenil of 
theee have been worked upon a tolerably extensive scale. ITor many 
pnrposes, this exceedingly pretty metal, when properly deposited by 
alectrDlyiUB, is very useful, but more eepeciaUy for coating die inndea 
of cast-iron culinary veeaela, oopper preserving pans, and artiales o( a 
Himilar doeoription. Thereisone drawbaekoonaeoted with the eleotn- 
deposition of this metal, however, whioh stands much in the way of 
its practioal usefulneas, and renders its deposition by separate current 
more costly &an would otherwise be the case, namely, that Qie anodes 
do not become diaaolved in the bath in the same ratio as the depout 
upon the cathode, oonsequentiy the stiength of the bath requires to 
be kept up by constant additionH of some salt of the metal to the solu- 
tion while deposition is t&Ung place. If this were not done, the bath 
would soon become exhausted, and cease to work altogether. To over- 
come Utifl difficulty, and to 
keep up a uniform oundition 
of the bath, the author pro- 
posed in his former work • the 
following method :^ARsage 
above the depositiiig tank a 
stone vessel, capable of receiv- 
ing a lap (Fig. i iS) ; to this 
connect a vulcanised india- 
rubber tube, reaching nearly 
to the surface of the solution. 
Let this jar be nearly flUed 
with oonoentrated solution of 
the tan salt employed, made 

by dissolving the salt in a por- fig. iiS. 

tion of the main solution. 

'When the bath is being worked, let the tap be turned slighUy, ■□ 
that the concentrated solution may drip or flow into the depositing 
bath. When the stone vessel has become empty, or nearly w, a fresh 
oonctmtaated solution should be made, using the liquor from tho bath 
to a certain extent in lieu of wat^-, so a^ not to increase the bulk of 

* ** Slectro-Malallutgy." Eighth edition, p. 241. 



344 REPOSITION AND ELECTRO -DEPOSITICTK OF TIN. 

the bath more than is absolutely necessary. By this method several 
advantages are grained — (i) By using the weakened bath each time 
to make the concentrated solution, there will be but trifling addi- 
tion to the bulk of the solution ; (2) By allowing the concentrated 
solution to coniinualiy enter the bath while deposition is taking place, 
there will be no necessity to disturb the bath by stirring in a larger 
quantity of the solution all at one time. In cases in which it is 
necessary to make additions of two separate substances, these may 
be introduced by employing two tapped vessels instead of one. 

RoseleurU Solution. — The bath which this author recommends as 
possessing all the conditions desired by the operator, is composed 
of:— 

Protochloride of tin (in crystaU) . 600 grammes. 

Pyrophosphate of soda or potassa 5 kilogrammes. 

Distilled or raiu water .... 500 litres. 

Instead of employing crystals of the tin salt, the fused substance is 
to be preferred, 500 grammes of which take the place of the former. 
In making up the bath, the water is put into a tank lined with anodes 
of sheet tin, imited together, and put in connection with the positive 
electrode of the battery or other source of electricity. The pyro- 
phosphate salt is then put into the tank, and the liquid stirred until 
this is dissolved. The protochloride is placed in a copper sieve, and this 
half immersed in the solution. A milky- white precipitate is at once 
formed, which becomes dissolved by agitation. When the liquid has 
become clear and colourless, or slightly yellow, the bath is ready for 
use. The cleaned articles are now to be suspended from the negative 
conducting rods as usual. 

** The anodes," says Boseleur, ** are not sufficient to keep the bath 
saturated ; and when the deposit takes place slowly, we add small por- 
tions of equal weights of tin salt and pyrophosphate. The solution of 
these salts should always be made with the aid of the sieve, for if 
fragments of the protochloride of tin were to fall on the bottom of the 
batli they would become covered with a slowly soluble crust, pre- 
venting their solution." It is stated that any metal may be coated in 
this solution with equal facility, and that a good protective coating 
may be obtained with it, while the metal has a dead white lustre 
resembling that of silver, which may be rendered bright either by 
scratch -brushing or by burnishing. An intense current is necessary 
in working this solution. 

Fearn'ii Process. — ^This process, for which a patent was granted in 
1873, includes four different solutions, which may be thus briefly 
described : No. i . A solution of chloride of tin (containing but little 
free acid) is first prepared, containing 3 ounces of mfft*^!!'^ tin per 



8TEELE*S PROCESS. 345 

gallon; 30 pounds of caustic potash are dissolved in 20 gallons of 
water ; 30 pounds of cyanide of potassium in 20 gallons of water ; and 
30 pounds of pTTophospbate of soda in 60 gallons of water. 200 ounces 
(by measure) of the tin solution are poured slowly, stirring with a 
glass rod, into the 20 gallons of potash solution, when a precipitate is 
formed, which quickly redissolves ; into this solution is poured first 
all the cyanide solution, then all the pyrophosphate, and the mixture 
well stirred. Ko. 2. 56 pounds of sal-ammoniac are dissolved in 
60 gallons of water ; 20 pounds of pyrophosphate of soda in 40 gallons 
of water ; into the latter is poured 100 ounces by measure of the 
chloride of tin solution, and the mixture well stirred, when the pre- 
cipitate formed redissolves as before. Lastly, the sal-ammoniac solu- 
tion is added, and the whole well stirred together. No. 3. 150 pounds 
of sal-ammoniac are dissolved in 100 gallons of water ; into this 
200 ounces by measure of the tin solution are poured, and weU stirred 
in. No. 4. To make this solution, 400 ounces of tartrate of potash 
are dissolved in 50 gallons of water; 1,200 ounces of solid caustic 
potash in 50 gallons of water ; 600 ounces by measure of the tin solu- 
tion are then added slowly, with stirring, to the tartrate solution ; the 
caustic potash solution is next added, the stirring being kept up until 
the precipitate which forms has become entirely redissolved. 

In using the above solutions. No. i is to be worked at a temperature 
of 70° Fahr., with a current from two Bunsen batteries; No. 2 is 
used at from lOo'* to 1 10° Fahr., with a weaker current ; No. 3 is to 
be worked at 70° Fahr. ; and No. 4 may be used cold. It is stated 
that solutions i and 4 yield thick deposits without requiring alternate 
deposition and scratch-brushing. Since during the working less tin 
is dissolved from the anodes than is deposited, the oxide or other salt 
of the metal must be added from time to time, except in the case of 
No. 3, which acts upon the anode more freely than the others. In 
tinning cast iron in these solutions, they require first to have a deposit 
of copper put upon them. For tinning zinc articles, No. i solution is 
employed. 

Steele* » Process. — ^This process is applied to coating articles of 
copper, brass, steel, iron, and zinc with tin. The solution is prepared 
thus: Dissohre 60 pounds of common soda, 15 pounds of pearlash, 
5 pounds of caustic potash, and 2 ounces of cyanide of potassium in 
75 gallons of water, then filter the solution ; next add 2 ounces of 
acetate of zinc, 16 pounds of peroxide of tin, and stir the mixture 
until all is dissolved, when the solution is ready for use. The solution 
is to be worked at about 75° Fahr. 

In preparing articles for electro-tinning, they must be rendered per- 
fectly clean, either by scouring or dipping. Articles of cast iron may 
advantageously be first coppered in an alkaline coppering bath. Some- 



346 DEPOSITION AND ELECTRO-DEPOSITION OF TIN. 

times a deposit of tin is giyen in a boiling-hot solution by the adnc- 
contact method, and a stouter deposit afterwards obtained by the 
separate current in either of the foregoing solutions. The process of 
electro -tinning has been much adopted in Franoe, and during the past 
few years there has been considerable attention paid to it in this 
country. It has yet to be developed into a really extensive industry. 

Bleetro-Tlnning 81i««t-Xroii. — 8p«ne«'B Proc— . — ^This inventor 
says :— *' When it is desired to make tin plates as cheaply as possible, 
I first place the plates in a solution of zinc, and deposit that metal 
on the surface ; and then put them in a solution of tin, and deposit a 
coating of that metal. In manufacturing these plates, I coat the 
sheet iron with zinc, as before, and then deposit a coating of lead by 
electricity." By this method he reduces the quantity of tin usually 
required ; and in regfard to teme plates, he dispenses with the use of 
tin altogether. When removed from the bath, the electro -tinned 
plates are brightened by being placed in a stove heated to a tempera- 
ture slightly above that at which tin melts (442° Fahr.). As the plates 
are taken out of the tinning bath, they are placed in a rack capable of 
containing 24 pieces. These racks, as they are filled, are placed in the 
stove, where they are allowed to remain until the tin melts on the surface. 
The plates are afterwards passed through rollers, with that edge first 
which was at the bottom of the rack. To avoid the employment of 
heat, one or more pairs of polished steel rollers may be used in suc- 
cession, and so adjusted as to bear on the plate with some pressure. 
On removing the plates from the bath, they are passed through the 
roUers, which remove inequalities of the tin surface. To give the 
necessary polish, the plates are then placed on a table, on which is a 
pair of rolls rotating at high speed, and coated with cloth or other 
suitable material. These rolls are so arranged ** as to rotate in the 
reverse direction to the transverse of the plate, and hence the plate has 
to be pushed through them.*' 

S«ooT«ry of Tin from Tin Scrap by Blootrolyrio. — ^Dr. J. H. 
Smith, in a paper read before the Society of Chemical Industry, 
described a method for working up tin scrap which he found to be 
successful. The scrap to be dealt with had, on an average, about 
5 per cent, of tin and there was a supply of some 6 tons a week, for 
which quantity the plant was arrangped. It was designed to convert 
the tin into chloride of tin for dyers* use, the iron scrap being utilised 
as copperas. On the recommendation of Messrs. Siemens and Halske, 
of Berlin, one of their dynamos (C 18), was used. The machine in 
question was stated to give a current ot 240 amperes, with an electro- 
motive force of 15 volts, and an expenditure of 7 -horse power. Eight 
baths were used, made of wood lined with rubber. They were 



BEOOVEBT OF TIN FBQH TIN 80BAP BT ELECTB0LYBI8. 347 

I j metres long, 70 centimetres wide, and i mMre deep. The anodes 
were, of coarse, formed of the tin scrap, which was packed in baskets 
made of wood, and of a size to hold 60 kilos to 70 kilos of the scrap. 
There was an arrangement for constantly agitating these baskets by 
raising and lowering them, thus promoting cironlation of the solution 
and regfularity of action. The cathodes were copper plates i^ milli- 
m^tares thick and 1 20 centimetres long by 95 centimetres broad. There 
were sixteen of these, placed two in each tank, one on each side of 
the basket. The electrolyte used was sulphuric acid, diluted with 
9 volumes of water. The tin precipitated was rather over 2 kilos per 
hour ; it was very pure, easily melted when required, and in a form 
very suitable for solution in acid for preparation of tin salts. Dr. 
Smith having worked his process in a district in G^ermany^'where pro- 
bably tin scrap was obtainable at a low price, was enabled to show 
that a profit could be obtained upon the working. The same results 
might possibly be obtained in Birmingham, London, and other dis- 
tricts where large quantities of sheet tin are used. There have been 
many patents taken out for the electrolytic treatment of tin scrap, but 
the expense of collecting the scrap has always been the chief diiBcolty 
in rendering such procesaes commeroiaUy available. 



* For farther remarks on thia proce^* (which >%iu not cuoductcd in 
Germany, as here sUtttd, but iu Milan), see p. 57b. 



CHAPTEE XXII. 
ELECTRO-DEPOSITION OF IRON AND ZINC. 

Electro-deposition of Iron; Facing Engraved Copper-plates.— Klein's Pro- 
cess for Depositing Iron upon Copper.— Jacob! and Klein's Process. — 
Ammonio-sulphate of Iron Solution.— Boettger's Ferrocyanide Solution. 
— Ammonio-chloride of Iron Solution.— Sulphate of Iron and Chloride 
of Ammonium Solution.— Electro-deposition of Zinc- Zincing Solu- 
tions.— Person and Sire's Solution.— Deposition of Zinc by Simple Im- 
mtrsion. — Hermann's Zino Process. 

Bl«etro-dapoaltlon of Iron. — Facing Engrwed Copper 'plates. — ^The 
extreme hardness of electro-deposited iron as compared with copper 
and type metal has caused the electro -deposition of iron to be 
applied to ihe facing of printers' type and engraved copper-plates, by 
which their durability is greatly augmented. The importance of 
protecting the surface of engraved copper-plates from the necessary 
wear and tear of the printing operations can scarcely be over- 
estimated, and a deposit of iron answers this purpose admirably. 
Another g^reat advantage of the iron or " steel facing," or, as it is 
termed in France, acierage, is that when the deposited metal begins to 
wear ofP, the old coating is readily removed from the surface by means 
of dilute sulphuric acid, and another deposit given in its place in 
a very short time. In this way copper -plates may be preserved 
almost for an indefinite period, while each impression from the plate 
is as sharp and distinct as another even after a vast number of copies 
have been printed from the same plate. This system of facing 
printers' type and engraved copper-plates — ^which was orig^inally sug- 
gested by Boettger — and the plates used for printing bank notes, has 
been much adopted by several large firms, including the eminent firm 
by whom this work was printed. 

Iron may readily be deposited from a solution of its most common 
salt, the protosnlphate, or green copperas, but for this purpose the 
salt should be as pure as possible. A depositing solution maj also be 
prepared by passing a strong current through a large iron anode 
suspended in a tolerably strong solution of sal ammoniao. After the 
electrolytio action has been kept up for an hour or so, a oathode oi 



KLEIN*S PROCESS POR DBPOBITTNO IRON UPON OOPPEB. 349 

dean sheet braaa or oopper ahould be substituted, whioh, if the tola- 
tiun has beoome suflBoientlj impregnated with metal, will at once 
receive a coating of iron, of a good white colour, though not perhaps 
quite so bright as the deposit obtained from a solution of the proto- 
sulphate of iron. An iron-depositing solution may he made in the 
same way by employing a moderately strong solution of eitiier acetate 
of ammonium or acetate of potassium. A mixture of two parts 
sulphate of iron and one of sal ammonaio dissolyed in water may also 
be employed, but the solution should not be too strong, otherwise the 
deposit is apt to be irregpalar, and of an indifferent colour. In 
making up iron baths for the electro-deposition of this metal, it has 
oommonly been the practice to employ somewhat concentrated solutions, 
but the author, in the course of a long series of experiments, found 
that in most cases such a condition was far from being necessary and 
that weaker baths frequentiy yielded better results. 

