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A Handbook of the Production and Properties of Printing, Writing, and 
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CONTENTS. Introduction. Carbon and Carbonaceous Inks. Tannin Materials for 
Inks. Nature of Inks. Manufacture of Iron Gall Inks. Logwood, Vanadium, and 
Aniline Black Inks. Coloured Writing Inks. Examination o~f Writing Inks. Early 
Methods of Manufacture. Manufacture of Varnish Preparation and Incorporation of 
the Pigment. Coloured Printing Inks. Copying Inks Marking Inks. Safety Inks and 
Papers. Sympathetic Inks. Inks for Special Purposes Engdsh Patents. INDEX. 
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Thoroughly Revised, Enlarged, and in Part Re-written 
ABRIDGED CONTENTS. General Composition and Nature of Oils, Butters, Fats, and 
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A Text-booh on the Chemistry and Physics of Fermentative Changes. 


CONTENTS. Introduction. Definition of Ferment. Chemical Nature of Ferment. 
influence of External Factors on Ferments. Mode of Action. Physiological Action. 
Secretion of Ferments. Ferments and the Vital Processes. A. THE HYDROLYTIO 
FERMENTS : Proteolytic Ferments. Trypsin. Bacteriolytic and Hsemolytic. Proteo- 
lytic Vegetable Ferments. Coagulating Ferments. Saccharifying Ferments. Animal 
Diastases. Enzymes of the Disaccharides. Ferments which decompose Glucosides. 
Lactic Acid Fermentation. B. THE OXIDISING FERMENTS : Alcoholic Fermentation. 
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CONTENTS. Structure and Chemical Composition of Muscular Fibre. Structure 
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Meat Extracts and Flesh Peptones. Cooking of Flesh. Poisonous Flesh. Animal 
Parasites. Bacteriological. Ptomaines. INDEX. 

" A compilation wnicii will be most use.ui lor uic cia i u r whom it is intended." Afhenetum. 







Chemist to Messrs. Beaufoy <5r* Co., Manufacturers of Vinegar 
for nearly 200 years. 

With 5 Plates and 49 other Illustrations. 





[A I! Rights Reserved.} 

In recognition of numerous kindnesses over a 
period of many years, 

3bts JSoofc is Defctcatefc 

to the oldest firm in the Vinegar Industry, 



CONSIDERING the age of the vinegar industry in this 
country, it is strange that no book has yet been published 
dealing with the subject from the English point of view. 
This is partly due to the fact that until a comparatively 
recent date the manufacture of vinegar was regarded 
as a mysterious process, all details of which had to be 
jealously guarded, not only from the outside world, 
but also, as far as possible, from the workmen in the 
factory itself. Even at the present day this tradition 
of secrecy is not quite dead, although the general prin- 
ciples of the manufacture are now common property. 

The information in chemical dictionaries has been 
mainly derived from American, French, and German 
books, which in some respects are obsolete, and in any 
case do not embody the experience of writers acquainted 
with the conditions of acetification in England. 

At the request of the Publishers I have attempted to 
fill this gap, and have tried to make clear the scientific 
principles underlying each stage of the manufacture, 
and to indicate the lines upon which development of the 
industry is possible. 

In the analytical portion of the book I have assumed 
that the reader will have a general knowledge of analytical 


chemistry, and have omitted details to be found in any 
ordinary text-book. With regard to the interpretation 
of analytical results, I have laid stress on the present 
unsatisfactory state of the law, and have pointed out 
the difficulties which this uncertainty causes both to the 
manufacturer and to the public analyst. 

It gives me great pleasure to acknowledge the assistance 
I have had from various friends in writing the book, and 
in particular I would thank Messrs. Beaufoy & Co. and 
Major Hamilton Pott for allowing me to use historical 
and other material in their possession. 

I have also to acknowledge my indebtedness to Messrs. 
Pontifex & Co. for the loan of blocks illustrating 
machinery made by them. 

My best thanks are also due to Miss M. B. Elliott for 
the help she has given me in reading the proofs. 

C. A. M. 






Early Scientific Views : Vinegar in Alchemy and latro-Chemistry 
Domestic Manufacture Early Manufacturing 
Alegar Vinegar Manufacturers Legislation on Vinegf 
Proof Vinegar The Acetometer Trade Numbers of Vinegar, 1-19 


Early Theories of Acetification Liebig's Theory Pasteur's Views 
Nageli's Mechanical Theory Later Enzymic Theories 
The Enzyme of Vinegar Bacteria Oxidation and Reduction 
Processes, . . / .' * . . , . 20-31 


Mycoderma aceti Hanson's Three Species Zoogloeal Condition 
Involution Forms Other Acetic Bacteria Action of Light on 
Acetic Bacteria Use of Pure Cultures, . . . . 32-49 


Earlier Views Oxidation in Acetification Effects of Oxidation 
Acetaldehyde Acetal Ethyl Acetate Other Products- 
Oxidation of the Acetic Acid Oxidation effected by Platinum 
Black, . . . 60-56 




Radical Vinegar Acetous Acid Acetic Acid 'in the Pharma- 
copoeias Anhydrous Acetic Acid Glacial Acetic Acid 
MANUFACTURE OF ACETIC ACID from Verdigris from Spirit 
Vinegar from the Distillation of Wood Pyroligneous Acid 
Platinum Black Use of Ozone Ozone in Acetifiers Newton's 
Apparatus Properties of Acetic Acid, .... 57-76 


The Mash-Tun Mashing Machines Hot-Liquor Backs Process 
of Mashing Gelatinised Grain Addition of Sugar The 
Conversion Process Fermentation of the Wort Storing the 
Gyle, 77-97 


APPARATUS : The Slow Process Fielding The Orleans Process 
Claudon's Apparatus The Quick Process English Acetifiers. 
DISTRIBUTION OF THE GYLE : The Sparge The Tipping 
Trough Siphon Distributors Aeration Devices Wagen- 
mann's Graduator Luck's Acetifier Singer's Apparatus 
Bersch's Acetifier. ACETIFICATION IN PRACTICE : Aeration 
The Temperature Effects of Alcohol and Acetic Acid The 
Group System Disturbances due to Mother-of-Vinegar The 
Vinegar Eel The Vinegar Mite The Vinegar Fly, . . 98-128 


Filtration Clarification Action of Ferrocyanide Sterilisa- 
tion Storage Distillation Composition of the Residue in 
the Still, ... ...... 129-136 




DETERMINATION OF ACIDITY Automatic Supply Burette 
Standardisation of Alkali Solutions Salleron's Ac6timetre 
Otto's Acetometer Standards of Acidity Crude Pyroligneous 
Acid TOTAL SOLIDS Alkalinity of the Ash MINERAL ACIDS 
Detection Determination Combined Sulphuric Acid 
Methyl-acetol FORMIC ACID TOTAL NITROGEN Nitrogenous 
COLOURING MATTERS Measurement of Colour Intensity 
Lovibond's Tintometer Caramel Cochineal Archil MET- 
ALLIC IMPURITIES Iron Copper Lead Tin Arsenic 
Official Method of Testing for Arsenic, . . . . 137-170 


Interpretation of Results CHEMICAL STANDARDS Acetic Strength' 
Total Solids Original Solids Nitrogen and Phosphoric Acid 
Optical Standard MALT VINEGARS The Malt Vinegar 
Question Composition of Malt Vinegars Cider Vinegar 
Wine Vinegar Whey Vinegar Fruit and Herb Vinegars 
Date Vinegar Spirit Vinegars Essig-sprit Wood Vinegar 
Composition of Artificial Vinegars, . . . . .171-191 

APPENDIX I. Import Duties on Vinegar and Acetic Acid, . . 192-195 
APPENDIX II. French Duties on Vinegar, .... 196 

INDEX, .... . 197-201 


Frontispiece. " Sending-out " Warehouse Messrs. Beaufoy & Co.'s 
Works in 1812. 


1. Early Apparatus used for Distilling Vinegar, .... 3 

2. Excise List of Vinegar Brewers, 1763, 11 

3. Obsolete Excise Acetometer, . . . . . . .15 

4. Pasteur's Drawing of Mycoderma aceti, ..... 24 

5. Pasteur's Experiment illustrating the Absorption of Oxygen, . 26 

6. Bacterium aceti (after Hansen), ...... 33 

7. Bacterium Pasteurianum (after Hansen), ..... 33 

8. Bacterium Kutzingianum (after Hansen), ..... 34 

9. Bacterium Pasteurianum Zooglceal Formation, .... 34 

10. Morphological Changes of B. Pasteurianum, . . . .35 

11. Thread Formation of B. Pasteurianum t . . . . .36 

12. Transformation of B. Pasteurianum, .... . . .38 

13. B. Pasteurianum Residue of Swollen Threads, . . . .37 

14. B. Pasteurianum Conversion of Threads into Chains of Short Rods, 

to face page 38 

15. Filaments of B. aceti, . . . . . . .39 

16. B. aceti Unusual Forms, . " . . . . .40 

17. Apparatus for Distillation of Radical Vinegar, . . . . 63 

18. Newton's Patent Process, . . 71 

19. Obsolete Mash-Tun and Copper, 78 

20.- Section of Mash- Tun, 79 

21. The Sparge, 80 

22. Section of External Mashing Machine, . . . . .81 

23. Mash-Tun with Steel's Mashing Machine, . " . . . . 84 

24. Underback and Refrigerator, A.D. 1812, 90 

25. Vertical Refrigerator, 92 

26. Exterior of Fermenting Tuns, . . . . .to face page 93 

27. Horizontal Refrigerator, ........ 93 

28. Fermenting Tun with Cooling Coil and Parachute, ... 94 

29. Old Store Vats, 96 

30. Vinegar Field Filling the Casks, 99 

31. Vinegar Field Drawing-off, 100 



32. Manufacture of Wine Vinegar. Orleans Process, . . . 102 

33. Claudon's Acetifying Apparatus, ...... 104 

34. Section of a Modern Acetifier with Basket Work, . . . 107 

35. Sparge of an Acetifier (Bronner), ...... 108 

36. The Tipping Trough (Bronner), 109 

37. Combined Siphon and Sparge, 110 

38. Diagram showing Aeration of an Acetifier, . . . .111 

39. Aeration Device, . . . 112 

40. Aeration Tubes, 112 

41. Wagenmann's Graduator, . . . . . . .113 

42. Singer's Acetifier, 115 

43. Bersch's Acetifier, 115 

44. Vinegar Eels (Pasteur), 123 

45. Vinegar Eel, highly magnified (Pasteur), 124 

46. Vinegar Mite, 127 

47. Vinegar Mite, 127 

48. The Rape Shed, to face page 129 

49. Diagram of Sterilising Apparatus, . . . . . .134 

50. Vinegar Still, to face page 135 

51. Salleron's Acetimetre, ........ 138 

52. Lovibond's Tintometer, .159 

53. Arsenic Apparatus, . . . . . . . .167 




Early Scientific Views : Vinegar in Alchemy and latro-Chemistry Domestic 
Manufacture Early Manufacturing Processes Alegar Vinegar Manu- 
facturers Legislation on Vinegar Proof Vinegar The Acetometer 
Trade Numbers of Vinegar. 

Vinegar in Alchemy and Early Chemistry. Passing over 
various allusions in the Classics to Acetum, and the fable 
of its use by Hannibal to dissolve the Alps, we find that 
vinegar had its recognised place among the products 

of the alchemist, and was indicated by the symbols h-L 
and } , while for distilled vinegar the characters >$p and 
^8J were used. These symbols were retained after the 
transition of alchymy into what has been termed " iatro- 
chymistry," from its being mainly concerned with the 
action of different bodies upon the human system. The 
doctrines of the alchemists were discarded but slowly, 
and we find that even at the beginning of the eighteenth 
century all natural things were held to consist of the 
five principles Spirit, Oil, and Salt (which were active), 

and Water and Earth (which were passive). 



According to Lemery,* there were three sorts of liquors 
known as Spirit ; the Spirit of Animals, the Burning 
Spirit of Vegetables, and the Acid Spirit. The first was 
typified by Spirit of Hartshorn, the second by Spirit of 
Wine, while the last, as " the Spirit of Vinegar, Tartar, 
and Vitriol, is an Acid Essential Salt, dissolved and put 
in fusion by the fire, as I shall prove when I speak of 
Vinegar." f 

In discussing the nature of vinegar, Lemery remarks : 
" Wines like other Liquors that use to ferment do grow 
sowr by the Dissolution of their Tartar in a second fer- 
mentation. This Dissolution is commonly made, when 
upon the Wines going to decay, some of the more subtle 
Spirits are lost ; for the Tartar taking their Place, fixes 
the rest of the Spirits which remain in the Wine, so that 
they can act no longer. This Fixation is the Cause that 
when the Wine turns sowr, very little quantity of it is 
diminished, and very little Tartar is found in the Vessels 
wherein Vinegar is made. 

" To the End that Wine may quickly sowr, you must 
set the Vessel that contains it in some hot Place, and mix 
the Lees from Time to Time ; for this Tartar will easily 
dissolve when Heat comes to act upon it." . . . " The 
Acids (in Vinegar) continue a long Time ; but being 
moved and continually agitated by the Sulphurs which 
intangled them, they at last evaporate into the Air ; 
and so the strongest Vinegar by length of Time becomes 
almost insipid." 

The following passage is of interest, since it throws 

* A Course of Chymistry (4th English edition from llth French edition), 
1720, p. 6. 
t/6id., p. 404. 


light upon the term " radical " vinegar, which survived 
into the last century,* and also shows that a concentrated 
acetic acid was prepared from distilled vinegar by neutral- 
isation, concentration, and redistillation, as far back as 
the seventeenth century : " Some having dried and 
calcined the sweet Extract that remains at the bottom 
of the Cucurbit, after the Distillation of Vinegar, and 
having by Solution, Filtration, and Coagulation, separated 
from it an Alkali fixt Salt, much like to that which is 

. A portable furnace for distilling 

with a fire of sand. 

/. The ash-room and its door. 
g. hearth and its door. 

h. cucurbit. 

*. head. 

k. receiver. 

I. cucurbit apart. 

m. head apart. 

Fig. 1. Early Apparatus for Distilling Vinegar. 

drawn from Tartar, they mix it with Spirit of Vinegar, 
and distil and cohobate it divers Times, until, say they, 
the Spirit has carried off all the Salt, and then will needs 
have it called Spirit of Vinegar Alkalized, or Radical 
Spirit of Vinegar ; and they affirm that this being much 
more pure and entirely united with its proper Salt, is 
much the more powerful in dissolving Metals." 

In the directions given by Lemery for the distillation 

* See the Act of George III. of 1818, p. 12. 


of vinegar, the liquid is first evaporated in an earthenware 
basin on a hot- water bath, until a sixth part, " which is 
the plegmatic Part," is expelled. The remainder is then 
" poured into a glass or earthenware Cucurbit and dis- 
tilled in a strong Sand-heat, until there remains at Bottom 
nothing but a Substance like Honey/' 

" This Spirit of Vinegar," he adds, " is mixed in 
Cordial Potions to resist Putrefaction. It is mixed with 
Water, and this Oxycrate is used to stop Hemorrhagies 
taken inwardly, and to asswage Inflammations applied 

" Neither Vinegar, nor any other Acids are proper for 
melancholy Persons, because they mix the Humoures too 
much : They also turn those who take much of them 
lean ; for they give too great Consistency to the Blood, 
and do hinder the Chyle from distributing itself sufficiently 
through the Body to give Nourishment." 

Domestic Manufacture. Long before any vinegar maker 
was established in this country wine vinegar appears to 
have been imported from France. In that strange 
collection of domestic recipes handed down from genera- 
tion to generation in the Fairfax family, and published 
in facsimile by Weddell,* there is one relating to the 
preparation of " Sirrupp of Viniger " in handwriting which 
appears to belong to the time of Queen Elizabeth. In 
this recipe the principal constituent is " white wine 
viniger," and as no directions are given for making it, 
such as those for the brewing of beer and cowslip wine, 
the making of simples for warding off the plague and 
curing the bite of a mad dog, or the preparation of 
baths for melancholy, it seems fair to infer that vinegar 

* Arcana Fairfaxiana, 1890, 


was not made in that household at all events. Not 
until the eighteenth century (judging by the writing) 
do we find an entry in the index relating to the 
making of vinegar, and the recipe corresponding to 
this is not to be found in the body of the manu- 

The process of brewing home-made vinegar was pro- 
bably very similar to that described by Mackenzie,* 
in the following words : 

" To every gallon of water put a Ib. of coarse Lisbon 
sugar ; let the mixture be boiled and skimmed as long 
as any scum arises. Then let it be poured into proper 
vessels ; and when it is as cool as beer, when worked, 
let a warm toast rubbed over with yeast be put into it. 
Let it work about twenty-four hours, and then put it 
into an iron hooped cask, fixed either near a constant 
fire, or where the summer sun shines the greater part 
of the day ; in this situation it should not be closely 
stopped up ; but a tile or something similar should be 
laid on the bung hole, to keep out the dust and insects. 
At the end of about three months (sometimes less) it 
will be clear and fit for use, and may be bottled off. The 
longer it is kept after it is bottled, the better it will be. 
If the bottle containing the liquor is to be exposed to 
the sun's heat, the best time to begin making it is in the 
month of April." 

Early Manufacturing Processes. The earliest descrip- 
tion of a process of making vinegar appears to be that 
published in 1670 in the Transactions of the Royal Society 
under the heading : " The Way of Making Vinegar in 
Prance : Communicated to the Publisher by an In- 

* One Thousand Processes of Manufacture, 1828. 


genious Physician of that Nation, living at a Place where 
much of it is Made." * 

Since this account throws light upon the origin of 
terms used to this day in the English vinegar industry, 
and disposes of the claim that Boerhave originated 
the process here described, it deserves quotation at 
length : 

" They take two great Casks, within each of which 
they put at the bottom a Trevet, which must be one foot 
high and as large, as the largness of the Cask permits. 
Upon this Trevet they put Vine twiggs, whereon they 
lay a substance called Rape, with which they fill both 
vessels within half a foot from the top. This Rape is 
nothing else but the wood or stalks of the Clusters of 
Grapes. The Trevet and the Vine branches are put at 
the bottom of the Casks, only to keep the Rape from 
setting at the bottom. It is this Rape which alone heats 
and sowrs the Wine. The two Vessels being almost 
quite filled with the Rape, one of them is filled up with 
Wine, and the other only half full for the time ; and 
every day they draw by a Cock half the Wine that is 
in the full vessel, therewith quite to fill up the other, 
that is but half full ; observing enterchangeable turns of 
filling and unfilling the vessels. Ordinarily at the end 
of two or three days the half filled vessel begins to heat, 
and this heat augments for several dayes successively, 
continuing to do so till the Vinegar is perfectly made, 
and the workmen know that the Vinegar is made by the 
ceasing of the heat. In summer it is a work of fifteen 
dayes ; in winter it proceeds more slowly, and that 
according to the degree of Cold weather. The full vessel 

* Phil. Trans. Roy. Soc., 1670, vol. v., p. 2002. 


is quite open at the top, but a wooden cover is put on 
the vessel that is but half full. . 

