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Full text of "The assayer's guide; or, Practical directions to assayers, miners and smelters, for the tests and assays, by heat and by wet processes, of the ores of all the principal metals, of gold and silver coins and alloys, and of coal, &c. By Oscar M. Lieber .."

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THE 

ASSAYER'S    GUIDE; 

OR, 

PRACTICAL  DIRECTIONS 

TO    ASSAYERS, 
MINERS    AND     SMELTERS, 

FOR  THE 

TESTS  AND  ASSAYS,  BY  HEAT  AND  BY  WET  PROCESSES, 

OF    THE 

ORES  OF  ALL  THE  PRINCIPAL  METALS, 

OF 

GOLD    AND    SILVER    COINS    AND   ALLOYS, 
AND  OF  COAL,  &c. 


OSCAR    M. 

1ATE  GEOLOGIST  TO  THE  STATE  OF  MISSISSIPPI. 


A  NEW,  REVISED  A$D*  E 


EDITION. 


PHILADELPHIA: 

HENRY  CAREY  BAIRD  &  CO., 

INDUSTRIAL  PDBLISHERS,  BOOKSELLERS  AND  IMPORTERS, 

810  WALNUT  STREET. 

1907- 


pv^x- 

0' 

Copyright  by 

HENRY  CAREY  BAIRD  &  Co., 
1892. 


77V 


PREFACE  TO  THE  REVISED  EDITION. 


THE  "Assayer's  Guide"  has  so  steadily  main- 
tnined  the  popularity  and  reputation  it  has  en- 
joyed for  many  years,  and  has  met  with  such 
success,  that  it  has  been  determined  to  issue  a 
new  edition  containing,  in  addition,  numerous  re- 
cent and  approved  assaying  methods. 

The  material  for  this  purpose  has  been  largely 
drawn  from  the  articles  on  Metallurgy  contributed 
by  Prof.  Bruno  Kerl  and  others  to  the  fourth  edi- 
tion of  u  Muspratt's  Theoretische,  Praktische  and 
Analytische  Chemie,"  now  being  published  in 
Germany. 

While  many  improvements  in  the  apparatus 
used  in  assaying  have  been  made,  only  a  few  of 
the  most  notable  of  these  novelties  have  been  in- 
troduced, it  being  believed  that  the  implements 
and  utensils  described  and  illustrated  in  the  work 
are  sufficient  for  all  practical  purposes. .  "  • 

The  book  has  also  been  provided  with  a  copious 

(iii) 

255808 


IV         PREFACE  TO  THE   REVISED   EDITION. 

Table  of  Contents  and  a  very  full  Index,  which 
will  render  any  subject  easy  and  prompt  of  ref- 
erence. 

In  its  enlarged  and  revised  shape,  it  is  hoped 
that  the  work  will  fully  maintain  its  claim  to  the 
favor  it  has  so  long  enjoyed  as  a  complete  guide 
in  the  art  of  assaying. 

PHILADELPHIA,  December  1,  1892. 


PREFACE  TO  THE  ORIGINAL  EDITION. 


IN  presenting  this  little  volume  to  the  public,  I 
trust  that  I  am  filling  a  void  in  our  chemical  lit- 
erature. I  believe  there  is  no  work  in  the  Eng- 
lish language  on  assaying  which  combines  with 
practical  usefulness  a  sufficiently  popular  charac- 
ter for  those  readers  who  have  not  made  metal- 
lurgy and  its  kindred  sciences  objects  of  their 
especial  study.  My  desire  is  to  offer  a  book 
which  fully  treats  of  all  the  subjects  of  assaying, 
and  whose  price  will  yet  place  it  within  the  reach 
of  all  persons  professionally  interested  in  this 
important  branch  of  knowledge. 

The  more  compendious  works  on  chemistry,  if 
they  allude  to  assaying  at  all,  give  so  sparing  and 
incidental  remarks,  that  they  do  not  throw  any 
light  upon  it  for  technical  purposes,  as  indeed  it 
does  not  fall  within  their  province  to  do. 

The  immense  mineral  wealth  of  the  United 
States,  to  which  the  discoveries  in  California  have 
so  largely  added,  makes  this  art  a  very  desirable 
acquirement  for  every  one  engaged  in  any  busi- 
ness connected  with  the  metals ;  and  it  would  ap- 
pear indispensable  to  those  desirous  of  deriving 
the  greatest  advantage  from  a  residence  in  that 
promising  and  alluring  part  of  our  country. 

Although  these  pages  principally  treat  of  the 
processes  by  heat,  I  have  thought  it  proper  to  de- 


VI         PREFACE   TO   THE   ORIGINAL    EDITION. 

scribe  also  some  wet  processes,  either  where  they 
serve  as  methods  to  rectify  the  former,  or  where 
no  others  exist;  as,  for  instance,  is  the  case  with 
platinum.  For  the  coins  I  have  selected  those 
employed  at  mints,  and  which  are  therefore  gen- 
erally considered  the  most  serviceable  for  the 
analysis  of  those  alloys. 

I  feel  induced  here  to  recommend  at  least  a 
partial  study  of  blowpipe  assaying  "to  those  who 
may  wish  to  make  use  of  the  instructions  given  in 
this  treatise.  This  infant  branch  of  chemistry 
was  first  created,  I  may  say,  in  Sweden  by  Crom- 
sted,  and  established  more  firmly  by  Gahn  and 
Berzelius,  both  his  countrymen,  and  has  of  late 
been  made  by  Plattner  a  method  even  for  quanti- 
tatively ascertaining  the  contents  of  most  min- 
erals. 

The  requisite  blowpipe  utensils  for  the  mere 
detection  of  the  principal  components  of  ores  are 
so  few,  can  so  easily  be  commanded,  and  may  be  so 
readily  carried  about  one's  person,  that,  at  least  for 
the  purpose  of  a  prior  test,  it  is  very  advisable  to 
possess  some  knowledge  of  their  application, 
which  can  be  acquired  with  great  facility. 

I  cannot  conclude  these  brief  remarks  without 
seizing  upon  the  opportunity  of  acknowledging 
the  liberality  of  a  distinguished  officer  at  Frei- 
berg in  Saxony,  Mr.  Fritzsche,  chief  assayer  of 
that  mining  district.  I  have  made  frequent  use 
of  his  notes  and  hints,  given  me  while  I  had  the 
advantage  of  a  personal  intercourse  with  him. 

O.  M.  L. 


CONTENTS. 


INTRODUCTION. 

PAGE 

Definition  of  assaying,  its  object  and  in  what  it 
differs  from  inorganic  analytical  chemistry  properly 
so  called  ' 17 

Assaying  the  foundation  of  theoretical  chemistry ; 
Antiquity  of  the  art  -  -  -  -  18 

Agricola  and  his  writings  ;  What  should  guide  the 
assayer  in  his  operations  -  -  -  19 

I.    DESCRIPTION  OF  THE  IMPLEMENTS  AND  UTEN- 
SILS USED  IN  THE  COURSE  OP  ASSAYS  BY 

HEAT. 

The  muffle  furnace  and  the  muffle,  illustrated  and 
described  .     -        -        -  . .    -        -        -       -        -    21 

Hessian  crucibles,  illustrated  and  described        -        -22 
Furnace  for  tests  of  iron  ores,  lead  ores,  etc.,  illus- 
trated and  described       -        -        -  -        -    27 

Portable  furnaces       -        -        -        -        -        -        -     30 

The  Battersea  fiirnace  ;  Brecon's  portable  assay  fur- 
nace ;  Other  instruments  used  in  the  assay  of  ores      31 
The  balance,  and  how  weighing  is  to  be  effected        -     32 
Scales  for  weighing  larger  quantities          -        -        -     33 
Crucibles,  cupels  or  cups,  and  tongs,  illustrated  and 
described        -------- 

Mr.  Fritzsche's  recipe  for  the  preparation  of  cupels  - 
Hessian  crucibles  for  the  assay  of  iron  ores,  illustrated 

and  described 37 

Preparation  of  charcoal  for  coating  crucibles     -        -  38 

Pan  for  cooling  buttons  of  metal       -        -        -        -  39 

Tongs,  illustrated  and  described         -        -        -        -  40 

Mode  of  introducing  the  cupels  into  the  muffle         -    41 

(vii) 


Vili  CONTENTS. 


Sieves  and  their  use          ......  43 

Gas  assay -furnaces  44 

Fletcher's  direct-draft  crucible  furnace,  illustrated  and 
described ;  Group  of  gas  furnaces  designed  by 

Walter  Lee  Brown,  illustrated  and  described          -  45 

"  Monitor  "  furnace,  illustrated  and  described  -  48 

Manner  of  operating  Brown's  group  of  furnaces  51 

Management  of  the ''Monitor"        -        -        -        -  52 

II.    RE-AGENTS  USED  IN  ASSAYING. 

Re-agents  for  dry  assays  ;  Reducing  agents  -  -  54 
Composition  of  black  flux,  white  flux  and  gray  flux  55 
List  of  the  reducing  powers  of  various  reducing 

agents  56 

Oxidizing  agents ;   Preparation  of  litharge  entirely 

free  from  silver 57 

Solvent  agents  ;  Acid  solvent  agents          -        -        -    58 

Basic  solvent  agents  59 

Desulphurizing,  or  precipitating  agents      -        -        -    60 
Sulphurizing  agents  ;  Concentrating  fluxes  ;  Decom- 
posing and  volatilizing  fluxes  ;  Air-excluding  fluxes 
(covering  agents)  -        -        -        -    61 

Re-agents  for  wet  assays  ;  For  assays  by  gravimetric 
and  calorimetric  analysis  ;  For  volumetric  assays  -  62 

III.    ASSAY  OF  SILVER  ORES  BY  HEAT 

CUFELLATION. 

Occurrence  of  silver  in  nature ;  Preparation  of  the 
ore  for  investigation  -  -  -  -  -  -  64 

Object  of  the  addition  of  lead  to  the  ore ;  Impurity 
of  the  lead  of  commerce  •  -  65 

Preparation  of  pure  lead 66 

Manner  of  charging  the  crucible  with  the  ore  to  be 
assayed  --------  67 

Advantage  of  making  several  assays  at  one  time       -    68 

Process  of  melting  the  assay 69 

Pouring  out  the  assay       ------    70 


CONTENTS.  IX 

PAGE 

Separation  of  the  slag  from  the  metallic  button ; 
Crucibles  used  in  making  the  assay ;  Silberblick, 
(silver  gleam) 71 

On  what  the  accuracy  of  the  assay  chiefly  depends    -    72 

Adage  current  among  German  smelters  and  assayers  ; 
Treatment  of  the  buttons  of  pure  silver  -  -  73 

Unavoidable  inaccuracies  in  the  shape  of  losses         -    75 

IV.  A  TABLE  TO  RECTIFY  THE  Loss  IN- 
CURRED DURING  THE  SILVER  ASSAY. 

Difference  in  the  results  obtained  in  Freiberg    -        -    79 

V.  GAY-LUSSAC'S  PROCESS  FOR  ASSAYING 

SILVER  ALLOYS. 

Preparation  of  the  assay  -  •  -  -  -  80 
Normal  and  decinormal  solutions  of  common  salt ; 

Decinormal  solution  of  silver ;  Preparation  of  the 

assay  solution         -------  81 

Flasks  illustrated  and  described         -        -        -        -  82 

Titration  of  the  silver  solution  and  apparatus  used    -  83 
Calculation        --------86 

Preparation  of  the  normal  solutions  -  -  -  88 
Gay-Lussac's  tables  for  determining  the  fineness  of 

silver  alloys  -  - 89 

Table  for  decimal  salt  solution 91 

Table  for  decinormal  silver  solution  -  -  -  -  94 
Whittell's  method  of  saving  time  and  insuring  greater 

facility  in  making  Gay-Lussac's  assay    -        -        -  97 

YI.    ASSAY  OF  NATIVE  SILVER  ORES. 
Lowe's  method  ;  Preparation  of  the  ore  -        -        -    99 

VII.    ASSAY  OF  GOLD  ORES  BY  HEAT. 

Similarity  of  the  properties  of  silver  and  gojd,  and 
their  ores  as  regards  the  process  of  cupellation  -  101 


X  CONTENTS. 

PAGE 

Preparation  and  melting  of  the  assays  ;  Manner  of 
ascertaining  the  percentage  amount  of  .gold  in  the 
specimen  under  examination  ;  Preparation  of  per- 
fectly pure  silver  -  102 

Definition  of  quartation    -        -        -        -  -  103 

Treatment  of  the  button  of  gold  and  silver  alloy 

obtained  -----.  -  104 

Manner  of  ascertaining  the  original  amount  of  silver  105 

VIII.     ASSAY  OF  GOLD  ORES  BY  AMAL- 
GAMATION. 

On  what  this  method  is  founded  ;  Purification  of 
mercury ;  Definition  of  the  term  dokimastic  test ; 
Manner  of  making  the  assay  ....  106 

IX.    ASSAY  OF  GOLD  BY  WASHING. 

On  what  the  assay  is  based  ;  Its  employment  in  Cali- 
fornia ;  Vessels  used 108 

Execution  of  the  assay 109 

X.    ASSAY  OF  GOLD  BY  PANNING. 

The  pan  or lt  batea  "  used  in  making  the  test ;  Execu- 
tion of  the  assay  -  -  111 

Example  of  calculating  the  result  of  the  assay ; 
Separation  of  the  free  gold  from  the  sulphides ; 
Preparation  of  an  amalgamated  pan  -  -  -  114 

Klein  Schmidt's  method  of  assaying  gold  by  panning     115 

Another  method  ;  Australian  method       -        -        -  1 1 6 

XL    ASSAY  OF  GOLD  BY  COMBINED  DRY 
AND  WET  METHODS. 

Object  of  these  assays  ;  Manner  of  obtaining  a  correct 

average  sample  of  the  ore  to  be  assayed  -  -  117 
Manner  of  pulverizing  the  sample  -  -  -  -118 
Assays  by  smelting  with  lead  ;  Scorification  assay  -  119 

Execution  of  the  assay 121 

Crucible  assay  ;  Advantage  of  this  assay  -        -  124 


CONTENTS.  XI 

PAGE 

Melting  earthy  gold  ores  or  gold  ores  containing  ferric 

oxide  (also  dross  or  sweepings,  slags)      -        -        -  125 

Charge  for  American  gold  ore  -        .-        -        -  126 

Melting  of  sulphuretted  ores 127 

Fluxes  for  dross  or  sweepings 129 

Cupellation  of  the  auriferous  lead     -        -        -        -  1 30 

Parting  the  gold  from  the  silver        -        -        -        -  131 
Indications  by  which  to  judge  whether  silver  has  to 
be  added  or  not  when  cupelling  the  auriferous  lead 

button  -  132 

Examination  of  black  specks  remaining  behind         -  134 

XII.    ASSAY  OF  GOLD  ORES  BY  A  WET 

PROCESS. 

Preparation  of  the  assay  -  - ;  -  -  -  136 
Execution  of  the  assay 137 

XIII.    ASSAY  OF  SILVER  COINS,  OR  ALLOYS 
OF  SILVER  AND  COPPER. 

Test  for  ascertaining  the  probable  amount  of  silver 
and  copper  -  -/•---  138 

Erker's  table  for  regulating  the  requisite  quantity  of 
lead 139 

Manner  of  preparing  a  sample  of  the  coin  ;  Execution 
of  the  assay 140 

XIV.    ASSAY  OF  GOLD  COINS,  OR  ALLOYS 

CONTAINING   GOLD,  SlLVER  AND  COPPER. 

Touchstone  or  besanite  test  -  -  -  -.  -  141 

Execution  of  the  assay  -  -  -  -  .  -  142 
D'Arcet's  table  for  regulating  the  amount  of  lead  to 

be  used 143 

Mint  units  of  the  various  countries  -  -  145 

Table  showing  the  content,  weight,  etc.,  of  gold  coins 

of  various  countries  -  146 

Table  showing  the  content,  weight,  etc.,  of  silver 

coins  of  various  countries       -  147 


Xll  CONTENTS. 


PAGE 

Table  of  base  coins 148 

XV.  To  FIND  THE  PROPORTION  OF  GOLD  IN  A 
MIXTURE  OF  GOLD  AND  QUARTZ  BY 
CALCULATION. 

Specific  gravity  of  gold  and  of  quartz  ;  Manner  of 
making  the  calculation  -  1 49 

XVI.    ASSAY  OF  PLATINUM  ORES. 

Occurrence  of  platinum  in  the  United  States  ;  Execu- 
tion of  the  assay  -  1 52 

Test  for  ascertaining  the  amount  of  the  alloy  of  gold 

and  platinum  -  154 

Electrolytic  assay  of  platinum  -  156 

Separation  of  platinum  from  iridium  -  157 

XVII.  ASSAY  OF  COPPER  ORES— GERMAN 
AND  HUNGARIAN  METHODS. 

Preparation  of  the  ore       -        -  -        -        -  158 

Black  flux  and  its  preparation  -  159 

Difference  of  opinion  regarding  the  use  of  oxide  of 
antimony,  arsenic  or  lead  ;  Manner  of  charging  the 

crucible  -        -        -  160 

Indications  of  a  good  assay 162 

Removal  of  foreign  metals  from  the  button       -        -  163 

Indications  of  the  presence  of  lead  in  the  button       -  164 

XVIII.  ASSAY  OF  COPPER  ORES— ENGLISH 

METHOD. 

Ores  to  which  this  assay  is  applicable ;  Preparation 
of  the  ore  -  -  ....  165 

Preparation  of  white  flux          -        -       .-        -        -  166 

Treatment  of  the  button  of  copper  alloy ;  Test  of 
the  purity  of  the  copper  -  -  167 

Method  of  diminishing  the  loss  of  copper         -        -  168 


CONTENTS.  xin 

XIX.     WET  ASSAY  OF  COPPER. 

PAGB 

Advantage  of  this  assay  ;  Modified  Swedish  assay ; 

Preparation  of  the  cupriferous  substance  -  -  17G 
Precipitation  with  iron  -  -  -  -  -  -172 

Correction  for  iron  -  - 175 

Characteristics  of  pure  precipitated  copper  ;  Testing 

the  residue  from  the  solution  of  the  ore  for  copper  176 
Precipitation  with  zinc  free  from  lead  and  arsenic  -  177 

XX.     ELECTROLYTIC  DETERMINATION  OF 
COPPER. 

Basis  of  Classen's  method  for  the  electrolytic  deter- 
mination of  metals 180 

Classen's  method  of  the  determination  of  copper      -  181 

Arrangement  of  the  apparatus  used  illustrated  and 
described  -  182 

Herpin's  method  of  assaying  copper  by  electrolysis, 
illustrated  and  described 183 

XXI.     ASSAY  OF  LEAD  ORES. 

On  what  the  method  of  assaying  lead  ores  depends    185 
Methods  of  assaying  sulphuretted  lead  ores  which 

contain  few  or  no  foreign  sulphides  -  -  -  186 
Preparation  of  black  flux  -  -  -  -  -  187 

Substitute   for  black  flux ;   Cover  of  common   salt 

and  its  object -188 

Assays  without  fluxes  in  iron  vessels  ;  Assay  in  iron 

dishes  --------  ]89 

Assay  in  iron  crucibles       -        -        -        -        -        -190 

Assays  with  fluxes    -        -        -        -        -        .        -  191 

Assay  in  an  iron  crucible  with  black  flux      „  '  -        -  192 
Method  used    in    England,    Germany,   France  and 

Belgium                                                    *        -'       -  193 
Proportions  of  the  charge  in  various  countries           -  194 
Assay  in  a  clay  crucible  with  black  flux  and  iron  ; 
available  for  ores  poor  in  foreign  sulphides,  but 
richer  in  earths 195 


XIV  CONTENTS. 


PAGE 

Upper  Harz  potash  assay  in  clay  crucibles  -  -  198 
Methods  of  assaying  sulphuretted  lead  ores,  which 

contain  many  foreign  sulphides  -  -  -  -  199 

Calcination  assay 200 

Assay  with  sulphuric  acid  .....  203 
Methods  of  assaying  for  sulphuretted  lead  ores, 

which  contain  many  earthy  constituents  -  ^  205 
Methods  of  assaying  oxidized  lead  ores  and  smelting 

products  ;  By  melting  with  reducing  agents  -  206 

By  melting  with  reducing  agents  and  iron  .  -  -  208 

XXII.    ASSAY  OF  LEAD  ORES  BY  HEAT. 

Loss   incurred    in    the  assay ;    Preparation  of  the 

charge  -  -  -  210 
Execution  of  the  assay 211 

XXIII.  ASSAY  OF  LEAD  ORES  BY  A  WET 

PROCESS. 
Preparation  of  the  ore 213 

Constitution  of  sulphate  of  lead       -        -        -        -  214 

XXIV.  GRAVIMETRIC  ANALYSIS  OF  LEAD, 

Method  as  executed  at  Bleiberg  in  Carinthia  -  -  216 
Storer's  method 217 

XXV.    ASSAY  OF  IRON  ORES  BY  HEAT. 

Preparation  of  the  ore  and  mode  of  charging  the 
crucible  -  219 

Smelting  apparatus  used  in  the  iron  works  on  the 
Harz  Mountains 220 

Method  of  obtaining  chemically  pure  iron,  according 
to  Karsten 

Characteristics  of  the  button  of  pure  iron         -        -  223 

XXVI.    FUCHS'S  PROCESS  FOR  IRON  ORES  AND 

IRON. 
Ores  to  which  this  process  cannot  be  applied    -        -  224 


CONTENTS.  XV 

PAGE 

Preparation  of  the  ore ;  Method  of  ascertaining  the 
peroxide  of  iron  in  the  ore  -----  225 

Method  of  finding:  the  whole  amount  of  iron  in  the 
ore  -  - 226 

XXVII.  SWEDISH  ASSAY  OF  IRON  ORES. 

Manner  of  obtaining  the  yield  of  crude  iron  from  the 

ores,  as  well  as  the  approximate  content  of  iron    -  221 
Mode  of  obtaining  the  assay  sample ;  The  aim  in 
executing  the  assay        ------  228 

Berthier's    process   for   the   determination    of   the 
earthy  matter  present    -        -        -        -        -        -  229 

Quantities  of  flux  required  -  -  -•-.'-  230 
The  character  of  the  slag  as  a  test  as  to  whether  the 

correct  proportion  of  earths  has  been  used      -        -  231 
Formation  of  a  slag  recommended  by  Percy;   Suit- 
able fluxes  for  ores  or  metallurgical  products          -  233 
Execution  of  the  dry  assay  of  iron  ores  ;  Preparation 

of  ba^qued  crucibles  -  235 

Crucibles  best  adapted  for  the  assay  -  —  -  236 
Characteristics  of  the  iron  buttons  obtained  -  -  238 
Execution  of  the  iron  assay  in  England ;  Proportions 

of  ore  and  fluxes  used 239 

Reducing  agent  employed  ;  Preparation  of  the  charge  240 
Probable  result  of  the  operation  -  241 

XXVIII.  ASSAY  OP  QUICKSILVER  ORES. 

Composition  of  cinnabar  ;  Analysis  of  a  specimen  of 

cinnabar  from  Japan  by  Klaproth        -        -        -  243 
Distillation  of  quicksilver  -  244 

Fluxes  used  in  the  assay  of  quicksilver  -  245 

Precaution    as    to   the   heat  employed  during   the 

assay      -        -        -        ;        -/•     -        -        -        -  246 
Berthier's    preparatory  process  in   assaying   quick- 
silver                                                                         -  248 
Berthier's  treatment  of  quicksilver '  ore  containing 
arsenic 249 


XVZ  CONTENTS. 

Electrolytic  determination  of  quicksilver,  Escosura's 

process  _  250 

Classen's  process       -        -        -        ...        .  252 

XXIX.    DRY  ASSAY  OF  TIN  ORES. 

What  the  assay  proper  consists  of;  Difficulties 
caused  by  the  behavior  of  stannic  oxide  and  metal- 
lic tin  at  an  elevated  temperature  -  -  253 

German  method  of  assay 255 

Mitchell  s  process ;  Leval's  assay  with  potassium 
cyanide 256 

Winkler's  bronze  assay 258 

XXX.     ASSAY  OF  SULPHURETS  IN  ORES. 
Preparation  of  the  charge  -        -        -  260 

Volumetric  determination  of  sulphur  in  ores  which 

contain    either  sulphur  alone,  or  also  sulphates; 

Weil's  method  261 

Examination  of  sulphur  in  metallic  lead  -         -        -  262 
Determination  of  sulphur  in  pyrites  ...  263 

Bodewig's  method  of  determining  sulphur  in  pyrites  264 

XXXI.     MODE  OF  TESTING  THE  CALORIFIC 

POWER  OF  COAL  AND  OTHER  FUELS. 
Despretz's  experiments  ;  Rumford's  process     -        -  266 
Berthier's  process     -        -        -        --       .        .        .  267 
Examples  of  comparison  in  making  the  assay   -        -  268 
Table  of  analyses  of  different  clays  from  which  the 

most  approved  crucibles  are  made          -        -        -  270 
Table  showing,  in  degrees  of  the   Centigrade  and 
Fahrenheit  thermometers,    the   amount    of   heat 
necessary  to  melt  various  substances  -        -  271 

Table  of  the  troy  weights  used  with  gold  and  silver, 
and  platinum  ,  Table  of  avoirdupois  weights  used 

with  other  metals  -  272 

Index        -        -        -        -  '     -        ...        -  273 


THE 

ASSAYER'S  GUIDE, 


INTRODUCTION 

ASSAYING  is  the  science  which  treats  of  the 
various  methods  of  ascertaining  the  amount 
of  one  or  of  several  ingredients  of  a  chemical 
compound,  such  as  an  ore  or  alloy,  but  is 
solely  intended  for  practical  purposes.  For 
this  reason  one  of  its  main  objects  is  to  be 
able  to  attain  to  a  very  great  accuracy  with 
the  smallest  and  cheapest  means,  and  in 
the  shortest  possible  time.  In  this  it  is  con- 
tradistinguished from  inorganic  analytical 
chemistry,  properly  so  called.  The  aim  of 
the  latter  is  to  ascertain  all  the  different 
composing  elements  of  an  inorganic  com- 
pound, and  also  the  exact  amount  of  each, 

2  17 


18  THE  ASSAYER'S  GUIDE. 

and  for  this  reason  the  chemist  should  never 
be  deterred  by  a  great  waste  of  time  and 
money,  if  an  accurate  result  should  require 
extravagant  means.  As  assaying  is  only  an 
aid  to  technical  operations,  and  these  never 
can  extract  the  whole  amount  of  a  metal  or 
other  component  part  contained  in  a  com- 
position, (be  the  latter  a  natural  or  artificial 
Dne,)  with  true  chemical  precision,  it  is  self- 
evident  that  much  time  and  labour  would 
be  unnecessarily  lost,  if  the  same  attention 
were  devoted  to  it  as  would  be  requisite 
in  an  analysis.  This,  however,  also  shows 
that  it  is  utterly  inadequate  for  purely 
scientific  ends. 

Assaying  was  the  earliest  known  branch 
of  chemistry,  and  in  fact  that  one  which 
afterward,  through  the  medium  of  the 
various  investigations  of  alchemy,  drew 
attention  to  theoretical  chemistry,  and  thus 
founded  that  science. 

The  art  of  assaying  is  so  ancient,  and  it 
has  so  constantly  and  imperceptibly  re- 


INTRODUCTION.  19 

eeived  new  additions  and  perfections,  that 
its  origin  is  entirely  unknown.  Agricola 
of  Saxony,  who  lived  in  the  earliest  half  of 
the  sixteenth  century,  was  the  first  to  col- 
lect the  facts  and  write  on  this  subject. 
(G.  Agricola  de  Ke  Metallica,  libr.  XII. 
Basil,  1546.)  Since  then  the  manifold  dis- 
coveries of  more  enlightened  periods  have 
vastly  enlarged  and  developed  this  branch 
of  study. 

It  is  not  by  any  means  always  necessary 
that  the  same  measures  be  employed  foi 
these  tests  as  are  used  in  the  separation  of 
the  single  constituent  from  the  rest  of  the 
compound  in  large  quantities;  as,  for  in- 
stance, in  the  processes  of  smelting  and 
amalgamation,  although,  if  convenient,  it  it 
very  advisable,  as  it  facilitates  the  metal- 
lurgist in  the  detection  of  the  best  fluxes 
and  admixtures  to  be  added  to  his  peculiar 
ores. 

The  assayer  should  be  guided  in  his 
operations  by  chemistry,  and  the  study  of 


20  THE  ASSAYER'S  GUIDE. 

the  latter,  particularly  as  far  as  regards  the 
principal  and  more  common  substances, 
should  never  be  omitted.  In  other  respects, 
all  that  can  be  recommended  to  one  who 
desires  to  perfect  himself  in  assaying,  is  the 
most  scrupulous  cleanliness,  order,  and  pre- 
cision as  regards  his  assays  and  implements, 
and  the  most  unwearying  adroitness  and 
attention  in  performing  the  manipulations 
required  by  his  science. 


21 


Description  of  the  Implements  and  Utensils 
used  in  the  course  of  Assays  by  Heat 

AMONG  the  articles  necessary  for  an 
assayer's  office,  of  course  the  first  that 
requires  a  description  is  the  furnace.  For 
most  purposes  the  muffle  furnace  suffices, 
and  it  is  the  only  one  used  for  gold,  silver, 
and  copper  ores ;  but  for  iron,  lead,  &c.  we 
require  another,  though  much  simpler  one. 
I  shall  first  describe  the  muffle  furnace, 
(Plate  I.  figs.  1,  2,  and  3.)  The  character- 
istic part,  the  one  from  which  this  furnace 
derives  its  name,  is  the  muffle,  illustrated 
on  the  same  plate,  in  figs.  7  and  8.  Both 
these  diagrams  give  a  perspective  view,  the 
first  a  semilateral,  the  second  one  from  in 
front.  They  can  be  procured  in  most  of 
our  larger  cities,  and  are  manufactured  in 


22  THE  ASSAYER'S  GUIDE. 

great  quantity  in  Hessia,  of  a  very  firm  and 
fire-proof  siliceous  clay,  the  same  material 
as  that  used  for  the  well-known  Hessian 
crucibles,  (Plate  II.  fig  5.)  The  one  from 
which  the  drawing  was  taken  in  Plate  I. 
measures  eight  inches  across  the  bottom 
from  mouth  to  back  outside,  and  four 
inches  down  the  back.  The  holes  opening 
upwards  towards  the  interior  measure  each 
an  inch  and  a  half  lengthways,  but  their 
number  of  course  varies  according  to  the 
size  of  the  muffle,  which  again  should 
depend  on  the  quantity  of  assays  expected 
to  be  performed  at  once.  The  back  and 
the  mouth  of  the  muffle  are  equal  in  size. 

The  muffle  furnace  is  exhibited  from  in 
front  in  fig.  1,  in  a  lateral  section  in  fig.  3. 
and  in  a  transverse  perpendicular  section  in 
fig.  2.  A  scale,  showing  the  proportionate 
dimensions  in  English  feet,  is  attached,  to 
facilitate  the  use  of  the  drawings  in  build- 
ing a  furnace ;  for  though  very  small,  they 
have  been  made  with  much  care,  and,  with 


DESCRIPTION   OF   IMPLEMENTS.  23 

the  little  sketches  attached,  are  fully  capa- 
hle  of  being  employed  to  that  effect.  As 
will  be  seen  from  the  first  figure,  the  line 
A  B  is  seven  feet  long,  while  the  external 
width  of  the  furnace,  C  D,  is  two  feet  nine 
inches.  The  furnace  consists  of  three  chief 
parts,  the  chimney,  i\  in  figs.  2  and  3,  (which 
need  only  be  3i  feet  high  if  it  enters  the 
chief  chimney  of  the  laboratory,  which 
should  then  measure  at  least  9 — 12  feet,) 
the  part  above  C  D,  in  fig.  1,  containing  the 
muffle,  and  the  part  below  that,  the  grate, 
ashes  box,  &c.,  &c.  In  fig.  1  we  see  imme- 
diately below  the  chimney  a  representation 
of  bricks,  (firebricks,  for  all  in  immediate 
contact  with  the  heat  should  be  of  this 
kind  ;  the  external  ones  are  common  burnt 
bricks.)  These,  though  fastened  in  tight, 
are  placed  so  that  they  can  be  taken  out, 
to  put  in  a  new  muffle,  or  'make  other 
repairs  when  necessary.  In  this  brickwork 
we  have  two  openings,  d  and  a.  The 
former  is  only  a  small  aperture,  for  insert- 


24  THE  ASSAYER'S  GUIDE. 

mg  pieces  of  sheet  iron,  upon  which  to  dry 
the  cupels.  It  is,  however,  not  immediately 
necessary,  and,  if  present,  is  always  closed 
with  a  tight  brick  when  the  muffle  is  in  use. 
a  is  the  opening  of  the  muffle,  which  can  be 
closed  by  a  piece  of  fire-proof  brick  repre- 
sented in  fig.  4,  having  an  iron  piece  pro- 
truding on  the  exterior,  with  a  narrow 
opening,  into  which  fits  the  handle  fig.  5, 
which  we  apply  on  removing  it.  To  the 
right  and  a  little  below  the  muffle  is  a 
loose  brick,  6,  to  be  taken  out  whenever  it 
becomes  necessary  to  remove  the  fire-proof 
clay  bar,  o,  which  holds  the  muffle,  (vid.  fig. 
2.)  As  seen  in  fig.  3,  this  bar  as  well  as 
the  three  others  shown  in  the  little  sketch 
affixed  to  fig.  2,  and  of  which  the  centre 
one  is  a  little  the  longest,  are  slightly 
inclined,  thus  elevating  the  back  of  the 
muffle  an  inch  above  the  front,  and  giving  a 
better  circulation  of  heat,  as  should  be  the 
case  where  stone-coal  or  cokes  are  used. 
In  burning  charcoal  it  may  be  horizontal, 


DESCRIPTION    OF   IMPLEMENTS.  25 

although  this  inclination  has  another  ad* 
vantage,  inasmuch  as  it  enables  us  to 
clean  out  the  muffle  easier,  should  a  cupel 
upset,  the  contents  running  forward.  The 
three  fireclay  bars,  sss,  are  loose,  while  o  is 
inlaid  on  one  side,  and  on  the  other  fastened 
in  with  a  loose  piece  of  brick  and  an  iron 
wedge,  which  can  be  removed,  as  already 
remarked,  through  e.  On  inserting  the  bars 
and  muffle,  the  parts  where  they  meet,  and 
where  the  former  touch  the  other  bricks, 
should  be  powdered  over  with  bone-ashes,  to 
prevent  a  possible  adhesion  from  the  intense 
heat.  Small  cracks  in  the  muffle  should 
be  mended  with  coarsely  powdered  burnt 
clay,  p,  in  fig.  2,  is  the  open  space  left  round 
the  muffle  about  an  inch  and  a  half  wide, 
and  into  which  the  opening  d  in  figs.  1  and 
3  leads.  Immediately  below  C  D  we  have 
the  door  b  exhibited  in  all  three  figures 
It  is  for  the  introduction  of  fuel,  and  is  just 
above  the  grate,  x  x,  in  figs.  2  and  3,  which 
consists  of  six  iron  bars  placed  in  the  same 


26  THE  ASSAYER'S  GUIDE. 

inclination  as  the  muffle.  The  door/,  fig  1, 
is  of  iron,  with  an  inside  coating  of  fire-clay, 
an  inch  and  a  quarter  thick,  kept  in  place  by 
iron  rivets,  thus  protecting  the  assayer  from 
the  radiating  heat  of  the  iron,  which  would 
otherwise  soon  be  white-hot.  Below  the 
grate  stretches  the  chamber  q,  in  figs.  2  and 
3,  both  for  draught  and  for  the  cinders, 
The  plane  at  the  bottom  of  this  is  inclined 
like  the  grate  and  muffle,  and  has  the 
opening  c  to  take  out  the  ashes.  To  intro- 
duce a  regular  and  sufficient  quantity  of 
atmospheric  air,  the  channel  k  has  to  be 
constructed,  which  enters  q  at  h,  and  passing 
under  the  floor  of  the  laboratory  opens 
outside  at  i,  fig.  3 :  Z  is  a  small  piece  of 
sheet  iron,  by  pulling  out  or  pushing  in 
which,  we  open  or  close  the  passage  Jc  at 
pleasure,  and  accordingly  as  we  require  a 
great  influx  of  air  or  not,  for  a  high  or  low 
temperature.  The  little  figure  annexed  to 
fig.  1,  shows  the  construction  of  the  little 
opening  and  slide  in  the  lower  door.  It  is 


DESCRIPTION   OF   IMPLEMENTS.  27 

exactly  as  with  a  common  iron  stove,  y 
being  the  hole,  while  the  slide  a  /?  can  be 
closed  over  it  by  means  of  the  handle,  or 
removed,  as  may  be  desirable  for  different 
degrees  of  ventilation.  This  furnace  is  of 
the  kind  proposed  by  Professor  Plattner  for 
the  Freiberg  assay  office  for  the  use  of  stone- 
coal  and  cokes,  and  where  it  has  been 
employed  to  great  advantage,  as  regards 
economy  and  practicability  in  general. 

Having  thus  pretty  minutely  given  a 
description  of  the  muffle  furnace,  as  it  can 
best  be  constructed  when  not  required  to  be 
movable,  I  shall  proceed  to  the  furnace  for 
tests  of  iron  ores,  lead  ores,  &c.,  also  in  a 
shape  not  intended  to  be  moved,  as  repre- 
sented by  a  lateral  section  in  fig.  6,  Plate  I. 
Those  parts  in  immediate  contact  with  the 
heat  should  be  constructed  of  fire-proof 
bricks,  which  ought  to  reach  some  distance 
up  the  chimney.  The  main  body  of  the 
furnace  B  and  A  is  either  square  or  round, 
and  twelve  inches  in  diameter.  The  back 


28  THE  ASSAYER'S  GUIDE. 

is  about  three  feet  nine  inches  high,  while 
the  front  measures  slightly  less,  as  the  top 
has  a  little  slant,  merely  for  convenience  in 
easier  being  able  to  get  at  the  bottom.  A 
is  the  part  where  the  ashes  collect,  with  a 
door  at  H  having  one  or  several  openings, 
as  is  represented  in  the  door  g,  in  fig.  1,  for 
the  sake  of  regulating  the  ventilation.  It 
this  furnace  is  to  be  used  for  iron  assays, 
in  which  case  a  very  intense  heat  is  requi- 
site, a  similar  channel  as  illustrated  in  K, 
fig.  3,  should  be  attached,  the  longer  the 
better,  and,  if  possible,  opening  into  some 
cool  place,  e.  g.  a  cellar,  thus  creating  a 
stronger  current  of  air,  and  consequently  a 
better  ventilation.  Above  A  are  the  bars 
forming  the  grate  FG,  which  ought  to  vary 
in  distance  from  one  another  according  as 
we  use  charcoal  or  stone-coal  and  cokes,  in 
the  former  case  being  closer  to  one  another. 
B  is  the  part  in  which  the  crucibles  are 
placed,  as  well  as  the  fuel,  and  which  has 
one  opening  for  the  introduction  of  the  same 


DESCRIPTION  OF   IMPLEMENTS.  29 

with  the  cover  E,  suspended,  when  open, 
by  a  chain,  but  which  is  shut  when  the 
furnace  is  in  use.  This  cover  is  commonly 
ol  iron,  covered  with  fireproof  clay. 

C  is  the  channel  leading  off  to  the 
chimney  D,  which  may  vary  in  width  from 
one  half  to  one  quarter  the  width  of  B. 
For  assays  of  lead  and  copper  it  is  not 
necessary  to  have  the  chimney  very  high, 
as  no  very  severe  draught  is  required ;  but 
for  iron  assays  it  should  be  about  thirty  feet. 
In  the  assay  office  in  Clausthal  it  measures 
forty-eight  feet.  In  this  case,  of  course,  if 
there  is  also  a  muffle  furnace  on  the  same 
hearth,  it  is  best  to  conduct  the  chimneys 
of  both  into  one  large  one.  On  placing 
the  crucibles  in  this  furnace — twelve  have 
room  in  it  at  once — a  piece  of  firebrick,  K 
in  the  drawing,  is  first  placed  on  the  grate, 
which,  to  avoid  adhesion  of  the  crucibles, 
may  be  powdered  with  bone-ashes.  This 
brick  is  employed  to  have  the  crucibles 
more  in  the  focus  of  heat,  by  elevating 


30  THE  ASSAYER'S  GUIDE. 

them  above  the  coal  around  it,  and  also — 
clay  being  a  bad  conductor — to  keep  them 
from  immediate  contact  with  the  cold  blast 
The  fuel  should  never  be  heaped  above  1, 
the  mouth  of  the  channel  C,  and  large  coals 
should  be  placed  below,  to  keep  the  grate 
from  choking.  If  several  crucibles  are  used 
at  once,  they  ought  to  stand  sufficiently 
upart  to  admit  coals  between  them,  as  they 
otherwise  might  melt  partially  in  the  course 
of  the  process,  and  form  one  compact  mass. 
On  the  foregoing  pages  I  have  furnished 
Inscriptions  and  measurements  of  furnaces, 
which,  as  I  have  already  remarked,  though 
easily  constructed,  are  not  portable ;  and  it 
is  proper  that,  before  closing  this  chapter,  I 
should  devote  a  few  lines  to  the  mention  of 
those,  which,  from  their  being  movable,  and 
thus  obviating  the  difficulty  and  incon- 
venience of  constructing  one,  might,  in 
many  cases,  be  preferred,  although  their 
smaller  dimensions,  as  a  matter  of  course, 
make  it  more  difficult  to  perform  good 


DESCRIPTION   OF   IMPLEMENTS.  31 

assays,  and  impossible  to  attend  to  many  at 
a  time.  Among  these  we  have  both  muffle 
furnaces  and  wind  furnaces  such  as  last  de- 
scribed. Many  forms  have  been  manufac- 
tured, and  it  is  not  necessary  to  enter  into 
detailed  descriptions.  They  can  generally 
be  procured  at  all  larger  stores  of  chemical 
apparatus.  The  Battersea  furnace  is  of 
fireclay  made  in  sections  and  bound  with 
iron  bands.  Brocoris  portable  assay  fur- 
nace consists  of  a  sheet-iron  frame  27  inches 
high  and  14  inches  square,  lined  with  fire- 
brick, the  interior  being  smooth  and  straight 
from  top  to  bottom.  The  cover  is  ridged 
to  lessen  the  danger  from  cracking.  The 
muffle  door  is  cast  iron  and  is  fitted  with  a 
circular  opening  filled  with  mica,  that  the 
operations  going  on  within  the  muffle  may 
be  seen  when  the  door  is  closed.  After 
having  thus  given  a  description  of  the  fur- 
naces used  in  the  course  of  the  experiments 
elucidated  in  the  following  pages,  the  reader's 
attention  is  called  to  other  instruments  usecj 


32 

in  the  assays  of  ores.  Among  these,  probably 
the  balance  will  appear  most  conspicuous. 
There  ought  to  be  two  in  use,  one  very  ac- 
curate, the  other  less  so,  for  more  common 
purposes,  as  weighing  off  the  ingredients  or 
admixtures,  such  as  pure  lead,  borax,  &c. 
The  other  one  should  be  made  with  great 
care,  and  only  used  to  weigh  off  the  small 
buttons  of  gold  and  silver  procured.  Before 
weighing  the  balance  must  be  tested  as  to 
its  equilibrium.  The  substance  to  be  weighed 
should  be  cold,  and  must  not  be  placed 
directly  upon  the  scale  pan,  but  upon  suitable 
smaller  pans,  watch  glasses,  etc. ;  hygro- 
scopic substances  in  closed  tubes.  The  bal- 
ance beam  should  be  raised  from  the  knife 
every  time  before  a  weight  is  put  into  or 
removed  from  the  pan.  The  weights  must 
not  be  put  in  the  pan  at  random,  but  system- 
atically, this  being  the  only  way  of  saving 
time.  The  highest  probable  weight  should 
be  added  first,  then  the  next  lowest,  and  so 
on  until  the  equilibrium  has  been  established. 


DESCRIPTION   OF   IMPLEMENTS.  33 

The  pans  should  then  be  changed  in  order 
to  test  the  correctness  of  the  weight.  Per- 
fect equilibrium  of  the  balance  is,  however, 
not  absolutely  essential,  as  a  correct  weigh- 
ing may  be  obtained  by  placing  the  substarice 
to  be  weighed  in  one  pan  and  in  the  other 
pan  any  convenient  material  as  a  make- 
weight, such  as  tin-foil,  shot,  granules  of 
lead,  etc.,  until  equilibrium  is  established 
The  balance  is  then  raised,  the  weighed 
substance  is  removed  from  the  pan,  and 
sufficient  weights  to  counterpoise  the  bal- 
ance are  put  in  its  place.  The  sum  of  these 
will  give  the  correct  weight  of  the  sample. 
It  is  a  good  plan  to  always  place  the 
weights  in  one  pan  (the  right-hand  one) 
and  whatever  is  to  be  weighed  always  in 
the  other. 

In  the  choice  of  a  scale  for  weighing 
larger  quantities  (fluxes,  etc.)  much  latitude 
may  be  allowed.  It  need  not  be  very  deli- 
cate ;  a  grocer's  scale  will  do. 

We  must  now  cast  a  rapid  glance  at  the 

3 


34  THE  ASSAYER'S  GUIDE. 

smaller  and  less  costly  utensils,  but  all 
of  which  are  necessary  for  the  accomplish- 
ment of  the  operations  to  be  performed  a& 
directed  in  the  following  pages.  I  allude 
to  the  crucibles,  cupels  or  cups,  and  tongs, 
&c.,  illustrated  in  Plate  II.  The  former, 
figs.  1,  2,  3,  4  and  5,  are  all  of  their  natu- 
ral size  in  the  drawings.  Figs.  1,  3,  and  4, 
should  be  made  from  accurate  descriptions 
by  a  potter,  of  a  pure  clay,  containing  as 
little  silica  mechanically  combined  as  pos- 
sible, since  its  presence  prevents  the  ves- 
sels from  being  sufficiently  porous  to  allow 
the  oxidizing  metals  to  enter,  which  would, 
as  will  hereafter  be  seen,  become  a  great 
drawback  to  the  assay.  Some  hundreds 
must  always  be  kept  on  hand,  for  they  can 
only  be  used  once,  as  the  lead,  almost  al- 
ways present,  glazes  them  immediately. 

Fig.  1  represents  a  cupel  used  in  the 
operation  technically  termed  cupdlation  of 
the  gold  and  silver  ores :  a  shows  it  froiu 
above,  b  from  the  side.  The  concave  inner 


DESCRIPTION   OP  IMPLEMENTS.  35 

surface  should  not  be  too  shallow,  thus 
letting  the  contents  run  over ;  nor,  on  the 
other  hand,  too  deep,  in  which  case  too 
small  a  surface  would  be  exposed  to  the 
oxidizing  power  of  the  heat.  The  line 
given  in  b  shows  the  proper  inclination 
within. 

Fig.  2  is  a  truncated  cone,  with  a  very 
slightly  concave  surface  at  the  wider  ex- 
tremity or  top.  It  is  made  in  great  part  of 
bone-ashes,  being  among  the  most  porous 
substances  that  can  stand  a  high  tempera- 
ture. I  give  here  a  recipe  for  their  pre- 
paration, furnished  me  by  Mr.  Fritzsche. 
It  shows  the  relative  quantity  of  the  ingre- 
dients as  used  for  these  cupels  at  his  office, 
where  they  are  made  by  the  laboratory 
servant  in  wooden  moulds,  using  a  rod, 
shaped  like  a  pestle,  to  make  the  hollow 
at  the  top.  The  mass  consists  of  4  parts 
of  wood-ashes  previously  freed  of  the  pot- 
ash by  filtration,  1  part  of  lime,  and  1  part 
of  bone-ash. 


36  THE  ASSAYER'S  GUIDE. 

Fig.  3  shows  a  flat,  shallow  crucible 
made  of  the  same  pure  clay  as  that  repre- 
sented in  fig.  1 :  a  is  the  cup  as  seen  from 
above,  while  b  gives  a  lateral  view,  show- 
ing also  the  curve  of  the  inner  surface. 
This  vessel  is  used  in  the  assay  of  copper, 
as  well  as  fig.  4.  Fig.  3  is  termed  in  Ger- 
man " Kupfer  Garscherbe"  from  the  fact 
that  "with"  its  use  the  copper  assay  is 
finished. 

Fig.  4  is  a  high  crucible,  as  mentioned 
above,  used  for  copper  and  lead.  It  is 
made  of  the  same  material  as  the  former. 
The  reason  of  its  having  so  great  a  height 
compared  with  its  width,  and  otherwise  so 
peculiar  a  form,  is  to  concentrate  all  the 
heat  round  about  the  bottom  of  the  in- 
terior. In  some  places,  in  lieu  of  better, 
the  Hessian  crucible  (fig.  5)  is  used;  but 
No.  4  is  much  better  adapted,  from  the 
height  of  the  foot-piece,  which  also  protects 
the  contents  from  the  cooling  influence  of 
the  iron  bars  on  which  they  are  placed. 


DESCRIPTION   OF   IMPLEMENTS.  37 

and  from  a  too  direct  contact  with  the  cold 
draught.  Some  assay ers  use  an  extra 
cover  for  this  crucible,  a  very  superfluous 
addition,  since  the  bottoms  of  the  old  cru- 
cibles answer  admirably  as  covers  to  the 
new.  As  mentioned  before,  these  also  are 
useless  after  once  having  been  employed, 
and  before  throwing  them  away  it  is  there- 
fore well  first  to  break  off  the  feet. 

Fig.  5  gives  a  drawing  of  a  Hessian  cru- 
cible, which  is  used  chiefly  in  the  assays  of 
iron  ores.  These  are  imported  into  the 
United  States,  and  can  be  procured  in  al- 
most every  crockery  store.  Their  dimen- 
sions are  very  different,  and  so  contrived 
that  one  fits  into  the  next  in  size,  being 
in  sets  of  about  a  dozen.  They  are  com- 
monly triangular  above,  and  round  below, 
as  shown  in  the  figure;  but  sometimes  they 
are  made  round  above  and  below,  and 
where  these  can  be  had,  they  should  be 
preferred.  If  they  cannot  be  procured, 
similar  crucibles  of  pure  clay  may  be  sub- 


38  THE  ASSAYER'S  GUIDE. 

atituted,  and  in  fact  they  are  sometimes 
considered  preferable.  The  latter  are  then 
commonly  made  with  a  foot-piece,  some- 
what as  in  fig.  4,  though  not  quite  so 
strongly  separated  from  the  main  bulk  of 
the  vessel.  These  or  the  Hessian  crucibles, 
as  will  be  seen  hereafter,  should  be  kept 
constantly  on  hand  thickly  coated  with 
charcoal.  They  are  prepared  in  this  man- 
ner. Charcoal  of  any  oak-wood,  except 
red-oak,  which  contains  much  oxide  of 
iron,  is  the  best  on  account  of  its  density. 
It  should  be  pulverized  with  the  utmost  care, 
since  a  coarse  powder  will  never  furnish  a 
consistent  mass.  To  this  we  carefully  add 
water  until  we  procure  a  tough  paste  or 
dough,  and  with  this  fill  the  crucible  very 
tightly,  always  ramming  down  every  new 
portion  introduced,  with  a  pestle  or  piece 
of  wood.  When  the  whole  interior  is  filled 
up,  we  cut  out  a  hole  in  the  middle  with 
a  penknife,  leaving  a  margin  of  about  half 


DESCRIPTION   OF   IMPLEMENTS.  39 

an  inch  at  least,  below  and  all  round.     (See 
Assay  of  Iron  Ores.) 

Fig.  6  furnishes  a  sketch  of  an  imple- 
ment, which,  though  not  immediately  ne- 
cessary, will  be  found  extremely  useful, 
inasmuch  as  it  tends  to  keep  up  order 
and  accuracy,  great  requisites  for  an  able 
assayer.  As  will  be  seen  from  the  dif- 
ferent views  a  and  &,  it  consists  simply  of 
a  piece  of  sheet-iron,  having  a  wooden 
handle  and  several  semi-circular  cavities, 
the  number  of  which  may  vary  according 
to  the  number  of  assays  expected  to  be 
performed  at  once.  If  a  large  muffle  is 
used  in  the  furnace,  it  is  well  also  to  have 
this  large;  and,  in  fact,  I  would  suggest 
having  the  number  of  holes  in  each  row 
equal  to  the  number  of  cupels,  of  the  sort 
illustrated  in  fig.  1,  that  can,  without  col- 
lision, be  placed  across  the  muffle  from  side 
to  side.  (See  Silver  and  Gold  Ores.)  This 
pan,  or  whatever  we  may  otherwise  term 
it,  is  used  to  cool  the  buttons  of  metal  and 


40  THE   ASSAYEft'S   GUIDE. 

their   surrounding   slag   after  having   oxi 
dized  part  of  the  lead,  &c.,  and  separated 
the  gangue-rock,  as  is  the  case  with  silver 
and  gold  (q.  v.)     The  holes  should  be  li 
inch  wide  and  i  inch  deep: 

Figs.  7  and  8  represent  two  different 
kinds  of  tongs.  Fig.  7  is  only  shown  in  a 
lateral  view,  since  its  characteristics  are 
thus  exhibited,  while  fig.  8  is  sketched 
from  above.  They  are  both  very  necessary 
in  the  progress  of  our  investigations.  The 
first  is  shaped  like  common  fire-tongs,  only 
that  the  ends,  instead  of  widening  into  a 
flat  circular  lobe,  are  bent  downward  like 
a  poker,  thus  enabling  us  to  handle  the 
crucibles  with  great  care.  The  .second 
tongs  has  each  piece  ending  in  a  semi- 
circle, the  diameter  of  which  circle,  when, 
united,  should  be  so  that  it  may  exactly 
embrace  the  lower  part  of  fig.  1.  It  is 
used  to  place  those  cupels  into  the  muffle, 
as  we  are  thereby  prevented  from  touch- 
ing the  contents.  In  using  this  latter  in- 


DESCRIPTION    OF    IMPLEMENTS.  41 

strument  great  caution  should  be  taken  not 
to  upset  the  cupels.  Let  me  first  remark, 
that  on  introducing  the  cupels  into  the 
muffle,  we  always  commence  with  No.  1, 
i.  e.  first  assay  on  hand,  behind  on  the  left. 
It  may  seem  a  very  superfluous  precaution 
to  dwell  thus  long  on  so  simple  a  manipu- 
lation as  the  one  I  am  now  describing; 
but  I  know  from  experience,  how  many 
failures  carelessness  in  this  procedure  oc- 
casions to  the  uninitiated.  Let  us  now 
suppose,  that  we  have  the  crucible,  fig.  1, 
filled  with  the  powdered  mineral  to  be 
tested,  and  the  other  additions,  such  as 
lead  or  borax.  Grasping  the  cupel  firmly 
at  the  bottom,  we  lift  it  up  high,  so  that, 
when  pushed  into  the  mouth  of  the  muffle, 
it  is  a  good  deal  above  its  floor,  and  cannot 
knock  against  it.  As  soon  as  it  is  within 
the  muffle,  without  leaving  hold  of  it,  and 
keeping  it  up  high,  we  hold  the  side  of  the 
tongs  up  against  the  side  of  the  muffle  to 
steady  them,  then  run  them  along  quietly 


42  THE  ASSAYBR'B  QUID*. 

though  not  too  slowly,  for  that  only  cause§ 
the  hand  to  tremble,  until  the  crucible  is 
just  above  the  spot  where  we  intend  to 
place  it,  (when  once  down  it  should  never 
be  moved,)  and  then  slowly  lower  it,  not 
letting  go  till  it  stands  secure. 