The author has obtained depoaits of iron from most of its salts, 
including those prepared with the vegetable adds, as the acetate, 
citrate, tartrate of iron, &c., from some of which exceedingly interest- 
ing results were obtained, but possesRing, however, no practical signi- 
ficance. The results of some of the more useful experiments ars 
given in the Appendix. 

SleiB's Pro c— finr depoeitliis firon upon Oopper. — ^This process, 
which from its successful results obtained the recognition and support 
of the Russian Gk)vermnent, is specially applicable to the production 
of electrotypes, as a substitute for those produced from copper, and is 
stated to be eminently successful in bank-note printing. The solution 
is prepared in a very simple way, as follows : — ^A solution of sulphate 
of iron is first made, and to this is added a solution of carbonate of 
ammonia until all the iron is thrown down. The precipitate is then 
to be washed cevcral times, and afterwards dissolved by sulphuric 
add, care being taken not to use an excess of acid. The solution is 
to be used in as concentrated a state as possible. To prevent the iron 
bath from becoming acid by working, a very large iron anode is 
employed — about eight times larger in surface than that of the copper 
cathode to be coated. After working this bath for some time, M. 
Klein found that the deposition became defective, and this he dis- 
covered was due to the presence of acid in the bath, owing to the 
anode not having supplied the solution with its proper equivalent of 
iron to replace that which had been deposited. To overcome this, he 
attached a copper or platinum plate to the anode, by which the two 
plates formed a separate voltaic pair in the liquid, causing the iron 
(the positive metal) to become dissolved, while the battery current was 
not passing through the bath. It is stated that the iron deposited by 
this process is as hard as tempered steel, but very brittle ; it may. 



350 ELECTRO- DEPOSITION OF IBON AND ZINO. 

however, be rendered malleable by annealing', when it may be engrayed 
upon as easily aH Hoft steel. The following process is g^ven for copy- 
ing engraved metal plates in electrotype, and then giving them a 
surface of iron. 

To Copy Engraved Metal Pinies and Face them with Iron. — " If the 
plate be of steel, boil it one hour in caustic potash solution. Brush 
and wash it well. Wipe it dry with a rag, and then with one 
moistened with benzine. Melt six pounds of the best gputta-percha 
very slowly indeed, the gum being previously cut up into very small 
pieces. Add to it three pounds of refined lard, and thoroughly incor- 
porate the mixture. Pour the melted substance upon the centre of the 
plate. Allow it to stand twelve hours, and then take the copy off. 

** Phosphoric Solution. — Dissolve a fragment of phosphorus half -an - 
inch in diameter in one teaspoonful of bisulphide of carbon, add a 
similar measure of pure benzine, three drops of sulphuric ether, and 
half-a-pint of spirit of wine. Wash the mould twice with this solu- 
tion, allowing it to dry each time. 

" Silver Solution. — Dissolve one-sixth of an ounce of nitrate of silver, 
in a mixture of half-a-pint of strong alcohol and half a teaspoonful 
of acetic acid ; wash the mould once with this liquid, and allow it to 
dry. 

** Copper Solution. — ^Dissolve fifty-six pounds of sulphate of copper in 
nineteen gallons of water, and add one gallon of oil of vitriol. De- 
posit a plate of copper upon the mould in this solution. 

** Iron Solution. — ^To coat the copper plate with a surface of iron, 
dissolve fifty-six pounds of carbonate of ammonium in thirty-five 
gallons of water. Dissolve iron into the liquid, by means of a clean 
anode of charcoal iron and a current from a battery. Clean the anode 
frequently, and add one-pound of carbonate of ammonium once a 
week. The copper plate, before receiving the deposit, should be 
cleansed with pure benzine, then with caustic potash, and thoroughly 
with water. Immerse the cathode in the iron solution for four 
minutes, take it out, wash, scrub, replace in the vat, remove and 
brush it every five minutes, until there is a sufficient deposit ; then 
wash it thoroughly, well dry, oil, and rub it, and dean with benzine' 
If it is not to be used at once, coat it with a film of wax.'* 

JaeoM and Ktoln's Vtogmw. — For depositing iron upon moulds for 
reproducing engraved surfaces and for other useful purposes, the fol- 
lowing process is given. A bath is prepared with a solution of sul- 
phate of iron, with the addition of either sulphate of ammonia, 
potash, or soda, which form double salts with the salt of iron. The 
bath must be kept as neutral as possible, though a small quantity of 
a weak organic acid may be added to prevent the precipitation oi 
aalts of peroxide of iron. A small quantity of gelatine improves the 



JlooBi AND Klein's pboges& 351 

texture of the deposit. To accelerate the rapidity of the deposit, and 
favour it8 uniform depositiou, the flolution should be warm. The anodes 
employed are larg^e iron plates, or bundles of iron wire, and since it is 
found that the anodes do not dissolve with sufficient rapidity to keep 
~ up the normal metallic strengfth of the bath, the inventors have found it 
useful to employ anodes of gas carbon, copper, or platinum — or any 
metal which is electro -negative to iron — ^as well as the iron anodes ; 
or these auxiliary anodes may be placed in separate porous cells, 
excited by dilute sulphuric or nitric acid, or the nitrates or sulphates 
of potash or soda. The current employed is either from one or two 
Daniell cells only, or from a single Smee, the size of which is propor- 
tionate to the surface of the cathode. The Daniell celln should have 
a large surface, and the zinc be excited by a solution of sulphate of 
magnesia instead of dilute sulphuric acid. It is said to be " indispen- 
sable that the current should be regulated and kept always uniform 
with the assistance of a galvanometer having but few coils, and there- 
fore oifering only a small resistance. The intensity of the current 
ought to be such as to admit only of a slight evolution of gas bubbles 
at the cathode ; but it would be prejudicial to the beauty of the 
deposit if gas bubbles were allowed to adhere to its surface.** In 
working this process, the same moulds used for electrotyping may be 
employed ; but it is advisable in using lead or gutta-percha moulds 
to first coat them with a film of copper in the usual way, and after 
rinsing to place them at once in the iron solution. The film of copper 
may be afterwards removed, either by mechanical means or by dipping 
in strong nitric acid. 

The following formula is given for the composition of the iron 
bath:— 

Sulphate of iron 139 parts. 

„ magnesia .... 223 „ 

These substances are to be dissolved together in hot water, with the 
addition of a little oxalic acid and some iron shavings. This solution 
should be kept, in its concentrated condition, in well-stoppered glass 
lx)ttles or carboys, and when required for use must be diluted until 
it has a specific g^vity of i * 155 (water being i 'Ooo). When working 
this solution, the oxide of iron which appears at the surface of the 
liquor must be skimmed off, with some of the solution, and shaken 
up in a bottle with a little carbonate of magnesia, and after settling, 
the clear liquor may be returned to the bath. To prevent air-bubbles 
from adhering to the mould, while in the bath, the mould may be 
first washed with alcohol, and afterwards with water ; it is then to be 
placed in the bath before it has time to become dry. It is said that 
the iron deposited by this process is very hard and brittle, therefore 



352 



ELECTRO- DEPOSITION OF IRON AND ZINC. 



much care muBt be taken to avoid breaking the electro -deposit when 
separating* it from the mould. When annealed, however, the iron 
acquires the malleability and softness of tempered steel, and has a 
remarkably fine appearance when brushed with carbonate of mag- 
nesia. 

Amongst the numerous solutions recommended for the electro- 
deposition of iron, we select the following : — 

Anunonlo-siilpliate of Iron 8olatloB. — This double salt, which 
was first proposed by Boettger for depositing this metal, may be readily 
prepared by evaporating and crystallising mixed solutions of equal 
parts .of sulphate of iron and sulphate of ammonia ; a solution of the 
double salt yields a fine white deposit of iron with a moderate current, 
and has been very extensively employed in ** facing " engraved copper- 
plates. When carefully worked, this is one of the best solutions for 
the deposition of iron upon copper surfaces. 

Bo«tt8«r's Pwrocy a ald» Bolntion. — This solution, which is con- 
sidered even better than the former for coating engraved copper-plates 
with iron, is formed by dissolving ro grammes of ferrocyanide of potas- 
sium (yellow prussiate of potash) and 20 grammes of Bochelle salt in 
200 cubic centimetres of distilled water. To this solution is added a 
solution consisting of 3 grammes of persulphate of iron in 50 cubic 
centimetres of water. A solution of caustic soda is next added, drop 
by drop, with constant stirring, to the whole solution, until a per- 
fectly clear light yellowish liquid is obtained, which is then ready for 
immediate use. 

Mr. Walenn obtained good results from a slightly acid solution of 
sulphate of iron (i part to 5 of water). Sulphate of anmionia, how- 
ever, was found to increase the conductivity of the solution. 

A mmrnito-dilcBrlde of Xron Bolntioiiy made by adding sal-ammo- 
niac to a solution of protochloride of iron, may also be used for de- 
positing iron, a moderately strong current being employed. When 
carefully prepared and worked, this solution is capable of yielding 
very good results, but it has these disadvantages : the solution becomes 
turbid, and a shiny deposit is apt to form upon the electrodes. It is 
a common defect in iron solutions that they are liable to undergo 
change by absorbing oxygen from the air. To overcome this, Klein 
adopted the ingenious expedient of adding glycerine to the solution, 
by which he was enabled to keep his solution bath tolerably clear, 
except on the surface, upon which a shiny foam accumulated, which 
became deposited upon the articles in solution. To prevent the air 
from injuriously affecting the baths, it is advisable that tihe depositing 
vessel should be kept covered as far as practicable. 

Snlphata of Zkon and Chloride of Anunoniiun Solntton. — ^The 
addition of chloride of ammonium (sal-ammoniac) to sulphate of iron 



ELECTRO-DEPOSITION OF ZINC. — WATT's SOLUTION. 353 

Bolation improves the character of the deposit while improving the 
oonductivity of the solution. Meidinger found that engraved copper- 
plates coated with iron in a bath Hivlb composed were capable of 
jrielding from 5,000 to 15,000 impressions. * 

lll»etro-d«pocition of Zinc — Watt^t Solution, — ^The deposition of 
this metal has never attained the dignity of a really practical art. In 
the earlier periods of electro-deposition many iron articles, including the 
sheet metal, were coated with zinc by this means, to protect them from 
rust, or oxidation, but it wa« soon found that the porous and granular 
nature of the coating, instead of acting as a preservative from rust, 
greatly aeo$lerated the action of moisture upon the underlying metal 
(iron) by promoting electro-chemical action. 

The process of galoaniting iron, as it is fancifully termed — ^by which 
artidee of this metal are dipped into a bath of molten zinc — soon 
proved, although not wholly &ultless, so superior to that of electro- 
zincing, that it became generally adopted to the entire exclusion of the 
latter. There are many purposes — gauze wire, for example — to which 
the process of ''galvanising" is inapplicable, and for which a good 
elec^-depoeit of zinc would be specially serviceable. To obtain a 
solution which would give a good reguline deposit of zinc suitable 
for such purposes, the author, after a long series of experiments, 
succeeded in forming a solution, for which he obtained a patent 
in 1855, from which he obtained some exceedingly beautiful de- 
posits, possessing the fullest degree of toughness which this metal 
exhibits when in a perfectly pure state. The most satisfactory 
result was obtained by dissolving the best milled zinc in a strong 
solution of cyanide of potassium, with the addition of liquid ammonia, 
by means of a strong voltaic current. The process is briefly as fol- 
lows : 200 ounces of cyanide of potassium are dissolved in 20 gallons 
of water ; to this solution is added 80 ounces, by measure, of strong 
liquid ammonia. The whole are then well stirred together. Several 
large porous cells are then filled with the solution, and these are 
placed upright in the vessel containing the bulk of the solution, the 
liquids in each vessel being at an equal height. Strips of copper are 
then connected by wires to the negative pole of a compound Bunsen 
battery of two or more cells, and these strips are immersed in the 
porous cells. A large anode of good milled zinc, previously well 
deaned, is now connected to the positive pole of the battery, and the 
plate suspended in the larger vessel. The voltaic action is to be 
kept up until the zinc has become dissolved to the extent of about 
60 ounces, or 3 ounces to each g^on of solution. To this solution is 
added 80 ounces of carbonate of potash, by dissolving it in portions of 



For farther remarks on the electro-deposition of iroD, see pp. 442-446. 



354 ELECTRO -DEPOSITION OP IRON AND ZINC. 

the solution at a time, and returning the dissolved salt to the bath. 
The porous cells being' removed, the solution is allowed to rest for 
ilbout twelve hours, when the clear liquor is to be transferred to 
another vessel, the last portions, containing sedimentary matter, being 
filtered into the bath. 

Treparvng Cast and Wrought Iron Work for Zincing. — ^The artioles 
require to be first dipped for a short time in a hot potash bath, after 
which they are to be well rinsed. They are next steeped in a ' ' pickle " 
composed of oil of vitriol half-a-pound, water i g^on. As soon as 
the black coating of oxide yields to the touch the articles are removed 
and plunged into dean cold water ; they are then taken out one by one 
and well brushed over (using a hard brush) with sand and water ; if 
any oxide still remains upon the surface, the articles must be immersed 
in the pickle again, and allowed to remain therein until, when the 
brushing is again applied, they readily become cleaned. They are 
now to be well rinsed, and at once suspended in the zincing bath, in 
which they should remain for a few minutes, then taken out and ex- 
amined ; and if any parts refuse to receive the deposit, these must be 
again well sand-brushed or scoured, the article being finally brushed 
all over, again rinsed, and placed in the depositing bath, where they 
are allowed to remain until sufficientiy coated. An energetic current 
from at least two 3 -gallon Bunsen cells, where a dynamo-machine is 
not used, is necessary to obtain a good deposit. The articles may be 
rendered bright by means of the scratch -brush, but larg^ articles 
may be sufficientiy brightened by means of sand and water, with 
the assistance of soap. When finished they should be dipped into 
hot water, and may then be further dried by means of hot sawdust. 
The anodes should be of the best milled zinc, and well cleaned before 
using. 