' The Wine in changing, leaves a certain grease, which 
sticks partly to the sides of the Cask (and that they take 
care to do clean away), partly to the Rape, so that if 
they cleanse not the Rape from it almost every year 
once, the Wine turns into a whitish liquor, which is 
neither Wine nor Vinegar. In the Casks which have 
never served for this purpose before the Vinegar is 
made more slowly than in such that have been used 

" There is no other way of keeping the Rape that 
hath once served already than to drown it ; that is to 
say, to fill the vessel wherein it is with Wine or Vinegar/' 

The account given by Boerhave * of the French method 
of manufacturing vinegar is substantially the same as 
this version of 1670, and there seems to be little doubt 
but that many English manufacturers derived their 
information from one or other of these sources. 

Alegar. The English being a beer-drinking nation, 
it was to be expected that the development of the vinegar 
industry in this country should have come by way of 
beer rather than of wine. By analogy the product 
derived from beer became known as " alegar," which 
stood in the same relation to ale as vinegar to wine. 

Boorde f in the year 1542 refers to both products in 
his " dyetary," where he speaks of " Soure and Tarte 
Thynges as Venegre and Aleger." 

The distinction between the two products was pointed 

* A New Method of Chemistry by Boerhave. English translation by 
Peter Shaw, 1753, vol. ii., p. 129. 

[First Boke of Introduction of Knowledge (edn. of 1870), vol. xxxiv., p. 296. 


out by Cogan * in 1586, in a passage upon the making 
of vinegar, where he remarks : " Some make it of Ale 
onely . . . but that is rather Aliger than Viniger." 

The term " alegar " is still to be found in glossaries 
of local words, but is probably now practically as obsolete 
as is the old home-made product obtained by adding a 
" vinegar plant " to sour beer. 

The vinegar manufacturer evolved out of the brewer ; 
for the production of vinegar was the obvious way of dis- 
posing of sour beer whether in the household or the brewery. 

It is probable that the earliest English products were 
nothing more than ale partially converted into vinegar 
by long exposure to the air. Subsequently the French 
methods of manufacture were adopted and " wash " was 
specifically brewed for the purpose. 

Vinegar Manufacturers. In the Revenue Act of 
Charles II. (1673), the vinegar thus produced as a waste 
product in the " common breweries " was termed 
" Vinegar-Beer/' and had to pay a duty of sixpence per 
barrel (as against Is. 3d. duty upon six-shillings' beer). 

The date of the establishment of the first vinegar 
factory as distinct from the " common brew-house " 
is uncertain, but there was undoubtedly a " vinegar 
yard" in Castle Street, South wark, as far back as 1641.f 
This yard belonged to a man named Rush, " in whose 
family it remained a considerable and improving manu- 
factory until the year 1790, when it came into the hands 
of the present proprietors." J 

* Cogan, Haven Health. 

-^History and Antiquities in the Parish of St. Saviour, Southwark, 1795. 

Messrs. Pott & Co., who already had a vinegar yard in the same 
parish, established in 1720. Early in the present century the firm 
became amalgamated with Messrs. Beaufoy & Co. 


The only name in the Excise list of vinegar makers 
for 1764, which is still connected with the industry, is 
that of Beaufoy. 

Early in the eighteenth century Mark Beaufoy, a 
member of the Society of Friends, established vinegar 
works on the site of the old Cuper's Gardens on the 
Surrey side of Waterloo Bridge, and within a few years 
they had become the third in importance in London. 

Pennant,* writing in 1792, makes the following allusion 
to these works in his description of London : " There is 
a magnificence of business in this ocean of sweets and 
sours, that cannot fail exciting the greatest admiration, 
whether we consider the number of vessels or their 
size. The boasted tun of Heidelberg does not surpass 
these. On first entering the yard two rise before you, 
covered at the top with a thatched dome ; between them 
is a circular turret including a winding staircase, which 
brings you to their summits above twenty-four feet in 
diameter. One of these conservatories is full of sweet 
wine, and contains fifty-eight thousand one hundred and 
nine gallons of Winchester measure ; its superb associate 
is full of vinegar to the amount of fifty-six thousand seven 
hundred and ninety-nine gallons/' 

In 1812 the ground occupied by these works was re- 
quired for the southern approach to Waterloo Bridge, 
and the manufacture was transferred to its present site 
in South Lambeth. 

A Report of an Excise Commission which preceded 
the alteration of the method of collecting the duty upon 
vinegar showed that up to the year 1834 there were 
seventy-seven thousand dealers in vinegar in Great 

* London, 3rd edition, p. 34. 


Britain, every one of whom received twelve visits a year 
from the Excise officers. In this report it was also stated 
that about three million gallons of vinegar were brewed 
in Great Britain and Ireland, for more than half of which 
five firms in London were responsible. 

In the year 1844 there were forty-four vinegar makers 
(excluding manufacturers of acetic acid), and they 
produced in that year 2,828,043 gallons of proof vinegar, 
upon which a duty of 24,745 7s. 6d. was paid. In the 
following year there were 65, but by the year 1860 the 
number of vinegar makers had fallen again to about 
50, and they still produced about 3,000,000 gallons 

Considerable light is thrown upon the development 
of vinegar making in this country by a study of the 
successive Acts of Parliament. 

Legislation upon Vinegar. Although the legislation in 
connection with vinegar has been mainly concerned 
with the purposes of revenue, it yet at the same time 
gives many interesting details of the industry. In the 
year 1673, an Act of Parliament was passed (XII. 
Car. II. Cap. 24) imposing a duty of 6d. per gallon for 
every Barrel of Beer commonly called Vinegar-Beer 
brewed by any common Brewer in any common Brew- 
House, the work of inspection to be carried out by the 
" gagers " of beer, metheglyn, etc. Apparently the 
revenue suffered from the evading of this duty, for in 
the year 1696 (VII. and VIII. Wm. III. C. 30) a penalty 
of forty shillings was imposed for every barrel of vinegar 
concealed from the gaugers, or sent out of the works 
without due notice to the Excise officers. 

* Muspratt, Dictionary of Chemistry, 1860, p. 36. 



In the following reign, by an Act passed in 1710 (VIII. 
Anna, C. 7), the duty upon vinegar was increased to 

Fig. 2. Facsimile of Excise List of Vinegar Brewers, 1763. 

9d. per barrel, and remained at that rate throughout 
the w r hole of the following century. 


By the Act of VI. Geo. III. C. 14, it was enacted that 
cider and perry that had turned sour and become unfit 
for sale were to pay duty as vinegar; while in 1796 
(XXXVI. Geo. III. C. 72) vinegar-makers were not allowed 
to have a distillery upon the same premises. They were 
also, before obtaining a licence, obliged to declare whether 
they intended to make vinegar from malt or corn, or from 
molasses or sugar. 

In 1818 (LVIII. Geo. III. C. 65) the old duties were 
repealed, and a duty of 4d. per gallon levied upon vinegar, 
vinegar-beer, alegar, radical vinegar, verjuice, acetous 
acid, acetic acid, pyroligneous acid, and liquors intended 
for vinegar made in England and Ireland, and of Is. per 
gallon upon imported vinegar and acetic acid, with a 
drawback of 4d. per gallon for exported products upon 
which the duty had been paid. 

To prevent the introduction or sale of strong acetic 
acid upon which only the duty for " common vinegar " 
had been paid, it was enacted that " all such liquors 
shall be tried with such acetometer as may be devised 
by the Commissioners of Excise. If found above proof 
a proportional charge was to be made for the excess/' 
" Proof " vinegar was defined in this Act as that con- 
taining " such strength of Acetous Acid that 100 parts 
of the Liquor by Weight shall saturate or neutralize 
14J parts by weight of crystallized subcarbonate of 
soda." * 

No foreign acid was to be added to vinegar except 
sulphuric acid in a proportion not exceeding one 
thousandth part by weight (Sec. 25). 

Moreover, no person was allowed to make vinegar 

* This corresponded to 4'74 per cent, of the so-called "dry" acid. 


from malt or other fermentable matter at any place 
used for the preparation of acetous acid. 

The drawback allowed by this Act, for exported 
vinegar upon which the duty had been paid, was sub- 
sequently, in 1821 (I. and II. Geo. IV. C. 102), made 
proportional to the acetic strength as estimated by an 

Four years later (VI. Geo. IV. C. 37), the excise duty 
upon vinegar was again altered to 16s. 8d. for 100 gallons, 
and by VI. Geo. IV. C. 81, the licence for the manufacture 
of vinegar was fixed at 5 per annum. 

In the following reign two Acts concerning vinegar 
were passed. In 1833 (III. Gulielm. IV. C. 56) the 
customs duty was fixed at 18 18s. per tun, while in 
1836 (VI. and VII. Gulielm. IV. C. 65) the Act of George 
III. dealing with the collection of the excise duty was 
repealed so far as it concerned the retailers of vinegar. 
This change was made upon the report of Commissioners 
who estimated that the number of dealers and retailers 
was very large (see p. 9), and that the continual inspec- 
tion of the stock was expensive and unnecessary, since 
the duties might be much more readily collected from 
the manufacturers. 

In 1840 (III. Viet. C. 17) an additional charge of 5 per 
cent, upon the customs and excise duties upon vinegar 
was imposed, but four years later the excise duty upon 
vinegar was entirely abolished (VII. and VIII. Viet. 
C. 25), though a manufacturer's licence was still required, 
while the customs duty was fixed at 4 4s. per tun of 
proof vinegar or acetic acid (VII. Viet. C. 16). The 
licence for having a vinegar still or retort was fixed in 
1846 at ten shillings a year (IX. and X. Viet. C. 90). 


Proof Vinegar. With the repeal of the duties upon 
vinegar and acetic acid, the word " proof acid " became 
obsolete, and the acetometer, by which the strength 
was ascertained, became a curiosity of the past. The 

ee -p 

terms "proof/' ^-, and so on, still linger, however, in 

the vocabulary of the older workmen in vinegar and 
acetic acid works, while discarded acetometers may 
still survive here and there, although they have long 
since ceased to be made. 

Since, however, they have historical interest in the 
vinegar industry, a brief outline may be given of the 
method by which the revenue officers determined the 

The acetometer was a particular form of hydrometer, 
having a silver cup to receive weights at the top of its 
stem. These weights were added until the hydrometer 
sank in the liquid to a mark made upon the stem. The 
ucid or vinegar to be tested was first diluted with an 
equal volume of rain water, and neutralised by the 
addition of slaked lime introduced in slight excess. As 
considerable heat was produced by the neutralisation, 
the liquid was always cooled to 70 F. before testing. 
In the case of vinegars an extra weight marked M 
(" the mucilage weight ") was used to compensate for 
the solid matter, and the reckoning taken from the 
numbered weights subsequently used. The weight 

" 10" 
marked ^ indicated the strength of the " best vinegar " 

freed from solid matter (" mucilage "), and was the 
strength fixed by the Act of George III. as " proof acid." 
The 20 weight indicated twice that strength of vinegar, 


the 30 weight three times the strength, and so on up to 
80, which corresponded to 35 per cent, over proof, or the 
strongest acid upon which duty was charged by means 
of this instrument. There were also three intermediate 
weights, 8, 4, 2, and two fractional weights, 1 and J. 

Fig. 3. Obsolete Excise Acetometer. 

The specific gravity of the calcium acetate solution was 
approximately double that of the original acid. Thus, 
an acid of specific gravity 1 -009 showed 1 -018 in the acetate 
solution. Vinegar of the same strength would show about 
1-023, from which 0-005 would be deducted for the 
mucilage or extract. The proportions of acetic acid 


corresponding to the acetometer strengths were thus 
as follows : 

Acetometer, . \ 1 2 4 8 ^ 20 30 40 50 60 70 80 
' 25 ' 5 1 2 4 5 10 15 20 25 30 35 40 

As a matter of fact, the strength of " proof vinegar " 
was only approximately 5 per cent., the neutralisation 
value fixed by Act of Parliament corresponding to a 
vinegar containing 4-74 per cent, of " real " acetic acid 
(see pp. 12, 60). 

The estimations of the acidity made with this instru- 
ment were very rough, and the variations in the amounts 
of solid matter were so great in different vinegars that 
the allowance made for them by the " mucilage weight " 
could at best be only approximately correct. 

In Nicholson's Dictionary of Chemistry (2nd ed.), 1823, 
it is stated that Taylor's acetometer was based upon the 
following table : 


Sp. gr. 1-0085 contains real acid in 100, . . 5 

1*0170 . . 10 

1-0257 . 15 

1-0320 . 20 

1-0470 . 30 

1-0580 . 40 

" The acetic acid or radical vinegar of the apothecaries, 
in which they dissolve a little camphor or fragrant essen- 
tial oil, has a specific gravity of about 1 -070." 

Trade Numbers of Vinegar. As a rule, vinegar is not 


sold to the retailers in accordance with acetic strength, 
but is described by the numbers 16, 18, 20,- 22, and 24. 

The origin of these numbers has been attributed to 
the price in pence per gallon at which the vinegar was 
once sold, but even in 1842 it was stated * that " although 
the price no longer accords with these numbers, the num- 
bers themselves have been retained as symbols whereby a 
certain quality of vinegar may be known and designated/' 

This explanation is borne out by Phillips' Translation 
of the Pharmacopceia, for the year 1824, where it is stated 
that " the strongest vinegar is termed proof vinegar, 
and by the manufacturer called No. 24. It is estimated 
to contain 5 per cent, of real acetic acid, and the maker 
is allowed to mix one-thousandth of its weight of sul- 
phuric acid with it." 

On p. 18 of the same edition the writer makes it clear 
that by " real " acetic acid is meant what we now term 
acetic anhydride, but what was then regarded as the 
hypothetical " dry " acid, and he states that 50 grains 
of real acetic acid neutralise 153 grains of crystallised 
subcarbonate of soda (i.e., crystalline sodium carbonate). 
Calculated upon this basis, the proof vinegar of the Act, 
or No. 24 vinegar, contained 4-74 per cent, of " real " 
acetic acid, or 5-5 per cent, of acetic acid as is now under- 
stood by the term. 

The other explanation of the trade numbers is given 
by Muspratt,f who states that " proof vinegar has 
a specific gravity of 1-0085, and contains about 5 per 
cent, of acetic acid. In commerce this vinegar is 

* The Penny Magazine, 1842, p. 430. The same explanation is also 
given in Tomlinson's Cyclopedia of Useful Arts, 1854, p. 7. 
t Dictionary of Chemistry, 1860, p. 32. 



represented by No. 24, from the fact that 24 grains 
of pure dry carbonate of soda are required to neutralise 
a fluid ounce. Weaker vinegars are represented by the 
Nos. 18, 20, 22, according to their strength; and, as in 
the foregoing instance, these figures equal the number of 
grains of carbonate of soda that will saturate a fluid ounce." 

The chief objection to this explanation is that the 
strength of proof vinegar was estimated according to 
the Act of George III., not by means of anhydrous sodium 
carbonate, but by neutralisation with " crystallised 
carbonate of soda," which corresponded to the modern 
crystalline sodium carbonate (Na 2 C0 3 -f- 10H 2 0). Accord- 
ing to this, proof vinegar contained 4-74 per cent, of the 
hypothetical " dry " or " real " acetic acid, and not 
5-27 per cent., as would be required to comply with 
Muspratt's explanation. 

The statements in Phillips' Translation (supra) are 
conclusive upon the point, for they show that the term 
" No. 24 " was in use soon after the passing of the Act. 

On the basis of this latter explanation, which was 
accepted by many vinegar manufacturers, the " numbers " 
of the different vinegars would have the following strengths 
in terms of " real " or " dry " acetic acid and its corre- 
sponding modern equivalent acetic acid. 

Xumbev of Vinegar. 

" Dry " or "Real " Acetic 

Acetic Acid. 

Per cent. 

Per cent. 

















In practice there has been no uniformity upon this 
point among different manufacturers. No. 16 vinegar, 
for example, has been sold at strengths ranging from 
3-5 to 4-2 per cent., while No. 24 has usually contained 
from 5-5 to 6-0 per cent, of acetic acid, and has seldom 
been sold at a strength of 6-2 per cent. 

Some years ago a still weaker vinegar than No. 16 was 
known to the trade as " Diamond Vinegar," but since 
the recommendation of the Local Government Board as 
to the strength of vinegar, the sale of any vinegar 
weaker than 4 per cent, is liable to be followed by a 



Early Theories of Acetification Liebig's Theory Pasteur's Views 
Nageli's Mechanical Theory Later Enzymic Theories The Enzyme 
of Vinegar Bacteria Oxidation and Reduction Processes. 

Early Theories of Acetification. The conditions neces- 
sary for the successful acetification of alcoholic liquids 
were known empirically long before it was recognised 
that the oxidation of alcohol into acetic acid, as practised 
in vinegar works, was of a process analogous to the 
fermentation of sugar into alcohol. Various phenomena 
in the manufacture of vinegar were recorded, but not 
until the 19th century was well advanced was there any 
plausible attempt to explain their significance. 

For example, in 1822, Persoon made a microscopical 
study of the films that develop upon wine and beer when 
exposed to the air, and found them to be made up of 
cells resembling yeast cells. He gave to these pellicles 
the general name of Mycoderma (mucinous skin), but 
did not associate them with the development of 

Berzelius, in 1829, extended his theory of catalytic 
action to cover the function of the " mother of vinegar " 
in acetification, but attributed the fermentation not to 
any living cell or product of a living cell, but to the 


action of the acetic acid " enclosed within the pores " 
of the mucinous skin. 

Then in 1837 Kiitzing examined the skin, and described 
the small cellular structures, arranged in chains, of which 
it was composed. He recognised that these were living 
organisms, and regarded them as algae (Uvula aceti), by 
the vital activity of which alcohol was transformed into 
acetic acid. 

Liebig's Theory. In the year 1839 Liebig* published 
his theory of the nature of alcoholic fermentation, and 
extended it to cover also the fermentation of alcohol 
into acetic -acid. This theory had many points in common 
with that of Stahl (1697), for both looked upon the 
ferment as a body in a state of decomposition, and capable 
of imparting its motion to surrounding bodies. Liebig, 
however, included all processes of fermentation under 
ordinary chemical actions, and in support of his view 
that a small quantity of one substance could bring about 
changes in large quantities of other substances, cited 
phenomena such as the solution in nitric acid of platinum 
alloyed with silver, and the action of nitric oxide in the 
production of sulphuric acid. 4 

-In particular, the fact' that platinum black could 
promote the oxidation of alcohol to acetic acid was 
regarded by Liebig as a proof that the ferment in vinegar, 
" the mother of vinegar/' also acted purely by chemical 
means. The proteins composing it underwent decom- 
position and communicated their motion. 

Liebig subsequently modified his opinion to the extent 
that fermentations were caused by enzymes produced 
within the living ceDs, and that the physiological growth 
* J. prakt. Chem., 1., 35, 312. 


of the cells had nothing to do with the fermentation 
itself, but was merely the means by which the enzyme 
was developed.* 

In another place f he elaborates these views : 

" An atom or molecule put in motion by any power 
whatever may communicate its own motion to another 
atom in contact with it. 