These  tongs  should  be  made  'light 
enough  conveniently  to  handle  them  with 
one  hand.  The  handles  are  made  of  some 
good  firm  wood,  though  No.  8  is  general!}7 
held  lower  down  than  the  handles,  and,  I 
may  add,  never  so  that  the  end  of  the 
tongs,  the  handle,  passes  under  the  arm. 
but  exactly  as  the  savages  hold  their  darts 
when  about  to  hurl  them.  It  may  seem 
awkward  at  first,  and  yet  I  know  many 
accidents,  as  regards  the  assays,  having 
occurred  from  not  attending  to  it.  The 
length  of  the  tongs  ought  to  be  about  three 
feet.  It  may  be  well  to  supply  oneself 
with  a  third  pair,  with  straight  and  rather 
pointed  ends. 


DESCRIPTION   OF   IMPLEMENTS.  43 

For  sifting  brass  or  copper  wire  sieves  are 
generally  used  in  preference  to  hair  sieves, 
since  the  latter  deteriorate.  Such  sieves  are 
furnished  of  various  diameters  (6  to  8  inches 
is  a  good  size).  For  less  valuable  ores  the 
sieves  have  about  35  to  50  meshes  to  the 
square  inch  and  for  more  valuable  ores 
from  70  to  80.  The  box-sieve  of  tinned 
iron  consisting  of  a  sieve,  of  about  80  to 
100  meshes  to  the  linear  inch,  with  tightly 
fitting  bottom  to  catch  all  the  sifted  ma- 
terial, and  cover  to  retain  the  dust,  is  a 
valuable  implement.  Brittle  substances 
will  pass  through  the  sieves  without  diffi- 
culty, but  those  with  malleable  admixtures 
will  leave  behind  a  flattened  residue,  as,  for 
example,  ores  carrying  native  silver  and 
copper,  silver  glance,  granules  of  lead  in 
slag  and  thin  matt,  sweepings  containing 
gold  and  silver,  etc.  In  case  hard  gangue 
(quartz)  is  to  be  sifted,  the  fine  mass  which 
has  passed  through  the  sieve  is  several  times 
rubbed  together  with  the  coarse  residue  re- 


44 


THE   ASSAYER7S   GUIDE. 


maining  upon  the  sieve,  until  everything 
has  passed  through.  The  residue  of  soft 
gangue  is  weighed  and  at  once  assayed  by 
itself,  and  the  fine  siftings  separately  also, 
after  they  have  been  mixed  upon  glazed 


FIG.  A. 

paper  and  several  times  passed  through  a 
coarse  sieve.  The  entire  yield  is  then  cal- 
culated by  adding  the  product  of  both  to- 
gether. 

Gas  assay -furnaces.    These  furnaces  have 


DESCRIPTION   OF   IMPLEMENTS.  45 

been  known  and  used  for  some  time.  The 
source  of  heat  is  our  common  illuminating 
gas.  Fig.  A  shows  Fletcher's  direct-draft 
crucible  furnace.  It  consists  of  a  fire-clay 
body  held  together  by  sheet-iron  bands. 
The  heat  and  flame  pass  through  the  body 
of  the  furnace  to  the  chimney.  It  can  be 
used  either  for  scorifying  or  cupelling,  and 
by  removing  the  top  cover  the  heat  has  full 
play  upon  a  roasting  dish  placed  upon  it. 

Fig.  B  gives  a  representation  of  a  group 
of  gas  furnaces  designed  by  Walter  Lee 
Brown  and  described  by  him  as  a  complete 
gas-assaying  plant.* 

Its  duty  is  to  do  roasting,  crucible  fusion, 
scorification  and  cupellation.  The  furnace 
at  the  left  is  for  roasting  sulphurets  or  other 
ores  for  experimentation  or  actual  work. 
It  is  what  is  known  as  a  Fletcher  No.  163, 
the  same  as  shown  in  fig.  A.  The  heat  and 
flame  pass  from  the  burner  through  the 

*  Transactions  of  'the  American  Institute  of  Mining 
Engineers,  1884. 


4(5  THE  ASSAYER'S  GUIDE. 

furnace,  and  out  and  up  the  chimney  pipe. 


FIG.  B. 
The  funnel-shaped  pipe  over  the  cover  is  to 


DESCRIPTION   OF   IMPLEMENTS.  47 

catch  and  draw  the  fumes  up  the  chimney. 
When  the  burner  is  lighted  a  powerful 
draught  ensues,  carrying  all  odors  and  fumes 
at  once  away.  Both  the  pipe  and  hood  are 
provided  with  dampers,  controlled  by  small 
weights.  The  burner  is  connected  to  the 
gas-tap  by  stout  \  inch  rubber  tubing.  A 
cast-iron  tripod  supports  one  end  of  the 
furnace  and  keeps  everything  firm. 

Next  in  regular  order  (supposing  a  sul- 
phuret  ore  to  be  under  treatment)  is  the 
middle  furnace  for  crucible  fusions.  This, 
likewise,  consists  of  a  furnace  and  burner. 
The  latter  is  a  Fletcher  No.  15,  of  the  same 
construction,  however,  as  the  No.  16.  The 
furnace  proper  is  made  in  five  parts,  the 
central  section  (a  cylinder  of  fireclay),  the 
bed-plate  upon  which  it  rests  and  which 
has  an  opening  for  the  flame  to  pass  through  ; 
the  cover  (with  handle  attached),  which  also 
has  an  opening  filled  by  a  plug — all  of  fire- 
clay ;  and  finally  a  plumbago  lining.  The 


48  THE  ASSAYER'S  GUIDE. 

rubber  tube  chimney  connections  and  darn  per 
are  like  those  of  the  other  furnace. 

Finally  at  the  right  is  shown  the  furnace 
for  scorification  and  cupellation,  which  the 
author  designates  the  "Monitor."  Fig.  C 


FIG.  C. 


shows  it  enlarged  and  uncovered.  Its  form 
is  almost  that  of  a  reverberatory  furnace, 
the  movable  bricks,  when  in  place,  being 
the  roof.  Looking  at  it  from  another  point 
of  view,  it  may  be  considered  as  a  muffle 


DESCRIPTION  OF  IMPLEMENTS.  49 

with  the  flame  as  well  as  the  heat  inside. 
Its  exterior  dimensions  are  as  follows : 
length  20  inches;  width  7  inches;  and 
depth  5£  inches.  In  the  interior,  upon  the 
bottom,  are  four  little  wedge-shaped  bridges 
of  fire-clay  which  are  movable;  and  upon 
these  rests  a  false  bottom  or  floor,  also 
movable.  The  latter  corresponds  to  the 
muffle-bottom  of  an  ordinary  furnace,  and 
upon  it  is  done  all  the  work.  It  is  3i 
inches  wide  by  7i  inches  long  and  i  inch 
thick,  and  has  a  shoulder  or  bench  running 
across  its  entire  width  on  the  end  nearest 
the  burner.  The  covering  bricks,  four  in 
number,  are  each  7  inches  long  by  21  inches 
wide  and  II  inches  high,  each  with  a  slotted 
bridge  for  convenient  handling.  The  con- 
nections are  similar  to  those  of  the  first 
mentioned  furnaces. 

The  3-inch  stove-pipes  of  all  three  fur- 
naces are  fitted  into  one  long,  horizontal 
pipe,  which  fits  snugly  into  the  chimney. 
The  bench  or  table  upon  which  rest  the 


50  THE  ASSAYER'S  GUIDE. 

furnaces  described  is  made  of  pine,  well 
seasoned  and  firmly  joined,  to  resist  as 
much  as  possible  the  warping  influence  of 
heat,  and  to  support  the  weight  of  the  fur- 
naces and  table-tiles.  In  dimensions  (not 
figuring  on  the'  top,  which  overlaps  1  inch 
all  round)  it  is  4  feet  6  inches  long,  1  foot 
7  inches  wide,  and  2  feet  1  inch  high,  plus 
the  thickness  of  the  top,  which  is  II  inches. 
A  double  coat  of  shellac  varnish  is  its  sole 
ornamentation.  To  the  sides  and  ends  of 
the  table-top  are  firmly  screwed  four  strips 
of  band  iron  of  24  inches  width  and  1  inch 
thickness,  and  of  such  lengths  as  to  alter- 
nately overlap  at  the  angles,  making  smooth 
joints.  The  top  of  this  sort  of  wall  is  I 
inch  above  the  bed  of  the  table.  Upon  the 
latter  are  114  fire-clay  tiles,  or,  rathei; 
clamps,  such  as  are  used  to  join  house  tiles 
and  having  the  shape  of  the  letter  "  E  " 
less  the  middle  projection.  Their  average 
size  is  34  inches  by  3  inches  across  and  II 
inches  high.  They  are  so  arranged  on  the 


DESCRIPTION   OF   IMPLEMENTS.  51 

table  as  to  leave  a  series  of  six  air  tubes  or 
chambers  running  its  entire  length.  The 
spaces  between  the  tiles  are  filled  with  a 
mixture  of  plaster  of  Paris  and  Venetian 
red  rubbed  up  with  water.  The  latter 
color  is  also  used  for  the  tiles  themselves, 
and  somewhat  on  the  fire-clay  portions  of 
the  furnaces. 

A  t-inch  bore  gas-pipe,  with  proper  taps 
and  nozzles,  is  screwed  to  the  front  of  the 
table. 

The  manner  of  operating  the  furnaces  is 
simple.  As  regards  the  roasting-furnace,  it 
is  necessary  merely  to  shut  off  the  dampers 
of  the  other  furnaces,  turn  on  and  light  the 
gas  and  regulate  the  heat  to  suit  the  par- 
ticular ore.  The  control  of  the  mixture  of 
gas  and  air  is  effected  by  means  of  the 
milled  handle  at  the  burner.  In  using  the 
crucible-furnace,  remove  cover,  turn  gas  on 
full  at  tap,  light  and  regulate  by  milled 
handle.  Crucibles  containing  charges  that 
are  to  be  heated  gradually  can  be  placed  in 


52 

the  furnace  as  soon  as  lighted  ;  others  after 
the  lapse  of  a  few  moments  to  allow  the 
furnace  to  become  thoroughly  heated, 
Placing  the  charges  in  cold,  good  fusions  of 
refractory  ores  have  been  made  in  twenty- 
five  minutes  from  time  of  lighting.  The  fur- 
nace will  take  crucibles  in  size  up  to  Bat- 
tersea  "S"  (4i  inches  across  by  5  inches 
deep). 

To  manage  the  "  Monitor,"  remove  the 
covering  bricks,  open  the  .damper  and  shut 
those  of  the  other  furnaces,  turn  back  the 
milled  handle  at  the  gas-entrance  to  the 
burner  so  as  to  allow  a  full  flow  of  gas, 
turn  gas  on  full  at  tap,  light  and  put  back 
the  bricks  into  place.  In  from  twelve  to 
twenty  minutes,  the  interior  will  be  hot 
enough  for  work.  The  bricks  are  then 
again  removed,  the  charged  scorifiers  are 
placed  on  the  false  floor,  the  bricks  are  re- 
placed, and  the  excess  of  gas  is  turned  off 
at  the  burner.  When  the  charges  have 
melted,  slide  the  bricks  aside  more  or  less 


DESCRIPTION   UF   IMPLEMENTS.  53 

— principally  those  nearest  the  burner — to 
admit  air  for  oxidation.  In  cupellation,  the 
gas  is  turned  down  more  than  in  scorifica- 
tion. 

The  time  of  performing  either  scorifica- 
tion  or  cupellation  varies  according  to  the 
nature  of  the  ore,  charge,  size  of  button, 
etc.,  but  is  about  the  same  as  that  occupied 
in  the  use  of  a  coke  furnace.  The  con- 
sumption of  gas  is  not  far  from  thirty  cubic 
feet  per  hour.  It  is  not  intended  or  claimed 
that  this  furnace  can  take  the  place  of  one 
required  to  be  run  from  ten  to  twelve  hours 
per  day ;  for  that,  of  course,  solid  fuel  will 
be  cheaper.  But  for  short  runs  of  from 
one  to  say  four  hours,  it  is  economical,  as 
are  also  the  others  here  described.  The 
complete  plant,  as  illustrated,  costs  about 
$75.00.  The  furnaces  are  manufactured 
by  the  Buffalo  Dental  Manufacturing  Com- 
pany, of  Buffalo,  New  York. 


II. 

Re-agents   Used  in  Assaying. 

Re- agents  for  dry  assays.  According  to 
their  action  they  may  be  divided  into : — 

1.  Reducing  agents.  Wood  charcoal,  in 
the  form  of  powder,  or  of  small  pieces. 
One  part  of  ordinary  charcoal  will  reduce 
from  22  to  nearly  32  parts  of  metallic  lead 
from  litharge,  according  to  the  purity  of  the 
charcoal.  When  employed  in  the  roasting 
of  antimonial  and  arsenical  gold  and  silver 
ores,  charcoal  exercises  a  desulphurizing 
action. 

Powdered  coke,  anthracite  and  graphite 
may  also  be  used  instead'of  powdered  char- 
coal, but  they  are  less  combustible.  Argol 
(crude  bitartrate  of  potash)  yields  consid- 
erable carbon  on  becoming  carbonized,  and 
in  consequence  exerts  a  vigorous  reducing 


RE-AGENTS   USED   IN   ASSAYING.  55 

effect,  but  causes  refractoriness.  For  this 
reason  its  content  of  carbon  is  reduced,  if 
necessary,  by  mixing  it  in  different  pro- 
portions with  saltpetre.  The  mixture  is 
poured  into  a  red-hot  crucible,  placed 
under  a  well-drawing  chimney.  The  mix- 
ture deflagrates  and  emits  empyreumatic 
odors,  and  a  partial  oxidation  of  the  carbon 
taking  place,  a  mixture  of  potassium  car- 
bonate and  carbon  is  formed.  This  is 
known  as  black  flux.  For  vigorous  reduction 
it  is  made  from  3  parts  argol  and  1  salt- 
petre; for  less  vigorous,  either  2i  and  1, 
or  2  and  1  parts  respectively.  White  flux 
consists  of  1  to  2  parts  saltpetre  and  1 
part  argol;  gray  flux  of  3  parts  argol 
and  2  saltpetre.  On  account  of  the  hygro- 
scopic properties  of  black  flux,  a  mixture 
of  potassium  carbonate  or  of  bicarbonate 
of  soda  and  flour  is  used  in  preference,  it 
being  also  cheaper.  Usually  20  to  25  per 
cent,  of  wheat  flour  is  taken,  but  for 
more  vigorous  reductions,  30  to  35  per 


56  THE  ASSAYER'S  GUIDE. 

cent.,  and  even  as  much  as  50  per 
cent. 

Potassium  cyanide  is  an  energetic  reduc- 
ing (as  well  as  desulphurizing)  agent.  It 
being  very  poisonous,  great  care  should  be 
exercised  in  handling  it. 

Potassium  ferrocyanide  yields,  on  heating, 
a  mixture  of  iron  carbide,  ferrous  and 
ferric  oxides,  free  carbon,  and  a  small 
quantity  of  potassium  cyanide.  It  exer- 
cises also  a  vigorous  desulphurizing  action. 

The  following  list  of  the  reducing  powers 
of  various  reducing  agents  will  be  found 
very  useful.  The  values  are  approximate 
only,  but  for  air  practical  assaying  they  are 
sufficiently  near. 

will  reduce  parts 
1  part  of  of  metallic  lead. 

Ordinary  wood  charcoal,  22  to  30 

Powdered  coke,  24 

Powdered  hard  coal,  25 

Powdered  soft  coal,  22 

Wheat  flour,  15 

Cornstarch,  11  £  to  13 

Laundry  starch,  11 J  to  13 


RE-AGENTS   USED   IN   ASSAYING.  57 

will  reduce  parts 
1  part  of  of  metallic  lead. 

Pulverized  white  sugar,  14 J 

Pulverized  gum  arabic,  1 1 

Crude  argol,  5£  to  8J 

Cream  of  tartar,  4£  to  6£ 

2.  Oxidizing  agents.  Saltpetre.  Ordi- 
nary saltpetre  of  commerce  is  used.  It 
should,  however,  be  as  free  as  possible  from 
sulphates.  Pulverize  finely,  and  keep  dry. 

Litharge  (plumbic  monoxide,  yellow  oxide 
of  lead)  exerts  an  oxidizing  effect  upon 
metals  and  metallic  sulphides,  as  well  as 
upon  organic  substances.  It  should  be  dry, 
and  free  from  any  considerable  amount  of 
red  oxide  of  lead,  as  this  causes  oxidation 
.of  silver  and  consequent  loss.  When  the 
litharge  contains  silver,  white  lead  not 
adulterated  with  heavy  spar  may  be  sub- 
stituted for  it.  Litharge  entirely  free  from 
silver  may  be  prepared  by  oxidizing  the 
purest  Pattison  or  Villach  lead  by  cupella- 
tion,  or  bringing  such  lead,  after  it  has  been 
granulated  into  fused  saltpetre;  or  by 


58 

gradually  scattering  powdered  charcoal 
upon  litharge  fused  in  a  refractory  crucible, 
whereby  some  lead  will  be  reduced  which, 
in  subsiding,  withdraws  the  silver  from  the 
litharge. 

3.  Solvent  agents,  a.  Acid;  such  as 
silica  and  glass.  Silica  is  best  used  in  the 
form  of  pulverized  silica,  since  it  is  then  in 
a  very  fine  state  of  division  suitable  for 
intimate  mixture  with  ores  and  fluxes.  It 
should  be  perfectly  dry. 

Borax-glass.  This  is  produced  by  fusing 
borax  in  a  clay  crucible,  and  then  pouring 
it  upon  a  bright  metallic  surface.  It  is 
more  fusible  than  glass,  and  the  boric  acid 
forms  combinations  with  nearly  all  the 
bases  as  well  as  with  silicic  acid. 

Salt  of  phosphorus  (sodium-ammonium- 
liydrogen  phosphate)  or  microcosmic  salt. 
In  the  anhydrous  state  it  is  a  more  ener- 
getic solvent  agent  than  borax. 

Clay,  such  as  kaolin.  Most  varieties  of 
clay  contain  over  50  per  cent,  of  silica. 


BE- AGENTS    USED   IN  ASSAYING.  59 

b.  Basic.  Potassium  carbonate.  Ordi- 
nary carbonate  of  potash.  It  should  be 
ground  to  a  fine  powder  and  kept  from  the 
air,  as  otherwise  it  would  rapidly  absorb 
moisture. 

Sodium  carbonate  (bicarbonate  of  soda) 
acts  somewhat  less  energetically  than  po- 
tassium carbonate,  and  consequently  a  larger 
quantity  of  it  must  be  used.  It  is  less 
deliquescent,  more  fusible  and  cheaper.  A 
mixture  of  13  parts  of  dry  potassium  car- 
bonate and  10  of  calcined  bicarbonate  of 
soda  furnishes  a  very  readily  fusible  flux. 

Caustic  alkalies  act  more  energetically 
than  carbonates,  but  exert  a  very  injurious 
effect  upon  the  crucibles. 

Calcium  carbonate,  in  the  form  of  chalk 
(or  calcite),  may  be  used  for  smelting  oper- 
ations at  higher  temperatures  (for  instance, 
in  assays  of  iron) . 

Fluor-spar  is  more  readily  fusible  than 
calcium  carbonate,  and  is  especially  effec- 
tive for  removing  silica.  It  readily  fuses 


60  THE  ASSAYEK'S  GUIDE. 

down  with  calcium  phosphate,  heavy  spar 
and  gypsum. 

Lead  oxide  (litharge,  minium,  white  lead) 
readily  fuses  with  silica,  the  alkalies,  and 
most  of  the  heavy  metallic  oxides,  but  less 
so  with  the  earths  and  alkaline  earths. 

4.  Desulphurizing  or  precipitating  agents. 
Iron  in  the  form  of  iron  filings  and  as  pieces 
of  wire. 

Potassium  cyanide  and  potassium  ferro- 
cyanide  (see  p.  56). 

Caustic  alkalies  and  carbonates  decom- 
pose metallic  sulphides.  The  metal  is  sep- 
arated, and  sulphites,  hyposulphites,  and 
sulphates  of  the  alkalies,  together  with 
alkaline  sulphide,  are  formed.  The  latter 
forms  a  sulphur-salt  with  one  part  of  the 
metallic  sulphide,  which,  as  a  general  rule, 
can  be  decomposed  with  iron. 

Carbon  promotes  desulphuration  (black 
flux,  potassium  carbonate  and  flour).  Salt- 
petre oxidizes  metallic  sulphides,  while  the 
metals  are  separated. 


RE- AGENTS  USED  IN  ASSAYING.  61 

5.  Sulphurizing  agents.     Sulphur  in  the 
form  of  flowers  of  sulphur ;  or  of  iron  py- 
rites. 

6.  Concentrating   fluxes.       Lead    in    a 
granulated  form   (assay  lead).     Silver  for 
alloying  with  gold   (quartation).     Gold  for 
collecting    copper    (assay    of    nickel    and 
cobalt) .      Copper  oxide  for  t in .     Iron  pyrites 
as   collecting   agent   for   copper  (assay  of 
matt). 

7.  Decomposing  and   volatilizing  fluxes. 
Charcoal    and'  graphite   for    decomposing 
sulphates,  arseniates  and  antimoniates  by 
roasting.     Ammonium  carbonate  for  decom- 
posing sulphates,  especially  copper  sulphate, 
at  red  heat,  but  less  completely  lead  and 
bismuth  sulphates.     Common  salt  for  the 
volatilization  of  antimony  and  arsenic  in 
refining  black  copper  according  to  the  Cor- 
nish method. 

8.  Air-excluding  fluxes  (covering  agents). 
Decrepitated  common  salt,  as  free  from  sul- 
phates as  possible,  fuses  easily  and  becorn- 


62  THE  ASSAYER'S  GUIDE. 

ing  very  thinly-fluid  washes  down  particles 
of  metal  adhering  to  the  sides  of  the  assay 
vessels.  Refined  slag  from  charcoal  iron 
blast  furnaces. 

Re-agents  for  wet  assays.     The  following 
are  principally  used : 

1.  For  assays  by  gravimetric  and  color  i- 
metric    analysis.       Acids:     Hydrochloric, 
sulphuric,    nitric  and  acetic;    aqua   regia. 
Bases  and  salts:  Caustic  alkalies,  alkaline 
carbonates,  potassium  chlorate,  ferrous  sul- 
phate,   sodium    sulphide,  etc.     Metals   for 
precipitation :  Iron  in  the  form  of  wire,  or 
in  a  pulverulent  condition,  for  copper ;  zinc 
in  the  form  of  wire  or  granules,  or  in  a 
pulverulent  state,  as  a  reducing  agent  for 
iron   solutions,   etc. ;  copper ;   bromine  for 
decomposing  sulphurets,  compounds  of  gold, 
etc. 

2.  For    volumetric    assays.      Potassium 
,  permanganate ;  sodium  sulphide ;  potassium 

cyanide ;  barium  chloride ;  potassium  iodide, 
free  and  with  dissolved  iodine;  sodiurn 


EE- AGENTS   USED    IN   ASSAYING.  63 

hyposulphite ;  ferric  chloride ;  sodium  chlor- 
ide; potassium  sulphocyanide,  etc.  As  in- 
dicators: Litmus  tincture,  Brazil  wood 
tincture,  etc.,  for  acids  and  alkalies;  the 
salts  of  iron,  nickel  and  lead,  and  sodium 
nitroprusside,  for  sulphur ;  starch-paste  for 
iodine;  potassium  sulphocyanide,  etc.,  for 
iron  oxide. 


64 


III. 

cf  Silver  Ores  by  Heat — Cupellativn. 

SILVER  occurs  in  nature  chiefly  in  lead 
ores,  (galena,)  and  native,  as  in  the  Lake 
Superior  copper  mines,  or  less  commonly 
as  chloride  of  silver,  as  is  the  case  in  the 
extensive  mines  of  Chili.  The  following 
directions,  however,  refer  equally  to  the 
assays  of  all. 

As  with  all  minerals  to  be  investigated 
by  these  methods,  the  ore  must  previously 
be  reduced  to  the  finest  possible  powder,  for 
which  purpose,  where  many  assays  are 
made,  a  large  iron  bowl  is  used  as  a 
mortar,  the  pestle  having  a  wooden  handle 
attached  at  right  angles  to  the  iron  part, 
enabling  us  thus  to  employ  a  much  greater 
force  than  if  it  were  straight,  as  commonly 
is  the  case.  The  usual  shape  of  a  mortar. 


ASSAY    OF    SILVER    ORES    BY    HEAT.  65 

used  in  kitchens  is  not  so  good,  for  its 
depth  prevents  its  being  cleaned  sufficiently 
to  insure  accuracy.  In  lieu  of  the  former, 
and  when  small  quantities  only  are  de- 
sired to  be  pulverized,  an  agate  mortar 
may  suffice.  Of  the  ore  we  weigh  off  one 
part, — about  3  grammes,  equal  to  46  grs. 
Troy,  (say  50  grs.)  is  a  good  standard 
weight, — and  .  mix  it  with  ten  parts  by 
weight  of  pure  lead,  and  from  one-tenth  to 
one-tifth  part  of  borax,  in  the  manner  de- 
scribed below. 

The  lead  is  added  to -extract  all  impuri- 
ties, such  as  copper,  nickel,  &c.,  and  in 
cases  where  these  occur  in  great  abun- 
dance, should  be  used  in  the  proportions 
even  up  to  fifteen  and  twenty  parts,  though 
it  is  always  injurious,  and  .tends  to  create 
a  loss,  to  add  too  much. 

To  the  rules  for  testing  the  quality  of 
alloys  of  silver  and  copper,  will  be  found 
subjoined  a  table  by  Erker,  to  regulate  this. 

The  lead  of  commerce  contains  many  im« 


66  THE    ASSAYEE  S    GUIDE. 

purities,  iii  the  shape  of  other  metals, 
which,  since  silver  always  is  among  thoni, 
is  very  injurious  to  our  assays,  and  it  ia 
therefore  necessary  to  obtain  a  purer  article. 
At  silver  furnaces  lead  is  produced  as  an 
extra  product,  sufficiently  pure  for  our  pur- 
poses. That,  for  instance,  thus  procured 
from  the  smelting  works  at  Freiberg  in 
Saxony,  and  used  there  by  the  assay ers, 
contains,  to  6.40000  parts  of  lead,  from 
0.00001  to  0.000015  parts  of  silver,  too 
slight  an  impurity  to  affect  the  result  of 
the  assay.  If  so  situated  as  not  to  be  able 
to  get  it  in  this  manner,  the  best  way  is  to 
reduce  it  by  a  galvanic  process  from  acetate 
of  lead.  This,  the  sugar  of  lead  of  com- 
merce, we  can  readily  dissolve  in  luke- 
warm water,  after  which  we  should  filter 
off  the  solution,  and  introduce  a  rod  of 
zinc,  by  which  process  all  the  lead  is  re- 
duced and  collected  round  that  metal. 
After  some  time  remove  it,  and  continue 
in  this  manner  until  all  the  lead  is  pre- 


ASSAY   OF    SILVER   ORES    BY    HEAT.  67 

cipitated.  It  is  then  to  be  repeatedly 
washed  with  care  to  remove  the  acid,  and 
afterward  dried  between  blotting  paper. 
If  not  in  a  sufficiently  pulverized  shape,  it 
need  only  be  shaken  a  little  in  a  towel  and 
finally  sieved.  A  spoon  containing  a  given 
amount — five  parts,  equal  to  250  grs.,  is  con- 
venient— is  used  to  measure  the  quantity 
for  each  assay,  thus  avoiding  the  tedium  of 
weighing  each  time,  a  matter  of  consider- 
able consequence  in  an  assaying  office, 
where  frequently  hundreds  of  assays  are 
made  in  a  day. 

The  vessel  into  which  the  mineral,  to- 
gether with  the  lead  and  borax,  is  placed, 
to  be  introduced  into  the  muffle  of  the  fur- 
nace, is  represented  in  fig.  1,  Plate  II.  (See 
the  description  given  a  few  pages  back.) 
We  first  put  one-half  of  the  lead  to  be 
used  in  it,  and  on  the  top  the  silver  ore, 
mixing  the  two  with  great  care,  not  to 
spill  the  least  particle,  and  afterward 
cover  it  with  the  rest  of  the.  lead,  and 


68  THE  ASSAYER'S  GUIDE. 

sprinkle  the  borax  over  the  whole.  The 
latter  is  used  to  facilitate  the  melting  of 
the  lead,  and  to  produce  a  good  slag. 
When  much  tin,  zinc,  or  lime  is  present 
in  the  ore,  the  borax  should  be  increased 
in  quantity  up  to  the  largest  amount  before 
mentioned. 

If  we  desire  to  test  ores  containing  very 
little  silica,  and  our  crucibles  are  not  as 
perfect  as  we  might  wish  them  to  be,  it  is 
very  advisable  to  make  use  of  some  quartz 
or  glass-powder,  to  be»  added  immediately, 
or,  better  still,  when  the  slag  is  forming, 
and  the  process  of  calcining  is  thus  at  an 
end. 

We  should,  for  the  sake  of  economy  with 
the  fuel,  make  several  assays  at  once,  and 
always  five  or  six  of  each  ore,  afterward 
taking  the  average,  and  thus  regulating 
our  own  labour. 

After  previously  firing  the  furnace,  and 
bringing  the  muffle  to  a  regular  and  con- 
stant red-heat,  we  may  introduce  the  cru- 


ASSAY    OF   SILVER   ORES    BY    HEAT.  69 

cibles.  To  quicken  the  melting  of  the 
lead,  we  place  some  pieces  of  well-dried 
charcoal,  which  should  always  be  kept  on 
hand,  in  front  of  the  crucibles.  Yapours 
will  be  observed  to  be  emitted,  caused  by 
the  discharge  of  volatile  substances.  The 
door  of  the  muffle,  previously  closed, 
should  be  kept  perfectly  open  as  soon  as 
the  operation  of  calcining  or  roasting  the 
ore  has  properly  commenced,  to  admit 
fresh  air,  and  prevent  the  heat  from  in- 
creasing too  much. 

This  process  generally  lasts  about  twenty 
minutes,  after  which,  by  introducing  fresh 
coals  into  the  muffle  and  again  closing  the 
door,  we  raise  the  heat,  and  continue  it 
sufficiently  long  to  let  the  slags  collect  and 
flow  easily,  so  as  to  make  a  crust  round  the 
white-hot  metal.  When  not  employing  a 
sufficiently  high  temperature,  the  slag  will 
remain  thick  or  tough,  and  retain  the 
metallic  alloy  of  silver  and  lead  in  small 
particles  disseminated  throughout  the  mass. 


THE  ASSAYER'S  GUIDE. 


From  the  circular  portion  of  argentiferous 
lead,  which  appears  to  be  in  a  constant 
rotary  motion  in  the  centre  of  the  slag, 
vapours  of  lead  rise  incessantly.  The  time 
that  should  be  occupied  by  this  process  of 
melting  varies  much  according  to  the 
character  and  quality  of  the  ore,  which 
sometimes,  though  rarely,  may  even  require 
something  more  than  half  an  hour.  Gene- 
rally much  less  time  is  wanted  with  a  good 
fire,  and  the  assayer  can  always  see  at  what 
time  the  encircling  slag  has  been  properly 
separated  from  the  metal,  and  even  with 
very  little  practice  is  enabled  to  regulate  it. 
We  now  again  open  the  muffle,  and  by 
oxidizing  some  more  lead  during  the  space 
of  ten  minutes,  cover  the  metal  entirely, 
and  after  that,  once  more  apply  a  strong 
heat  for  a  few  minutes  to  make  the  slags 
flow  easy,  and  then  taking  out  the  crucibles, 
pour  the  whole  contents  into  the  different 
hollows  of  the  iron  plate,  illustrated  by  fig, 
0.  Plate  II.  This  should  be  done  very 


ASSAY   OF  SILVER  ORES   BY   HEAT.          7 1 

quickly,  for  otherwise  the  lead  will  not 
collect  in  one  button,  but  be  distributed 
in  small  particles  all  over  the  molten  slag 
as  above.  A  little  practice  will  soon  accus- 
tom any  one  to  all  these  operations. 

On  cooling,  with  a  stroke  or  two  of  the 
hammer  we  separate  the  slags  from  the 
metallic  buttons,  and  with  a  few  more 
easily  shape  the  latter  into  cubes  as  regular 
as  possible. 

The  crucibles  shown  in  fig.  2,  Plate  II. 
come  into  use  at  this  part  of  the  assay.  If 
well  made  and  dried,  they  should  be  very 
porous,  and  so  friable  as  to  be  crushed 
between  the  fingers  with  ease. 

In  these  cupels  we  expose  the  metal 
cubes  to  a  moderate  red-heat,  which  we  are 
enabled  to  regulate  by  inserting  cold  pieces 
of  pottery — old  crucibles  will  be  found  very 
serviceable — and  leaving  the  furnace  open. 
The  rising  vapours  are  from  the  lead,  and 
continue  until  that  peculiar  bright  flash  of 
light  is  observed,  termed  silberblick,  (silver- 


72  TUP:  ASSAYER'S  GUIDE. 

gleam,)  in  German  mining  and  smelting 
technology,  and  from  which  we  know  that 
the  silver  is  pure.  The  utmost  attention 
should  be  paid  to  this  part  of  the  assay,  to 
ascertain  the  moment  when  this  occurs. 
The  coolers  are  then  carefully  removed,  the 
aperture  closed,  and  the  most  intense  heat 
possible  kept  up  for  a  few  moments.  To 
do  this  well  is,  I  may  say,  the  chef  tfoeuvre 
of  an  assayer,  and  on  it  depends,  in  a  great 
measure,  the  accuracy  of  the  assay;  for  the 
silver,  when  pure,  requires  a  much  greater 
heat  to  bring  it  to  the  melting  point  than 
when  it  contains  even  a  very  small  admix- 
ture of  lead ;  and  for  this  reason,  if  we  do 
not  instantly  elevate  the  temperature  when 
the  ceasing  of  the  rainbow  colours  and  the 
bright  light  of  the  globule  of  pure  silver 
inform  us  that  all  the  lead  has  left, — then 
the  silver  would  cool  suddenly,  and,  of 
course,  quicker  at  the  surface  than  in  the 
interior  or  at  the  bottom,  and  by  this 
subitaneous  contraction  cause  a  spattering 


ASSAY    OF   SILVER   ORES   BY    HEAT.  73 

motion  of  the  yet  unconsolidated  particles, 
and  be  productive  of  great  loss  to  the 
assay. 

There  is  an  old  adage  current  among 
German  smelters  and  assay  ers, — probably 
known  to  all  who  may  have  had  the 
advantage  of  studying  this  art  in  that 
country,  where  it  has  been  brought  to  such 
perfection, — which,  since  it  is  many  centu- 
ries old,  shows  how  long  it  has  been  re- 
garded as  the  great  aim,  in  this  mode  of 
testing  silver  ores,  to  keep  up  a  moderate 
temperature  as  long  as  any  lead  is  left,  and 
to  apply  intense  heat  as  soon  as  all  has  de- 
parted. I  insert  them  here  : 

"  Kiihl  getrieben,  heisser  Blick 
1st  des  Probierer's  Meisterstiick." 

In  English  it  would  be :  To  evaporate 
coolly  and  to  use  heat  when  pure,  is  the 
masterpiece  of  an  assayer. 

When  the  buttons  of  pure  silver  have 
cooled,  we  grasp  them  firmly  with  a  pair 
of  pincers,  tight  enough  to  compress  the 


74  THE  A&SAYER'S  GUIDE. 

sides,  thus  exposing  the  bottom  more,  and 
with  a  wire  brush  remove  the  adhering 
particles  of  litharge,  and  dust  of  the  cupel. 
Turning  them  half  round  so  as  to  make 
the  base  a  square,  we  repeat  the  operation, 
and  then  weigh,  but  only  when  quite  cold, 
since  otherwise  the  heat,  by  increasing 
the  bulk,  might  tend  to  create  a  varia- 
tion. 

The  silver  produced  in  this  manner,  it 
should  be  remarked,  is  not  perfectly  pure, 
chemically  speaking,  but  the  slight  impu- 
rities are  too  insignificant  to  deserve  any 
attention  from  an  assayer,  who  has  nothing 
but  technical  purposes  in  view,  though 
they  might  require  it  from  a  scientific 
chemist ;  and  for  this  latter  reason,  -I  have 
thought  proper  in  the  fourth  chapter  to  sug- 
gest a  method  to  ascertain  the  exact 
amount  of  silver  in  this  button,  should  it 
be  deemed  necessary,  though,  I  must  add, 
that  such  precision  can  only  be  required 
at  mints,  if  the  investigations  are  not  con- 


ASSAY   OF   SILVER   ORES    BY    HEAT.  75 

ducted  for  science'  sake,  in  which  case,  the 
wet  process  would,  of  course,  be  preferred 
from  the  beginning. 

Besides  this,  small  inaccuracies  in  the 
shape  of  losses,  as  has  already  been  re- 
marked, cannot  be  averted,  even  though 
the  assay  be  performed  with  the  greatest 
care,  as  the  evaporating,  or  rather  oxid- 
izing lead  probably  carries  off  small  par- 
ticles of  silver,  particularly  when  too  much 
heat  is  used  during  that  process.  It  is  im- 
possible to  give  any  perfect  rules  how  to 
obviate  such  faults,  since  so  much  depends 
on  the  care  and  attention  paid,  as  well  as 
on  the  acquired  practice  and  innate  prac- 
tical skill  of  the  assayer ;  yet,  pre-supposing 
all  this  as  perfect,  the  Parisian  mint  has 
established  a  table  to  regulate  their  assays, 
which  will  be  found  on  pages  77  and  78. 
From  this  it  is  seen  that  the  different  losses 
with  different  quantities  of  silver  vary  con- 
siderably, nor  is  the  loss  a  per-centage, 
being  greatest  where  the  original  or  true 


76  THE  ASSAYER'S  GUIDE. 

amount   of  silver  in   the   ore   or   alloy    is 
seven  hundred. 

This  table  should  always  be  referred  to, 
as  it  enables  us  to  calculate  the  true 
amount  of  silver,  and  to  rectify  those  un- 
avoidable faults  which  may  be  occasioned 
by  the  lead  carrying  off  portions  of  the 
silver  entirely,  or  else  drawing  them  along 
with  it  into  the  pores  of  the  crucible. 


77 


IV. 

A  Table  to  rectify  ike  Loss  incurred  during 
tJie  Silver  Assay. 


Real  amount  of 
sUver. 

Amount  of  silver 
found  by  the  assay. 

Loss  during  the 
procesp. 

1000 

998-97 

1-03 

975 

973-24 

1-76 

950 

947-50 

2-50 

925 

921-75 

3-25 

900 

896-00 

4-00 

875 

870-93 

407 

850 

845-85 

4-15 

825 

820-78 

4-22 

800 

795-70 

4-30 

775 

770-59 

1-41 

750 

745-48 

4-52 

725 

720-36 

4-64 

700 

695-25 

4-75 

675 

670-27 

4-73 

650 

645-29 

4-71 

625 

620-30 

4-70 

600 

595-32 

4-08 

575 

570-32 

4-68 

78 


THE   ASSAYER'S   GUIDE. 


Real  amount  of 
silver. 

Amount  of  •silver 
found  by  the  assay. 

Loss  during  the 
process. 

550 

545-32 

468 

525 

520-32 

4-68 

500 

495-32 

4-68 

475 

470-50 

4-50 

450 

445-69 

4-31 

425 

420-87 

4-13 

400 

396-05 

3-95 

375 

371-39 

3-61 

350 

346-73 

3-27 

325 

322-06 

2-94 

300 

297-40 

2-60 

275 

272-42 

2-58 

250 

247-44 

2-56 

225 

222-45 

2-55 

200 

197-47 

2-53 

175 

172-88 

2-12 

150 

148-30 

1-70 

125 

123-71 

1-29 

100 

99-12 

0-88 

75 

74-34 

0-66 

50 

49-56 

0-44 

25 

24-78 

0-22 

LOSS   DUBING   THE   SILVER   ASSAY.  79 

Iii  Freiberg  somewhat  different  results 
have  been  obtained.  With  refined  silver 
the  loss  by  absorption  by  the  cupel  was 
found  to  be  0.0015  to  0.0002 ;  and  in  alloys 
of  medium  .richness  the  loss  was  greater 
than  that  stated  in  the  preceding  table. 
For  instance,  with  750  thousandths  and  16 
weights  of  lead,  the  loss  was  5.55  thou- 
sandths, but  with  11  weights  of  lead  it  ac- 
corded with  the  table,  4.52  thousandths. 
According  to  Plattner,  fine  silver  with  five 
times  the  quantity  of  lead  frequently  gives 
a  loss  up  to  0.009,  refined  silver  with  937 
thousandths  and  five  times  the  quantity  of 
lead,  0.0042  to  0.0059  ;  refined  silver  with 
687  to  750  thousandths  and  14  times  the 
quantity  of  lead,  0.0073  to  0.0083. 


V. 

Gay-Lussads  Process  far  assaying  Silver 
Alloys. 

THIS  modus  operandi  is  one  which,  from 
its  very  simplicity  and  shortness,  almost 
necessarily  insures  success,  but  it  is  only 
intended  for  alloys,  such  as  coins,  and  can, 
therefore,  if  applied  to  ores,  only  be  used 
to  ascertain  the  real  amount  of  silver  in 
the  button  produced  in  the  last  assay, 
which,  as  already  observed,  contains  a  very 
minute  amount  of  spurious  metals  in  an 
alloyed  state. 

It  was  proposed  by  Gay-Lussac,  and 
from  the  indubitableness  of  its  results, 
has  since  been  introduced  in  France,  and 
most  parts  of  Germany,  to  regulate  the 
assays  of  the  mint. 

They   dissolve    a   given    weight   of   the 


GAY-LUSSAC'S    PROCESS.  81 

alloy  in  nitric  acid  and  precipitate  from  the 
solution  all  the  silver  as  chloride  of  silver 
by  means  of  a  standard  solution  of  sodium 
chloride.  For  this  purpose  a  normal  solu- 
tion of  common  salt  is  required,  100  cubic 
centimeters  of  which  will  precipitate  1 
gramme  of  chemically  pure  silver.  There 
is  further  required  a  decmormal  solution  of 
common  salt,  containing  but  one-tenth  the 
quantity  of  common  salt  in  solution  in  the 
first,  and  a  decinormal  solution  of  silver  in 
nitric  acid  containing  1  milligramme  of  sil- 
ver in  1  cubic  centimeter  of  solution. 

Preparation  of  the  assay  solution.  The 
degree  of  richness  of  the  silver  is  approxi- 
mately determined  by  a  preliminary  assay, 
4  to  6  thousandths  parts  the  amount  of 
silver  found  by  this  assay  being  added  to 
the  result.  It  is  generally  preferred  to 
assume  the  degree  of  richness  a  few  thou- 
sandths higher  than  is  actually  the  case, 
and  to  base  the  calculation  for  the  quantity 
of  assay-sample  required  upon  this,  as,  to 


82  THE  ASSAYER'S  GUIDE. 

effect  the  more  rapid  settling  of  the  silver 
chloride,  it  is  more  preferable  to  add,  during 
the  titration,  a  few  thousandths  from  the  de- 
cinormal  solution  of  salt  than  to  be  obliged 
to  add  from  the  decinormal  solution  of  sil- 
ver. The  quantity  of  alloy  containing  1 
gramme  of  silver  which  is  to  be  taken  is 
then  calculated  (for  instance,  if  the  prelim- 
inary assay  gives  a  content  of  897  thou- 
sandths, then  1.115  grammes  of  alloy  con- 
taining 1  gramme  of  silver  should  be  taken, 
1000  :  897  =  x  :  1000).  The  sample  in  the 
form  of  shavings  or  granules  is  placed 
in  a  numbered  flask,  together  with  6  to  7 
cubic  centimeters  of  nitric  acid  free  from 
chlorine,  and  dissolved  either  on  a  water  or 
sand  bath.  The  flasks  in  which  the  sam- 
ples are  dissolved  are  from  10  to  15  centi- 
meters high,  and  5  to  5 2  centimeters  wide. 
If  several  assays  are 'to  be  made,  it  is  ad- 
visable to  dip  the  flasks,  which  are  arranged 
upon  a  stand,  Fig.  D,  into  hot  water.  (A 
black "  residue  maybe  gold  or  sulphide  of 


83 

silver;  should  the  latter  be  the  case,  some 
concentrated  nitric  acid  is  added  and  the 
fluid  heated,  or  sulphuric  acid  used.)  The 
nitrous  acid  formed  is  then 
driven  out  of  the  flask  by 
means  of  a  small  bellows  with 
curved  extremity,  and  the 
contents  of  the  flask  are  treat- 
ed with  the  normal  solution. 
But,  as  the  influence  of  the  temperature 
upon  the  volume  of  the  normal  solution  of 
common  salt  must  be  taken  into  considera- 
tion, its  liter  must  always  be  determined  on 
the  same  day  the  assays  are  to  be  made, 
with  1  gramme  of  pure  silver  +  1  to  2  cubic 
centimeters  decinormal  solution  of  silver,  in 
order  to  be  able,  for  the  above-mentioned 
reason,  to  use  decinormal  solution  of  salt  for 
the  final  tit  ration.  The  silver  solution  is 
then  titrated  by  placing  the  glass  flask  in 
the  metal  cylinder  C,  Fig.  E,  standing  upon 
the  sliding  carriage  B  (Sire's  apparatus). 
The  glass-cock  c  (a  pinch-cock  may  be  used 


84 


THE   ASSAYER7S   GUIDE. 


instead)  is  then  opened  and.  accompanied 
by  the  admission  of  air  through  a,  the  nor- 
mal solution  of  sodium  chloride  flows  from 
the  vessel  A  through  h,  the  thermometer 


FIG.  E. 

tube  by  and  the  rubber  tube  d,  into  the 
burette  e.  It  ascends  in  this,  and  a  sniall 
quantity  reaches  the  saucer  g  through  the 
grifice/.  The  cock  c  is  now  closed  (h  and 


GAY-LUSSAC'S  PROCESS.  85 

e  may  be  also  directly  connected  by  a  rub- 
ber tube  provided  with  a  clip)  and  the 
pipette  6,  which  is  now  filled,  will  contain 
exactly  100  cubic  centimeters  of  liquid. 
The  index  finger  of  the  left  hand  is  now 
placed  upon  the  mouth /of  the  pipette,  the 
rubber  tube  d  is  detached  from  the  lower 
end  of  the  pipette  e,  and  the  sliding  car- 
riage B,  upon  which  stands  the  metal  cylin- 
der G  containing  the  flask  with  the  solution 
of  silver,  is  pushed  underneath  the  dis- 
charge orifice  of  the  pipette.  The  index 
finger  is  now  removed  from  /,  and  the  100 
cubic  centimeters  of  the  common  salt  solu- 
tion are  allowed  to  run  into  the  flask,  care 
being  taken  that  the  pipette  does  not  rest 
on  the  neck  of  the  flask.  The  sliding  car- 
riage is  then  pushed  back,  the  flask  is  closed 
with  its  ground-glass  stopper,  and  its  con- 
tents are  cleared  by  shaking,  which  is  best 
done  by  inclosing  it  for  the  purpose  in  a 
metal  cylinder  of  proper  size.  If  many 


86 

assays  are  to  be  made,  it  is  advisable  to  use 
Gay-Lussac's  or  Mulder's  agitator. 

One  cubic  centimeter  of  decinorrnai  so 
lution  is  now  added  to  the  entirely  clear 
fluid  standing  over  the  precipitate  of  silver 
chloride,  by  means  of  a  graduated  pipette 
contained  in  a  flask,  Fig.  F,  whereby  the 
point  of  the  pipette  should  be  placed  against 
the  neck  of  the  flask  containing  the  silver 
solution.  If  turbidity  is  produced, 
the  silver  solution  is  agitated  until 
it  is  again  clear,  and  1  cubic  centi- 
^  meter  of  the  decinormal  solution  of 
DIG.  r.  common  salt  again  added,  etc.,  until 
the  last  cubic  centimeter  which  is  added 
does  not  produce  any  turbidity.  This  last 
cubic  centimeter  is  not  taken  into  calcula- 
tion, and  only  one-half  of  the  one  previously 
added.  (For  the  reason  previously  stated, 
it  is  more  suitable  to  use  decinormal  solu- 
tion of  common  salt  than  decinormal  solu- 
tion of  silver  for  the  final  reaction.) 

Calculation.      Suppose   the   richness  of 


GAY-LUSSAC'S   PROCESS.  87 

the  alloy  was  found  according  to  the  pre- 
liminary assay  to  be  897  thousandths,  1115 
thousandths  of  the  sample  containing  1.000 
gramme  would  have  to  be  weighed  off.  1000 
cubic  centimeters  of  the  decinormal  solution 
of  salt  —  1  gramme  of  silver.  Now  sup- 
pose 1002.5  cubic  centimeters  of  decinor- 
mal solution  of  common  salt  had  been  used, 
1000  parts  of  the  alloy  would  therefore  con- 
tain 899.1  parts  of  silver. 

In  case  mercury  should  be  present,  so- 
dium acetate  (0.5  gramme  to  5  thousandths 
of  mercury)  is  added,  which  will  prevent 
the  mercury  from  being  precipitated  by  the 
sodium  chloride  solution ;  or  the  mercury  is 
previously  volatilized  by  heating  the  assay 
sample  in  a  small  graphite  crucible  in  the 
muffle.  For  bismuth  some  tartaric  acid  is 
added.  In  case  tin  is  present,  the  assay 
sample  is  dissolved  in  sulphuric  acid  instead 
of  nitric  acid.  According  to  Thorpe,  only 
2  parts  of  silver  chloride  freshly  precipi- 
tated, and  0.8  part  that  has  been  blackened 


88 

by  exposure  to  light,  are  dissolved  in  106,. 
000  parts  of  nitric  acid. 

Preparation  of  the  normal  solutions.  A 
completely  saturated  solution  of  common 
salt  is  prepared,  of  which,  if  the  salt  used 
is  entirely  pure,  170  cubic  centimeters  con- 
tain 54.15  grammes  of  common  salt.  These 
170  centimeters  are  diluted  to  the  volume 
of  10  liters.  100  cubic  centimeters  of  this 
solution  correspond  to  0.5415  gramme  of 
common  salt,  which  will  completely  precipi- 
tate 1  gramme  of  pure  silver.  The  true 
standard  is  obtained  by  pouring  100  cubic 
centimeters  of  the  common  salt  solution 
into  a  solution  of  1  gramme  of  chemically 
pure  silver.  This  is  agitated  by  shaking 
until  it  becomes  clear,  and  the  number  of 
thousandths  of  common  salt  or  silver  which 
remain  free  are  exactly  determined  by  the 
addition  of  an  observed  volume  of  very 
dilute  salt  solution  of  known  strength,  or 
of  a  decinormal  solution  of  silver,  and  from 
this  the  quantity  of  water  or  of  common 


G4Y-LUSSAC?S   PROCESS.  89 

salt  is  calculated  which  must  be  added  to 
obtain  the  correct  standard.  When  this 
addition  has  been  made,  a  new  test  is  had 
with  the  standard  solution  and  the  decinor- 
mal  solution  prepared  from  it,  and  this  is 
continued  until  the  solution  does  not  show 
a  perceptible  variation  from  the  correct 
standard 

The  decinorinal  solution  of  common  salt 
is  prepared  by  pouring  100  cubic  centi- 
meters of  the  standard  common  salt  solu- 
tion into  a  flask  capable  of  holding  1  liter 
and  filling  it  with  water  to  the  liter  mark. 
For  the  decinormal  solution  of  silver  1 
gramme  of  fine  silver  is  dissolved  in  5  to 
6  grammes  of  nitric  acid,  which  is  then 
diluted  with  water  to  1  liter. 

When  a  large  number  and  great  variety 
of  silver  alloys  have  to  be  assayed,  the 
following  tables,  A  and  B,  calculated  by 
Gay-Lussac  for  his  silver  assay,  will  be 
found  to  save  much  time  and  trouble  in 
determining  the  fineness  of  the  alloy.  If, 


90  THE  ASSAYER'S  GUIDE. 

after  the  addition  of  the  standard  common 
salt  solution,  no  reaction  takes  place  on 
adding  the  decimal  salt  solution  or  the 
decimal  silver  solution,  it  is  an  indication 
that  the  silver  in  the  alloy  assayed  amounts 
to  exactly  1000  milligrammes,  and  it  fur- 
ther indicates  that  the  standard  solution 
is  correct.  The  titer  is  indicated  in  the 
columns  by  the  figure  0. 


91 


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GAY-LUSSAC'S   PROCESS.  97 

In  making  Gay-Lussac's  assay  of  silver 
bullion,  a  great  deal  of  time  is  necessarily 
spent  in  waiting  for  the  suspended  chlo- 
ride to  settle  and  leave  the  liquid  clear 
in  order  to  observe  the  action  of  the  next 
drop  of  the  precipitant.  Whittell  has  re- 
duced this  loss  of  time  and  insured  greater 
facility  in  making  the  assay  by  dividing 
the  solution  containing  the  silver  into  sev- 
eral, say  five,  equal  parts  in  separate  ves- 
sels. They  are  placed  in  a  row,  and  3 
cubic  centimeters  of  salt  solution  added  to 
the  first,  4  c.  c.  to  the  second,  5  c.  c.  to  the 
next,  and  so  on.  After  the  precipitate  has 
subsided,  %  c.  c.  of  the  same  solution  is 
added  to  each  successively.  Numbers  1, 
2,  and  3  will  perhaps  show  traces  of  silver 
still  in  solution,  but  numbers  4  and  5 
none.  The  amount  precipitated  from  num- 
ber 3  multiplied  by  5  (as  it  represents 
only  5  of  the  original  solution  of  silver) 
will  be  the  amount  of  silver  contained  in 
the  ore  or  alloy  being  assayed.  A  simple 

7 


98  THE  ASSAYER'S  GUIDE. 

means  of  settling  the  precipitated  chloride 
almost  instantaneously  is  to  agitate  the 
solution  with  a  few  drops  of  chloroform. 
Its  action  seems  to  be  entirely  mechanical. 
The  agitation  displaces  the  chloroform  in 
minute  globules  throughout  the  silver  solu- 
tion, which  in  settling  to  the  bottom  carries 
with  it  every  particle  of  the  chloride. 


99 


VI. 

Assay  of  Native  Silver   Ores. 

THE  following  method  is  recommended 
by  Lowe.  When  silver  is  chemically  com- 
bined  in  the  ore  it  is  not  difficult  to  de- 
termine its  assay  value,  but  in  ores  con- 
taining the  silver  in  a  metallic  state,  the 
assay  can  yield  only  approximate  results. 
The  following  method  obviates  this  diffi- 
culty to  some  extent.  The  ore  is  coarsely 
powdered  and  sampled  down  to  a  half 
pound,  then  finely  powdered  and  passed 
through  a  100  mesh  sieve.  The  sifted 
ore  is  divided  into  four  parts  and  four 
assays  made  of  it,  each  amount  for  each 
assay  being  taken  as  nearly  as  possible 
from  the  same  relative  parts  of  each  quar- 
ter. The  average  of  the  four  assays  is 
taken  as  the  result.  The  metallic  par- 


100 

tides  or  scales  of  silver  which  will  not 
pass  through  the  meshes  of  the  sieve  are 
mixed  with  assay  lead,  cupelled,  and  the 
weight  of  the  resulting  button  reduced  to 
its  proper  value  added  to  the  result  ob- 
tained from  the  assay  of  the  siftings. 


101 


VII. 
Assay  of  Gold  Ores  by  Heat. 

THOSE  properties  of  silver,  which  enable 
us  to  assay  its  ores  by  the  process  of 
cupellation,  are  so  equally  characteristic 
of  gold  and  its  ores,  that,  were  I  to  dwell 
more  at  length  on  this  first  part  of  the 
operation,  it  would  be  a  mere  repetition  of 
what  has  been  said  under  the  head  of 
Silver,  and  therefore  I  shall  only  refer  the 
reader  to  the  remarks  given  above. 

When,  however,  that  process  is  com- 
pleted, .and  when  therefore  with  silver  we 
would  have  procured  the  final  result,  the 
real  gold  assay  only  commences,  for  gold, 
though  always  native,  contains  silver,  pla- 
tinum, &c. 