Zineins Bolntloiis. — For the electro -deposition of zinc, solutions of 
the sulphate, ammonio- sulphate, chloride, and ammonio-chloride may 
be employed, as also alkaline solutions prepared by dissolving zino 
oxide or carbonate in a solution of cyanide of potassium or caustic 
potassa ; the deposit from either of these alkaline solutions is g^eraUy 
of very good quality, and if too strong a current be not employed, 
the deposited metal is usually very tough. 

F«raon and Bird's Bolntion. — ^This consists of a mixture of 1 part 
of oxide of zinc dissolved in 100 parts of water, in which 10 parts of 
alum have been previously dissolved at the ordinary temperature. The 
current from a single battery cell is employed, and the anode surface 
should be about equal to that of the articles to be coated, when, it is 
stated, the deposition proceeds as easily as that of copper, and takes 
place with equal readiness upon any metal. 

D«po«ltloii of ZlBo by Blmple XmiiMnioii. — According to 



DEPOSITION OF ZINO BT SIMPLE IMMERSION. 355 

Roqne, cast and wronght-iron artioles may be coated with zinc in the 
following way : — ^A mixtoie is first made consisting of (by measure) 
hydroohloiio acid 550 parts, solplmrio acid 60 parts, water 1,000 
parts, and glycerine 20 parts. The iron articles are first pickled in this 
mixture and then placed in a solution composed of carbonate of 
potassa 1 part and water 10 parts. The articles are next to be 
mmiersed from three to twelve hours in a mixtnre composed as 
follows: — water 1,000, chloride of aluminium 10, bitartrate of 
potassium 8, chloride of tin 6, chloride of zinc 4, and add sulphate of 
aluminium 4 parts. The thickness of the deposit is regulated by 
the length of the immersion. 

Bennaim'a Zinc Frooesa. — By this process, which was patented 
in Grermony in 1883^ zinc is dejx^sited by electrolysis from dilute solu- 
tions of sulphate of zinc with the aid of sulphates of the alkalies, or 
alkaline earths — ^potassium, sodium, ammonium, strontium magne- 
sium, or aluminium — either added singly, or mixed together. The 
addition of these salts is only advantag^us when dilute solutions of 
sulphate of zinc are to be treated. According to TTiliiLni^ during the 
electrolysis of a solution of sulphate of zinc of I '33 specific gravity 
(the anodes and cathodes consisting of zinc plates), the evolution of 
gras is greatest with a weak current, diminishing with an increasing 
current, and ceasing when on one square centdmdtre electrode surface, 
three milligrammes of zinc are precipitated per minute. The deposit 
obtained with a strong current was very firm. From a 10 per cent, 
solution the deposit was best with a current yielding from 0*4 to 0*2 
milligpramme of zinc. From very dilute solutions the zinc was always 
obtained in a spongy condition, accompanied by copious evolutions of 
hydrogen. With a weak current and from a i per cent, solution, 
oxide of zinc was also precipitated, even with an electro-motive force 
of 17 volts, when only 0'0755 milligramme of zinc per minute was 
deposited on one square centimetre of cathode surface. The size of 
the electrode surfaces must therefore be adjusted aooording to the 
strong^ of the current and the degree of concentration of the elec- 
trolyte.* 

* For further detaih concerning the electro-deposition of zinc, see p. 631. 



CnAPTEB XXIII. 

ELEOTEO-DEPOSinON OF VARIOUS METALS. 

Electro-deposition of Platinum. — Electro-deposition of Cobalt — Electro- 
deposition of Palladium. — Deposition of Bismuth. — Deposition of 
Antimony. — Deposition of Lead. — Metallo-Chromes. — Deposition of 
Aluminium. — Deposition of Cadmium. — Deposition of Chromium. — 
Deposition of Manganium. — Deposition of Magnesium. — Deposition of 
Silicon. 

Thebe are many metals which have been deposited by electrolysLs 
more as a matter of fact than as presenting any practical advantage 
in a conunercial sense ; others, again, possessing special adyantages 
which would render their saooessful deposition a matter of some 
importance, have been the subject of much exx>eriment, in the hope 
that the difficulties which stood in the way of their being practically 
deposited for useful purposes could be oreroome. Of these hitter, 
the intractable but most valuable metal, platinum, may be considered 
the most important. 

Bteetro-d^poaltloii of natmim. — The peculiar attributes of this 
interesting metal — its resistance to the action of oorrosiTe acids, and 
of most other substances, render it invaluable in the construction of 
chemical apparatus, while its high cost, its infusibility, and the g^reat 
difficulty experienced in giving this metal any required form, greatly 
limit the area of its usefolness. If, however, articles of copper, 
brass, or Gkrman silver — metals which may be so readily put into ehape 
by casting, stamping, or by any ordinary mechanical means — could 
be successfully and eoonomioaUy coated with platinum, this branch of 
the art of electro-deposition would soon meet with considerable sup- 
port from the manufaeturers of chemical apparatus, as also from 
opticians, who woxild gladly adopt electro-platinised* articles for 
many purposes of their art. 

* To contradistinguish the art of depositing bright reg^line platinum upon 
metals from the process of platinising, devised by Smee for imparting a 
black powdery film upon silver for the negative plates of voltaic batteries, 
the term platinating has been proposed, but we would suggest that a simpler 
term would be platining. mectro-platinising would be a more correct term 
than platinating. 




ELECTRO- DEPOSITION OF PLATINUM. 357 

One great difficulty that stands in the way of depositmpf platinum 
economically and of any required thickneBR is that the anodes do not 
dissolve in the solutions which have as yet been adopted for its depo- 
sition ; consequently, unless repeated additions of a platinum salt are 
made as the solution becomes exhausted, it is impossible to obtain a 
coating of sufficient thickness for any practical purpose. In order to 
meet this difficulty in some degree, the author suggested in his former 

work that the strength of the solution may 
be kept up in the same way as he recom- 
mended for electro-tinning ; that is to say, a 
reservoir, containing concentrated platinum 
solution, is placed upon a shelf a little 
above the electro-platinising bath (Fig. 
118), and the strong liquid is allowed to 
drip or flow out through a tap in the reser- 
voir, and trickles at any required speed, 
into the solution bath, whils depoiition is 
Jg- 119- ffoinff on, and in this way the strength of 

the bath may be kept up to any desired density. For small quanti- 
ties of solution, the funnel arrangement shown in Fig. 119 may be 
adopted. The concentrated platinum solution being made in part 
from a portion of the larger solution, instead of with water, the 
original quantity of the liquid may be very fairly balanced. For 
example, if we take, say, one quart of the platinising solution and 
add to this a considerable proportion of platinum salt and the solvent 
employed in its preparation, so as to make as strong a solution as 
possible, when this is added and returned to the bath in the way above 
indicated, it will not add much to its original bulk. By weighing 
the articles before and after immersion, the weight of metal deposited 
may soon be ascertained (the time occupied being noted), and if the 
exact percentage of metal in the concentrated liquor is previously 
determined, there will be no difficulty in determining at what speed 
the strong solution should be allowed to flow into tiie batb to keep 
it up to the proper strength. Another suggestion we have to make 
is this : since the platinum anode does not become dissolved during 
electrolysis, a carbon anode may be substituted, which, in large opera- 
tions, would add much to the economy of the process. 

Preparation of Chloride of Fhtinum. — As in the case of gold, this 
metal must first be dissolved in aqita reffia, to form chloride of platimmi, 
previous to making up either of the baths about to be described. For 
this purpose, fragments of platinum, which may be pieces of foil or 
wire, are put into a glass flask, and upon them is to be poured two to 
three parts of hydrochloric acid and one part nitric acid ; the flask is 
then placed on a sand bath, and gently heated until the red fumes at 



358 ELEOTRO-DEPOSITION OF VARIOUS METALS. 

first given off cease to appear in the bulb of the flask. A solution of 
a deep red colour is formed, which must now be carefully poured into 
a porcelain evaporating dish, placed on the sand bath, and heated 
until nearly dry, moving the vessel about, as recommended in 
treating chloride of gold, until the thick blood-red liquor ceases to 
flow, at which period the vessel may be set aside to cool. Any undis- 
solved platinum remaining in the flask may be treated with nitro- 
hydrochloiio acid as before until it is all dissolved. The dry mass is to 
be dissolved in distilled water, and the subsequent solution, after 
evaporation, added to it. If the original weight of the platinum is 
known, it is a good plan to dissolve the dried chloride in a definite 
quantity of distilled water, so that ui using any measured portion of 
the solution, the percentage of actual metal used may be fairly deter- 
mined when making up a solution. 

Cyanide of Flaiinum Solution. — ^Take a measured quantity of the 
chloride of platinum solution representing about five pennyweights of 
metal, and add sufficient distilled water to make up one pint. Now 
add of strong solution of cyanide sufficient to precipitate and redis- 
Bolve the platinum ; add a little in excess, filter the solution, and 
make up to one quart with distilled water. The solution must be 
heated to about 130° Fahr. when using it. A rather weak current 
from a WoUaston or Daniell battery should be used ; if too strong a 
current be applied, the deposit will probably assume the form of a 
black powder. 

Depotition hy Simple Immersion. — ^Platinum readily yields itself up 
when brass, copper, G^erman silver, &c., are immersed in its solutions, 
but the deposit is of little or no practical use. It may also be depo- 
sited from its solution by contact with zinc as follows : — Powdered 
carbonate of soda is added to a strong solution of chloride of platinum 
until no further effervescence occurs ; a little glucose (g^pe sugar) is 
then added, and lastiy, as much common salt as will produce a whitish 
precipitate. The articles of brass or copper are put into a zinc 
colander and immersed in the solution, heated to about 140° Fahr., 
for a few seconds, then rinsed and dried in hot sawdust. 

Deposition by Battery Current. — ^Roseleur describes a solution from 
which he obtained platinum deposits of considerable thickness. The 
solution is prepared as follows : — 

Platinum, converted into chloride . . 10 parts. 
Distilled water ... • • Soo „ 

Dissolve the chloride in the water, and if any cloudiness appears in 
the solution, owing to the chloride having been over-heated during 
the last stage of the evaporation, it must be passed through a filter. 



BLBOTBO-DXPOSITION OF PLATINUM. 359 

Pboephate of ammonia (crystaUised) loo parts. 

Difltilled water 500 „ 

Dissolye the phosphate in the above quantity of water, and add the 
liquid to the platinum solution, with brisk stirring, when a copious 
precipitate will be formed. To this is next added a solution of — 

Phosphate of soda S^^o parts. 

Water (distilled) x,ooo „ 

The above mixture is to be boiled until the smell of ammnnia ceases 
to be apparent, and the solution, at first alkaline, reddens blue litmus 
paper. The yellow solution now becomes colourless, and is ready for 
use. This solution, which is to be used hot, with a strong battery 
ourrent, is recommended for depositing platinum upon copper, brass, 
and Gkfrman silver, but is unsuited for coating zinc, lead, or tin, since 
these metals decompose the solution and become coated in it by simple 
immersion. Since the platinum anode is not dissolved in this solu- 
tion, fresh additions of the chloride must be made when the solution 
has been worked. 

Boetiger^B Solution for Depositing Flatinum consists of a boiling-hot 
mixture of chloride of platinum solution and chloride of ammonia 
(sal-ammoniac), to which a few drops of liquid ammonia are added. 
The solution, which is weak in metal, requires to be revived from time 
to time by additions of the platinum salt.* 

Bleetso-d^poailioa of Cobalt. — Until somewhat recentiy the elec- 
tro-deposition of cobalt had chiefly been of an experimental character, 
based upon the belief, however, that this metal, if deposited under 
favourable conditions, was susceptible of some useful applications in 
the arts. The difficulty of obtaining pure cobalt anodes — as was the 
case with nickel until a comparatively few years ago— as a commer* 
dal article, stood in the way of those practical experimentalists who 
would be most likely to turn the electro-deposition of this metal to 
account. Moreover, the extremely high price of the metal, even if 
rudely cast in the form of an ingot, rendered its practical application 
all but impossible. That unfavourable epoch is now passed, and we 
have cobalt anodes and ** salts " in the market, as easily procurable, 
though not, of course, at so low a price, as the corresponding nickel 
products. The author is indebted to the courtesy of the enterprising 
firm of cobalt and nickel refiners, Messrs. Henry Wiggin & Co., of 
Birmingham, for some excellent examples of their single and double 
cobalt salts and rolled cobalt anodes, and is thus enabled to state that 
those who may desire to embark in the electro-deposition of this 
metal can readily obtain the chief requisites, the salts and anodes, in 

* For further details concerning the electro-deposition of platiiiam, see 
pp. 441, 443. 



360 ELECTRO-DEPOSITION OF VARIOUS METALS. 

any desired quantity from this firm at the following rates : — ^Rolled 
and oast cobalt anodes, 168. per lb.; single cobalt salts, $8. 6d. per lb. ; 
double cobalt salts, 4s. 6d. per lb. 