" Hydrogen, from being in contact with decaying 
substances, acquires the power of combining with oxygen 
at the common temperature. 

" Other inflammable gases, both simple and com- 
pound, are affected under these circumstances in exactly 
the same manner as hydrogen. The vapour of alcohol, 
for example, when in a vessel containing wood or other 
substances in a state of decay, absorbs oxygen from the 
atmosphere, and becomes transformed into aldehyde, 
and subsequently into acetic acid, which, upon assuming 
a fluid state, is withdrawn from the further influence of 
the oxygen. 

"It is upon this power of substances undergoing 
decay to increase the attraction of all organic substances 
for oxygen, and especially the affinity of alcohol for this 
element that a speedy process for acidifying alcohol 
was based, which is termed the ' Schnellessig-fabrikation/ 
or ' quick vinegar process.' 

" The transformation of fermented liquors into vinegar 
formerly required weeks, and even months, to accomplish 
in consequence of the imperfect access of the air : we can 
now convert alcohol into vinegar in less than twenty- 
four hours ; and this is effected mainly by making brandy 

* Annalen der Chem. u. Pharm., 1870, cliii. 

f Liebig, Letters on Chemistry, London, 1851, p. 216. 


diluted with water, or any other weak spirituous liquor, 
trickle slowly through casks filled with wood shavings, 
and at the same time causing a slight stream of air to 
circulate through these shavings. 

" At the commencement of this process it is usual 
to add to the dilute spirit a small quantity of some sub- 
stance containing matter capable of undergoing the 
process of decay, such as beer wort, honey, vinegar, 
etc. ; but after the lapse of a very short time, the surface 
of the wood shavings passes into a state of oxidation, 
and from that moment effects the transformation of the 
spirit into vinegar without the further co-operation of 
extraneous decaying matter/' 

In a later paper * Liebig expressed the opinion that 
the mother-of-vinegar was not essential to acetic fer- 
mentation, but that its place could be taken by dead 
vegetable matter. "It is unquestionable/' he says, 
" that mother-of-vinegar is capable of effecting the 
oxidation of alcohol into acetic acid, but this action 
does not depend upon a physiological process. Alcohol 
requires for its conversion into acetic acid only oxygen, 
and thus the Mycoderma aceti cannot and does not give 
to it out of its own substance. The analysis of the air 
leaving the acetifiers shows that the oxygen required 
for the oxidation of the alcohol is taken from the air, 
and the only part that the mother-of-vinegar can take 
in this process is that of promoting this absorption ; it- 
is only active by virtue of this chemical process, and 
its place as a living plant can be taken by a large number 
of dead substances and parts of plants/' 

Pasteur's Views on Acetiflcation. The weight of Liebig's 

* Annalen der Chem. u. Pharm., cliii., 137. 


authority prevented the views of Kiitzing (supra) gaining 
much acceptance, and it was not until the year 1864 
when Pasteur's experiments confirmed the conclusions 
of Kiitzing, that the vitalistic theory of acetification 
began to prevail, and that the acetic fermentation was 
recognised as being inseparably connected with the 
presence of living organisms. 

fc V.* 

:*3fr :& - 

- Xi -s i|** 

? l rV*4 * V- 

'<- ,, - ' -K 'V 
1 * 


Fig. 4. Pasteur's Drawing of Mycoderma aceti. 

Pasteur observed many of the facts recorded by some 
of his predecessors, but he made also the first systematic 
study of the process of vinegar-making, and was the 
first to prove that no acetic fermentation could take 
place in the absence of the so-called fungus Mycoderma. 

Like Kiitzing, he found that this mycoderma was 
composed of distinct cells, and in a lecture given in 


1868 to the vinegar manufacturers of Orleans he illus- 
trated the structure of the " fungus " by the drawing 
here reproduced. 

He was the first to suggest that a distinction should 
be made between the pellicle forming upon fermenting 
wine and that upon souring wine, and that the name of 
Mycoderma vini should be given to the former, and that 
of Mycoderma aceti to the latter. 

For very many years these names were generally 
accepted, but the work of Hansen and others (infra) 
showed that the organisms composing " mother-of- 
vinegar " were in reality bacteria, and ought, therefore, 
to be distinguished from the yeasts which composed 
the pellicle of Mycoderma vini. In fact, Pasteur con- 
cluded that there were many reasons for regarding 
Mycoderma aceti as a parasite of Mycoderma vini. 

In his treatise upon the Fermentation of Vinegar,* 
Pasteur showed that the vinegar Mycoderma could be 
grown upon a neutral fluid containing alcohol, and that 
in its growth it absorbed oxygen from the air. 

The experimental apparatus by which he proved this 
fact is shown in the accompanying figure. 

As the pellicle developed upon the liquid in the flask 
the oxygen was slowly absorbed, and the mercury con- 
tained in the basin, L, gradually rose in the tube D E. 
Subsequently the gases remaining in the flask were 
withdrawn into the eudiometer F G H, while the amount 
of acetic acid produced was estimated by titration of 
the liquid. 

In answer to Liebig's assertion (p. 23), that the 
function of the Mycoderma was a purely chemical one, 

* Memoire sur la Fermentation Acetiqve, Paris, 1868. 


and that its place as a promoter of oxidation could be 
taken by dead vegetable matter, Pasteur replied that, 
while such a notion was conceivable, he was not concerned 
with this or that theory, but only with the fact that 
every fermentation of alcohol into acetic acid resulted 
in the spontaneous development of Mycoderma aceti in 
the liquid in the casks. It was, moreover, possible to 
keep beer yeast for many years in contact with ferment- 

Fig. 5. Pasteur's Experiment illustrating the Absorption of Oxygen. 

able fluids, and in communication with the air in fer- 
mentation vessels, without the slightest trace of vinegar 
being produced, so long as there were no indications 
of the appearance of Mycoderma aceti. 

Upon the question of the presence of a specific oxidising 
ferment as distinct from the vital processes in the living 
organism, Pasteur did not express any dogmatic opinion, 
although from the general trend of his arguments he 


appeared to have a strong leaning towards the view 
that both alcoholic and acetic fermentations were purely 
physiological processes inseparable from the li r e of the 
organisms effecting those fermentations, and he summed 
up his position in the matter by quoting the following 
words of Dumas * : " There are doubtless cases in which 
a secret agency of living organisms, such as, for example, 
those which are found in association with vinegar fer- 
mentation, is conceivable ; but so long as the ferments 
in question have not been separated from the rest of the 
materials and the phenomenon attributed to them de- 
monstrated, the doubt as to their actual existence must 

While recognising that the vinegar " fungus'' was not 
the same organism as the wine " fungus " or yeast, 
Pasteur did not agree with the view first put forward 
by Stack, f that the vinegar organism could be classified 
with the bacteria. 

Nageli's Mechanical Theory. In 1879 Nageli J put 
forward a mechanical theory to explain the nature of 
fermentation processes. According to this theory the 
molecular groups composing the protoplasm of an organ- 
ism inducing fermentation are in a state of molecular 
vibration. These vibrations it is able to communicate 
to other compounds with which it comes into contact, 
so as to produce also within their molecules specific 
vibrations which result in the destruction of the equili- 
brium and the formation of new compounds. 

A sharp distinction is drawn between fermentation 
and enzymic action, the enzymes being regarded as 

* Chimie Appliquee aux Arts, vi., 341 (1843). 

f Intellectual Observer, 1863.. J Theorie der Gcihrung, 1879. 


replaceable by chemical agents, whereas a ferment can- 
not exist apart from the living cell. It is only when work 
is to be done at some distance from the cell that the 
organism excretes an enzyme. 

Applying his theory to the acetic fermentation, Nageli 
suggested that the protoplasm of the acetic^ bacteria 
was in a condition of molecular vibration, and that the 
vibrations were imparted, in the first place, to the mole- 
cules of alcohol and oxygen that had penetrated into 
the bacterial cells, and were thence communicated to 
the molecules outside the cells. As soon as the vibrations 
reached a certain pitch of intensity the molecular equili- 
brium was destroyed, chemical reaction took place, and 
a new series of bodies in another phase of equilibrium 
was produced. Part of the acetic fermentation thus 
occurred within the cells of the bacteria, but the greater 
part took place in the surrounding medium. The fer- 
mentation was thus accomplished in two stages, the 
equilibrium of the molecules being first destroyed, and 
new compounds then formed under the influence of the 
forces set in motion by the communicated vibrations. 

Later Enzymic Theories. In the later modification of 
his theory (p. 23), Liebig adopted a position which 
receives experimental support from the discovery and 
isolation of the enzymes in yeast, and later in the acetic 
bacteria by Buchner. 

It has been seen that, in their earlier form at all events, 
Liebig's views were diametrically opposed to any such 
vitalistic theory as that suggested by Kutzing. 

According to Liebig, " mother-of- vinegar " was not 
a living organism, but consisted of structureless precipi- 
tated albuminous matter, which acted like platinum 


black by imparting to the oxygen and alcohol its vibra- 
tions, so that these entered into combination. 

Liebig's final position with regard to the question 
of enzymes was thus practically the same as that held 
by Traube * in 1858. Traube's hypothesis was that in 
each organism producing fermentation there was present 
an enzyme of definite chemical composition, which had 
the power of transferring oxygen from one part of a group 
of molecules to another. These enzymes were of two 
kinds viz., (1) reducing enzymes, which could transfer 
combined oxygen, as in alcoholic fermentation ; and 
(2) oxidising enzymes, which were capable of conveying 
free oxygen to other bodies, as in the fermentation of 
alcohol into acetic acid. Both groups of enzymes were 
assumed to act merely by conveying oxygen, and not 
by communicating their own vibrations to the ferment- 
able substances. 

This theory of specific enzymes in bodies inducing 
fermentation was subsequently developed by Hoppe- 
Seyler, who concluded that the living organisms produced 
the ferments required for the particular fermentation, 
but that these ferments or enzymes were exceedingly 
unstable bodies, which w^ere inseparable from the proto- 
plasm, and became inactive when the organism died. 

The Enzyme of Vinegar Bacteria. When Buchner f 
had succeeded in isolating the enzyme zymase from yeast, 
and in proving that it was possible to effect alcoholic 
fermentation by means of preparations entirely free from 
living cells, attempts were made to separate enzymes 
from various bacteria by similar methods of grinding 

* Theorie der Fermentwirkungen, Berlin, 1858. 
f B&r. d. Chem. Ges., xxx., 227, 1110. 


up the cells with quartz sand and kieselguhr, and sub- 
jecting the mass to hydraulic pressure. 

But in every instance the liquids expressed from 
acetic bacteria were inert, and incapable of effecting 
the oxidation of alcohol. It thus appeared as though 
the oxidising function of the bacteria were more inti- 
mately connected with the vital processes of the organ- 
isms than in the case of the alcohol-producing enzyme 
in yeast, and the failure of these early experiments to 
separate an oxidising enzyme confirmed the views of 
those who held that the acetic fermentation was purely 
a physiological process. It was only because the oxida- 
tion was an exothermic process of a specific character 
that there was any evidence for still regarding the acetic 
fermentation as being due to a definite enzyme. 

It was not until 1 906 that Buchner and Gaunt * suc- 
ceeded in demonstrating, by a totally different method, 
that such acetic enzymes really existed. The pellicles 
of " mother-of- vinegar " forming upon alcoholic liquids 
in course of acetification were freed from water by centri- 
fugal force, and the residual mass of bacteria was treated, 
while still moist, with acetone. The resulting fluid 
acetone preparations were stable and capable of oxidising 
alcohol. Any possibility of living cells was eliminated 
by adding a small amount of toluene. The preparations 
made from cultivations of bacteria grown at 10 to 22 C. 
were more active than those grown at 28 C. In the 
experimental fermentations the stable acetone prepara- 
tions were ground to a paste with 2 to 4 per cent, of 
alcohol and chalk and 4 per cent, of toluene, and the 
mixtures were exposed for three days to a current of 

* Annalen, 1906, cccxlix., 140. 


air at 28 C. As a rule, not more than 0-5 to 2 per cent, 
of acetic acid was obtained, the maximum yield being 
4 per cent. 

The preparations also possessed the same property as 
the living bacteria of oxidising propyl alcohol to pro- 
pionic acid. From the results of these experiments there 
can be no reason for doubting that acetic bacteria owe 
their oxidising powers to the presence of one or more 

It has recently been found by Wieland * that the 
enzyme thus prepared from Hansen's B. aceti may be used 
instead of palladium black as a catalytic agent for the con- 
version of alcohol into acetic acid, and that it is capable 
of effecting the change in the absence of free oxygen, 
provided that a substance such as quinone or methylene 
blue is present. The function of the oxygen in the methyl- 
ene blue is to absorb the liberated hydrogen, and thus 
prevent its combining with the palladium and rendering 
it inactive. In the light of these experiments, the enzymic 
process, which is usually regarded as one of oxidation, 
must be regarded as a dehydrogenation process. In 
fact, Wieland considers that he is justified in regarding 
all oxidations as due to dehydrogenation, and that there 
is in reality no essential difference between processes of 
reduction and of oxidation. 

* Ber. d. Chem. Qes., 1913, xlvi., 3327. 


Mycoderma aceti Hansen's Three Species Zoogloeal Condition In- 
volution Forms Other Acetic Bacteria Action of Light on Acetic 
Bacteria Use of Pure Cultures. 

The Mycoderma aceti. For many years after their 
discovery the small organisms that compose the struc- 
ture of " mother-of- vinegar " were regarded as mould 
fungi or yeasts, the superficial resemblances ' between 
the pellicle formed upon liquids in course of acetification 
and that formed upon wine by the yeast then termed 
Mycoderma vini lending support to this view. 

The suggestion of Stack (p. 27) that Mycoderma aceti 
was produced by bacteria was not accepted by Pasteur 
(1868), notwithstanding the fact that he states he had 
observed under the microscope indications of the multi- 
plication of the cells by fission.* One of the earliest 
authorities to recognise the nature of these micro-organ- 
isms was Cohn,f who in 1872 included them among the 

Hansen's Three Species. It was not until 1878, when 
Hansen J published the results of his investigation into 
the nature of the micro-organisms that cause beer to turn 

* Loc. tit., p. 63. 

fCohn, Beitrage zur Biologie der Pflanzen, ii., 127 (1872). 

J See Compt. Rend. Lab., Carlsberg, 1894, iii. ; 1900, v. 



sour, that it became known that the acetic fermentation 
might be brought about by several species of bacteria. 

Subsequently it was discovered by Lafar * that at 
least one species of budding fungi was capable of effecting 
the conversion of alcohol into acetic acid. 

The three species of acetic bacteria which were 
thoroughly studied by Hansen f were given the names of 
Bacterium aceti, B. Pasteurianum, and B. Kutzingianum, 
and they differ from each other in their form and their 
behaviour when grown upon an alcoholic culture-medium 
such as beer. 

Fig. 6. Bacterium aceti 
(after Hansen). 

Fig. 7. Bacterium Pasteurianum 
(after Hansen). 

Bacterium aceti, when grown in beer exposed to the 
air, at a temperature of about 34 C., speedily develops a 
moist smooth skin, in which are markings resembling veins. 

B. Pasteurianum also develops a pellicle within twenty- 
four hours, but the skin in this case is dry and has a 
corrugated appearance. 

* Compt. Rend. Lab., Carlsberg, 1894, p. 182. 
f Centrcitbl. Balder., 1893, xiii., 1864. 


B. Kiltzingianum forms a skin somewhat resembling 
that produced by B. aceti, but differing from it in the 
way in which it spreads upwards at the edges. It also 
causes turbidity in the liquid, after cooling, which is not 
the case with the other two species. 

The general appearance of the cells composing the 
pellicles formed by these three species is shown in Fig. 6. 

It will be noticed that the cells of B. aceti are smaller 
and narrower than those of the other two species, and 
that they form more compact chains than B. Pasteur- 
ianum. In the case of B. Kutzingianum isolated cells are 

Fig. 8. Bacterium Kutzingianum 
(after Hansen). 

Fig. 9. Bacterium Pastevrianum 
Zoogloeal Formation. 

the rule, and chain formations the exception. The con- 
stricted " figure-of-eight " forms observed by Pasteur is 
a frequent characteristic of the cells of B. Pasteur ianum. 

Zoogloeal Conditions. The curious pellicles formed by 
these and other acetic bacteria upon the surface of the 
liquid in which they develop are zooglceal forms produced 
by the swelling and cohesion of the walls of adjacent cells 
into a compact mucinous mass. 

When a portion of one of these pellicles is examined 
under the microscope, the structure of the mucinous 



layer between the cells is invisible, but when stained by 
Loffler's method the cells may be seen imbedded in their 
gelatinous envelope. 

An example of this is shown in Fig. 9, which represents 
a portion of the pellicle of B. Pasteur ianum stained in 
this manner. The three lowest spaces on the left show 
the mucinous membrane devoid of the bacterial cells, 

Fig. 10. Morphological Changes of jB. Pasteurianum. 

these having been crushed during the preparation of the 

The mucinous membrane of one of Hansen's three 
species, B. Kiitzingianum, when freshly grown upon a 
nutrient liquid, may be stained blue by a solution of 
iodine, and when now examined under the microscope 
the cells (stained yellow) will be seen enveloped in a blue 
medium. In the case of the other two species the cells 


are stained yellow by the iodine, but the mutinous 
membrane remains colourless. 

Involution Forms of Acetic Bacteria. A remarkable 

Fig. 11. Thread Formation of B. Pasteurianum. 

property, which appears to be common to all the species 
of acetic bacteria, is that of changing its form under the 
influence of temperature. The discovery and investiga- 



tion of this phenomenon by Hansen* formed part of a 
research which has now become a classic. 

Hansen found that when the cells of the bacteria, 

Fig. 12. Transformation of B. Pasteurianum. 

freshly grown at 34 C. (see Fig. 10), were transferred 
to a similar medium (a light beer), and maintained at a 

* Loc. cit. 


temperature of about 40 C., long rod-shaped forms were 
developed (Fig. 10), and these gradually extended into 
long threads, some of which attained a length of 200 /u. 
(Fig. 11). 

On now exposing these filaments to the initial tem- 
perature of 34 C. they began, after a few hours, to pro- 
duce bulbous swellings in different places (Figs. 12, 14), and 
finally both the rods and the bulbous cells become split 
up into short rods (Fig. 13), leaving only the thick walls 
of the bulbous cell (d, Fig. 13) unchanged. 


Fig. 13. B. Pasteurianum Residue of Swollen Threads. 

On examining the culture after twenty-four hours, 
all signs of the long thread formation had disappeared 
and the bacteria had reverted to their original form of 
chains of cells (Figs. 10, 14). 

These morphological changes were thus mainly de- 
pendent upon the temperature of cultivation, although 
they were also influenced by the composition of the 

Fig. 14. B. Pasteurianum Conversion of Threads into Chains of Short Rods. 


culture medium and the age of the bacteria. Cells that 
were more than two days old formed the long filaments 
with much less readiness than quite young cells. 