I  must  remark  that,  since  gold  ores  are 
almost  invariably  excessively  poor,  com- 


102  THE  ASSAYER'S  GUIDE. 

pared  with  those  of  other  metals,  we 
should  arrange  our  assays  accordingly, 
and  commence  with  a  larger  amount  of 
ore  than  is  necessary  in  other  cases.  For 
this  purpose  it  is  common  to  begin  with 
six  different  parts  of  ore  of  50  grs.  each, 
which,  after  being  mixed  with  lead  and 
borax  as  with  silver,  are  committed  to 
the  muffle  in  as  many  separate  crucibles. 
The  products  are  then  melted  up  into  two 
buttons,  in  two  different  cupels  of  the  same 
kind,  and  these  again  in  the  process  of 
extracting  the  lead  are  concentrated  into 
one.  Of  course,  wnen  the  assay  is  finished 
we  are  obliged  to  divide  the  produce  by  six 
to  ascertain  the  per-centage  amount  of  gold 
in  the  specimen  under  examination. 

After  having  proceeded  thus  far,  it  is  neces- 
sary to  procure  some  perfectly  pure  silver, 
for  which  we  have  the  following  methods: 
first,  by  producing  chloride  of  silver,  which 
is  done  by  precipitating  the  silver  from  the 
nitric  acid  solution,  with  muriatic  acid,  and 


ASSAY    OF   (SOLD   ORES   BY   HEAT.  103 

melting  it  in  a  porcelain  crucible,  with  pot- 
ash ;  chloride  of  potash  and  the  pure  silver 
being  thus  formed:  or  secondly  by  the 
galvanic  process,  the  virgin  metal  being 
thus  collected  round  a  rod  of  zinc  immersed 
in  the  acid  (nitric)  liquid  from  which, 
as  above,  the  silver  has  been  extracted  by 
adding  muriatic  acid,  but  which  precipitate 
must  remain  in  the  same  vessel.  The 
silver  is  then  preserved  in  the  shape  of 
filings. 

It  is  necessary  to  make  use  of  this  silver 
whenever  the  quantity  of  gold  in  the  last 
produced  button  is  more  than  one  fourth, 
(hence  the  term  quartatiori)  since  experi- 
ence has  shown  that  if  there  are  not  at  least 
about  three  quarters  the  amount  of  silver 
(rarely  the  case  with  ores)  in  this  alloy, 
the  gold  would  protect  the  particles  of 
silver  from  the  action  of  the  acid,  which, 
as  will  become  evident  from  the  sequel, 
would  prove  fatal  to  our  investigations. 

Of  the  pure  silver,  two  and  a  half  time* 


104  THE  ASSAYER'S  GUIDE. 

the  weight  of  the  buttons  of  impure  gold, 
and  about  half  the  weight  of  both  in 
pure  lead,  should  be  melted  up  with  them 
in  one  crucible,  (fig.  2,  Plate  II.)  Tlsis 
single  button  of  gold  and  silver  alloy  is  to 
be  hammered  flat  on  a  little  steel  anvil, 
and  slightly  curved,  as  this  shape  will 
allow  it  more  easily  to  pass  through  the 
mouth  of  a  little  vial,  in  which  it  is  now 
placed  to  be  boiled  with  nitric  acid  (2 
drams)  of  from  1  to  3  specific  gravity. 
The  vial  should  be  round  at  the  bottom 
as  this  is  performed  over  a  spirit-lamp. 
We  allow  the  liquid  to  boil  until  the 
yellowish  vapours  of  nitrous  acid  gas  have 
ceased  to  be  emitted.  The  gold  is  then 
pure,  and.  requires  only  to  be  boiled  a 
couple  of  times  in  water  to  remove  the  acid, 
and  then  to  be  heated  to  redness  to  evapo- 
rate the  water,  to  enable  us  to  weigh  it, 
which,  as  with  all  other  assays,  should 
never  be  done  till  the  metal  is  perfectly 
eold. 


ASSAY   OF   GOLD   ORES   BY    HEAT*.  105 

If  a  small  portion  of  platinum  be  in  the 
ore,  it  will  be  found  in  the  nitric  acid 
solution  of  silver.  (See  Platinum.) 

The  original  amount  of  silver  may  be 
ascertained  by  deducting  the  weight  of  the 
gold  from  the  button  prodiw^  before 
other  pure  silver  was 


106 


VIII. 
Assay  of  Gold  Ores  by  Amalgamation. 

THIS  method  is  founded  on  the  fact,  that 
gold  unites  with  quicksilver  to  form  an 
amalgam,  for  thus  the  alloys  of  mercury 
and  other  metals  are  termed.  It  is  one 
that  may  answer  for  peculiar  circum- 
stances, though  it  is  not  accurate  enough 
to  serve  as  a  regular  dokimastic*  test,  since 
lead  and  silver  also  produce  amalgams. 

We  require  pure  mercury  for  this  pur- 
pose; and  as  the  quicksilv.er  of  commerce 
generally  contains  some  lead,  we  must  pu- 
rify it  by  pressing  it  through  a  piece  of 
buckskin. 

The   powdered    gold    ore,   which   ought 


*  A  technical  term,  derived  from  the  Greek  verb 
,  to  try,  to  test  the  purity  of  a  thing. 


ASSAY   OF    GOLD    ORES    BY   AMALGAMATION.  107 

first  to  be  reduced  in  volume  by  washing, 
is  brought  in  contact  with  the  quicksilver, 
the  sand  or  gangue-rock  removed  by  sift- 
ing the  mass  through  a  coarse  cloth ;  after 
which,  by  forcing  the  quicksilver  through 
some  buckskin,  the  amalgam  is  retained. 

By  evaporating  the  mercury  in  an  iron 
spoon  over  a  lamp,  the  gold  is  procured, 
which  will,  however,  still  be  found  to  con- 
tain silver  or  lead,  if  these  occur  in  the 
ore. 


108 


IX. 
Assay  of  Gold  ~by  Washing. 

THIS  is  a  way  of  ascertaining  the  ap- 
proximate value  of  a  gold  ore,  which  hardly 
deserves  being  called  an  assay,  although, 
with  an  experienced  hand,  tolerable  accu- 
racy may  be  attained. 

It  is  based  on  the  fact,  that  gold  is  much 
heavier  than  quartz  or  other  ganguerock, 
and  therefore  the  rock  should  be  well 
pounded  for  this  operation. 

The  process  is  precisely  the  same  as  that 
used  to  extract  gold  from  the  sand  of  river 
beds,  and  which  is  now  so  extensively  em- 
ployed in  California.  Even  the  vessels 
used  are  frequently  of  the  same  kind, 
though  it  is  better  to  have  a  small  glass 
cylinder,  about  three  times  the  length  of 
the  part  that  will  be  occupied  by  the  ore, 


ASSAY    OF    GOLD    ORES    BY    WASHING.       101) 

and  three-quarters  of  an  inch  in  diameter, 
closed  at  the  end,  like  a  common  chemical 
test-glass.  I  would  suggest,  if,  where  used, 
the  gangue-rock  or  sand  be  always  of  the 
same  kind,  having  a  mark  round  the  tube 
made  with  a  slight  scratch  of  the  diamond, 
up  to  where  a  certain  quantity  by  weight 
of  the  ore  would  reach.  One  hundred 
grains  would  not  be  too  much,  if,  for  in- 
stance, the  rock  is  quartz;  and  it  is  also 
the  most  convenient  amount,  from  the 
facility  thus  afforded  in  afterward  calcu- 
lating the  per-centage.  Under  circum- 
stances where  we  have  to  deal  with  ores 
in  which  the  original  rock  is  not  always 
the  same,  it  would  be  well  to  have  several 
such  tubes,  to  each  of  which  its  peculiar 
rock  might  be  allotted;  or  one  with  dif- 
ferently marked  lines.  In  this  manner, 
one  such  line  might  indicate  the  part  of 
the  tube  which  would  be  filled  by  a  hun- 
dred grains  of  the  quartzose  ore,  another 
the  portion  which  would  be  occupied  by 


110 

the  same  weight  of  a  talcose  one,  and  so 
on.  The  lines  will  vary  in  height  as  the 
ratio  of  the  various  specific  gravities  of  the 
respective  ores. 

When  the  properly  pulverized   ore  has 
been  placed  in   the  glass  tube,  the  latter 
should  be  filled  up  two-thirds  with  water, 
and  tightly  corked ;  after  which,  by  repeater* 
shakings,  the  gold  will  be  collected  below 
By  careful  decanting  and  continual  shak 
ing,  we  can  remove  the  sand  and  particles 
of  rock,  and  retain  the  gold  as  a  matter  of 
course,  though  only  in  its  natural,  alloyed 
state. 

This  method  will  be  found  to  be  a  con- 
siderable improvement  on  the  washing  in 
pans.  If  the  ore  contains  iron  pyrites,  it 
is  best  to  calcine  it  first,  though  carefully, 
so  that  no  gold  is  carried  off  mechanically 
by  the  gases  formed. 


Ill 


X. 

Assay  of  Gold  by  Panning. 

THE  pan-test  is  a  process  of  concentration, 
the  product  being  either  gold  particles,  or 
gold  sulphides,  iron,  sand,  etc.,  depending 
on  how  far  the  process  is  carried. 

The  pan  used  for  the  purpose  is  a  sheet- 
iron  vessel  of  a  shallow  truncated  conical 
shape,  or  a  round  shallow  wooden  dish  with 
its  bottom  sloping  to  a  point  and  technically 
known  as  a  "  batea."  In  the  United  States 
experienced  miners  frequently  use  a  section 
of  a  bullock's  horn  as  a  substitute  for  the 
pan. 

The  ore  being  sampled,  crushed  and  pul- 
verized so  as  to  pass  through  a  50  or  60 
mesh  sieve,  the  requisite  amount  (3  to  15 
kilogrammes)  is  weighed  out  and  put  in 
the  pan,  which  must  be  free  from  grease. 


112  THE  ASSAYER'S  GUIDE. 

Now  moisten  the  ore  and  let  it  stand  for  a 
few  moments,  in  order  that  particles  may 
not  float  off  when  the  pan  is  put  in  water. 
When  wet  the  whole  pan  and  ore  is  gently 
sunk  below  the  surface  of  a  tank  of  water 
and  a  peculiar  oscillatory  motion  or  side 
vibration  is  commenced,  though  not  enough 
to  throw  any  particles  of  ore  over  the  edges 
of  the  pan.  The  object  of  this  is  to  settle 
the  heavier  particles  (the  free  gold,  heavy 
minerals,  black  sand,  etc.),  and  have  noth- 
ing on  the  surface  but  rock  or  quartz.  Then 
slightly  incline  the  pan,  and  so  wash  it 
around  as  to  carry  the  surface  rock  over  the 
edge ;  only,  however,  a  little  at  a  time. 
Level  the  pan  and  resettle  as  at  first ;  again 
incline  and  wash  more  over  the  edge.  Keep 
up  this  operation,  gradually  getting  more 
and  more  rock  over  the  edge,  and  becoming 
more  careful  and  washing  more  delicately 
as  the  process  continues. 

Toward  the  end  of  the  operation,  that  is, 
when  the  rock  is  nearly  gone,  be  careful  to 


ASSAY  OF  GOLD   BY   PANNING.  113 

keep  the  ore  under  the  surface  of  the  water, 
as  the  gold  might  otherwise  become  dry  and 
float  off.  Also  make  no  sudden  or  unusual 
lurch,  or  the  whole  result  may  go  off  the 
pan.  Dry  the  residue.  If  gold  alone  is 
obtained,  that  is,  gold  (or  gold  and  silver) 
free  from  sulphides,  etc.,  it  must  be  treated 
as  an  alloy,  weighed,  parted,  and  weighed 
again,  or  cupelled  with  lead,  weighed,  parted 
and  weighed ;  in  both  cases  giving  gold  and 
silver.  If  the  panning  is  not  carried  to 
such  a  point  as  to  get  rid  of  all  the  rock, 
the  concentration  is  all  scorified  with  test 
lead  (or  melted  down  in  a  crucible),  cupelled, 
parted  and  weighed.  In  the  case  of  an  ore 
supposed  to  carry  auriferous  sulphides,  it 
should  be  panned  so  far  as  can  safely  be 
done  without  losing  metalliferous  particles, 
and  the  concentration  treated  as  above  de- 
scribed. 

If  the  ore  is  quite  poor,  or  a  large  quan- 
tity is  desired   to  be  worked,  the  panning 


114  THE  ASSAYER'S  GUIDE. 

can  be  carried  on  roughly  and  the  successive 
concentrations  finally  panned  together. 

The  results  are  based  upon  the  amount 
of  ore  taken  in  the  pan.  As  an  example 
of  the  calculation,  the  following  is  given  : 

Weight  of  panful  of  ore,  21  kilogrammes 
=  2,250,000  milligrammes. 

Weight  of  bead  obtained,  gold,  20  milli- 
grammes; silver,  50  milligrammes; 

2,250,000  mgrms.  .  .  29166  x  =  25 


then 
and 


20  mgrms.  x  100  oz. 

2,250,000  mgrms.  .  .  29166  x  =  64 


50  mgrms.  x          100  oz. 

The  free  gold  can  be  separated  from  the 
sulphides  (if  it  is  desired  to  determine  how 
much  of  the  gold  is  "  free  "  and  how  much 
in  the  "sulphides")  by  washing  in  an 
amalgamated  pan.  Such  a  vessel  may  be 
simply  made  by  bending  a  piece  of  thin 
silver-plated  copper  (about  6x12  inches)  so 
as  to  form  curved  edges  on  three  sides,  the 
silvered  side  in.  The  side  not  turned  up  is 
one  of  the  narrow  ends.  A  little  mercury 


ASSAY   OF   GOLD    BY   PANNING.  115 

will  quickly  amalgamate  the  interior,  and 
if  the  ore  is  carefully  washed  over  this, 
most  of  the  free  gold  will  become  amalga- 
mated and  stick  to  the  pan.  A  piece  of 
chamois  skin  made  into  a  rubber  will  push 
the  gold,  which  can  be  seen  as  little  specks 
of  amalgam,  to  the  open  edge  of  the  pan 
and  into  a  crucible.  The  mercury  can  be 
driven  from  the  gold  by  heat. 

Kleinschmidt  gives  the  following  method 
of  assaying  gold  by  panning.  Five  kilo- 
grammes of  the  ore  to  be  assayed  are 
sampled,  crushed  and  pulverized  so  as  to 
pass  through  a  50  or  60  mesh  sieve,  any 
gold  remaining  upon  the  sieve  being 
weighed  separately.  Of  the  powdered  sam- 
ple passed  through  the  sieve,  500  grammes 
;ire  put  in  the  pan,  moistened  with  water 
and  mixed  with  5  grammes  or  more  of  mer- 
cury. After  standing  two  hours,  washing  is 
slowly  commenced  and  continued,  finally, 
with  the  addition  of  potassium  cyanide  solu- 
tion. The  cleansed  amalgam  is  gently 


116 

heated,  and  the  resulting  metal,  if  necessary, 
cupelled,  or  the  bead  parted. 

According  to  another  method  the  pulver- 
ized ore  is  put  in  a  porcelain  dish,  and  for 
some  time  mixed  with  mercury  by  means 
of  a  piece  of  amalgamated  silver  sheet. 
The  gold  amalgam  is  then  scraped  off,  and 
the  entire  amalgam  treated  with  nitric  acid, 
whereby  the  gold  remains  behind. 

In  Australia  1  kilogramme  of  gravelly 
gold  ore  is  dead-roasted,  the  roasted  sample 
triturated  in  an  iron  mortar  with  water  to 
a  stiff  paste,  and,  after  adding  one  table- 
spoonful  of  mercury,  the  mixture  is  rubbed 
together.  The  addition  of  mercury  and 
trituration  are  then  repeated,  and  after 
adding  hot  water,  soda  and  5  or  6  spoonfuls 
of  mercury,  the  whole  is  rubbed  together, 
washed  in  an  enamelled  dish,  collected  and 
the  amalgam  distilled,  whereby  80  to  90 
per  cent,  of  the  gold  which  can  be  brought 
out  by  the  fire-assay  are  obtained. 


117 


XI. 


Assay  of  Gold  by   Combined  Dry  and  Wet 
Methods. 

THE  object  of  these  assays  is  to  fix  the 
gold,  which  mostly  contains  silver,  on  lead 
(smelting  with  lead),  which,  after  cupella- 
tion,  gives  a  silver-gold  button,  to  be  fur- 
ther parted  by  the  wet  way  (quartation 
with  nitric  acid).  In  smelting  with  lead 
earthy  admixtures  are  scorified,  and  metal- 
lic sulphides  previously  converted  into  ox- 
ides by  oxidizing  agents  (lead  oxide,  air, 
saltpetre,  etc.). 

The  gold  being  very  unequally  distrib- 
uted in  the  ores,  special  care  must  be 
taken  to  obtain  a  correct  average  sample  of 
the  ore  to  be  assayed.  To  illustrate  the 
averaging,  take  a  quantity  of  ore  weighing 
about  fifty  pounds,  which  may  be  as  a 


118  THE  ASSAYER'S  GUIDE. 

single  lump,  or,  better,  the  result  of  the  se- 
lection of  samples  across  the  section  of  a 
vein.  With  a  sledge-hammer  break  up  the 
entire  mass  into  pieces  about  the  size  of  a 
walnut,  and  form  of  the  mass  an  oblong 
pile.  Then  divide  the  pile  in  halves  by 
means  of  a  large  spatula  or  piece  of  heavy 
sheet  brass.  Select  one  of  these  halves, 
and  break  up  the  pieces  constituting  it  still 
finer  to  the  size  of  a  hazelnut  or  less.  Mix 
the  pieces,  form  them  into  a  pile  and  halve 
as  before.  Continue  the  crushing,  mixing 
and  halving  until  about  one  pound  has 
finally  been  sampled  down.  Instead  of 
halving  the  piles  may  be  quartered,  and 
two  of  the  diagonally  opposite  quarters 
taken  as  a  half. 

The  next  step  is  to  pulverize  the  sample 
finally  obtained;  wet  or  damp  ores  must  be 
dried  before  pulverizing.  The  latter  may 
be  effected  by  means  of  an  iron  mortar  and 
pestle,  care  being  had  to  prevent  loss  due 
to  flying  particles  by  loosely  wrapping  a 


COMBINED   DRY   AND   WET   METHODS.      119 

piece  of  linen  around  the  pestle  and. across 
the  top  of  the  mortar.  Then  sift  the  pulver- 
ized sample  through  a  tin  box-sieve,  having 
80  to  100  meshes  to  the  linear  inch,  upon  a 
piece  of  brown  paper  or  a  zinc  sifting-pan. 

Assays  by  smelting  with  lead.  According 
to  the  nature  of  the  assay-sample  (poor  or 
rich,  with  free  gold,  with  earthy  or  gravelly 
admixtures),  there  is  used — 

a,  The  scarification  assay,  which  is  suitable 
for  every  kind  of  ore.  According  to  the 
supposed  content  of  gold  weigh  out  for  each 
assay  0.5  to  10  grammes  of  the  sample. 
With  poor  material  enough  assays  are  made 
that  the  gold-silver  button  resulting  from 
the  cupellation  of  all  the  lead  buttons 
weighs  0.2  to  0.5  gramme.  The  powdered 
ore,  according  to  whether  it  contains  metal- 
lic sulphides  or  only  earthy  constituents,  is 
charged  with  four  to  sixteen  times — on  an 
average  with  eight  times — the  quantity  of 
granulated  lead  free  from  silver.  The  ob- 
ject of  the  latter  is  to  absorb  the  gold  pres- 


120  THE  ASSAYER'S  GUIDE. 

ent,  for  which  it  has  great  affinity.  This 
is  most  readily  effected  by  the  presence  of 
metallic  lead  in  an  earthy  substance,  but 
with  more  difficulty  in  metallic  sulphides. 
The  latter  must  previously,  during  the  oxi- 
dizing melting,  be  oxidized  by  the  lead 
oxide  formed  and  converted  into  oxide. 
Since,  however,  the  different  metallic  sul- 
phides are  more  or  less  readily  completely 
oxidized  by  lead  oxide,  a  varying  addition 
of  lead  is,  according  to  their  quality,  re- 
quired. Thus,  for  instance,  galena  requires 
four  to  six  times,  iron  pyrites  nine  to  ten 
times,  zinc  blende  and  copper  pyrites  ten  to 
fifteen  times  the  quantity  of  assay-lead  of 
the  ore  weighed  out.  If  the  ore  contains 
only  acid  earthy  constituents  (quartz,  clay 
and  other  silicates),  they  are  dissolved  to  a 
slag  by  the  lead  oxide.  If  it  contains  basic 
earths  (lime,  magnesia,  etc.)  or  metallic 
oxides  produced  from  metallic  sulphides  in 
roasting,  acid  dissolving  agents  (bor  ,x- 
glass,  glass)  are  required,  the  quantity  of 


COMBINED   DRY    AXD   WET   METHODS.       121 

such  agents  being  dependent  on  the  quan- 
tity of  the  bases  to  be  scorified,  and  on  their 
refractoriness.  Lime  and  zinc  oxide  pro- 
duce special  refractoriness,  and  require  up  to 
50  per  cent,  or  more  of  the  ore  weighed  out 
of  fluxing  agents ;  oxides  of  iron  and  copper 
from  10  to  15  per  cent. 

The  assay  itself  is  executed  as  follows: 
Have  ready  cleaned  a  number  of  the  scori- 
fiers.  Number  or  tetter  each  scorifier  with 
reddle,  weigh  the  requisite  amount  of  granu- 
lated lead,  divide  it  in  halves  and  transfer 
one-half  to  the  scorifier.  Upon  it  place  the 
ore  and  mix  by  means  of  a  spatula.  Pour 
the  remaining  half  of  the  lead  evenly  over 
ttk}  surface  of  the  mixed  ore  and  lead,  and 
over  all  sprinkle  the  borax-glass.  A  charge 
frequently  used  is,  for  instance,  3.75 
grammes  ore,  30  grammes  lead  and  0.94 
gramme  borax-glass.  In  similar  manner 
charge  all  other  scorifiers. 

By  means  of  the  sconfier-tongs  place  the 
scorifiers  in  the  strongly-heated  muffle- 


122  THE  ASSAYER'S  GUIDE. 

furnace,  close  the  door  and  augment  the 
heat  (fifteen  to  twenty-five  minutes)  until 
the  surface  of  the  assays  is  smooth  without 
showing  un melted  portions  (period  of  hot 
working).  In  melting  the  lead  sinks  to  the 
bottom,  absorbing  thereby  the  greater  por- 
tion of  the  gold,  while  the  specifically  lighter 
substances  (earths,  sulphides,  borax)  pass 
to  the  surface,  where  they  at  first  remain 
tminelted.  With  the  increase  in  tempera- 
ture and  the  access  of  air,  which  should  not 
be  entirely  excluded,  the  metallic  sulphides 
are  oxidized,  partially  directly  by  the  air 
and  partially  by  the  lead  oxide  formed,  and 
the  oxides  together  with  the  earths  melt 
with  lead  oxide  and  borax  to  a  slag.  The 
latter,  however,  still  holds  metallic  sul- 
phides (oxysulphides)  as  well  as  particles 
of  gold  enclosed,  and  accumulates  on  the 
edge  of  the  scorifier.  The  door  of  the 
muffle  is  then  opened,  thus  admitting  a 
current  of  air,  the  fire  being  at  the  same 
time  decreased.  The  lead  now  oxidizes  in 


COMBINED   DRY   AND   WET   METHODS.      123 

larger  quantity,  and  its  oxygen  passes  over 
to  the  metallic  sulphides  in  the  slag  (period 
of  cold  working).  As  soon  as  the  slag 
covers  the  entire  surface  of  the  bath,  the 
process  is  finished,  because  a  further  access 
of  air  would  no  longer  act  upon  the  lead. 
Finally  close  the  door  of  the  muffle,  and 
increase  the  heat  for  a  minute  or  two  to 
fully  liquify  the  slag. 

Now  remove  the  scorifiers  from  the  muffle 
•  and  pour  their  contents  into  the  scorifica- 
tion-moulds,  which  should  be  warm  and 
painted  inside  with  chalk  or  reddle  wash. 
Cover  each  receptacle  of  the  moulds  with 
its  proper  scorifier  to  retain  its  identifica- 
tion. 

Instead  of  pouring  the  contents  of  the 
scorifiers  into  scorification-moulds,  the  lead 
buttons  may  be  allowed  to  cool  in  their 
scorifiers.  In  either  case,  however,  when 
cold,  detach  the  lead  buttons  from  their 
slags  and  hammer  each  button  into  a  clean 
cube  with  flattened  corners.  A  content  of 


124 

silver  in  the  ore  collects  with  the  gold  in 
the  lead. 

The  scorifiers  when  placed  in  the  hot 
muffle  and  taken  from  it  must  not  crack, 
and  should  be  perfectly  smooth  in  their 
interior,  so  that  the  corrosion  of  the  clay 
substance  by  the  lead  oxide  rnay  not  exert 
a  disturbing  effect. 

b.  Crucible  assay.  Melt  the  assay-sample 
together  with  fluxes  (potash,  soda,  borax, 
etc.),  lead  oxide  and  reducing  agents  "(coal 
dust,  colophony,  flour,  argol),  in  crucibles, 
whereby  the  earthy  constituents  are  scori- 
fied by  the  fluxes  and  a  portion  of  the  lead 
oxide,  while  another  portion  of  the  lead 
oxide  is  converted  by  the  reducing  agents 
into  metallic  lead  which  then  absorbs  the 
gold  (besides  the  silver).  These  assays 
have  the  advantage  of  being  more  accurate 
than  the  scorification- assay,  because  with 
the  availability  of  a  larger  quantity  of 
assay-substance  (25  to  50  grammes  or  more) 
the  losses  decrease,  and  furthermore  they 


COMBINED   DRY  AND  WET  METHODS.      125 

are  more  convenient  and  cheaper,  on  ac- 
count of  a  larger  number  of  assays  (fre- 
quently twenty  or  more)  not  being  required, 
which  has  to  be  taken  into  consideration, 
especially  with  very  poor  ore.  On  the 
other  hand,  they  are  chiefly  suitable  only 
for  earthy  ores  or  ores  containing  ferric 
oxide  and  products  containing  native  gold 
(gulch  gold,  dross  or  sweepings,  auriferous 
slags,  etc.).  They  are  less  adapted  for 
metallic  sulphides,  telluride  ores,  arsenical 
and  antimonial  ores.  The  latter  to  be  con- 
verted into  oxides  require  previous  roast- 
ing, because  by  melting  they  are  but  in- 
completely decomposed,  while  in  the  more 
suitable  scorification  process  they  suffer 
vigorous  oxidation. 

a.  Melting  earthy  gold  ores  or  gold  ores 
containing  ferric  oxide  (also  .dross  or  siceep- 
ings,  slags) .  Into  a  smooth  refractory  clay 
crucible  with  steep  sides  bring  10  grammes 
of  borax  and  10  grammes  of  argol,  next  20 
grammes  of  litharge  free  from  silver  and 


126  THE  ASSAYER'S  GUIDE. 

gold,  gently  breathe  upon  the  sides  of  the 
crucible  and  turn  the  crucible  around  until 
it  is  coated  f  of  its  height  with  litharge. 
Then  add  15  grammes  of  potash  and  25 
grammes  of  the  assay -substance,  mix  the 
whole  with  a  spatula,  add  a  cover  of  10 
grammes  of  soda,  then  one  12  millimeters 
thick  of  common  salt,  and  scatter  5  grammes 
of  litharge  around  the  walls  of  the  crucible. 

A  charge  for  American  gold  ore  con- 
sists, for  instance,  of  50  grammes  ore,  70 
grammes  anhydrous  soda,  100  to  120 
grammes  litharge,  and  6  to  8  grammes  coal 
dust.  First  mix  the  ore,  litharge  and  coal 
dust  by  themselves  and  then  with  the  flux, 
and  lay  in  the  crucible  a  piece  of  iron 
wire,  in  case  a  few  per  cent,  of  sulphur 
should  be  present. 

Or,  mix  500  grammes  of  very  pure  gold 
sand  with  SOO  grammes  potash,  200  grammes 
soda  and  50  grammes  borax  ;  scatter  upon 
the  mixture  20  grammes  of  granular  lead 
free  from  silver,  upon  this  a  thin  layer 


COMBINED   DRY   AND  WET   METHODS.       127 

of  soda,  and  finally  a  cover  of  common 
salt. 

The  crucible  thus  charged  is  slowly 
heated  in  the  air-furnace  until  no  more 
flames  of  carbonic  oxide  come  from  under 
the  lid  and  the  puffing  up  of  the  mass 
ceases.  The  heat  is  then  increased  for  10 
or  15  minutes  more  to  insure  complete 
fusion.  The  pasty  condition  of  the  mass, 
which  is  maintained  during  flaming,  pro- 
motes the  action  of  the  lead  upon  the 
gold.  The  crucible,  when  cold,  is  broken 
up,  the  lead  freed  from  slag  and  cupelled. 
If  great  accuracy  is  required,  several  assays 
(4  or  5)  are  made.  The  lead  buttons  ob- 
tained are  cupelled,  the  metallic  grains 
weighed,  and  those  best  agreeing  in  weight 
examined  as  to  their  content  of  gold  by  the 
wet  process. 

b.  Melting  of  sulphuretted  ores.  Ores 
with  a  larger  content  of  gold  are  brought 
into  sco rifiers  and  dead-roasted  in  the  muffle 
by  gently  heating  them  with  the  access  of 


.128 

air  until  a  sample  taken  from  the  muffle 
shows  no  odor  of  sulphurous  acid.  The 
slightly  slagged  mass  of  an  earthy  appear- 
ance is  then  broken  up  with  the  blade  of 
the  spatula,  rubbed  fine,  mixed  with  coal 
dust  and  again  heated,  with  the  access  of 
air,  in  the  muffle  until  the  coal  dust  is 
burnt. 

With  poorer  ores,  of  which  a  larger  quan- 
tity, for  instance,  0.5  kilogramme  or  more, 
has  to  be  used,  roasting  in  the  muffle  is 
effected  in  clay  boxes,  each  about  200 
millimeters  long,  70  to  90  millimeters  wide, 
and  40  to  50  millimeters  deep,  or  over  the 
coal  fire  of  an  air  furnace  by  placing  over 
it  a  clay-lined  piece  of  sheet-iron  turned  up 
on  the  edges,  or  a  clay  roasting-plate. 

The  charging  and  melting  of  the  roasted 
assay-sample  is  effected  in  the  manner 
above  described,  but  for  the  better  scorifica- 
tion  of  the  larger  amount  of  oxide,  the 
quantity  of  borax  is  somewhat  increased  or 
some  glass  added.  Another  charge  is,  for 


COMBINED    DRY   AND   WET   METHODS.       129 

instance,  as  follows  :  The  roasted  sample 
resulting  from  0.5  kilogramme  crude  ore, 
125  to  250  grammes  potash-glass  or  soda- 
glass,  125  grammes  black  flux,  or  250 
grammes  potash  and  32  grammes  flour,  then 
scattered  upon  it  0.5  kilogramme  of  grain- 
lead  free  from  silver,  with  a  protecting 
cover  of  common  salt.  Waste  from  amal- 
gamation containing  pyrites  is  melted,  with- 
out being  roasted,  with  fluxes  and  litharge 
without  reducing  agents.  By  the  content 
of  sulphur  in  the  pyrites  lead  is  then  re- 
duced from  the  lead  oxide,  the  former  ab- 
sorbing the  gold  and  silver.  If,  with  very 
poor  substances,  the  gold  alone  is  to  be  de- 
termined, four  assays  of  25  grammes  each 
are  made,  and  the  four  buttons  cupelled 
with  the  addition  of  silver,  so  that  the  re- 
sulting button  with  a  sufficient  content  of 
silver  can  be  at  once  submitted  to  quarta- 
tion.  Other  fluxes  for  dross  or  sweepings 
are,  4  parts  potash  and  1  part  flour,  or  13 
parts  potash  and  10  parts  soda  with  small 


quantities  of  borax  and  saltpetre.  Melt  for 
two  hours  in  a  Hessian  crucible,  flatten  out 
the  resulting  lead  button,  cut  it  up,  scorify 
the  separate  pieces  in  scorifiers  and  then 
concentrate  them  to  one  button,  which  is 
cupelled  and  parted.  Merrick  melts  lead 
buttons,  which  are  too  large  for  direct  cupel- 
lation,  in  a  capacious  Hessian  crucible,  adds 
one-half  the  quantity  of  the  weight  of  the 
button  of  saltpetre,  heats  to  a  white  heat, 
stirs  with  an  iron  wire,  and  then  takes  the 
crucible  from  the  furnace.  If  necessary 
the  operation  is  repeated,  and  even  pure 
gold  can  in  this  manner  be  obtained. 

c.  Gupellation  of  the  auriferous  lead. 
This  operation  consists  in  oxidizing  the  lead 
of  the  lead  buttons,  the  litharge  formed  by 
the  heat  being  partly  absorbed  by  the  cupel 
and  partly  driven  up  the  chimney,  leaving 
the  gold  and  silver  together  as  a  bead  upon 
the  surface  of  the  cupel.  Other  metals  that 
may  have  remained  in  small  quantity  from 
the  previous  operations  are  also  oxidized 


COMBINED   DRY   AND   WET   METHODS.      131 

and  thus  removed.  The  process  is  the  same 
as  for  silver  (which  see)  with  the  exception 
of  a  hotter  "driving"  towards  the  end  of 
the  assay,  so  that  no  litharge  remains.  If 
the  assay-sample  is  poor,  the  separate  lead 
buttons  are  either  entirely  cupelled  or  only 
partially.  In  the  latter  case  they  are 
wrapped  in  lead  foil  and  cupelled  together. 
The  resulting  gold  button  is  then  weighed, 
and,  in  case  it  contains  silver,  the  latter  is 
parted  by  means  of  nitric  acid. 

d.  Parting  the  gold  from  the  silver.  The 
button  after  weighing  is  flattened  a  little. 
For  parting  the  gold  from  the  silver  pure 
nitric  acid  free  from  chlorine  is  used.  The 
silver  under  certain  conditions  dissolves  in 
the  heated  acid,  but  not  the  gold.  Parting 
is  complete  only  when  at  least  2  2  parts  of 
silver  are  present  to  1  part  of  gold.  With 
a  smaller  content  of  silver  the  button  pos- 
sesses the  power  of  resisting  the  solvent 
action  of  nitric  acid.  The  metallic  grains 
resulting  from  actual  gold  ores  are  apt  to  be 


132 

richer  in  gold  than  in  silver,  whilst  those 
from  auriferous  silver  ores,  pyrites,  etc., 
generally  contain  only  i  to  £  gold.  Whilst 
the  latter  are  directly  subjected  to  the  treat- 
ment with  nitric  acid,  the  former  are  first 
again  cupelled  with  two  and  a  half  times 
the  quantity  of  silver  enfolded  in  a  small 
piece  of  sheet-lead.  If  the  gold  alone  is 
to  be  determined,  sufficient  silver  may  at 
once  be  added  when  cupelling  the  auriferous 
lead  button. 

To  judge  whether  silver  has  to  be  added 
or  not,  note, 

a.  The  color  of  the  button.  If  it  is  deep 
yellow,  two  and  a  half  to  three  times  the 
quantity  of  silver  will  have  to  be  added  ;  if 
pale  yellow,  twice  the  quantity ;  and,  if 
white,  once  the  quantity  or  none.  Or, 

P.  The  behavior  of  the  button  towards 
nitric  acid  of  1.19  specific  gravity  ivhen 
heated  in  a  small  flask.  If  the  laminated 
button  thereby  breaks  up  and  brown  flakes 
of  gold  are  separated,  sufficient  silver  (at 


COMBINED   DRY   AND   WET   METHODS.      133 

least  more  than  4  parts)  is  present  and  the 
operation  may  be  proceeded  with.  But  if 
the  laminated  button  does  not  break  up  and 
only  acquires  a  dark  coloration,  it  is  taken 
from  the  fluid,  rinsed  off,  dried,  cupelled  with 
two  and  a  half  times  the  quantity  of  silver 
and  some  lead,  and  parting  completed  with 
nitric  acid,  whereby  the  gold  remains  be- 
hind either  in  a  pulverulent  form  if  at  least 
4  parts  silver  are  present,  or  in  a  coherent 
state  with  2£  parts  silver  to  1  part  gold. 
When  no  more  nitrous  acid  is  developed 
heating  is  interrupted,  the  brown  lustreless 
gold  allowed  to  settle  and  the  liquid  care- 
fully decanted.  The  gold  is  now  washed 
twice  by  decantation  with  boiling  distilled 
water.  The  flask  is  then  entirely  filled 
with  cold  water  and  inverted  in  a  clay  cru- 
cible, or  a  small  porcelain  saucer,  and  when 
the  gold  has  dropped  into  the  crucible,  the 
flask  is  carefully  withdrawn  over  the  side. 
The  water  is  then  poured  off,  the  gold  dried, 
and  the  crucible  strongly  heated,  whereby 


134  THE  ASSAYER'S  GUIDE. 

the  powder  unites  to  a  coherent  mass  which 
is  weighed. 

To  recognize  with  very  poor  ores  whether 
the  small  black  specks  remaining  behind, 
when  treating  the  button  with  nitric  acid, 
are  gold,  allow  them  to  slide  from  the  flask 
into  a  small  porcelain  dish.  Then  carefully 
wash  them  first  with  water,  next  with 
alcohol  and  ether,  and  ignite,  whereby  with 
a  magnifying  glass  traces  of  yellow  shining 
metal  may  be  observed. 

Or,  dissolve  the  specks,  after  transferring 
to  a  test  tube  and  washing  in  aqua  regia, 
evaporate  to  dryness,  and  strongly  heat  the 
tube,  whereby  thin  yellow  rings  appear, 
which  may  be  recognized  either  with  the 
naked  eye  or  with  a  magnifying  glass. 

The  specks  may  also  be  transferred  to  a 
glass  plate  which  is  placed  under  a  micro- 
scope, and  after  pouring  a  few  drops  of  aqua 
regia  upon  it,  the  solution  is  observed,  a 
yellow  fluid  being  formed,  in  which  after 
evaporation  and  heating  yellow  gold  may 


COMBINED   DRY   AND   WET   METHODS.      135 

be  recognized.  The  smallest  quantity  of 
chloride  of  silver  of  various  colors,  especially 
violet,  can  be  recognized  in  the  gold  solution. 
A  black  speck  rubbed  in  an  agate  mortar 
shows  a  gold  color. 


XIL 

Assay  of  Gold  Ores  by  a  Wet 


ALTHOUGH  I  have  tried  to  make  it  a 
point  to  introduce  as  few  wet  processes  as 
possible  into  this  treatise,  I  now  venture 
to  give  directions  for  one  which  will  be 
found  very  available  to  ascertain  the  true 
amount  of  gold,  when  the  gold  has  been 
extracted  in  its  natural  state  by  the  last- 
given  methods.  It  is  characterized  by  the 
ease  with  which  it  can  be  performed. 

The  residue  of  alloyed  gold  produced  by 
washing  the  ore  or  sand  should  be  sub- 
mitted to  the  action  of  concentrated  aqua 
regia,  (consisting  of  from  three  to  four  parts 
of  muriatic  acid,  to  one  of  nitric,)  by  which 
all  the  gold  is  extracted.  All  the  plati- 
num, if  that  metal  be  present,  will  be  pre- 
cipitated as  below  from  this  liquid. 


'ASSAY  OF  GOLD  ORES  BY  A  WET  PROCESS.   1-7 

The  solution  should  then  be  filtered  off 
with  the  greatest  care,  water  being  after- 
ward poured  on  to  wash  the  insoluble 
parts,  and  to  procure  the  whole  of  the  dis- 
solved gold.  Sal-ammonia  is  then  to  he 
added,  and  if  causing  a  precipitate,  the  in- 
fusion filtered  again.  This  latter  is  then 
evaporated  to  dryness,  and  alcohol  of  O84 
specific  gravity  repeatedly  added,  and  after 
digesting  poured  off,  until  no  more  coloured 
by  the  dissolving  chloride  of  gold.  Iron 
vitriol  (copperas)  in  solution,  if  poured 
into  it,  will  precipitate  the  pure  gold  as  a 
brown  powder,  which  may  then  be  filtered, 
washed,  heated  to  redness,  and  weighed. 


XIII. 

Assay  of  Silver  Coins,  or  Alloys  of  Stiver  and 
Copper. 

As  a  matter  of  course,  with  these  alloys 
it  is  not  necessary  to  perform  the  operation, 
which  is  done  with  the  ores,  of  first  sepa- 
rating the  gangue-rock.  We  proceed  with 
the  cupellation,  as  soon  as  by  prior  tests  we 
have  ascertained  the  probable  amount  of 
silver  and  copper.  To  know  this  more 
accurately  no  method  exists,  except  a 
previous  hasty  cupellation,  though  to  a 
practised  assayer  it  is  cognisable  from  the 
greater  specific  gravity,  whiter  colour,  and 
increased  malleability  of  the  more  argen- 
tiferous alloys.  It  is  necessary  previously 
to  become  acquainted  with  this,  as  the 
quantity  of  lead  must  be  taken  accordingly. 
By  adding  too  much,  a  loss  of  silver  in 


ASSAY   OF  SILVER   C.INS. 


139 


incurred,  while,  if  too  little  is  used,  we  will 
not  be  able  to  procure  a  pure  silver  button, 
as  not  all  the  copper  will  pass  over  into  the 
litharge. 

The  table  to  regulate  the  requisite  quan- 
tity of  lead,  was  calculated  by  Erker. 
Still  later,  D'Arcet  arranged  another,  which, 
though  less  simple,  experience  has  shown 
to  be  no  more  accurate,  and  it  is  for  this 
reason  that  I  have  subjoined  the  former. 


32  parts  of  the  Alloy  containing 

Require  in 
parts  of 
Lead. 

Relative  quanti- 
ties of  Copper 
to  Lead. 

Parts  in  Silver. 

Parts  in  Copper. 

31 
30 
28 
24-26 
18-24 
8-16 
2-8. 

1 

2 
4 
8-6 
14-8 
24-16 
80-24 

128 

192 
256 
320 
448 
480 
512 

1        128 
1           96 

1       64 
1       40-53 
1       32-54 
1       20-30 
1       16-21 

From  this  table,  it  is  evident  that  the 
relative  amount  of  lead  should  decrease  as 
the  copper  increases,  although  the  nr>re 
copper  the  alloy  contains,  the  more  lead 
should  be  used. 


140  THE  ASSAYEK'S  GUIDE. 

The  only  way  to  pulverize  a  coin  or 
alloy  is  to  file  off  small  portions.  About 
a  gramme  or  fifteen  grains  of  the  filings 
should  be  carefully  weighed  off,  wrapped 
in  paper,  (satin  paper  is  the  best,  giving 
little  ashes,)  to  prevent  small  particles 
from  being  lost,  and  placed  in  the  muffle 
furnace  on  the  cupel,  fig.  2.  When  the 
paper  is  burnt  to  ashes,  the  lead  is  added 
according  to  the  table.  The  rest  of  the 
assay  is  exactly  as  with  silver  ores.  As 
long  as  lead  and  copper  are  being  oxidized, 
no  severe  heat  should  be  employed,  which 
is,  however,  done  as  soon  as  the  bright 
flash  appears. 

The  alloy  or  coin  may  also  be  treated 
according  to  Gay-Lussac's  process,  already 
described.  Having  thus  ascertained  the 
amount  of  silver,  we  are  easily  enabled  to 
calculate  that  of  the  copper,  by  subtraction, 


i« 


XIV. 

Assay  of  Gold  Coins,  or  Alloys  containing 
Oold,  Silver,  and  Copper. 

BEFORE  making  the  regular  assay,  it  is 
necessary  to  ascertain  the  probable  contents 
of  the  alloy,  as  with  silver.  The  method 
commonly  used  is  the  touchstone  or  besanite 
test,  the  same  employed  by  goldsmiths 
when  purchasing  coin  or  bullion.  A  dark 
fine-grained  basalt  or  siliceous  slate  is  re- 
quired, and  on  this  a  line  is  drawn  with  the 
gold  coin.  Those  whom  business  has  fre- 
quently brought  in  contact  with  such 
alloys  are  generally  able  to  judge  pretty 
accurately  by  this  alone,  as  the  purer  it  is, 
the  brighter  the  yellow,  silver  making  it 
whitish,  copper  of  a  redder  hue.  To  carry 
this  test  out  farther,  the  mark  is  moistened 
witb  an  acid,  which,  dissolving  the  baser 


142  THE  ASSATER'S  GUIDE. 

metals,  leaves  the  gold  in  its  virgin  state. 
This  acid  consists,  in  thousand  parts,  of 

784  parts  of  pure  nitric  acid,  of  1.340  specific  gravity, 

16     "      "     "     muriatic  acid,  of  1.173  spec.  grav. 
200     "     "     "     distilled  water. 

1000 

As  with  gold  ores,  several  assays  should 
be  made  at  once,  to  regulate  one  another. 
When  some  of  the  alloy  has  been  filed  off' 
— too  small  pieces  ought  not  to  be  taken, 
on  account  of  their  liability  to  be  blown 
away — the&e  particles  should  he  carefully 
brushed,  to  remove  the  fine  dust,  which 
might  otherwise  only  drop  off  after  weigh- 
ing, and  thus  cause  a  decided  loss. 

For  the  assays,  5  grains  are  used  in  each, 
and  the  value  of  the  gold  is  afterward  given 
in  carats  fine,  pure  gold  being  reckoned  at 
24  carats  fine.  In  this  way  an  alloy 
containing  91.666  per  cent,  of  gold  will  be 
22  carats  fine,  or  in  other  words,  it  contains 
S  or  jj  of  pure  gold  to  %  of  the  alloyed  metal. 


ASSAY   OF   GOLD   COINS.  14:3 

After  having  weighed  off  the  above 
quantity  of  the  gold  to  be  tested,  three 
times  the  weight  of  the  expected  amount 
of  gold,  as  ascertained  by  the  prior  inves- 
tigations, are  taken  in  pure  silver.  Some 
deem  two  and  a  half  sufficient.  The  gold 
and  the  silver  are  then  carefully  wrapped 
in  a  piece  of  paper. 

It  is  now  necessary  to  ascertain  the 
required  quantity  of  pure  lead,  which 
varies  according  to  the  per-centage  of  cop- 
per in  the  coin  or  alloy.  As  this  metal 
has  a  much  greater  affinity  for  gold  than 
for  silver,  it  is  much  more  difficult  to  sepa- 
rate it  from  its  alloys  with  the  former 
than  with  the  latter,  and  for  this  reason 
the  lead  used  should  be  about  twice  as 
much  as  would  be  necessary,  were  we 
assaying  a  coin  consisting  of  silver  and 
copper.  The  following  table  is  given  by 
D'Arcet  to  regulate  the  amount  to  be 
used : — 


144 


THE   ASSAYER  S    GUIDE 


If  the  contents  of  gold  in  the 

alloy  is 

The  quanti- 

Relative quantity 

ty  of  lead  re- 

of lead  to  the 

quired  is 

copper. 

In  1,000  parts. 

In  carats  fine. 

1.000 

24. 

1 

0 

0.900 

21.6 

10 

100.000  to  1 

0.800 

19.2 

16 

80.000  to  1 

0.700 

16.8 

22 

73.333  to  1 

0.600 

14.4 

24 

60.000  to  1 

0.500 

12.0 

26 

52.600  to  1 

0.400 

9.6 

34 

56.666  to  1 

0.300 

7.2 

34 

48.571  to  1 

0.200 

4.8 

34 

42.500  to  1 

0.100 

2.4 

34 

37.777  to  1 

As  with  silver  assays,  if  too  much  be 
employed,  it  will  produce  a  loss,  while  too 
little  would  not  extract  all  the  copper. 

The  lead  is  first  placed  in  the  cupel, 
(fig.  2,)  and  only  when  the  process  of  oxid- 
ation has  commenced,  is  the  paper  contain 
ing  the  gold  and  silver  to  be  added.  The 
rest  is  performed  exactly  as  with  gold  ores. 
The  button  should  be  hammered  to  a  very 
thin  sheet,  before  being  submitted  to  the 
nitric  acid;  and  to  do  this  well,  it  should 
be  perfectly  cold,  JIM  otherwise  marginal 


145 

cracks  are  often  produced,  which  again  may 
be  productive  of  loss. 

It  may  not  be  quite  out  of  place  here  to 
give  the  mint  units  and  the  content,  weight, 
etc.,  of  the  coins  of  various  countries. 

Mint -Units. 


Country. 

Miut-uiiit. 

Weight  in 
grammes. 

Fineness  of 
principal 
coins. 

Fine 
gold. 

Fine 
silver. 

Austria                 I 

Gold  gulden  

0.7258 

8.8217 
1.3725 

0.4032 
7.3224 

0.29 
0.3584 
0.29 
0.29 
0.29 
1.1997 

0.29 
0.066 

1.5046 

11.11 
22.5 

4.5 

4.5 
4.5 
4.5 

17.9961 
4.5 

0.998 

900 
900 
900 
900 
900 

900 
916.66 

900 
900 
900 
900 
900 
916  66 
868.05 
900   • 
900 
900 

900 

Brazil  
Chili                     I 

Silver  gulden.     .. 
Gold  milreis.. 
Peso  (gold)  
Peso  (silver). 

Krone 

Denmark,  Sweden 
and  Norway  
England  ,  

Pound    or    sove- 
reign..   

Franc  

France,  Belgium, 
Switzerland  
German  Empire... 
(j  reece 

10  marks 

Drachme 

Italy  
lioumaiiia  

Russia     ..           I 

Lira  
Lei  
Gold  rouble  
Silver  rouble  
Dinar    
Gold  piastre  
Silver  piastre  

Dollar  

Servia  
Turkey                | 

United   States  of 
North  America. 

JO 


146 


The  following  tables  show  the  content, 
weight,  etc.,  of  the  coins  of  various  coun- 
tries. 

Gold  Coins. 


Weight  Fineness 

Fineness 

Remedy 

Remedy 

Country. 

Coins. 

in 

in  thou- 

in 

in 

in 

gram'es. 

sandths. 

gram'es. 

weight. 

fineness. 

8  Gulden  .. 

6.4516 

900 

5.8065 

0.002 

0.002 

Austria...  * 

4 

3.2258 

900 

2.9032 

0.002 

0.002 

Dukaten... 

3.4909 

986.111 

3.4424 

0.00125 

0.00175 

100  Francs 

32.2518 

900 

29.0323 

0.001 

0.002 

50      " 

16.1290 

900 

14.5161 

0.001 

— 

France..  « 

20      " 

6.451d 

900 

5.8065 

0.002 

— 

10      " 

3.2258 

900 

2.9032 

0.002 

— 

5      " 

1.6129 

900 

1.4516 

0.003 



' 

20  Marks.. 

7.965 

900 

0.002 

_ 

German    J 

10      " 

3.9825 

900 



0.002 

_ 

Empire  j 

5      " 

1.9912 

900 

— 

0.004 

— 

f 

5  Sovereigns 

39.9403 

916.667 

36.6119 

0.002 

0.002 

Great 

2        " 

15.9761 

916.667 

14.6448 

0.002 

— 

Britain  1 

1  Sovereign 

7.9881 

916.667 

7.3224 

0.002 

— 

i        " 

3.9940 

916.667 

3.6612 

0.002 

— 

| 

£  Imperial 

6.5440 

916.667 

5.9987 

0.00679 

— 

Russia  ...  •{ 

Imperial 

( 

Dukat... 

3.9264 

916.667 

3.5992 

0.00566 

— 

f 

Double 

United 

eagle  

33.4363 

900 

30.0926 

0.000969 

— 

States  of 

Eagle  

16.7181 

900 

15.0463 

0.001938 

— 

North     ' 

i  eagle  

8.3591 

900 

7.5232 

0.001938 

— 

America,  i 

\  eagle  

4.1795 

900 

3.7616 

0.003876 

i 

1 

1  Dollar... 

1.6718 

900 

1.5046 

0.00969 

147 

Silver  Coins. 


Country. 

Coins. 

Weight 
in 
gram'es. 

Fineness 
in  thou- 
sandths. 

Fineness 
in 
gram'es. 

Remedy 
in 
weight. 

Remedy 
in 

fineness. 

2  Gulden  .. 

24.6914 

900 

22.222 

0.003 

0.003 

1        " 

12.3457 

900 

11.111 

0.004 

— 

i 

5.3419 

520 

2.7778 

0.010 

— 

Austria...  . 

20  Kreuzer 

2.6667 

500 

1.3333 

— 

— 

10       " 

1.6667 

400 

0.6667 

— 

— 

Maria-Theresa- 

Thaler... 

20.0668 

833.333 

— 





5  Francs... 

25 

900 

22.5 

0.003 

0.002 

2 

10 

835 

8.35 

0.005 

0.003 

France..,  , 

1 

5 

835 

4.175 

0.005 

0.003 

50Centimes 

2.5 

835 

2.0875 

0.007 

0.003 

20       " 

1 

835 

0.835 

0.010 

0.003 

German     1 

5  Marks... 

27.7778 

900 

25 

0.010 

0.003 

Empire 

2       " 

11.1111 

900 

10 

0.010 

0.003 

1 

5.5555 

900 

5 

0.010 

0.003 

50  Pfennig 

2.7778 

900 

2.5 

0.010 

0.003 

20        " 

1.1111 

900 

1 

— 

0.003 

Great 

1  Crown... 

28.2759 

925 

26.1552 

0.004 

— 

Britain 

i      " 

14.1380 

925 

13.0776 

0.004 

— 

1 

1  Shilling. 

5.6552 

925 

5.2310 

0.004 

— 

6  Pence.... 

2.8276 

925 

2.6155 

0.004 

— 

4      " 

1.8851 

925 

1.7437 

0.004 

— 

1  Rouble... 

20.  73  15  1  868.056 

17.9961 

0.00857 

— 

i      " 

10.3658  868.056 

8.9981 

0.01286 

— 

Russia  ...  - 

i      " 

5.1829  868.056 

4.4990 

0.01715 

— 

I'OKopecks    3.5992 

500 

1.7996 

0.01715 

— 

10      " 

1.7996 

500 

0.8998 

— 

— 

5 

0.8998 

500 

0.4499 

— 

— 

United    [ 

1  Dollar... 

27.2156 

900 

24.4940 

0.00357 

0.003 

States  of 

*        " 

12.5 

900 

11.25 

0.00714 

— 

North    •! 

i        " 

6.25 

900 

5.625 

0.01428 

— 

America. 

i       " 

5. 

900 

4.5  - 

0.01428 

— 

'        I 

1  Dime  

2.5 

900 

2.25 

0.03571 

~ 

148 

Base  Coins. 


Country. 

Coins.  • 

Weight 
in 
gram'es. 

Composition. 
Per  cent. 

Remedy 
in 
content. 

l! 

f 

4  Kreuzer 

134 

1 

Austria..  \ 

1        " 

.  3J 

[Cu 

1 

i        « 

1  & 

1 

15 

j 

lOCentimes 

10 

511 

5 

0.01  Cu 

0.01 

France  ..  - 

2u 

2 

95  Cu  4-4  Sn 

0.005  Sn 

0.01 

1       " 

1 

+  1  Zn 

0.005  Zn 

0.015 

German 

10  Pfennig 
5       " 

4 
2.5 

)    75  Cu  +  25  . 

Ni 

1  0.005  Ni 

0.05 

Empire  1 

2       " 

3.13 

1 

t  95  Cu  +4  Sn 
i 

0.05 

i 

1       " 

2 

J      +  1  Zn 

0.05 

_ 

1  Penny      9.4498     !p-r,1+4Sn 

Great    ! 
Britain   j 

£       «          5.6699 
1  Farthing  2.8349 

+  1  Zn 

5  Kopecks 

16.352 

1 

3 

9.820 

2        " 

6.532 

Russia...  . 