Characteristics of Cobalt. — Believing that this metal is destined to 
take an important position in the art of electro -deposition at no dis- 
tant period, a few remarks upon its history, and the advantages 
which it presents as a coating for other metals, may not be unwelcome. 
Cobalt, like its mineral associate, nickel,* was regarded by the old 
Gkrman copper miners with a feeling somewhat akin to horror, since 
its ore, not being understood, frequently led them astray when search- 
ing for copper. Brande says, ** The word cobalt seems to be derived 
from Cobalus, which was the name of a spirit that, according to the 
superstitious notions of the times, haunted mines, destroyed the 
labours of the miners, and often gave them a great deal of unneces- 
sary trouble. The miners probably gave this name to the mineral 
out of joke, because it thwarted them as much as the supposed spirit, 
by exciting false hopes, and rendering their labour often fruitless ; 
for as it was not known at first to what use the mineral could be 
applied, it was thrown aside as useless. It was once customary in 
Germany to introduce into the church service a prayer that Gk)d would 
preserve miners and their works from kobalts and spirits. Mathesius, 
in his tenth sermon, where he speaks of eadmia fossilis (probably cobalt 
ore) says, ' Ye miners call it cobalt : the Germans call it the black 
devil, and the old devil's hags, old and black kobel^ which by their 
witchcraft do injury to people and to their cattle.' " 

In chemical works cobalt is generally described as a reddish-grey 
metal, and this fairly represents the tone of its colour, though a tvarm 
steel grey would perhaps be a more appropriate term. When depo- 
sited by electrolysis under favourable conditions, however, cobalt is 
somewhat whiter than nickel, but it acquires a warmer tone after 
being exposed to the air for some time. Becquerel states that cobalt, 
deposited from a solution of its chloride, '* has a brilliant white colour, 
rather like that of iron ; " while GkdfEe says that, when deposited 
from a solution of the double sulphate of cobalt and ammonium, it is 
'< superior to nickel, both in hardness, tenacity, and beauty of colour." 
Wahl remarks, " The electro-deposits of this metal which we have 
seen equal, if indeed they do not surpass, those of nickel in whiteness 
and brilliancy of lustre." Much of the beauty of electro-deposited 
cobalt depends, not only upon the electrolyte employed, but also upon 
the quality of the current, as is also the case with nickel, and indeed 
most other metals and tiieir alloys. 

* Nickel was called, by the old German miners^ kupfernickel, or ** false 
copper." 



DEPOSITION OF COBALT. 36 1 

Aooordmg to Deville, cobalt is one of the most ductile and tenacious 
of metals, its tenacity being almost double that of iron. It is fused 
with great difficulty, but more readily when combined with a litUe 
carbon, in which respect, as in many other characteristics, it bears a 
dose resemblance to its mineralcgical associate, nickel. It is soluble 
in sulphuric and hydrochloric adds, but more freely in nitric acid. 

Oobalt Solutions. — ^The salts most suitable for making up cobalt 
baths are : — i. Chloride of cobalt, rendered neutral by ammonia or 
potash ; 2. the double chloride of cobalt and ammonium ; and 3, the 
double ndphate of cobalt and ammonium. 

Chloride of Cobalt. — ^The single salt (chloride) may be prepared by 
diseolTing metallic cobalt or its oxides (the latter being the most 
readily soluble) in hydiochlorio acid, and evaporating the solution to 
dryness. The residuum is then heated to redness in a covered crucible, 
when a substance of a bright blue colour is obtained, which is pure 
chloride of cobalt. When this anhydrous (that is without water) 
chloride of cobalt is dissolved in water it forms a pink solution, 
which, by careful evaporation, will yield crystals of a beautiful red 
colour. This is hydrated chloride of cobalt, from which various cobalt 
baths may be prepared according to the directions given below. 

BecquereVe Solution. — ^This is formed by neutralising a concentrated 
solution of the chloride of cobalt by the addition of ammonia or caustic 
potash, and adding water in the proportion of i gallon to 5 ounces 
of the salt. The bath is worked with a very weak current, and the 
deposit is in coherent nodules, or in uniform layers, according to the 
strength of the current. The deposited metal is brilliantly white, 
hard, and brittle, and may be obtained in cylinders, bars, and medals, 
by using proper moulds to receive it. The deposited rods are mag- 
netic,* and possess polarity. If an anode of cobalt be used, the solu- 
tion is of a permanent character. A portion of the chlorine is disen- 
gaged during the electro-deposition, and if iron be present in the 
solution, the greater portion of it is not deposited with the cobalt. 

JBeardslee*s Solution. — ^The following has been recommended by Mr. 
G. W. Beardslee, of Brooklyn, New York, and ia stated to yield a 
good deposit of cobalt, which is ** very white, exceedingly hard, and 
tenaciously adherent." Dissolve pure cobalt in boiling muriatic acid, 
and evaporate the solution thus obtained to dryness. Next dissolve 
from 4 to 6 ounces of the resulting salt in i gallon of distilled 
water, to which add liquid ammonia until it turns red litmus paper 
blue. The solution, being thus rendered slightly alkaline, is ready 
for use. Battery power of from two to five Smee cells will be suffi- 
cient to do good work. Care must be taken not to allow the solution 

* Far«day says that perfectly pure cobalt is not magnetic. 



n 
ft 



362 BLKCTBO-DEPOSITION OF VABIOtJS METALS. 

to lose its alightly alkaline condition, upon whioh the whitenoBB, 
uniformity of deposit, and its adhesion to the work greatly depend. 

Boettger'» Solution. ^Boettger states that from the following solu- 
tion a hrilliant deposit of metallio cobalt was obtained by means of a 
current from two Bunsen cells. 

Chloride of cobalt ..... 40 parts. 
8al-ammonlae •.••.. 20 
Liquid ammonia • . • • . 20 

Water 100 

By another formula it is recommended to dissolve Are ounces of dry 
chloride of cobalt in one gallon of distilled water, and make the 
solution slightly alkaline by means of liquid ammonia. A ounent 
from three to five Smee cells is employed, with an anode of cobalt. 
Hie solution must be kept slightly alkaline by the addition of liquid 
ammonia whenerer it exhibits an acid reaction upon litmus paper. 
Since these solutions are liable to become add in working, it is a good 
plan to keep a strip of litmus paper floating in the bath, so that any 
change of colour from blue to red may be noticed before the altered 
condition of the bath has time to impair the colour and character of 
the deposited metal: if some such precaution be not adopted, the 
deposit may assume a black colour and rescouring be necessary. 

Double SulphaU of Cobalt and Ammonia. — Cobalt is freely deposited 
from a solution of the double salt, of a fine white colour, provided that 
an excess of ammonia be present in the bath. Eromfour to six ounoee 
of the double salt may be used for each gallon of water in making up 
a bath, according to the strength of current employed. The solution 
of this salt and that of the double chloride more readily yield up 
their metal than the corresponding salts of nickel, therefore a propor- 
tionately smaller quantity of the metallic salts are required to make 
up a cobaltmg bath.* 

Bleetvo-depoaltion off Palladitiin.— This metal may be deposited 
more freely from its solution than platinum ; it is dissolved in aqua 
regia and treated in the same way as the latter metal, and the dry salt 
dissolved in distilled water. This palladium is then precipitated by 
means of a solution of cyanide of potassium, and the precipitate redis- 
solved by an excess of the same solution. Since a palladium anode 
becomes dissolved in the cyanide bath, deposite of any required thick- 
ness may be obtained. This metal may also be deposited from a 
solution of the ammonio-chloiide, using a palladium anode, and a 
current from two or three Smee cells. M. Bertrand advises a neutral 
solution of the double chloride of palladium and ammonium for the 
electro-deposition of this metal either with or without the use of a 

* For further remarks on the electro-deposition of cobalt, see p. 464 et aeq. 



DEPOSITION OF ANTIMONY. 363 

roltaio battery. The deposition of palladium is, however, more inter- 
esting as a fact than of any practical use.* 

D^poottloB Of Blsmatli.~<Thi8 metal may be dissolved in dilute 
niizio add (2 parts add to i part water) with moderate heat, and the 
solution evaporated and allowed to crystallise. The resulting salt is 
known as acid nitrate of bismuth, which may be dissolved in a very 
■mall quantity of distiUed water ; but if the solution, even when add, 
be poured into a large quantity of water it becomes decomposed, and 
forms a white, somewhat crystalline predpitate, commonly called 
aubnitrate of bisnmthf bane nitrate, or pearl white^ If strong nitrio add 
be poured upou powdered bismuth the chemical action is intensely 
violent, and ignition sometimes results. Chloride of bismuth is formed 
by dissolving the metal in 4 parts of hydrochloric acid and I part nitrio^ 
by measure, the exoess add being expelled by evaporation. 

To deposit bismuth upon artidee of tin by simple immuersion, Oom- 
maille employs a solution form by dissolving 10 grains of nitrate of 
bismuth in a wineglassful of distilled water, to which two drops of 
nitrio add have been added. After the artide is immersed the bismuth 
win be depodted in very small shiny plates. The metal may also be 
depodted by means of the separate battery. The depodted metal is 
said to be explodve when struck by a hard substance. 

Bismuth may be depodted from a cyanide solution^ but since the 
anode is not fredy acted upon by the cyanide the solution soon becomes 
exhausted. M. A. Bertrand states that bismuth may be depodted 
upon copper or brass from a solution consisting of 30 gnunmes of the 
double ohloiide of bismuth and ammonium, dissolved in a litre of 
water, and slightly acidulated with hydrochloiio add. A current 
from a single Bunsen cell should be used. 

Deposition of Antimony. — Chloride of antimony, terchloride of 
antimony, or, as the andents termed it, butter of antimony, is thus pre- 
pared, according to the pharmacopceias : i lb. of prepared sulphuret of 
antimony is dissolved in commercial muriatio acid, 4 pints, by the aid 
of gentle heat, gradually increased to ebullition. The liquid is filtered 
until qmte clear, then boiled down in another vessel to 2 pints ; it is 
then cooled, and preserved in a well stoppered bottle. The solution 
has a specific gravity of i '490. It is highly caustic. 

A solution of chloride of antimony may also be prepared by the 
eleotrolytio method, that is by passing a moderatdy strong current 
tiirough an anode of antimony, immersed in hydrochloiio add, em- 
ploying a plate of carbon as the cathode, the action being kept up 
until a strip of dean brass, being substituted for the carbon plate, 
promptiy receives a coating of antimony. 

* For further details concerning the electro-deposition of palladiam. see 
p. 473. 



364 ELECTRO- DEPOSITION OP VARIOUS MKTALS. 

Anothor solution may be prepared by digesting recently precipi- 
tated teroxide of antimony in concentrated hydrochloric acid, and 
then adding an excess of free acid to the solution thus obtained. 
This solution yields a very quick and brilliant deposit of antimony 
upon brass or copper surfaces with a current from three small Daniell's 
cellSi arranged in series, with electrodes of about equal surface. 
The fresh teroxide may be readily formed thus : Dissolve 4 ounces of 
finely powdered tersulphuret of antimony in i pint of muriatic acid, 
by the aid of gentle heat, by which a solution of terchloride of anti- 
mony is obtained ; filter the liquid, and then pour it into 5 pints of 
distilled water. By this dilution a g^^eater part of the terchloride is 
decomposed, the chlorine unites with the hydrogen of the water, 
forming hydrochloric add, and the oxygen of the water, being set 
free, unites with the antimony, forming a teroxide, that is, an oxide 
oontaining three equivalents of oxygen. The teroxide thus obtained 
is separated by filtration, and washed, to free it from acid. It is 
then washed with a weak solution of carbonate of soda, which decom- 
poses any terchloride present, leaving the teroxide free. It is then 
dried over a water bath, and preserved in a well-stoppered bottle. 

Antimony may also be deposited from a solution prepared by dis- 
solving oxyohloride of antimony in strong hydrochloric acid, the 
latter being in excess. The oxychloride may be obtained by largely 
diluting with water a solution of the chloride of antimony, when a 
white precipitate falls, which is insoluble in water. The liquor is now 
to be poured off, and hydrochloric acid added until the precipitate is 
entirely dissolved. The resulting solution, which must not be diluted 
with water— which decomposes it — should be used with a moderate 
current and rather small anode surface, and the articles to be coated 
in it must be perfectly dry, and when the required deposit is obtained 
the article should be dipped in a strong solution of hydrochloric acid 
before being rinsed in water, otherwise a white insoluble film of oxy- 
chloride will form on the surface. 

A depositing bath may also be formed by mixing equal parts, by 
measure, of a solution of commercial chloride of antimony and sal- 
ammoniac. The solution thus formed is a very good conductor, 
deposits freely a good reguline metal, and is not so liable to yield 
deposits upon the baser metals by simple immersion as the former 
solution. 

A very good antimony bath may be made by dissolving tartar emetic 
(potassio-tartrate of antimony) in 2 parts hydrochloric acid and i part 
water, by measure; or, say, tartar emetic 8 lbs., hydrochloric add 
4 lbs , and water 2 lbs., a lsj*ger proportion of water being added if 
desired. The rasulting solution forms a very g^od bath for the 
deposition of antimony, and yields up its metal very freely. With 



DEPOSITION OF LEAD. 365 

tbe current from two to three Daniellfi the metal is deposited Tery 
quickly, and in a good reguline condition. To insure the adherence of 
the deposit, however, the anode surface should at first be small, until a 
film of moderate thickness has been obtained, after which it may be 
gradually increased until both electrodes are of about equal surface. 
The above solution is not affected by atmospheric influence nor by 
continual working, and would be very useful for small operations for 
producing thick deposits of antimony ; but the cost of the mixture 
woidd preclude its adoption except for experiment. 

Deposition by Simple Imtnertion. — ^The add solution of chloride of 
antimony readily yields up its metal to brass by simple immersion, 
and by this means brass articles are coloured of a lilac tint. A solution 
is made for this purpose by adding a large quantify of water to asmall 
quantity of chloride of antimony, when a dense white precipitate of 
oxychloride of antimony is formed. The mixture is boiled until this 
is nearly redissolved, when more water is added, and the boiling 
resumed. The liquor is then filtered, and the clear liquor heated to 
boiling ; into this the cleaned brass articles are placed, when they at 
once receive a coating of antimony of a lilac colour, being kept in the 
boiling solution until the desired shade of colour is obtained. After 
rinsing in clean water, the articles are dried in hot sawdust, then 
brushed clean and lacquered. 