Similar involution forms were observed in the case 

Fig. 15. Filaments of B. aceli. 


of the other two species discovered by Hansen. The 
filaments produced by B. aceti were thinner, and attained 
more than twice the length of those formed by B. Pasteur ~ 
ianum (see Fig. 15), while occasionally branchings were 
observed (Fig. 16). 

Fig. 16. B. aceti Unusual Forms. 

On the other hand, the filaments of B. Kutzingianum, 
were much shorter than those of the other two species. 
Hansen also recorded the occurrence of analogous for- 
mations, when other species of acetic bacteria, including 


those discovered by Zeidler,* were cultivated at higher 

Other Acetic Bacteria. A species of acetic bacteria 
quite distinct from those described by Hansen was 
isolated by A. J. Brown f from malt wort in course of 
acetification, while three new species were isolated by 
Henneberg J in 1897, and several more later. 

There is some reason for doubting whether all these 
species are really distinct or whether some are not merely 
involution forms of others due to variations in the culture 

Bacillus xylinus (Brown). The bacilli are non-motile 
rods 1 to 2 /x in length by 0-5 /x mean breadth, and under 
the influence of increased temperature form filaments 
10 to 30 /x long by 0-5 /m in breadth. They produce a 
tough, gelatinous pellicle, which may grow to several 
inches in thickness. At first this skin is transparent, 
but later becomes opaque and leathery. 

It is the zooglceal condition of this and allied species 
of bacteria which constitutes the so-called " vinegar 
plant," and the excessive development of which causes 
trouble in the working of the acetifiers in the factory. 

It was shown by Brown || that when the pellicle was 
freed from fat, etc., by extraction there remained a mass 
which gave the reactions of cellulose (solubility in ammoni- 
acal copper oxide, blue coloration with iodine and sul- 
phuric acid) and had a composition corresponding to 
the formula (C 6 H 10 5 ) M . 

* Centralbl.f. Bakt., 1896, ii. f Journ. Chem. Soc., 1886, xxxix., 432. 

J Die Deutsche Essig-industrie, 1898, ii., Nos. 14-15. 

Ibid., 1905, Nos. 49-51. 

\\Journ. Chem. Soc., 1886, xxx., 432 ; Proc. Chem. Soc., 1887, 87. 


Bacillus oxydans (Henneberg). This forms rods 2-4 to 
2-7 JUL in length by 0-8 to 1 /* in breadth, which frequently 
produce long undulating filaments. It forms a thin 
mucinous pellicle, which does not give a blue coloration 
with iodine. Apparently this bacillus is identical with 
the Bacterium aceti of Zopf . 

Bacillus acetosus (Henneberg). The bacilli are about 
1 fjL long by 0-5 yu in breadth, and form long filaments 
resembling those of B. Pasteurianus in appearance. 
They produce a very tough, adherent pellicle, which does 
not give a blue coloration with iodine. 

Bacillus acetigenus (Henneberg). This is distinguished 
from the preceding species by yielding a soft mucinous 
pellicle, which gives a blue coloration with iodine and 
contains cellulose. It is one of the species which effects 
the acetification in German vinegar works. 

Bacillus Orleanensis (Henneberg). This species is stated 
by Henneberg to effect rapid acetification. It forms 
a very tough skin, which subsequently when older 
becomes polished and closely resembles silk paper. The 
bacilli form small rods (1-5 to 2-5 //, by 0-4 to 0-5 /x), 
which frequently develop into long filaments. They 
will not grow at 8 C. or at 39 C., the optimum tempera- 
ture being 20 to 25 C. The pellicle does not give a blue 
coloration with iodine. 

Bacillus curvus (Henneberg). This species, in accord- 
ance with its name, has a pronounced tendency toward 
the formation of curved rods (1-6 to 4/x by 0-4 to 0-5 yu), 
which may occur singly or in chains. It only produces 
a very small quantity of pellicle, which may form small 1 
white patches on the surface of the liquid. 

Bacillus rancens (Beijerinck). A species of bacilli 


isolated by Beijerinck * from a beer vinegar had the 
property of inverting cane sugar. 

Several forms of bacteria were also separated by 
Perold f from sour wine, and termed B. aceti vini. He 
regarded them as quite distinct from other species that 
have been described. 

Bacillus Schiltzenbachii (Henneberg). This was found 
by Henneberg in the gyle of a vinegar brewery. It 
forms ovoid or elongated rods (1-6 to 2-4/x in length by 
0-3 to 0-4// in breadth), which may be isolated or in 
chains. When grown on a nutrient liquid it produces 
pellicles which are at first in patches, but afterwards 
coalesce, while a light powdery deposit forms at the 
bottom of the vessel. The pellicle does not give a blue 
coloration with iodine. 

Bacillus xylinoides (Henneberg). Another species, iso- 
lated by Henneberg in 1906 from vinegar " wash/' may 
produce either a thin, fairly tough pellicle, or a coarse 
mucinous skin resembling coagulated white of egg. The 
latter zoogloeal condition resembles the " vinegar plant " 
formed by B. xylinus, and, like the latter, gives the 
cellulose reaction with iodine and sulphuric acid. The 
other modification of the pellicle does not give this re- 
action. The bacilli are rods from 1-2 to 2 /x in length by 
0-5 to 0-8 p in breadth. They will not develop at 6 C., 
and only grow slightly at 15 C. Their optimum tem- 
perature is 28 C., and at 35 9 C. all growth stops. 

Bacillus vini acetati (Henneberg). As its name implies, 
this species was found in wine in course of acetification. 
It forms a tender pellicle, and at first causes the liquid 
to become turbid. The bacilli (1 to 2 /x long by 0-4/x 

* Centralbl /. BaU., 1898, iv. (2), 209. f Ibid., 1909, xxiv., 13. 


broad) only occasionally form filaments. Growth is 
feeble at 15 C. and at 36 C., and stops at 8 C. 

Effect of Light on Acetic Bacteria. Like all micro- 
organisms, the vitality of the acetic bacteria is reduced 
by sunlight, and this was recognised long before the 
nature of acetic fermentation was known. 

Thus, for example, in one of the earliest German 
technical treatises on the manufacture of vinegar,* a 
description is given of the method of fermentation in 
casks, which are termed Mutterfasser. This process in 
its essential details is the same as the Orleans method 
described in the Transactions of the Royal Society (see 
p. 6), but stress is laid upon the point that all daylight 
should be excluded from the room, as far as possible, and 
that even candle-light should only be used when abso- 
lutely necessary. 

Experiments upon a small scale made in 1891 by 
Giunti f showed that acetic fermentation was inhibited 
by the direct rays of the sun, and that even diffused 
daylight checked the development of the bacteria in 
those parts of the liquid that it could reach. These 
results were confirmed in 1891 by Tolomei,f who also 
extended the experiments to ascertain which of the 
rays affected the fermentation. Nine samples of the same 
white wine were placed in a series of flasks, one of which 
was of ordinary colourless glass, another being blackened, 
while the rest were coloured in accordance with the 
colours of the spectrum. After the lapse of 22 days the 
amounts of alcohol and acetic acid were estimated in 
each of the flasks, with the following results : 

* Juch, Die Kunst der Essig-Bereitung, Niirnberg, 1818. 
t Quoted by Franche, Fdbricant de Vinaigre, p. 37. 




00 ^i 


2 03 







p *? 

V C^l ^^ 





_ ^ 



00 ^* 



4< co o 




g 5 ? 





g 1 


<M T^ 









5? S 



^H 1O CO 



"-' ^ S 

T^ t> 


p-i o co 




f 1 r ( C5 



^ CO 




4^ * 



""3 ^ 


^ 'J 

_o* * M 


> .s 


t ! ! 


* , 3 , fi 

S T 

i ! I s ' 



These results are very striking. They show a steady 
increase in the amount of acetic acid formed from violet 
to red, and prove that the violet rays of light are those 
that are injurious to acetic fermentation. 

The precautions taken by the old vinegar makers to 
exclude daylight as far as possible have thus a scientific 
justification. When dealing with small casks, into the 
top o c which the vinegar was poured, such constant 
exposure of the bacteria to the light must have had an 
injurious effect upon their development and action. 

The experiments cited show that by placing windows 
of orange glass in the room the fermentation would have 
proceeded as weh 1 as in darkness. 

When " stoves " for the large English acetifiers, con- 
taining 3,000 to 4,000 gallons, were first erected, the 
tradition of darkness was maintained, but the conditions 
of acetification on such a large scale are quite different 
from those that obtain in acetification in small casks. 

Even when there is a top window, the amount of light 
that can find its way into the acetifiers through the 
small holes in the sides of the vats is quite negligible, 
and the author has proved by an experience of several 
years that it is possible to have sufficient light in the 
building without interfering in any way with the steady 
working of the acetifiers. 

Use of Pure Cultures of Acetic Bacteria. The isolation 
of the particular species of bacteria most suitable for the 
preparation of different kinds of vinegar, and their use 
as pure cultures for acetification, would probably give 
very satisfactory results in producing vinegars with 
different flavours, and for rapid working with different 
types of apparatus. 


For example, the bacteria (B. xylinus, etc.) which 
form the " vinegar plant " do not work satisfactorily 
in some of the Continental forms of apparatus, since 
the heavy gelatinous slime they produce soon tends 
to choke any fine openings, while, on the other hand, 
some of the other species work best at too low a tempera- 
ture to suit the large English acetifiers, which derive 
their heat from rapid auto-oxidation. 

This is, of course, assuming that the Continental 
species of bacteria would not, if grown for many gener- 
ations in malt wash under the conditions of the manu- 
facture in England, gradually assume the " slime-forming " 
capacity of B. xylinus. 

So far, very little work has been done to ascertain 
the effects of using pure species of the bacteria in cultures 
prepared upon lines similar to those first employed by 
Hansen in growing pure cultivations of yeast from a 
single cell. 

It was, however, shown some fifteen years ago that 
each individual species has the power of producing a 
vinegar of different quality and aroma from the same 

Thus Villon * describes the results of his experiments 
on this point in the following words : " We have dis- 
tinguished several varieties of Mycoderma aceti, and 
each of them has the property of producing a vinegar 
of characteristic flavour and aroma. 

" We have been able to make a selection from these 
varieties, in exactly the same way as has been done in 
the case of the yeasts of beer, wine, and cider. We have 

* Quoted by Franche, Manuel Pratique du Fabricant de Vinaiyre, 1901, 
p. 64. 


isolated three distinct varieties, which we term I., II., 
and III. 

" My coder ma, aceti No. I. produces an exquisite vinegar, 
which keeps well. It acetifies wine and vinegar less 
rapidly than the other two varieties, and also grows 
old more rapidly. 

" My coder ma aceti No. II. gives an ordinary vinegar 
of average keeping qualities. It acetifies more rapidly 
than the variety No. I., and keeps for an average length 
of time. It is the sort of most common occurrence in 
ordinary vinegar works. 

" Mycoderma aceti No. III. produces a turbid, flat 
vinegar, which keeps extremely badly. It acetifies more 
rapidly than the others in fact too rapidly, since it 
oxidises the substances that form the bouquet. 

" We are convinced that there are other varieties of 
Mycoderma aceti, but up to the present we have only 
been able to isolate these three from those which acetify 

" It would be advantageous to make use only of 
Mycoderma No. I., and to prevent the formation of No. II., 
and especially of No. III. We have isolated this variety 
No. I. from Burgundy wine of an alcoholic strength of 
exactly 9 per cent, in process of acetification at a tem- 
perature of 20 C. The wine was treated with 1 gramme 
of ammonium phosphate per litre. We then made a 
series of twenty cultivations in succession, the Mycoderma 
aceti not being left for longer than 24 hours in each new 
wine, which had previously been aerated in a current of 
oxygen and filtered through porous porcelain to remove 
foreign ferments. 

" We thus obtained a cultivation of Mycoderma which 


was pure, young, and very vigorous. It was with the 
plant thus cultivated that we inoculated the wine that 
was to be acetified on an industrial scale. The ferment 
was only suitable for two acetifications, after which it 
had to be replaced by a fresh pure culture. In this way 
a vinegar with an excellent flavour and remarkable 
aroma was obtained/' 

It is to be feared that too little stress is laid upon the 
aroma of the vinegar brewed in England to make the 
use of pure cultures of bacteria appreciated from this 
point of view. On the other hand, it is possible that by 
the use of cultures of special species the loss of acid 
during acetification might be materially reduced. 



Earlier Views Oxidation in Acetification Effects of Oxidation Acet- 
aldehyde Acetal Ethyl Acetate Other Products Oxidation of the 
Acetic Acid Oxidation effected by Platinum Black. 

Earlier Views. The part played by the air in the conver- 
sion of wine into vinegar was recognised in practice long 
before any attempt was made to explain the facts. 

In the year 1778 Macquer described in his Dictionaire 
de Chimie an experiment made by Becher, the results 
of which were supposed to show that wine was con- 
verted into stronger vinegar than usual when heated in 
a hermetically sealed flask i.e., without the assistance of 
the air. Some years later the Abbe R-ozier * proved that 
absorption of air took place in the course of acetification. 
He attached a bladder distended with air to a tube passing 
through the bung of a cask containing wine that was 
turning sour ; and he found that the more acid the wine 
became the more limp was the bladder. 

Oxidation in Acetifieation. Rozier did not draw any 
decisive deductions from this experiment, and it was 
left for Lavoisier f to show that it was not the whole of 
the air, but the oxygen contained in it, that was the 
active agent in acetification. 

* Dictionaire d' Agriculture, 1786, iv., 525. 
t Trait* de Chimie, 1793, i., 159. 


" The acetic fermentation," he wrote, " is nothing 
more than an acidification of the wine effected in the 
open air by absorption of oxygen." 

The nature of alcohol and acetic acid was not under- 
stood at that period, and hence Lavoisier made no sugges- 
tion as to how the absorbed oxygen acted during aceti- 

The theory put forward by Berthollet * to explain 
the effect of the absorption in Rozier's experiment was 
that the oxygen probably effected the decomposition 
of the vinous compound, by abstracting and combining 
with the hydrogen therein so as to form acetic acid, and 
it is interesting to note that this view has recently received 
support from the experiments of Wieland (p. 31) upon 
the behaviour of the vinegar enzyme in the absence of 
free oxygen. 

The next observations published upon the chemical 
process of acetification were those of de Saussure,f who 
claimed that he had found that during the acetic fer- 
mentation a volume of carbon dioxide equal to that of 
the absorbed oxygen was liberated, and that the aceti- 
fication of wine depended not upon a fixation of oxygen, 
but upon the withdrawal of carbon and its partial libera- 
tion in the form of carbonic acid. 

Effects of Oxidation, It was not until 1821 that 
definite proof of the nature of the oxidation process was 
brought. In that year E. Davy { discovered platinum 
black, and showed that when it was moistened and 
treated with spirits of wine it became white hot and 

* Statique Chimique, 1803, ii. (Appendix), 525. 

t Recherches Ckimiques sur la Vegetation, 1804, p. 143. 

$Schweigger'sJourn., 1821, i., 340. 


caused the alcohol to be oxidised to acetic acid without 
any carbon dioxide being formed. It was this observa- 
tion which suggested to Dobereiner * his equation of the 
oxidation of alcohol in the acetic fermentation 

C 4 H 6 2 + 40 = C 4 H 4 4 + 2(HO),t 
or translating this into modern formulae 

CH 3 CH 2 OH + 20 = CH 3 . COOH -j- H 2 0, 

and he confirmed this by quantitative experiments. 

In accordance with his results, Dobereiner explained 
the acetic fermentation as a simple process of oxidation t 
which was brought about through the agency of a body,, 
such as platinum black, capable of condensing and 
absorbing the oxygen, so as to bring it into close contact 
with the alcohol. 

Acetaldehyde. Dobereiner also described a " light 
oxygen ether," which he obtained by distilling alcohol 
with manganese dioxide and sulphuric acid. This sub- 
stance, which was impure aldehyde, was subsequently 
studied by Liebig, who gave it its name (Alcohol dehydrogen- 
atus), and showed that it was produced as an intermediate 
stage in the oxidation of alcohol to acetic acid. 

The course of the fermentation would thus take place 
in two stages, in the first of which the alcohol was oxidised 
to aldehyde 

C 2 H 6 + O = C 2 H 4 + H 2 0, 

while on further oxidation the aldehyde became acetic 

C 2 H 4 + = C 2 H 4 2 . 

* Ibid., viii., 321. f C = 6 ; = 8. 


This is now accepted as an approximate explanation of 
the main reactions that take place in the conversion of 
alcohol into acetic acid. 

The relative proportions of alcohol, acet aldehyde and 
acetic acid present at any given stage of the process 
will depend to a large extent upon the conditions of the 
fermentation. If too little air be supplied the secondary 
oxidation will not keep pace with the first oxidation, 
and a pronounced odour of acetaldehyde will be per- 
ceptible in the air issuing from the acetifiers. 

Acetal. Another intermediate product formed in the 
oxidation is acetal,. CH 3 . CH(OC 2 H 5 ) 2 , which is produced 
when a mixture of aldehyde and alcohol is heated to a 
temperature of about 100 C. 

CH 3 . COH + 2C 2 H 5 . OH = CH 3 . CH(OC 2 H 5 ) 2 , 

and is also formed in small quantity through the heat 
of the acetic fermentation. It is probable that Dober- 
einer's " light oxygen ether " (supra) was a mixture of 
acetal and acetaldehyde, and that his " heavy oxygen 
ether/' obtained in a later stage of the distillation, was 

It was shown by Kromer and Pinner * that acetal 
was slowly formed by keeping alcohol and acetaldehyde 
together for several months at the ordinary temperature. 

Ethyl Acetate. In addition to acetaldehyde and 
acetal, a small amount of ethyl acetate or acetic ether 
is always produced in the acetic fermentation through 
the combination of the alcohol with the acetic acid 

CH 3 . COOH + C 2 H 5 . OH = CH 3 . COOC 2 H 5 + H 2 0. 

*Jahresber. Chem., 1869, 502. 


In the manufacturing process this is also finally oxi- 
dised to acetic acid, so that the finished vinegar leaving 
the acetifiers will usually be quite free from this ester. 
Since, however, a trace of alcohol (about 0-5 per cent.) 
is usually left unoxidised, slow combination takes place 
subsequently between this alcohol and the acetic acid, 
and the aroma of stored vinegar is principally due to the 
formation of ethyl acetate. 

Other Products. Traces of other alcohols, esters, and 
acids are also formed in the acetic fermentation, their 
nature and quantity depending upon the character of 
the non-alcoholic constituents (sugars, dextrins, acids, 
etc.) in the alcoholic wash. For example, formic acid 
is found in wine- vinegars, succinic acid in grain vinegars, 
and fusel oils in spirit vinegars ; but although some of 
these compounds may influence the flavour of a vinegar, 
they are without practical importance in the fermenta- 
tion process. 

Boutroux * gave a description of the action of the 
acetic fermentation upon dextrose, and showed that 
gluconic acid was produced. His experiments were 
repeated by Brown, | who found that gluconic acid was 
the sole product of the action of B. aceti on dextrose. 
The bacteria were unable to hydrolyse cane sugar, but 
oxidised mannitol, with the formation of laevulose as the 
main product. 