1 

3.244 

bronze 

i        " 

1.600 

i        " 

0.800 

j 

United     • 
States  of 
North   ' 

5  Cents 
3     " 

5 
1.944 

)  75  Cu  +  25 

j      Ni 

1  0.025 

0.039 
0.066! 

America  [ 

1      " 

3.944 

95  Cu  +  5  Sn 

- 

and  Zn 

0.044 

143 


XV. 

To  find  the  Proportion  of  Gold  in  a  mixture 
of  Gold  and  Quartz  ~by  Calculation* 

THE  specific  gravity  of  gold  =  19.000 
The  specific  gravity  of  quartz  =  2.600 
These  numbers  can  be  corrected  when 

experiment  shows  the  specific  gravities  to 

be  different. 

A.  Ascertain  the  specific  gravity  of  the 
mixture  of  gold  and  quartz.     Suppose  it  to 
be  8.067. 

B.  Deduct   the   specific   gravity  of  the 

*This  article  is  taken  from  J.  A.  Phillips's  "Gold 
Mining  and  Assaying,"  (London,  1852,)  p.  85,  a  work 
published  since  the  first  edition  of  this  little  volume, 
and  one  which,  like  the  other  productions  of  its  author, 
it  is  needless  more  particularly  to  recommend  to  those 
who  pay  attention  to  the  recent  publications  in  this 
department  of  applied  chemistry. 


150  THE   ASbAiEil'S    GUIDE. 

mixture  from  the  specific  gravity  of  the 
gold :  the  difference  is  the  ratio  of  the 
quartz  by  volume  : — 

19.000-8.067  =  10.933 

C.  Deduct   the   specific  gravity   of  the 
quartz  from  the  specific  gravity  of  the  mix- 
ture :  the  difference  is  the  ratio  of  the  gold 
by  volume: — 

8.067  -  2.600  =  5.467 

D.  Add  these  ratios  together,  and  pro- 
ceed by  the  rule  of  proportion.     The  pro- 
duct is  the  per-centage  of  gold  by  bulk  : — 

10.933  +  5.467  =  16.400 
16.4  is  to  5.467  as  100  is  to  33.35 

E.  Multiply  the  per-centage  of  gold  by 
bulk,  by  its  specific  gravity.     The  product 
is   the   ratio  of  gold   in   the   mixture   by 
weight : — 

33.35x19.00  =  633.65 

F.  Multiply  the  per-centage  of  quartz  by 
bulk,  by  its  specific  gravity.     The  product 


PROPORTIONS   OF   GOLD.  151 

is  the  ratio  of  the  quartz  in  the  mixture  by 
weight : — ^ 

66.65x2.60  =  173.29 

G.  To  find  the  per-centage  of  gold,  add 
these  ratios  together,  and  proceed  by  the 
rule  of  proportion  : — 

633.65  +  173.29  =  806.94 
806.94  is  to  633.65  as  100  is  to  78.53 

Hence,  a  mixture  of  quartz  and  gold, 
having  the  specific  gravity  of  8.067,  con- 
tains 78.53  per  cent,  of  gold  by  weight. 


152 


XVI. 
Assay  of  Platinum  Ores. 

THIS  metal  has  as  yet'  occurred  in  the 
United  States  only  in  gold  ores,  and  even 
then  in  the  merest  traces,  and  hence,  per- 
haps, it  would  barely  deserve  a  mention  in 
these  pages;  but  the  great  interest  attached 
to  its  occurrence,  as  so  rare  a  metal  all  over 
the  world,  and  its  useful  application  to 
chemical  purposes,  has  caused  me  to  insert 
some  rules  for  its  assay. 

If  the  ore  contain  platinum  in  no  larger 
amount  than  three  or  four  per  cent,  of  the 
gold,  the  former,  as  already  observed  in 
Article VII.,  on  quartation,  will  be  entirely 
dissolved  in  the  nitric  acid  used  on  ac- 
count of  the  silver.  From  this  solution  of 
the  two  metals  precipitate  the  silver  with 
common  salt,  or  muriatic  acid,  as  chloride 


ASSAY    OF   PLATINUM   ORES.  153 

of  silver;  filter  and  wash  until  the  water 
dropping  from  the  funnel  no  longer  con- 
tains any  of  the  platinum  solution.  This 
latter  evaporate  to  dryness,  after  adding 
sal-ammonia.  Wash  it  with  alcohol,  (see 
Gold,  art.  XII.)  and  heat  the  double  chlo- 
ride of  platinum  and  ammonium  to  red- 
ness, thus  producing  a  spongy  mass  of  pure 
platinum. 

If  there  be  more  than  three  or  four  per 
cent,  of  platinum  in  the  gold,  its  presence 
is  readily  perceived,  from  various  circum- 
stances :  thus,  in  evaporating  the  lead  a 
higher  temperature  is  necessary  than  is 
commonly  the  case,  to  make  the  metal  flow 
and  acquire  a  round  form ;  secondly,  the 
bright  light  cannot  be  observed;  thirdly, 
the  surface  of  the  button  is  crystalline  or 
rough,  and  when  large,  flat  and  quite  ir- 
regular, besides  looking  dull  and  having  a 
more  or  less  grayish  colour;  fourthly,  the 
nitric  acid  is  frequently  discoloured;  and 
fifthly,  the  little  roll  of  gold  is  not  of  a 


154  THE  ASSAYEL  s  GUIDE. 

pure  gold  yellow,  but  rather  inclining  to- 
wards steel  gray. 

After  having  thus  recognised  a  larger 
quantity  of  this  metal,  it  becomes  neces- 
sary, since  copper  is  frequently  present,  to 
make  a  prior  test,  to  ascertain,  by  cupella- 
tion,  the  amount  of  the  alloy  of  gold  and 
platinum.  After  that,  two  assays  should 
be  made;  the  one,  to  ascertain  the  exact 
conjoint  per-centage  of  the  two;  the  other, 
inquartation  (pure)  silver  being  added,  to 
discover  the  amount  of  the  gold  alone. 
The  difference  of  the  two  results  gives  the 
amount  of  platinum.  The  inquartation 
silver  should  not  be  more  than  from  two 
and  a  half  to  three  times  the  weight  of  the 
alloy  of  gold  and  platinum  ;  and  it  is  often 
well  to  add  a  certain,  accurately  weighed 
quantity  of  pure  gold  at  the  same  time,  so 
that  the  gold  may  afterward  be  procured 
m  one  connected  sheet  or  piece.  This 
ought  particularly  to  be  done,  when  there 
is  as  much  as  a  third  the  weight  of  the 


ASSAY   OP   PLATINtM   OftES.  155 

gold  in  platinum,  as,  for  instance,  in  the 
platinum  grains  of  the  Ural  Mountains, 
which  contain  about  80  per  cent.  The 
button  is  hammered  flat,  and  proceeded 
with  exactly  as  gold  ores,  the  platinum 
dissolving  with  the  silver  in  nitric  acid. 
But  as  it  does  not  do  so  as  easily  as  the 
latter,  at  least  when  in  large  quantities,  it 
is  necessary  to  repeat  the  process  from  the 
quartering  on  once  or  twice,  using  silver 
and  lead  over  again.  This  should  be  done 
until  nothing  but  the  silver  used  is  dis- 
solved in  the  nitric  acid,  or,  in  other  words, 
until  two  assays  following  one  another 
have  produced  the  same  results,  a  thing 
that  may  not  occur  until  the  fifth  time. 

It  should  be  remarked,  that  it  is  neces- 
sary to  add  a  little  more  lead  for  cupella- 
tion,  than  .would  be  done  if  no  platinum 
were  in  the  ore;  and  also,  that  just  before 
the  bright  flash  of  light  occurs  during  the 
operation  of  quartering,  it  is  well  to  shake 
the  cupel  a  little,  to  make  the  button 


156  THE  ASSAYER'S  GUIDE. 

stiffen,  as  soon  as  the  last  lead  has  entered 
the  former,  by  which  the  platinum  will  be 
more  regularly  distributed  in  the  alloy,  and 
cannot  so  well  collect  in  different  uncon- 
nected lumps,  unexposed  afterward  to  the 
action  of  the  acid.  The  platinum  may 
then  be  extracted  and  reduced  from  the 
solution  as  above. 

Electrolytic  assay  of  platinum.  Com- 
pounds of  platinum  are  decomposed  with 
the  greatest  ease  by  the  galvanic  current, 
with  the  deposition  of  the  metal  on  the 
negative  electrode.  A  current  of  two  Bun- 
sen  cells  produces  decomposition  so  rapidly 
that  the  platinum  separates  as  platinum 
black  and  cannot  be  determined.  If  one 
cell  is  used  it  separates  in  so  dense  a  form 
that  it  cannot  be  distinguished  from  ham- 
mered platinum.  It  is  possible,  in  this 
way,  gradually  to  deposit  considerable  quan- 
tities of  platinum  on  the  negative  electrode 
without  changing  its  appearance.  For  the 
determination  of  platinum  in  its  salts,  the 


ASSAY   OF   PLATINUM   ORES.  157 

solution  may  be  slightly  acidified  with  hy- 
drochloric acid  or  with  sulphuric  acid,  or 
treated  with  ammonium  or  potassium  oxal- 
ate,  gently  warmed  and  electrolyzed.  The 
platinum  separates  in  a  comparatively  short 
time.  For  example,  a  solution  of  platinum 
chloride  diluted  to  200  cubic  centimetres, 
containing  0.6  gramme  platinum,  deposited 
0.5  gramme  in  five  hours. 

Iridium  is  not  reduced  from  its  solutions 
by  a  single  Bunsen  cell.  This  fact  may  be 
used  for  the  separation  of  platinum  from 
iridium 


158 


XVII. 

Assay  of  Capper  Ores — German  and  HUM- 
garian  Method. 

THIS  ore,  if  a  sulphuret,  as  is  very  gene- 
rally the  case,  should,  after  having  been 
reduced  to  the  finest  possible  powder,  be 
submitted  to  the  process  of  roasting,  vul- 
garly termed  calcining.  For  this  purpose 
one  part  by  weight  of  the  ore  is  mixed 
up  with  one  fifth  of  graphite,  (black-lead,) 
which,  consisting  of  carbon  in  a  more  con- 
densed state  than  that  element  occurs  in 
charcoal,  is,  therefore,  so  much  the  more 
effectual  in  driving  off  the  sulphur.  This 
mixture  of  the  two  should  be  exposed  to 
an  intense  red-heat  in  the  cupel,  (fig.  1,) 
(painted  over  on  the  inside  with  red  chalk, 
or  Spanish  red,  to  prevent  adhesion,)  for 
about  twenty  minutes,  after  which  it  is 


ASSAY   OF    COPPER   ORES.  159 

to  be  taken  out,  and  stirred  up  with  a  small 
iron  ladle  to  expose  the  unburnt  parts  of 
graphite,  when  it  should  again  be  exposed 
in  the  muffle.  In  about  a  quarter  of  an 
hour  we  take  it  out  again,  pound  it  over, 
for  the  mass  is  generally  clogged,  and  mix 
it  with  about  twice  its  weight  of  charcoal- 
dust,  after  which  we  continue  the  roasting 
for  about  one-half  to  a  full  hour,  according 
as  the  ore  contains  a  little  or  much  sul- 
phur, vapours  of  which  may  be  seen  rising 
during  the  whole  of  this  process. 

After  this  the  ore  has  a  reddish,  or  what 
is  generally  called  a  ferruginous  colour, 
and  we  now  take  it  from  the  first  crucible, 
and  introduce  it  into  that  represented  in 
fig.  4,  Plate  II.,  or  if  not  in  possession  of 
such,  into  a  Hessian  crucible,  fig.  5,  on  the 
same  plate.  For  this  purpose,  however, 
some  Hack  flux  should  be  provided.  It 
consists  of  carbonate  of  potash  and  lime, 
and  is  made  by  igniting  together  one  part 
by  weight  of  saltpetre,  and  two  of  rural- 


160  THE  ASSAYER'S  GUIDE. 

mon  tartar.  The  flux  produced  should  be 
kept  carefully  corked  to  prevent  the  ab- 
sorption of  hygroscopic  water.  It  is  still 
better  to  make -it  only  when  required  for 
immediate  use. 

If  the  ore  is  poor,  one  tenth  part  by 
weight  of  oxide  of  antimony,  (antimonious 
acid,)  or  of  arsenic,  (arsenious  acid,)  or  if  it 
is  richer,  fifteen  per-cent.  of  pure  lead*  are 
requisite,  as  will  hereafter  be  seen  to  make 
the  particles  of  copper  unite.  One  of  these 
together  with  three  parts  of  black  flux,  one 
half  the  weight  in  borax,  and  two  parts  of 
table  salt,  must  then  be  added  to  the  roast- 
ed ore,  though  none  except  a  part  of  the 

*  Some  assayers  use  neither  of  these  three,  on  the 
ground  that  the  arsenic,  as  occasionally  even  40  per- 
cent, may  be  taken,  is  very  difficult  to  separate  from 
the  copper,  and  that  the  antimony  may  unite  with  part 
of  the  same,  forming  an  antimoniate.  They  therefore 
only  employ  borax  and  black  flux,  in  about  the  same 
proportions,  however,  as  given  above.  It  is  hard  to 
say  which  is  best,  and  it  must  be  left  to  the  discretion 
and  experience  of  the  assayer  to  act  as  may  be  most 
suitable  co  his  peculiar  ores 


ASSAY   OF    COPPER    ORES.  161 

flux  are  mixed  with  the  mineral  now  in- 
vestigating. The  salt  is  merely  used  to 
form  a  crust  over  the  whole.  When  all 
have  thus  been  placed  in  the  crucible,  they 
are  covered  over  with  a  piece  of  charcoal, 
cut  to  match  the  size  of  the  vessel ;  after 
which  the  cover  is  put  on.  We  then  ex- 
pose it  to  a  white-heat  for  about  one-half 
to  one  full  hour,  as  may  be  most  conve- 
nient, either  in  the  draught  furnace,  fig.  6, 
Plate  I.,  or  in  the  muffle  furnace;  in  which 
latter  case,  we  must  allow  the  longest 
period  of  time. 

The  carbon  of  the  flux  is  intended  to 
reduce  the  peroxide  of  copper  produced  by 
roasting,  while  its  carbonate  of  potash 
unites  with  the  earthy  contents  of  the  ore 
and  the  oxides  of  other  metals  present, 
such  as  iron,  which  would  otherwise  also  be 
reduced  to  their  metallic  state.  With  these 
it  forms  a  slag,  the  borax  being  added  to 
make  it  flow  easy,  and  allow  the  copper  to 

collect  in  one  button. 

11 


162 

On  cooling,  we  break  open  the  crucible, 
and,  on  removing  the  slag,  extract  a  spheri- 
cal piece  of  impure  or  alloyed  copper, 
according  as  other  metals  may  chance  to 
occur  in  the  ore.  If  any  intermediate 
crust  should  have  formed  between  the 
button  and  the  slag,  the  ore  was  not  proper- 
ly roasted,  a  part  of  the  copper  not  reduced, 
and  consequently  the  assay  is  worthless. 

In  a  good  assay  the  slag  should  be  black 
and  vitreous  in  appearance,  never  of  an 
earthy  texture.  If  striated  or  speckled 
with  red,  we  may  know  that  protoxide  of 
copper  is  dissolved  in  it,  and  again  that  the 
whole  cannot  be  productive  of  an  accurate 
result.  Much  attention  is  required  during 
this  test,  and,  as  already  mentioned  under 
the  heads  of  silver  and  gold,  the  final  result 
depends  entirely  upon  the  care  taken  by 
the  assayer.  If  well  managed,  however,  as 
here  directed,  he  can  hardly  fail  to  be  suc- 
cessful. 

The   button,   as   remarked   above,   may 


ASSAY  OF   COPPER   ORES.  163 

vary  in  purity.  It  generally  contains  some 
iron,  and  (since  these  metals  frequently 
exist  in  copper  ores)  lead,  bismuth,  tin, 
cobalt,  nickel,  antimony,  and  arsenic — the 
latter  two  in  particular,  if  they  were  added 
in  the  process  of  reduction.  Thus  it  very 
rarely,  if  ever,  happens,  that  a  copper  ore 
is  sufficiently  pure  to  require  no  third 
process.  The  less  admixtures  the  alloy  con- 
tains, the  less  brittle  and  the  more  ductile  it 
is.  Nickel  particularly  tends  to  harden  it. 

To  remove  the  foreign  metals,  the  button 
is  put  in  a  piece  of  paper,  with  sufficient 
borax  to  cover  it,  (one-fourth  to  one-third 
part  by  weight,  rather  more  than  less,)  and 
if  no  lead  occur  in  the  ore,  with  about  from 
live  to  ten  per-cent.  of  that  metal,  which 
amount,  however,  should  increase  up  to 
forty,  or  even  more,  if  there  are  many 
impurities  in  the  alloy.  Even  if  this  be 
not  the  case,  it  is  always  safer,  and  can 
never  produce  any  bad  effect,  to  add  much. 

A  crucible  of  the  kind  illustrated  in  fig.  3, 


164  THE  ASSAYER'S  GUIDE. 

Plate  II.,  should  be  brought  to  a  bright 
white-heat  in  the  muffle.  Coals  may  be 
placed  round  to  increase  the  temperature, 
which  should  be  so  great,  that  the  copper, 
on  being  introduced,  wrapped  in  paper  with 
borax  and  lead,  may  melt  in  a  few  minutes. 

As  long  as  the  tongs  held  over  the  button 
are  reflected,  or  rainbow  colours  are  yet 
seen  to  flicker  over  its  surface,  lead  is  still 
present.  As  with  silver  and  gold,  too  great 
heat  ought  not  to  be  employed.  When  the 
lead  has  left,  we  immediately  take  out  the 
crucible,  and  immerse  it  in  water,  to  pre- 
vent any  copper  from  oxidating  unneces- 
sarily. The  button  of  pure  copper  is  then 
broken  out  and  weighed.  A  slight  loss  can- 
not be  prevented,  as  it  is  impossible  to  pre- 
vent some  oxide  of  copper  from  being  formed, 
and  we  must  therefore  grant  a  larger  per- 
centage than  the  assay  would  direct. 

At  least  two  assays  should  be  made  at 
once,  to  compare  the  results,  and  take  the 
average. 


165 


XVIII. 
At&ay  of  Capper  Ores — English  Method. 

AT  the  copper  mines  in  Cornwall,  a  mode 
of  assaying,  is  employed,  which  in  several 
of  its  minutiae  differs  considerably  from  the 
one  just  described.  It  should  be  remarked 
that  this  method  is,  properly  speaking,  ouly 
applicable  to  sulphurets,  as  all  copper  con- 
tained in  the  ore  as  a  pure  oxide,  or  com- 
bined with  an  acid,  will  pass  over  into  the 
slag  during  the  reduction  process ;  and  that 
therefore  if  these  latter  are  present,  some 
means  should  be  employed,  as  shall  be 
shown  hereafter,  to  extract  them  from  the 
slags,  when  the  other  parts  of  the  assay  are 
concluded. 

The  ore,  being  a  sulphuret,  should  be 
roasted  as  directed  in  the  foregoing  Ger- 
man or  Hungarian  method,  after  which  it 


166  THE  ASSAYER'S  GUIDE. 

is  mixed  with  from  one  to  one  and  a  half 
parts  of  pounded  glass,  which  should,  how- 
ever, contain  no  lead  or  arsenic,  from 
twenty-five  to  fifty  per-cent.  of  saltpetre, 
and  fifty  per-cent.  of  borax.  Together  with 
these,  it  is  exposed  to  a  strong  melting  heat 
in  a  clay  crucible.  On  cooling,  the  button 
is  removed,  as  is  the  case  in  the  other  mode  t 
of  procedure,  more  common  on  the  conti- 
nent of  Europe. 

Having  thus  reduced  the  copper,  it  is  ne- 
cessary to  purify  it,  as  was  also  done  in  the 
other  assay.  I  must  observe,  however, 
that  this  part  of  the  Cornwall  process, 
again,  can  only  be  applied  where  very 
little  lead  is  contained  in  the  copper  ore. 

For  this  purpose,  some  white  flux  should 
be  prepared,  which  is  done  by  igniting  to- 
gether equal  parts  of  saltpetre  and  tartar. 
Being  as  susceptible  to  the  effects  of  atmo- 
spheric moisture  as  black  flux,  it  requires 
the  same  precaution  as  regards  its  preser- 
vation. 


ASSAY   OF   COPPER    ORES.  167 

The  button  of  copper  alloy  is  then  ham- 
mered out  flat,  to  a  sheet  as  thin  as  it  will 
allow  of,  without  breaking.  It  is  then  ex- 
posed in  a  crucible,  (fig.  3,)  already  red- 
hot,  and,  as  soon  as  it  melts,  covered  with 
white  flux.  Some  table-salt,  from  which 
the  water  of  crystallization  has  been  re- 
moved by  heat,  is  frequently  added  to  give 
a  covering  and  protect  the  copper  from  too 
immediate  contact  with  the  atmosphere, 
which,  together  with  the  heat,  would  un- 
avoidably create  a  free  oxidation.  A  con- 
siderable ebullition  is  produced,  on  the  sub- 
siding of  which,  and  when  therefore  the 
mass  flows  quietly,  the  contents  of  the  cru- 
cible are  poured  into  an  iron  mould,  (fig.  6, 
Plate  II.,)  greased  over  beforehand,  from 
which  the  mass  should  be  removed  with  a 
pair  of  tongs,  as  soon  as  sufficiently  consoli- 
dated, to  be  dipped  in  water,  which  ena- 
bles us  to  separate  the  slag  from  the  copper 
with  greater  ease.  The  purity  of  the  latter 
is  known  by  its  malleability,  and  by  it« 


168  THE  ASSAYER'S  GUIDE. 

not  cracking  much  at  the  margin,  when 
stretched  on  the  anvil  under  the  blows  of  a 
hammer.  Should  this  test  prove  its  yet 
uncleansed  state,  it  ought  again  to  be  sub- 
mitted to  the  operation  just  concluded. 
Sometimes  it  is  necessary  to  repeat  this 
several  times. 

It  has  already  been  mentioned,  that,  par- 
ticularly when  not  all  the  copper  in  an 
ore  is  contained  in  the  shape  of  a  sulphu- 
ret,  it  is  impossible  to  prevent  some  of  this 
metal  from  escaping  into  the  slag;  and 
therefore,  to  diminish  this  loss  as  much  as 
possible,  English  assayers  collect  the  slags, 
both  of  the  reducing  and  of  the  purifying 
processes,  and,  pounding  them  up  together, 
mix  them  with  an  equal  quantity  of  tartar 
and  some  powdered  coke. 

This  mixture  is  then  melted  in  a  Hessian 
crucible,  after  being  covered  over  with  com- 
mon salt.  The  little  button  produced  in 
this  way  is  of  course  impure,  and  requires 
the  same  treatment  as  the  larger  one,  origi- 


ASSAY   OF   COPPER    ORES.  1GO 

nally  procured.  This  second  button  Is 
weighed  together  with  the  large  one,  and 
the  result  will  givp  vpry  accurately  the 
per-centage  of  coppei  m  cne  ore. 


XTX. 

Wet  Assay  of  Copper. 

ON  account  of  its  greater  accuracy  and 
simpler  execution,  the  wet  method  has,  as  a 
general  rule,  been  substituted  for  the  dry 
assay  of  copper. 

Modified  Swedish  assay.  The  cuprifer- 
ous substance  is  brought  into  solution  with 
sulphuric  or  hydrochloric  acid  (nitric  acid 
must  not  be  used,  as  the  precipitated  copper 
is  again  dissolved  in  it),  and  the  copper  pre- 
cipitated with  iron  or  zinc,  and  determined 
either  as  metal  or  oxide.  This  plan  is  not 
admissible  in  the  presence  of  metals  which 
are  also  precipitated  by  iron  and  zinc. 

Such  metals,  however,  can  be  removed 
during  the  operation  without  injurious  effect 
by  igniting  the  precipitated  copper,  or  by  a 
preparatory  roasting  at  not  too  high  a  tern- 


WET   ASSAY   OF   COPPEIl.  171 

perature  of  the  assay-sample,  first  by  itself, 
and  then  with  the  addition  of  some  iron  py- 
rites. Tin  and  antimony  are  removed  by 
heating  with  moderately  diluted  sulphuric 
acid,  then  adding  nitric  acid,  and  heating 
nearly  to  boiling.  If  necessary,  as  in  the 
oase  of  metallic  sulphides,  a  few  drops  of 
fuming  nitric  acid  are  added.  The  solu- 
tion is  then  evaporated  to  dryness  until  the 
fuming  ceases.  The  dry  mass  is  dissolved  in 
hot  water  and  filtered,  and  the  solution  treated 
with  some  hydrochloric  or  nitric  acid,  etc. ; 
or,  the  antimony  is  removed  by  fusing  the 
assay-sample  with  potassium  hydrate  or 
potassium  carbonate  in  a  silver  crucible, 
lixiviating  the  potassium  antimoniate  and 
dissolving  the  residue ;  or,  the  assay-sample 
is  dissolved,  neutralized  with  soda,  and  di- 
gested with  a  solution  of  sodium  sulphide 
to  extract  the  antimony,  arsenic  and  tin  in 
soluble  form.  It  is  now  filtered,  and  the 
residue  washed  and  dissolved  as  above. 
Ores  containing  bitumen,  for  instance,  cupri- 


172  THE  ASSAYER'S  GUIDE. 

ferous  schists,  must  be  ignited  to  remove  the 
bitumen,  before  they  are  dissolved. 

a.  Precipitation  with  iron.  Into  a  suit- 
able flask  placed  in  an  oblique  position  bring, 
according  to  the  richness  of  the  ore,  1  to  5, 
generally  2.5  to  5,  grammes  of  the  assay- 
sample,  and  decompose  them  by  heating 
with  sulphuric  acid,  adding  from  time  to 
time  some  fuming  nitric  acid  or  potassium 
chlorate,  until  the  separated  sulphur,  in- 
closing particles  of  the  ore,  is  oxidized  as 
much  as  possible.  Or,  the  sample  is  at  once 
dissolved  in  aqua  regia.  It  is  then  evapo- 
rated to  dryness  with  some  sulphuric  acid,  or 
until  the  sulphuric  acid  vapors  appear  in 
the  flask.  To  dissolve  the  basic  salts,  add  a 
few  drops  of  sulphuric  acid  to  the  dry  mass 
and  then,  cautiously,  water.  The  fluid, 
which  is  now  entirely  free  from  nitric  acid, 
is  filtered  into  a  flask,  and  the  residue 
washed  until  the  wash-water  no  longer  pro- 
duces a  red  stain  upon  a  piece  of  bright 
sheet- iron.  Two  pieces  of  iron  wire,  3  to 


WET   ASSAY   OF   COPPER.  173 

4  centimeters  long,  are  then  added ;  or,  to 
shorten  the  time  required  for  the  assay,  the 
fluid  may  at  once  be  filtered  into  a  porcelain 
dish  in  which  the  iron  wires  lie,  and  copper 
will  then  be  precipitated  during  filtration. 
The  filtrate  is  then  sufficiently  diluted  and 
gently  heated  until  a  pointed  iron  wire 
dipped  into  the  fluid  does  not  show  a  red- 
dish stain  of  copper.  To  prevent  the  sepa- 
ration of  basic  iron  salts,  which  are  more 
readily  formed  by  hot  water,  the  copper  is 
twice  decanted  with  cold  water  into  a  spa- 
cious beaker  and  then  three  times  with 
boiling  water.  The  flask  is  then  completely 
filled  with  cold  water,  and  a  flat-bottomed 
porcelain  dish  about  20  millimeters  high 
and  80  millimeters  in  diameter  is  placed 
bottom  upwards,  on  top  of  it.  The  flask 
and  dish  are  then  inverted.  The  mouth 
of  the  flask  is  held  in  an  oblique  position, 
and  the  water  allowed  to  run  into  the 
dish  until  it  is  nearly  full.  The  flask 
is  left  standing  in  the  dish  until  all  the 


174  THE  ASS  AVER'S  GUIDE. 

copper  and  the  iron  wires  have  falter  Ir.co 
the  water  in  the  dish.  Small  particles 
of  carbon  separated  from  the  iron  will  re- 
main floating  on  the  water  for  some  time. 
The  flask  is  then  gently  removed  by  draw- 
ing it  over  the  side  of  the  dish,  which 
should  be  somewhat  inclined  for  the  pur- 
pose. The  iron  is  freed  from  copper  by 
rubbing  with  the  fingers,  which  should  be 
rinsed  off  in  the  water.  The  copper  is  now 
decanted  twice  with  boiling  water.  This  is 
poured  off  as  completely  as  possible  from 
the  copper,  which  is  moistened  with  abso- 
lute alcohol,  and  dried  on  the  water-bath 
until  it  has  assumed  a  pulverulent  condition. 
It  is  allowed  to  cool  in  the  desiccator,  and  is 
then  brought  upon  the  pan  of  the  balance, 
or  into  a  tarred  porcelain  crucible  with  the 
aid  of  a  fine  brush,  and  quickly  weighed. 
It  is  now  dried  for  10  or  15  minutes  more, 
and  again  weighed  until  the  results  agree ; 
o?',  the  copper  is  spread  out  upon  a  roasting 
dish  and  ignited  in  the  muffle  furnace,  and 


WET  ASSAY   OF  COPPER.  175 

the  metal  calculated  from  the  amount  of 
cupric  oxide  formed .  (100  cupric  oxide  = 
79. 88 copper).  If  the  water  used  in  decanta- 
tion  shows  a  reddish  sediment,  it  should  be 
filtered,  the  filter  dried  and  ignited  upon  the 
scorifier,  and  the  percentage  of  copper  re- 
sulting from  the  cupric  oxide  should  be 
added  to  the  principal  yield. 

Correction  for  iron  that  may  be  contained 
in  the  precipitated  copper  on  account  of  a 
deposit  of  basic  iron  salts :  The  precipitated 
copper  is  ignited  upon  the  scorifier  until  it 
becomes  black.  The  cupric  and  ferric  ox^ 
ides  formed  are  weighed  and  dissolved  in 
hydrochloric  or  sulphuric  acid.  The  ferric 
oxide  is  precipitated  with  ammonia.  The 
solution  is  filtered  upon  a  small  filter  of 
paper.  The  filter  is  dried  and  ignited,  and 
the  ferric  oxide,  which  may  be  found,  is  de- 
ducted from  the  combined  weight  of  the 
cupric  and  ferric  oxides,  and  the  copper  cal- 
culated from  the  quantity  of  pure  cupric 
oxide  found.  Instead  of  decanting  the  pre- 


176  THE  ASSAYER'S  GUIDE. 

cipitated  copper,  it  may  all  be  filtered,  dried, 
ignited,  weighed,  and  dissolved,  as  above, 
for  obtaining  the  content  of  iron. 

Pare  precipitated  copper  has  a  fine  copper 
color.  If  the  solution  contains  antimony 
and  arsenic,  it  has  first  a  copper  color  which 
later  on,  by  the  antimony  and  arsenic  being 
precipitated,  changes  to  black.  The  larger 
portion  of  the  antimony,  after  the  precipi- 
tate has  been  evaporated  to  dryness  with 
sulphuric  acid  and  again  moistened  with 
water,  remains  as  basic  sulphate  of  anti- 
mony, while  arsenic  passes  into  solution. 
The  residue  from  the  solution  of  the  ore, 
etc.,  is  tested  for  copper  by  heating  it  with 
nitric  acid,  filtering,  and  adding  ammonia 
in  excess.  The  appearance  of  a  blue  color 
indicates  copper. 

Instead  of  two  iron  wires,  a  single  wire 
bent  into  the  form  of  a  ring,  with  one  end 
projecting  vertically,  may  be  used.  The 
ring  is  dipped  into  the  liquid  in  the  beakei 
glass  so  that  the  end  projects.  When  pre- 


WET  ASSAY  OF  COPPER.  177 

cipitation  is  complete,  the  copper  is  rinsed 
from  the  ring,  decanted,  etc.,  as  above.  Or, 
a  strip  of  sheet-iron  may  be  used  in  place 
of  the  wire,  but  it  must  be  immediately  re- 
moved from  the  liquid  after  the  precipita- 
tion of  the  copper  is  complete  to  avoid  the 
formation  of  basic  iron  salts.  In  solutions 
that  are  too  concentrated,  the  copper  ad- 
heres too  strongly  to  the  iron. 

b.  Precipitation  with  zinc  free  from  lead 
and  arsenic.  Prepare  a  solution  of  the  as- 
say-sample with  sulphuric  acid,  as  above 
described,  and  filter.  Then  place  a  strip  of 
zinc  in  the  solution  and  heat  until  a  bright 
iron  wire  held  in  it  shows  no  copper  de- 
posit; or  until  a  drop  of  the  solution  placed 
upon  a  porcelain  dish  is  not  browned  by 
sulphuretted  hydrogen.  The  strip  of  zinc 
is  then  taken  out,  and  the  precipitated  cop- 
per washed  off  with  the  wash  bottle.  It  is 
next  filtered  until  but  a  small  layer  of  water 
covering  the  copper  remains.  A  few  drops 

of  warm  hydrochloric  acid  are  then -added 
12 


178  THE  ASSAYER'S  GUIDE. 

to  dissolve  any  particles  of  zinc  which  ma;y 
be  present.  It  is  now  decanted,  etc.,  as  in 
the  precipitation  with  iron ;  or  it  is  filtered 
as  soon  as  effervescence  ceases,  quickly 
washed  with  hot  water,  and  dried.  The 
copper  is  then  detached  from  the  filter, 
ignited  on  the  cover  of  a  porcelain  or  plati- 
num crucible,  or  upon  a  roasting  dish  in 
the  muffle  and  the  oxide  quickly  weighed 
The  black  crust  upon  the  end  of  the  piece  of 
zinc,  which  has  been  dipped  into  the  fluid, 
is  a  spongy  layer  of  zinc  colored  by  a  trace 
of  sulphide  of  copper.  Nickel,  which  is  not 
thrown  down  by  iron,  is  precipitated  with 
zinc,  but  cobalt  is  not. 

Granulated  zinc  may  be  used  instead  of 
a  strip,  but  the  granules  must  be  completely 
dissolved  by  the  time  the  bubbles  cease. 
The  copper  is  then  decanted,  etc.  The 
cupriferous  fluid  may  be  filtered  into  a 
platinum  dish,  and  some  hydrochloric  acid 
added  to  it.  Now  heat  and  add  a  few  small 
pieces  of  zinc,  whereupon  the  copper  will. 


WET  ASSAV   CF  COPPER.  179 

firmly  deposit  itself  on  the  platinum,  but 
loosely  on  the  zinc.  After  precipitation  is 
complete,  which  is  ascertained  by  testing 
with  sulphuretted  hydrogen,  as  above,  the 
copper  is  rubbed  and  washed  off  from  the 
zinc.  It  is  then  allowed  to  settle,  decanted, 
treated  with  hot  water,  to  which  some 
hydrochloric  acid  has  been  added;  then 
quickly  washed  with  hot  water  by  decanta- 
tion  to  prevent  the  loss  of  copper  by  solu 
tion.  It  is  finally  moistened  with  absolute 
alcohol  dried  in  a  water-bath  at  230°  to 
248°  F.,  and  the  tarred  platinum  dish,  after 
having  been  cooled  in  the  desiccator,  is 
weighed.  If  the  utmost  accuracy  is  de- 
manded, the  copper  is  heated  in  a  current 
of  sulphuretted  hydrogen. 


180 


XX. 

Electrolytic  Determination  of  Copper. 

CLASSEN'S  method  for  the  electrolytic  de- 
termination of  metals  is  based  upon  the  fact 
that  the  separation  of  the  metal  is  best 
effected  when  the  oxide  is  fixed  to  an  acid 
readily  decomposed  by  the  current,  so  that 
a  secondary  reaction  cannot  take  place. 
Such  an  acid  is  oxalic  acid,  which  splits 
into  carbonic  acid  and  hydrogen.  Most 
heavy  rnetals  give  insoluble  precipitates 
with  oxalic  acid ;  their  double  alkaline 
salts  are,  however,  readily  soluble,  and  by 
adding  ammonium  oxalate  in  excess  the  re- 
action progresses  with  ease  and  without  the 
formation  of  a  precipitate.  The  carbonic 
acid  separated  on  the  positive  pole  by  the 
decomposition  of  the  ammonium  oxalate 
combines  with  the  ammonium,  forming  am- 


ELECTROLYTIC  DETERMINATION  OF  COPPER.    181 

monium  carbonate.  In  general  the  process 
is  conducted  by  converting  the  neutral 
chlorides  arid  sulphates  of  the  metals  into 
double  oxalates  by  the  addition  of  a  large 
excess  of  ammonium  oxalate,  heating  the 
solution  and  exposing  it  to  the  action  of  a 
galvanic  current,  whereby  the  metals  de- 
posit quickly  and  in  a  compact  form  on  the 
negative  electrode. 

The  determination  of  copper,  as  is  well 
known,  can  be  very  easily  effected  directly 
from  the  acid  solution.  According  to  Clas- 
sen's method  the  solution  (concentrated,  if 
necessary,  by  evaporation)  is  heated  to  boil- 
ing, and,  after  adding  3  to  4  grammes  of 
solid  ammonium  oxalate,  subjected  to  the 
action  of  the  electric  current  as  soon  as 
everything  is  dissolved.  The  copper  sep- 
arates quickly  and  easily,  provided  the 
current  is  not  too  weak.  With  a  strength 
of  current  corresponding •  to  300  cubic  cen- 
timeters of  oxy hydrogen  gas  per  hour,  0.15 
gramme  of  metallic  copper  can  be  separated 


182  THE  ASSAYER'S  GUIDE. 

in  25  minutes.  As  the  negative  electrode, 
Classen  uses  a  'platinum  dish,  and  for  the 
positive  electrode  a  disk,  4  to  5  centimeters 
in  diameter,  of  moderately 
thick  platinum  sheet,  Fig.  G, 
which  is  secured  by  a  screw 
to  a  medium  thick  platinum 
wire. 

To  prevent  loss  the  plati- 
num dish  is  covered  with  a 
watch  crystal  perforated  in 
the  centre.  The  entire  ar- 
rangement of  the  apparatus 
is  shown  in  Fig.  H.  The 
glass  cylinder  shown  in  front 
is  the  resistance-arrangement 
recommended  by  Classen  for 

"  ---  N. 

^  the  reduction  of  more  consid- 


G.  erable  strengths  of  current. 
It  consists  of  a  rod  b  with  a  zinc  pole, 
which  can  be  moved  to  and  from  the  zinc 
pole  a  until  the  current  reaches  the  desired 
strength.  The  zinc  poles  must  be  amai- 


ELECTROLYTIC  DETERMINATION  OF  COPPER.    183 

gamated    with    mercury   and    hydrochloric 
acid,  and  the  contacts  at  «,  b  kept  clean. 

According  to  Herpin's  method  of  assay- 
ing copper  by  electrolysis,  1  gramme  or 
more  of  the  assay-sample  is  dissolved  in 
nitric  acid.  The  solution  is  evaporated 


FIG.  H. 

nearly  to  dryness,  the  residue  dissolved  in 
a  small  quantity  of  dilute  sulphuric  acid 
and  the  solution  diluted  to  60  or  70  cubic 
centimeters.  The  solution  is  poured  into 
the  platinum  dish  A,  Fig  I,  and  the  conduct- 
ing stand  B  of  the  dish  is  connected  with 


184 


THE    ASS  AVER'S   GUIDE. 


the  negative  electrode,  the  platinum  spiral 
C  with  the  positive  elec- 
trode, and  the  liquid 
electrolyzed  after  the 
funnel  D  has  been  placed 
in  position.  When  the 
copper  has  been  precipi- 
tated, the  fluid  is  poured 
]  from  the  dish.  The  lat- 
FIG.  I.  ter  is  rinsed  out  first  with 

water  and  next  with  alcohol,  then  dried  and 

weighed,  the  copper  being  determined  from 

the  increase  in  weight. 


185 


XXI. 

Assay  of  Lead   Ores. 

THE  method  of  assaying  lead  ores  de- 
pends on  the  nature  of  the  ore  and  chiefly 
on  whether  the  lead  occurs  in  a  sulphur- 
etted or  oxidized  state. 

A.  With  sulphuretted  lead  combinations 
three  cases  are  to  be  distinguished  :  a.  The 
galena  contains,  besides  a  few  earthy  con- 
stituents, none  or  very  few  foreign  sulphides 
(copper  pyrites,  iron  pyrites,  zinc  blende, 
etc.).  b.  Many  of  such  sulphides  are  pres- 
ent, c.  Earthy  'constituents  are  present  in 
predominant  quantity. 

As  a  rule,  these  conditions  can  be  better 
recognized,  when  the  assay-sample  is  in 
pieces  than  when  in  the  form  of  a  powder.. 
In  the  latter  case  elutriation  may,  with 
the  assistance  of  a  magnifying  glass,  give 


186  THE   ASSAY  ER*8   GUIDE. 

important  disclosures  regarding  the  metallic 
admixtures. 

1.  Methods  of  assaying  sulphuretted  lead 
ores  which  contain  few  or  no  foreign  sul- 
phides. 

These  methods  are  based  upon  the  desul- 
phuration  of  the  galena  by  iron  and  alka- 
lies, or,  as  is  more  generally  done,  simulta- 
neously- by  iron  and  alkalies,  and  promoting 
the  reduction  of  the  alkalies  by  the  addition 
of  carbon,  or  entirely  omitting  the  latter. 
Too  much  carbon  causes  refractoriness. 
The  carboniferous  substances  also  main- 
tain an  oxidizing  atmosphere  in  the  cru- 
cible and  prevent  the  oxidation  of  the 
sulphides  of  iron  to  oxidized  iron,  which 
strongly  attacks  the  sides  of  the  crucible 
and  in  pouring  out  the  assay  contributes  to 
the  retention  of  particles  of  lead.  Any 
white  lead  or  sulphate  of  lead  occurring 
together  with  the  galena  are  reduced  by  the 
carboniferous  substances.  By  the  alkalies 
alone,  or  the  simultaneous  use  of  suitable 


ASSAY   OF   LEAD   ORES.  187 

fluxes,  such  as  glass  and  borax,  the  earths 
occurring  in  the  ores  are  scorified.  If  for- 
eign sulphides,  such  as  copper  pyrites,  sul- 
phide of  antimony,  zinc  blende,  etc.,  are 
associated  with  the  galena,  they  are  also 
partially  decomposed  by  the  alkalies  and 
the  iron,  and  their  radicals  pass  into  the 
lead.  They  also  give  rise  to  the  formation 
of  sulphur-salts,  which  retain  sulphide  of 
lead  in  the  slag.  Of  the  alkaline  combina- 
tions potash  and  dehydrated  soda  are  chiefly 
used.  The  carbon  is  employed  either  in 
the  form  of  coal  dust  mixed  with  the  potash, 
or  still  better,  in  a  finely  divided  state  in 
black  flux,  or  in  a  mixture  of  potash  and 
flour. 

The  black  flux  is  prepared  by  pouring  a 
mixture  of  2£  parts  crude  tartar  and  1  part 
saltpetre  (crude  flux)  in  a  heated  clay  cru- 
cible and  laying  a  glowing  coal  upon  the 
surface;  or  by  gradually  introducing  the 
mixture  into  a  glowing  crucible.  The  mass 
thereby  decrepitates,  whereby  the  oxygen 


188  THE  ASSAYER'S  GUIDE. 

of  the  nitric  acid  first  oxidizes  the  hydrogen 
of  the  tartaric  acid,  this  being  the  most 
readily  oxidizable  constituent,  and  then  also 
a  portion  of  the  carbon,  while,  with  a  cor- 
rect quantity  of  saltpetre,  another  portion 
of  the  carbon  separates  in  a  finely  divided 
state.  By  taking  too  much  saltpetre  all  the 
carbon  is  oxidized,  and  instead  of  a  mixture 
of  potassium  carbonate  and  carbon  (black 
flux)  only  potassium  carbonate  (white  flux) 
is  obtained,  arid  with  little  carbon,  gray  flux. 
Black  flux  has  the  disagreeable  property 
of  readily  absorbing  moisture,  arid,  hence, 
must  frequently  be  prepared  fresh.  For 
this  reason  it  is  more  convenient  to  use  a 
mixture  of  100  parts  potash  and  10  to  15 
parts  rye  or  wheat  flour.  On  heating  the 
mixture  the  latter  carbonizes  and  finely 
divided  carbon  is  separated  with  the  evolu- 
tion of  reducing  varieties  of  gas. 

The  fluxes  are  frequently  protected  by  a 
cover  of  common  salt.  It  serves  to  keep 
off  the  air  from  the  melting  assay  and  after 


ASSAY   OF    LEAD   ORES.  189 

it  has  become  thinly-fluid  as  a  wash,  bring- 
ing down  from  the  sides  of  the  crucible  ad- 
hering metallic  grains  or  fluxes. 

All  assays,  containing  in  their  charge 
carbon,  puff  up  in  consequence  of  the  for- 
mation of  carbonic  oxide,  and  hence  capa- 
cious crucibles,  which  should  at  the  utmost 
be  filled  I  full  with  the  assay-sample,  have 
to  be  used.  The  crucibles  are  heated  either 
in  an  air-furnace  or  a  muffle-furnace ;  a 
blast-furnace  being  seldom  used. 

For  assaying  lead  ores  of  the  kind  men- 
tioned under  A  1,  various  methods  are  in 
use  in  different  places. 

a.  Assays  without  /luxes  .  in  iron  vessels. 
These  are  suitable  only  for  nearly  pure 
galena. 

a.  Assay  in  iron  dishes.  Galenas  nearly 
free  from  foreign  admixtures  are  assayed  in 
England  as  follows :  About  300  grammes 
of  the  ore  are  placed  in  a  red-hot  w rough t- 
irondish.  The  latter  is  about  5  to  6  milli- 
meters thick,  0.127  meter  in  diameter  and 


190 

0.025  meter  deep  in  the  centre.  After  in- 
troducing the  assay-sample  the  dish  is  pro- 
vided with  a  semicircular  lid  of  somewhat 
larger  diameter,  and  the  whole  heated  in 
a  blast-furnace  for  about  2  minutes.  The 
dish  is  then  taken  from  the  furnace  and 
placed  upon  a  ring.  When  the  matte  is 
congealed,  empty  the  still  liquid  lead  intc 
a  conical  bronze  mould,  melt  the  matte  in 
the  dish  once  more,  using  a  stronger  fire,  and 
then  pour  all  upon  a  metal  plate,  whereby 
a  small  lead  regulus  still  results.  In  5  to 
6  minutes  two  such  meltings  are  finished. 
Seventy-five  to  eighty  per  cent,  of  lead  are 
in  a  short  time  brought  out,  and  these 
assays  are  especially  used  for  controlling 
the  reverberatory  furnace  process,  in  which 
nearly  the  same  volatilization  of  metal 
takes  place. 

P.  Assay  in  iron  crucibles.  In  South 
Wales  about  80  grammes  of  galena  are 
melted  in  an  iron  crucible,  about  72  milli- 
meters high  and  69  millimeters  in  diameter 


ASSAY   OF    LEAD   ORES.  191 

on  the  top,  in  an  air-furnace  for  about  10 
to  15  minutes.  The  yield  is  81  to  82  per 
cent. 

b.  Assays  with  fluxes.  The  fluxes,  which 
have  to  be  added  to  more  impure  ores, 
serve  either  for  decomposing  the  galena  or 
for  scorifying  oxide  and  earthy  admixtures, 
or  for  both  purposes. 

Of  silver  nearly  everything  passes  into 
the  lead  ;  with  a  content  of  sulphide  of 
iron  in  the  slag  more  silver  is  retained 
than  without  such  a  content.  Copper  is 
divided  between  lead  and  slag.  Of  zinc 
only  a  small  portion  passes  into  the  lead, 
that  which  does  not  volatilize  passing 
chiefly  into  the  slag.  Iron  is  only  found 
in  traces  in  the  lead,  but  antimony  in 
abundance,  while  arsenic  partially  vola- 
tilizes as  arsenic  and  orpiment,  and  par- 
tially yields  speiss  with  iron.  Silica  pro- 
motes the  scorification  of  lead  more  than 
calcareous  spar  and  heavy  spar.  If  lime 
and  ferric  oxide  be  at  the  same  time  present 


i92 

scorification  is  counteracted.  The  lead  in 
an  impure  lead  regulus  obtained  by  the  dry 
assay  can  only  be  determined  by  the  wet 
method.  With  a  content  of  copper,  dissolve 
the  regulus  in  moderately  strong  nitric  acid, 
evaporate  the  solution  with  sulphuric  acid 
until  the  nitric  acid  is  expelled,  dilute  with 
water,  bring  the  sulphate  of  lead  upon  a 
dry,  weighed  filter,  or  reduce  it  with  cya- 
nide of  potash  and  soda  in  a  porcelain 
crucible.  Brittle  lead  containing  antimony 
is  oxidized  with  nitric  acid,  the  dilute  solu- 
tion digested  with  ammonia,  ammonium 
sulphide  and  some  sulphur,  and  the  undis- 
solved  sulphide  of  lead  converted  into 
sulphate. 

According  to  the  quality  and  quantity  of 
the  foreign  admixtures,  the  following  methods 
of  assaying  may  be  used. 

a.  Assay  in  an  iron  crucible  with  black 
flux.  With  ores  as  free  as  possible  from 
copper  and  poor  in  earths,  this  assay  in  a 
short  time  gives  the  greatest  yield  (84 i  to 


ASSAY  OF   LEAD  ORES.  193 

85 i  per  cent.),  because  it  is  for  a  shorter 
time  (10  to  15  minutes)  in  the  fire  and 
can  be  executed  with  larger  quantities  of 
ore,  whereby  the  loss  is  distributed  over 
larger  quantities.  The  absence  of  a  larger 
content  of  earths  favors  the  complete  pour- 
ing out  of  the  contents  of  the  crucible 
into  moulds,  while  with  larger  quantities 
of  slag,  the  latter  adheres  to  the  sides  of 
the  crucible  and  mechanically  retains  lead. 
This  method,  which  is  much  used  in  Eng- 
land, Germany,  France  and  Belgium,  is 
executed  as  follows :  Heat  a  wrought-iron 
crucible  in  an  air-furnace  to  a  red  heat,  and 
then  charge  it  with  25  to  50  grammes  of 
lead  ore  and  12  to  15  grammes  of  flux 
(potash,  soda,  or  a  mixture  of  2  parts  salt- 
petre, 3  argol,  and  1  borax).  Then  add  a 
cover  of  common  salt  or  powdered  glass, 
place  an  iron  lid  upon  the  crucible  and 
gradually  heat  during  5  minutes  to  a  red 
heat,  and  maintain  this  temperature  for  5 
to  8  minutes  longer.  When  all  is  melted, 

13 


194  THE  ASSAYER'S  GUIDE. 

and  any  globules  of  lead  appearing  on  the 
surface  or  unmelted  masses  have  been  sub- 
merged with  a  spatula,  take  the  crucible 
from  the  furnace,  and,  after  allowing  it  to 
cool  somewhat,  pour  the  contents  into  a 
warmed  ingot-mould  painted  inside  with 
black  lead.  The  slag  may  be  again  melted 
with  some  flux  (soda  or  potash  and  argol) 
for  10  to  12  minutes. 

The  difference  between  the  quantity  of 
lead  obtained  by  the  assay  and  that  actually 
present  in  the  ore  is  nearly  the  same  with 
ores  from  the  highest  to  50  per  cent,  con- 
tent of  lead,  but  increases  with  poorer  ores. 
Of  86.81  per  cent,  actual  content  of  galena 
84  i  to  85i  per  cent,  is  obtained  by  this 
assay.  The  proportions  of  the  charge  in 
various  works  are  as  follows :  In  England  : 
for  rich  ores,  500  grains  (32.  4  grammes) 
ore,  500  grains  soda  and  50  grains  argol ; 
for  poorer  ores,  850  grains  soda,  150  grains 
borax  and  50  grains  argol ;  time  for  melting, 
8  to  10  minutes;  entire  time,  10  to  15 


ASSAY  OF  LEAD  ORES.  195 

minutes.  At  Freiberg :  50  grammes  ore, 
2  tablespoon fuls  flux  (3  parts  argol,  2  salt- 
petre, 1  borax) ;  time  for  melting,  at  a  red 
heat,  12  to  15  minutes;  time  for  heating 
the  slag  with  potash,  10  to  12  minutes. 

0.  Assay  in  a  clay  crucible  with  black  flux 
and  iron  ;  available  for  ores  poor  in  foreign 
sulphides  but  richer  in  earths.  At  Freiberg 
this  method  of  assaying  is  executed  as  fol- 
lows: Charge  a  crucible,  first  with  3.75 
grammes  of  powdered  ore,  then,  according 
to  its  richness,  place  upon  the  ore  0.37  to 
1.12  grammes  of  iron  wire  (a  piece  6.5  to 
9.8  millimeters  long  and  4  to  5.5  millimeters 
thick),  spread  out  upon  it  11.25  grammes 
of  black  flux,  or  8.37  grammes  of  a  mix- 
ture of  potash  and  flour,  cover  the  latter 
with  1.12  to  1.5  grammes  of  borax,  and 
finally  add  a  cover  of  common  salt  a  few 
millimeters  thick.  If  foreign  sulphides, 
combinations  of  antimony  or  arsenic  are 
present,  the  ore  previously  to  charging  it 
may  be  somewhat  roasted. 


196  THE   ASSAYEK'8   GUIDE. 

With  galena  ores  the  charge  at  Pribram 
is  as  follows:  5  grammes  ore,  11.5  to  12 
grammes  black  flux  (2  parts  argol,  1  salt- 
petre), 1  to  1.2  grammes  borax  and  2  to  2.5 
grammes  iron  wire.  With  ores  containing 
blende  :  5  grammes  ore,  20  grammes  black 
flux,  1  to  1.2  grammes  borax  and  2  t.o  2.5 
grammes  iron  wire.  Some  argol  is  always 
placed  upon  the  bottom  of  the  crucible  and 
under  the  common  salt  serving  as  cover,  2 
to  3  per  cent,  saltpetre,  in  order  to  make 
the  common  salt  more  fluid  and  retain  the 
lead,  which  is  volatilized,  by  oxidation. 

The  assay  is  melted  in  an  air-furnace. 
When  taken  from  the  furnace,  the  crucible 
is  allowed  to  cool,  the  lead  regulus  is  then 
freed  from  slag,  flattened  to  remove  any 
adhering  sulphide  of  iron,  and  weighed. 
The  assay  may  be  considered  a  success 
when  assay  and  counter-assay  agree,  when 
the  lead  is  at  the  bottom  in  one  button  and 
the  slag  uniform  in  character.  By  a  few 


ASSAY    OF    LEAD   ORES.  197 

blows  of   the    hammer,   the    iron   wire   is 
separated  from  the  adhering  lead. . 

The  galena  is  at  first  desulphurized  by 
the  alkali,  alkaline  sulphate  and  potassium 
sulphide  being  formed  besides  lead.  The 
potassium  sulphide  combines  with  a  portion 
of  still  undecomposed  galena  to  a  sulphur- 
salt  which  passing  into  the  slag  at  an  in- 
creased temperature — hence,  towards  the 
end  of  melting — is  freed  by  the  iron  from  its 
content  of  lead.  The  carbon  prevents  an 
oxidation  of  the  lead  and  reduces  the  alkali. 
It,  therefore,  also  contributes  towards  the 
desulphurization,  the  potassium  formed 
being  closely  allied  to  sulphur.  Another 
portion  of  the  alkali  in  conjunction  with 
the  borax  and  glass  causes  the  scorification 
of  the  earths  and  metallic  oxides  contained 
in  the  assay-sample.  Besides  silicates  the 
slag  also  contains  sulphur-salts,  especially 
a  double  sulphide  of  potash  and  iron.  The 
cover  of  the  readily-fluid  common  salt  pre- 
vents the  adherence  of  lead  globules  on 


198  THE  ASSAYER'S  GUIDE. 

the  edge  of  the  crucible  and  shuts  out  the 
air. 