Commercial chloride of antimony (butter of antimony) is also used 
for bronzing or hrouming gun-barrels, and when used for this purpose 
it is known as bronzing salt. To apply it for bronzing gun-barrelfl the 
chloride is mixed with olive-oil, and rubbed upon the barrel, slightiy 
heated ; this is afterwards exposed to the air until the requisite tone 
is obtained ; a little aquafortis is rubbed on after the antimony to 
hasten the operation. The browned barrel is then carefully oleuied, 
washed with water, dried, and finally burnished or lacquered. 

When a piece of clean zinc is inmiersed in a solution of chloride of anti- 
mony the metal becomes reduced to a fine grey powder, which is em- 
ployed to give the appearance of g^rey cast-iron to plaster of Paris casts. 

Deposition of Zi«ad.* — Lead is readily produced from a solution 
of its nitrate or acetate — as exemplified in the production of the well- 
known lead-tree; it may also be deposited upon zinc or tin from a 
solution formed by dissolving litharg^e (oxide of lead] in a solution of 
caustic potash. Iron articles will become coated, by simple immersion, 
in a solution of sugar of lead (acetate of lead). Beoquerelf deposited 
lead upon a bright, cleaned surface of copper, in contact with a piece 
of zinc, in a solution of chloride of lead and sodium. This metal may 

* See also pp. 446 et seq. 

f '< The Chemist," vol. v. p. 408. 



S66 



ELECTRO-DEPOSITION OF VARIOUS METALS. 



also be deposited, by means of the batterj, from dilute solutioDfl of 
acetate or nitrate of lead, or from a solution formed by saturating a 
boiling solution of caustic potash with litharge, employing a lead anode. 
The deposition of this metal is not, however, of any commercial im- 
portance. The electrolysis of salts of lead under certain conditions 
are, howeyer, exceedingly interesting in what is termed tnetaUo- 
ehromy, as will be seen below. 

M«tallo-Cliroin«s. — A remarkably beautiful effect of electro-chemi- 
cal decomposition is produced under the following conditions : A con- 
centrated solution of acetate of lead (sugar of lead) is first made, and 
after being filtered is poured into a shallow porcelain dish. A plate 
of polished st«el is now immersed in the solution, and allowed to rest 
on the bottom of the dish (see Fig. 1 20). A small disc of sheet copper 




Fig. 120. 

is then to be connected to the wire proceeding from the zinc element of 
a constant battery of two or three cells, and the wire connected to the 
copper element is to be placed in contact with the steel plate. If now 
the copper disc be brought as close to the steel plate as possible, with- 
out touching it, in a few moments a series of beautiful prismatic 
colorations will apx)ear upon the steel surface, when the plate should 
be removed, and rinsed in clean water. These colorations are films 
of lead in the state of peroxide, and the varied hues are due to the 
difference in thickness of the precipitated peroxide of lead, the light 
being reflected through them from the polished metallic surface 
beneath. By reflected light, every prismatic colour is visible, and by 
transmitted light a series of prismatic colours complementary to the 
first series will appear, occupying the place of the former series. 
The colours are seen to the greatest perfection by placing the plate 
before a window with its back to the Ught, and holding a piece of 
white paper at such an angle as to be reflected upon its surface. The 
colorations are not of a fugitive character, but will bear a oonsider- 
abie amount of friction without being removed. In proof of the lead 



HETALLO-GHROME8. 3^7 

oxide being dex)osited in films or layers, if the deposit be allowed to 
proceed a few seconds beyond the time when its greatest beauties axe 
exhibited, the coloration will be less marked, and beoome more or 
less red, green, or brown. If well rubbed when dry with the finger 
or fleshy part of the hand a rich blue-coloured film will be laid bm, 
by the removal of the delicate film above it. 

The discovery of this interesting electrolytic phenomenon is due to 
Nobili, who in the year 1826 discovered that when a solution of acetate 
of lead was electrolysed by means of a current from four to six Grove 
cells, a large platinum anode and a platinum wire cathode being 
employed, prismatic colours were produced upon the anode surface ; 
and when the platinum anode was placed horizontally in the acetate 
solution and the negative wire held vertically above it, a series of 
rings in chromatic order were produced. These effects subsequently 
took the name of ''Nobili*s rings," and the interesting discovery 
induced Becquerel, Gassiot, and others to experiment in the same 
direction by varying the strength of the current and employing other 
solutions than the acetate of lead. 

BeequereVs Solution. — ^The following formula was suggested by 
Becquerel : * Dissolve 200 grammes of caustic potash in 2 quarts of 
distilled water, add 150 grammes of litharge, boil the mixture for half 
an hour, and allow to settle. Then pour off the dear liquor, and 
dilute it with its own bulk of water. 

The plan recommended by Hr. Gassiot to obtain ^e-metaUo'ehromet 
ia to place over the steel plate a piece of card, cut into some regular 
device, as shown in the illustration, and over this a rim of wood, the 
copper disc being placed above this. We have found that very beau- 
tiful effects are obtained when a piece of fine copper wire is turned up 
in the form of a ring, star, cross, or other pattern, and connected to 
the positive electrode as before ; indeed, this is one of the simplest and 
readiest methods of obtaining the colorations upon the polished 
metal. A few examples of metaUo -chromes obtained in this way are 
shown in the frontispiece of this work. MetaUo-chromy, as it is 
termed, is extensively employed in Nuremberg to ornament metallio 
toys, the solution used being that suggested by Becquerel, namely, a 
solution of the oxide of lead in caustic soda or potash. MetaHo- 
ohromy has also been adopted in France for colouring bells, and in 
Switzerland for colouring the hands and dials of watches. In using 
the lead solutions to produce metallo-chromes it must be remembered 
that metallio lead becomes deposited upon the cathode, consequentiy 
the solutions in time become exhausted, and must therefore be renewed 
by the addition of the lead salt. 

 " The Chemist,** vol. iv. p. 457. 



368 ELEOTBO-DE POSITION OF VARIOUS METAIiS. 

Metallo'chromet on Ntckel-plated Surfaces. — It will be obvious th&t if 
metallo-chromy were only applicable to platiiiuin or steel smfaces — 
which has generally been the case heretofore — that the usefulness of 
the process as a means of ornamentation for industrial purposes would 
be greatly restricted. While the production of these colorations upon 
platinum foil would only be effected for experimental purposes, the 
application of the process to steel surfaces would necessarily be of a 
limited character, owing to the unsuitablenees of this metal as com- 
pared with brass, Gterman tdlyer, and copper, for the manufacture of 
many articles of utility or ornament. With a view to extend the 
usefulness of these very beautiful colorations, and thus, to a certain 
extent, open up a new field for their application, the author some 
time since turned his attention to polished nickel-plated surfaces, as 
being, of all others, the most suitable, from their extreme brilliancy, 
to exhibit the rainbow tints of metallo-ohromy. His first experiments 
were upon highly-polished surfaces of nickel-plated brass, and the 
results obtained were exceedingly satisfactory. The experiments were 
subsequentiy pursued under varied conditions of working, until the 
most satisfactory method of procedure was arrived at. 

The reader is referred tp pp. 448, et teg., for a detailed description 
of the method adopted to produce these colorations upon nickel-plated 
surfaces, and for some particulars as to salts of lead applicable to the 
purpose. 

Sepoflitloa of JUnmfnmn or Aiwti«««»w — 1*^^^^ remarkable 
metal, which in an oxidised state (alumina) occurs most abundantly in 
nature as a constituent of all days in combination with silica, was 
first obtained in the metallic state by Wohler in the following way : 
Chloride of aluminium and pure potassium are heated in a small 
platinum or porcelain crucible, the heat of a spirit-lamp being suffi- 
cient, for when the substances begin to react upon each other the 
temperature suddenly rises to redness. When the crucible is cold, its 
contents are well washed with cold water, by which a finely divided 
grey substance with a metallic lustre is obtained, which is pure 
aluminium. About the year 1854, Sainte-Clairo Deville, of Paris, 
devoted his attention to this subject, substituting chloride of sodium 
for potassium, and heating the chloride of aluminium with this salt in 
a porcelain crucible to bright redness,* by which the excess of chloride 
of aluminium was disengaged, and in the middle of the resulting 
saline mass larger or smaller globules of perfectly pure aluminium 
were found. 

In reference to the characteristics of this metal, BeviUe says: 



» «* The Chemist.* Edited by John ^wd Ohsrles Watt. Vol. i., new series, 
1854. 



DEPOSITION OF ALUMINIUM. 369 

— '' It is completely iinalterable, either in dry or humid air ; it does 
not tamifih ; and remains brilliant where freshly-cut zinc or tin loso 
their polish. Sulphuretted hydrog'en has no action upon it ; neither 
cold nor boiling water will tarnish it ; nitric acid, whether weak or 
concentrated, or sulphuric acid employed cold, will take no effect 
upon it. Its real solvent is hydrochloric acid. ... It will be easily 
understood that a metal as white [P] and as unalterable as silver, which 
does not tarnish in the air, which is fusible, malleable, ductile, and yet 
tough, and which has the singular property of being lighter than 
glass, would be most useful if it could be obtained. If we consider, 
besides, that this metal exists in considerable proportions in nature, 
that its ore is argil [clay], we may well desire that it should become 
of general use. I have much hope that it may be so, for chloride of 
aluminium is decomposed with remarkable facility by common metals 
at a high temperature, and a reaction of this nature, which I am 
now endeavouring to realise on a larger scale than a mere laboratory 
experiment, will decide this question in a practical point of view.*' 

Not long after the above announcement was made, Sainte- Claire- 
DeviUe, supported in the practical development of his ingenious pro- 
cess by the late Emperor of the French, succeeded in producing alu- 
minium in abundance, and bars of this useful metal entered the market 
as a commercial product to the g^at surprise and delight, not only 
of scientists, but of those workers in metals who know how to appre- 
ciate the importance of a metal possessing such remarkable character- 
istics as aluminium. We all know now what an important position it 
has taken in the arts ; but its usefulness may yet receive further 
development, it is hoped, by some successful process of electro -depo- 
sition. That point, however, has not yet been fully reached, although 
the metal has been deposited with sufficient success to warrant tho 
belief that still more satisfactory results will be obtained by a further 
investigation of the subject. 

Speaking upon the separation of aluminium by electrolysis, Deville 
observes:* — " It appeared to me impossible to obtain aluminium by 
the battery in aqueous liquids. I should believe this to bo an impoH- 
sibility if the brilliant experiments of M. Bunsen on the production 
of barium did not shake my conviction. Still, I must say that all 
processes of this description which have recently been published for 
the preparation of aluminium have failed to give me good results. It 
is of the double chloride of aluminium and sodium, of which I have 
already spoken, that this decomposition is effected. The bath is 
composed of 2 parts b^ weight of chloride of aluminium, with the 
addition of i part of dry and pulverised common salt. The whole is 



* ♦* The Chemist," new series, vol. ii. p. 12, 1855. 

00 



S70 ELEOTBO-DEPOSinON OF YABIOU8 METALS. 

mixed in a porcelain crucible, heated to about 392° Fahr. The com- 
bination IB effected with disengagcement of heat, and a liquid is 
obtained which is very fluid at 392° Fahr., and fixes at that tempera- 
ture. It is introduced into a vessel of glazed porcelain, which is to be 
kept at a temperature of about 392° Fahr. The cathode is a plate of 
platinum, on which the aluminium (mixed with common salt) is 
deposited in the form of a greyish crust. The anode is formed of a 
cylinder of charcoal, placed in a perfectly dry porous vessel, contain- 
ing melted chloride of aluminium and sodium. The densest charcoal 
rapidly disintegrates in the bath and becomes pulverulent ; hence the 
necessity of a porous vessel. The chlorine is thus removed, with a 
little chloride of aluminium, proceeding from the decomposition of the 
double salt. This chloride would volatilise and be eAtirely lost, if 
some common salt were not in the porous vessel. The double chloride 
becomes fixed, and the vapours cease. A small number of voltaic 
elements (two are all that are absolutely necessary) will sufElce for the 
decomposition of the double chloride, which presents but litUe resist- 
ance to the electricity. The platinum plate is removed when it is 
sufficiently charged with the metallic deposit. It is suffered to cool, 
the saline mass is rapidly broken off, and the plate replaced." 

Bunsen electrolysed the fused chloride of aluminium and sodium in 
a deep covered porcelain crucible, divided by a partition of porous 
porcelain, which extended half-way down the vessel. Carbon elec- 
trodes were used, and these were introduced through opening^ in the 
cover. He used a current from ten cells of his zinc and carbon batteiy. 
The salt fused at 662° Fahr. (the boiling point of mercury), and 
readily yielded the metal. The temperature of the liquid should then 
be raised to nearly the melting point of silver, when the particles 
of the liberated aluminium fuse, uniting together into globules, 
which, being heavier than the fused salt, fall to the bottom of the 
crucible. 

Gorbelli has deposited aluminium by electrolysing a mixed solution 
of rock alum (sulphate of alumina) and chloride of sodium or calcium 
with an anode of iron wire, coated with an insulating material, and 
dipping into mercury deposited at the bottom of the solution ; a zinc 
cathode is immersed in the solution. Aluminium deposits upon the 
zinc, and the chlorine set free at the anode unites with the mercury, 
forming chloride of mercury (calomel). 

Thomas and Tilley^a ProeeaSf for which a patent was obtained in 
1854, consists in forming a solution composed of freshly precipitated 
alumina dissolved in a boiling solution of cyanide of potassium. By 
another process, patented in 1855, calcined alum is dissolved in a 
solution of cyamde of potassium. Several other solutions are included 
in the same specification, and the invention includes the deposition of 



DEPOSITION OP OADMnm. 37 1 

alloys of alnminlom with fdlyer, sUver and oopper with tin, sflyer and 
tin, etc. 

JMfieon^t Froe0t» (Amerioan) conaiats in depositing aluminium from 
a solution of a doable salt of aluminium and potassium, of the specific 
gravity i'i6i, employing a current fium three Bunsen cells. 

M. Bertrand states that he has deposited aluminium upon a plate of 
copper in a solution of the double chloride of aluminium and ammo- 
nium by using a strong current. 