Brown's f B. xylmus (" the Vinegar-Plant ") behaved 
in a similar way, but had also the property of forming 
cellulose from leevulose, which was not possessed by any 
other acetic bacteria then known (cf. p. 41). This 

* Cmnptes Send., 1880, 236. 
\Journ. Chem. Soc., 1886, xlix., 172. 


cellulose gave all the reactions of ordinary cellulose, and 
on hydrolysis yielded a dextro-rotatory sugar. 

In this connection mention may be made of the action 
of acetic bacteria upon other alcohols. Both B. aceti 
and B. xylinus (Brown)* are capable of oxidising propyl 
alcohol to propionic acid, but are unable to attack methyl 
or amyl alcohols. Glycerol is oxidised completely into 
carbon dioxide and water, with a small quantity of an 
unknown acid, while glycol is converted into glycollic 

CH 2 (OH)CH 2 (OH) + 2 = CH 2 (OH)COOH + H 2 O. 

Oxidation of the Acetic Acid. It has long been known 
that if vinegar was left too long in the acetifiers its strength 
gradually decreased, but it was left for Pasteur f to prove 
that this loss of acetic acid was bound up with the life 
of the micro-organisms. 

He showed that the " Mycoderma aceti " would develop 
upon a nutrient medium containing acetic acid but no 
alcohol, and that the air in the flask subsequently con- 
tained a large proportion of carbon dioxide but no oxygen, 
while the whole of the acetic acid had disappeared. 

He called attention to the analogy between this slow 
process of combustion and the respiration of living 
organisms, and concluded that in the absence of alcohol 
the micro-organisms were capable of transferring oxygen 
to the acetic acid and of converting its carbon into car- 
bonic acid. 

At the same time the phenomena are also susceptible 
of the explanation that the oxidation of the acetic acid 
is due to enzymic action carried beyond the process of 

* Ibid., 1887, 638. t Loc. tit., p. 94. 


the acetification of the alcohol, and that the carbon 
dioxide is not due to respiration of micro-organisms, but 
is a combustion process analogous to that effected by 
the excessive oxidation of alcohol by platinum black. 

Oxidations Effected by Platinum Black. The analogy 
between the oxidations effected by platinum black and 
acetic bacteria furnished Liebig with one of his principal 
weapons against the vitalistic theory of acetification. 
The differences between the two processes, however, were 
demonstrated in 1873 by von Knierem and A. Mayer,* 
who showed that the conditions were not in any way 
comparable, although the final products might be the 
same. For example, the acetic fermentation could not 
take place in the presence of more than 10 to 12 per cent, 
alcohol, whereas platinum black could effect the oxida- 
tion of alcohol of any strength. In the latter case the 
oxidation was promoted by increasing the temperature, 
whereas the acetic fermentation was inhibited by tem- 
peratures exceeding about 40 C. 

It was also pointed out by these chemists that the 
same analogies were to be observed between other fer- 
mentation processes and the hydrolytic decompositions 
effected by dilute acids. 

For example, the conversion of starch into sugars 
could be effected either by diastatic " fermentation " 
or by the action of dilute acids. Moreover, other chemical 
agents, such as chromic acid, could effect the oxidation 
of alcohol to acetic acid. 

* Landw. Versuchsstat., 1873, xvi., 305. 



Radical Vinegar Acetous Acid Acetic Acid in the Pharmacopoeias- 
Anhydrous Acetic Acid Glacial Acetic Acid MANUFACTURE OF 
ACETIC ACID from Verdigris from Spirit Vinegar from the Distil- 
lation of Wood Pyroligneous Acid from Acetate of Lime CHEMICAL 
PROCESSES OF OXIDATION Platinum Black Use of Ozone Ozone 
in Acetifiers Newton's Apparatus Properties of Acetic Acid. 

Radical Vinegar. Acetic acid, as the Latin origin of its 
name (acetum) indicates, is the acid of vinegar, from 
which it was first separated in a more concentrated form 
by fractional distillation, neutralisation with alkali, 
crystallisation, and redistillation of the salt with acid 
(see p. 3). 

The strongest acid thus obtained was known as alkalised 
vinegar, or radical vinegar, which Bailey's English 
Dictionary of 1747 defines as " the sharpest Part of 
Vinegar, which hath its Phlegm * drawn off." 

In the London Pharmacopoeias of 1721, 1746, and 
1788 ordinary distilled vinegar (containing about 6 per 
cent, of acetic acid) is described by that name (Acetum 
distillatum) , but this was changed in the Pharmacopoeia 
of 1809 to " acetic acid "' (Acidum aceticum), and to 
" dilute acetic acid " (Acidum aceticum dilutum) in the 
Pharmacopoeia of 1824. 

* Water. 


Acetous Acid. In the edition of 1788 the more con- 
centrated acid is termed " acetous acid " (Acidum 
acetosum) a name which constantly recurs in Acts of 
Parliament down to 1844, and survives in the term 
" acetous fermentation/' which is still used in the vinegar 
industry. This name was given to the acid derived from 
vinegar, because it was believed to contain one atom less 
oxygen in its molecule than acetic acid from wood, and 
the salts that it formed with alkalies and heavy metals 
were termed acetites, to distinguish them from acetates. 
The name originated with the French chemist Berthollet, 
who in 1785 published a paper to prove that the acid 
obtained by distillation of verdigris differed in its pro- 
perties from the acetous acid derived from vinegar. He 
regarded the acid derived from the salt as a compound of 
acetous acid with oxygen. 

Even as late as 1806, we find the first edition of the 
Encylopcedia Britannica referring to " acetous acid in 
that concentrated state in which it is called radical 

In 1808 Henry * remarks, with reference to this question, 
" It appears that acetic acid differs only from the acetous 
in containing less water and more mucilage/' 

Acetic Acid in the Pharmacopoeias. It was probably 
owing to this proof of identity that the name of " acetic 
acid " was given to distilled vinegar in the Pharmacopoeia 
of 1809. 

In the next edition of Phillip's Translation (1824) it 
is pointed out that the " mucilage " f which passed over 
and condensed with the acetic acid in the distillation of 

* Epitome of Chemistry, 1806, p. 302. 

f By the term mucilage was understood what we now describe as " extract." 


vinegar rendered it difficult to obtain pure white acetate 
of potash on saturating the acid with alkali. For this 
reason acetic acid derived from wood was introduced 
into the Materia Medica under the name of " stronger 
acetic acid distilled from wood " (acidum aceticum fortius 
e ligno destillatum) . At that time the strongest acid 
known had a specific gravity of 1-043, and contained 
about 32 per cent, of acid, or five times as much as dis- 
tilled vinegar. 

In the following edition of Phillip's Translation, pub- 
lished in 1836, this " stronger acid " was described as 
" acetic acid " without any qualification, and was stated 
to contain 30-8 per cent, of the anhydrous acetic acid; 
while glacial acetic acid, the strongest acid procurable, 
became solid at about 40 F., and consisted of one 
equivalent of anhydrous acetic acid and one equivalent 
of water. No alteration was made in the next issue in 

In the first edition of the British Pharmacopoeia, pub- 
lished in 1867, " acetic acid " was prescribed to contain 
28 parts of " anhydrous acid/' corresponding to 33 parts 
by weight of the hydrated acid. This corresponded in 
strength with the acetic acid of commerce and the 
" Purified Pyroligneous Acid " of the Dublin Pharma- 
copoeia, but was not so strong as the " Acetic Acid " of 
the London Pharmacopoeia (supra). It was much weaker 
than the "Acetic Acid " of the Edinburgh Pharmacopoeia, 
which contained upwards of 95 per cent, of acid. 

Anhydrous Acetic Acid. Considerable confusion has 
been caused through the belief which was at one time 
generally accepted, that acetic acid did not exist in the 
anhydrous state, and was only known in combination 


with water or a base. In other words, the compound 
we now describe as acetic anhydride was formerly re- 
garded as the hypothetical acid. " Anhydrous acetic 
acid/' as existing in dry sodium acetate, was assigned 
the formula C 4 H 3 3 ,* while glacial acetic acid was re- 
garded as a monohydrated acid, C 4 H 3 O 3 , HO, crystal- 
lising at 45 F. The hypothetical anhydrous acid was 
also known as acetylic acid, from being regarded as a 
compound of the radical acetyl, C 4 H 3 ,* and oxygen. 
This use of the term radical was a development of the 
idea connoted by the word in radical vinegar which was 
in use long before the discovery of oxygen. 

According to Nicholson, f the term radical was used 
in 1823, to describe " the distinguishing part of an acid, 
by its combination with the oxygen common to all acids/' 
Thus sulphur was the radical of sulphurous and sulphuric 

The terms " dry " acetic acid and " real " acetic acid 
were used as synonyms of anhydrous acetic acid, and 
this must be borne in mind in calculating the strengths 
of acetic acid mentioned in the earlier Pharmacopoeias. 
In the British Pharmacopoeia of 1867 reference is made 
to both acetic acids, and to prevent mistake the chemical 
formulae are given, showing that by " real " acid the 
anhydrous compound was understood. 

In the Pharmacopoeia of 1885, however, the term 
" real " acid is used to describe the hydrated acid, 
CH 3 . COOH, thus increasing the confusion ; but in the 
current issue all ambiguity has been avoided by the use 
of the chemical name " hydrogen acetate/' 

* Old notation : C = 6 ; H = 1 ; = 8 

f Dictionary of Chemistry, 1823. 


In 1874 the Society of Public Analysts adopted 3 per 
cent, of " real " acetic acid as the minimum limit of 
strength for vinegar. It is doubtful whether this was 
intended to refer to the anhydrous acid (acetic anhydride) 
or to hydrogen acetate. Allen, speaking in 1893 on the 
subject,* was not certain upon the point, but was inclined 
to believe that acetic anhydride was meant. 

Glacial Acetic Acid. The most concentrated solutions 
of acetic acid were first obtained by saturating dry 
charcoal with vinegar, and distilling the mass. Then, 
by exposing the later fractions of the distillate to a 
freezing mixture, the water separated as ice, while a 
stronger acid could be drained off the crystals. Only a 
relatively weak acid could be thus prepared, and prior 
to the introduction of wood acid all concentrated acid& 
were prepared by dry distillation of verdigris or copper 
acetate. Acid derived in the first instance from the dis- 
tillation of wood soon displaced the acid of higher strength 
derived from vinegar. 

It is interesting to follow in the successive issues of the 
London Pharmacopoeia how the concentrated acetic 
acid of commerce became purer and more concentrated. 
In Phillip's Translation of 1824 there is no mention of 
the glacial acid, and the author states that he has not 
met with acetic acid of greater strength than 30 per 
cent. In the next edition (1836) there is a reference 
to glacial acetic acid, " so-called from becoming crystal- 
line at about 40 F.," while in the following edition 
(1851) the solidification point is given as 45 F. In the 
first edition of the British Pharmacopoeia (1867) glacial 
acetic acid is included as a drug, and is stated ta 

* Analyst, 1893, xviii., 183. 


crystallise at 34 F. and remain solid until the tempera- 
ture reaches 48 F., while in the editions of 1885 and 1898 
glacial acetic acid is required to have a specific gravity, 
of 1-058, and to remain crystalline above 60 F. (15-5 C.). 


The earliest method of preparing a strong acetic acid 
from vinegar has already been mentioned (p. 57). Another 
process of concentration was to freeze the stronger frac- 
tions obtained in the distillation of vinegar, and to 
separate the crystals from the unfrozen acid. 

Acetic Acid from Verdigris. But the chief source of 
acetic acid prior to the discovery of pyroligneous or wood 
acid was copper acetate, which was popularly known 
as distilled verdigris, from the use of distilled vinegar in 
its preparation. This salt was obtained by the action of 
a crude vinegar, derived from refuse grapes, upon plates 
of copper. These were placed on wooden gratings, which 
were suspended in the vinegar for about three weeks, 
after which they were removed, exposed to the air for 
a day or two, and again immersed in the vinegar. In 
many parts of France each farm house had its verdigris 
cellar, where all wine that had become sour was thrown 
into tubs kept for the purpose. 

As soon as the plates had become sufficiently coated 
with the crystals the acetate was scraped off and sold 
in its moist condition to the dealers. 

This salt was a basic acetate with a composition approxi- 
mating to the formula (CH 3 C0 2 ) 2 Cu . CuO . 6H 2 0. When 
it was dissolved in distilled vinegar and the solution 



crystallised, normal cupric acetate, (CH 3 C0 2 ) 2 Cu . H 2 O, 
was obtained. 

The crystals of copper acetate were known to the 
alchemists, who termed them Crystals of Venus, and 
the distilled acetic acid or radial or aromatic vinegar of 
the apothecaries was derived from this verdigris 
by dry distillation in a stoneware retort, which was 
gently heated in a suitable furnace (see Fig. 17). The 
acid vapours were condensed in a series of receivers, the 
last of which was connected by means of a Welter's 
tube with a flask partly filled with distilled vinegar. 

Fig. 17. Apparatus for Distillation of Radical Vinegar. 

When vapours were no longer distilled, and the receivers 
in .the basins of water remained cool the process was 
finished. The acid thus obtained was of a green colour 
from the traces of copper acetate carried over mechani- 
cally in the distillation. It was purified by redistillation 
in a glass retort heated in a sand bath. 

About a fifth of the available acetic acid was lost in 
this process through being decomposed by the heat. 
To obviate such loss the verdigris was heated with a 
small amount of sulphuric acid ; but this had the draw- 
back of yielding a distillate containing sulphurous acid, 


while lacking the pleasant aroma (the so-called pyro- 
acetic spirit) of the product obtained by dry distillation. 
Hence, long after the introduction of wood acid, the 
process described above continued in use for the manu- 
facture of " aromatic vinegar/' It was not until the 
method of purifying wood acid had been perfected that 
it was finally superseded. 

Preparation from Spirit Vinegar. The commercial spirit 
vinegar (Essig-sprit or Spritessig), containing about 
12 per cent, of acetic acid, is used as the source of a 
concentrated acetic acid of about 80 per cent, strength, 
which fetches a much higher price than acetic acid derived 
from wood. 

Such concentration is not possible simply by fractional 
distillation in an ordinary retort, since the stronger 
fractions which pass over towards the end of the dis- 
tillation are contaminated by products of the decomposi- 
tion of extractive matters in the vinegar. 

To obviate this, Stein devised a method of raising the 
boiling point of the vinegar by adding to it about one- 
third of its weight of salt. By this means a considerably 
larger yield of acetic acid was obtained, though a large 
proportion was still left in the retort. The distillation 
was carried out in tin or copper retorts. 

Although a much stronger product than the original 
vinegar was obtained in this way, the method has been 
superseded by the process of neutralising the Essig- 
sprit with lime, evaporating the liquid to dryness, and 
distilling the crude calcium acetate with a mineral acid. 
The distillate has a specific gravity of about 1 -060 (about 
49 per cent.), and is purified by further distillation with 
sodium or calcium acetate. 


Acetic Acid from Wood. The discovery that acetic acid 
was formed in the dry distillation of wood appears to 
date back no further than the middle of the eighteenth 
century, when Glauber described a " wood acid " or 
pyroligneous acid as one of the constituents of the dis- 
tillate, while Boerhaave pointed out that this acid was 
closely related to the acid of vinegar. Glacial acetic acid 
was first prepared in 1793 by Lowitz, and seven years 
later it was proved by Fourcroy and Vauquelin that 
pyroligneous acid was nothing more than acetic acid 
contaminated with other products of the distillation. 
It was owing to the difficulty of completely eliminating 
these impurities that the identity of wood acetic acid 
and vinegar " acetous " acid remained unknown for so 
long a time. 

In the year 1799 the first plant for the dry distillation 
of wood on a manufacturing scale was erected by Lebon, 
with the object of obtaining charcoal, pyroligneous acid, 
tar, and gas for lighting and heating purposes. A few 
years later a factory was started by Stoltze in Halle for 
obtaining pyroligneous acid from wood and converting 
it into pure acetic acid. About the same time the manu- 
facture was begun in England, and in 1808 Mollerat 
was distilling wood at Pellerey in France, and converting 
the acid into a table vinegar. 

An outline of his process was published in Paris,* 
with reports upon the products by Berthollet, Fourcroy, 
and Vauquelin. It was stated that the acid there pro- 
duced was of such strength that when diluted with 

* Memoires sur la Distillation du Bois et 1'Emploi de ses Produits, par 
J. M. Mollerat, et Rapports faits a ce Sujet par M. M. Berthollet, Fourcroy 
et Vauquelin, Paris, 1808. 



seven parts of water it yielded a good vinegar, and that 
it was identical with the acid obtained by the distillation 
of wine vinegar. 

Pyroligneous Acid. The crude acid first separated from 
the products of the distillation is a yellowish-brown 
to dark brown liquid with a characteristic tarry odour. 
It has a specific gravity ranging from about 1-020 to 
1-030, and contains not only acetic acid but also small 
amounts of other fatty acids (formic, butyric, valeric), 
together with esters, alcohols (e.g., furfural), acetone, 
phenols, and tarry products. The proportions of these 
constituents vary with the nature of the wood, tem- 
perature of distillation, and method of condensing the 

The antiseptic action of the crude acid is largely due 
to the presence of the phenols, and accounts for its value 
as an agent for curing hams and fish. 

After removal of the acetone the crude pyroligneous 
acid is neutralised with lime, and the liquid evaporated 
to obtain crude brown acetate of lime. Or soda is used 
for the neutralisation of the liquid, which is then con- 
centrated to obtain acetate of soda. 

These impure salts are sold to the makers of acetic 
acid, who distil them with hydrochloric or sulphuric 
acid, to separate the combined acetic acid. 

The acid derived from the calcium salt is known com- 
mercially as " lime acid/' while that derived from sodium 
acetate is termed " soda acid," and fetches a higher 
price, owing to its usually containing less impurities, and 
thus having a better aroma. 

Acid from Acetate of Lime. The modern process of dis- 
tilling acetic acid from commercial acetate of lime may 


be made more clear by the following outline : On dis- 
tilling together 1 ton of acetate of, say, 65 per cent, 
strength, and 1 ton of hydrochloric acid of 30 Tw., 
there will be obtained approximately 

(a) 180 gallons of strong acid of specific gravity 1-057, 

say, 46 per cent. ; 

(6) 100 gallons of feints of specific gravity 1-020, say, 
10 per cent., 

corresponding together to 43 per cent. acid. 

The strong crude acid (a), when fractionated in a 
column still, taking a charge of about 250 gallons, will 
yield approximately 

(1) 25 gallons of first runnings, used in the manufacture 

of white lead. 

(2) 150 gallons of middle fractions (specific gravity, 

1-045 to 1-050) used for preparing acid (6). 

(3) 50 gallons of last runnings of about 70 per cent. 


(4) 20 to 25 gallons of a residue of acid, tarry matters, 

fatty acids, etc. 

The feints (b) are neutralised with soda, evaporated, 
and crystallised, the crystals of sodium acetate being 
separated by means of a hydro-extractor, and used for 
the manufacture of the best " soda acid." 

The fraction (2) is redistilled, after treatment with 
sulphuric acid and potassium permanganate to destroy im- 
purities, the middle fractions being used for technical acid. 