This  method  of  assaying  is  very  simple, 
readily  executed  and  permits  of  the  best 
yield  of  lead  for  ores  of  the  above-mentioned 
kinds.  From  galena  with  85.5  per  cent,  of 
lead  up  to  84.85  per  cent,  is  obtained ; 
with  more  impure  ores,  the  loss  of  lead 
may,  however,  increase  to  10  per  cent. 

v.  Upper  Harz  potash  assay  in  clay  cru- 
cibles. Melt  5  grammes  of  galena  with 
three  times  the  quantity  of  potash  under 
a  cover  of  common  salt  in  a  crucible  under 
the  muffle  strongly  heated  for  15  to  30 
minutes  or  longer  until  fusion  is  complete. 
The  following  reaction  thereby  takes  place  : 
4  K2  C  03  +  Pb  S  =  4-  Pb  +  3  (K2  S  + 
Pb  S)  +  K2  S  04  +  4  C  02.  In  order  to 
separate  from  th  sulphur-salt  (K2  S  + 
Pb  S)  the  lead  retained  by  it  open  the 
muffle  5  to  10  minutes  and  moderate  the 
fire,  whereby  the  K2  S  is  converted  into 
K2  S  04,  and  the  liberated  Pb  S  partially 


ASSAY  OF  LEAD  ORES.  199 

into  Pb  S  04.  If  now  the  muffle  is  again 
closed  and  after  10  minutes  a  strong  heat 
is  given,  the  sulphate  of  lead  acts  upon  the 
decomposed  sulphide  of  lead,  metallic  lead 
being  formed,  if  the  proper  time  has  been 
allowed  for  the  above-mentioned  cooling 
(Pb  S  +  Pb  S  04  =  2  Pb  +  2  S'02).  If 
cooling  is  continued  for  too  long  a  time,  oxide 
of  lead  remains  in  the  slag,  and  if  for  too 
short  a  time,  sulphide  of  lead.  The  dura- 
tion of  cooling  at  which  the  most  lead  is 
obtained  must  be  ascertained  for  each  ore. 

2.  Methods  of  assaying  sulphuretted  lead 
ores  which  contain  many  foreign  sulphides. 

The  above-mentioned  assays  are  not  suit- 
able for  such  lead  combinations,  because 
the  foreign  sulphides  are  decomposed  by 
the  alkalies  and  the  iron,  their  radical 
passing  into  the  lead  button,  and  an  abun- 
dant formation  of  sulphur-salts  takes. place, 
which  always  retain  much  lead  in  the 
slag. 

For  such  substances  the  calcination-assay 


200  THE   ASSAYER"S   GUIDE. 

and  a  partially  wet  assay  with  sulphuric 
acid  are  suitable. 

a.  Calcination-assay.  This  assay  is  used 
for  Rarnmelsberg  ores  whose  small  content 
of  lead  is  diminished  5  to  8  per  cent,  by 
the  presence  of  considerable  quantities  of 
iron  pyrites,  copper  pyrites,  zinc  blende, 
antimony  and  arsenic  combinations,  as  well 
as  earthy  substances.  Take  from  a  pile  of 
ore,  which  has  previously  been  roasted,  three 
times,  5  to  10  grammes.  Pulverize  this 
assay-sample  and  thoroughly  roast  it  for  6 
or  more  hours  in  a  more  or  less  shallow 
crucible  about  65  millimeters  in  diameter, 
13  to  16  millimeters  deep  and  painted  in- 
side with  reddle  or  chalk  washes.  By 
thorough  roasting  is  understood  heating  the 
ore  at  a  gradually  increasing  temperature 
and  with  the  access  of  air,  so  that  no  fusion 
takes  place,  but  the  air  can  exert  an  oxi- 
dizing effect  upon  the  sulphides,  whereby 
the  latter,  with  the  development  of  sul- 
phurous acid,  are  converted  into  oxides. 


ASSAY  OF  LEAD  ORES.  201 

In  order  to  effect  this  as  completely  as  pos- 
sible frequently  turn  the  crucible  around 
so  that  the  air  can  act  uniformly.  After 
half  an  hour  take  the  crucible  from  the 
furnace,  triturate  the  assay-sample,  if  it 
should  be  slagged  together,  in  a  cast-iron 
mortar,  roast  again  for  about  half  an  hour, 
triturate  again,  mix  coal  dust  or  another 
carbonaceous  substance,  for  instance,  suet, 
with  it  and  reheat.  In  roasting,  metallic 
sulphates  are  also  formed  from  the  sul- 
phides, which  by  the  addition  of  carbon  are 
to  be  decomposed  so  that,  with  the  develop- 
ment of  sulphurous  acid,  they  again  form 
sulphides  and  then  with  the  repeated  access 
of  air  are  reconverted  into  oxides  and  sul- 
phates. The  sulphur  can  only  be  removed 
by  repeated  triturating  and  heating  of  the 
ore  with  carbon  at  a  gradually  increased 
temperature.  The  last  portions  of  it,  which 
remain  as  sulphates  in  the  roasted  powder, 
are  removed  by  heating  the  latter  with 
ammonium  carbonate,  volatile  ammonium 


202 

sulphate  being  formed.  The  sulphate  of 
lead  formed  in  roasting  the  sulphide  of  lead 
can  in  this  manner  be  but  incompletely  de- 
composed and  hence  remains  as  such  in 
the  roasted  sample.  'A  thoroughly  roasted 
sample  has  an  earthy  appearance  and  shows 
no  odor  of  sulphurous  acid.  It  is  finally 
taken  from  the  furnace,  allowed  to  cool  and, 
after  being  charged  with  suitable  fluxes, 
melted  for  metallic  lead. 

The  roasted  sample  chiefly  consists  of  the 
oxides  of  the  lead,  iron,  copper,  zinc,  etc., 
and  if  it  is  melted  at  not  too  high  a  tem- 
perature with  reducing  agents  (black  flux, 
potash  and  flour)  and  solving  fluxing  (borax, 
glass),  the  lead  oxide  is  reduced  to  metallic 
lead  while  the  metallic  oxides,  reducible 
with  more  difficulty,  are  scorified.  How- 
ever, with  too  high  a  temperature  in  melt- 
ing, the  latter  are  also  partially  reduced 
and  the  resulting  lead  is  impure.  Too 
much  or  too  little  of  solving  fluxes  causes 
glorification  of  lead  oxide,  or  reduction  of 


ASSAY  OF   LEAD   ORES.  203 

the  foreign  oxides  if  scorifying  agents  are 
wanting.  The  sulphate  of  lead  present  is 
partially  decomposed  by  the  acids  of  the 
borax  and  glass  and  partially  reduced  to 
sulphide  of  lead,  from  which  by  the  alkali 
a  portion  of  the  lead  is  separated,  while 
another  portion  remains  as  a  double  sul- 
phide of  potash  and  lead  in  the  slag.  For 
the  decomposition  of  the  latter  combina- 
tion a  small  addition  of  iron  is  recom- 
mended. 

Melting  is  executed  by  mixing  the  roasted 
assay-sample  with  three  to  four  times  the 
quantity  of  black  flux  and  an  equal  weight 
of  borax  and  glass,  bringing  the  mixture 
into  a  crucible,  covering  it  with  common 
salt  and.  after  placing  the  lid  upon  the  cru- 
cible, heating  it  in  an  air-furnace  for  about 
i  hour.  If  the  assay  has  been  successful 
the  lead  lies  on  the  bottom  under  the  well- 
fused  slag  in  one  button  without  being  en- 
veloped by  brittle  sulphides. 

b.  Assay  with   sulphuric  acid.      Decom- 


204  THE   ASSAYER'S   GUIDE. 

pose  5  or  10  grammes  of  finely  pulverized 
ore  in  a  digesting-glass  with  nitric  acid, 
evaporate,  with  the  addition  of  sulphuric 
acid,  the  contents  of  the  glass  to  dryness, 
moisten  the  dry  mass  with  a  few  drops  of 
sulphuric  acid,  soften  it  with  water,  bring 
it  upon  a  filter,  and  thoroughly  wash  the 
residue  upon  the  latter.  Besides  insoluble 
earths,  the  residue  chiefly  consists  of  sul- 
phate of  lead  which  is  with  difficulty  sol- 
uble in  water,  while  the  sulphates  of  the 
metals  associated  with  galena  being  readily 
soluble  in  water  are  removed  after  washing 
the  residue.  The  filter  is  dried,  ignited 
with  its  contents  and  the  ignited  mass 
melted  with  black  flux  and  iron,  whereby 
the  sulphide  of  lead  reduced  from  sulphate 
of  lead  is  decomposed  by  the  iron,  the  re- 
sult being  a  button  of  lead. 

This  assay  gives  a  more  correct  content 
of  lead  than  the  preceding,  and  is  also 
suitable  for  lead  alloys.  On  account  of 
the  availability  of  lower  temperatures,  the 


ASSAY   OF   LEAD   ORES.  205 

assay  becomes  still  more  accurate  by  mix- 
ing the  residue  obtained  by  treating  the 
mass  in  a  capacious  porcelain  crucible  and 
heating  until  the  free  sulphur  is  volatilized, 
with  about  five  times  the  quantity  of  potas- 
sium cyanide  (with  or  without  soda)  and 
melting  in  the  covered  crucible  over  a  small 
lamp.  The  cold  melt  is  extracted"  with 
water,  and  the  lead  remaining  behind  in 
one  or  more  buttons  decanted  with  water 
containing  alcohol,  dried  and  weighed.  If 
a  black  powder,  which,  however,  contains 
no  sulphide  of  lead,  has  been  formed,  re- 
move it  by  washing.  In  both  cases  a 
content  of  antimony  passes  into  the  lead 
and  has  to  be  removed  by  the  wet  process. 
3.  Methods  of  assaying  for  sulphuretted 
lead  ores ,  which  contain  many  earthy  con- 
stituents. In  such  combinations  the  con- 
tent of  lead  can  only  be  very  inaccurately 
determined  by  the  dry  method  by  melting 
a  larger  quantity  of  assay  substance  (100 
to  500  grammes)  with  the  most  powerful 


206  THE  ASSAYER'S  GUIDE. 

fluxes  (caustic  alkalies),  and  the  addition 
of  reducing  agents,  and  stirring  a  piece  of 
sheet  iron  bent  in  the  form  of  a  horseshoe 
around  in  the  fluid  mass  until  all  the  lead 
is  separated.  If  the  content  of  lead  is  not 
too  small,  not  below  i  per  cent.,  a  useful 
result  is  also  obtained  by  mixing  10  to  20 
grammes  of  the  substance  to  be  assayed  in 
the  ordinary  manner  with  potash  or  black 
flux,  spreading  out  on  top  of  the  mass  arv 
accurately  weighed  quantity  of  finely  di- 
vided silver  (30  to  50  per  cent.),  covering 
the  latter  with  common  salt  and  melting  in 
the  usual  manner.  The  increase  in  the 
weight  of  the  silver  represents  the  content 
of  lead. 

B.  Oxidized  lead  ores  and  smelting  prod- 
ucts may  be  assayed  as  to  their  content  of 
lead  by  two  methods,  viz. : 

1.  By  melting  with  reducing  agents  when 
the  assay-sample  contains  free  lead  oxide 
(litharge,  lead  scurn,  or  skim)  or  lead  oxide 
fixed  on  carbonic  acid  or  an  organic  acid 


ASSAY   OF   LEAD   ORES.  207 

(as  white  lead  ore,  lead  acetate),  or  lead 
oxide  combined  with  fixed  mineral  acids 
which  cannot  be  reduced,  but  combine 
directly  with  the  alkalies  (silicate,  phos- 
phate, tungstate  and  molybdate  of  lead ;  in 
chromate  of  lead,  the  chromic  acid  is  re- 
duced to  chromic  oxide,  which  passes  into 
the  slag). 

Combinations  of  the  above-mentioned 
variety  are  mixed  with  three  or  four  times 
their  weight  of  black  flux  or  potash  and 
flour,  and  melted  under  a  cover  of  salt  in  a 
crucible.  The  slag  must  become  thinly- 
fluid,  and  as  this  chiefly  depends  on  the 
nature  of  the  by-constituents,  the  height  of 
the  temperature  in  melting,  and  the  dura- 
tion of  the  latter,  must  accordingly  be 
modified.  To  highly  silicated  lead  slags  it 
is  best  to  add  a  flux  of  from  20  to  50  per 
cent,  borax,  and  to  very  poor  slags,  con- 
taining i  to  $  per  cent,  of  lead,  a  flux  of  15 
to  20  per  cent,  silver  for  the  collection  of 
the  lead.  Slags  containing  sulphur  are 


208  THE  ASSAYER'S  GUIDE. 

somewhat  roasted,  or  receive  a  flux  of  from 
5  to  10  per  cent.  iron.  According  to  the 
refractoriness  of  the  slags,  melting  may  last 
from  1  \  to  2  hours,  in  order  to  give  the  lead 
an  opportunity  to  thoroughly  separate  from 
the  very  thinly-liquid  slag.  At  Mecher- 
nich  the  lead  slags  are  melted  with  §  soda 
and  \  borax  in  an  iron  crucible  at  a  bright 
red  heat ;  result,  0.4  to  0.6  per  cent,  of  lead. 

Percy  recommends  the  following  charges  : 
For  white  lead  ore :  500  grains  ore,  500 
soda,  100  argol  and  30  borax.  Time  of 
melting,  20  minutes.  For  minetite  (green 
lead  ore)  :  besides  iron  flux,  300  grains  ore, 
400  soda,  20  coal  dust  and  30  borax ;  or 
350  grains  soda,  100  argol  and  30  borax. 
Duration  of  the  process  from  the  time  of  in- 
troducing the  charge  to  pouring  out,  25  to 
30  minutes. 

2.  By  melting  with  reducing  agents  and 
iron,  when  the  lead  oxide  is  fixed  on  sul- 
phuric acid,  arsenious  or  arsenic  acids,  as, 
for  instance,  in  sulphate  of  lead,  in  calcined 


ASSAY   OF  LEAD  ORES.  209 

galena  and  matt  of  lead,  lead  smoke,  slag- 
lead,  dross,  etc.  Charge  with  three  to  four 
times  the  quantity  of  black  flux  and  10  to 
30  per  cent.  iron.  For  slags,  an  addition 
of  5  to  10  per  cent,  iron  suffices. 

14 


210 


XXII. 

Assay  of  Lead  Ores  by  Heat 

THERE  is  no  way  of  assaying  lead  ores  by 
heat  which  gives  the  full  amount  of  the 
metal,  as  it  is  so  easily  oxidized  by  a  high 
temperature.  Generally,  the  loss  varies 
from  one-sixth  to  one-twelfth,  or  yet  more 
commonly  is  about  a  tenth;  and  for  this 
reason,  the  result  of  the  assay  should  after- 
ward be  increased  by  A,  on  giving  the  per- 
centage of  lead. 

The  assay  is  performed  in  the  crucible, 
fig.  4,  or  in  the  Hessian  one.  The  part  of 
ore  used  ought  to  be  about  two  hundred 
grains,  as  lead  ores  (galena,  a  sulphuret  of 
lead  is  the  most  common)  are  very  heavy, 
and  therefore  are  comparatively  small  in 
bulk.  Three  parts,  or  here  six  hundred 
grains,  of  black  flux  are  mixed  up  with  the 


ASSAY   OF    LEAD    ORES    BY   HEAT.  211 

powdered  ore. 

A  little  piece  of  very  thick  wire,  or  of  a 
round  iron  bar,  weighing  from  thirty  to 
forty  per-cent.  of  the  weight  of  the  lead 
ore,  is  placed  on  the  top,  in  the  crucible. 

We  then  expose  the  whole  to  a  strong, 
steady  red-heat,  for  about  an  hour,  in  the 
bellows  furnace,  fig.  6,  Plate  I.  This  is  ef- 
fected by  first  placing  the  crucible  on  the 
bri^.k,  and  then  making  a  layer  of  cold 
burnt  coals,  as  high  as  the  brick.  On  this 
come  the  live  coals,  and  on  them  the  un- 
burnt  ones  up  to  the  top  of  the  furnace. 
When  burnt  down,  we  take  out  the  cruci- 
bles, and  thus  obtain  a  button  of  pure  lead 
and  some  slag,  besides  a  remaining  portion 
of  the  iron. 

The  latter  should  be  added  in  excess,  to 
insure  the  entire  absorption  of  the  sulphur. 
Galena  contains,  in  hundred  parts,  13.45 
parts  of  sulphur  to  86.55  of  lead,  which 
would  require  22.67  parts  of  metallic  iron 
to  form  sulphuret  of  iron,  consisting  of  37.23 


212 

parts  of  sulphur  to  62.77  of  iron.  If,  there- 
fore, two  hundred  grains  of  the  ore  are 
used,  the  iron  should  weigh  from  60  to  100 
grains.  Filings  ought  never  to  be  used,  as 
they  are  always  covered,  to  a  smaller  or 
greater  amount,  with  oxide.  Besides,  it  is 
very  difficult  to  get  them  as  free  from  im- 
purities as  wire.  Weighed  pieces  of  the 
latter  should  be  kept  in  some  vial  or  box 
for  this  purpose. 


213 


XXIII. 

Assay  of  Lead  Ores  ty  a  Wet  Process. 

THIS  method  will  be  found  much  the 
more  accurate  of  the  two,  although  it  may 
not  often  happen  that  a  practical  assayer 
has  sufficient  time  for  this  proceeding.  (See 
Woehler's  Anal.  Chem.) 

The  ore  (galena)  should  be  powdered 
much  finer  even  than  in  the  assay  by  heat, 
after  which  it  is  moistened  with  fuming 
nitric  acid,  and  digested  in  the  sand-bath, 
by  which  process  it  is  entirely  changed 
from  the  sulphuret  to  the  sulphate  of  lead. 

If  the  mass  be  diluted  with  water  and 
filtered,  the  merest  traces  only  of  lead  can 
be  found  in  the  solution, — quantities  toe 
small  to  deserve  any  farther  attention.  If 
the  ore  contain  copper,  iron,  or  silver,  they 
will  be  contained  in  this  filtered  solution ; 


214  THE   ASSAYERi'S   GUIDE. 

the  first  are  then  discovered  by  ammonia, 
the  latter  by  muriatic  acid. 

Should  fuming  nitric  acid  not  be  at 
hand,  and  if  therefore  a  weaker  kind  is 
used,  a  mixture  of  sulphate  of  lead  and  sul- 
phur is  produced,  together  with  a  solution 
of  nitrate  of  lead.  From  this  latter  the 
metal  should  be  precipitated  with  sulphuric 
acid.  By  heating  the  dried  residue, — after 
filtering  and  washing,  by  pouring  water 
over  it  while  yet  on  the  filter, — sulphur  is 
evaporated  and  sulphate  of  lead  is  retained. 

In  both  cases,  the  lead  produced  is  a 
sulphate,  and  in  this  shape  it  should  be 
weighed,  and  from  the  result  the  amount 
of  the  former  alone  may  be  easily  calcu- 
lated, as  will  be  seen  from  the  sequel. 

Sulphate  of  lead  consists,  in  100  parts  by 
weight,  of 

Oxide  of  lead  .  73.56 
Sulphuric  acid  .  26.44 

100.00 


ASSAY   OF    LEAD   ORES   BY    A   WET   PROCESS.  215 

and  the  oxide  of  lead,  again,  of 

Lead 92.83 

Oxygen      ....  7.17 

Hence  we  say,  if  100  parts  of  oxide  of  lead 
contain  92.83  of  pure  lead,  then  73.56  of 
pure  lead  contain  68.285748  parts;  or,  in 
other  words,  sulphate  of  lead  consists  ol 

Lead  .  .  .  68.285748 
Oxygen  .  .  .  5.274252' 
Sulphuric  acid  .  26.440000 


100.000000 

For  this  assay  about  twenty  grains  only 
need  be  taken.  A  smaller  amount  might 
make  us  incapable  of  finding  the  real  quan- 
tity of  lead,  while  a  larger  one  would  only 
give  us  unnecessary  trouble. 


216 


XXIV. 

Gravimetric  Analyses  of  Lead  Ores. 

AT  Bleiberg,  in  Carinthia,  this  method  is 
executed  for  pure  galenas  as  follows :  De- 
compose 2  grammes  of  the  ore  with  concen- 
trated nitric  acid,  add  a  few  drops  of  sul- 
phuric acid,  evaporate  nearly  to  dryness, 
soften  the  mass  in  water,  wash,  digest  the 
contents  of  the  filter  (lead  sulphates,  cal- 
cium and  barium,  sulphur,  silica)  with 
concentrated  soda  solution  for  one  hour  in 
order  to  convert  the  sulphate  of  lead  into 
carbonate,  filter,  wash  the  filter  until  a  drop 
of  the  filtrate  no  longer  shows  turbidity 
with  barium  chloride,  boil  the  residue  with 
dilute  nitric  acid  or  with  acetic  acid,  wash 
with  water  until  acid  reaction  ceases,  pre- 
cipitate the  lead  with  as  little  sulphuric 
acid  as  possible  (an  excess  of  acid  also  pre- 


GRAVIMETRIC  ANALYSES  OF  LEAD  ORES.  217 

cipitates  lime),  filter  off  the  sulphate  of 
lead,  wash,  dry  and  heat  to  a  red  heat, 
whereby  differences  exceeding  0.1  per  cent, 
should  not  occur.  In  order  to  avoid  with 
ores  poor  in  lead  and  rich  in  lime,  bringing 
from  the  start  too  much  calcium  sulphate 
amongst  the  lead  sulphate,  the  evaporation 
of  the  nitric  acid  solution  with  sulphuric 
acid  is  not  carried  quite  so  far,  arid  the  so- 
lution diluted  with  J  liter  water  before  add- 
ing the  sulphuric  acid. 

Storer  decomposes  2  to  3  grammes  of 
galena  with  a  regulus  of  zinc  6  millimetres 
in  diameter  and  7  millimetres  thick,  and 
100  to  150  cubic  centimetres  of  hydro- 
chloric acid  diluted  with  four  times  the 
quantity  of  water,  and  heated  to  122°  F. 
for  15  to  20  minutes.  He  then  decants  the 
metallic  lead,  separated  under  the  develop- 
ment of  sulphuretted  hydrogen,  with  hot 
water,  cleanses  the  cylinder  of  zinc  by  rub- 
ing  with  the  finger  and  rinsing,  and  dries 
the  lead  in  a  tared  porcelain  crucible  at  a 


218  THE  ASSAYER'S  GUIDE. 

moderate  temperature  in  a  current  of  illu- 
minating gas,  or  in  the  air-bath.  In  the 
presence  of  insoluble  gangues  the  lead  is  dis- 
solved from  them  by  means  of  nitric  acid  and 
the  residue  weighed.  Other  metals  precip- 
itable  by  zinc  have  to  be  separately  deter- 
mined by  special  assays,  and  deducted  from 
the  lead.  Since  the  lead  sponge  is  readily 
oxidizable,  Boessler  fixes  it  on  a  weighed 
quantity  of  Wood's  metal  (1  part  Bi,  0.5 
Pb,  0.25  Sn,  0.25  Cd),  and  finds  the  lead 
from  the  increased  weight  of  the  regulus. 


219 


XXV. 
Assay  of  Iron  Ores  by  Heat. 

ONE  part  of  the  ore,  about  a  hundred 
grains,  thoroughly  pulverized,  is  mixed  with 
from  thirty  to  a  hundred  0/ains  of  calcined 
borax.  The  quantity  of  the  latter  varies 
according  to  the  purity  of  the  mineral,  and 
increases  when  it  contains  many  foreign 
admixtures. 

If  the  ore  contains  sulphur,  it  ought  first 
to  be  roasted,  as  was  the  case  with  the 
assays  of  other  metals  already  described. 

A  Hessian  crucible  is  then  prepared  with 
coal,  as  already  directed  in  the  description 
of  those  vessels  under  the  head  of  Utensils 
and  Implements.  Into  the  hollow  in  the 
centre,  the  mixture  of  ore  and  borax  is 
poured,  and  on  that  some  charcoal  powder; 
after  which  the  cavity  is  entirely  covered 


220  THE   ASSAYS  R'S   GUIDE. 

with  a  piece  of  charcoal.  The  crucible  is 
then  closed,  the  number  of  the  assay  being 
marked  on  the  inner  surface  of  the  cover. 
This  is  then  fastened  down  air-tight  with 
some  putty. 

The  iron  ore,  after  these  preliminary 
arrangements,  is  to  be  submitted  to  a  reduc- 
tion process  in  the  furnace,  fig.  6,  Plate  L, 
which  lasts  about  three-quarters  of  an 
hour. 

At  the  extensive  iron- works  on  the  Hartz 
Mountains  in  the  interior  of  Germany,  a 
very  simple  apparatus  is  used  instead  of 
the  other  furnace,  of  which,  on  account  of 
its  portability,  I  here  give  a  description. 
It  consists  simply  of  an  open  cast-iron  pot 
or  jar,  measuring  about  a  foot  across,  and 
one  and  a  half  in  height,  and  having  a 
plate  of  sheet-iron,  perforated  with  many 
little  holes  an  inch  in  diameter,  instead  of 
a  grate.  This  leaves  a  vacant  space  of 
about  two  inches  below,  to  receive  the 
ashes.  The  latter  partition  has  two  open 


ASSAY   OF   IRON    ORES   BY   HEAT.  221 

;  one,  the  door  to  take  out  these  cin- 
ders —the  other,  to  introduce  the  end  of  the 
bellows.  Above  the  iron  plate,  on  which 
the  crucibles  are  directly  placed,  without 
any  brick,  a  coating  of  fire-clay,  an  inch 
thick,  extends  to  the  mouth  of  the  jar. 

The  latter  is  furthermore  supplied  with 
three  or  four  short  legs,  and  a  handle  on 
each  side. 

In  this  furnace  the  process  lasts  about 
an  hour  and  a  quarter, 

In  both  cases,  the  button  produced  con- 
tains exactly  the  same  impurities,  carbon, 
earths,  acids,  or  other  metals,  as  pig-iron 
would,  if  procured  from  the  same  ore,  and 
therefore  this  assay  is  only  to  be  used  for 
furnaces.  For  these  it  entirely  suffices; 
but  to  ascertain  the  true  amount  of  pure 
iron,  the  wet  analysis  should  be  resorted  to, 
the  same  as  with  other  ores ;  and  it  is  for 
this  that  I  shall  give  directions  in  the  next 
chapter  how  to  discover  or  calculate  the 
real  per-centage  of  the  pure  metal,  or  to 


222  THE  ASSAYER'S  GUIDE,. 

assay  the  pig-iron  produced  in  the  process 
by  heat. 

It  may  not  be  uninteresting  to  many, 
who  may  honour  these  pages  with  their 
perusal,  to  become  acquainted  with  a  me- 
thod for  obtaining  chemically  pure  iron, 
as  given  by  Karsten  in  his  famous  and 
voluminous  works  on  this  metal.  It  is 
described  in  vol.  i.,  pages  167,  168.  He 
says,  to  procure  chemically  pure  iron,  take 
the  best  bar-iron  of  commerce,  e.  g.  Swedish 
iron  in  the  shape  of  small  wire ;  cut  it  up 
in  short  pieces,  and  then  mixing  it  with 
about  a  fourth  part  by  weight  of  oxide  of 
the  same  metal,  melt  it  in  a  Hessian  cru- 
cible. To  cover  it,  use  a  compound  flux, 
consisting  of  pure  quartz,  pure  lime,  and 
equally  pure  carbonate  of  potash,  in  pro- 
portions capable  of  furnishing  a  glass  or 
slag,  not  flowing  too  easily,  but  of  rather  a 
tough  consistency. 

For  the  manufacture  of  an  oxide  of  iron, 
free  from  all  admixtures  of  foreign  metals, 


ASSAY  OF  IRON  UKES  BY  HEAT.      223 

it  is  best  to  use  small  clean  wire,  oxidizing 
it  by  vapours  of  watei 

The  button  thus  produced  has  a  re- 
markably white  colour,  a  strong  metallic 
lustre,  and  is  more  ductile  than  the  best 
varieties  of  soft  bar-iron.  Particularly  cha- 
racteristic, however,  is  its  great  specific 
gravity,  amounting  to  7.9654,  while  that 
of  wrought-iron  is  7.6  to  7.9,  and  of  cast- 
iron  only  from  7.0  to  7.5.  The  only  im- 
purity this  metal  may  be  discovered  to 
possess  occurs  as  slight  traces  of  silicium. 
and  therefore  it  may  be  considered  to  be  ass 
pure  as  it  possibly  can  be  made,  even  by  a 
process  conducted  only  upon  the  rules  and 
principles  of  wet  analysis,  and  thus  in  this 
shape  it  is  utterly  unknown  to  the  mere 
practical  metallurgist  or  smelter. 


224 


XXVI. 

s  Process  for  Iron  Ores  and  Iran. 


THIS  method,  though  remarkable  for  ite 
simplicity,  is  a  very  sure  one,  not  only  to 
ascertain  the  quantity  of  iron  in  an  ore,  but 
to  acquaint  us  with  the  peculiar  degree  of 
oxidation  in  which  it  exists,  and  also  the 
amount  of  each  oxide,  which  it  is  often  not 
only  very  interesting,  but  useful  to  know. 
Many  ores,  particularly  the  magnetic  ones, 
contain  both  the  peroxide  and  the  prot- 
oxide, and  the  only  ones  to  which  this 
process  cannot  be  applied  are  those  con- 
taining arsenious  acid,  not  a  very  common 
ingredient. 

The  process  discovered  or  invented  by 
Fuchs  is  founded  on  the  fact,  that  chemically 
pure  muriatic  acid,  when  atmospheric  air  is 
excluded,  is  incapable  of  dissolving  anv 


copper;  but  that,  when  peroxide  of  iron  is 
contained  in  it,  a  corresponding  quantity  of 
that  metal  becomes  soluble,  a  muriate  or 
chloride  of  iron  and  chloride  of  copper  being 
thus  formed. 

The  ore  is  dissolved  in  muriatic  acid,  and, 
if  necessary,  filtered.  A  small  round-bot- 
tomed vial  should  be  used.  Into  the  solu- 
tion a  clean  weighed  strip  of  copper  is 
placed,  and  the  vessel  corked,  and  covered 
with  a  piece  of  bladder,  tied  down  round 

-* 

the  neck  until  we  are  ready  to  boil  it. 
This  is  best  done  in  a  water-bath,  and 
should  last  until  no  more  copper  is  received 
by  the  acid.  The  former  is  then  taken  out, 
well  washed  in  water,  dried  with  a  towel, 
and  immediately  weighed. 

The  difference  in  the  weight  of  the 
copper  is  all  that  is  required  to  ascertain 
the  amount  of  peroxide  of  iron  in  the  ore, 
for  we  need  only  multiply  this  by  the 
equivalent  of  peroxide  of  iron,  which  Fuchs 
takes  to  be  40,  and  divide  the  product  by 

15* 


226  THE   ASSAYE?/S   GUIDE. 

31.7,  the  equivalent  of  copper.  The  quo- 
tient gives  the  quantity  of  peroxide  con- 
tained in  the  solution  or  ore. 

To  know  the  whole  amount  of  iron  in  it, 
we  need  only  weigh  off  another  part.  (10 — 
15  grs.,)  dissolve  it  in  muriatic  acid,  and 
then  digest  with  chlorate  of  potash,  to 
transform  the  protoxide  into  peroxide,  after 
which,  copper  will  decompose  the  whole. 
Indtead  of  40,  the  equivalent  of  peroxide 
of  iron,  we  insert  28,  the  equivalent  of  the 
pure  metal,  into  our  calculations.  By  sub- 
tracting the  amount  of  the  peroxide  from 
the  last  result,  the  amount  of  the  protoxide 
is  found. 

The  presence  of  alumina,  silica,  &c.  has 
no  effect  on  this  assay,  though  the  existence 
of  copper  in  it  would  represent  the  ore  as 
poorer  than  it  really  is.  The  latter,  how- 
evei,  rarely  occurs  in  common  iron  or  its 
ores  except  in  mere  traces,  and,  as  such,  it 
produces  no  material  difference. 


227 


XXVII. 

Swedish  Assay  of  Iron   Ores. 

THE  following  dry  method  of  assaying 
iron  ores  is  still  much  employed  in  Swe- 
dish works,  and  though  the  results  obtained 
are  less  accurate  than  most  of  those  ob- 
tained in  the  wet  way,  they  approximate 
much  more  nearly  to  the  economic  value  of 
an  iron  ore  when  smelted  on  a  large  scale. 
The  yield  of  crude  iron  from  the  ores,  as 
well  as  the  approximate  content  of  iron, 
is  obtained  by  multiplying  the  weight  of 
the  resulting  button  of  crude  iron  by  0.95. 
Only  iron  ores  very  rich  in  manganese  have 
to  be  directly  assayed  as  to  their  content  of 
iron.  The  ores  delivered  at  the  works  are 
first  assayed  in  the  dry  way  in  order  to 
determine  the  yield  of  iron,  the  nature  of 
the  iron,  the  behavior  in  smelting,  etc. 


228  THE  ASS  AVER'S  GUIDE. 

The  required  assay-sample  is  obtained  by 
taking  pieces  up  to  200  Ibs.  or  more  in 
weight  from  the  circumference  and  interior 
of  the  ore-pile  and  reducing  them  to  pow- 
der. The  powder,  thoroughly  mixed,  is 
formed  into  a  conical  heap,  which  is  divided 
into  several  parts.  One  or  two  of  these 
parts  are  then  taken  and  again  formed  into 
a  heap,  which  is  divided  as  before.  This 
reduction  is  several  times  repeated  until 
finally  2  to  4  Ibs.  of  the  sample  remain, 
which  are  passed  through  a  sieve  having 
40  to  60  meshes  to  the  linear  inch,  and 
dried  at  from  230°  to  248°  F. 

The  aim  in  executing  the  assay  is  to 
reduce  the  oxidized  iron,  to  carbonize  the 
reduced  iron,  and  to  melt  to  a  slag  the 
admixed  earthy  matter.  To  effect  the  lat- 
ter, silica,  alumina  and  lime  must  be  brought 
together  in  suitable  proportion  about  56  :  14 
:  30  (bisilicate).  In  order  to  approximate 
this  proportion,  it  is  best  to  make  a  pre- 
liminary assay  in  the  wet  way  for  the  de» 


SWEDISH   ASSAY  OF   IRON   ORES.  229 

termination  of  the  earthy  matter  present. 
For  this  purpose  Berthier  recommends  the 
following  process : — 

A  weighed  quantity  of  the  finely  pow- 
dered ore  is  heated  to  redness  in  a  porcelain 
crucible ;  the  loss  of  weight  gives  the  amount 
of  water,  carbonic  acid,  and  other  volatile 
matters  present.  Another  weighed  portion 
is  heated  with  dilute  nitric  acid,  which  dis- 
solves out  carbonates  of  lime  and  magne- 
sium ;  the  residue  contains,  under  ordinary 
circumstances,  only  oxide  of  iron,  clay  and 
quartz,  the  difference  giving  the  amount  of 
the  earthy  carbonates.  A  third  portion  is 
treated  with  strong  hydrochloric  acid, 
whereby  the  carbonates  of  lime  and  mag- 
nesium and  the  oxides  of  iron  ore  are  dis- 
solved out,  leaving  an  insoluble  residue  of 
quartz  and  clay.  This  is  weighed,  the 
oxides  of  iron  being  determined  from  the 
difference  of  weight  by  deducting  that  of 
the  carbonates  previously  found.  From 
these  results  the  proportion  of  fluxes  neces- 


230 


THE  ASSAYER'S  GUIDE. 


sary  to  be  added  can  be  approximately  de- 
termined, with  a  view  to  produce  an  easily 
fusible  slag. 

In  many  instances,  however,  this  pre- 
liminary assay  can  be  dispensed  with,  as  a 
sufficiently  good  idea  of  the  nature  of  the 
fluxes  to  be  added  can  be  determined  by  the 
appearance  of  the  ore  alone.  Calcareous 
ores  effervesce  with  acids-;  clayey  ores,  when 
breathed  upon,  give  the  characteristic  odor 
of  clay  and  adhere  to  the  tongue,  while 
siliceous  ores  give  sparks  when  struck  with 
the  steel.  According  to  experience,  the 
following  quantities  of  flux  suffice  in  many 
cases  : 


MATERIALS. 

Chalk, 
per  cent. 

Fluor- 
spar, 
per  cent. 

China 
clay, 
per  cent. 

10 
5 
25 
20 
25  to  30 
25  to  30 

25 
25 
25 
20  to  25 
25  to  30 
25  to  30 
20  to  25 
25 
20  to  25 

10  to  15 

specular  iron  ore          

red  hematite  iron  ore    

brown  iron  ore 

argillaceous  iron  ore  

spathic  iron  ore        ... 

20  to  25 
20  to  25 

finery  cinders  .  ...        ....      i 

SWEDISH   ASSAY   OF   IKON   ORES.  231 

According  to  the  above  table,  for  siliceous 
and  argillaceous  iron  ores  a  flux  of  20  to  25 
per  cent,  of  chalk  and  20  to  30  per  cent,  of 
fluor-spar  is  as  a  rule  sufficient.  However, 
in  many  cases,  especially  with  poor  ores, 
the  flux  will  have  to  be  increased  to  50  per 
cent,  or  more.  When  alumina  is  wanting, 
5  to  15  per  cent,  of  China  clay  is  added. 
From  the  character  of  the  slag  obtained  in 
melting  it  can  readily  be  recognized  whether 
the  correct  proportion  of  earths  has  been 
used.  If  the  slag  is  translucent,  has  a  gray, 
yellowish  or  violet  (not  green)  color,  and  is 
enamel-like  with  conchoidal  fracture,  lime, 
clay  and  silica  are  in  the  proper  propor- 
tions. If  there  is  too  much  silica  in  the 
flux,  the  slag  has  a  greenish  tint,  is  glassy, 
more  or  less  completely  transparent,  easily 
broken  with  a  conchoidal  fracture  and  sharp 
edges.  Should  the  charge  be  fritted,  pul- 
verulent, and  the  iron  diffused  in  minute 
particles,  the  flux  has  been  wrongly  pro- 
portioned, or  the  temperature  too  low. 


232  THE  ASSAYER'S  GUIDE. 

This  is  apt  to  happen  with  ores  containing 
a  large  proportion  of  lime  and  magnesium, 
as  they  are  always  refractory,  and  require 
the  addition  of  a  large  proportion  of  silica 
and  lime.  If  the  slag  is  but  half  fused  and 
dark  in  color,  the  ore  contains  an  excess  of 
silica  or  silicates  of  iron  and  manganese, 
which  react  on  the  carburetted  iron,  decom- 
posing it,  forming  malleable  iron  and  car- 
bonic acid,  giving  it  a  spongy  appearance. 
In  this  case  lime  should  be  added.  The 
presence  of  a  small  amount  of  manganese 
is  indicated  by  the  amethystine  color  of 
the  slag ;  larger  amounts  render  it  olive 
green,  yellowish  or  brown.  Titaniferous 
ores  are  apt  to  render  the  slag  copper-colored 
by  the  formation  of  cyano-nitride  of  titan- 
ium. Chromic  iron  ores  produce  a  resinous 
and  dark-colored  slag  which  is  sometimes 
surrounded  with  a  thin  metallic  layer.  A 
stony,  earthy  slag  with  rough  fracture  and 
a  gray,  yellow  or  brown  color,  indicates  a 
large  content  of  bases.  With  a  considerable 


SWEDISH  ASSAY  OF  IRON  ORES. 

excess  of  lime  the  slag  on  being  touched 
crumbles  to  a  powder.  Such  basic  slags 
with  a  stony  texture  may  correctly  give 
the  content  of  iron  if  the  button  is  not  too 
graphitic.  Iron  ores  containing  sulphur 
may  also  be  intentionally  charged  so  as  to 
obtain  a  basic  slag  in  order  to  learn  whether 
the  iron  button  proves  to  be  sufficiently  free 
from  sulphur.  Thus  Percy,  for  instance, 
recommends  the  formation  of  a  slag  with 
38  Si  02,  15  A12  03  and  47  Ca  0,  or  nearly 
21  parts  Si  02,  1  part  A12  03  and  3  parts 
Ca  0.  Such  slag  is  almost  formed  by  melt- 
ing together  the  following  fluxes  : 

l9i  JS102 1.75(35 

Wass  2*  |  other  constants  =  A12O3  0.75  \  15 

Lime 2.50(50 

The  following  fluxes  have  also  been 
recommended  as  adapted  to  ores  or  metal- 
lurgical products,  which  would  be  classed 
under  the  following  several  general  heads. 
The  proportions  given  are  for  0.65  gramme 
(10  grains)  of  ore  : — 


THE  ASSAYER'S  GUIDE. 

1.  Ores  nearly  free  from  gangue,  some 
varieties  of  magnetite,  red  and  brown  hem- 
atite, specular  iron  ore  and  micaceous  iron 
ore  : — 

Parts.  Parts. 

China  clay 2  Lime 2£  to  3 

Lime 2£  Blast-furnace  slag.  5 

Sand Otol  Fluor-spar 5 

Glass 2  to  2 & 

2.  Ores,  etc.,  containing  silica,  varieties 
of  limonite  or  brown  iron  ore,  refinery  slag 
(tap),  and  flue  cinders : — 

Parts.  Parts. 

Glass Ito2£        China  clay 2 

Lime 2i  to  4         Lime 3£  to  4 

3.  Ores   containing   carbonates  of  lime, 
magnesia,    protoxide   of    manganese,   etc., 
calcareous  hematites,  and  spathic  ores : — 

Parts.  Parts. 

China  clay 2  Glass 3   to  4 

Lime 1J  Lime 1J  to  2 

Sand..  .  1 


SWEDISH   ASSAY  OF  IRON  ORES.  235 

4.  Ores   containing   silica   and  alumina, 
clay  iron  ores,  etc. : — 

Parts.  Parts. 

Glass 0    to  2*      China  clay 0   to  2 

Lime 2J  to  3        Lime 2    to  3 

5.  Titaniferous  ores,  or  ores  containing 
titanium : — 

Parts.  Parts. 

Lime 3  Glass 2£ 

Glass 2  Lime H 

China  clay 2  China  clay 1 

Lime 2J 

The  dry  assay  of  iron  ores  is  performed  as 
follows :  Mix  the  finely  pulverized  ore  with 
the  required  quantity  of  flux  and  transfer  it 
to  a  basqued  or  charcoal-lined  crucible.  The 
basqued  crucibles  are  prepared  as  follows : 
The  charcoal  powder  is  mixed  with  just 
sufficient  gum-water  or  molasses  to  make  it 
cohere  readily.  The  crucible  is  gently 
rammed  full  of  this  charcoal,  and  a  cylin- 
drical cavity  of  sufficient  size  to  contain 


236  THE  ASSAYER'S  GUIDE. 

the  charge  is  made  in  it  with  a  spatula  01 
some  other  boring  instrument.  The  cru- 
cibles best  adapted  for  this  assay  are  made 
of  a  mixture  composed  of  two  parts  unburnt 
and  one  part  burnt  clay.  They  are  about 
II  inches  high  and  li  inches  in  diameter 
at  the  top.  As  the  amount  of  ore  in  the 
charges  never  exceeds  from  0.64  to  0.96 
gramme,  four  crucibles  are  placed  in  the 
furnace  at  a  time.  The  charges  in  each 
are  exactly  alike,  and  if  there  is  but  a 
slight  variation  in  the  weight  of  the  result- 
ing buttons,  the  assay  is  probably  correct; 
the  mean  weight  of  the  four  should  be  taken 
as  the  result.  It  is  generally  best  to  stand  the 
four  crucibles  on  a  half  brick,  or  lute  them 
to  it.  so  that  when  the  fusion  is  finished  all 
the  crucibles  can  be  removed  from  the  fur- 
nace at  one  time.  Although  lids  are  some- 
times used  to  cover  the  crucibles,  it  is  better, 
after  the  charge  has  been  introduced,  to  stop 
the  cavity  with  a  charcoal  plug  and  to  cover 
the  entire  top  of  the  crucible  with  a  clay 


SWEDISH   ASSAY  OF  IRON  ORES.  237 

luting.  The  half  brick  holding  the  cru- 
cibles should  be  placed  near  or  directly 
upon  the  fire-bars  at  the  bottom  of  the  fur- 
nace and  the  anthracite  or  coke  fire  built 
up  around  and  over  the  crucibles.  When  the 
latter  have  been  in  the  fire  about  li  to  2 
hours,  and  a  white  heat  has  been  reached 
and  maintained  through  a  considerable  part 
of  this  period,  the  assay  may  be  considered 
finished  and  the  crucibles  removed.  When 
the  crucibles  are  cold  they  are  broken  up, 
the  metallic  buttons  and  globules  *  which 
may  adhere  to  the  charcoal  lining  and  slag 
are  separated  out  with  a  magnet.  The  ap- 
pearance of  the  slag,  which  has  previously 
been  referred  to,  as  well  as  the  character 
of  the  iron  buttons,  serve  for  judging  the 
assay.  If  the  ores  are  easily  reducible  and 
the  proper  temperature  has  been  reached 
and  maintained  in  the  furnace,  the  buttons 

*  The  formation  of  these  globules  is  prevented  by  not 
allowing  any  fine  particles  of  charcoal  or  dirt  to 'get  into 
the  cavity  when  it  is  being  charged. 


238 

should  be  dark,  tough  and,  if  they  have  not 
been  cooled  too  quickly,  graphitic.  As  a 
general  thing  the  iron  buttons  are  dark 
gray  or  mottled  according  to  the  condition 
and  amount  of  carbon  they  contain.  If  the 
crucibles  are  allowed  to  cool  very  slowly, 
the  buttons  are,  as  a  rule,  very  graphitic, 
but  if  cooled  quickly  are  fine-grained  and 
white,  or  grayish  in  color.  The  presence 
of  phosphorus  generally  renders  the  buttons 
white,  hard  and  brittle ;  sulphur  produces 
a  mottled  or  reticulated  structure;  man- 
ganese, a  hard,  white  crystalline  or  close- 
grained  iron ;  titanium,  a  dull,  dark-gray 
button  with  a  crystalline  fracture;  chro- 
mium, a  well-fused  button,  with  a  tin-white, 
bright  crystalline  fracture,  to  a  semi-fused, 
white,  or  light  gray,  spongy  mass,  accord- 
ing to  the  amount  of  chromium  in  the 
iron. 

A  content  of  sulphur  may  also  be  recog- 
nized by  the  odor  of  sulphuretted  hydrogen, 
or  the  brownish  coloration  of  a  lead-paper  on 


SWEDISH    ASSAY   OF   IRON   ORES.  239 

pouring  hydrochloric  acid  over  the  regulus. 
By  bringing  a  sheet  of  silver  over  a  weighed 
quantity  of  the  button  thus  treated,  the 
former  is  colored  the  darker  the  more  sul- 
phur is  present.  By  the  degree  of  colora- 
tion it  may,  with  some  experience,  be 
judged  whether  the  iron  is  suitable  for  this 
or  the  other  purpose. 

In  England  the  assay  of  iron  is  also  exe- 
cuted in  large  unlined  crucibles  by  mixing 
the  ore  with  the  previously  mentioned 
fluxes  (glass  and  lime)  and  pulverized  char- 
coal, coke  or  anthracite.  The  ore  and 
fluxes  should  be  pulverized  and  passed 
through  a  60-mesh  sieve.  With  a  series, 
of  four,  the  ore  and  fluxes  may  be  pro- 
portioned as  follows : — 

1  and  2. 

Ore 500  grains  (32     grammes) 

Glass 250     "       (16     grammes) 

Lime 300     "       (19.2  grammes) 

3  and  4. 

Ore 500  grains  (32     grammes) 

China  clay. c*.  ..200     "       (12.8  grammes) 


240 

Sand 50  grains  (  3. 2  grammes) 

Lime 250     "       (16     grammes) 

The  reducing  agent  employed  is  prefer- 
ably anthracite,  but  charcoal  or  coke  may 
be  used.  In  any  case  it  should  be  pulver- 
ized and  passed  through  a  60  mesh  sieve. 
The  following  amounts  are  respectively 
used : 


1 .  80  grains  (5. 1 2  grammes) 

2.  110     "      (7. 04  grammes) 


3.  1 20  grains  (7. 68  grammes) 

4.  150     "      (9. 60  grammes) 


Mix  the  fluxes  and  reducing  agents 
thoroughly  with  the  ore,  transfer  to  a  cru- 
cible about  4  inches  high  by  li  inches  in 
diameter.  Lute  the  cover  on  with  clay, 
place  on  a  piece  of  fire-brick  and  heat  in 
the  usual  manner  for  an  hour  or  more.  In 
lifting  the  crucible  out  of  the  furnace,  care 
must  be  taken  to  shake  it  as  little  as  pos- 
sible in  order  to  avoid  disseminating  glob- 
ules of  iron  in  the  slag.  When  cold,  break 
open  the  crucible,  and  collect  any  small 
buttons  or  shots  of  metal  in  the  slag  with  a 


SWEDISH   ASSAY  OF   IRON   ORES.  241 

magnet.  Weigh,  then  fracture  the  largest 
button  and  note  the  character  of  the  iron. 
If  the  above  scheme  has  been  carefully  car- 
ried out,  using  an  ordinary  hematite  or 
magnetic  ore,  the  results  will  be  something 
like  as  follows  : — 

1.  Not  being  sufficient  carbon   present, 
the  ore  is  not  all  reduced ;  the  reduced  and 
unreduced  ore  being  fritted  together  with 
slag  in  an  irregular  lump. 

2.  Ore  completely  reduced  and  fused  into 
a  button.     Iron,  gray.     Slag,  glassy,  and 
transparent,  or  perhaps  dark-grayish,  and 
opaque. 

3.  Ore  completely  reduced  and  fused  into 
a  well-melted  button.    Iron,  gray  to  grayish 
white.       Slag,    clear,     glassy    and     trans- 
parent; color,  gray   to  greenish  by  trans- 
mitted light. 

4.  Ore  completely  reduced,  but  owing  to 
the  excess  of  carbon  present  the  metal  is 
disseminated    through    the    slag    in    small 

16 


242 

shots  or  globules.    Iron,  gray.    Slag,  glassy, 
opaque  or  translucent. 

There  should  always  be  present  an  excess 
of  the  amount  of  carbon  necessary  to  re- 
duce the  ore.  100  parts  by  weight  of 
sesquioxide  of  iron  require  22  £  parts  of 
carbon  for  reduction.  Consequently  the 
amount  added  must  be  adjusted  according 
to  the  oxide  of  iron  present. 


243 


XXVIII. 

Assay  of  Quiclmlver  Ores. 

THIS  metal  is  one  of  those  which  some- 
times occur  in  the  virgin  state,  though  by 
far  the  most  common  shape  in  which  it 
presents  itself  is  the  bisulphuret,  commonly 
termed  cinnabar,  which  in  its  perfectly 
pure  state  consists  of: — 

Mercury     .     .     -.     .     86.287 
Sulphur     .     ...     .    13.713 


100.000 

Its  formula  being  Hg  S.     A  specimen  from 
Japan,  analyzed  by  Klaproth,  gave: — 
Mercury     .     .     T    ..    84.50 
Sulphur      .    .    .     .     14.75 

99.25 
i 
Which,   though    it    must  have   contained 


244  THE   ASSAYEIl'S   GUIDE. 

0.75  of  other  ingredients  not  mentioned 
in  the  analysis,  shows  that  it  possessed 
as  much  as,  according  to  the  above-calcu- 
lated composition,  it  could  be  expected  to 
contain. 

It  is  not  the  place  here  to  give  the 
analyses  of  other  casual  occurrences  of 
this  metal,  such  as  perhaps  are  only  to  be 
found  in  the  cabinet  of  the  mineralogist; 
and  I  shall  therefore  proceed  to  describe 
the  manner  in  which  the  assays  of  mercurial 
ores  are  performed. 

In  all  cases  the  mercury  is  procured  by 
simple  distillation,  for  which  purpose,  wher; 
not  originally  uncombined,  it  is  necessary 
first  to  disengage  it. 

In  distilling  quicksilver,  an  iron  retort 
covered  outside  with  a  coating  of  clay  is 
commonly  used.  The  neck  should  be  so 
contrived  that  it  can  be  unscrewed,  to 
facilitate  cleaning  the  interior.  Retorts  or 
tubes  of  clay,  glazed  externally,  are  also 
applicable,  and  are  preferred  by  some;  but 


ASSAY  OF  QUICKSILVER  ORES.      24o 

those  of  iron  are  safer,  inasmuch  as  the 
vapors  of  mercury  cannot  possibly  pene- 
trate and  escape  through  them. 

To  produce  the  necessary  heat,  which 
should  not  exceed  a  mild  red,  any  conve- 
nient furnace,  such  as  the  one  described  on 
page  220,  will  answer. 

Any  tumbler  or  beaker-glass  containing 
cold  water  may  be  employed  as  a  condenser. 
It  must,  however,  be  remarked  here  that 
the  mouth  of  the  retort  ought  not  to  be 
inserted  into  the  water,  because  in  that  case, 
on  cooling,  the  water  would  rise  up  into  it. 
To  avoid  this,  and  yet  to  prevent  the  escape 
of  the  mercurial  vapors,  a  wet  wrapper  of 
paper  or  linen  is  bound  round  the  neck  of 
the  retort,  protruding  sufficiently  to  permit 
of  the  other  end  being  completely  immersed 
in  the  water.  Some  assayers  employ  a  little 
bag  tightly  attached  to  the  retort.  . 

The  fluxes  used  are  various,  and,  accord- 
ing to  their  efficiency,  may  be  enumerated 
thus,  the  first  being  the  best : — 


24f>  THE  ASSAYER'S  GUIDE. 

Black  llux,  from    one-half  to  full  weight  of  ore 
Carbonate  of  soda  or  of  potash,  one-half  "         " 
Iron  filings,  from  a  quarter  to  a  half         "         " 
Carbonate  of  lime,  one-half  to  full  "         " 

With  charcoal  powder,  one-tenth  to  one-eighth    " 

The  black  flux  produces  with  cinnabar 
besides  liberating  the  mercury,  sulphuret  of 
potassium,  while  sulphates  of  soda  and  of 
potash  are  formed  from  the  carbonates, 
The  iron  filings  simply  cause  the  formation 
of  protosulphuret  of  iron,  while  the  quick- 
silver is  disengaged.  The  alkaline  fluxes 
are  chiefly  used  with  the  iron  retorts.  If 
the  quicksilver  is  known  to  exist  only  in 
its  virgin  uncombined  state,  no  flux  is  re- 
quired, and  we  may  immediately  proceed 
to  distil  it  over. 

It  has  been  remarked  above  that  the  heat 
employed  during  the  assay  should  not 
exceed  a  moderate  red.  This  point  is  of 
great  consequence  with  cinnabar,  because 
this  sulphuret  is  capable  of  being  sublimated 
in  its  undecomposed  state,  if  the  heat  is  in 
creased  beyond  that  temperature.  If  the 


ASSAY   OF    QUICKSILVER    ORES.  247 

ore  contain  chloride  or  bromide  of  mercury, 
these,  too,  will  pass  over;  and,  to  avoid  this, 
the  ore,  if  their  presence  is  suspected,  must 
first  be  mixed  with  soda.  To  render  the 
mixing  more  intimate,  a  little  water  is  em- 
ployed, which  must,  however,  be  removed 
before  placing  the  ore  in  the  retort.  It  is 
also  advisable  to  apply  the  heat  gradually, 
and,  when  retorts  are  used,  to  be  particular 
that  they  are  everywhere  heated  equally, 
as  otherwise  quicksilver  might  be  condensed 
in  the  interior  of  the  retort.  When  it  has 
Oeen  ascertained  that  drops  of  quicksilvei 
are  no  longer  leaving  the  retort  or  tube, 
and  therefore  that  the  process  is  about  being 
completed,  it  is  advisable  to  fire  up  a  little 
before  removing  the  receiving  vessel,  so  that 
particles  of  the  metal  condensed  in  the  neck 
of  the  retort  or  in  the  tube  may  be  forced  out , 
though,  to  insure  this  still  more,  it  is  neces- 
sary to  brush  out  the  neck  of  the  vessel 
with  a  little  brush  or  feather. 