GozeU Process. — ^Mr. Gk>ze obtained a deposit of aluminium by the 
single cell method from a dilute solution of the chloride. The liquid 
was placed in a jar, in which was immersed a porous ouU containing 
dilute sulphuric acid ; an amalgamated zinc plate was immersed in 
the acid solution, and a plate of copper in the chloride solution, the 
two metals being connected by a copper conducting wire. At the end 
of some hours the copper plate became coated with a lead-coloured 
deposit of aluminium, which, when burnished, presented the same 
degree of whiteness as platinum, and did not appear to tarnish readily 
when immersed in cold water, or in the atmosphere, but was acted 
upon by dilute sulphuric and nitric acids.* 

D«po«ltton of Oadminin. — This metal is readily soluble in dilute 
nitric, sulphuric, and hydrochloric acids, with disengagement of 
hydrogen, and the respective salts may be obtained in the crystalline 
form by concentrating the acid solutions by evaporation. The hydrated 
oxidej in the form of a gelatinous precipitate, is produced when a 
solution of the alkalies, soda, potassa, &c., is added to a solution of a 
salt of cadmium. The hydrate is white, but becomes brown from loss 
of water when dried by heat. Respecting the electro-deposition of 
cadmium, Smee states that it is difficult to obtain firm, coherent 
deposits from solutions of the chloride or sulphate, but that it may be 
easily deposited in a reguline and fiexible condition from a solution of 
the ammonio-sulphate, prepared by adding sufficient liquid ammonia 
to sulphate of cadmium to redissolve the precipitate at first formed. 
Napier reconmiends the following : *' A solution of cadmium is easily 
prepared by dissolving the metal in weak nitric acid, and precipitating 
it with carbonate of soda, washing the precipitate, and then dissolving 
it in cyanide of potassium. A battery power of three or four pairs is 
required, and the solution should be heated to at least 100° Fahr. The 
metal is white, and resembles tin ; it is very soft, and does not present 
many advantagfes to the electro-metallurg^t." 

Hussfll and lVoolrteh*» Process. — ^This process, for which a patent 
was obtained in 1849, is thus briefly described: '* Take cadmium, and 
dissolve it in nitric acid diluted with five or six times its bulk of water, 



For further remarkB on alaminium depositB, see pp. 476 et $eq* 



37^ ELEOTBO-DBPOSmON OF VABI0U8 METALS. 

at a temperature of about 80^ or 100^ Fahr., adding the dilute acid by 
degrees until the metal is all dissolved ; to this solution of cadmium 
one of carbonate of sodium (made by dissolving i lb. of crystals of 
washing soda in i gallon of water) is added until the cadmium is all 
precipitated; the precipitate thus obtained is washed four or five 
times with tepid water. Next add as much of a solution of cyanide of 
potassium as will dissolve the precipitate, after which one-tenth more 
of the solution of the potassium salt is added to form free cyanide. 
The strength of this mixture may vary ; but the patentees prefer a 
solution containing six troy ounces of metal to the gallon, llie liquid 
is worked at about 100° Fahr., with a plate of cadmium as an anode." 

For depositing cadmium M. A. Bertrand recommends a solution of 
the bromide of cadmium, containing a littie sulphuric acid, or a solu- 
tion of sulphate of cadmium. He states that the deposit obtained is 
white, adheres firmly, is very coherent, and takes a fine polish.* 

Deposition of Obromlnm. — ^In his investigation concerning the 
electrolysiB of metallic salts Bunsen determined the causes which 
most influence the separation of the metal ; these pauses are two in 
number, the principal of which is owing to the density of the current, 
and the other to the greater or less concentration of the electrolyte. 
By density he means the concentration to a single point of '* the elec- 
trical undulations, in a manner analogous to the concentration of 
luminous or calorific rays in the focus of a concave mirror. Let us 
take, for example, a charcoal crucible in communication with the 
positive pole of the battery, and place in it a small capsule of glazed 
porcelain, containing the liquid to be decomposed ; the space between 
the crucible and the capsule is filled with hydrochloric acid, and the 
liquid of the small capsule is put in communication with the battery 
by means of a thin sheet or wire of platinum.* The current is then 
established between a large surface, the charcoal crucible, and a fine 
platinum wire, in which it is concentrated ; the effects are added in 
this direction, and the fluid becomes capable of overcoming affinities 
which have hitherto resisted powerful batteries." The apparatus 
is placed is a porcelain crucible, which is kept warm in a sand bath. 

By the above arrangement Bunsen succeeded in separating chro- 
mium with perfect facility from a concentrated solution of its chloride ; 
the deposited metal, which was chemically pure, presented the ap- 
pearance of iron, but was less alterable in moist air. It refdsted 

* For further remarks on the electro-deposition of cadmium, see <* Arvatf" 
silver plating, p. 473 of this volume. 

f For this purpose the platinum wire must be exactly in the centre of the 
cnicible; if not, by virtue of its tendency to take the shortest road, the 
current is established in preference between the nearest pointSt 



DEPOSITION or MAOMBsnm, 373 

13ie action of even boiling nitrio aoid, but was acted upon by hydro- 
chloric acid and dilate sulphuric acid. Bunsen found that when the 
current was diminiahed, the metal ceased to be deposited in the 
metallic state, but appeared as a black powder consisting of protoxide 
and sesquioxide of chromium.* 

Sepoflitlon of »**«»ff «<««**^ or Iffangmi—it — ^The same eminent 
chemist succeeded in obtaining metallic manganese by the method 
above described from a concentrated aqueous solution of chloride of 
manganese. The metal was separated with the greatest facility with 
a powerfol cuiient, but when the current was weakened black oxide 
of mangfanese was obtained. 

Sepoflitlon of MagBMliiiii* — Bunsen electrolysed fused chloride of 
magnesium at a red heat by the same method as that adopted for 
the separation of aluminium. Magnesinm, being a very light metal, 
i» liable to rise to the surface of the fused mixture and ignite in the 
air; to prevent this, as far as possible, the carbon cathode was 
notched, so that the metal could collect in the notches. M. Bertrand 
says that from an aqueous solution of the double chloride of magne- 
sium and ammonium, a strong current will deposit magnesium upon 
a sheet of copper in a few minutes, the deposit being homogeneou3, 
strongly adherent, and easily polished. 

Deposition of Silicon. — Mr. Qoze reduced the metal silicium from 
a solution of monosilicate of potash, prepared by fusing one j^art of 
silica with 2^ parts of carbonate of potash, the same voltaic arrange- 
ment being adopted, except that a small pair of Smee batteries were 
interposed in the circuit. With a very slow and feeble action of the 
current, the colour of the deposit was much whiter than aluminium, 
closely approximating that of silver. 

We have given the foregoing details concerning the deposition of 
some of the less tractable metals, more with a view to show what 
ingenious methods have been devised for their extraction, or separa- 
tion, than as presenting any absolute practical adyantage. As inter- 
esting deotrolyidc facts they are valuable to the student, while to the 
more practical operator who may devote a portion of his spare time to 
electrolytic experiments, Chevidier Bunsen's methods of conducting 
the electrolysis of salts which do not readily yield up their metal from 
aqueous solutions will prove not only interesting but highly instruc- 
tive. It will not be in accordance with the object of this work, how- 
ever, to enter further into the deposition of metals which have no 
practical significance in the arts.* 

* " The Chemist," new series, vol. i. p. 685. 



CHAPTER XXIV. 

ELECTRO-DEPOSITION OF ALLOYS.* 

PMectro-deposition of Braas and Bronze.— Bnuaing Solutions.— Brunei, Bisson 
and Co.'8 Processes. — De Salzede's Processes.— Newton's Processes.— 
Kussell and Woolrich's Process. — ^Wood's Process.— Morris and Johnson's 
Process.— Dr. Heeren's Process.— Roscleur's Processes.— Walenn'e Pro- 
cesses.— Bacco's Solution. — ^Winckler*8 Solution. — ^American FormuloB. 
Thick Brass Deposits.— Braas Solution prepared by Battery Process. 



Illdetro-d«position of Brass and Bronaa. — The deposition of two 
metals in combination by eleotxo-chemical means, although perfectly 
practical, is far more difficult to aooompUsh satisfactorily than to 
deposit a single metal. For example, the two metals zinc and copper 
are so widely different in all their chazaoteristics — in their melting point, 
ductility, electric relation, and oonductiyity — that when in a state of 
solution great care is necessary to enable us to bring them together 
in the uniform condition of what is termed an alloy . Even when these 
two metals are alloyed in the ordinary way, by fusion, gre&t care must 
be exercised, or the zinc, being a volatilisable metal, will pass away 
into the air instead of uniting with the copper to form broM. The 
copper, melting at a far higher temperature than zinc, is fused or 
melted first, and the zinc gradually added, until the desired object is 
obtained — a bright yellow alloy, the tone or colour of which may be 
varied according to the proportion of either metal. 

In depositing brass from its solution, the nature and strength of the 
electric current are of the greatest importance, for if the electro- 
motive force be too weak copper only will be deposited, and if too 
strong zinc alone will be precipitated upon the receiidng metal. 
Again, if too great a surface of anode be exposed in the bath in propor- 
tion to the size of the article to be coated zinc alone will deposit, the 
reverse being the case, that is copper alone, if the surface of anode is 
too small. A medium between these conditions is absolutely necessary 
(all other things being equal) to ensure a coating of brass of gr(>^ 
colour upon any gfiven article. To make this more clear to the lees 
experienced, we may state, for instance, that a battery composed of the 
two elements, zinc and copper, as the WoUaston and Daniell batteries, 

* See also pp. 45X-454 and pp. 473 ot seq. 



ELEGTBO-DEPOSITION OF BRASS AMD BR0N2G. 375 

are far leas intense, tiiat is to say, they possess feebler electromotive 
force, than Bunsen's battery, with carbon and zinc elements. The 
latter battery, therefore, is more suited to the electro-deposition of 
brass, and is indeed preferable to any other. The qualify of the 
deposit is also much influenced by the temperature of the solution 
and the materials with which it is prepared, some formulse yielding 
solutions which are better conductors than others, and consequently 
offer less resistance to the current. 

In making up solutions for the deposition of alloys, as brass, bronze, 
and German silver, for example, the author prefers to prepare them 
in what may be termed the direct way ; that is to say, instead of form- 
ing the depositing solution from a mixture of the metallic salts and 
their solvents, according to the usual method of preparing such 
solutions, he first dissolves the metallic alloy in its acid solvent — 
nitric or nitro-hydrochlorio acid {aqua regia) — and from the acid 
solution thus obtained he forms the depositing bath by either of the 
methods given below. It may be well to remark, however, that in 
making up a brass bath upon this system, metal of the very best 
quality should be employed, and the solution should be formed from 
the identical sample of brass which is to be used as an anode in the 
depositing tank. The proportions g^ven are for one gallon of solution, 
but it win be readily understood that, adopting the same proportions 
of the materials, a bath of any desired quantity can be prepared. 
8oliittoiis.~iyo. /.—Take of 



Good sheet brass x ouDce. 

Nitric acid (by measure) about .4 ounces. 
Water 2 „ 

Cut up the sheet brass into strips, and put them carefully into a glass 
flask, then pour in the water and acid. To accelerate the chemical 
action the flask should be gently heated over a sand bath, and the 
fumes must be allowed to escape through the flue of the chimney. 
When the red fumes, liberated during the decomposition, cease to be 
visible in the bulb of the fla.Hk the chemical action is at an end, pro- 
vided a portion of undissolved brass remains in the flask. If such be 
not the case a few fragments of the metal should be put into the flask 
and the heat continued, when, if red fumes are agtiin given off, the 
heat should be kept up until the fumes disappear while a portion of 
undissolved metal still remains in the flask. The reasons for giving 
these precautionary details are — i, that it is important there should 
be as littie excess of acid as possible in the solution ; and 2, that the 
strength of commercial nitric acid is very variable, and therefore 
chemically minute proportions cannot advantageously be gfiven. "We 
may say, moreover, that the exact quantity of brass per gallon of solu- 



376 ELECTBO-DEPOSITION OF ALLOYS. 

tion is of no consoquence ; if the proportion nearly approaches that 
giyen in the formula, it will be quite near enough for all practical 
purposes. While touching upon this subject we may also state that 
the active quality of commercial cyanide of potassium also varies 
greatly ; consequently it may be necessary to apply either more or less 
than the quantity specified below, according to the quality of the 
article that may fall into the hands of the user. Upon this subject we 
shall, however, say more hereafter. 

The acid solution of brass must next be poured into a vessel of 
sufficient capacity, and diluted with about three or four times its bulk 
of water. Then add liquid ammonia (specific gravity '880°), gradually 
to the green solution of the metals, stirring with a glass rod, when a 
pale green precipitate will be formed, which will afterwards become 
dissolved by adding an excess of ammonia, forming a beautiful deep 
blue solution. This solution should become perfectly clear when the 
necessary quantity of ammonia has been added, but if such be not 
the case, a little more must be added, with brisk stirring, until the 
precipitate is quite dissolved and a clear solution obtained. The exact 
quantity of ammonia required will depend upon the amount of free 
acid remaining in the metallic solution first prepared. A moderately 
strong solution of cyanide must now be added to the blue solution, 
with constant stirring, until the blue colour entirely disappears. When 
sufficient cyanide has been added to destroy the blue colour, the 
solution will acquire a pinkish tinge, and on the application of a 
little more cyanide solution this will in its turn disappear, and the 
liquid will assume a yellowish tint, when a moderate excess of the 
cyanide must be given as '* free cyanide," and the solution then made 
up to the full quantity (one gallon) by the addition of water. The 
solution should then be set aside to rest for a few hours, when the 
clear liquor may be poured into the depositiag vessel. The last portion 
of the liquor should be passed through a filter, to separate any im- 
purities (chiefly derived from the cyanide) which may be present. If 
convenient, the entire bulk of the solution may be filtered, which is in 
all cases preferable. A brassing bath always works most satisfactorily 
if not used for at least twenty-four hours after being prepared, 
although it may, if required, be used directly after being filtered. 
If to be used hot, the solution may be further diluted. 