The stronger fraction (3) is also oxidised in the still, 
together with the similar fractions from other charges, 
and is redistilled to obtain higher strengths (80 per cent., 
to glacial acid). 


In each case the first oily runnings and weaker fractions 
are separated, and worked up with similar fractions. 


Oxidation by Means of Platinum Black. The process 
of catalytic oxidation, discovered in 1835 by Dobereiner 
(see p. 52), has been made the basis of several indus- 
trial methods, especially in Germany, where alcohol is 
relatively cheap. 

The original manufacturing apparatus of Dobereiner 
consisted of a glass vessel in which was a series of sup- 
ports at different levels. On each of these were several 
basins, each containing a tripod holding a watch-glass 
filled with platinum black. A current of air was drawn 
through the apparatus, while the temperature was main- 
tained at 30 to 35 C. by means of a steam coil. The 
vapours of the evaporated alcohol came into contact with 
the oxygen, and under the influence of the platinum black 
acetic acid was produced, and condensing upon the walls 
of the vessel, was collected in a receptacle at the bottom. 

An apparatus with a capacity of about 700 litres, 
containing about 200 to 210 grammes of platinum, was 
capable of transforming 1 kilo, of pure alcohol into 
acetic acid, while in some of the larger apparatus a charge 
of as much as 17 kilos, of platinum black was employed 
to convert 150 litres of alcohol into acetic acid per day. 

In practice it was found that the regulation of the 
exact quantity of air was extremely difficult. If too 
little was supplied a large proportion of acetaldehyde 
and acetal was produced, while by increasing the current 
of air there was a loss of acetic acid by evaporation. 


A much more important drawback was that after a 
short time the platinum black became spent, and had 
to be re-calcined to render it active again a process 
of necessity attended with the loss of expensive material. 

To obviate this a method was devised in which the 
platinum black was maintained at about 300 C. in a 
porcelain tube, through which was passed a current of 
alcohol vapours mixed with air or oxygen. 

In a later modification of the process the platinum 
black was heated to incandescence by means of an electric 

Use of Ozone. In the year 1872 a note was published 
by Widemann * upon the use of ozone in the manufacture 
of vinegar. The process described consisted in causing 
the alcoholic liquid to fall drop by drop through a column 
containing fragments of glass or porcelain, and to meet 
on its way a current of hot air which had been passed 
through a gas flame. The action of this hot air upon the 
alcohol was claimed to effect acetification. 

A plant to work the process upon an industrial scale 
was set up by Widemann in America, and numerous 
modifications of the process were patented. 

It is open to question whether simple passage of air 
through a gas flame will effect ozonisation of the oxygen. 
Moreover, Claudon,f who repeated the experiment with 
air which had been ozonised in the usual way, was unable 
to obtain similar results. The expense of ozonisation 
would also be a factor against the commercial success 
of any such process, even if practicable. 

Ozone in Acetiflers. By a curious misapprehension of 

* Comptes Eendus t 1872. 

f Fabrication du Vinaigre (C. Franche), p. 188. 


the function of ozone in any chemical oxidation of alcohol, 
attempts were made, especially in this country, to accel- 
erate acetification by the introduction of ozonised air 
into the acetifiers. 

The experiments were tried on a large scale in several 
of the largest vinegar works in London, but in no case 
did they prove successful, and were abandoned after a 
few months' trial. 

It is difficult to understand the theory supposed to 
underlie this use of ozone, for it is a powerful bactericidal 
agent, and would thus be most unlikely to promote the 
growth or activity of acetic bacteria. 

The statements put forward by the promoters of some 
of these processes to the effect that the Mycoderma aceti 
developed more readily in the presence of ozonised air, 
as, for instance, when the gyle containing it was projected 
in a fine spray into a chamber of such air (see illustration, 
p. 71), have not been borne out by the results of prac- 
tical experience. 

Newton's Apparatus. In the apparatus patented by 
Newton (Eng. Pat. 1905, 1872) the use of ozone or 
ozonised air "produced by passing a current of atmos- 
pheric air through a flame " was claimed for effecting 

The liquid to be acetified was pumped from the vessel 
N in the form of a fine spray into the chamber A, where 
it meets with the ozone or ozonised air drawn or forced 
by means of the pump, K, from the vessel B. A series 
of such chambers may be superposed, the liquid leaving 
the bottom of each being passed in a fine spray into the 
next one below. 

Properties of Acetic Acid. Pure acetic acid is a colourless 



liquid with a characteristic pungent odour of vinegar. 
When chilled a little below the ordinary temperature it 
solidifies to a crystalline mass, the solidification point 
depending upon the strength of the acid (vide infra). 
When applied to the skin it produces blisters, and many 
fatal accidents have been caused through its being 
inadvertently swallowed. 

Fig. 18. Newton's Patent Process. 

Although an organic acid, it is remarkably stable, and 
is not readily attacked by oxidising agents. It can be 
decomposed by passing its vapour through a tube heated 
to redness, the products of decomposition including 
methane and acetone. 

Most of its salts are soluble in water ; several of them 
are of commercial importance. This aluminium acetate 


and ferric acetate (red liquor] are used as mordants in 
dyeing, while verdigris (q.v.) and emerald green (cupric 
aceto-arsenite) form the basis of oil pigments. 

Solidification Point of Acetic Acid. The determination 
of the freezing point of glacial acetic acid is one of the 
most reliable methods of ascertaining the amount of 
water present, as was first pointed out by Riidorff.* He 
showed that acetic acid of 100 per cent, strength solidified 
at 16-7 C., and that with each slight increase of water 
the freezing point fell. His results, which are given in 
tabular form below, did not go below mixtures con- 
taining 20 per cent, of water, and his determinations 
were afterwards supplemented by Grimaux,t who ascer- 
tained the freezing points of mixtures of all strengths, 
from 93 to 16 per cent., and gave the following summary 
of his results : 


100 Parts of 

100 Parts 

100 Parts of 

100 Parts 

Acetic Acid 



Acetic Acid 



mixed with 



mixed with 









+ 16-7 



















11-0 9-910 





12-0 10-774 





























* Ber. d. d. Chem. Ges., 1870, iii., 390. 
f Comptes Rendus, 1873, Ixxvi., 486. 
% Ber. d d. Chem. Ges., 1870, iii., 370. 





Acetic Acid. 



Acetic Acid. 


Per cent. 

Per cent. 


Per cent. 

Per cent. 




+ 5-3 56-54 





-1-4 61-68 





-11-6 69-23 





-19-3 76-23 


- 8-2 



-20-5 79-22 


- 7-3 



-24-0 81-89 


- 6-4 



-22-3 83-79 


- 5-5 




If these results are plotted in a curve in which the 
ordinates are the solidification points and the abscissae 
the proportions of water, it will be found that the lines 
connecting the temperatures are practically straight, 
and that their point of intersection, showing the maximum 
lowering of temperature, corresponds to the mixture 
containing about 37 per cent, of water. This pro- 
bably indicates the formation of a definite hydrate, 
C 2 H 4 O 2 -f 2H 2 O. No break occurs at about 28 per cent, 
of water, such as is found in the table of specific gravities 
at 15 C., where possibly the presence of a compound, 
C 2 H 4 O 2 + H 2 0, is suggested. 

It has already been pointed out (p. 61) that the 
pharmacopceial requirements for the solidification point 
of glacial acetic acid have steadily been raised. In the 
edition of 1898 glacial acetic acid was required to 
contain 98-9 per cent, of hydrogen acetate (by titration), 
and to remain solid at 15-5 C. (60 F.). Now, this solidifi- 
cation point corresponds to an acid containing not 99 per 
* Comptes Rendus, 1873, Ixxvi., 486. 


cent., but nearly 99-5 per cent., as is shown in RMorfFs 
table (p. 72). 

In the new Pharmacopoeia (1914) this error has been 
corrected, and glacial acid (98- 9 per cent.) is required not to 
re-melt entirely until the temperature rises above 14' 7 C. 

The point is of considerable importance in connection 
with the Customs duties in certain countries . For example , 
in New Zealand all glacial acid below the strength of that 
of the British Pharmacopoeia is required to pay an excess 
duty of 5d. per lb., which is considerably more than the 
ordinary duty. 

Since the strength is ascertained, by the Customs 
officials, simply by determining the freezing point, acid 
of over 99 per cent, was, prior to 1914, liable to rejection 
if it did not behave like acid of 99-5 per strength. 

This anomaly is not found in the United States Pharma- 
copoeia, which defines glacial acid as containing 99 per 
cent, of absolute acid, solidifying below 15 C., and 
becoming fluid again at about 15 C. 

AT 20 C. (Ftoy). 

Acetic Acid. 


Acetic Acid. 


Acetic Acid. 


Per cent. 

Per cent. 

Per cent. 









































Optical Refraction. The refractive index of acetic acid 
shows analogous variations according to the strength. 



As is seen in the foregoing table of results by Fery, it 
increases steadily up to about 85 per cent., where a 
break occurs in the curve, and the refraction falls to 
1-3710 at 20 C. 

WATER (Oudemanns)* 

Acetic Acid. 

Gravity at 
15 C. 

Acetic Acid. 

Gravity at 
15 C. 

Acetic Acid. 

Gravity at 
15 C. 

Per cent. 

Per cent. 


Per cent. 





























. 28 













































































































































































* Jahresber. Fortschritte der Chemie, 1886, p. 302. 


Specific Gravity. Tables of the specific gravity of 
mixtures of acetic acid and water of different strength 
have been published by Mohr and by Oudemanns (supra), 
but these differ considerably from each other, possibly 
owing to the presence of traces of higher acids as impuri- 
ties in the acetic acids used for the determinations. 

For acids of strengths of 25 to 40 per cent, a deter- 
mination of the specific gravity is useful as a rough 
estimate of the strength, but many of the acids of 80 per 
strength upon the market do not comply with the specific 
gravity given in the tables. 

The tables agree more nearly for the lower strengths 
up to 10 per cent. 














6 C. 



















The Mash -Tun Mashing Machines Hot Liquor Backs Process of Mashing 
Gelatinised Grain Addition of Sugar The Conversion Process 
Fermentation of the Wort Storing the Gyle. 

THE first step in the manufacture of vinegar is the pre- 
paration of an alcoholic wash, containing also sufficient 
nutriment for the acetic bacteria. 

In the production of spirit vinegar in France and 
Germany a diluted spirit derived from potatoes or maize 
starch is mixed with a small proportion of phosphates 
and ammonium salts, and used for the purpose. Wine 
vinegar is made from diluted wine, and cider vinegar from 
sour cider or from apple juice expressed for the purpose. 
Any substance capable of fermentation so as to yield 
an alcoholic liquor is also capable of acetification under 
suitable conditions, but in this country the bulk of the 
vinegar is manufactured from malted or unmalted grain, 
or from a mixture of cereals and fermentable sugars. 

The malt or malt and grain is infused in a mash-tun or 
saccharified in a " converter " by means of a dilute acid, 
and the gyle thus obtained is clarified and acetified as 
subsequently described. 

The Mash-Tun. The most important piece of apparatus 
common to the brewer and the vinegar maker is the 


mash-tun. As the vinegar manufacture has lagged 
behind the brewing industry, the old-fashioned plant of 
fifty years ago may still be found in some vinegar works. 




For example, an open mash- tun, like that shown in 
the accompanying illustration (Fig. 19), in which the 
revolving rakes travelled round the tun by engaging in 
teeth upon the circumference, has been seen by the writer 
in old vinegar breweries. 

This type of mash-tun had superseded the still earlier 
form in which the crushed malt and hot water were 

Fig. 20. Section of Mash-Tun. 

stirred together by long poles termed " oars." In up- 
to-date vinegar works the mash-tun is completely closed 
in with non-conducting material, to prevent loss of heat, 
and it is fed by a mashing machine from a hot liquor 
back and grist case. 

The copper which supplied the older mash-tun has, in 
many instances, been retained for heating the water for 


the first mash, but the stokehole has been abolished, and 
its place taken by a steam pipe. 

The most suitable form of mash-tun for vinegar brewing- 
is one provided with rakes, and 
also with a steam coil beneath 
the perforated false bottom, to 
enable the temperature of the 
mash to be raised gradually from 
a relatively low temperature. 

For the reasons given below, 
this is much more satisfactory 
than raising the temperature 
suddenly by means of " under- 
letting/' as is usually done in 
mashing malt for beer. 

Otherwise the construction of 
the mash-tun is the same as in a 
brewery (where it is exceptional 
to find mash- tuns with coils), and 
has the appearance in vertical 
section shown in Fig. 20. 

The steam coil would be fixed 
in the space C beneath the per- 
forated plates. 

The sparge is an essential part 
of the plant in a modern vinegar 
brewery. As shown in the 
diagram (Fig. 21), it consists of 
a cylindrical box or " basin/' 
communicating at the bottom 
with two arms, and is made to revolve easily about a 
central axis. 



The hot water coming from the copper enters the two 
arms, which are perforated at regular intervals on one 
side, and by its pressure as it escapes from the holes 
causes the sparge to rotate and to sprinkle the upper 
surface of the mash with an evenly distributed shower. 

Mashing Machines. The use of an external mashing 
machine is particularly suitable for brewing the wort 
for vinegar, since it enables a more thorough and even 
admixture of the grain and hot liquor at any desired 
temperature for the initial mash to be made than is 
possible in the mash-tun itself. 

Fig. 22. Section of External Mashing Machine. 

The first machine of this type was invented in 1853 by 
Steel, and in all essentials is the same as the mashing 
machines still most frequently in use. 

As is shown in the section (Fig. 22), it consists of a 
shaft B with rakes and arms at right angles, revolving 
in a horizontal cylinder of copper or iron A. 

The screw propeller H is a modern addition, and was 
not present in the original machine. The shaft is made 
to revolve by means of a strap over the wheel D, at a 



speed of 150 to 180 revolutions per minute, and thus 
causes a very rapid admixture of the hot water, which 
enters by a pipe at E with the grist which comes from the 
grist case through a shutter F, the movement of which is 
controlled by the wheel G. 

In another type of mashing machine the agitators are 
eliminated. Thus, in Maitland's machine, the grist is 
delivered in a steady stream into a cylinder with per- 
forated walls. This is surrounded by another cylinder, 
into which the hot water is forced, and is thence drawn 
in a series of fine jets through the perforations. At the 
bottom of the cylinder a larger jet of hot liquor is forced 
upwards, and meeting the falling grist, completes the 

Hot Liquor Backs. The use of coppers for heating 
the water for mashing has been superseded in most 
vinegar works by a hot liquor back, which is fixed at a 
level above the mash-tun, and is connected with the 
mashing machine, and also with the underletting pipe. 
This back is usually in rectangular form, and is generally 
made of iron cased in with non-conducting material to 
prevent loss of heat. 

The liquid is most conveniently heated by means of a 
steam pipe delivering steam into the back, and if care 
be taken to prevent oil or impurities from the boiler 
gaining admission to the water, this method is quite 

Where, however, impurities are likely to be carried 
over with the steam, it is preferable to heat the water 
by means of a copper coil. The steam entering thus 
parts with its heat, and is condensed, and the water 
escapes through a trap at the end of the coil. 


The temperature of the water in the back is indicated 
by a special thermometer, which is bent at right angles 
and fixed in an opening in the side of the back. As a 
rule, there is also a gauge tube outside the back to show 
the height of the water within. Or, in some breweries, 
a float attached to a cord passing over pulleys serves 
this purpose, the amount of liquor being indicated by 
the position of a counterweight at the other end of the 
cord, in relation to a scale. 

Process of Mashing. The first stage in the preparation 
of a malt or grain vinegar is in all essentials the same 
as in a distillery. In each case the object is to obtain 
as high a proportion as practicable of sugars in a fer- 
mentable form. 

In this respect the mashing process differs from that used 
in the brewing of beer, where, since the aim is to leave 
a relatively large proportion of unfermentable dextrins, 
a considerably higher mashing temperature is per- 
missible. . * --, 

The vinegar brewer, like the distiller, must mash his 
malt or malt and grain at a lower temperature, and the 
boiling of the wort practised by the brewer is usually 
unsuitable for his purpose. 

If he is using a mixture of malted and unmalted grain, 
he will require a malt of good diastatic power, but when 
malted barley is being used alone a malt of low diastatic 
power (say about 30) will give good results. 

The malt or mixture of malt and grain is crushed in 
exactly the same way as in a brewery, and is then passed 
through a Steel's mashing machine into the mash-tun, 
with the calculated quantity of water to give a mash 
at a temperature of about 120 F. 



The temperature is then very slowly raised, either by 
underletting water at a higher temperature or, preferably, 
by means of a steam coil at the bottom of the mash-tun. 

In this connection it is of practical interest to note 
that in the writer's experience naked steam may be 
admitted at this stage into the mash- tun, without any 
appreciable injury to the diastase of the malt. After 
the temperature has in this way been gradually brought 
up to about 152 F., while the goods have meanwhile 
been kept in constant movement by the rakes in the 
tun, the mashing is continued until the liquid no longer 
gives a blue coloration with iodine. 

This infusion is then drained off and a second mash 
of an hour is given with a smaller quantity of water 
at 155 F., this extract being drained off as before. Finally 
the goods in the tun are washed from above with water 
at 155 F., which is distributed over their surface from 
the arms of a revolving sparge. 

The united extracts, which will have a specific gravity 
of about 1-060 (from 45 quarters of malt), are cooled 
to about 70 F. by means of refrigerators, and are then 
fermented with yeast as described subsequently. 

A wort obtained in this way is readily fermentable, 
but the use of low-dried diastatic malts and low tem- 
peratures for mashing has the drawback of yielding 
vinegars which are sometimes very difficult to free from 
a slight degree of cloudiness. This turbidity appears 
to be partly due to albuminous substances, which can be 
coagulated by heat ; for boiling the worts enables them 
to be filtered with much more ease. 

As a rule, however, it is not practicable for the vinegar 
maker to boil his worts, since by so doing he converts 


dextrins into an unfermentable form, and thus reduces 
his yield of alcohol, and subsequently of acetic acid. 

In practice, therefore, it is advisable to use a malt that 
has been dried at a medium temperature. This will give 
a wort which, while fermenting well, although not giving 
the highest yield of alcohol, will yield a vinegar which 
can be made " bright " without much difficulty. 

A further objection to the production of an infusion 
containing the largest possible proportion of fermentable 
sugar is that the vinegar prepared from such a wort will 
contain very little solid matter, and that there will, 
therefore, be a possibility of its being condemned as an 
adulterated article under the Food and Drugs Act. 

Gelatinised Grain. By submitting the grain to a 
preliminary heating, the starch granules swell up and 
become gelatinised, and are then much more readily 
attacked and dissolved by the diastase of malt. 

For this reason it is possible to use a much larger 
proportion of grain of this description than of ordinary 
untreated or " raw " grain, with the malt in the mash- 
tun, or to use a malt of much lower diastatic power. 

Torrefied or " popped " barley is one of these products. 
It is prepared by heating the barley until the starch 
granules are ruptured and the grain is slightly roasted. 
In the process of roasting the moisture of the barley is 
reduced to about 3 to 4 per cent., while the fat is lowered 
by about 50 per cent., both of which changes are advan- 
tageous from the brewing point of view. 