The  quicksilver  which   has  collected  ID 


THE  ASSAYER'S  GUIDE. 

the  condensing  vessel  is  frequently  indis- 
posed to  join  and  form  a  connected  mass; 
but  this  is  easily  brought  about  by  boiling 
it  in  water.  Adhering  moisture  remaining 
when  the  water  is  decanted  should  be  re 
moved  with  blotting-paper. 

From  one-half  to  three  pounds  of  the  orf 
are  commonly  employed  for  the  assay,  de- 
creasing in  quantity  as  the  value  of  the  ore 
increases. 

Perfect  accuracy  can  never  be  attained 
in  the  assay  of  quicksilver  ores  by  heat, 
neither  as  regards  the  perfect  chemical 
purity  nor  the  full  amount  of  the  metal  pro- 
duced; but,  as  the  loss  and  impurity  are  yet 
greater  with  quicksilver  produced  on  a 
large  scale,  this  method  of  treating  the  ore 
will  be  sufficient  for  technical  purposes. 

Berthier,  in  the  Annales  des  Mines,  h 
se*rie,  t.  iii.  p.  820,  suggests  that  when  the 
ore  is  a  very  poor  one,  and  when  therefore 
the  large  amount  it  would  be  necessary  to 
use  might  be  the  cause  of  considerable  in- 


ASSAY   OF   QUICKSILVER   ORES.  249 

convenience  in  the  assay,  the  following  pre- 
paratory process  be  resorted  to.  The  ore 
should  be  digested  with  aqua  regia,  the 
supernatant  liquid  decanted  or  filtered  off, 
the  residue  thoroughly  washed  with  water, 
and  the  acid  solution,  together  with  the 
washings,  evaporated  to  dryness.  All  the 
quicksilver  in  the  shape  of  chloride  is  then 
contained  in  the  last-dried  residue,  and  can 
be  further  treated  in  the  dry  way,  only 
that,  as  above  remarked,  it  is  always  neces- 
sary carefully  to  mix  with  soda,  when 
choride  of  quicksilver  is  present. 

Before  closing  this  chapter  it  will  be  well 
to  describe  the  treatment  necessary  when  a 
quicksilver  ore  contains  arsenic.  I  shall 
literally  translate  the  remarks  of  BodemaD 
in  the  work  quoted  in  the  preface.  He 
says : — 

"  An  ore  from  Huanca-Ve*lica,  in  Peru, 
containing  arsenic  (red  sulphuret  of  arsenic, 
&c.)  and  cinnabar,  having  been  submitted 
to  Berthier's  inspection,  he,  after  various 


^"vJ  THE    ASSAYER  S    GUIDE. 

useless  experiments,  discovered  the  follow- 
ing process  to  be  the  most  adequate  for 
determining  the  mercury  in  it. 

"  The  ore  is  mixed  with  four  or  five  times 
its  weight  of  litharge,  and  then  heated  in  a 
retort.  A  flowing,  slag-like  mass  is  formed 
by  the  litharge,  sulphuret  of  arsenic,  &c.. 
while  the  cinnabar  is  decomposed  into  sul- 
phurous acid  and  metallic  mercury.  The 
quicksilver  is  completely  volatilized  by  a 
moderate  heat,  and  collected  in  the  condens- 
ing apparatus  and  the  farther  portion  of  the 
aeck  of  the  retort.  The  only  precaution 
necessary  during  the  operation  consists  in 
gradually  and  but  moderately  heating  the 
clay  or  glass  retort,  to  prevent  its  being 
perforated  by  the  effects  of  the  litharge  be- 
fore the  process  is  concluded." 

Electrolytic  determination  of  quicksilver. 
According  to  Escosura,  0.5  gramme  of  the 
ore  is  digested  with  10  to  15  cubic  centi- 
meters of  hydrochloric  acid  and  20  cubic 
centimeters  of  water  in  a  porcelain  dish. 


ASSAY   OF   QUICKSILVER   ORES.  251 

After  boiling  add  from  0.5  to  1  gramme  of 
potassium  chlorate  in  small  portions.  When 
decomposition  is  complete,  dilute  with  50 
cubic  centimeters  of  water  and  expel  free 
chlorine  by  continued  boiling.  In  order  to 
separate  selenium  or  tellurium,  if  present, 
add  20  to  30  cubic  centimeters  of  a  sat- 
urated solution  of  ammonium  sulphate  and 
boil  moderately.  When  the  insoluble  resi- 
due has  settled,  filter,  and  use  the  filtrate 
as  the  electrolytic  bath.  The  negative 
electrode  should  be  pure  gold,  and  the  posi- 
;ive  a  platinum  sheet.  The  solution  is 
subjected  to  the  galvanic  current  from  24 
to  30  hours.  The  increased  weight  of  the 
gold  equals  the  content  of  quicksilver. 
Two  Bunsen  cells  are  generally  sufficient. 
This  assay  may  also  be  executed  by  treat- 
ing the  finely  pulverized  ore  in  a  platinum 
dish  with  hydrochloric  acid,  ammonium 
sulphate,  and  water.  Of  10  per  cent,  ore 
only  0.2  gramme  is  used,  and  .of  0.1  per 
cent,  ore,  10  grammes.  The  platinum  dish 


252 

serves  as  the  negative  pole,  and  a  disk  of 
sheet-gold,  about  4  centimeters  in  diameter, 
as  the  positive  pole.  The  current  is  sup- 
plied by  6  Meidinger  cells,  and  the  quick- 
silver is  precipitated  in  24  hours. 

These  determinations  are  said  to  be 
very  accurate  and  are  exclusively  used 
at  Almaden. 

From  a  solution  of  its  salt  acidified  with 
nitric  acid,  mercury  is,  according  to  Classen, 
precipitated  on  the  negative  electrode  in  the 
form  of  a  mirror,  or  of  small  globules,  by  a 
current  of  0.2  to  0.5  cubic  centimeter  of 
oxyhydrogen  gas.  The  metal  adheres 
well  and  can  be  washed  without  loss.  The 
washing  must,  however,  be  done  without 
interrupting  the  current.  Insoluble  quick- 
silver compounds  may  easily  be  analyzed 
by  suspending  them  in  acidulated  water,  or 
in  a  dilute  solution  of  common  salt  (1:10) 
and  electrolyzing  as  usual. 


253 


XXIX. 

Dry  Assay  of  Tin   Ores. 

TIN  that  is  to  be  assayed  in  the  dry  way 
must  be  present  in  the  form  of  oxide.  The 
assay  proper  consists  of  applying  in  a  cru- 
cible at  a  high  temperature  reducing  and 
fluxing  re-agerits  which,  bring  the  stannic 
oxide  to  the  metallic  state  and  convert  the 
gangue  into  a  liquid  slag.  The  behavior 
of  stannic  oxide  and  of  metallic  tin  at  an 
elevated  temperature  causes,  however,  cer- 
tain difficulties,  which  make  the  results 
often  less  accurate  than  could  be  desired. 
These  difficulties  are : 

1.  That  some  of  the  resulting  metallic 
tin  is  liable  to  be  volatilized. 

2.  That    metallic   tin    decomposes    the 
alkali    carbonates  used    as  fluxes   forming 
stannates  which  enter  the  slag. 


254 

3.  That  at  the  temperature  required  to 
reduce    the   stannic   oxide,  other   metallic 
oxides  become  also  reduced  to  the  metallic 
state  and  alloy  with  the  resulting  tin  but- 
ton, and  vitiate  the  assay. 

4.  That  sulphates  are  reduced,  or,  if  sul- 
phides are  present,  they  combine  directly 
with  the  metallic  tin  and  carry  it  into  the 
slag. 

5.  That  the  gangue  in  the  ore  is  always 
siliceous.     This  causes  loss  as  the  stannic 
oxide,  while  passing  through  the  interme- 
diate state  of  stan nous  oxide,  combines  with 
silica  and  silicates. 

6.  That  stannic  oxide  is  liable,  before  its 
reduction  has   begun,  to  combine  with  the 
basic  fluxes  used  in  assaying  and  form  stan- 
nates ;  this  liability  increases  as  the  quan- 
tity of  flux  is  increased. 

Thus  it  will  be  seen  that  the  results  can 
be  too  high  (as  when  iron  enters  the  tin 
button)  or  too  low  (as  when  tin  is  carried 
off  in  the  slag  as  stannate,  sulphide,  or  sili- 


ASSAY   OF  TIN   ORES.  255 

cate),  and  that  all  impurities  should  be  re- 
moved, if  possible,  before  the  actual  dry 
assay  takes  place.  The  making  up  of  the 
charge  must  also  be  regulated  to  counteract 
as  much  as  possible  the  bad  influences  of 
the  basic  fluxes.  The  crucibles  used  in 
assaying  tin  ores  are  the  ordinary  clay  cru- 
cibles, the  plumbago  crucible,  and  the  porce- 
lain crucible.  Crucible  linings  are  unneces- 
sary. 

German  method  of  assay.  Five  grammes 
of  ore  are  intimately  mixed  with  0.75  to 
1  gramme  of  charcoal  dust,  and  charged 
into  a  clay  crucible ;  on  top  are  placed  12.5 
to  15  grammes  black  flux  (or  the  substi- 
tute: 2  parts  of  potassium-sodium-carbonate 
and  1  part  of  flour),  with  1  to  1.25  grammes 
borax-glass,  then  a  common  salt  cover,  and 
fin  ally  a  piece  of  charcoal.  The  crucible 
being  covered,  heat  in  a  muffle  or  a  pot-fur- 
nace at  a  moderate,  gradually  increasing  tem- 
perature, until  the  boiling  has  ceased,  and 
then  for  from  half  to  three-quarters  of  an 


256  THE  ASSAYER'S  GUIDE. 

hour  at  a  white  heat.  The  crucible  is  then 
removed  from  the  fire,  broken,  when  cool, 
and  the  tin  button  weighed. 

Mitchell  *  mixes  400  grains  ore,  100 
argol,  300  sodium  carbonate,  50  lime,  and 
charges  in  a  crucible  so  large  that.it  need 
only  be  half  filled ;  then  gives  a  cover 
of  sodium  carbonate  and  200  grains  of 
borax,  heats  gently  and  keeps'  for  at  least 
20  minutes  at  a  dull  red  heat,  increasing 
the  temperature,  until  tranquil  fusion  takes 
place. 

LevaTs  assay  with  potassium  cyanide.  A 
sufficient  quantity  of  powdered  potassium 
cyanide  is  rammed  into  a  capacious  porce- 
lain or  fire-clay  crucible  to  form  a  layer  of 
from  12  to  15  millimeters  thick.  Five 
grammes  of  the  .powdered  ore  intimately 
mixed  with  five  times  the  quantity  of  potas- 
sium cyanide  are  added  to  that  in  the  cru- 
cible, and  the  whole  is  covered  with  a  thin 
layer  of  the  cyanide.  The  charge  is  then 

* >Janual  of  Assaying;  New  York,  1881,  p.  48, 


DRY  ASSAY  OF  TIN  ORES.  257 

aeated  in  a  moderate  fire  until  it  fuses,  and 
is  kept  in  constant  fusion  for  10  minutes. 
The  crucible  is  then  taken  out  and  gently 
tapped  to  facilitate  the  formation  of  a  single 
button,  and  allowed  to  cool.  The  button 
is  then  freed  from  adhering  slag  by  water. 
In  case  copper  or  lead  is  present,  the  ore 
must  be  freed  from  them  before  reduction 
by  treating  it  with  acid.  This  is  the  most 
accurate  method  of  assaying  tin  (to  within 
one-half  per  cent.),  and  can  be  executed  in 
a  very  short  time.  In  case  the  ore  is 
siliceous,  a  mixture  of  10  grammes  of  ore, 
3  to  8  grammes  of  ferric  oxide,  and  40 
grammes  of  potassium  cyanide,  is  placed  in 
a  crucible  lined  with  charcoal.  The  mix- 
ture is  first  covered  with  potassium  cyanide 
and  then  with  powdered  charcoal.  The 
cover  is  luted  on  and  the  charge  heated  at 
a  high  temperature  for  one-half  to  one 
hour. 

In  any  case  it  is  always  better  to  mix  a 

small  quantity  of  powdered  charcoal  with 
17 


258  THE  ASSAYER'S  GUIDE. 

the  charge.  One-half  of  the  potassium 
cyanide  may  be  mixed  with  the  ore  and 
the  balance  used  to  cover  the  charge.  Care 
must  be  taken  not  to  allow  the  fire  to  become 
too  hot  or  the  charge  to  boil  over.  After 
pouring,  the  mould  must  not  be  moved 
until  the  slag  has  set,  otherwise  it  is  apt  to 
penetrate  into  the  button. 

Winklers  bronze  assay.  Five  grammes 
of  ore  are  mixed  with  5  grammes  of  cupric 
oxide  and  charged  in  a  clay  crucible ;  on 
top  are  placed  15  grammes  of  black  flux 
with  1.25  grammes  of  borax-glass,  then  a 
common  salt  cover,  and  finally  a  large  piece 
of  charcoal.  The  crucible  is  heated  in  a 
muffle  or  pot-furnace,  after  boiling  has 
ceased,  for  three-quarters  of  an  hour  to  an 
hour  at  a  bright-red  heat,  finishing  the 
assay  at  almost  a  white  heat.  The  result 
is  a  white,  brittle,  tin-copper  alloy.  With 
every  tin-assay,  an  assay  of  5  grammes  of 
cupric  oxide  with  the  same  charge  is  made, 
and  the  weight  of  the  resulting  button  of 


DRY    ASSAY   CF   TtX   ORES.  25 f* 

copper,  subtracted  from  the  bronze-button, 
gives  the  weight  of  the  tin  contained  in 
the  ore. 

This  assay  is  actually  a  modification  of 
the  German  method  previously  described. 
Its  advantage  is  that  no  prills  of  tin  (or, 
rather,  particles  of  bronze)  are  found  sus- 
pended in  the  slag.  All  the  metallic  oxides 
that  have  been  reduced  are  found  collected 
in  one  button.  It  is  claimed  that  more  tin 
is  recovered  by  this  method  than  by  the 
regular  German  method,  and  that  the  but- 
tons do  not  differ  more  than  from  0.4  to  0.5 
per  cent. 


2i)0 


XXX. 
Assay  of  Sulplmrets  in  Ores. 

IT  is  often  very  necessary  to  know  the 
quantity  of  sulphurets  contained  in  ores,  to 
be  able  to  arrange  accordingly  the  processes 
of  smelting  them. 

To  one  part  of  ore,  50  to  100  grains,  one 
part  of  powdered  glass  and  two  of  borax 
are  required. 

The  borax  is  first  mixed  with  the  ore, 
and  when  placed  in  the  Hessian  crucible, 
or  in  the  lead  and  copper  one,  fig.  4,  Plate 
II.,  both  are  covered  with  the  glass.  The 
crucible  is  then  exposed  to  a  bright  red-heat, 
as  with  copper  and  lead,  and  on  cooling  the 
button  is  broken  out,  which  may  contain  in 
the  shape  of  sulphurets,  copper,  lead,  iron, 


ASSAY   OF   SULPHURETS   IN   ORES.  261 

&c.,  according  as  these  exist  in  the  ore,  and 
it  may  then  be  examined  for  these  metals 
by  the  means  already  given  in  their  respec- 
tive assays. 

Volumetric  determination  of  sulphur  in 
ores  which  contain  either  sulphur  alone,  or 
also  sulphates.  Weil  gives  the  following 
method  :  Place  1  to  2  grammes  of  the  finely 
powdered  ore  in  a  flask  provided  with  a 
cork,  through  which  passes  a  bent  tube. 
The  outside  end  of  this  tube  dips  into  an 
ammoniacal  solution  of  copper  of  known 
strength.  A  few  small  pieces  of  granulated 
zinc  are  placed  in  the  flask,  and  75  cubic 
centimeters  of  hydrochloric  acid  poured 
over  its  contents;  quickly  close  the  flask 
and  heat.  The  sulphuretted  hydrogen  de- 
veloped precipitates  an  equivalent  portion 
of  copper,  and,  when  precipitation  ceases, 
the  sulphide  is  allowed  to  settle,  is  filtered 
and  washed.  The  object  of  adding  the 
zinc  is  to  dilute  the  sulphuretted  hydrogen 
with  hydrogen,  and  to  carry  off  the  last 


262  THE  ASSAYER'S  GUIDE. 

traces  of  it  which  may  remain  in  the  flask 
and  glass  tube.  The  amount  of  filtrate 
from  the  precipitated  copper  sulphide  is 
carefully  measured,  and  10  to  20  cubic 
centimeters  of  it  saturated  with  from  25  to 
50  cubic  centimeters  of  hydrochloric  acid. 
Heat  to  boiling,  and  when  boiling  titrate 
with  a  standardized  solution  of  stannous 
chloride.  This  quantity  multiplied  by 
0.50393  gives  the  content  of  sulphur 
sought.  The  zinc  added  facilitates  the  ac- 
tion of  the  acid  upon  the  ore,  and  if  any 
galena  is  present,  it  is  also  more  readily 
decomposed ;  the  chloride  of  lead  formed 
being  reduced  to  metallic  lead  by  the  zinc. 
Examination  of  sulphur  in  metallic  lead. 
Treat  20  to  30  grammes  of  very  fine  chips 
of  the  lead  with  a  considerable  excess  of 
concentrated  hydrochloric  acid ;  sulphur 
will  be  set  free  as  sulphuretted  hydrogen. 
Pass  this  sulphuretted  hydrogen,  by  means 
of  an  aspirator,  into  bromine  water,  in 
which  it  is  decomposed,  sulphuric  acid  be- 


ASSAY  OF  SULPHURETS  IN   ORES.          263 

ing  formed.  Determine  the  sulphur  in  the 
latter  with  barium  chloride  as  usual.  The 
solution  of  the  lead  is  aided  by  gentle  heat. 
A  large  excess  of  hydrochloric  acid  prevents 
the  separation  of  lead  ehloride. 

Determination  of  sulphur  in  pyrites.  To 
1  gramme  of  the  finely  powdered  ore  in  a 
porcelain  dish  or  casserole  add  a  small 
amount  of  potassium  chlorate,  cover  the 
dish  with  a  watch  glass,  add  50  cubic  cen- 
timeters concentrated  nitric  acid,  and  heat 
to  boiling,  adding  a  little  chlorate  from  time 
to  time.  When  perfectly  oxidized,  remove 
the  watch  glass  (and  it  should  be  rinsed 
into  the  dish),  and  evaporate  to  a  small 
bulk  on  a  water  bath.  Add  a  little  strong 
hydrochloric  acid,  and  evaporate  to  dryness, 
moisten  with  the  same  acid,  add  water,  and 
filter  from  silica  and  the  gangue.  To  the 
filtrate  add  1  gramme  tartaric  acid,  heat, 
add  hot  solution  of  barium  chloride,  drop 
by  drop,  boil,  let  settle,  filter  and  wash  well 
with  hot  water. 


264  THE  ASSAYER'S   GUIDE. 

Weigh  a  clean  porcelain  or  platinum  cru- 
cible, add  the  filter  and  precipitate,  burn  to 
ashes,  cool,  and  weigh  as  baric  sulphate. 
After  deducting  weights  of  crucible  and 
filter  ash,  multiply  the  remainder  by  0.1374, 
and  the  product  by  100  for  percentage  of 
sulphur. 

Bodewig's  method  of  determining  sulphur 
in  pyrites.  One-half  gramme  of  pyrites  is 
treated  in  a  glass-stoppered  vessel  of  about 
100  cubic  centimeters'  capacity,  with  30 
cubic  centimeters  of  water  and  4  c.  c.  of 
bromine.  The  stopper  is  quickly  inserted, 
and  the  vessel  shaken  for  5  minutes.  When 
oxidation  is  ended,  which  is  known  by  the 
disappearance  of  all  pulverulent  sulphur 
adhering  to  the  sides  of  the  glass,  the  solu- 
tion is  emptied  into  a  casserole,  and  most 
of  the  bromine  allowed  to  evaporate  in  the 
cold.  The  solution  is  almost  neutralized 
with  ammonia,  then  poured  into  an  excess 
of  hot  ammonia  contained  in  a  platinum 
dish,  and  digested  from  10  to  15  minutes  at 


ASSAY  OF  SULPHURETS  IN  ORES.          265 

a  gentle  heat.  The  sulphuric  acid  is  de- 
termined in  the  filtrate  from  this  in  the 
usual  manner.  The  entire  amount  of  bro- 
mine employed  must  not  be  added  all  at 
once,  as  otherwise  there  may  be  some  loss 
of  sulphur  in  the  form  of  sulphuretted  hy- 
drogen. Some  iron  volatilizes  as  a  bromide 
with  the  excess  of  bromine ;  hence  it  can- 
not be  determined  in  the  precipitate  made 
by  the  ammonia. 


266 


XXXI. 

Mode  of  testing  the   Calorific  Power  of  Coal 
and  other  Fuels.* 

IT  must  not  be  supposed  that  the  amount 
of  heat  which  a  fuel  is  capable  of  producing 
is  entirely  dependent  on  its  chemical  com- 
position. 

Different  means  have  been  adopted  to 
determine  the  efficacy  of  coal  as  a  fuel. 
Thus,  Despretz  has  made  experiments  of 
this  kind  by  discovering  the  amount  of 
water  which  a  certain  quantity  of  coal  will 
elevate  in  temperature  one  degree  of  the 
centigrade  thermometer.  The  varying  tem- 
perature of  the  water,  however,  must  ever 
prevent  an  accurate  result.  Kumford  has 
proposed  to  determine  the  same  by  the 

*  Rarsten's  Eiseuhiittenkunde,  vol.  ii.,  p.  219,  §  476. 


CALORIFIC   POWER   OF   COAL.  267 

direct  use  of  a  thermometer  in  a  closed 
vessel.  Berthier  has,  however,  proposed 
one  that  seems  equally  simple,  and  service- 
able for  all  practical  purposes. 

According  to  his  proposition,  one  gramme 
of  the  coal  (or  other  fuel;  for  it  is  applica- 
ble to  all)  should  be  thoroughly  pulverized. 
All  coals  are  readily  reduced  to  such  a 
state.  Wood  should  be  used  as  shavings,  or 
rasped.  The  powdered  substance  is  then 
mixed  with  some  litharge,  but  more  than 
it  is  capable  of  reducing, — not  less  than 
twenty  times  its  own  weight  nor  more  than 
forty.  The  quality  of  the  fuel  will  enable 
the  assay er,  after  a  little  practice,  to  deter- 
mine d,  priori  with  considerable  accuracy 
what  will  be  the  requisite  quantity.  The 
mixture  is  placed  in  a  clay  crucible  (Plate 
II.,  fig.  4  or  5)  and  carefully  covered  with 
about  twenty  to  thirty  grammes  of  litharge. 
The  crucible  must  not  be  filled  over  one- 
half  This  is  then  placed  in  a  heated  muffle 
and  covered.  The  heat  should  not  be  too 


268  THE  ASSAYER'S  GUIDE. 

severe  and  rapid.  The  contents  will  boil 
up.  When  the  melting  has  thoroughly 
taken  place,  strong  heat  should  be  applied 
for  ten  minutes,  so  that  the  button  may 
collect.  The  crucible  is  then  taken  out  and 
cooled  slowly,  then  broken,  and  the  button 
extracted  and  weighed. 

This  process  rests  upon  the  fact  that  the 
carbon  will  reduce  the  litharge;  and  having, 
therefore,  assumed  one  number  for  the 
amount  of  litharge  reduced,  from  which 
to  calculate  our  experiments,  it  will  be  easy 
to  compare  the  different  varieties  of  fuel. 
When  many  experiments  of  this  kind  are 
made,  the  assayer  will  do  well  to  establish 
a  certain  number  as  the  basis.  This  will 
vary  according  to  the  general  character  of 
his  coals.  This  number  it  will  be  well  to 
assume  as  low  as  possible,  to  avoid  the  in- 
convenience of  fractions.  He  would  there- 
fore adopt  a  very  inferior  variety  of  coal 
as  the  one  with  which  to  compare  the 
others  in  the  following  manner,  though 


CALORIFIC   POWER  OF   COAL.  269 

be  it  remembered  I  am  not  now  giving 
results  of  assays,  but  only  imaginary 
examples. 

1  part  bone-coal    reduced  10.00  parts  by  weight  of  litharge 
"    rough  bituminous"  12.50      "  "  '< 

"    good  bituminous  "  20.00     "  «  ' 

"    anthracite  "  26.00     "  «•  • 


II 


Sis 
fll 


.270 


inclusive, 
les  in  the 
gland. 


two  fi  clays,  1  to  3 
sed  chiefly  for  crucib 
facture  of  steel  in  En 


rst 
iefl 


T86    |    5*66    |   0'66    |    9'66 


i'OOI 


O'OOl 


1 


II 


From  Stourbridge, 
England,  by  Ber- 
thier- 


Sr 


OQ 


b 

"-.I 


ill 

|ii 

CO 


271 


Table  showing,  in  Degrees  of  the  Centigrade  and  Fah- 
renheit Thermometers,  the  Amount  of  Heat  necessary 
to  melt  various  Substances. 


Centigrade. 

Fahrenheit 

Platina.... 

2500 

4532 

1500-1600 

2732-3012 

Steel  

1300-1400 

2372-2552 

Cast  iron,  j 

irav 

1200 

2192 

Do. 

irhite  

1050 

1922 

Gold  

1100-1250 

2012-2282 

Silver  

1000 

1832 

900 

1652 

Antimony  . 

450 

842 

Zinc  

360 

680 

Lead  

330 

658 

Bismuth... 

260 

480 

Tin  

230 

446 

Alloys  of  Tin, 

Lead,  and 

Bismuth. 

(in  parts.) 

(in  parts.) 

(in  parts.) 

1 

3 

289 

554 

1 

1 

_ 

241 

464 

3 

„ 

1 

200 

892 

3 

1 

_ 

186 

865 

2 

_ 

1 

167.7 

333.5 

1 

_ 

1 

142.2 

283.8 

4 

1 

5 

188-9 

246.2     ! 

3 

2 

5 

100 

212 

3 

5 

8 

100 

212 

1 

1 

4 

94 

203 

109 

280 

Mercury 

-39 

38  2 

»e.^    i 

"2T1 


T<M*  of  Tray  Weights  used  with  Gold,  and  Silver,  and 
Platina. 

24  grains  (gr.)     make  1  pennyweight  (dwt.) 
20  pennyweights    —    1  ounce  (oz.) 
12  ounces  —    1  pound  (Ib.) 

Ib.       oz.        dwt.          gr. 
1  =  12  =  240  ==  5760 
1  =     20  =     480 
1  =       24 

The  value  of  gold  is  given  in  carats  fine,  24  c.  f.  being 
pure. 

One  pound  of  gold  24  carats  fine  contains  5760  grs.  of  pure 
gold,  as  gold  of  that  number  of  carats  fine  is  unalloyed. 

One  pound  of  gold  23  carats  fine  contains  5520  grs.,  and 
•o  on,  and  one  oz.  of  gold  20  c.  f.  has  400  grs. 
one  dwt.  of  gold  15  c.  f.  has    15  grs. 
These  are  given  as  examples  of  the  manner  in  which  the 
Amount  of  the  pure  metal  ought  to  be  calculated. 


Table  of  Avoirdupois  Weights  used  with  other  Metals. 

(Tun,)  (Hundredweight)  (Quarter)        (Pound)     (Ounce)  (Dram) 

T.  ewt  qr.  Ib.  oz.  dr. 

1      =      20      =      80     =     2240  =  35840  =  573440 

1      SB        4=112=    1792  =    28672 

1     =        28  =      448  =      7168 

1  =        16  =       266 

1  =         16 


Plate  I.— Part  I. 


Plate  I.— Part  II. 


Plate  Il.-Part  I. 


Plate  II.-Part  II. 


Plate  II.— Part  III. 


INDEX. 


Acid  solvent  agents,  58 
Acids  for  wet  assays,  62 
Agricola  and  his  writings,  19 
Air-excluding  fluxes,  61,  62 
Alkalies  and  carbonates,  caus- 
tic, 60 
caustic,  59 
Alloy  or  coin,  pulverizing  an, 

140 
silver,  calculation   of  the 

silver  in  a,  86,  87 
Alloys  containing  gold,  silver 

and    copper,    assay    of, 

141-148 

melting  points  of,  271 
silver  and    copper,  assay 

of,  138-140 

silver,    Gay-Lussac's    pro- 
cess for  assaying,  80-98 
Almerode    clay,    analysis    of, 

270 

Amalgamated  pan,  114 
Amalgamation,  assay  of  gold 

ore  by,  106,  107 
American  gold  ore,  charge  for, 

126,  127 

Ammonium  carbonate,  61 
Analyses,  gravimetric,  of  lead 

ores,  216-218 
Analysis,  gravimetric  or  calori- 

inetric,      re-ageuts      for 

assays  by,  62 
Anthracite,  54 
Antimony,  addition  of,  in  the 

assay  of  copper,  160 
Argol,  54 
Arsenic,    addition    of,    in    the 

assay  of  copper,  160 
treatment    of    quicksilver 

containing,  249,  250 
Assay,  bronze,  Winkler's,  258, 

259 

.   18 


Assay,  crucible,  for  gold,  124- 
130 

dry,  of  iron  ores,  execution 
of,  235-239 

dry,  of  tin  ores,  253-259 

electrolytic,  of  platinum, 
156,  157 

furnaces,  gas,  44-53 

modified  Swedish,  of  cop- 
per, 170-179 

of  copper  ores,  158-170 

of  gold  by  a  wet  process, 
136,  137 

of  gold  by  combined  dry 
and  wet  methods,  117- 
135 

of  gold  by  panning,  111- 
116 

of  gold  by  washing,  108- 
110 

of  gold  coins,  or  alloys 
containing  gdld,  silver 
and  copper,  141-148 

of  gold  ore  by  amalgama- 
tion, 106,  107 

of  gold  ores  by  heat,  101- 
105 

of  iron  ores  by  heat,  219- 
223 

of  lead  ores,  185-209 

of  lead  ores  by  a  wet  pro- 
cess, 213-215 

of  lead  ores  by  heat,  210- 
212 

of  native  silver  ores,  99, 
100 

of  platinum  ores,  152-157 

of  quicksilver  ores,  243- 
252 

of  silver  coins,  or  alloys  of 
silver  and  copper,  138- 
140 

(273) 


274 


INDEX. 


Assay  of  silver,  inaccuracies  in 

the,  74-76 
of  silver  ores  by  heat,  64- 

76 
of  sulphurets  in  ores,  260- 

265 
scorification,  for  gold,  119- 

124 
silver,  a  table  to  rectify  the 

loss  incurred  during  the, 

77-79 
silver,  Gay-Lussac's  tables 

for  the,  89-96 
silver,   preparation   of  the 

charge  in  the,  67,  68 
solution,    silver,    prepara- 
tion of  the,  81-86 
Swedish,  for  iron  ores,  227- 

242 

wet,  of  copper,  170-179 
Whittell's,  of  silver,  97,  98 
Assayer,  chef  d'ceuvre  of  an, 

72,73 
chemistry  the  guide  of  the, 

19,20 
Assay ers  and  smelters,  German, 

adage  current  among,  73 
English,  practice  of,  in  the 

assay  of  copper,  168, 169 
Assaying,  antiquity  of,  18,  19 
by  heat,   implements    and 

utensils     used     in     the 

course  of,  21-53 
definition  of,  17 
plant,  W.  L.  Brown's,  45- 

53 

re-agents,  used  in,  54-63 
Assays,  advantage   of  making 

several,  at  one  time,  68 
by   gravimetric   or    calori- 

metric  analysis,  re-agents 

for,  62 

dry,  re-agents  for,  54-62 
gold,     by     smelting    with 

lead,  119-124 
volumetric,   indicators  for, 

63 
volumetric,    re-agents    for, 

62,63 
wet,  acids  for,  62 


Assays,  wet,  bases  and  salts  for, 

62 

wet,  re-agents  for,  62,  63 
Auriferous  lead,  cupellatiou  of 

the,  130,  131 
Australia,  method  of  assaying 

gold  in,  116 


Balance,  the,  and  its  manage- 
ment, 32,  33 

Base  coins  of  the  various  coun- 
tries, 148 

Bases  and  salts  for  wet  assays, 
62 

Basic  solvent  agents,  59,  60 

Batea,  the,  111 

Battersea  furnace,  31 

Belgium,  lead  assay  in,  193- 
195 

Bellows  furnace,  211 

Berthier's  method  of  testing  the 
efficacy  of  coal,  267,  268 
preparatory  process  in  the 
assay  of  quicksilver,  248, 
249 

process  for  quicksilver  ore 
containing  arsenic,  249, 
250. 

process  for  the  determina- 
tion of  earthy  matter  in 
iron  ores,  229,  230 

Besanite  or  touchstone  test,  141, 
142 

Bicarbonate  of  soda,  59 

Bismuth  in  silver,  87 

Black  flux,  55,  159,  160 

preparation  of,  187, 188 
substitute  for,  55,  56 

Bleiberg,  in  Carinthia,  assay  of 
lead  ores  at,  216,  217 

Bodewig's  method  of  determin- 
ing sulphur  in  pyrites, 
263-265 

Borax-glass,  58 

Brecon's  portable  furnace,  31 

Bronze  assay,  Winkler's,  258, 
259 

Brown's,  W.  L.,  gas-assaying 
plant,  45-53 


INDEX. 


275 


Buttons,  pan    for  cooling  the, 
39,40 


Calcination-assay  for  lead  ores, 

200-203 

Calcium  carbonate,  59 
California,    assay  of  gold    by 

washing  in,  108 

Calorific    power    of    coal    and 
other  fuel,  mode  of  test- 
ing the,  266-269 
Calorimetric     or      gravimetric 
analysis,  re-agents  for  as- 
says by,  62 
Carbon, 60 

Carbonate,  ammonium,  61 
calcium,  59 
of  potash,  59 

Carbonates  and  alkalies,  caus- 
tic, 60 
Caustic  alkalies,  59 

and  carbonates,  60 
Charcoal  and  graphite,  61 

for  coating  crucibles,  38,  39 
wood,  54 

Chemistry,    inorganic    analyti- 
cal,      as      contra-distin- 
guished   from    assaying, 
17,  18 
the  guide  of  the  assayer, 

19,  20 
theoretical,     assaying     the 

foundation  of,  18 
Cinnabar,  composition  and  for- 
mula of,  243 
from    Japan,    analysis    of, 

243,  244 

Classen's  method  for  the  elec- 
trolytic deposition  of 
metals,  180,  181 
for  the  electrolytic  de- 
termination of  quick- 
silver, 252 
of  the  determination  of 

copper,  181-183 
Clay,  58 
Clays,  analyses  of,  for  crucibles, 

270 
Coal  and  other  fuel,  mode  of 


testing  the  calorific  power 
of,  266-269 
Coal,  standards  for  comparison 

in  testing,  268,  269 
Coin  or   alloy,   pulverizing   a, 

140 
Coins,    base,    of    the    various 

countries,  148 

gold,  of  the  various  coun- 
tries, 146 

of  various  countries,  mint- 
units  of,  145 

silver,  of  the  various  coun- 
tries, 147 
Coke,  powdered,  54 
Common  salt,  61 

cover  of,  188,  189 
deci normal  solution  of, 

81 

decrepitated,  61,  62 
normal  solution  of,  81 
Concentrating  fluxes,  61 
Copper    button,    signs    of    the 
purity  of  the,  167, 168 
to  remove  the  foreign 
metals  from  the,  163 
Classen's  method  of  the  de- 
termination of,  181-183 
correction  for  iron,  in  the 

assay  of,  175,  176 
crucible    for  the  assay  of, 

163,  164 
electrolytic    determination 

of,  180-184. 

Herpin's  method  of  assay- 
ing, by  electrolysis,  183, 
184 
modified  Swedish  assay  of, 

170-179 

ore,  roasting  of,  158,  159 
ores,  assay  of,  158-169 

English  method  for  the 

assay  of,  165-169 
German  and  Hungarian 
method   of  assaying, 
158-164 
oxide,  61 
precipitation  of,  with  iron, 

172-177 
of,  with  zinc,  177-179 


276 


INDEX. 


Copper,       pure       precipitated,  j  Dry  assay  of  tin  ores,  253-259 
characteristics  of,   176 


wet  assay  of,  170-179 
Cornwall,  assay  of  copper  ores 

in,  165-169 

Covering  agents,  61,  62 
Crucible  assay  for  gold,  124-130 
clay,  lead   assay  in  a,  with 
black  flux  and  iron,  195- 
198 
for  the  Ussay  of  copper,  163, 

164 

Hessian,  36,  37 
iron,  lead  assay  in  an,  with 

black  flux,  192-195 
Crucibles,  36-39 

analyses  of  clay  for,  270 
basqued,  preparation  of,  235, 
236 


Electrolysis.    TTerpiu's    method 
of   assjiving    copper    by, 
183,  184. 
Electrolytic  assay  of  platinum, 

156,  157 
determination     of    copper, 

180-184 

of  quicksilver,  250-252 
England,  assay  of  iron  in,  239- 

242 

proportions   of   the   charge 

in  lead  assays  in,  194,  195 

English    assayers,   practice    of, 

in   the   assay   of   copper. 

168,  169 

method    for    the    assay    of 
165-169 


clay     Upper  Harz    potash    Erkei.,g  \^le  of  'the  quantjties 
lead  assay  in    H-8,  199  of   ]ead   to   be  4added    in 

for  the  assay  of  silver -71  the  of  si]ver  coi 

paste  for  coating,  38,  39  139 

Cupellation,  64-76  Escosura's  process  of  the  elec- 

of  the  auriferous  lead,  130, ,  trolytic   determination  of 


131 
Cupels  or  cups,  34,  35 

recipe   for   the  preparation 

of,  35 

Cups  or  cupels,  34,  35 
Cyanide  of  potassium,  56,  60 

D'Arcet's  table  for  the  quanti- 
ties of   lead  to  be  added 
in  the  assay  of  gold  coins, 
143,  144 
Decomposing    and    volatilizing 

fluxes,  61 

Despretz's  experiments  to  deter- 
mine the  efficacy  of  coal, 
266 
Desulphurizing  or  precipitating 

agents,  60 
Dross  or  sweepings,  fluxes  for, 

129,  130 
of    gold,    melting    of, 

125-127 

Dry  and  wet  methods,  com- 
bined, assay  of  gold  by, 
117-135 


quicksilver,  250-252 

Ferrocyanide  of  potassium,  56, 

60 
Fletcher's  direct-draft  crucible 

furnace,  45 
Fluor-spar,  59,  60 
Flux,  black,  55,  159,  160 

preparation  of,  187,  188 
substitute  for,  55,  56 
gray,  55,  188 
quantities  of,   in  the  assay 

of  iron  ores,  230 
white,  55,  166,  188 
Flaxes,  air-excluding,  61,  62 
concentrating,  61 
decomposing  and  volatiliz- 
ing, 61 
for  dross  or  sweepings,  129, 

130 

for  iron  ores   or  metallur- 
gical products,  233-235 
lead  assays  with,  191-199 
scale  for  weighing,  33 


INDEX. 


277 


Fluxes    used  in  the  assay  of 

quicksilver,  245,  246 
France,  lead  assay  in,  193-195 
regulation  of  the  mint  as- 
says in,  80 
Freiberg,  lead  assay  at,  195 

from  the   smelting 

works  at,  66 
proportions  of   the   charge 

in  lead  assays  at,  195 
Fritzche's  recipe  for  the  prepa- 
ration of  cupels,  35 
Fuchs's  process  for    iron    ores 

and  iron.  224-226 
Fuel,  mode  of  testing  the  cal- 
orific power  of,  266-269 
Furnace,  Battersea,  31 
bellows,  211 
Brocon's  portable,  31 
Fletcher's  direct-draft  cru- 
cible, 45       . 

for  testing  iron  ores,  27-30 
muffle,  21-27 
Furnaces,  gas,  44-53 
portable,  30,  31 


Gas  assay-furnaces,  44-53 

assaying     plant,     W.      L. 

Brown's,  45-53 

Gay-Lussac's  apparatus,  82,  83 
process  for  assaying  sil- 
ver alloys,  80-98 
tables  for  silver  assay, 

89-96 

German  and  Hungarian  method 
of  assaying  copper  ores, 
158-164 
method  of  assaying  tin,  255, 

256 
smelters  and  assayers,  adage 

current  among,  73 
Germany,  lead  assay  in,  193-195 
regulation  of  the  mint  as- 
says in,  80 
Glass,  58" 

borax,  58 
Gold,  61 

assay,  addition  of  silver  in 
the,  103,  104 


Gold,  assay  of,  by  a  wet  process, 

136,  137 

of,  by  combined  dry 
and  wet  methods, 
117-135 

of,  by  panning,  111-116 

of,  by  washing,  108-110 

assays    by    smelting    with 

lead,  119-124 
besanite  or  touchstone  test 

for,  141,  142 

button,  behavior  of  the,  to- 
wards nitric  acid, 132- 
134 

color  of  the,  132 
coins,  assay  of,  141-148 

of  the  various  coun- 
tries, 146 

quantities  of  lead  to  be 
.     added  in  the  assay  of, 

143,  144 

crucible  assay  for,  124-130 
dross  or  sweepings,  fluxes 
for,  129,  130 

melting  of,  125 

-127 

free,  separation  of,  from  sul- 
phides, 114,  115 
obtained  by  panning,  exam- 
ple of  calculating  the,  114 
ore,  American,   charge  for, 

126,  127 

assay  of,  by  amalgama- 
tion, 106,  107 
sampling  of,  117,  118 
ores,  assay  of,  by  heat,  101- 

105 

earthy    or    containing 
ferric  oxide,  melting 
of,  125-127 
sulphuretted  melting  of, 

127-130 

parting    the,   from  the  sil- 
ver, 131-135 
scorification  assay  for,  119- 

124 

smelting  of,  with  lead,  117 
specific  gravity  of,  149 
specks,  recognition  of,  134, 
135 


278 


INDEX. 


Gold,  test-acid  for,  composition 

of,  141,  142 

to  find  the  proportion  of,  in 
a  mixture    of  gold   and 
quartz,  149-151 
troy  weights  for,  272 
Graphite,  54 

and  charcoal,  61 

from   Passau,  analysis  of, 

270 
Gravimetric   analyses    of  lead 

ores,  216-218 

or  calorimetric  analysis,  re- 
agents for  assays  by,  62 
Gray  flux,  55,  188 

Harz  mountains,  apparatus  for 
assaying  iron  used  on  the, 
220,  221 

upper,  potash  lead  assay  in 
clay  crucibles,  198,  199 

Heat,  the  amount  of,  necessary 
to  melt  various  sub- 
stances, 271 

Herpin's  method  of  assaying 
copper  by  electrolysis, 
183,  184 

Hessian  crucible,  36,  37 

Hungarian  and  German  method 
of  assaying  copper  ores, 
158-164 

Implements  and  utensils  used 
in  the  course  of  assays 
by  heat,  21-53 

Indicators    for  volumetric    as- 
says, 63 
Iridium,    separation    of,    from 

platinum,  157 

Iron  and  iron  ores,  Fuchs's  pro- 
cess for,  224-226 
assay  of,  in  England,  239- 

242 
buttons,  characteristics  of, 

237,  238 

chemically  pure,  prepara- 
tion of,  222 

correction  for,  in  the  cop- 
per assay,  175,  176 


Iron  dishes,  lead  assay  in,  189, 

190 

ores  and  iron,  Fuchs's  pro- 
cess for,  224-226 
assay  of,  by  heat,  219- 

223 

character  of  the  slag, 

in  assaying,  231-233 

determination  of 

earthy  matter  in,  229, 

230 

furnace  for  testing,  27- 

30 
preliminary  assay  of, 

229,  230 
quantities  of  flux   in 

the  assay  of,  230 
siliceous    and   argilla- 
ceous flux  for,  231 
Swedish     assay      for, 

227-242 

oxide  of,  free  from  foreign 
metals,    preparation    of, 
222,  223 
precipitation     of     copper 

with,  172-177 

proportions    of    ore    and 
fluxes  in   the   assay  of, 
239,  240      . 
pyrites,  61 

reducing  agents  in  the  as- 
say of,  240 
results  of  the  assay  of,  241, 

242 

ores  or  metallurgical  prod- 
ucts, fluxes  for,  233-235 

Japan,    analysis    of    cinnabar 
from,  243,  244 


Kaolin,  58 

Karsten's  method  of  preparing 
chemically  pure  iron,  222 

Klaproth,  analysis  of  cinnabar 
from  Japan  by,  243,  244 

Kleinschmidt's  method  of  as- 
saying gold  by  panning, 
115,  116 

Kupfer  Garscherbe,  36 


INDEX. 


279 


Lead,  61 

addition  of,  in  silver  as- 
says. 65,  66 

of,  in  the  assay  of  cop- 
per, 160 

assay  by  melting  with  re- 
ducing agents,  206- 
208 

in  a  clay  crucible  with 
black  flux  and  iron, 
195-198 

in    an    iron     crucible 
with  black  flux,  192- 
195 
in  iron  crucibles,  190, 

191 
in     iron    dishes,    189, 

190 

assays  by  melting  with  re- 
ducing   agents    and 
iron,  208,  209 
with  fluxes,  191-199 
without  fluxes  in  iron 

vessels,  189-191 
auriferous,   cupellation  of 

the,  130,  131 
from  the  smelting  works  at 

Freiberg,  66 
gold    assays    by  smelting 

with,  119-124 
metallic,    examination    of 

sulphur  in,  262,  263 
ores,  assay  of,  185-209 

by  heat,  210- 

212 

by  a  wet  pro- 
cess^ 13-2 15 
with      sulphuric 
acid  for,  203-205 
calcination   assay  for, 

200-203 
gravimetric     analyses 

of,  216-218 

oxidized,  and  smelting 
products,  assays  for, 
206-209 

sulphuretted  with  few 
or  no  foreign  sul- 
phides, methods  of 
assaying,  186-199 


Lead  ores    sulphuretted    with 
many    foreign    sul- 
phides,   methods  of 
assaying,  199-205 
oxide,  60 

preparation  of  pure,  66,  67 

quantities  to  be  added  in 

the  assay  of  gold  coins, 

143,  144 

slags,  melting  of,  at  Mech- 

ernich,  208 

smelting  of  gold  with,  117 
sulphate  of,  composition  of, 

214,  215 
white,  57,  60 
yeklow,  oxide  of,  57,  58 
Leval's  assay  of  tin  with  potas- 
sium cyanide,  256-258 
Litharge,  57,  58 

entirely  free  from  silver,  to 

prepare,  57,  58 

Lowe's  method  of  assaying  na- 
tive silver  ores,  99,  100 


Mechernich,   melting    of    k-ad 

slags  at,  208 
Mercury  in  silver,  87 
melting  point  of,  271 
purification  of,  106 
Metallurgical  products  or  iron 

ores,  fluxes  for,  233-235 
Metals,    Classen's    method   of 
the   electrolytic    deposi- 
tion of,  180,  181 
for  precipitation,  62 
melting  points  of,  271 
tableof  avoirdupois  weights 

for,  272 

Microcosmic  salt,  58 
Minium,  60 

Mint  assays,  regulation  of,  in 
Germany  and  France,  SO 
units  of  the  coins  of    va- 
rious countries,  145 
Mitchell's  assay  of  tin,  256 
Monitor,  the,  48,  49 
Mortar  and  pestle,  64,  65 
Muffle  furnace,  21-27 
the,  21,  22 


280 


INDEX. 


Nitric  acid,  behavior  of  the  gold 
button  towards,  132- 
134 

quartation  with,  117 
solution  of  silver  chlo- 
ride in,  87,  88 

Normal  solutions,  preparation 
of  the,  88,  89 

Ore,    American    gold,    charge 

for,  126, 127 

gold,  assay  of,  by  amalga- 
mation, 106,  107 
sampling  of,  117,  118 
Ores,  assay  of  sulphurets  in, 

260-265 

copper,  assay  of,  158-169 
gold,  assay    of,    by   heat, 

101-105 

earthy    or    containing 
ferric  oxide,  melting 
of,  125-127 
sulphuretted,    melting 

of,  127-130 
iron,    assay  of,    by    heat, 

219-223 
furnace  for  testing,  27- 

30 
Swedish  assay  for,  227- 

242 
lead,  assay  of,  185-209 

by  heat,  210-212 
native  silver,  assay  of,  99, 

100 

platinum,  assay  of,  152-157 
quicksilver,  assay  of,  243- 

252 
silver,  assay  of,   by  heat, 

64-76 

tin,  dry  assay  of,  253-259 
volumetric    determination 
of  sulphur  and  sulphates 

in,  261,  262 
Oxide,  copper,  6i 

lead,  60 
Oxidizing  agents,  57,  58 

Pan,  amalgamated,  114 
Panning,    assay    of    gold    by, 
111-116 


Panning,  example  of  calculat- 
ing the  gold  obtained 
by,  114 

Passau  clay,  analysis  of,  270 
Percy,  charges  in  making  lead 
assays,  recommended  by, 
208  " 

formation  of  a  slag  recom- 
mended by,  233 
Peru,  quicksilver  ore  from,  249, 

250 

Pestle  and  mortar,  64,  65 
Phosphorus,  salt  of,  58 
Pibram,  lead  assay  at,  196-198 
Platinum,  electrolytic  assay  of, 

156,  157 

ores,  assay  of,  152-157 
separation  of  iridium  from, 

157 

troy  weights  for,  272 
Plumbic  monoxide,  57,  58 
Potash,  carbonate  of,  59 

crude  bitartrate  of,  54 
Potassium  carbonate,  59 
cyanide,  56,  60 

Leval's  assay  of  tin, 

with,  256-258 
ferrocyanide,  56,  60. 
Pouring  plate,  39,  40 
Precipitating    or   desulphuri& 

ing  agents,  60 
Precipitation,  metals  for,  62 
Pyrites,  determination  of  sul* 

phur  in,  263-265 
iron,  61 

Quartation,  103 

with  nitric  acid,  117 
Quartz  and  gold,  to  find   the 
proportion  of  gold  in  a 
mixture  of,  149-151 
specific  gravity  of,  149 
Quicksilver,  Berthier's  prepar- 
atory process  in  the  as- 
say of,  248,  249 
containing    arsenic,  treat- 
ment of,  249,  250 
distillation  of,  244,  245 
electrolytic    determination 
of,  250-252 


INDEX. 


281 


Quicksilver,  fluxes  used  in  the 

assay  of,  245,  246 
ores,  assay  of,  243-252 

Ramnaelsberg  lead  ores,  assay 

for,  200-203 

Re-agents  for  assays  by  gravi- 
metric or  calori- 
metric  analysis, 
62 

dry  assays,  54-62 
volumetric  assays, 

62,63 

wet  assays,  62,  63 
used  in  assaying,  54-63 
Reducing  agents,  54-57 

list   of    the    reducing 

powers  of,  56,  57 
Roessler's  method  of  fixing  the 

lead  sponge,  218 
Rumford's   method    of    testing 
the  efficacy  of  coal,  266, 
267 

Salt,  common,  61 

cover  of,  188,  189 
decinormal  solution  of, 

81 

decrepitated,  61,  62 
normal  solution  of,  81 
microcosmic,  58 
of  phosphorus,  58 
solution,  decimal  table  for, 

91-93 

Saltpetre,  57,  60 
Salts  and  bases  for  wet  assays, 

62 

Scale  for  weighing  larger  quan- 
tities, 33 
Scorification    assay    for    gold, 

119-124 
mould,  39,  40 
Scorifier,  39,  40 
Sieves  and  sifting,  43,  44 
Sitting  and  sieves,  43,  44 
Silberblick,  71,  72 
Silica,  58 
Silver,  61 

addition  of,  in  the  gold  as- 
say, 103,  104 


Silver  alloy,  calculation  of  the 

silver  in  a,  86,  87 
alloys,   Gay-Lussac's   pro- 
cess for  assaying,  80-98 
and    copper,   assay  of  al- 
loys of,  138-140 
Sire's  apparatus,  83-85 
Silver  assay,  a  table  to  rectify 
the     loss     incurred 
during  the,  77-79 
Gay-Lussac's  tables  for 

the,  89-96 

preparation      of      the 

charge  in  the,  67,  68 

solution,     preparation 

of  the,  81-86 
assays,  addition  of  lead  in, 

65,66 

bismuth  in,  87 
buttons,  manipulation  of, 

73,74 

separation  of  the,  71 
chloride,    solution    of,    in 

nitric  acid,  87,  88 
coins,  assay  of,  138-140 
of   the   various  coun- 
tries, 147 

quantities  of  lead  to 
be  added  in  the  as- 
say of,  139 

crucibles  for  the  assay  of,  71 
deciuormal  solution  of,  81 
gleam,  71,  72 
inaccuracies  in   the  assay 

of,  74-76 
mercury  in,  87 
occurrence  of,  64 
ores,  assay  of  by  heat,  64- 

76 
native,    assay    of,  99, 

100 
parting  the  gold  from  the, 

131-135 
pure,  preparation  of,  102, 

103 
solution,  decinormal,  table 

for,  94-96 
tin  in,  87 

to  prepare  litharge  entirely 
free  from,  57,  58 


282 


INDEX. 


Silver,  troy  weights  for,  272 
Whittell's    assay    of,    97, 

98 

Slag,  appearance  of,  in  the  as- 
say of  copper,  162 
character  of  the,  in  assay- 
ing iron  ores,  231-233 
formation    of    a,     recom- 
mended by  Percy,  233 
in  silver  assays,  69,  70 
refined,  62 

Smelters  and  assayers,  Ger- 
man, adage  current 
among,  73 

Smelting  products  and  oxidized 
lead  ores,  assays  for, 
206-209 

Soda,  bicarbonate  of,  59 
Sodium-ammonium    hydrogen 

phosphate,  58 
carbonate,  59 
Solution,    decimal    salt,  table 

for,  91-93 
decinormal    silver,    table 

for,  94-96 
Solutions,  normal,  preparation 

of,  88,  89 

Solvent  agents,  58-60 
Stammingtou  clay,  analysis  of, 

270 
Storer's  assay  of  lead  ores,  217, 

218 
Stourbridge  clay,  analysis  of, 

270 
Sulphate  of  lead,  composition 

of,  214,  215 

Sulphates   and   sulphur,   volu- 
metric determination  of, 
in  ores,  261,  262 
Sulphides,   separation    of   free 

gold  from,  114,  115 
Sulphur,  61 

and  sulphates,  volumetric 
determination   of,  in  ores, 

261,  262 

determination    of,    in    py- 
rites, 263-265 

examination  of,  in  metal- 
lic lead,  262,  263 
melting  point  of,  271 


Sulphur,  recognition  of,  in  ircn, 

238,  293 
Sulphurets  in    ores,   assay   of, 

260-265 

Sulphuretted   gold   ores,  melt- 
ing of,  127-130 
lead  ores  with'  few  or  no 
foreign    sul- 
phides,   me- 
thods of  as- 
saying, 186- 
199 

many  earthy 
constituents, 
methods  of 
assayingfor, 
205,  206 
many  foreign 
s  u  1  ])  hides, 
methods  of 
assaying, 
199-205 
Sulphuric  acid,  assay  of  lead 

ores  with,  203-205 
Sulphurizing  agents,  61 
Swedish   assay   for    iron   ores, 

227-242 

of  copper,  170-179 
Sweepings  or  dross,  fluxes  for. 

129,  130 

of   gold,    melting 
of,  125-127 


Table  for  decimal  salt  solution, 
91-93 

decinormal   silver    so- 
lution, 94-96 
of  analyses  of  different 
clays  used  for  cru- 
cibles, 270 

avoirdupois  weights 
for  metals,  272 

base  coins  of  the  va- 
rious countries,  148 

gold  coins  of  the  va- 
rious countries,  146 

mint-units  of  the  coins 
of  various  countries, 
145 


INDEX. 