Solution II. — One ounce of brass being dissolved as before, the 
solution is to be diluted with about three pints of cold water ; a solu- 
tion of carbonate of potash (about half-a-pound to a quart of water) 
is to be gradually added, with frequent stirring, until no further pre- 
cipitation takes place. The precipitate formed should next be put 
into a filter of unbleached calico stretched over a wooden frame, and 
when the liquor has ceased to drain from it, hot water should be 



BRASSING SOLUTIONS. 377 

poured on to the mass, which must be stured with a wooden spoon, or 
flat strip of wood, so as to assist the washing of the precipitate with 
the water. When the precipitate is thoroughly drained, it is to be 
transferred to a oonyeuient vessel, and redissolved by liquid ammonia, 
which is to be added gradually, and constantly stirred in until the 
whole is dissolved, and a dark blue solution formec' . After reposing 
for a few minutes, the clear liquor may be poured off, and should any 
undissolved g^reen precipitate remain at the bottom of the vessel, 
ammonia must be added to this until dissolved, when the resulting 
blue liquor is to be added to the bulk. A strong solution of cyanide 
IB now to be added to the blue liquor, until its characteristic colour 
has entirely disappeared, after which a moderate excess of the cyanide 
solution is to be added, and the solution then made up to i gallon 
(according to the proportion of metal dissolved) with cold water. The 
repose or filtration as before should be again resorted to. 
Solution III,— 

Acetate of copper 
Sulphate of zinc 
Caustic potash 
Liquid ammonia . 
Cyanide of potassiam 



5 


ounces. 


10 


n 


4i 


lbs. 


z 


quart 


8 


ounces. 



The acetate of copper should be first powdered, and then dissolved in 
about 2 quarts of water. To this add one-half of the ammonia 
(i pint). Now dissolve the sulphate of zinc in i g^aUon of water at a 
temperatnre of 180** Fahr. ; to this add the remaining pint of the 
ammonia, constantiy stirring while the liquid is being added. The 
potash is next to be dissolved in i gallon of water, and the cyanide in 
I gallon of hot water, after which the several solutions are to be mixed 
as follows : The solutions of copper and zinc are to be first mixed, the 
solution of potash then added, and lastiy the cyanide. The whole 
must now be weU stirred, and then allowed to repose for a short time, 
when tiie agitation may be resumed and repeated at intervals during 
a couple of hours or so. Water, to make up 8 gallons in aU, is now 
to be added, and the solution then allowed to rest for a few hours, 
when the clear liquor is to be decanted into the bath. This solution 
should be worked with a strong current, with additions of liquid am- 
monia and cyanide from time to time when the anode becomes foul. It 
is important in working this, as in all other brassing solutions, that the 
anode should be kept clean, a condition which is not possible with ihese 
solutions unless there be an excess of the solvents, cyanide and JiwimnTtift . 
Bni]ii61, Binon, * Oc's Pr o owi ,— i. The brasang solution is 
formed from the foUowiug ingredients, which shoiild each be dissolvei 
in separate vessels : — 



378 ELECTRO-DEPOSITION OF ALLOYS. 

Carbonate of potaasa (salt of tartar) zo pounds. 

Cyanide of potassium z) pound. 

Sulphate of zinc li >» 

Chloride of copper zo onnces. 

Water z2( gallons. 

A sufficient quantity of the potash solution is to be added to the sul- 
phate of zinc and chloride of copper solutions to precipitate all the 
metal in the form of earbonaiet. Liquid ammonia (specific gravity 
'880**) is now to be poured into each vessel, being well stirred in to 
dissolve the respective precipitates, when the solutions are to be 
added to the cyanide solution ; the remainder of the potash solution 
is next to be added, and the whole well stirred ; water is then to 
be added to make up a bath of 12^ gallons. The solution is to bo 
worked with two or more Bunsen batteries, with a large brass 
anode. As before reconmiended, the solution should not be worked 
until some hours after being made, and the clear liquid must bo 
decanted, so as to separate it hx)m any sedimentary matter that may 
be present from impurities in the cyanide or otherwise. After using 
the bath for some time, it will require moderate additions of cyanide 
and liquid aizmionia, to keep the anode free from the white salt of 
zinc which forms upon its surface when the excess of these substances 
has become exhausted. In adding fresh cyanide, a portion of the 
solution zziay be taken out of the bath with a jug, and a few lumps of 
cyanide (say half a pound) added, and as this becomes partially dis- 
solved, the liquid is to be added to the bath, and the jug again filled 
with the solution as before ; in this way the bath may be strengpthened 
with cyaziide without employing water to dissolve it. In warm 
weather, however, when the bath loses water by evaporation, the 
cyaziide znay be dissolved in water before adding it to the bath. 
When either liquid azimioziia or cyanide are to be added to the solu- 
tion, this znay be conveniently done overnight, and the bath well 
stirred, whczi by the following morning the disturbed sediment, which 
always accumulates at the bottom of depositing vessels, will have 
had time to settle. 

Solution 2. — This is prepared from the following ingredients : — 

Sulphate of zinc 2 pounds. 

Chloride of copper z pound. 

Carbonate of potassa 25 pounds. 

Nitrate of ammonia Z2i „ 

The chloride of copper is tu be dissolved in half a gallon of water, the 
carboziate of potash in 6 g^Uozis of water, and the sulphate of zinc 
in half a gallon of hot water. These three solutions are now to be 
mixed, and the nitrate of ammonia added, when the whole are to be 
well uziited by stirring. Sufficient water is next to he added to 



NEWTON'S FB0GEB8ES. 



379 



milic up about 20 gallons of solution, which must be allowed to rest 
for some hours before using it. After working this solution for some 
time it will be necessary to add moderate quantities of liquid ammonia 
and cyanide of potassium, otherwise the anode wiU become foul and 
thus incapable of becoming dissolved in the solution. 

lit 8ala«d#'s VrootMMB. — i. This is prepared from the following 
formula : — 

Cyanide of potassiam 

Carbonate of potassa 

Sulphate of zinc .... 

Chloride of copper . 

Nitrate of ammonia 

Water ...... 



12 


parts. 


. 610 


)) 


. 48 


» 


25 


» 


 305 


« 


. 5000 


»f 



The cyanide is to be dissolved in 120 parts of the water, and the car- 
bonate of potash, sulphate of zinc, and chloride of copper are next to 
be dissolved in the remainder of the water, the temperature of which 
is to be raised to about 150° Fahr. When the salts are well dissolved, 
the nitrate of ammonia is to be added, and the mixture well stirred 
imtil the latter is all dissolved. The solution should be allowed to 
stand for several days before using, and the dear liquor separated from 
any sediment that may have deposited at the bottom of the vessel. 
Solution 2. — 

Cyanide of potassiam . * ... 50 parts. 

Carbonate of potassa 500 „ 

Sulphate of zinc •.•••• 35 », 

Chloride of copper 15 » 

Water 5000 „ 

This solution is to be made up in the same way as No. i. 

Solution 3. Bronzing Solution. — ^This solution is the same as No. i, 
except that 25 parts of chloride of tin are substituted for the sulphate 
of zinc. 

Solution 4. Bronzing Solution. — ^This solution is the same as No. 2, 
with the exception that 1 2 parts of chloride of tin are substituted for 
the sulphate of zinc. This solution is worked waim, that is, at about 
97*^ Fahr. 

]f«wton's riuueasM consist in forming solutions for depositing 
brass or bronze. Ho mixes chloride of zinc with the chloride of 
ammonium (sal-ammoniac), chloride of sodium (common salt), or chlo- 
ride of potassium, dissolved in water. Or he makes a mixture of 
acetate of zinc dissolved in water and acetate of ammonia, soda, or 
potassa. In making up a brassing solution, Newton adds to either of 
the above solutions a proportion of the corresponding salt of copper ; 
for example, with the acetate of zinc he would unite acetate of oopper, 



380 SLEOTBO-DEPOSITION OF ALLOTS. 

and 80 on. In malring a bronzing solution, he dissolyes the doable 
tartrate of oopper and potassa, and doable tartrate of the protoxide 
of tm and potaaaa. He deposits an alloy of zino, tin, and oopper by 
employing a solution oomposed of the following : double cyanide of 
oopper and potassium, '* zincate '* of potassa, and staimate of potaasa. 
The zineaie of potassa he forms by fusing oxide of zino with caustic 
potassa, and the stannaite of potassa, either by fusing oxide of tin with 
caustic potassa, or by dissolving it in a solution of potassa. To form 
a brassing bath, he also employs a solution consisting of a g^yen 
quantity of oxide of copper dissolved in an excess of cyanide of 
potassium ; oxide of zinc and a litUe liquid ammonia are then added, 
and the solution heated from 120° to 140^ Fahr. Water is then added 
to allow the solution to contain 3 ounces of the metallic oxides to each 
gaUon of the solution, that is, 2 ounces of zinc oxide to I ounce of 
copper oxide, being the proportions to form brass. 

BnaMll and H^oolxloli's Piuuew. — ^A solution is made of the 
following : — 

Acetate of copper 10 poands. 

„ zinc .... I poaud. 

„ potassium 10 pounds. 

Water 5 gallons. 

The salts are to be dissolved in the water, and as much of a solution 
of cyanide added as will first precipitate the metals, and afterwards 
rediseolve the precipitate. An excess of cyanide is then to be added, 
and the solution set aside to settie as before. A brass anode, or one 
of zinc and another of oopper, may be used. 

Wood's Vroceas consists in making a solution as follows : — 

Cyanide of potassium (troy weight) . . i pound. 

„ copper 2 ounces. 

„ zinc z ounce. 

Distilled water z gallon. 

When the ingredients are dissolved, add 2 ounces of sal-am- 
moniac. For coating smooth articles, it is recommended to raise the 
temperature of the solution to 160° Fahr., using a strong current. 

Konrls and Jolmaon's Froeou. — ^A solution is made by dissolv- 
ing in z gallon of water — 

Cyanide of potassium i pound. 

Carbonate of ammonia i » 

Cyanide of copper ....*. 2 ounces. 

„ zinc z ounce. 

The solution is to bo worked at a temperature of 150® Fahr., with a 
large brass aziode, and a strong current. 



DB. HEEBEN'8 PBO0E88. ^8 1 



9r. BMirMft's Piuiw. — ^Aooording to this authority,* a brassing 
solution may be prepared by employing a large excess of zino to a 
very small proportion of copper, as follows : — ^Take 

Snlphate of copper z part 

„ zinc 8 parts. 

Cyanide of potassiam x8 » 

The ingredients are to be dissolved in separate portions of warm 
water. The copper and zinc solutions are now to be mixed, and the 
cyanide solution then added, when 250 parts of distilled water are to 
be added, and the mixture well stirred. The bath is to be used at 
the boiling temperature, with two Bunsen cells. By this process it is 
said that very rapid deposits of brass have been obtained upon articles 
of copper, zinc, Britannia metal, &c. 

Boa^lmir'a Proee— e«. — i. Dissolve in 1,000 parts of water, 25 
parts of sulphate of copper and from 25 to 30 parts of sulphate of 
zinc ; or, 12^ parts of acetate of copper and I2| to 15 parts of fused 
chloride of zinc. The mixture is to be precipitated by means of 100 
parts of carbonate of soda previously dissolved in plenty of water, 
with constant stirring. The precipitate is to be washed several times, 
by first allowing it to subside and then pouring off the supernatant 
liquor (which may be thrown away), when fresh water is to be poured 
on the precipitate, and after again stirring it is allowed to subside, the 
washing to be repeated two or three times. After pouring off all the 
water the last time, a solution composed of 50 parts of bisulphite of 
sodium and 100 parts of carbonate of soda dissolved in 1,000 parts of 
water, is to be added, stirring well with a wooden rod. A strong 
solution of commercial cyanide of potassium is now to be added until 
the precipitate becomes just dissolved. From 2J to 3 parts of cyanide 
in excess are now to be added with stirring, when the solution is 
complete. 

Solution 2. — ^To form a cold bath for brassing all metals, dissolve 
15 parts of snlphate of copper and 15 parts of sulphate of zinc in 200 
parts of water ; now add a solution made by dissolving 40 parts of 
carbonate of soda in 100 parts of water, and stir the mixture well. 
The precipitate is allowed to subside, as before, when the clear liquor 
is to be run off, and fresh water added, to wash the precipitate, the 
washing to be repeated several times. To the drained precipitate add 
20 parts of bisulphite of sodium dissolved in 900 parts of water. Now 
dissolve 20 parts of cyanide of potassium and two-tenths of a part of 
arsenious acid (white arsenic) in 100 parts of water, and add this to 
the former liquor. This decolours the mixture and completes the 



« «• 



The Chemist,'' 1855, p. 341^ 



383 ELECTRO-DEPOSITION OP ALLOYS. 

brassing solution. The effect of the arsenioTis acid is to render the 
deposit bright. We were long accustomed to employ small quantities 
of white arsenic with our brassing solutions, and when used with 
moderation considered the addition highly favourable to a good deposit 
of brass. Roseleur recommends, in working this bath, to add a little 
cyanide when the deposit looks earthy, or ochreous, and arsenic when 
it yields a dtdl deposit ; if too red, a little zinc and cyanide are to be 
added ; if too white, a little copper and cyanide ; if the solution works 
tardily, add both zinc and copper salts, and more cyanide ; and since 
the anode does not dissolve freely enough to keep up the streng^ of 
the solution, these additions of the metallic salts and cyanide must be 
made from time to time whenever the bath works tardily. The same 
remedy should be applied to all brassing solutions when they work 
sluggishly. When the above solution, by the additions of the metalHo 
salts, reaches a higher specific gravity than I'OQi, water must be 
added, but the specific gravity must not be lower than i 'O36. 