Flaked Maize and Rice. As the large amount of oil 
in the maize is of no use to the brewer, preparations 
known as "flaked maize" or "flaked maize malt" are 
sold in large quantities. 


They are prepared by crushing the maize, removing 
the germ containing the bulk of the oil, and gelatinising 
the starch by heat. To some extent the heating does 
the work of diastase, and for this reason such products 
have become known as " malts " in the brewing industry. 

Flaked rice is prepared in a similar manner, but in that 
case the process is not so advantageous to good mashing, 
since rice contains much less oil than maize. 

Analyses of gelatinised grains are given in Chap. X, and 
show the influence of the processes upon the composition 
of the cereals. 

In some vinegar breweries rice or maize grits are 
partially gelatinised on the spot by subjecting them to 
the action of steam under pressure. This ruptures the 
starch granules, converting the whole mass into a paste, 
which, when cooled to about 130 to 140 F., is rapidly 
liquefied on the addition of a small amount of crushed 
malt. It can then be run into the mash-tun, where the 
saccharification of the starch is completed at the same 
time as the rest of the mash. In this way a large quantity 
of raw grain can be introduced into the mash-tun, without 
any risk of finding unconverted starch in the wort. 

This entails the use of a separate vessel or " converter " 
for the gelatinisation of the starch of the raw grain, but 
by suitable manipulation and saccharification in stages 
it is possible to use the mash-tun itself for the purpose. 

For example, a mixture of the crushed barley and malt 
is slowly heated from about 130 to about 170 F. The 
sugar formed in the hydrolysis at the lower temperatures 
protects the diastase for some time at the higher tem- 
perature, so that a considerable amount of the starch 
in the raw grain is converted. The temperature is then 


raised to over 200 F., and kept at that point for about 
30 minutes to gelatinise the starch, after which the mash 
is cooled to 130 to 135 C. by means of a coil, and a fresh 
portion of ground malt added to complete the hydrolysis 
of the gelatinised starch. When now the temperature is 
gradually raised to 155 F., the conversion is rapidly 
completed, and the wort is then drawn off, and the 
" goods " sparged in the usual way. 

Addition of Sugar. Certain makers of vinegars prefer 
to buy the products of the acid hydrolysis of cereal starch 
in the form of ready-made glucose, which is sold either 
in the form of a thick syrup or as a solid. 

A suitable proportion of the sugar is added to the wort 
as it leaves the mash- tun, and a much more concentrated 
wash can thus be prepared without the necessity of using 
larger plant. 

Worts to which commercial glucose has been added 
usually " attenuate " very far, and hence in some cases 
yield a vinegar deficient in " body/' To prevent the 
product being too thin in this respect special preparations 
containing unfermentable dextrins are sometimes used, 
or a certain proportion of molasses may be mixed with 
the glucose. 

In several of the larger vinegar breweries a " converter " 
is used for transforming the starch of the cereal into 
fermentable sugar, and thus, while obtaining all the 
advantages of a product prepared by acid hydrolysis, 
they also retain the other constituents of the grain (the 
nitrogenous compounds and phosphoric acid), which are 
not present in commercial glucose. 

The Conversion Process. Instead of the starch of 
cereals being saccharified by the diastase of malt, a process 


in which a dilute mineral acid is used as the hydrolytic 
agent is employed. 

Maize or rice are the chief materials used by those who 
prepare their worts in this way, and when malt is also 
added, as is sometimes the case, the object of the addition 
is to give a malt flavour to the product or to make it 
answer more closely to the normal composition of a 
barley malt vinegar. 

In converting the starch into fermentable dextrose, the 
grain is mixed with dilute sulphuric acid (about 3 per 
cent, strength) in a closed iron vessel, where it is heated 
for several hours by steam under pressure until a sample 
of the liquid no longer gives a reaction for unconverted 

The contents of the converter, which now consist 
largely of an acid solution of dextrose, are neutralised 
with lime and chalk, which precipitate the sulphuric 
acid as gypsum, and are then drawn off, cooled, and 
fermented in the same way as the wort obtained by 

A converter of average size will take a charge of 6 to 
7 tons of grain, and the whole of the starch will be hydro- 
lysed within about three hours, when heated with steam 
under a pressure of about 10 Ibs. After neutralisation 
the mixture is allowed to stand for several hours for the 
calcium sulphate to subside, and is then drawn off through 
filters, cooled, and passed into the fermenting tuns. 

As it leaves the filters the wort (from the above-men- 
tioned quantity of grain) will show a specific gravity of 
about 1 -070, and, if a strong vinegar is required, is pitched 
with yeast directly without any dilution. It is more 
usual, however, for the liquid to be diluted with water 


to a specific gravity of 1-055 to 1-060 before 

Although the bulk of the calcium sulphate separates 
in insoluble form during the neutralisation, a considerable 
proportion will still remain in solution, and will afford 
an indication, though not an infallible one, that the 
vinegar has been prepared by a conversion process. 

Fig. 24. Underback and Refrigerator (A.D. 1812). 

Usually the glucose solution derived from the acid 
hydrolysis of grain is readily fermentable, and a wort 
of specific gravity 1-060 can be attenuated without 
difficulty down to a specific gravity of 1-004 to 1-005. 
Vinegars prepared from the products of the " converter " 
are frequently sold as " malt vinegar/' although they 
do not comply with the definition suggested by the 


Local Government Board, which requires the starch to 
have been saccharified by the diastase of malt. 

Fermentation of the Wort. After leaving the mash-tun 
the wort, including the spargings, is pumped through 
a refrigerator to cool it down sufficiently for the addition 
of the yeast. 

In the older vinegar breweries cooling was effected by 
exposing the liquid to the air in large shallow tanks, 
known as coolers, such as that shown in Fig. 24, 
which represents the obsolete plant used in 1812 in 
Messrs. Beaufoy & Co.'s Works. But at the present day 
the same course is followed as in breweries, and the wort 
is cooled by means of refrigerators, which are usually 
of the vertical type. 

As is shown in Fig. 25, the refrigerator consists essen- 
tially of a series of superposed tubes, through which 
passes a current of cold water. The wort is pumped 
into a trough above these and trickles through holes in 
the bottom of this in a number of thin streams over 
the tubes, in succession, until it reaches the large trough 
in which the apparatus stands. 

The cooling tubes are frequently of oval instead of 
circular form, so as to offer a larger cooling surface to 
the liquid trickling over them. 

Horizontal refrigerators (Fig. 27) are sometimes em- 
ployed where there is insufficient height for the other 
type, and when the supply of water is plentiful. They 
are made in the form of a rectangular trough with 
partitions at intervals. In each compartment is a hori- 
zontal tube with rounded ends, through which passes 
the cold water. The hot wort passes successively 
through these compartments, and is thus cooled in 


To face p. 93.] 

Fig. 26. Exterior of Fermenting Tuns. 



stages before running into the main leading to the 
fermenting tun. 

Except in cases where a good growth of yeast is the 
primary object, it is unnecessary to cool the wort for 
vinegar to so low a temperature as is required for beer. 

Yeast may be added to the wort at a temperature of 
70 to 75 F., and although a " boiling fermentation " 
usually follows, the attenuation takes place more rapidly 
and completely than when lower temperatures are main- 
tained. The temperature rapidly rises, and on the second 

V/AUR OUttfb 

Fig. 27. Horizontal Refrigerator. 

day will be as high as 90 to 93 F., falling on the third 
day to about 85 F., while the yeast working under such 
conditions produces very little " head." 

In some vinegar factories the production of yeast is 
the main end in view, while vinegar is only manufactured 
as a by-product. In such cases the conditions to be 
followed are quite different from those described above. 
The wort must be cooled to a much lower point (say 
about 60 F.), and, after " pitching," the temperature 


in the fermenting tun must be kept at about 70 to 
75 F. by means of an attemperator, or cooling coil 
within the vat (see Fig. 28). 

Much more efficient aeration is also required to obtain 

Fig. 28. Fermenting Tun with Cooling Coil and Parachute. 

a good crop of yeast than when attenuation of the wort 
is the main object. Various devices are in use for this 
purpose. In addition to the primitive wooden rouser, 
a current of air is sometimes pumped into the vat through 


a tube which passes nearly to the bottom of the liquid, 
and terminates in a rose or perforated radial arms. 

A common form of apparatus for removing the yeast 
from the surface of the liquid is that known as the 
" parachute " (Fig. 28). This consists of a funnel ending 
in a tube, with a valve near the top, which can be con- 
trolled from the outside. The yeast is driven into the 
parachute by means of a metal " skimming board/' as 
shown, and is collected in a tank below the tun, where 
it is washed with water, and then pumped into a press. 

The parachute and skimming board are attached to 
a rack and pinion work, so that they can be raised or 
lowered at will, and means are also provided for making 
the skimming board sweep over the surface of the liquid. 

Unless special precautions are taken to keep a 
low temperature and to aerate the liquid thoroughly 
during the fermentation, it is of little use attempting 
to press the yeast, since it assumes such a slimy condition 
that it speedily clogs the cloths of the filter press. 

The choice of a yeast for the fermentation will largely 
depend upon which of the two modes of fermentation 
is to be followed. As brewing in the vinegar industry 
takes place more or less intermittently (with the exception 
of the factories that manufacture pressed yeast), it is 
usually not practicable to use the strain grown in the 
vinegar works. 

Apart from that, the yeast is weakened in the high 
temperature fermentation, and is less suited for a fol- 
lowing fermentation than a yeast grown at a lower 

The best course to follow is to select the type of brewers' 
or distillers' yeast which is found by trial to be the most 


suitable for the wort at the desired temperature, and to 
obtain a fresh supply thereof for each brewing. 

Storage of the Gyle. After fermentation is complete 

Fig. 29. Old Store Vats. 

the alcoholic wash is racked into storage vats, where 
it is left for some weeks or months before being trans- 
ferred to the acetifiers. The longer this period of storage 


can be made the better the wash is suited for acetifica- 
tion. Not only does it clarify itself spontaneously, 
throwing down a deposit of dead yeast cells, but it also 
undergoes a preliminary acetification. Hence a wash 
that has been stored for three months may contain as 
much as 2 per cent, of acetic acid, and thus reduce the 
time required for the work of the acetifiers. It has also 
the advantage of keeping the acetifiers cleaner than in 
the case of freshly-fermented gyle, while the vinegar it 
produces can be obtained in " bright " condition much 
more rapidly than is otherwise possible. 

For these reasons it is the practice in some vinegar 
works to do the main portion of the brewing at one time 
of the year, and to acetify the wash at another. It may 
almost be accepted as an axiom that the greater the 
storage capacity of the works the better the condition 
both of the gyle and of the finished vinegar. 



APPABATUS : The Slow Process Fielding The Orleans Process Claudon's 
Apparatus The Quick Process English Acetifiers. DISTRIBUTION 
OF THE GYLE : The Sparger The Tipping Trough Siphon Distri- 
butors Aeration Devices Wagenmann's Graduator Luck's Acetifier 
Singer's Apparatus Bersch's Acetifier. ACETIFICATION IN PRACTICE : 
Aeration The Temperature Effects of Alcohol and Acetic Acid The 
Group System Disturbances due to Mother-of- Vinegar The Vinegar 
Eel The Vinegar Mite The Vinegar Fly. 

The Slow " Process. However the alcoholic wash or gyle 
has been prepared, it has to be subjected to the combined 
action of the acetic bacteria and atmospheric oxygen to 
convert it into vinegar. The oldest process of effecting 
this change was by exposing the casks partially filled 
to the air, with their bungs drawn out. 

This method, which is now obsolete in this country, 
was known as " fielding," from the fact of the casks 
being exposed in series of rows in the vinegar field. 

Between each series of rows was an underground pipe 
communicating with a " back " at the top of the brew- 
house, and each cask was filled by means of a hose attached 
to a cock upon the distributing pipe, the top of the hose 
being passed from cask to cask as shown in the illustra- 

During fine weather the bung-holes were loosely covered 


with pieces of slate, to prevent access of dust, but during 
wet weather the bungs were replaced. 

Several months were required for the conversion of 
the gyle into vinegar, the length of time depending upon 
the temperature of the atmosphere, and the amount of 
aeration that was possible by way of the bung-holes. 

When the fielding was finished the vinegar was drawn 
off by means of siphon tubes into a trough, the lower end 

Fig. 30. Vinegar Field. Filling the Casks. 

of which delivered into a travelling tank, which could 
be moved up and down between the rows (see Fig. 31). 
Thence it ran through a hose and underground into a 
well in the building, to be pumped into the store vats 
prior to filtration. 

This " slow " process of acetification was practically 
the same as the " Orleans process " of making wine 
vinegar, the only difference being that in the latter the 


casks are kept in a 
heated building and 
means are provided for 
the admission of more 

The Orleans Process. 
The method of aceti- 
fying wine that has 
been used from time 
immemorial in France, 
and especially in the 
district of Orleans, 
whence it takes its 
name, is not the same 
as that described by a 
correspondent of the 
Royal Society in 1670 
(p. 5), which is essen- 
tially the modern 
" quick " process. 

According to 
Franche,* the reason 
why the Orleans pro- 
cess has not been 
displaced by the more 
modern " rapid pro- 
cess " is that it will 
not acetify alcoholic 
solutions containing less 
than 25 per cent, of 

* Manuel Pratique du Fabri- 
cant de Vinaigre, p. 53. 


wine. Below that strength it is necessary to add phos- 
phates and nitrogenous substances ; and since these 
products from wine diluted with alcohol have to be 
sold under the name of " spirit vinegar," the Orleans 
process has come to be regarded as the only possible 
method of making pure wine vinegar. 

The apparatus working by the " quick method " is 
stated by Franche not to give satisfactory results with 
wine or mixtures of wine and alcohol, owing to the tartar 
deposited from the wine clogging the pores of the shavings 
or other porous material. 

Originally wine vinegar was made by the simple method 
of mixing wine with a little vinegar and exposing the 
mixture to the air in open casks. This primitive method 
was in use in some small factories, even in Orleans, as 
late as 1876, although most vinegar makers had long 
discarded it in favour of the " Orleans process/ 3 in which 
the acetification is effected in a series of casks of special 
construction provided with holes for the admission and 
outlet of air. 

These casks, which are termed " mothers," are ranged 
in tiers, as shown in the accompanying diagram, usually 
in an underground cellar, the temperature of which can 
be maintained at a fairly constant point, while the supply 
of air entering through the door-way can be regulated 
as required. The cellar is heated by means of a stove 
or hot-water pipes to a temperature which is never 
allowed to exceed 30 C. (86 P.). 

Prior to entering the acetifying casks the wine is filtered 
through a large vat containing shavings, which is known as a 
" wine-rape," while after acetification the vinegar is passed 
through a second rape, and matured in storage casks. 


The average quantity of vinegar produced by each 
cask in a month is only about 40 litres (8| gallons), and 
the expenses of manufacture range from about 3 to 
3J francs per hectolitre. 

The drawbacks of the Orleans process are that it is 

Fig. 32. Manufacture of Wine Vinegar, Orleans Process (after 

very slow, each cask yielding only 10 litres of vinegar 
per week, and that in consequence of this it is difficult 
to eliminate vinegar eels completely from the casks. 
From time to time the deposit of tartar which forms 


within the casks is removed, but this does not take place 
at sufficiently short intervals for the casks to be sterilised 
and freed from the eels. Moreover, even when one cask 
has been cleaned it speedily becomes infected again with 
eels from its neighbours a result which is much less 
likely to happen to acetifiers upon a larger scale. There 
is also a greater tendency in working with small casks 
for mother-of- vinegar to form, and to interfere with the 

On the other hand, the slow working of the Orleans 
process produces the esters to which French vinegar 
owes its reputation for aroma and flavour. 

Notwithstanding the investigations of Pasteur, which 
showed in what directions the Orleans process could 
be improved, there has been but little progress in the 
manufacture. The apparatus devised by Pasteur con- 
sisted of large shallow troughs with holes at the side 
for the admission of air. The amounts of vinegar with- 
drawn and of fresh wine added were regulated in accord- 
ance with the speed of acetification, so that the bacteria 
always had a sufficient supply of alcohol, and therefore 
did not attack the acetic acid. The wine was sterilised 
before acetification to destroy foreign organisms, while 
the finished vinegar was treated in the same way to ensure 
its keeping. 

Claudon's Apparatus. This plant was devised by 
Claudon to embody the principles of Pasteur's teaching 
while being practicable upon a manufacturing scale. 

It consisted essentially of a series of superposed shallow 
fermentation vessels C, C, C, in a square tank, about 
6 feet high, which was carried on stone pillars B. 

The bottom of each fermentation vessel formed the 


cover of the next one, while a floating box of special 
form was placed in each to keep the bacteria (My coder ma) 
at the surface of the liquid. 

In each fermentation vessel were ten openings E, five 
on each side, the admission of air through each being 
controlled by a movable glass panel. 

The wine was heated to a maximum temperature of 
55 C. in the vat H, whence it passed into the acetifying 

Fig. 33. ClaUdon's Acetifying Apparatus (after Franche). 

vessel, while the vinegar was drawn off into the vat L, 
and filtered through wire gauze filters with wool, which 
were contained in the vat N. Each tank A worked for 
about ten days before being cleaned and recharged. 

As in the original Orleans process, the alcoholic liquid 
(gyle) remained quiet, while its surface was exposed to 
the action of the air, and the advantage of this apparatus 


was that the shallow form of the fermentation vessels 
allowed much more exposure of liquid than was possible 
in ordinary casks. 

The "Quick" Process. The general introduction of 
the so-called " quick " process of acetification is attri- 
buted to Schiitzenbach, who introduced it into Germany 
in 1823. In all main essentials, however, the quick 
process is only a development of the method of aceti- 
fication used in certain wine-vinegar factories in France 
in 1670 (see p. 5). 

The main difference introduced by Schiitzenbach was 
the use of a vat instead of a cask as an acetifier, with 
mechanical means for the repeated distribution of the 
gyle over the acetifying medium. 

Until about sixty years ago both processes of acetification 
were in use in English vinegar works, part of the vinegar 
being prepared by fielding, and the remainder by stoving, 
as it was called. 

English Acetifiers. The main differences between 
English and German acetifiers are that the former are 
made upon a larger scale than the latter, and as they 
are used for acetifying an extract of grain rather than 
an alcoholic wash, must be provided with a larger supply 
of air. 

The acetifiers introduced into British vinegar works, 
at the time when the "stoves" replaced the vinegar 
fields, consisted of large vats taking a charge of 2,000 to 
3,000 gallons. 

About two-thirds of the way up a perforated false 
bottom was fixed, and the space above this was loosely 
packed with raisin stalks or shavings of beech wood, 
upon which the bacteria developed, while a current of 


air was admitted through a number of holes bored in the 
side of the vat below the false bottom. 

The gyle was distributed in a fine rain over the shavings 
by a revolving sparge, and running downwards encoun- 
tered the currents of air, which enabled the bacteria to 
acetify a small amount of the alcohol. 