283 


Table  of  silver  coins  of  the  va- 
rious countries,  147 
the  quantities  of  lead 
to  be  added  in  the 
assay  of  gold  coins, 
143,  144 

the  quantities  of  lead 
to  be  added  in  the 
assay  of  silver  coins, 
139 

troy  weights  used  with 
gold,  and  silver,  and 
platinum,  272 
showing    the    amount    of 
heat  necessary   to    melt 
various  substances,  271 
to  rectify  the  loss  incurred 
during  the  silver  assay, 
77-79 
Test  acid,  composition  of,  141, 

142 
Tin,  difficulties  in  the  assay  of, 

253,  254 

German    method  of  assay- 
ing, 255,  256 
in  silver,  87 

Leval's  assay  of,  with   po- 
tassium cyanide,  256-258 
Mitchell's  assay  of,  256 
ores,    dry   assay   of,    253- 

259 

Tongs,  40-42 

Touchstone  or  besanite  test, 
141,  142 

United  States,  assay  of  gold  by 

panning  in  the,  111 

occurrence  of  platinum 

in  the,  152 

Utensils  and  implements  used 
in  the  course  of  assaying 
by  heat,  21-53 


Volatilizing  and    decomposing 

fluxes,  61 
Volumetric    assays,   indicators 

for,  63 

re-agents  for,  62,  63 
determination   of  sulphur 
and    sulphates    in   ores, 
261,  262 

Wales,   South,   lead   assay   in, 

190,  191 
Washing,    assay   of    gold   by, 

108-110 

Weights,  avoirdupois,  for  met- 
als, 272 
troy,   for  gold,  silver  and 

platinum,  272 

Weil's  method  of  determining 
sulphur  and  sulphates 
in  ores,  261,  262 
Wet  and  dry  methods  com- 
bined, assay  of  gold  by, 
117-135 

assay  of  copper,  170-179 
assays,  acids  for,  62 

bases  and  salts  for,  62 
re-agents  for,  62,  63 
process,   assay    of  gold  by 

a,  136,  137 
White  flux,  55,  166,  188 

lead,  60 
Whittell's  assay  of  silver,  97, 

98 
Winkler's  bronze    assay,   258, 

259 
Wood  charcoal,  54 

Yellow  oxide  of  lead,  57,  58 

Zinc,   precipitation   of  copper 
with,  177-179 


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Its  History,  Variety,  Culture,  Manufacture,  Commerce,  and  Various 
Modes  of  Use.      By  E.    R.    BILLINGS.      Illustrated  by  nearly  200 
engravings.     8vo.      .          .          .          .          .          .          .          .      $3  oo 

BIRD. — The  American  Practical  Dyers'  Companion: 

Comprising  a  Description  of  the  Principal  Dye- Stuffs  and  Chemicals 
used  in  Dyeing,  their  Natures  and  Uses  ;  Mordants  and  How  Made  ; 
with  the  best  American,  English,  French  and  German  processes  f»r 
Bleaching  and  Dyeing  Silk,  Wool,  Cotton,  Linen,  Flannel,  Felt. 
Dress  Goods,  Mixed  and  Hosiery  Yarns,  Feathers,  Grass,  Felt,  Fur, 
Wool,  and  Straw  Hats,  Jute  Yarn,  Vegetable  Ivory,  Mats,  Skins, 
Furs,  Leather,  etc.,  etc.  By  Wood  Aniline,  and  other  Processes, 
together  with  Remarks  on  Finishing  Agents,  and  instructions  in  the 
Finishing  of  Fabrics,  Substitutes  for  Indigo,  Water-Proofing  of 
Materials,  Tests  and  Purification  of  Water,  Manufacture  of  Aniline 
and  other  New  Dye  Wares,  Harmonizing  Colors,  etc.,  etc.  ;  embrac- 
ing in  all  over  800  Receipts  for  Colors  and  Shades,  accompanied  by 
170  Dyed  Samples  of  Raw  Materials  and  Fabrics.  By  F.  J.  BIRD, 
Practical  Dyer,  Author  of  "  The  Dyers'  Hand-Book."  8vo.  $4.00 


HENRY   CAREY   BAIRD  &  CO.'S  CATALOGUE 


bLINN.— A  Practical  Workshop  Companion  for  Tin,  Sheet- 

Iron,  and  Copper-plate  Workers; 

Containing  Rules  Tor  describing  various  kinds  of  Patterns  used  by 
Tin,  Sheet-Iron  and  Copper- plate  Workers;  Practical  Geometry; 
Mensuration  of  Surfaces  and  Solids ;  Tables  of  the  Weights  of 
Metals,  Lead-pipe,  etc. ;  Tables  of  Areas  and  Circumference* 
of  Circles;  Japan,  Varnishes,  Lackers.  Cements,  Compositions,  etc.. 
etc.  By  LEROY  J.  BLINN,  Master  Mechanic.  With  One  Hundred 
and  Seventy  Illustrations.  I2mo $2.50 

BOOTH.— Marble  Worker's  Manual: 

Containing  Practical  Information  respecting  Marbles  in  general,  theii 
Cutting,  Working  and  Polishing ;  Veneering  of  Marble  ;  Mosaics  : 
Composition  and  Use  of  Artificial  Marble,  Stuccos,  Cements,  Receipts. 
Secrets,  etc.,  etc.  Translated  from  the  French  by  M.  L.  BOOTH. 
With  an  Appendix  concerning  American  Marbles.  I2mo.,  cloth  $1.50 

BRANNT.— A   Practical   Treatise  on  Animal  and  Vegetable 
Fats  and  Oils : 

Comprising  both  Fixed  and  Volatile  Oils,  their  Physical  and  Chem- 
ical Properties  and   Uses,  the    Manner  of    Extracting   and    Refining 
them,  and  Practical  Rules  lor  Testing  them  ;  as  well  as  the  Manufac- 
ture of  Artificial  Butter  and  Lubricants,  etc.,  with  lists  of  Ameiica 
Patents  relating  to  the  Extraction,  Rendering,  Refining,  Decomposing 
and  Bleaching  of  Fats  and  Oils.     By  WILLIAM  T.  BKANNT,  Edit< 
of  the  "  Techno-Chemical  Receipt  Book."      Second  Edition,  Revise 
and  in  a  great  part  Rewritten.     Illustrated  by  302  Engravings.     1 

Two  Volumes.     1304  pp.     8vo #10.00 

BRANNT.— A  Practical  Treatise  on  the  Manufacture  of  Soj-p 

and  Candles : 

Based  upon  the  most  Recent  Experiences  in  the  Practice  and  Scieiu  <.  ; 
comprising  the  Chemistry,  Raw   Materials,  Machines,  and  Utensiib 
and  Various  Processes  of  Manufacture,  including  a  great  variety  of 
formulas.     Edited   chiefly  from  the   German  of   Dr    C.   Deite,  A 
Kn^elhardt,  Dr.  C.  Schaedler  and  others;   with  additions  and   list- 
of  American  Patents  relating  to  these  subitcts.     By  WM.  T.  BRANM 
Illustrated  by  163  engravings.     677  pages.     Svo.      .         .      $12.50 

BRANNT  —India  Rubber,  Gutta-Percha  and  Balata  : 

Occurrence,  Geographical  Distribution,  and  Cultivation,  Obtaining 
and  Preparing  the  Raw  Materials,  Modes  of  Working  and  Lhlizii.g 
them,  Including  Washing,  Maceration,  Mixing,  Vulcanizing, Rubber 
and  Gutta-Percha  Compounds,  Utilization  of  Waste,  etc.  By  WILL- 
IAM  T.  BRANNT.  Illustrated.  I2tno.  A  new  edition  in  preparation. 


HENRY  CAREY  BAIRD  &  CO.'S  CATALOGUE. 


BRANNT— WAHL.— The  Techno-Chemical  Receipt  Book: 

Containing  several  thousand  Receipts  covering  the  latest,  most  im- 
portant, and  most  useful  discoveries  in  Chemical  Technology,  and 
their  Practical  Application  in  the  Arts  and  the  Industries.  Edited 
chiefly  from  the  German  of  Drs.  Winckler,  Eisner,  Heintze,  Mier- 
zinski,  Jacobsen,  Roller  and  Heinzerling,  with  additions  by  WM.  T. 
BRANNT  and  WM.  H.  WAHL,  Ph.  D.  Illustrated  by  78  engravings. 
I2mo.  495  pages.  .  .  .  .  .  .  .  $2.00 

BROWN.  —  Five  Hundred  and  Seven  Mechanical  Movements  : 
Embracing  all  those  which  are  most  important  in  Dynamics,  Hy- 
draulics, Hydrostatics,  Pneumatics,  Steam  Engines,  Mill  and  other 
Gearing,  Presses,  Horology,  and  Miscellaneous  Machinery  ;  and  in- 
cluding many  movements  never  before  published,  and  several  of 
which  have  only  recently  come  into  use.  By  HENRY  T.  BROWN. 
I2mo.  .  .  .  .  .....  $1.00 

BUCKMASTER.— The  Elements  of  Mechanical  Physics : 
By  J.   C.   BUCKMASTEK.       Illustrated    with    numerous    engravings. 
I2mo.         .......... 

BULLOCK. — The  American  Cottage  Builder  : 
A  Series  of  Designs,  Plans  and  Specifications,  from  $200  to  $20,000, 
for  Homes  for  the  People ;  together  with  Warming,  Ventilation, 
Drainage,  Painting  and  Landscape  Gardening.  By  JOHN  BULLOCK, 
Architect  and  Editor  of  "  The  Rudiments  of  Architecture  and 
Building,"  etc.,  etc.  Illustrated  by  75  engravings.  8vo. 

BULLOCK. — The  Rudiments  of  Architecture  and  Building : 
For  the  use  of  Architects,  Builders,   Draughtsmen,   Machinists,  En- 
gineers and  Mechanics.     Edited  by  JOHN  BULLOCK,  author  of  "  The 
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8URGH. — Practical    Rules    for    the   Proportions   of     Modern 

Engines  and  Boilers  for  Land  and  Marine  Purposes. 
By  N.  P.  BURGH,  Engineer.     I2mo. 

BY LES  —  Sophisms    of    Free    Trade   and    Popular    Political 

Economy  Examined. 

By  a  BARRISTER  (SiR  JOHN  BARNARD  BYLES,  Judge  of  Com  IT.  on 
Pleas).  From  the  Ninth  English  Edition,  as  published  by  the 
Manchester  Reciprocity  Associaticn.  I2mo.  .  .  .  $1.25 

BOWMAN.— The  Structure  of  the  Wool  Fibre  in  its  Relation 

to  the  Use  of  Wool  for  Technical  Purposes: 
Being  the  substance,  with  additions,  of  Five  Lectures,  delivered  at 
the  request  of  the  Council,  to  the  members  of  the  Bradford  Technical 
College,  and  the  Society  of  Dyers  and  Colorists.  By  F.  H.  BOW- 
MAN, D.  Sc.,  F.  R.  S.  E.,  F.  L.  S.  Illustrated  by  32  engravings. 
8vo 

BYRNE. — Hand-Book  for  the  Artisan,  Mechanic,  and  Engi- 
neer : 

Comprising  the  Grinding  and  Sharpening  of  Cutting  Tools,  Abrasive 
Processes,  Lapidary  Work,  Gem  and  Glass  Engraving,  Varnishing 
and  Lackering,  Apparatus,  Materials  and  Processes  for  Grinding  and 


HENRY  CAREY  BAIRD  &  CO.'S  CATALOGUE.  7 

Polishing,  etc.  By  OLIVER  BYRNE.  Illustrated  by  185  wood  en- 
gravings. 8vo $4'°° 

8YRNE. — Pocket-Book  for  Railroad  and  Civil  Engineers : 

Containing  New,  Exact  and  Concise  Methods  for  Laying  out  Railroad 
Curves,  Switches,  Frog  Angles  and  Crossings ;  the  Staking  out  of 
work ;  Levelling ;  the  Calculation  of  Cuttings :  Embankments ;  Earth- 
work, etc,  By  OLIVER  BYRNE.  i8mo.,  full  bound,  pocket-book 
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BYRNE.— The  Practical  Metal- Worker's  Assistant : 

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and  Alloys  ;  Forging  of  Iron  and  Steel ;  Hardening  and  Tempering; 
Melting  and  Mixing;  Casting  and  Founding  ;  Works  in  Sheet  Met?Jj 
the  Processes  Dependent  on  the  Ductility  of  the  Metals ;  Soldering; 
and  the  most  Improved  Processes  and  Tools  employed  by  Metal- 
workers. With  the  Application  of  the  Art  of  Electro-Metallurgy  to 
Manufacturing  Processes ;  collected  from  Original  Sources,  and  from 
the  works  of  Holtzapffel,  Bergeron,  Leupold,  Piumier,  Napier, 
Scoffern,  Clay,  Fairbairn  and  others.  By  OLIVER  BYRNE.  A  new, 
revised  and  improved  edition,  to  which  is  added  an  Appendix,  con- 
taining The  Manufacture  of  Russian  Sheet- Iron.  By  JOHN  PERCY, 
M.  D.,  F.  R.  S.  The  Manufacture  of  Malleable  Iron  Castings,  and 
Improvements  in  Bessemer  Steel.  By  A.  A.  FESQUET,  Chemist  and 
Engineer.  With  over  Six  Hundred  Engravings,  Illustrating  every 
Branch  of  the  Subject.  8vo #3-5° 

BYRNE.— The  Practical  Model  Calculator: 

For  the  Engineer,  Mechanic,  Manufacturer  of  Engine  Work,  Naval 
Architect,  Miner  and  Millwright.  By  OLIVER  BYRNE.  8vo.,  nearly 
600  pages.  , (Scarce.; 

CABINET  MAKER'S  ALBUM  OF  FURNITURE: 

Comprising  a  Collection  of  Designs  for  various  Styles  of  Furniture. 
Illustrated  by  Forty-eight  Large  and  Beautifully  Engraved  Plates. 
Oblong,  8vo.  .  .  . $1.50 

CALLINGHAM. — Sign  Writing  and  Glass  Embossing: 

A  Complete  Practical  Illustrated  Manual  of  the  Art.  By  JAMES 
CALLINGHAM.  To  which  are  added  Numerous  Alphabets  and  the 
Art  of  Letter  Painting  Made  Easy.  By  JAMES  C.  BADENOCH.  258 

pages.     I2mo. $'-5° 

CAMPIN. — A  Practical  Treatise  on  Mechanical  Engineering: 
Comprising  Metallurgy,  Moulding,  Casting,  Forging,  Tools,  Work* 
shop  Machinery,  Mechanical  Manipulation,  Manufacture  of  Steam' 
Engines,  etc.  With  an  Appendix  on  the  Analysis  of  Iron  and  Iron 
Ores.  By  FRANCIS  CAMPIN,  C.  E.  To  which  are  added,  Observation* 
at)  the  Construction  of  Steam  Boilers,  and  Remarks  upon  Furnaces 
used  for  Smoke  Prevention ;  with  a  Chapter  on  Explosions  By  R« 
ARMSTRONG,  C.  E.,  and  JOHN  BOURNE,  (scarce.) 


HENRY  CAREY  BAIRD  &  CG.SS  CATALOGUE. 


CAREY.— A  Memoir  of  Henry  C.  Carey. 

By  DR.  WM.  ELDER.    With  a  portrait.     8vo.,  cloth        .        .        75 
CAREY.— The  Works  of  Henry  C.  Carey : 

Manual  of  Social  Science.     Condensed  from  Carey's  "  Principled 

of  Social  Science."     By  KATE  McKEAN.  i  vol.  I2mo.     .        £2.00 

Miscellaneous  Works.     With  a  Portrait.    2  vols.    8vo.         $1000 

Past,  Present  and  Future.     Svo.         ....         $2.50 

Principles  of  Social  Science.     3  volumes,  Svo.  .         .         $10.00 

The  Slave-Trade,  Domestic  and  Foreign ;  Why  it  Exists,  and 

How  it  may  be  Extinguished  (1853)      Svo.       ,         .         .         $2.00 

The  Unity  of  Law :  As   Exhibited   in   the   Relations  of  Physical, 

Social,  Mental  and  Moral  Science  (1872).     Svo.        .         .         $2.50 

CLARK. — Tramways,  their  Construction  and  Working  : 
Embracing  a  Comprehensive  History  of  the  System.  With  an  ex 
haustive  analysis  of  the  various  modes  of  traction,  including  horse 
power,  steam,  heated  water  and  compressed  air;  a  description  of  the 
varieties  of  Rolling  stock,  and  ample  details  of  cost  and  working  ex- 
penses. By  D.  KINNEAR  CLARK.  Illustrated  by  over  200  wood 
engravings,  and  thirteen  folding  plates.  I  vol.  Svo.  .  $5.00 

COLBURN. — The  Locomotive  Engine  : 

Including  a  Description  of  its  Structure,  Rules  for  Estimating  its- 
Capabilities,  and  Practical  Observations  on  its  Construction  and  Man 
agement.  By  ZERAH  COLBURN.  Illustrated.  121110. 

COLLENS. — The  Eden  of  Labor;  or,  the  Christian  Utopia. 
By  T.  WHARTON  COLLENS,  author  of  "  Humanics,"    "The  Hist.  7 

"     of  Charity,"  etc.     I2mo.     Paper  cover,  $1.00;   Cloth          .         $1.2- 

COOLEY. — A  Complete  Practical  Treatise  on  Perfumery  : 
Being  a  Hand-book  of  Perfumes,  Cosmetics  and  other  Toilet  Article: 
With   a  Comprehensive    Collection  of  Formulae.     By   ARNOLD 
COOLEY.    lamo #i.ob 

COOPER. — A  Treatise  on  the  use  of  Belting  for  the  TranL 

mission  of  Power. 

With  numerous  illustrations  of  approved  and  actual  methods  of  ar 
ranging  Main  Driving  and  Quarter  Twist  Belts,  and  of  Belt  Fasten 
ings.  Examples  and  Rules  in  great  number  for  exhibiting  and  cal 
culating  the  size  and  driving  power  of  Belts.  Plain,  Particular  and 
Practical  Directions  for  the  Treatment,  Care  and  Management  or 
Belts.  Descriptions  of  many  varieties  of  Beltings,  together  witn 
chapters  on  the  Transmission  of  Power  by  Ropes;  by  Iron  and 
Wood  Frictional  Gearing;  on  the  Strength  of  Belting  Leather;  and 
on  the  Experimental  Investigations  of  Morin,  Briggs,  and  others.  By 
JOHN  H.  COOPER,  M.  E.  Svo $3.50 

CRAIK.— The  Practical  American  Millwright  and  M^ler. 

By  DAVID  CRAIK,  Millwright.  Illustrated  by  numerous  wood  en- 
gravings and  two  folding  plates.  Svo (Scarce.) 


HENRY  CAREY  BAIRD  &  CO.'S  CATALOGUE.  9 

CROSS. — The  Cotton  Yarn  Spinner: 

Showing  how  the  Preparation  should  be  arranged  for  Different 
Counts  of  Yarns  by  a  System  more  uniform  than  has  hitherto  been 
practiced;  by  having  a  Standard  Schedule  from  which  we  make  all 
our  Changes.  By  RICHARD  CROSS.  122  pp.  I2mo.  .  75 

CRISTIANI. — A.  Technical  Treatise  on  Soap  and  Candles: 
With  a  Glance  at  the  Industry  of  Fats  and  Oils.     By  R.  S.  Ci4's- 
TIANI,  Chemist.     Author  of  "  Perfumery  and  Kindred  Arts."     Illus- 
trated by  176  engravings.     581  pages,.  8  vo.  $15.00 

COURTNEY.— The  Boiler  Maker's  Assistant  in  Drawing, 
Templating,  and  Calculating  Boiler  Work  and  Tank 
Work,  etc. 

Revised  by  D.  K.  CLARK.     102  ills.     Fifth  edition.  .    .         80 

COURTNEY. — The  Boiler  Maker's  Ready  Reckoner: 

With  Examples  of  Practical  Geometry  and  Templating.  Revised  by 
D.  K.  CLARK,  C.  E.  37  illustrations.  Fifth  edition.  •  $l.6o 

DAVIDSON.— A  Practical  Manual  of  House  Painting,  Grain- 
ing, Marbling,  and  Sign- Writing: 

Containing  full  information  on  the  processes  of  House  Painting  ir 
Oil  and  Distemper,  the  Formation  of  Letters  and  Practice  of  Sign- 
Writing,  the  Principles  of  Decorative  Art,  a  Course  of  Elementary 
Drawing  for  House  Painters,  Writers,  etc.,  and  a  Collection  of  Useful 
Receipts.  With  nine  colored  illustrations  of  Woods  and  Marbles, 
and  numerous  wood  engravings.  By  ELLIS  A  DAVIDSON.  i2mo. 

$2.00 

DAVIES.— A  Treatise  on  Earthy  and  Other    Minerals   and 

Mining: 

By  D.  C.  DAVIES,  F.  G.  S.,  Mining  Engineer,  etc.  Illustrated  by 
76  Engravings.  I2mo $5.00 

DAVIES. — A  Treatise  on  Metalliferous  Minerals  and  Mining: 
By  D.  C.  DAVIES,  F.  G.  S  ,  Mining  Engineer,  Examiner  of  Mines, 
Quarries  and  Collieries.  Illustrated  by  148  engravings  of  Geological 
Formations,  Mining  Operations  and  Machinery,  drawn  from  the 
practice  of  all  parts  of  the  world.  Fifth  Edition,  thoroughly  Revised 
and  much  Enlarged  by  his  son,  E.  Henry  Davies.  I2mo.,  524 
pages .  .  $5.00 

DIETERICHS.— A   Treatise  on    Friction,   Lubrication,   Oils 

and  Fats : 

The  Manufacture  of  Lubricating  Oils,  Paint  Oils,  and  of  Grease,  and 
the  Testing  of  Oils.  By  E.  F.  DIETERICHS,  Member  of  the  Franklin 
Institute;  Member  National  Association  of  Stationary  Engineers; 
Inventor  of  Dieterichs' Valve-Oleum  Lubricating  Oils.  I2mo.  (1906.) 
A  practical  book  by  a  practical  man.  .  .  .  .  #1.25 

DAVIS.— A  Practical  Treatise  on  the  Manufacture  of  Brick, 

Tiles  and  Terra-Cotta: 

Including  Stiff  Clay,  Dry  Clay,  Hand  Made,  Pressed  or  Front,  and 
Roadway  Paving  Brick,  Enamelled  Brick,  with  Glazes  and  Colors, 
Fire  Brick  and  Blocks.  Silica  Brick,  Carbon  Brick,  Glass  Pots,  Re- 


jo          HENRY  CAREY  BAIRD  &  CO.'S  CATALOG!)*;. 


torts,  Architectural  Terra-Cotta,  Sewer  Pipe,  Drain  Tile,  Glazed  and 
Unglazed  Rooting  Tile,  Art  Tile,  Mosaics,  and  Imitation  of  Intarsia 
or  Inlaid  Surfaces.  Comprising  every  product  of  Clay  employed  in 
Architecture,  Engineering,  and  the  Blast  Furnace.  With  a  Detailed 
Description  of  the  Different  Clays  employed,  the  Most  Modern 
Machinery,  Tools,  and  Kilns  used,  and  the  Processes  for  Handling, 
Disintegrating,  Tempering,  and  Moulding  the  Clay  into  Shape,  Dry- 
ing, Setting,  and  Burning.  By  Charles  Thomas  Davis.  Third  Edi- 
tion. Revised  and  in  great  part  rewritten.  Illustrated  by  261 
engravings.  662  pages  .  . 

DAVIS. — A  Treatise  on  Steam-Boiler  Incrustation  and  Meth- 
ods for  Preventing  Corrosion  and  the  Formation  of  Scale: 
By  CHARLES  T.  DAVIS.     Illustrated  by  65  engravings.     8vo. 
DAVIS.-.-The  Manufacture  of  Paper  : 

Being  a  Description  of  the  various  Processes  for  the  Fabrication, 
Coloring  and  Finishing  of  every  kind  of  Paper,  Including  the  Dif- 
ferent Raw  Materials  and  the  Methods  for  Determining  their  Values, 
the  Tools,  Machines  and  Practical  Details  connected  with  an  intelli- 
gent and  a  profitable  prosecution  of  the  art,  with  special  reference  to 
the  best  American  Practice.  To  which  are  added  a  History  of  Pa- 
per, complete  Lists  of  Paper-Making  Materials,  List  of  American. 
Machines,  Tools  and  Processes  used  in  treating  the  Raw  Materials, 
and  in  Making,  Coloring  and  Finishing  Paper.  By  CHARLES  T. 
DAVIS.  Illustrated  by  156  engravings.  608  pages,  8vo.  $6.00 
DAVIS. — The  Manufacture  of  Leather: 

Being  a  Description  of  all  the  Processes  for  the  Tanning  and  Tawing 
with  Bark,  Extracts,  Chrome  and  all  Modern  Tannages  in  General 
Use,  and  the  Currying,  Finishing  and  Dyeing  of  Every  Kind  of  Leather; 
Including  the  Various  Raw  Materials,  the  Tools,  Machines,  and  all 
Details  of  Importance  Connected  with  an  Intrlligent  and  Profitable 
Prosecution  of  the  Art,  with  Special  Reference  to  the  Best  American 
Practice.  To  which  are  added  Lists  of  American  Patents  (1884-1897) 
for  Materials,  Processes,  Tools  and  Machines  for  Tanning,  Currying, 
etc.  By  CHARLES  THOMAS  DAVIS.  Second  Edition,  Revised,  and 
in  great  part  Rewritten.  Illustrated  by  147  engravings  and  14  Sam- 
ples of  Quebracho  Tanned  and  Aniline  Dyed  Leathers.  8vo,  cloth, 

712  pages.     Price 

DAWIDOWSKY— BRANNT.— A  Practical  Treatise  on  the 
Raw  Materials  and  Fabrication  of  Glue,  Gelatine,  Gelatine 
Veneers  and  Foils,  Isinglass,  Cements,  Pastes,  Mucilages, 
etc. : 

Eased  upon  Actual  Experience.  By  F.  DAWIDOWSKY,  Technical 
Chemist.  Translated  from  the  German,  with  extensive  additions, 
including  a  description  of  the  most  Recent  American  Processes,  l.y 
WILLIAM  T.  BRANNT.  2d  revised  edition,  350  pages.  (1905.) 

Price       . •       53-00 

DE  GRAFF.— The  Geometrical  Stair-Builders'  Guide:' 

feeing  a  Plain  Practical  System  of  Hand-Railing,  embracing  all  it? 
necessary  Details,  and  Geometrically  Illustrated  by  twenty-two  Stee 
JE,ngravin'r>;  together  with  the  use  of  t lie  most  approved 
•.••/  Practical  Geometry  By  SIMON  DE  GRAFF,  Architect 


HENRY   CAREY   BAIRD   &   CO.'S   CATALOGUE.        M 

DE  KONINCK— DIETZ.— A  Practical  Manual  of  Chemical 
Analysis  and  Assaying : 

As  applied  to  the  Manufacture  of  Iron  from  its  Ores,  and  to  Cast  Iron, 
Wrought  Iron,  and  Steel,  as  found  in  Commerce.  By  L.  L.  DB 
KONINCK,  Dr.  Sc.,  and  E.  DIETZ,  Engineer.  Edited  with  Notes,  by 
ROBERT  MALLET,  F.  R.  S.,  F.  S.  G.,  M.  I.  C.  E.,  etc.  America* 
Edition,  Edited  with  Notes  and  an  Appendix  on  Iron  Ores,  by  A.  A, 
FESQUET,  Chemist  and  Engineer.  I2mo.  .  .  .  $1.00 

DUNCAN.— Practical  Surveyor's  Guide: 

Containing  the  necessary  information  to  make  any  person  of  com) 
mon  capacity,  a  finished  land  surveyor  without  the  aid  of  a  teacher^ 
By  ANDREW  DUNCAN.  Revised.  72  engravings,  2 14  pp.  I2mo.  $1.50 

DUPLAIS. — A  Treatise  on  the  Manufacture  and  Distillation 

of  Alcoholic  Liquors : 

Comprising  Accurate  and  Complete  Details  in  Regard  to  Alcohol 
from  Wine,  Molasses,  Beets,  Grr.'tn,  Rice,  Potatoes,  Sorghum,  Asphc 
del,  Fruits,  etc. ;  with  the  Di-tillat'on  and  Rectification  of  Brandy, 
Whiskey,  Rum,  Gin,  Swiss  Absinthe,  etc.,  the  Preparation  of  Aro- 
matic Waters,  Volatile  Oils  or  Essences,  Sugars,  Syrups,  Aromatic 
Tinctures,  Liqueurs,  Cordial  Wines,  Effervescing  Wines,  etc.,  the 
Ageing  of  Brandy  and  the  improvement  of  Spirits,  with  Copious 
Directions  and  Tables  for  Testing  and  Reducing  Spirituous  Liquors, 
etc,,  etc.  Translated  and  Edited  from  the  French  of  MM.  DUPLAIS, 
By  M.  McKENNiE,  M.  D.  Illustrated  74*  pp.  8vo.  $15.00 

DYER  AND  COLOR-MAKER'S  COMPANION: 

Containing  upwards  of  two  hundred  Receipts  lor  making  Colors,  on 
the  most  approved  principles,  for  all  the  various  styles  and  fabrics  now 
in  evistence ;  with  the  Scouring  Process,  and  plain  Directions  for 
Preparing,  Wa$hing-off,  and  Finishing  the  Goods.  I2mo. 

EIDHERR. — The  Techno-Chemical  Guide  to  Distillation: 
A  Hand-Book  for  the  Manufacture  of  Alcohol  and  AlcohoUc  Liquors, 
including  the   Preparation  of  Malt  and   Compressed  Yeast.     Edited 
from  tlit-  <  ierman  of  Eii.  Eidherr. 

EDWARDS. — A  Catechism  of  the  Marine  Steam-Engine, 
For  the  use  of  Engineers,  Firemen,  and  Mechanics.  A  Practical 
Work  for  Practical  Men.  By  EMORY  EDWARDS,  Mechanical  Engi- 
neer. Illustrated  by  sixty-three  Engravings,  including  examplt-s  of 
(he  most  modern  Engines.  Third  edition,  thoroughly  revised,  with 
much  addition.d  matter.  12 mo.  414  pages  .  .  *l«5° 

DWARDS. — Modern  American  Loccmotive  Engines, 
Their  Design,  Construction  and  Management.     By  EM  :>R¥  EDWARDS* 
Illustrated  I2mo $1.50 

EDWARDS.— The  American  Steam  Engineer: 

Theoretical  and  Practical,  with  examples  of  the  latent  and  most  ap- 
proved American  practice  in  the  design  and  construction  of  Steam 
Engines  and  Boilers.  For  the  use  of  engineers,  machinists,  boiler- 
w»akers,  and  engineering  students.  By  EMORY  EDWARDS.  Fully 
Uiustrated.  419  pages.  I2mo.  ....  |i.5° 


12         HENRY  CAREY  BAIRD  &  CO.'S   CATALOGUE. 


EDWARDS. — Modern  American  Marine  Engines,  Boilers,  an* 

Screw  Propellers, 

Their  Design  and   Construction.     Showing  the  Present  Practice  ot 
the  most   Eminent  Engineers  and   Marine   Engine  Builders  in  the 
United  States.    Illustrated  by  30  large  and  elaborate  plates.  4to.  $2.00 
EDWARDS. — The  Practical  Steam  Engineer's  Guide 

In  the  Design,  Construction,  and  Management  of  American  Stationary, 
Portable,  and  Steam  Fire-Engines,  Steam  Pumps,  Boilers.  Injector^ 
Governors,  Indicators,  Pistons  and  Rings,  Safety  Valves  and  Steam 
Gauges.  For  the  use  of  Engineers,  Firemen,  and  Steam  Ujers.  B> 
EMORY  EDWARDS.  Illustrated  by  119  engravings.  ^20  pages. 

I2mo $2.00 

EISSLER.— The  Metallurgy  of  Silver  : 

A  Practical  Treatise  on  the  Amalgamation,  Roasting,  and  Lixiviation 
of  Silver  Ores,  including  the  Assaying,  Melting,  and  Refining  of 
Silver  Bullion.  By  M.  EISSLER.  124  Illustrations.  336  pp. 

I2mo $425 

ELDER. — Conversations  on  the  Principal  Subjects  of  Political 

Economy. 
By  DR.  WILLIAM  ELDER.     8vo.       ...  .        $i-$o 

ELDER. — Questions  of  the  Day, 

Economic  and  Social.     By  DR.  WILLIAM  ELDER.     Svo.      .     $3.00 
ERNI  AND  BROWN.— Mineralogy  Simplified. 

Easy  Methods  of  Identifying  Minerals,  including  Ores,  by  Means  of 
the  Blow-pipe,  by  Flame  Reactions,  by  Humid  Chemical  Analysis, 
and  by  Physical  Tests.      By  HENRI  ERNI,  A.  M.,  M.  D.    Fourth  Edi- 
tion, revised,  re-arranged  and  with  the  addition  of  entirely  new  matter, 
including  Tables  for  the  Determination  of  Minerals  by  Chemical  and 
Pyrognostic  Characters,  and  by  Physical  Characters      By  AMOS  P. 
BROWN,  E.  M.,  Ph.  D.    464 pp.. illustrated  by  123  engravings,  pocket- 
book  form,  full  flexible  morocco,  gilt  edges       .         .         .         $2.50 
FAIRBAIRN.     The  Principles  of  Mechan:sm  and  Machinery 

of  Transmission  : 

Comprising    the    Principles    of  Mechanism,   Wheels,    and    Pulleys, 
Strength  and  Proportion  of  Shafts,  Coupling  of  Shafts,  and  Engag- 
ing and   Disengaging  Gear.     By   SIR  WILLIAM  FAIRBAIRN,  Bart. 
C.    E.       Beautifully    illustrated   by   over    150    wood-cuts.      In   one 
volume,   I2mo.        ........         $2.00 

FLEMING. — Narrow  Gauge  Railways  in  America  : 

A  Sketch  of  their  Rise,  Progress,  and  Success.     Valuable  Statistics 
as  to  Grades,  Curves,  Weight  of  Rail,  Locomotives,  Cars,  etc.      By 
HOWARD  FLEMING.     Illustrated,  8vo.     .         .         .         .         $1.00 

FORSYTH. — Book  of  Designs  for  Headstones,  Mural,  and 

other  Monuments  : 

Containing  78  Designs.     By  JAMES  FORSYTH,     With  an  Introduction 
by  CHARLES  BOUTELL,  M.  A.     4to.,  cloth       .         .         .        $3 .00 
FRIEDBERG.     Utilization  of  Bones  by  Chemical   Means; 
especially  the  Modes  of  Obtaining   Fat,  Glue,  Manures, 
Phosphorus  and  Phosphates. 
Illustrated.     8vo.     (In  preparation.) 


HENRY   CAREY    BAIRD   &   CO.'S   CATALOGUE.        13 


FRANKEI HUTTER.— A  Practical  Treatise  on  the  Mann* 

facture  of  Starch,  Glucose,  Starch-Sugar,  and  Dextrine: 
Based  on  the  German  of  LADISLAUS  VON  WAGNER,  Professor  in  the 
Royal  Technical  High  School,  Buda-Pest,  Hungary,  and  other 
authorities.  By  JULIUS  FRANKEL,  Graduate  ot  the  Polytechnic 
School  of  Hanover.  Edited  by  ROBERT  HUTTER,  Chemist,  Practical 
Manufacturer  of  Starch-Sugar.  Illustrated  by  58  engravings,  cover- 
ing  every  branch  of  the  subject,  including  examples  of  the  most 
Recent  and  Best  American  Machinery.  8vo.,  344  pp. 

GARDNER.— The  Painters  Encyclopaedia: 
.Containing  Definitions  of  ail  Important  Words  in  the  Art  of  Plain 
and  Artistic  Painting,  with  Details  of  Practice  in  Coach,  Carriage, 
Railway  Car,  House,  Sign,  and  Ornamental  Painting,  including 
Graining,  Marbling,  Staining,  Varnishing,  Polishing,  Lettering, 
Stenciling,  Gilding,  Bronzing,  etc.  By  FRANKLIN  B.  GARDNER. 
158  Illustrations.  I2mo.  427  pp.  .  .  .  .  .  #2.OC 

GARDNER.— Everybody's  Paint  Book: 

A  Complete  Guide  to  the  Art  of  Outdoor  ami  Indoor  Painting.  38 
illustrations.  i2mo,  183  pp.  .  .  .  $l.oo 

3EE. — The  Jeweller's    Assistant   in   the    Art  of    Working  in 

Gold: 
A  Practical  Treatise  foi  Masters  and  Workmen.     I2mo.      .       $3-°° 

GEE. — The  Goldsmith's  Handbook : 

Containing  full  instructions  for  the  Alloying  and  Working  of  Gold, 
including  the  Art  of  Alloying,  Melting,  Reducing,  Coloring,  Col 
lecting,  and  Refining;  the  Processes  of  Manipulation,  Recovery  of 
Waste;  Chemical  and  Physical  Properties  of  Gold;  with  a  New 
System  of  Mixing  its  Alloys ;  Solders,  Enamels,  and  other  Useful 
Rules  and  Recipes.  By  GEORGE  E.  GEE.  I2mo.  .  .  £1.25 

GEE.— The  Silversmith's  Handbook  : 

Containing  full  instructions  for  the  Alloying  and  Working  of  Silver, 
including  the  different  modes  of  Refining  ind  Melting  the  Metal;  its 
Solders ;  the  Preparation  of  Imitation  Alloys ;  Methods  of  Manipula- 
tion ;  Prevention  of  Waste  ;  Instructions  for  Improving  and  Finishing 
the  Surface  of  the  Work ;  together  with  other  Useful  Information  and 
Memoranda.  By  GEORGE  E.  GEE.  Illustrated.  I2mo.  Si. 25 

GOTHIC  ALBUM  FOR  CABINET-MAKERS: 

Designs  for  Gothic  Furniture.     Twenty-three  plates.     Oblong  £1.00 

3RANT. — A  Handbook  on  the  Teeth  of  Gears  : 
Their  Curves,  Properties,  and  Practical  Construction.     By  GEORGE 
B.  GRANT.     Illustrated.     Third  Edition,  enlarged.     8vo.          $1.00 

GREENWOOD.— Iron  and  Steel: 

Vol.  I.  Iron  :  Its  Sources,  Properties,  and  Manufacture.  By  WILL- 
IAM HENRY  GREENWOOD.  Revised  and  Re-written  by  A.  HUM- 
BOLDT  SEXTON.  255pp.  Illustrated  12010.  .  .  .  $1.00 
Vol.  II.  Steel  •  Its  Varieties,  Properties,,  and  Manufacture  By 
WILLIAM  HENRY  GREENWOOD.  Revised  and  Re-written  by  A. 
HUMBOLDT  SEXTON.  254pp.  Illustrated.  I2mo.  .  .  $1.00 


14       HENRY   CAREY   BAIRD   &    CO.'S   CATALOGUE: 


GREGORY.— Mathematics  for  Practical  Men  : 

Adapted  to  the  Pursuits  of  Surveyors,  Architects,  Mechanics,  and 

Civil  Engineers.     By  OLINTHUS  GREGORY.     8vo.,  plates        $3.00 

GRISWOLD. — Railroad  Engineer's  Pocket  Companion  for  tlu 

Field : 

Comprising  Rules  for  Calculating  Deflection  Distances  and  Angles 
Tangential  Distances  and  Angles,  and  all  Necessary  Tables  for  En 
gineers;  also  the  Art  of  Levelling  from  Preliminary  Survey  to  th« 
Construction  of  Railroads,  intended  Expressly  for  the  Young  En- 
gineer, together  with  Numerous  Valuable  Rules  and  Examples.  By 

W.  GRISWOLD.     I2mo.,  tucks $1-5° 

GRUNER. — Studies  of  Blast  Furnace  Phenomena: 

By  M.  L.  GRUNER,  President  of  the  General  Council  of  Mines  o5 
France,  and  lately  Professor  of  Metallurgy  at  the  Ecole  des  Mines, 
Translated,  with  the  author's  sanction,  with  an  Appendix,  by  L.  D. 
B.  GORDON,  F.  R.  S.  E.,  F.  G.  S.  8vo.  .  .  .  $2.50 

Hand-Book  of  Useful  Tables  for  the  Lumberman,  Farmer  and 

Mechanic: 

Containing  Accurate  Tables  of  Logs  Reduced  to  Inch  Board  Meas. 
ure,  Plank,  Scantling  and  Timber  Measure ;  Wages  and  Rent,  by 
Week  or  Month;  Capacity  of  Granaries,  Bins  and  Cisterns;  Land 
Measure,  Interest  Tables,  with  Directions  for  Finding  the  Interest  on 
any  sum  at  4,  5,  6,  7  and  8  per  cent.,  and  many  other  Useful  Tables. 
32  mo.,  boards.  I6&  pages  .  .  .  •  .  .  .2$ 

HASERICK. — The  Secrets  of  the  Art  of  Dyeing  Wool,  Cotton, 

and  Linen, 

Including  B'.eachir.g  an/i  Coloring  Wool  and  Cotton  Hosiery  and 
Random  Yarns.  A  Treatise  based  on  Economy  and  Practice.  By 
E.  C.  HASERICK.  Illustrated  by  323  Dyed  Patterns  of  the  Varnt 

or  Fabrics.    8vo #4- 5° 

HATS  AND  FELTING: 

A  Practical  Treatise  on  their  Manufacture.     By  a  Practical  Hatte* 

Illustrated  by  Drawings  of  Machinery,  etc.    8vo.       .        .       $1.00 

HERMANN. — Painting  on  Glass  and  Porcelain,  and  Enamel 

Painting: 

A  Complete  Introduction  to  the  Preparation  of  all  the  Colors  and 
Fluxes  Used  for  Painting  on  Glass,  Porcelain,  Enamel,  Faience  and 
Stoneware,  the  Color  Pastes  and  Colored  Glasses,  together  with  • 
Minute  Description  ot  the  Firing  ot  Colors  and  Enamels,  on  tht 
Basis  of  Personal  Practical  Experience  of  the  Art  up  to  Date.  18 

illustrations.     Second  edition. $4.00 

HAUPT.— Street  Railway  Motors: 

With  Descriptions  and  Cost  of  Plants  and  Operation  of  the  Various 
Systems  now  in  Use. 


HENRY  CAREY  BAIRD  &  CO.'S  CATALOGUE.         15 

HAUPT. — A  Manual  of  Engineering  Specifications  and  Con- 
tracts. 
By   LEWIS   M.  HAUPT,  C.   E.     Illustrated  with  numerous   maps. 

328pp.    8vo $3  oo 

HAUPT.— The  Topographer,  His  Instruments  and  Methods. 
By  LEWIS  M.  HAUPT,  A.  M.,  C.  E.     Illustrated  with   numerous 
plates,  maps  and  engravings.     247  pp.    8vo.      .         .         .         $3.00 
HUGHES. — American  Miller  and  Millwright's  Assistant: 

By  WILLIAM  CARTER  HUGHES.     I2mo.     ....        $1.50 
HULME. — Worked  Examination  Questions  in  Plane  Geomet- 
rical Drawing  : 

For  the  Use  of  Candidates  for  the  Royal  Military  Academy,  Wool- 
wich ;  the  Royal  Military  College,  Sandhurst ;  the  Indian  Civil  En- 
gineering College,  Cooper's  Hill  ;  Indian  Public  Works  and  Tele- 
graph Departments ;  Royal  Marine  Light  Infantry  ;  the  Oxford  and 
Cambridge  Local  Examinations,  etc.  By  F.  EDWARD  HULME,  F.  L. 
S.,  F.  S.  A.,  Art-Master  Marlborough  College.  Illustrated  by  300 

examples.     Small  quarto $1.00 

JEKVIS.— Railroad  Property: 

A   Treatise   on   the    Construction   and    Management   of    Railways; 
designed  to  afford  useful  knowledge,  in    the   popular  style,  to  the 
holders  of  this  class  of  property  ;  as  well  as  Railway  Managers,  Offi 
cers,  and  Agents.     By  JOHN  B.  JERVIS,  late   Civil  Engineer  of  the 
Hudson  River  Railroad,  Croton  Aqueduct,  etc.    i2mo.,  cloth      $1.^0 
KEENE.— A  Hand-Book  of  Practical  Gauging: 

For  the  Use  of  Beginners,  to  which  is  added  a  Chapter  on  Distilla 
tion,  describing  the  process  in   operation  at  the  Custom- House  for 
ascertaining  the  Strength  of  Wines.     By  JAMES  B.  KEENE,  of  H.  M. 
Customs.     8vo.  ........ 

KELLEY. — Speeches,  Addresses,  and  Letters  on  Industrial  and 

Financial  Questions : 

By  HON.  WILLIAM  D.  KELLEY,  M.  C.     544  pages,  8vo.  .        $2.00 
KOENIG.— Chemistry  Simplified : 

A  Course  of  Lectures  on  the  Non-Metals  Based  upon  the  Natural 
Evolution  of  Chemistry.  Designed  Primarily  for  Engineers.  By 
GEORGE  AUGUSTUS  KOENIG,  Ph.  D.,  A.  M.,  E.  M.,  Professor  of 
Chemistry,  Michigan  College  of  Mines,  Houghton.  Illustrated  by 
103  Original  Drawings.  449  pp.  I2mo.,  (1906).  .  .  $2.2$ 
KEMLO.— Watch- Repairer's  Hand-Book: 
Being  a  Complete  Guide  to  the  Young  Beginner,  in  Taking  Apart, 
Putting  Together,  and  Thoroughly  Cleaning  the  English  Lever  and 
other  Foreign  Watches,  and  all  American  Watches.  By  F.  KfiMLO, 
Practical  Watchmaker.  With  Illustrations.  I2mo.  £1.25 


16          HENRY  CAREY  BAIRD  &  CO.'S  CATALOGUE. 

KENTISH. — A  Treatise  on  a  Box  of  Instruments, 

And  the  Slide  Ruie ;  with  the  Theory  of  Trigonometry  and  Log* 
rithms,  including  Practical  Geometry,  Surveying,  Measuring  of  Tim 
her,  Cask  and  Malt  Gauging,  Heights,  and  Distances.  By  THOMA' 
KENTISH.  In  one  volume.  I2mo.  .  .  .  .  $i-O£ 

KIRK.— A  Practical  Treatise  on  Foundry  Irons. 

Comprising  Pig  Iron,  and  Fracture  Grading  of  Pig  and  Scrap  Irons; 
Scrap  Irons;  Mixing  Irons;  Elements  and  Metalloids;  Grading  Iron 
by  Analysis;  Chemical  Standards  for  Iron  Castings;  Testing  Cast 
Iron;  Semi  Steel ;  Malleable  Iron;  Etc.,  Etc.  By  EDWARD  KIRK, 
Practical  Moulder  and  Melter,  Consulting  Expert  in  Melting.  Illus 
trated.  294  pages.  8vo.  1911.  #3.00 

KICK.— Flour  Manufacture. 

A  Treatise  on  Milling  Science  and  Practice.  By  FREDERICK  KICK 
Imperial  Regierungsrath,  Professor  of  Mechanical  Technology  in  th«. 
imperial  German  Polytechnic  Institute,  Prngue.  Translated  from 
the  second  enlarged  and  revised  edition  with  supplement  by  H.  H 
P.  POWLES,  Assoc.  Memb.  Institution  of  Civil  Engineers.  Illustrated 
with  28  Plates,  and  167  Wood-cuts.  367  pages.  8vo.  .  Jgio.OO 

^INGZETT.— The   History,  Products,  and   Processes  of  th» 

Alkali  Trade : 

including  the  most  Recent  Improvements.  By  CHARLES  THOMA* 
KTVOZETT.  Consulting  Chemist.  With  23  illustrations.  8vo.  $2.00 

«IRK.—  The  Cupola  Furnace : 

A  Practical  Treatise  on  the  Construction  and  Management  of  Foundry 
Cupolas.  By  EDWARD  KIRK,  Practical  Moulder  and  Melter,  Con- 
sulting Expert  in  Melting.  Illustrated  by  106  engravings.  Third 
Edition,  revised  and  enlarged.  482  pages.  8vo.  1910.  #35° 

LANDRIN.— A  Treatise  on  Steel : 

Comprising  its  Theory,  Metallurgy.  Properties,  Practical  Working, 
and  Use.  By  M.  H.  C.  LANDRIN,  JR.  From  the  French,  by  A.  A. 
FESQUET.  i2mo.  .  ••:•:•.  .  .  .  .  .  .  J&i.oo 

LANGBEIN.— A    Ccrr.piete  Treatise  on  the  E!ectro-Deposl 

tion  of  Metals : 

Comprising  Electro-Plating  and  Galvanoplastic  Operations,  the  De- 
position of  Metals  by  the  Contact  and  Immersion  Processes,  the  Color- 
ing of  Metals,  the  Methods  of  Grinding  and  Polishing,  as  well  as- 
Description  of  the  Voltaic  Cells,  Dynamo- Electric  Machines,  Ther. 
mopyles,  and  of  the  Materials  and  Processes  Used  in  Every  Depart- 
ment of  the  Art.  Translated  from  the  Fifth  German  Edition  ot 
DR.  GEORGE  LANGBEIN,  Proprietor  of  a  Manufactory  for  Chemical 
Products,  Machines,  Apparatus  and  Utensils  for  Electro- Platers,  and 
of  an  Electro-Plating  Establishment  in  Leipzig.  With  Additions  by 
WILLIAM  T.  BRANNT,  Editot  of  ''The  Techno-Chemical  Receipt 
Book."  Sixth  Edition,  Revised  and  Enlarged.  Illustrated  by  163 
Engravings,  8vo  ,  725  pages  (1909)  .  .  .  .  .  $4  oo 

LEHNER.— The  Manufacture  of  Ink: 

Comprising  the  Raw  Materials,  and  the  Preparation  of  Wrting, 
Copyingand  Hektograph  Inks,  Safety  Inks.  Ink  Extracts  and  Pow- 
ders, etc.  Translated  from  the  Germnn  of  SIGMUND  LKHNER.  with 
additions  by  WILLIAM  T.  BRANNT.  Iliu.-.trated.  I2mo.  $2.00 


HENRY  CAREY    BAIRD   &  CO.'S   CATALOGUE.        17 

LARKIN. — The  Practical  Brass  and  Iron  Founder's  Guide; 
A  Concise  Treatise  on  Brass  Founding,  Moulding,  the  Metals  and 
their  Alloys,  etc. ;  to  which  are  added  Recent  Improvements  in  the 
Manufacture  of  Iron,  Steel  by  the  Bessemer  Process,  etc.,  etc.  Bj 
JAMES  LARKIN,  late  Conductor  of  the  Brass  Foundry  Department  if 
Reany,  Neafie  &  Co.'s  Penn  Works,  Philadelphia.  New  edition, 
revised,  with  extensive  additions.  414  pages.  I2mo.  .  $2.50 

LEROUX. — A    Practical    Treatise    on    the    Manufacture   of 

Worsteds  and  Carded  Yarns  : 

Comprising  Practical  Mechanics,  with  Rules  and  Calculations  applied 
to  Spinning;  Sorting,  Cleaning,  and  Scouring  Wools;  the  English 
and  French  Methods  of  Combing,  Drawing,  and  Spinning  Worsteds, 
and  Manufacturing  Carded  Yarns.  Translated  from  the  French  of 
CHARLES  LEROUX,  Mechanical  Engineer  and  Superintendent  of  a 
Spinning- Mill,  by  HORATIO  PAINE,  M.  D.,  and  A.  A.  FESQUKT, 
Chemi?t  and  Engineer.  Illustrated  by  twelve  large  Plates.  To  which 
is  added  an  Appendix,  containing  Extracts  from  the  Reports  of  the 
International  Jury,  and  of  the  Artisans  selected  by  the  Committee 
appointed  by  the  Council  of  the  Society  of  Arts,  London,  on  Woolei 
and  Worsted  Machinery  and  Fabrics,  as  exhibited  in  the  Paris  Uni. 
versal  Exposition,  1867.  8vo.  .  .  •  •  .  $3.00 

LEFFEL.— The  Construction  of  Mill-Dams : 
Comprising  also  the  Building  of  Race  and  Reservoir  Embankment* 
and  Head-Gates,  the  Measurement  of  Streams,  Gauging  of  Water 
Supply,  etc.     By  JAMES  LEFFEL  &  Co.    Illustrated  by  58  engravings. 
8vo (Scarce.) 

LESLIE.— Complete  Cookery: 

Directions  for  Cookery  in  its  Various  Branches.  By  Miss  LESLIE 
Sixtieth  thomsand.  Thoroughly  revised,  with  the  addition  of  New 
Receipts.  I2mo.  .  .  fi.oo 

LE  VAN. — The  Steam  Engine  and  the  Indicator : 

Their  Origin  and  Progressive  Development;  including  the  Most 
Recent  Examples  of  Steam  and  Gas  Motors,  together  with  the  Indi- 
cator, its  Principles,  its  Utility,  and  its  Application.  By  WILLIAM 
BARNET  LE  VAN.  Illustrated  by  205  Engravings,  chiefly  of  Indi- 
cator-Cards. 469  pp.  8vo .  $2.00 

LIEBER.— Assayer's  Guide  : 

Or,  Practical  Directions  to  Assayers,  Miners,  and  Smelters,  for  the 
Tests  and  Assays,  by  Heat  and  by  Wet  Processes,  for  the  Ores  of  all 
t|^  principal  Metals,  of  Gold  and  Silver  Coins  a»d  Alloys,  and  of 
Coal,  etc.  By  OSCAR  M.  LIEBER.  Revised.  283  pp.  I2me*.  $1.50 

"U>ckwood's  Dictionary  of  Terms  : 

Used  in  the  Practice  of  Mechanical  Engineering,  embracing  those 
Current  in  the  Drawing  Office,  Pattern  Shop,  Foundry,  Fitting,  Turn- 
ing, Smith's  and  Boiler  Shops,  etc.,  etc.,  comprising  upwards  of  Six 
Thousand  Definitions.  Edited  by  a  Foreman  Pattern  Maker,  author 
A  "  Pattern  Making."  417  pp.  I2mo.  .  .  .  $3,75 


18         HENRY  CAREY  BAfRD  &  CO.'S  CATALOGUE. 

LUKIN.— The  Lathe  and  Its  Uses  : 

Or  Instruction  in  the  Art  of  Turning  Wood  and  Metal.  Including 
a  Description  of  the  Most  Modern  Appliances  for  the  Ornamentation 
of  Plane  and  Curved  Surfaces,  an  Entirely  Novel  P'orm  of  Lathe 
for  Eccentric  and  Rose-Engine  Turning;  A  Lathe  and  Planing 
Machine  Combined;  and  Other  Valuable  Matter  Relating  to  the 
Art.  Illustrated  by  462  engravings.  Seventh  edition.  315  pages. 
Svo #4.25 

MAIN  and  BROWN. — Questions  on  Subjects  Connected  with 

the  Marine  Steam- Engine: 

And  Examination  Papers;  with  Hints  for  their  Solution.  By 
THOMAS  J.  MAIN,  Professor  of  Mathematics,  Royal  ""tfaval  College, 
and  THOMAS  BROWN,  Chief  Engineer,  R.  N.  I2mo.,  cloth  . 

MAIN  and  BROWN.— The  Indicator  and  Dynamometer: 
With  their  Practical  Applications  to  the  Steam-Engine.     By  THOMAS 
J,  MAIN,   M.  A.  F.  R.,  Ass't    S.   Professor    Royal   Naval  College, 
Portsmouth,  and  THOMAS  BROWN,  Assoc.  Inst.  C.  E.,  Chief  Engineer 
R.  N.,  attached  to  the  R.  N.  College.     Illustrated.     Svo.  . 

MAIN  and  BROWN.— The  Marine  Steam-Engine. 
By  THOMAS  J.  MAIN,  F.  R.  Ass't  S.  Mathematical  Professor  at  the 
Royal   Naval   College,  Portsmouth,  and   THOMAS   BROWN,  Assoc. 
Inst.  C.  E.,  Chief  Engineer  R.  N.     Attached  to  the  Royal  Naval 
College.     With  numerous  illustrations.     Svo. 