Solution 3. — ^The following solution is recommended for coating 
steel, cast iron, wrought iron and tin : — Dissolve 2 parts of bisulphite 
of soda, 5 parts of cyanide of potassium (of 75 per cent.), and 10 parts 
of carbonate of soda in 80 parts of distilled water, and add to the 
mixture i part of fused chloride of zinc and i^ parts of acetate of 
copper, dissolved in 20 parts of water. 

Solution 4. — For coating zinc articles, the following solution is 
recommended : — 20 parts of bisulphite of soda and 100 of cyanide of 
potassium (of 75 x)er cent.) aie dissolved in 2,000 parts of water. 
Then dissolve 35 parts of chloride of zinc, 35 parts of acetate of 
copper, and 40 parts of liquid ammonia in .500 parts of water. The 
solutions are now to be mixed and the compound solution passed 
through a filter. 

In working these solutions, if too strong a current be employed, or 
too large a surface of anode exposed in the solution, zino only will be 
dex)osited ; if the current be feeble, or if the articles are kept in 
motion while deposition is taking place, the deposit will be chiefly or 
wholly copper. If a white deposit of oxide of zinc appears upon the 
anode, a small quantity of liquid ammonia should be added to the 
bath. 

Waltnn's Pr o c— — . — A solution for depositing brass is made as 
follows : — Crystallised sulphate of zinc I part, and crystallised nitrate 
of copper 2 parts, are dissolved to saturation. Strong liquid ammonia 
is then added in sufficient quantity to precipitate the oxides and redis- 
solve them. Cyanide of potassium is then added until the purple 
liquid is completely decoloured. The resulting solution should be left 
to repose for a day or two, and may be worked with from i to 3 Smee 
cells, using heat if a brass anode be employed. It is preferred, how- 



walenn's pbocbsses. 383 

ever, to work the solution by a "porous cell arrangement, in which 
the surface of the solution next the zinc or other dissolving plate is 
at a greater elevation than that of the external or depositing solu- 
tion." In working the solution, the hydrated oxides of copper and 
zinc are added from time to time, and, if necessary, ammoniuret of 
copper also. 

For a hot brassing solution, Walenn gives the following formula : — 
A ** solvent solution " is first made, consisting of — 

Cyanide of potassium (standard solution) . 6 parts. 

Nitrate of ammonium „ „ . . i part 

Sulphate of „ „ „ . . 2 parts. 

The standard solution of each salt consists of the solid salt dissolved 
in five times its weight of water. The ingredients being mixed, the 
whole is divided into three parts : 

Free solvent solution x part 

Solution to dissolve cupric cyanide . .5^ parts. 

» »> zinc „ . . . 2t „ 

When the respective cyanides have been dissolved to saturation in the 
above proportions, the free solution is added, and the whole well 
mixed ; ammoniuret of copper is then added, and the solution set 
aside for a day or two. Walenn prevents the evolution of hydrogen 
(or nearly so) during deposition by adding the hydrated oxides of 
copper, or ammoniuret of copper and zinc, in sufficient quantity for 
the purpose. 

By another process he employs solutions of cyanide of potas- 
sium and tartrate of ammonium, in equal proportions. In this 
menstruum he dissolves cyanides, tartrates, carbonates, &c. of copper 
and zinc, and the solutions thus formed may be worked either hot or 
cold. The proportions of the various salts must be varied according 
to the strength of the current employed. 

Walenn makes the following observations on the electro-deposition 
of copper and brass: — '* A solution containing one pound of cupric 
sulphate, and one of sulphuric acid to a gallon of water, dejwsits the 
metal in a solid and compact mass, with a somewhat botiyoidal* 
surface. The addition of one ounce of zinc sulphate (as recommended 
by Napiesr) prevents this botryoidal form, and renders the deposit 
tough, compact, and even. From a solution containing a greater 
proportion of zino sulphate, copper is deposited in tufts or needles, 



* Botryoidal, resembling a bunch of grapes ; referring to the Tiodular or 
knotty form which copper assumes at the back of electrotypes. 



384 EIACTB0-DEP08ITI0N OP ALLOTS. 

standing at right angles to the surface of the metal. Ordinary 
electro-brassing liquids [deposits from] show the same peculiarity in 
even a more marked degree, and this makes it impossible to produce a 
good deposit of more than *oi to '03 inch in thickness. This form of 
deposit is owing chiefly to a copious evolution of hydrogen taking 
place during its formation." While not disagreeing with Mr. 
Walenn*8 views, the author may state that he has found that a small 
quantity of arsenious acid (previously mixed with a strong solution of 
cyanide) added to brassing baths had generally rendered the deposit 
smooth and compact ; the quantity, however, must be small, other- 
wise the deposit is liable to be of a brittle character. About one 
drachm of arsenious acid to each gallon of bath will be sufficient. He 
has usually noticed that brassing solutions evolve hydrogen most 
freely when poor in metal, and when containing a large excess of 
cyanide. A solution richer in metal, and containing but a moderate 
excess of cyanide, gpenerally yields better results, both as to colour 
and general character of the deposit. A great deal depends, however, 
upon the amount of current and its tenHion, and also upon the tem- 
perature of the bath. A solution rich in copper and zinc is best 
worked at about 130° Fahr., or even higher. When the solution 
becomes partly exhausted of its metals, owing to the brass anodes not 
becoming freely dissolved in the solution, it is always advisable to add 
fresh concentrated cyanide solutions of the zinc and copper salts from 
time to time, taking care, however, only to add them in sufficient 
quantity to obtain the desired effect — a coating of good colour with 
but triiling evolution of hydrogen at the negative electrode. 

BacGO's SOlntion. — The following solution is said to yield a brass 
deposit upon zinc work that will stand burnishing, and the deposit 
may be obtained either by simple immersion or by the battery. A 
solution is first prepared by dissolving equal parts of sulphate of zinc 
and sulphate of copper in water. A strong solution of cyanide of 
potassium is then added in sufficient quantity to redissolve the pre- 
cipitate formed ; to the resulting solution one-tenth to one-fifth of 
liquid ammonia is added, and the solution is then diluted with water 
until it stands at about 8" Baume. For a light-coloured deposit of 
brass 2 parts sulphate of zinc to i part sulphate of copper are used. 
In adding C3ranide to the solution of the sulphates, great care must bo 
taken to avoid inhaling the cyanogen fumes that are liberated, which 
euro highly poisonous. A solution of this character should only be 
prepared by a person well accustomed to chemical manipulations. 

WlncklAT's Solution. — Saturated solutions of chloride of zinc and 
sulphate of copper are first prepared, in separate vessels. A solution 
of cyanide of potassium, consisting of cyanide 100 parts m water 
1,000 parts, is next prepared, and this is added to the solution of 



BBASS SOLUTION FOB BOUGH GAST-IBON. 385 

sulphate of copper until the precipitate at first formed is rediasolved, 
when a grass-green liquid results ; into this the solution of zinc is 
gradually introduced, with constant stirring, until the solution 
exhibits a white turbidity. The solution is then diluted with 2,000 
parts of water, and heated to the boiling point in an enamelled 
vessel, and then allowed to cool. It is next filtered, when it is ready 
for use. The bath is worked at the ordinary temperature, with a 
brass anode. 

Braas 861iition for Bongli Oa«t Xron. — The following formula 
has been given for brassing cast-iron work, and is said to yield a 
good colour : — 

Soft water 14 pints. 

Bisulphite of soda 7 ounces 

Cyanide of potaasitun '7 n 

Carbonate of soda 34 m 

To which is added — 

Acetate of copper 4^ ounces. 

Neutral chloride of zinc 3^ » 

Water 3^ pints. 

AnMrtean FonniilflD fiir Bnuwiiis Bolutloiis. — The Scientific 
American publishes the following formulse for brass solutions: — I. 
When tho ordinary commercial cyanide is employed, the following is 
said to answer very well ; — 

Sulphate of copper 4 oonces. 

Sulphate of zinc 4 to 5 „ 

Water i gallon. 

Dissolve and precipitate with 30 ounces of carbonate of soda ; allow to 
settle, pour off the clear liquid, and wash the precipitate several times 
in fresh water. Add to the washed precipitate- 
Carbonate of soda 15 ounces. 

Bisulphite of soda 7i »> 

Water z gallon. 

Dissolve the above salts in the water, assisting the solution by con* 
stant stirring ; then stir in ordinary cyanide of potassium until the 
liquid becomes clear and colourless. Filter the solution, and to im- 
prove its conductivity, an additional half -ounce of cyanide may be 
given. 

Oild Bath for all Metals.— 

Carbonate of copper (recently prepared) . . 2 ounceF. 

f'S 80Qft . - . • f 4 J, 

00 



386 ELKCTBO-DEPOSITIOM OF ALLOYS. 

Butulphite of soda 4 ounces. 

Cyanide of poCaaaium (pure) . . 4 „ 

Areeniouis acid 10 •> 

Water x gallon. 

Dissolve, precipitate, and redissolve as before, and filter if necessary. 
The arsenious acid is added to brighten the deposit ; an excess is apt 
to give the deposited metal a greyish -white colour. 

Thick Braas ]>«pocita. — ^MM. Person and Sire patented a process 
for obtaining stout coatings of braas upon steel or iron by depositing 
alternate layers of zinc and copper upon the objects, and then 
submitting them to heat until the metals become alloyed with each 
other. 

Braas Solution 7r«par»d toy Battary Fgooeia. — ^A brassing 
solution may be prepared by the battery method by suspending a 
large brass anode in a strong and warm solution of cyanide of potas- 
slum, to which liquid ammonia is added; about i^ pound of good 
cyanide and 10 ounces of strong liquid ammonia to the gallon of 
water will be about the best proportions. A strong current must be 
employed. Some persons reoonunend the addition of hydrocyanic 
acid ; this will not be necessary if good cyanide be used. In preparing 
solutions by the battery process, or indeed by the ordinary chemical 
methods, it is far better to employ really good cyanide of a g^uaranteed 
strength than to call in the assistance of hydrocyanic acid, which, 
even in the most careful hands, is a hazardous substance to deal with 
in what may be termed practical quantities. All the best results in 
electro-deposition have been obtained without the direct aid of this 
volatile and highly-poisonous acid, and its employment should never 
be attempted by inexperienced persons under any circumstances 
wiiaUucvex'. 



CHAPTER XXV. 

ELECTRO-DEPOSITION OF ALLOYS {continued). 

Electro-brassiDg Ciut-iron Work. — Scouring. — Electro-brassing Wrought-iroa 
Wurlc. — Electro-brassing Zinc Worls. — Electro-brassing Lead, Pewter, 
and Tin Work.— Observations on Electro-brassing. — Bronzing Electro- 
bniased Work.— French Method of Bronzing Electro-brassed Zinc Work. 
Green or Antique Bronze.— Bronze Powders.— Dipping Electro-brassed 
Work. - Lacquering Electro-brassed Work. — Electro-deposition of 
Bronze. — Electro-deposition of German Silver. — Morris and Johnson's 
Process. — Deposition of an Alloy of Tin and Silver.— Deposition of 
Alloys of Gold, Silver, &e. — Deposition of Chromium Alloys.— Slater's 
Process. — Deposition of Magnesium and its Alloys. — Alloy of Platinum 
and Silver.'New White Alloys.— Notes on Electro-brassing. 

filaetro-lnrMains Cast-Iron IRTork. — Owing to the porous nature 
of this class of work, and its liability to present certain unavoidable 
defects of casting known as sand -holes, the articles to be coated with 
brass require to bo prepared with some care before being immersed in 
the depositing bath. Moreover, it is necessary to remove the coating 
of oxide from the surface of the work previous to submitting the 
articles to the processes of scouring or cleaning. Cast-iron work 
should first be placed in a *' pickle '* composed of the following mix- 
ture, in sufficient quantity for the work in hand : — 

Sulphuric acid i pound. 

Water z gallon. 

The articles being placed in the above pickle are allowed to remain 
therein for about twenty minutes to half an hour, when they are 
taken out, one at a time, and examined; if the oxide has become 
sufficientiy loosened to readily rub off with the lingers, the articles are 
to be at once placed in clean cold water to rinse them ; they are then 
to bo scoured with a hard brush, coarse sand, and water. If after 
rinsing any black oxide obstinately refuses to be brushed away, the 
work must be returned to the pickle for a short time longer, or until 
the objectionable matter readily yields to the brush, leaving a clean 
surface beneath. Some articles require but a short immersion in the 
acid pickle, while others need a much longer steeping. When thtj 



388 EliECTBO-DEPOBITION OF ALLOTa 

articles ore coated with rust (oxide of iron) this may be romoyed by 
brushing thorn over with strong hydrochloric acid, after which they 
sliould be immersed in the sulphuric acid pickle until it is found that 
sand and water, applied with a very hard brush, will clean them. 
A solution for brassing cast-iron work should be very rich in metal. 

Scouring. — When the articles are sufficiently pickled, they are to 
be removed from the bath and well rinsed in clean water ; they are 
then taken to the " scouring tray,*' and being placed on the horizontal 
board, are to be well rubbed with the hard brush and coarse sand 
moistened with water, until they are perfectly bright and clean and 
free from all traces of oxide on their surfaces. They are now to be 
thoroughly rinsed in clean water, and are then ready for the brassing- 
bath. Some operators prefer to give them a momentary dip in a 
weak and cold potash bath, and then rinse them before placing the 
articles in the depositing bath. The work should be suspended in the 
bath by stout copper wires, and in the case of large pieces of work 
several such sUnging wires should be employed, not only to give 
support to the articles, but to equalise, as far as possible, the action of 
the current ; since it must be remembered that oast iron is but an 
indifferent conductor as compared with other metals. 

Bleetro-lmuuins Wiuiislit-iron UToxIc. — ^This class of work is 
more readily coated with brass (and copper) than the former, the 
metal being less porous and the articles generally in a smoother con- 
dition. The work is first to be pickled as before, and afterwards well 
scoured with sand and water, and then rinsed. The solution in which 
wrought- iron goods arc brassed may have rather less metal (that is, 
zinc and coi)per) than is necessary for cast iron. Wlien the articles