MAKINS.— A  Manual  of  Metallurgy: 

By  GEORGE  HOGARTH  MAKINS.  100  engravings.  Second  edition 
rewritten  and  much  enlarged.  I2mo.,  592  pages 

MARTIN.— Screw-Cutting  Tables,  for  the  Use  of  Mechanic*) 

Engineers  : 

Showing  the  Proper  Arrangement  of  Wheels  for  Cutting  the  Threads 
of  Screws  of  any  Required  Pitch ;  with  a  Table  for  Making  the  Uni- 
versal Gas-Pipe  Thread  and  Taps.  By  W.  A.  MARTIN,  Engineer. 
8vo .50 

MICHELL.— Mine  Drainage: 

Being  a  Complete  and  Practical  Treatise  on  Direct-Acting  Under 
ground  Steam  Pumping  Machinery.  With  a  Description  of  a  large 
number  of  the  best  known  Engines,  their  General  Utility  and  ih« 
Special  Sphere  of  their  Action,  the  Mode  of  their  Application,  and 
their  Merits  compared  with  other  Pumping  Machinery.  By  STEPHEM 
MiCHFf.L.  Illustrated  by  247  engravings.  8vo.,  369  pages.  $1250 

MOLES  WORTH.— Pocket-Book   of    Useful    Formulae   and 
Memoranda  for  Civil  and  Mechanical  Engineers. 
By  GUILFORD  L.  MOLESWORTH,  Member  of  the  Institution  of  Civil 
Engineers,  Chief  Resident  Engineer  of  the  Ceylon  Railway.     Full- 
bound  in  Pocket-book  form       .         .         <-        .        .        .         $1.09 


iiENRY  CAREY  BAIRD  &  CO.'S  CATALOGUE*          T9 

4IOORE.— The  Universal  Assistant  and  the  Complete  Me 

cnanii . 

Containing  over  one  million  Industrial  Facts,  Calculations,  Receipt*, 
Processes,  Trades  Secrets,  Rules,  Business  Forms,  Legal  Items,  Etc., 
in  every  occupation,  from  the  Household  to  the  Manufactory.  B)1 
R.  MOORE.  Illustrated  by  500  Engravings.  I2mo.  .  $2.50 

iMORRIS. — Easy  Rules  for  the  Measurement  of  Earthworks: 
By  means  of  the  Prismoidal   Formula.     Illustrated  with  Numerou? 
Wood-Cuts,  Problems,  and  Examples,  and  concluded  by  an  Exten- 
sive Table  for  finding  the  Solidity  in  cubic  yards  from  Mean  Areas, 
The  whole  being  adapted  for  convenient  use  by  Engineers,  Surveyors 
Contractors,  and  others  needing  Correct  Measuremen ';?.  if  Earthwork 
By  ELWOOD  MORRIS,  C.  E.    8vo.    .... 
"MAUCHLINE.— The  Mine  Foreman's  Hand-Book 

t )(  Practical  and  Theoretical  Information  on  the  Opening,  Venti 
lating,  and  Working  of  Collieries.  Questions  and  Answers  on  Prac- 
tical and  Theoretical  Coal  Mining.  Designed  to  Assist  Students  and 
Others  in  Passing  Examinations  for  Mine  Foremanships.  By 
ROBERT  MAUCHLIINE.  3d  Edition.  Thoroughly  Revised  and  En- 
larged by  F.  ERNEST  BRACKETT.  134  engravings,  8vo.  378  pages. 
('90S) fc-75 

51 A  PI  EH. — A  System  of  Chemistry  Applied  to  Dyeing. 
By  JAMES  NAPIER,  F.  C.  S.  A  New  and  Thoroughly  Revised  Ed* 
tion.  Completely  brought  up  to  the  present  state  of  the  Science, 
including  the  Chemistry  of  Coal  Tar  Colors,  by  A;  A.  FESQUET, 
Chemist  and  Engineer.  With  an  Appendix  o>i  Dyeing  and  Caiicc 
Printing,  as  shown  at  the  Universal  Exposition,  Paris,  1867.  Illus 
trated.  8vo.  422  pages $2.00 

NEVILLE.— Hydraulic  Tables,  Coefficients,  and  Formulae,  fo» 
finding   the   Discharge  of  Water   from    Orifices,   Notches 
Weirs,  Pipes,  and  Rivers: 

Third  Edition,  with  Additions,  consisting  of  New   Formula  for  the 
>ischarge  from  Tidal  and  Flood  Sluices  and  Siphons;  general  infor 
nation  on  Rainfall,  Catchment-Basins,  Damage,  Sewerage,  Wa.ei 
Supply  for  Towns  nnd  Mill  Power      Bv  ijJTN  NEVILLK.  C.  E.  M  R 
I.  A. ;  Fellow  of  the  Royal  Geological  Be -jfr&y  of  Ireland.    Thicl 
I2mo.        .........  Scarce 

IEWBERY.— Gleanings     trom     Qrnamgutal     Art    of    everj 

style : 

Drawn  from  Examples  in  the  British,  South  Kensington,  Indian, 
Crystal  Palace,  and  other  Museums,  the  Exhibitions  of  1851  and 
1862,  and  the  best  English  and  Foreign  works.  In  a  series  of  100 
exquisitely  drawn  Plates,  containing  many  hundred  examples.  15* 
ROBERT  NEWBERY.  410.  ......  (Scutes.. j 

NICHOLLS.  -The  Theoretical  and  Practical  Boiler-  Maker  an* 

Engineer's  Reference  Book: 

Containing  a  variety  of  Useful  Information  for  Employers  of  Laboc 
Foremen  a-\d  Working  Boiler-Makers  Iron,  Copper,  and  Tinsmiths 


HENRY  CAREY  BAIRD  &  CO.'S  CATALOGUE. 


Draughtsmen,  Engineers,  the  General  Steam- using  Public,  and  for  tha 
Use  of  Science  Schools  and  Classes.  By  SAMUEL  NICHOLLS.  Illu* 
trated  by  sixteen  plaies,  1 2mo. $2.50 

NICHOLSON.— A  Manual  of  the  Art  of  Bookbinding : 
Containing  full  instructions  in  the  different  Branches  of  Forwarding, 
Gilding,  and  Finishing.     Also,  the  Art  of  Marbling  Book-edges  and 
Paper.     By  JAMES  B.  NICHOLSON.     Illustrated.  I2mo.,  cloth     $2.25 

NICQLLS.— The  Railway  Builder: 

A  Hand-Book  for  Estimating  the  Probable  Cost  of  American  Rail- 
way Construction  and  Equipment.  By  WILLIAM  J.  NicoLLS,  Civil 
Engineer.  Illustrated,  full  bound,  pocket-book  form  .  Scarce 

NORMANDY.— The  Commercial  Handbook  of  Chemical  An» 

alysis : 

Or  Practical  Instructions  for  the  Determination  of  the  Intrinsic  01 
Commercial  Value  of  Substances  used,  in  Manufactures,  in  Trades, 
and  in  the  Arts.  By  A.  NORMANDY.  New  Edition,  Enlarged,  and 
to  a  great  extent  rewritten.  By  HENRY  M.  NOAD,  Ph.D.,  F.R.S., 
thick  I2mo. Scarce 

N  ORRIS. — A  Handbook  for  Locomotive   Engineers  and  Ma 

chinists : 

Comprising  the  Proportions  and  Calculations  for  Constructing  Loco 
motives;  Manner  of  Setting  Valves;  Tables  of  Squares,  Cubes,  Areas, 
etc.,  etc.  By  SEFHMUS  NORRIS,  M.  E.  New  edition.  Illustrated, 
I2mo 

NYSTRGM. — A  New  Treatise  on  Elements  of  Mechanics : 
Establishing  Strict  Precision  in  the   Meaning  of  Dynamical  Terms  • 
accompanied  with  an  Appendix  on  Duodenal  Arithmetic  and  Me 
trology.     By  JOHN  W.  NYSTROM,  C.  E.     Illustrated.     8vo. 

NYSTROM. — On  Technological  Education  and  the  Construc- 
tion of  Ships  and  Screw  Propellers : 

For  Naval  and  Marine  Engineers.  By  JOHN  W.  NYSTROM,  lnt» 
Acting  Chief  Engineer,  U.  S.  N.  Second  edition,  revised,  with  addi 
tional  matter.  Illustrated  by  seven  engravings,  izmo.  .  $1.00 

O'NEILL. — A  Dictionary  of  Dyeing  and  Calico  Printing:       ^ 
Containing  a  brief  account  of  all  fhe  Substances  and  Processes1  v 
use  in  the  Art  of  Dyeing  and  Printing  Textile  Fabrics  ;  with  Practife 
Receipts  and  Scientific  Information.     By  CHARLEC  O'NEILL,  Anal/ 
deal  Chemist.     To  which  is  added  an  Essay  on  Coal  Tar  Colors  ami 
their  application  to  Dyeing  and  Calico  Printing.     By  A.  A.  FESQUET. 
Chemist  and  Engineer.     With  an   appendix  on  Dyeing  and  Calk'. 
Printing,  as  shown  at  the  Universal  Exposition,  Paris,   1867      8vo., 

49!  pages  .          .  #2.00 

ORTON. — Underground  Treasures-. 

How  and  Where  to  Find  Them.  A  Key  for  the  Ready  Determination 
of  all  the  Useful  Minerals  within  the  United  States.  By  JAMES 
•nixjN,  A.M.,  Late  Professor  of  Natural  H:stnry  in  Vassar  College, 
N.  Y.;  author  of  the  "  Andes  and  the  Amazon,"  etc.  A  New  Edi- 
tion, with  An  Appendix  on  Ore  Deposits  and  Testing  Minerals  (1901). 
Illustrated  .  .  .  .  .  .  .  .  £i.<;o 


HENRY    CAREY   BAIRD   &   CO.'S   CATALOGUE.        21 


OSBORN.— The  Prospector's  Field  Book  and  Guide. 

In  the  Search  For  and  the  Easy  Determination  of  Ores  and  Other 
Useful  Minerals.     By  Prof.  H.  S.  OSBORN,  LL.  D.     Illustrated  by  66 
Engravings.     Eighth  Edition.     Revised  and  Enlarged.     401  pages, 
I2mo.     1910.  ........         $1.50 

DSBORN — A  Practical  Manual  of  Minerals,  Mines  and  Min 

ing : 

Comprising  the  Physical  Properties,  Geologic  Positions,  Local  Occur 
rence  and   Associations  of  the  Useful  Minerals;  their  Methods  of 
Chemical  Analysis  and  Assay ;  together  with  Various  Systems  of  Ex- 
cavating and  Timbering,  Brick  and  Masonry  Work,  during  Driving, 
Lining,  Bracing  and  other  Operations,  etc.     By  Prof.  H.  S.  OSBORN, 
LL.  D.,  Author  of  "  The  Prospector's  Field- Book  and  Guide."     171 
engravings.     Second  Edition,  revised.     8vo.      .         .         .         $4.50 

OVERMAN.— The  Manufacture  of  Steel : 

Containing  the  Practice  and  Principles  of  Working  and  Making  Steel. 
A  Handbook  for  Blacksmiths  and  Worker*  in  Steel  and  Iron,  Wagon 
Makers,  Die  Sinkers,  Cutlers,  and  Manufacturers  of  Files  and  Hard- 
ware, of  Sl»'el  and    Iron,  and  for   Men   of  Science  and  Art.     By 
FREDERICK  OVERMAN,  Mining  Engineer,  Author  of  the  "  Manu- 
facture of  lion,"  etc.     A  new,  enlarged,  and  revised  Edition.     By 
A.  A.  FESQLdT,  Chemist  and  Engineer.     I2mo.         .         .         $1.50 
OVERMAN.  —The  Moulder's  and  Founder's  Pocket  Guide  : 
A  Treatise  or.  Mouldingnml  Founding  in  Green-sand,  Dry  sand , Loam, 
and  Cement;  the  Moulding  of  Machine  Frames,  Mill-gear,  Hollow 
ware,  Ornamerts,  Trinkets,  Bells,  and  Statues;  Description  of  Moulds 
for  Iron,  Brcnze,  Brass,  and  other  Metals;   Plaster  of  Paris,  Sulphur 
Wax,  etc. ;  the  Construction  of  Melting  Furnaces,  the  Melting  and 
Founding  of  Metals ;  the  Composition  of  Alloys  and  their  Nature, 
etc.,  etc.     By  FREDERICK  OVERMAN,  M.  E.     A  new  Edition,  tc 
which  is  addled  a  Supplement  on  Statuary  nnd  Ornamental  Moulding, 
Ordnance,  Malleable  Iron  Castings,  etc.     By  A.  A.  FESQUET,  Chem- 
ist and  Engineer.     Illustrated  by  44  engravings.     I2mo.    .        $2.OO 
PAINTER,  GILDER,  AND  VARNISHER'S  COMPANION. 
Comprising  the  Manufacture  and  Test  of  Pigments,  the  Arts  of  Paint- 
ing, Graining,  Marbling,  Staining,  Sign  writing,  Varnishing,  Glass- 
staining,  and   Gilding  on  Glass ;   together  with  Coach  Painting  and 
Varnishing,   and  the    Principles    of  the  Harmony  and  Contrast  of 
Colors.     Twenty-seventh  Edition.     Revised,  Enlarged,  and  in  great 
part  Rewritten.     By  WILLIAM  T.  BRANNT,  Editor  of  "  Varnishes, 
Lacquers,  Printing  Inks  and  Sealing  Waxes."      Illustrated.     395  pp. 

f2mo.       .  #1.50 

PALLETT. — The  Miller's,  Millwright's, and  Engineer's  Guide. 
By  HENRY  PALLKTT.     Illustrated.     i2mo.       .        .        .        £2.00 


92         riENRY  CARET   BAIRD  &  Co.'S  CATALOGUE. 

PERCY.— The  Manufacture  of  Russian  Shset-Iron. 

By  JOHN  PERCY,  M.  D.,  F.  R.  S.     Paper.       ...        25  ct& 
PERKINS.— Gas  and  Ventilation: 

Practical  Treatise  on  Gas  and  Ventilation.     Illustrated.     I2mo.    $1.25 
PERKINS  AND  STOWE.— A  New  Guide  to  the  Sheet-iron 

and  Boiler  Plate  Roller  : 

Containing  a  Series  of  Tables  showing  the  Weight  of  Slabs  and  Pia  * 
to  Produce  Boiler  Plates,  and  of  the  Weight  of  Piles  and  the  Sizes  of 
Bars  to  produce  Sheet-iron;  i':!ie  Thickness  of  the  Bar  Gauge 
in  decimals;  the  Weight  per  foe1:,  and  the  Thickness  on  the  Bar  or 
Wire  Gauge  of  the  fraction^'  parts  of  an  inch;  the  Weight  per 
sheet,  and  the  Thickness  r  A  the  Wire  Gauge  of  Sheet-iron  of  various 
dimensions  to  weigh  ii£  Ibs.  per  bundle;  and  the  conversion  of 
Short  Weight  into  Long  Weight,  and  Long  Weight  into  Short. 

$1-5° 

POSSELT. — Recent  Improvements  in  Textile  Machinery  Re- 
lating to  Weaving : 

Giving  the  Most  Modern  Points  on  the  Construction  of  all  Kindi 
of  Looms,  Warpers,  Beamers,  Slashers,  Winders,  Spoolers,  Reeds, 
Temples,  Shuttles,  Bobbins,  Heddles,  Heddle  Frames,  Pickers, 
Jacquards,  Card  Stampers;  Etc.,  Etc.  By  E.  A.  POSSELT.  4(0. 
Part  L,  6co  ills. ;  Part  II.,  6oc  ills.  Each  part  .  .  .  $3.00 

Part  III.,  615  ills £7.50 

POSSELT. — Technology  of  Textile  Design: 
The  Most  Complete  Treatise  on  the  Construction  and  Application- 
of  Weaves  for  all  Textile  Fabrics  and  the  Analysis  of  Cloth.     By  E. 
A.  Posselt.     1,500  illustrations.     410.        ....         $5.00 
POSSELT. — Textile  Calculations: 

A  Guide  to  Calculations   Relating  to  the  Manufacture  of  all  Kinds 
of  Yarns  and  Fabrics,  the  Analysis  of  Cloth,  Speed,  Power  and  Belt 
Calculations.     By  E.  A.  POSSELT.     Illustrated.    410.        .        $2.00 
REGNAULT. — Elements  of  Chemistry: 

By  M.  V.  REGNAULT.  Translated  from  the  French  by  T.  FORREST 
BETTON,  M.  D.,  and  edited,  v/ith  Notes,  by  JAMES  C.  BOOTH,  Melter 
and  Refiner  U.  S.  .Mint,  and  WILLIAM  L.  FABER,  Metallurgist  and 
Mining  Engineer.  Illustrated  by  nearly  700  wood-engravings.  Com- 
prising nearly  1,500  pages.  In  two  volumes,  8vo.,  cloth  .  £5'°° 
RICHARDS.— Aluminium : 

Its  History,  Occurrence,  Properties,  Metallurgy  and  Applications, 
including  its  Alloys.  By  JOSEPH  W.  RICHARDS,  A.  C.,  Chemist  and 
Practical  Metallurgist,  Member  of  the  Deutsche  Chemische  Gesell- 
schaft.  Illust.  Third  edition,  enlarged  and  revised  (1895)  .  $6.OO 
fclFFAULT,  VERGNAUD,.and  TOUSSAINT.— A  Practical 

Treatise  on  the  Manufacture  of  Colors  for  Painting  : 
Comprising  the  Origin,  Definition,  and  Classification  of  Colors;  the 
Treatment  of  the  Raw  Materials ;  the  best  Formulae  and  the  Newest 
Processes  for  the  Preparation  of  every  description  of  Pigment,  and 
the  Necessary  Apparatus  and  Directions  for  its  Use ;  Dryers ;  the 
Testing.  Application,  and  Qualities  of  Paints,  etc.,  etc.  By  MM. 
RIFFAULT,  VERGNAUD,  and  TOUSSAINT.  Revised  and  Edited  by  M 


HENRY  CAREY  BAIRD  &  CO.'S  CATALOGUE. 


F.  MALEPEYRK.    Translated  from  the  French,  by  A.  A 

Chemist  and  Engineer.     Illustrated  by  Eighty  engravings.     In  one 

vol.,  8vo.,  659  pages  •        $S'°° 

ROPER.  —  Catechism  for  Steam  Engineers  and  Electricians: 
Including   the    Construction  and  Management   of   Steam    Engines, 
Steam  Boilers  and  Electric  Plants.     By  STEPHEN  ROPER.     Twenty- 
first  edition,  rewritten  and   greatly  enlarged  by  E.  R.  KELLER  and 
C.  W.  PIKE.     365  pages.     Illustrations.     i8mo.,  tucks,  gilt.     $2.00 

ROPER.—  Engineer's  Handy  Book: 

Containing  Facts,  Formulae,  Tables  and  Questions  on  Power,  it* 
Generation,  Transmission  and  Measurement;  Heat,  Fuel,  and  Steam; 
The  Steam  Boiler  and  Accessories  ;  Steam  Engines  and  their  Parts  ; 
Steam  Engine  Indicator;  Gas  and  Gasoline  Engines;  Materials; 
their  Properties  and  Strength  ;  Together  with  a  Discussion  of  the  Fun- 
damental Experiments  in  Electricity,  and  an  Explanation  of  Dynamos, 
Motors,  Batteries,  etc.,  and  Rules  for  Calculating  Sizes  of  Wires.  Bf 
STEPHEN  ROPER.  I5ih  edition.  Revised  and  enlarged  by  E.  K. 
KELLER,  M.  E.  and  C.  W.  PIKE,  B.  S.  (1899),  with  numerous  illus- 
trations. Pocket-book  form  Leather.  .  .  .  ;~  „  -  $3.50 

ROPER.  —  Hand-Book  of  Land  and  Marine  Engines  : 
Including  the  Modelling,  Construction,   Running,  and  Management 
of  Lane3  and  Marine  Engines  and  Boilers.     With  frustrations.     By 
STEPHEN  ROPER,  Engineer.    Sixth  edition.     I2mo.,t\'cks,  gilt  edge. 

$3-50 
ROPER.—  Hand-Book  of  the  Locomotive  : 

Including  the  Construction  of  Engines  and  Boilers,  and  the  Construc- 
tion,   Management,    and    Running    of  Locomotives.     By    STEPHEN 
ROPER.     Eleventh  edition.     i8mo.,  tucks,  gilt  edge  .         $2.50 

ROPER.  —  Hand-Book  of  Modern  Steam  Fire-Engines. 
With  illustrations.     By  STEPHEN  ROPER,  Engineer.     Fourth  edition, 
I2mo.,  tucks,  gilt  edge       .....         .         .         $3-50 

ROPER.  —  Questions  and  Answers  for  Engineers. 
This  little  book  contains  all  the  Questions  that  Engineers  will  be 
asked  when  undergoing  an  Examination  for  the  purpose  of  procuring 
Licenses,  and  they  are  so  plain  that  any  Engineer  or  Fireman  of  or 
dinary  intelligence  may  commit  them  to  memory  in  a  short  time.     By 
STEPHEN  ROPER,  Engineer.     Third  edition        .         .         .         $2.00 
ROPER.  —  Use  and  Abuse  of  the  Steam  Boiler. 

By  STEPHEN   ROPER,  Engineer.     Eighth  edition,  with   frustrations. 
i8mo.,  tucks,  gilt  edge       .......         $2.00 

ROSE.  —  The  Complete  Practical  Machinist  : 

Embracing  Lnthe  Work,  Vise  Work,  Drills  and  Drilling,  Taps  and 
Dies,  Hardening  and  Tempering,  the  Making  and  Use  of  Tools 
Tool  Grinding,  Marking  out  Work,  Machine  Tools,  etc.  By  JOSHUA 
ROSE.  39  5  Engravings.  Nineteenth  Edition,  greatly  Enlarged  with 
New  and  Valuable  Matter.  I2mo.,  504  pages.  .  .  $2.50 
ROSE.  —  Mechanical  Drawing  Self-Taught  : 

Comprising  Instructions  in  the  Selection  and  Preparation  of  Drawing 
instruments,  Elementary  Instruction  in  Practical  Mechanical  Draw- 


*4         HENRY  CAREY  BAIRD  &  CO.'S  CATALOGUE. 

ing,  together  with  Examples  in  Simple  Geometry  and  Elementary 
Mechanism,  including  Screw  Threads,  Gear  Wheels,  Mechanical 
Motions,  Engines  and  Boilers.  By  JOSHUA  ROSE,  M.  E.  Illustrated 
by  330  engravings.  8vo,  313  pages  .  .  .  .  #3-5° 
ROSE.— The  Slide- Valve  Practically  Explained: 

Embracing  simple  and    complete   Practical   Demonstrations  of  th 
operation  of  each  element  in  a  Slide-valve  Movement,  and  illustrat- 
ing the  effects  of  Variations  in  their  Proportions  by  examples  care- 
fully  selected  from  the  most  recent  and  successful  practice.     By 
JOSHUA  ROSE,  M.  E.     Illustrated  by  35  engravings  .         $1.00 

ROSS. — The  Blowpipe  in  Chemistry,  Mineralogy  and  Geology : 

Containing  all  Known  Methods  of  Anhydrous  Analysis,  many  Work- 
ing Examples,  and  Instructions  for  Making  Apparatus.  By  LIEUT.- 
COLONEL  W.  A.  Ross,  R.  A.,  F.  G.  S.  With  120  Illustrations, 

I2mO.  .  ....'"      i          '         fc       .  .       : #2.0O 

8HAW.— Civil  Architecture : 

Being  a  Complete  Theoretical  and  Practical  System  of  Building,  con- 
taining the  Fundamental  Principles  of  the  Art.  By  EDWARD  SHAW, 
Architect.  To  which  is  added  a  Treatise  on  Gothic  Architecture,  etc. 
By  THOMAS  W.  SILLOWAY  and  GEORGE  M.  HARDING,  Architects. 
The  whole  illustrated  by  102  quarto  plates  finely  engraved  on  copper. 
Eleventh  edition.  4to.  .  .  .  .  .  .  #5-°° 

SHUNK. — A  Practical  Treatise  on  Railway  Curves  and  Loca 

tion,  for  Young  Engineers. 
By  W.  F.  SHUNK,  C.  E.    I2mo.    Full  bound  pocket-book  form  $2.oc 

8LATER. — The  Manual  of  Colors  and  Dye  Wares. 

By  J.  W.  SLATER.     i2mo #3.00 

SLOAN. — American  Houses  : 

A  variety  of  Original  Designs  for  Rural  Buildings.  Illustrated  by 
26  colored  engravings,  with  descriptive  references.  By  SAMUEL 

^SLOAN,  Architect.     8v©.  .75 

SLOAN.— Homestead  Architecture: 

Containi.:^  Forty  Designs  for  Villas,  Cottages,  and  Farm-houses,  with 
Essays  on  Style,  Construction,  Landscape  Gardening,  Furniture,  etc., 
etc.  JHustrated  by  upwards  of  200  engravings.  By  SAMUEL  SLOAN, 
Architect.  8vo #2.00 

BLOANE.— Ho^e  Experiments  in  Science. 

By  T.  O'CoNOR  SLCXNE,  E.  M.,  A.  M.,  Fh.  O.  Illustrated  by  91 
engravings.  I2mo. .  $l.oo 

SMEATON.— Builder's  Pockt^Companion : 

*  Containing  the  Elements  of  Building,  Surveying,  and  Architecture-, 
with  Practical  Rules  and  Instructions  corrected  with  the  subject. 
By  A.  C.  SMEATON,  Civil  Engineer,  etc.  I2mo. 

SMITH. — A  Manual  of  Political  Economy. 
By  E.  PESHINE  SMITH.     A  New  Edition,  to  which  is  added  a  full 
Index.     I2mo,          .  .....$£  2£ 


HENRY  CAREY  BAlRD  &  CO.'S  CATALOGUE.          25 


SMITH. — Parks  and  Pleasure-Giounds  : 

Or  Practical  Notes  on  Country  Residences,  Villas,  Public  Parks,  and 
Gardens.  By  CHARLES  H.  J.  SMITH,  Landscape  Gardener  and 
Garden  Architect,  etc.,  etc.  I2mo.  ....  $2.00 

SMITH.— The  Dyer's  Instructor: 

Comprising  Practical  Instructions  in  the  Art  of  Dyeing  Silk,  Cotton, 
Wool,  and  Worsted,  and  Woolen  Goods ;  containing  nearly  800 
Receipts.  To  which  is  added  a  Treatise  on  the  Art  of  Padding;  and 
the  Printing  of  Silk  Warps,  Skeins,  and  Handkerchiefs,  and  the 
v.irious  Mordants  and  Colors  for  the  different  styles  of  such  work. 
By  DAVID  SMITH,  Pattern  Dyer.  i2mo.  .  .  .  $1.00 

S  ^YTH. — A  Rudimentary  Treatise  on  Coal  and  Coal-Mining. 
By  WARRINGTON  W.  SMYTH,  M.  A.,  F.  R.  G.,  President  R.  G.  S, 
of  Cornwall.  Fifth  edition,  revised  and  corrected.  With  numer- 
ous illustrations.  I2mo.  $i»4O 

SNIVELY. — Tables  for  Systematic  Qualitative  Chemical  Anal. 

ysis. 
By  JOHN  H.  SNIVELY,  Phr.  D.     8vo.         ....        $1.00 

SNIVELY. — The  Elements  of  Systematic  Qualitative  v.hemical 

Analysis : 

A  Hand-book  for  Beginners.    By  JOHN  H.  SNIVELY,  Phr.  D.    i6mo. 

$2.00 

STOKES. — The  Cabinet  Maker  and  Upholsterer's  Companion-. 
Comprising  the  Art  of  Drawing,  as  applicable  to  Cabinet  Work; 
Veneering,  Inlaying,  and  Buhl- Work;  the  Art  of  Dyeing  and  Stain 
ing  Wood,  Ivory,  Bone,  Tortoise-Shell,  etc.  Directions  for  Lacker 
ing,  Japanning,  and  Vanishing;  to  make  French  Polish,  Glues 
Cements,  and  Compo?'.-'<is;  with  numerous  Receipts,  useful  to  work 
men  generally.  B'-  STOKES.  Illustrated.  A  New  Edition,  with 
an  Appendix  upor  /ench  Polishing,  Staining,  Imitating,  Varnishing, 
etc.,  etc.  I2mo $1.25 

STRENGTH  AND  OTHER  PROPERTIES  OF  METALS-, 

Reports  of  Experiments  on  the  Strength  and  other  Properties  of 
Metals  for  Cannon.  With  a  Description  of  the  Machines  for  Testing 
Metals,  and  of  the  Classification  of  Cannon  in  service.  By  Officer? 
of  the  Ordnance  Department,  U.  S.  Army.  By  authority  of  the  Secre 
taryof  War.  Illustrated  by  25  large  steel  plates.  Quarto  .  $5.00 

fiULLIVAN. — Protection  to  Native  Industry. 

By  Sir  EDWARD  SULLIVAN,  Baronet,  author  of  "  Ten  Chapters  on 
Social  Reforms."  8vo $1.00 

SHERRATT. — The  Elements  of  Hand-Railing  : 

Simplified  and  Explained  in  Concise  Problems  that  are  Easily  Under- 
stood. The  whole  illustrated  with  Thirty-eight  Accurate  and  Origi- 
nal Plates,  Founded  on  Geometrical  Principles,  and  Showing  how  to 
Make  Rail  Without  Centre  Joints,  Making  Better  Rail  of  the  Same 
Material,  with  Half  the  1  abor,  and  Showing  How  to  Lay  Out  Stairs 
of  all  Kinds.  By  R.  J.  SHEKRATT.  Folio.  .  .  .  $2.50 


26        HENRY  CAREY  BAIRL*  &  CO.'S  CATALOGUE. 


BYME. — Outlines  of  an  Industrial  Science 
By  DAVID  SYME.     I2mo.  .         .  ...         $2.00 

TABLES      SHOWING     THE     WEIGHT      OF     ROUND, 

SQUARE,  AND  FLAT  BAR  IRON,  STEEL,  ETC., 
By  Measurement.     Cloth  ......  6j 

THALLNER.— Tool-Steel : 

A  Concise  Handbook  on  Tool- Steel  in  General.  Its  Treatment  in 
the  Operations  of  Forging,  Annealing,  Hardening,  Tempering,  etc., 
and  the  Appliances  Therefor.  By  OTTO  THALLNER,  Manager  in 
Chief  of  the  Tool-Steel  Works,  Bismarckhutte,  Germany.  From  the 
German  by  WILLIAM  T.  BRANNT.  Illustrated  by  69  engravings, 
194  pages.  8vo.  1902. $2.oo> 

TEMPLETON.— The  Practical  Examinator  on  Steam  and  th* 

Steam -Engine: 

With  Instructive  References  relative  thereto,  arranged  for  the  Use  of 
Engineers,  Students,  and  others.  By  WILLIAM  TEMPLETON,  En. 
gineer.  I2mo.  .  .  ...  '  •  •  •  $1.00- 

THAUSING.— The  Theory  and  Practice  of  the  Preparation  of 

Malt  and  the  Fabrication  of  Beer : 

With  especial  reference  to  the  Vienna  Process  of  Brewing.  Elab- 
orated from  personal  experience  by  JULIUS  E.  THAUSING,  Professor 
at  the  School  for  Brewers,  and  at  the  Agricultural  Institute,  Modling, 
near  Vienna.  Translated  from  the  German  by  WILLIAM  T.  BRANNT» 
Thoroughly  and  elaborately  edited,  with  much  American  matter,  and 
according  to  the  latest  and  most  Scientific  Practice,  by  A.  SCHWARZ 
and  DR.  A.  H.  BAUER.  Illustrated  by  140  Engravings.  8vo.,  815 
pages  ..  .'.4  .-•  .,  ...  .....  $10.00 

THOMPSON. — Political  Economy.     With  Especial  Reference 

to  the  Industrial  History  of  Nations  : 

By  ROBERT  E.  THOMPSON,  M.  A.,  Professor  of  Social  Science  in  the 
University  of  Pennsylvania.  I2mo.  .  .  .  .  $1.50 

THOMSON.— Freight  Charges  Calculator: 
By  ANDREW  THOMSON,  Freight  Agent.     241110.        .        .        $1.25. 

TURNER'S  (THE)  COMPANION: 

Containing  Instructions  in  Concentric,  Elliptic,  and  Eccentric  Turn. 
hig;  also  various  Plates  of  Chucks,  Tools,  and  Instruments;  and 
Directions  for  using  the  Eccentric  Cutter,  Drill,  Vertical  Cutter,  and 
Circular  Rest;  with  Patterns  and  Instructions  for  working  them, 
I2mo $l.oo 

TURNING :   Specimens  of  Fancy  Turning  Executed  on  the 

Hand  or  Foot- Lathe : 

With  Geometric,  Oval,  and  Eccentric  Chucks,  and  Elliptical  Cutting 
Frame.  By  an  Amateur.  Illustrated  by  30  exquisite  Photographs. 
4to. (Scarce.) 


HENRY  CAREY  BAIRB  &  CO.'S  CATALOGUE. 


VAILE. — Galvanized- Iron  Cornice -Worker's  Manual  : 
Containing  Instructions  in  Laying  out  the  Different  Mitres,  and 
Making  Patterns  for  all  kinds  of  Plain  and  Circular  Work.  Also, 
Tables  of  Weights,  Areas  and  Circumferences  of  Circles,  and  other 
Matter  calculated  to  Benefit  the  Trade.  By  CHARLES  A.  VAILE. 
Illustrated  by  twenty-one  plates.  4to.  .  -  .  .(Scarce.) 

VILLE.— On  Artifici     Manures  : 

Their  Chemical  SelecLon  and  Scientific  Application  to  Agriculture. 
A  series  of  Lectures  given  at  the  Experimental  Farm  at  Vincennes, 
during  1867  and  1874-75,  By  M.  GEORGES  VILLE.  Translated  and 
Edited  by  WILLIAM  CTJOOKES,  F.  R.  S.  Illustrated  by  thirty-one 
engravings.  8vo.,  450  pag  - : $6.00 

VILLE. — The  School  of  Chemical  Manures  : 
Or,  Elementary  Principles  in  the  Use  of  Fertilizing  Agents.     From 
the  French  of  M.  GEO.  VILLE,  by  A.  A.  FESQUET,  Chemist  and  En- 
gineer.    With  Illustrations.     I2mo.  ....         $1.2$ 

VOGDES. — The  Architect's  and  Builder's  Pocket- Companion 
and  Price-Book  : 

Consisting  of  a  Shoit  but  Comprehensive  Epitome  of  Decimals,  Duo- 
decimals, Geometry  and  Mensuration  ;  with  Tables  of  United  States 
Measures,  Sizes,  Weights,  Strengths,  etc.,  of  Iron,  Wood,  Stone, 
Brick,  Cement  and  Concretes,  Quantities  of  Materials  in  given  Sizes 
and  Dimensions  of  Wood,  Brick  and  Stone;  and  full  and  complete 
Bills  of  Prices  for  Carpenter's  Work  and  Painting ;  also,  Rules  for 
Computing  and  Valuing  Brick  and  Brick  W7ork,  Stone  Work,  Paint- 
big,  Plastering,  with  a  Vocabulary  of  Technical  Terms,  etc.  By 
FRANK  W.  VOGDES,  Architect,  Indianapolis,  Ind.  Enlarged,  revised, 
and  corrected.  In  one  volume,  368  pages,  full-bound,  pocket-book 

form,  gilt  edges $2.OC 

Cloth        .  1.59 

VAN  CLEVE.— VAc;  English  and  American  Mechanic: 
Comprising  a  Collection  of  Over  Three  Thousand  Receipts,  Rules, 
and  Tables,  designed  for  the  Us?  of  every  Mechanic  and  Manufac- 
turer. By  B.  FRANK  VAN  CLEVE.  Illustrated.    500  r,.-,.  12010.  $2.cx 
VAN  DER  BURG.— £?hool  of  Painting  for  the  Imitation  of 

Woods  and  Marbles : 

A  Complete,  Practical  Treatise  on  the  Art  and  Craft  of  Graining  and 
Marbling  with  the  Tools  and  Appliances.  36  plates.  Folio,  12  x  20 

inches #6.00 

WAHNSCHAFFE.— A  Guide  to  the  Scientific  Examinatioe 

of  Soils: 

Comprising  Select  Methods  of  Mechanical  and  Chemical  A  lalysi' 
and  Physical  Investigation.  Translated  from  the  German  of  Dr.  F 
WAHNSCHAFFE.  With  additions  by  WILLIAM  T.  BRANNT.  Illus- 
trated by  25  engravings.  121110.  177  pages  .  .  .  $I-S& 
WALTON.— Coal-Mining  Described  and  Illustrated  : 
By  THOMAS  H.  WALTON,  Mining  Engineer.  Illustrated  by  24  ?arg> 
and  elaborate  Plates,  after  Actual  Workings  and  Apparatus.  52.00 


2$          HENRY  CAREY   BAIRD  &  CO.'S  CATALOC  UBU 

WARE.— The  Sugar  Beet. 

Including  a  History  of  the  Beet  Sugar  Industry  in  Europe,  Varieties 
of  the  Sugar  Beet,  Examination,  Soils,  Tillage,  Seeds  and  Sowing 
Yield  and  Cost  of  Cultivation,  Harvesting,  Transportation,  Conserva 
tion,  Feeding  Qualities  of  the  Beet  and  of  the  Pulp,  etc.  By  LEWII 
S.  WARE,  C.  E.,  M.  E.  Illustrated  by  ninety  engravings.  8vo. 

$2.00 

ARN.— The  Sheet-Metal  Worker's  Instructor: 
P\>r  Zinc,  Sheet-Iron,  Copper,  and  Tin-Plate  Workers,  etc.  Contain- 
ing  a  selection  of  Geometrical  Problems ;  also,  Practical  and  Simple 
Rules  for  Describing  the  various  Patterns  required  in  the  different 
branches  of  the  above  Trades.  By  REUBEN  H.  WARN,  Practical 
Tin-Plate  Worker.  To  which  is  added  an  Appendix,  containing 
Instructions  for  Boiler-Making,  Mensuration  of  Surfaces  and  Solids, 
Rules  for  Calculating  the  Weights  of  different  Figures  of  Iron  and 
Steel,  Tables  of  the  Weights  of  Iron,  Steel,  etc.  Illustrated  by  thirty 
two  Plates  and  thirty-seven  Wood  Engravings.  8vo.  .  $2.00 

WARNER. — New  Theorems,  Tables,  and  Diagrams,  for  thf 
Computation  of  Earth-work : 

Designed  for  the  use  of  Engineers  in  Preliminary  and  Final  Estimates 
of  Students  in  Engineering,  and  of  Contractors  and  other  non-profes- 
sional Computers.  In  two  parts,  with  an  Appendix.  Part  I.  A  Prac- 
tical Treatise;  Part  II.  A  Theoretical  Treatise,  and  the  Appendix 
Containing  Notes  to  the  Rules  and  Examples  of  Part  I.;  Explana 
tions  of  the  Construction,  of  Scales,  Tables,  and  Diagrams,  and  z 
Treatise  upon  Equivalent  Square  Bases  and  Equivalent  Level  Heights 
By  JOHN  WARNER,  A.  M.,  Mining  and  Mechanical  Engineer,  Illus- 
t  -ated  by  14  Plates.  8vo.  .  .  .  .  .  .  $3.00 

WILSON. — Carpentry  and  Joinery  : 

Bj  JOHN  WILSON,  Lecturer  on  Building  Construction,  Carpentry  and 
Joinery,  etc.,  in  the  Manchester  Technical  School.  Third  Edition, 
with  65  full-page  plates,  in  flexible  cover,  oblong.  .  .  ( Scarce. ) 

WATSON.— A  Manual  of  the  Hand-Lathe  : 

Comprising  Concise  Directions  for  Working  Metals  of  all  kinds, 
Ivory,  Bone,  and  Precious  Woods  ;  Dyeing,  Coloring,  and  French 
Polishing  ;  Inlaying  by  Veneers,  and  various  methods  practised  to 
produce  Elaborate  work  with  Dispatch,  and  at  Small  Expense.  By 
EGBERT  P.  WATSON,  Author  of  "The  Modern  Practice  of  American 
Machinists  and  Engineers."  Illustrated  by  78  engravings.  $1.00 

WATSON.— The  Modern    Practice  of  American   Machinists 
and  Engineers  : 

Including  the  Construction,  Application,  and  Use  of  Drills,  Lathe 
Tools,  Cutters  for  Boring  Cylinders,  and  Hollow-work  generally,  with 
the  most  Economical  Speed  for  the  same  ;  the  Results  verified  by 
Actual  Practice  at  the  Lathe,  the  Vise,  and  on  the  floor.  Togethei 


HENRY   CAREY    BAIRD   &   CO.'S   CATALOGUE.         29 


with  Workshop  Management,  Economy  of  Manufacture,  the  Steam 
Engine,  Boilers,  Geys,  Belting,  etc.,  etc.  By  EGBERT  P.  WATSON. 
Illustrated  by  eighty ~*,ix  engravings.  I2mo.  .  .  .  $2.00 

WATT.— The  Art  of  Soap  Making  : 

A  Practical  Hand-Book  of  the  Manufacture  of  Hard  and  Soft  Soaps, 
Toilet  Soaps,  etc.  Fifth  Edition,  Revised,  to  which  is  added  an 
Appendix  on  Modern  Candle  Making.  By  ALEXANDER  WATT. 
111.  I2mo. $3.00 

WEATHERLY. — Treatise  on  the  Art  of  Boiling  Sugar,  Crys- 
tallizing, Lozenge  making,  Comfits,  Gum  Goods, 
And  other  processes  for  Confectionery,  including  Methods  for  Manu- 
facturing every  Description  of  Raw  and  Refined  Sugar  Goods.  A 
New  and  Enlarged  Edition,  with  an  Appendix  on  Cocoa,  Chocolate, 
Chocolate  Confections,  etc.  196  pages,  1 2mo.  (1903)  .  #1.50 

WILL.— Tables  of  Qualitative  Chemical  Analysis  r 

With  an  Introductory  Chapter  on  the  Course  of  Analysis.  By  Pro- 
fessor HEINRICH  WILL,  of  Giessen,  Germany.  Third  American, 
from  the  eleventh  German  edition.  Edited  by  CHARLES  F.  HIMES, 
Ph.  D.,  Professor  of  Natural  Science,  Dickinson  College,  Carlisle, 
Pa.  8vo $1.50 

WILLIAMS.— On  Heat  and  Steam  : 

Embracing  New  Views  of  Vaporization,  Condensation  and  Explo- 
sion. By  CHARLES  WYE  WILLIAMS,  A.  I.  C.  E.  Illustrated.  8vo. 

$2.00 

WILSON. — First  Principles  of  Political  Economy: 

With  Reference  to  Statesmanship  and  the  Progress  of  Civilization. 
By  Professor  W.  D.  WILSON,  of  the  Cornell  University.  A  new  and 
revised  edition.  I2tno $1.50 

WILSON. — The  Practical  Tool-Maker  and  Designer: 

A  Treatise  upon  the  Designing  of  Tools  and  Fixtures  for  Machine 
Tools  and  Metal  Working  Machinery,  Comprising  Modern  Examples 
of  Machines  with  Fundamental  Designs  for  Tools  for  the  Actual  Pro- 
duction of  the  work ;  Together  with  Special  Reference  to  a  Set  of 
Tools  for  Machining  the  Various  Parts  of  a  Bicycle.  Illustrated  by 
189  engravings.  1898.  .  .  .  .  .  .  $2.50 

CONTENTS  :  Introductory.  Chapter  I.  Modern  Tool  Room  and  Equipment. 
II.  Files,  Their  Use  and  Abuse.  III.  Steel  and  Tempering.  IV.  Making  Tigs. 
V.  Milling  Machine  Fixtures.  VI.  Tools  and  Fixtures  for  Screw  Machines.  VII. 
Broaching.  VIII.  Punches  and  Dies  for  Cutting  and  Drop  Press.  IX.  Tools  for 
Hollow-Ware.  X.  Embossing:  Metal,  Coin,  and  Stamped  Sheet-Metal  Orna- 
ments. XI.  Drop  Forging.  XII.  Solid  Drawn  Shells  or  Ferrules;  Cupping  or 
Cutting,  and  Drawing ;  Breaking  Down  Shells.  XIII.  Annealing,  Pickling,  and 
Cleaning,  XIV.  Tools  for  Draw  Bench.  XV.  Cutting  and  Assembling  Pieces 
by  Means  of  Ratchet  Dial  Plates  at  One  Operation.  XVI.  The  Header.  XVII. 
Tools  for  Fox  Lathe.  XVIII.  Suggestions  for  a  Set  of  Tools  for  Machining  the 
Various  Parts  of  a  Bicycle.  XIX.  The  Plater's  Dynamo.  XX.  Conclusion— 
With  a  Few  Random  Ideas.  Appendix.  Index. 

WOODS —Compound  Locomotives: 

By  ARTHUR  TANNATT  WOODS.  Second  edition,  revised  and  enlarged 
by  DAVID  LEONARD  BARNES,  A.  M.,  C.  E.  8vo.  330  pp. 


30        HENRY   CAREY   BAIRD   &   CO.'S  CATALOGUE. 


WOHLER.— A  Hand-Bookof  Mineral  Analysis: 

By  F.  WOHLER,  Professor  of  Chemistry  in  the  University  of  Gottin- 
gen.  Edited  by  HENRY  B.  NASON,  Professor  of  Chemistry  in  the 
Renssalaer  Polytechnic  Institute,  Troy,  New  York.  Illustrated. 
I2mo. 

WORSSAM.— On  Mechanical  Saws  : 

From  the  Transactions  of  the  Society  of  Engineers,  1869.  By  S.  W. 
WORSSAM,  JR.  Illustrated  by  eighteen  large  plates.  8vo.  $1.50 


RECENT   ADDITIONS. 

BRAN  NT.— Varnishes,  Lacquers,  Fiirating  Inks  and  Sealing- 

Waxes : 

Their  Raw  Materials  and  their  Manufacture,  to  which  is  added  the 
Art  of  Varnishing  and  Lacquering,  includingthe  Preparation  of  Put- 
ties and  of  Stains  for  Wood,  Ivory,  Bone,  Horn,  and  Leather.  By 
WILLIAM  T.  BRANNT.  Illustrated  by  39  Engravings,  338  pages. 
I2mo. $3.00 

BRANNT.— The  Practical   Dry  Cleaner,  Scourer,  and   Gar- 
ment Dyer : 

Comprising  Dry  or  Chemical  Cleaning;  Purification  of  Benzine;  Re- 
moving Stains  or  Spotting;  Wet  Cleaning;  Finishing  Cleaned  Fabrics- 
Cleaning  and  Dyeing  Furs,  Skins, Rugs,  and  Mats;  Cleaning  and 
Dyeing  Feathers ;  Bleaching  and  Dyeing  Straw  Hats ;  Cleaning  and 
Dyeing  Gloves;  Garment  Dyeing;  Stripping;  Analysis  of  Textile 
Fabrics.  Edited  by  WILLIAM  T.  BRANNT,  Editor  of  "  The  Techno- 
Chemical  Receipt  Book."  Third  Edition,  Revised  and  Enlarged. 
Illustrated  by  Twenty-Three  Engravings $2  50 

BRANNT.— Petroleum . 

its  History,  Origin,  Occurrence,  Production,  Physical  and  Chemical 
Constitution,  Technology,  Examination  and  Uses;  Together  with 
the  Occurrence  and  Uses  of  Natural  Gas.  Edited  chiefly  from  the 
German  of  Prof.  Hans  Hosier  and  Dr.  Alexander  Veith,  by  WM. 
T.  BRANNT.  Illustrated  by  %  Plates  and  284  Engravings.  743  po. 
8vo.  $12.50 

BRANNT. — A  Practical  Treatise  on  the  Manufacture  of  Vine- 
gar and  Acetates,  Cider,  and  Fruit- Wines  : 
Preservation  of  Fruits  and  Vegetables  by  Canning  and  Evaporation; 
Preparation  of  Fruit-Butters,  Jellies,  Marmalades,  Catchups,  Pickles, 
Mustards,  etc.  Edited  from  various  sources.  By  WILLIAM  T. 
BRANNT.  Illustrated  by  79  Engravings.  479  pp.  8vo.  $6.00 

BRANNT.— The  Metal  Worker's    Handy-Book    of  Receipts 

and  Processes : 

Being  a  Collection  of  Chemical  Formulas  and  Practical  Manipula- 
tions for  the  working  of  all  Metals ;  including  the  Decoration  and 
Beautifying  of  Articles  Manufactured  therefrom,  as  well  as  their 
Preservation.  Edited  from  various  sources.  By  WILLIAM  T. 
BRANNT.  lllustrattd.  lamo.  1 2.50 


HENRY  CAREY  BAIRD  &  CO.'S  CATALOGUE.         31 

DEITE. — A  Practical  Treatise  on  the  Manufacture  of  Per- 
fumery : 

Comprising  directions  for  making  all  Kinds  of  Perfumes,  Sachet 
Powders,  Fumigating  Materials,  Dentifrices,  Cosmetics,  etc.,  with  a 
full  account  of  the  Volatile  Oils,  Balsams,  Resins,  and  other  Natural 
and  Artificial  Perfume-substances,  including  the  Manufacture  of 
Fruit  Ethers,  and  tests  of  their  purity.  By  Dr.  C.  DEITE.  assisted 
by  L.  BORCHERT,  F.  EICHBAUM,  E.  KUGLER,  H.  TOEFFNER,  and 
other  experts.  From  the  German,  by  WM.  T.  BRANNT.  28  Engrav- 
ings. 358  page's.  8vo. $3-oo 

EDWARDS. — American    Marine  Engineer,    Theoretical   and 

Practical : 

With  Examples  of  the  latest  and  most  approved  American  Practice. 
By  EMORY  EDWARDS.  85  illustrations.  I2mo.  .  .  $1.50 

EDWARDS.— 900    Examination   Questions  and   Answers: 

For  Engineers  and  Firemen  (Land  and  Marine)  who  desire  to  ob- 
tain a  United  *States  Government  or  State  License.  Pocket-book 

form,  gilt  edge          .  $1.50 

FLEMMING. — Practical  Tanning: 

A  Handbook  of  Modern  Processes,  Receipts,  and  Suggestions  for  the 
Treatment  of  Hides,  Skins,  and  Pelts  of  Every  Description.  By  LEWIS 
A.  FLEMMING,  American  Tanner.  630  pp.  8vo.  1910.  Net  $6.00 

POSSELT. — The  Jacquard  Machine  Analysed  and  Explained: 
With  an  Appendix  on  the  Preparation  of  Jacquard  Cards,  and 
Practical  Hints  to  Learners  of  Jacquard  Designing.  By  E.  A. 
POSSELT.  With  230  illustrations  and  numerous  diagrams.  127  pp. 
4to #3-00 

POSSELT. — Recent   Improvements   in   Textile   Machinery, 

Part  III : 

Processes  Required  for  Converting  Wool,  Cotton,  Silk,  from  Fibre 
to  Finished  Fabric,  Covering  both  Woven  and  Knit  Goods  ;  Con- 
struction of  the  most  Modern  Improvements  in  Preparatory  Machin- 
ery, Carding,  Combing,  Drawing,  and  Spinning  Machinery,  Winding, 
Warping,  Slashing  Machinery  Looms,  Machinery  for  Knit  Goods, 
Dye  Stuffs,  Chemicals,  Soaps,  Latest  Improved  Accessories  Relat- 
ing to  Construction  and  Equipment  of  Modern  Textile  Manufactur- 
ing Plants.  By  E.  A.  POSSELT.  Completel-  Illustrated.  4to. 

#7-50 

RICH.— Artistic  Horse-Shoeing : 

A  Practical  and  Scientific  Treatise,  giving  Improved  Methods  of 
Shoeing,  with  Special  Directions  for  Shaping  Shoes  to  Cure  Different 
Diseases  of  the  Foot,  and  for  the  Correction  of  Faulty  Action  in 
Trotters.  By  GEORGE  E.  RICH.  62  Illustrations.  153  pages 
$2.00 


32       HENRY    CAREV   BAIRD  &  CO.'S  CATALOGUE 


RICHARDSON.  --Practical  Blacksmithing : 

A  Collection  of  Articles  Contributed  at  Different  Times  by  Skilled 
Workmen  to  the  columns  of  "  The  Blacksmith  and  Wheelwright," 
and  Covering  nearly  the  Whole  Range  of  Blacksmithing,  from  the 
Simplest  Job  of  Work  to  some  of  the  Most  Complex  Forgings. 
Compiled  and  Edited  by  M.  T.  RICHARDSON. 

Vol.1.  210  Illustrations.  224  pages.  I2mo.  ,  .  $1.00 
Vol.  II.  230  Illustrations.  262  pages.  I2mo.  ,  .  $1.00 
Vol.  III.  390  Illustrations.  307  pages.  I2mo.  ,  .  $1.00 
Vol.  IV.  226  Illustrations.  276  pages.  I2mo.  .  .  $1.00 

RICHARDSON^— The  Practical  Horseshoer: 
Being  a  Collection  of  Articles  on  Horseshoeing  in  all  its  Branche* 
which  have  appeared  from  time  to  time  in  the  columns  of  "  1  he 
Blacksmith  and  Wheelwright,"  etc.     Compiled  and  edited  by  M.  T. 
RICHARDSON.     174  illustrations.       .....        $1.00 

ROPER. — Instructions    and   Suggestions    for   Engineers  and 

Firemen : 
By  STEPHEN  ROPER,  Engineer.     i8mo.     Morocco        .        $2.00 

ROPER. — The  Steam  Boiler:  Its  Care  and  Management: 
By  STEPHEN  ROPER,  Engineer.     I2mo.,  tuck,  gilt  edges.        $2.00 

ROPER. — The  Young  Engineer's  Own  Book: 

Containing  an  Explanation  of  the  Principle  and  Theories  on  which 
the  Steam  Engine  as  a  Prime  Mover  is  Based.  By  STEPHEN  ROPER* 
Engineer..  1 60  illustrations,  363  pages.  i8mo.,  tuck  .  $2.50 

ROSE. — Modern  Steam- Engines: 

An  Elementary  Treatise  upon  the  Steam-Engine,  written  in  Plain 
language ;  for  Use  in  the  Workshop  as  well  as  in  the  Drawing  Office. 
Giving  Full  Explanations  of  the  Construction  of  Modern  Steam. 
Engines  :  Including  Diagrams  showing  their  Actual  operation.  To- 
gether with  Complete  but  Simple  Explanations  of  the  operations  of 
Various  Kinds  of  Valves,  Valve  Motions,  and  Link  Motions,  etc., 
thereby  Enabling  the  Ordinary  Engineer  to  clearly  Understand  the 
Principles  Involved  in  their  Construction  and  Use,  and  to  Plot  out 
their  Movements  upon  the  Drawing  Board.  By  JOSHUA  ROSE.  M.  E. 
Illustrated  by  422  engravings.  Revised.  358  pp. 

ROSE. — Steam  Boilers: 

A  Practical  Treatise  on  Boiler  Construction  and  Examination,  for  the 
Use  of  Practical  Boiler  Makers,  Boiler  Users,  and  Inspectors;  and 
embracing  in  plain  figures  all  the  calculations  necessary  in  Designing 
or  Classifying  Steam  Boilers.  By  JOSHUA  ROSE,  M.  E.  Illustrated 
by  73  engravings.  250  pages.  8vo $2.00 

SCHRIBER—  The  Complete  Carriage  and  Wagon  Painter: 
A  Concise  Compendium  of  the  Art  of  Painting  Carriages,  Wagons, 
and  Sleighs,  embracing  Full  Directions  in  all  the  Various  Branches, 
including  Lettering,  Scrolling,  Ornamenting,  Striping,  Varnishing, 
and  Coloring,  with  numerous  Recipes  for  Mixing  Colors.  73  Illus- 
trations. 177  pp.  I2mo