The liquid collecting in the bottom of the vat was 
pumped up again into the sparge box, whence it was 
once more distributed over the shavings, and this process 
was continually repeated for two to three weeks, until 
nearly the whole of the alcohol had been converted into 
acetic acid. 

When freshly started these acetifiers worked very 
well, but the shavings soon became clogged by mother- 
of-vinegar, and where this happened the air was no 
longer evenly distributed throughout the acetifying 
medium, but made channels for itself. Hence some 
parts received an excessive supply of oxygen, whereas 
in other places there was a deficiency, and the practical 
result was that part of the alcohol was not oxidised 
beyond the stage of aldehyde, while another part was 
oxidised beyond the stage of acetic acid, and was lost. 

For these reasons shavings were replaced in many 
vinegar works by wicker basket work. This was much 
less liable to become clogged than the shavings, and allowed 
the air to circulate more regularly. 

A section of part of an acetifier constructed on these 
lines is shown in Fig. 34. 

Distribution of the Gyle. One of the most important 
factors in acetification is the distribution of the wash 
over the acetifying medium in the finest possible state 
of division. 


The most general method of effecting this division is 
by the use of the sparge. This is frequently constructed 
upon the same principle as the sparge used in the mash- 
tun (p. 80), but it is made of vulcanite or block tin, to 
resist the action of the hot acetic acid. 

In the largest acetifiers the sparge is often made of 
wood, and is in the form of a tapering box pierced by 
holes at the sides and with an open top to facilitate 
cleaning at intervals. 

G, Supply pipe from pump. R, R, The sparge. 

S, Perforated support. 

Fig. 34. Section of a Modern Acetifier with Basket Work. 

Such heavy sparges will not revolve by the force of 
the escaping liquid, and require to be driven by a cog- 
wheel, whereas in the case of the light vulcanite sparges 
the revolution is produced by the force of liquid. This 
has the advantage that any failure in the action is at once 
shown by the stoppage of an outside indicator attached 


to the sparge. On the other hand, the narrow tubular 
sparges are much more liable to become clogged with 
mother-of-vinegar than the large wooden box sparges, 
from which any accumulation of " mother " is often 
expelled by the force of the liquid. 

Fig. 35. Sparge of an Acetifier (Bronner). 

The Tipping Trough. An ingenious device for dis- 
tributing the wash over the surface of the acetifying 
medium is shown in Fig. 36. It consists of a wide-angled 
trough with a partition in the middle, so as to form the 
two compartments a and b. At the angle c there is an 


axis upon which the trough can swing either to the right 
or to the left as far as the stops d. The wash pumped 
from the bottom of the acetifier falls through the tap 
into one of the compartments until this is filled to a certain 
height. It then tips over and discharges the wash over 
the surface of the acetifying medium, while the empty 
compartment is at the same time brought beneath the 
tap to be filled and discharged in the same way. This 
process continues alternately, so that each side of the 
surface of acetifying medium is alternately flushed with 
a large volume of the liquid. 

With small acetifiers this device works admirably, 
but it is unsuitable for acetifiers of even moderately 
large dimensions, as the weight 
of liquid in the compartment is 
so great that in its sudden fall it 
produces a great strain on the 

Siphon Distributors. Another 
method of distributing the wash Y ^ 36.-Ti PP ing Trough 

.... , 1,1 (Bronner). 

is to pump it into a closed tank 

above the acetifier. In this tank is a siphon tube, the 
longer limb of which discharges the liquid into a tray 
pierced with numerous small holes within the acetifier, 
whence it trickles in fine streams over the shavings 
or basket work. 

The air required in the siphon tank is drawn from the 
space at the top of the acetifier, so that the aeration of 
the wash remains under control. 

In some apparatus a combination of the siphon tube 
and sparge is employed with the object of automatically 
regulating the supply of wash to the acetifier. This 


arrangement is shown in Fig. 37. The liquid pumped 
from the base of the acetifier is delivered into the small 
cask c, through the pipe ?>. When it reaches a certain 
level it is drawn over through the glass siphon d into 
the funnel e of the sparge /, and is thence distributed 
by the revolving arms g, g. The point on which the 
sparge revolves is shown at h, while i represents the 
cover of the acetifier, and k, k holes for the escape of 
the air. The flow of the wash into the acetifier can 

Fig. 37. Combined Siphon and Sparge. 

thus be readily controlled by regulating the opening 
of the cock at 6, and by raising or lowering the siphon 

Aeration Devices. The most simple method of supply- 
ing air to the acetifiers is by piercing a number of small 
holes in the sides of the vat below the false bottom that 
supports the acetifying medium. 

An effective arrangement is to have from 6 to 12 holes 
with a diameter of about f inch, and it is preferable to 



have glass tubes projecting from some of these into the 
interior of the vat. 

The object of this will be seen by reference to the 
accompanying diagram (Fig. 38), which represents a ver- 
tical section of an acetifier. The air entering through the 
holes at the bottom must tend to rise vertically upwards 
until it escapes through the openings b near the centre 
of the cover. There will thus be a large cone-shaped 
area A, where the aeration will be less complete than 

Fig. 38. Diagram showing Aeration of an Acetifier. 

at the outside B, B. This less active space becomes 
larger with the increase in the diameter of the vat, so 
that for this reason the aeration in small acetifiers is 
frequently more uniform than in larger apparatus. 

By passing tubes a foot or more into the interior through 
alternate holes, the aeration will tend to become more 
regular throughout the whole of the acetifying medium. 

Another way of aerating the interior is by means of 
an air tube in the bottom of the acetifier. This projects 


upwards nearly to the level of the false bottom, and is 
protected from the falling vinegar by a conical roof 
supported on a tripod (Fig. 39). The air escaping from 

Fig. 39. Aeration Device. 

Fig. 40. Aeration Tubes. 

the central tube is distributed by contact with this roof, 
and rises through the middle of the acetifier. 



The same end is effected by an aeration tube of the 
form shown in Fig. 40, in which holes for the escape 
of the air are provided beneath the conical cover. 

The outlets for the escape of the air should be of larger 
size than the inlets, and are preferably to be placed near 
the middle of the cover. Sliding shutters, which can be 
drawn across the top openings, enable the air supply to 
be regulated in accordance with the yields of acetic 
acid obtained from the alcohol in the wash. 

Each acetifier will vary in its 
speed of action and its uniformity 
of acetification, and it is, therefore, 
necessary to vary the conditions of 
aeration in every instance until 
satisfactory results have been 

The diameter of the outlet 
openings at the top ought to equal 
the sum of the diameter of the 
inlets at the sides. 

Wagenmann's Graduator. A form of acetifier working 
by the " quick process " was devised about 1830 by M. 
Wagenmann. This consisted of a small oak cask about 
5J feet high by 3J feet in diameter at the top. A -series 
of holes was pierced at about 15 inches from the bottom, 
for the admission of air, while the liquid to be acetified 
was poured in through a funnel at the top. At about 
5 inches from the lid of the cask a perforated shelf was 
fixed, and through each of the 400 holes cotton or hemp 
wick was suspended to guide the liquid downwards on 
to the beech shavings, with which the acetifier was 

packed. There were also four larger holes in this shelf, 


Fig. 41. Wagenmann's 


in which were fixed short glass tubes projecting above 
and below the wood. These were intended for the escape 
of the air admitted through the holes below. After 
acetification was complete the vinegar was drawn off 
through the siphon tube at the base. 

In this gmduator, with its suspended cords, we have 
the germ of the idea utilised in Luck's acetifier, in which 
the acetifying medium consists of bunches of cords 
stretched between the distributing tray and the false 

Singer's Apparatus. This is composed of a series of 
rectangular boxes, which are superposed above each 
other. In each of these is a series of wooden tubes packed 
with shavings or charcoal, and the wash is made to trickle 
through these successively from top to bottom, while 
air is admitted through ventilators at the sides and at 
the top. 

To prevent loss of heat, the entire apparatus is enclosed 
in a case with glass windows. 

It is obvious that the acetification surface is much 
too small for effective working, and that this apparatus, 
which is described in most of the foreign text-books, 
would be quite unsuitable for the manufacture of vinegar 
on a large scale. 

Bersch's Acetifier. An Austrian apparatus, which is 
claimed to give excellent results in practice, is shown in 
the accompanying figure (Fig. 43). The wash is siphoned 
over from the trough at the top, and slowly percolates 
through layers of superposed flat plates with narrow 
spaces between them. 

Although this acetifier is suitable for the acetification 
of small quantities of an alcoholic wash, such as is used 



in Germany and Austria, it could not be effectively 
used with a malt wash, since the spaces between the 
plates would become rapidly clogged with mother-of- 

Theoretically it offers a large superficial area for the 
growth of the bacteria, but the frequent cleaning that 

Fig. 42. Singer's Acetifier. 

Fig. 43. Bersch's Acetifier. 

it would require under English conditions of working 
would render its use unprofitable in this country. 


Whatever form of acetifier be employed, the conditions 
for economical working are essentially the same, and the 


superiority of one type of apparatus over another depends 
upon the extent to which these conditions are satisfied. 

Aeration. If it were possible always to supply the 
acetic bacteria throughout the whole of the acetifier 
with exactly the right amount of air,. the conversion of 
alcohol into acetic acid would under the normal con- 
ditions of working be theoretical ; but, as a rule, in 
practice, the aeration process is far from perfect, and 
considerable losses of alcohol and acetic acid take place 
owing to the admission of either too much or too little 

For example, in the old type of acetifiers, packed with 
beech shavings, the admission of air is by no means 
uniform throughout the material. In some places, where 
the mother-of- vinegar has fallen upon the shavings, the 
air passages become blocked and the acetification is 
incomplete, while in other places the air will pass more 
freely, and if present in too large proportion will lead to 
the oxidation of the acetic acid already formed. Hence 
all stages of oxidation will be taking place simultaneously 
in the acetifier, and the total result will be a reduced 
yield of acetic acid, the deficiency usually ranging from 
about 10 to 25 or 30 per cent., but sometimes reaching 
40 per cent, or more. 

The substitution of basket work for shavings, as is 
found in many of the English acetifiers, is a distinct 
improvement, since it causes the aeration to be more 
regular, and reduces the tendency to the formation of 
air channels, but this type of apparatus soon becomes 
clogged, and requires frequent cleansing if it is to work 

In some of the Continental types of acetifiers. 


in which the gyle is made to trickle through tubes, 
regular aeration is more possible, although some of 
these apparatus are hardly suitable for working under 
conditions in which the bacteria produce an excessive 
quantity of " mother/' 

The whole problem of successful acetification depends 
upon presenting the largest possible surface for the 
development and aeration of the bacteria in a uniform 
manner, and of preventing the air passages from becoming 
clogged through the development of the zoogloeal con- 
dition of the micro-organisms. The solution of the 
difficulty is not as simple as at first sight might appear, 
although some types of apparatus which the writer has 
had the opportunity of examining under working con- 
ditions undoubtedly give results very much nearer to 
theoretical requirements than do the average acetifiers 
used in this country. 

An important factor which must be taken into con- 
sideration is the relationship between the economy of 
acetification and the speed with which the acetifying 
medium becomes clogged. The better the results obtained 
in the acetification the sooner will the vat require cleaning, 
owing to the porous medium becoming clogged. For 
example, a packing of fine wicker-work will give good 
results at first, but after a month or so it gradually be- 
comes clogged and begins to work irregularly, and with a 
greater loss of acetic acid. It will then require cleaning 
and starting again, which in itself involves a loss of the 
acetic acid with which the basket work has become 

The same difficulty attaches 'to some of the " plate " 
acetifiers, in which the wash is acetified between 


narrow parallel surfaces. At first, these work very well, 
and allow the air to be evenly regulated through all 
parts of the acetifier, but under English conditions, at 
all events, they soon become coated with a slimy deposit, 
and must be cleaned again. 

Hence it is necessary to regulate the aerating surfaces 
in an acetifier in such a way that the loss of alcohol 
involved in working with a more open medium (e.g., 
basket work of wider mesh) is more than counterbalanced 
by the saving in labour effected by the less frequent 
cleaning of the acetifiers, which is then required. 

The Temperature. After regulation of the supply of 
air, the most important factor for the successful working 
of an acetifier is that the temperature should be kept 
within definite limits. 

It has already been shown (p. 42) that the optimum 
temperature for the acetification of alcohol varies with 
different species of bacteria, although in practice it is 
quite possible to acclimatise the micro-organisms to 
abnormal temperatures. 

On the Continent the species of acetic bacteria in 
common use work best at a much lower temperature 
than is usual in this country. Thus in some of the small 
German acetifiers the temperature is kept at about 
90 to 95 F., and acetification w r ould cease if the tem- 
perature rose much above 100 F. In England, however, 
the acetifiers work best at temperatures of about 105 
to 110 F., and the temperature can be brought still 
higher without injuring the bacteria. 

If small acetifiers providing a relatively large surface 
for aeration be employed, the temperature will rise 
spontaneously to the optimum point, but with larger 


quantities of gyle, or with acetifiers in which the aeration 
surface is relatively smaller, it is advisable to heat the 
liquid to about 70 F. before starting the acetification 

In the case of the largest acetifiers, taking a charge 
of 4,000 to 5,000 gallons, it is usual to heat the liquid 
in the acetifier itself by means of a steam coil at the 
bottom of the vat. For smaller acetifiers the preliminary 
heating is conveniently done in a tank (lined with block 
tin), fixed at a level above a series of acetifiers, into any 
of which it can be discharged when sufficiently heated. 

In the Continental factories the whole of the acetifying 
room is usually heated by means of a stove, and this 
course has the advantage that currents of cold air are 
prevented from entering the acetifiers and causing ir- 
regular acetification. 

After the initial heating of the gyle in English acetifiers 
the bacterial oxidation raises the temperature to a point 
which will depend to a large extent upon the amount of 
air supplied, so that the daily readings of the thermometers 
inserted into a hole in the side of the acetifier afford an 
index of the regularity of the acetification. 

If too much air is being supplied, the temperature will 
rush up very rapidly, and it will then be found that, not 
only is the alcohol being rapidly acetified, but that the 
acetic acid produced is also being oxidised. 

On the other hand, if the temperature rises very slowly, 
or even falls, insufficient air to promote the oxidation is 
being supplied, and the openings must be regulated 

One advantage possessed by the English in comparison 
with the Continental process is that the higher temperature 


checks the development of vinegar eels and their effects 
upon the oxidation (p. 124). 

It is very rarely that these organisms will develop in 
an acetifier in which the temperature exceeds 100 F., 
although it is interesting to note that, like the acetic 
bacteria, the vinegar eel can become gradually acclima- 
tised to higher temperatures. In the case of acetifiers 
working at about 90 F., it is difficult to prevent their 
appearance, unless special precautions be taken to use 
a sterilised wash, and to protect the air-holes of the 

On the other hand, the high temperatures that are 
required for rapid acetification cause loss of volatile 
products, especially aldehyde, through evaporation. To 
obviate this it is essential to prevent, as far as possible, 
the escape of air from the acetifying chambers, or 
" stoves," as they are termed by the workmen. 

Any outlet for the hot air at the top of the. building 
increases this loss, by allowing the volatile products to 
escape, instead of being gradually drawn back again into 
the acetifiers and further oxidised. 

The Group System. The strength of vinegar that can 
be obtained directly from the acetifiers is restricted by 
the fact that the bacteria are sensitive to the action 
both of strong alcohol and of acetic acid. Alcohol in the 
proportion of about 10 per cent, kills them, but long 
before that strength is reached their activity is checked. 
On the other hand, they offer much greater resistance 
to acetic acid, and do not reach their full vital activity 
until the acidity reaches about 2 per cent. 

On these facts is based the group system of acetification, 
which consists, in brief, of acclimatising the bacteria to 


thrive best under certain conditions of alcoholic and 
acetic strength. 

It is not possible to produce a 12 per cent, vinegar 
directly from one acetifier, since the proportion of alcohol 
required would be fatal to the bacteria. Hence, in the 
production of concentrated vinegars, such as Essigsprit, 
the acetification is carried out in three groups of acetifiers. 
The first of these is charged with a wash capable of 
yielding about 6 per cent, of acetic acid. The vinegar 
leaving these is fortified with an alcoholic wash (usually 
potato or grain spirit), in sufficient quantity to yield a 
vinegar of 9 to 10 per cent, strength in the second group 
of acetifiers, while in like manner the vinegar from these 
is again fortified before being transferred to the third 
group of acetifiers, where the acetification is completed. 

Such a method of working is only possible where a 
strong alcoholic wash is obtainable. 

Disturbances due to Mother-of-Vinegar. However care- 
fully the supply of air to the acetifiers and the tempera- 
ture are controlled, it is impossible to prevent a gradual 
accumulation of mother-of- vinegar upon the baskets or 
porous packing in the vat. When once this " tripe," 
as the workmen term it, begins to form, the proper supply 
of air is checked, and under these conditions the growth 
of the mother-of -vinegar increase still further. 
-. The formation of this remarkable zooglceal condition 
of the bacteria (see p. 34) appears to be promoted by 
the presence of a limited supply of air. 

For example, if a bottle of freshly-made vinegar be 
tightly corked no alteration beyond a slight deposition 
of albuminous matter will take place, but if the cork 
be slightly loosened so that a trace of air gains admission 


to the liquid, a succession of solid gelatinous wads will 
form in the neck, and eventually fall to the bottom. 
This is commonly described as the vinegar " becoming 
mothery," and is the cause of occasional complaints. 
It is completely cured by sterilisation (see p. 132). 

The Vinegar Eel. As is mentioned above, one of the 
greatest troubles with which the vinegar maker has to 
contend is the minute animal known as the vinegar eel. 

There are numerous references to it in scientific litera- 
ture, one of the earliest being in the Philosophical Essays 
of Robert Boyle (1661) : "We have made mention to 
you of a great store of living creatures which we have 
observed in vinegar ; of the truth of which observation 
we can produce divers and severe witnesses, who were 
not to be convinced until we had satisfied them by ocular 
demonstration ; and yet there are divers parcels of 
excellent vinegar wherein you may in vain seek for these 
living creatures, and we are now distilling some of that 
liquor, wherein we can neither by candle light nor by 
daylight discern any of these little creatures, of which 
we have often seen swarms in other vinegars." 

The occurrence of eels in vinegar did not escape the 
notice of Leeuwenhoeck, who has the following amusing 
reference to them * : '' I have also described a full- 
grown live eel, such a one whereof there were many more 
in the vinegar. I cannot but take notice how some men 
are deceived that think of the sourness of vinegar proceeds 
from eels pricking their tongues with their tails, for if 
this were true, then would some vinegar be flat because 
there are no eels in it, or rather eels are dead in it, as is 
usual in cold or frosty weather/' 

* Trans. Roy. Soc., 1685, xv., 965. 


The organism to which these statements refer is the 
Leptodera oxophila, and appears to be identical with the 
" eels " that will develop in sour paste. 

It is of very frequent occurrence in Continental vinegar 
works, where the vinegar is manufactured at a lower 
temperature than is usual in England. According to 
Czernat, it may be introduced into the vinegar from the 

Fig. 44. Vinegar Eels (Pasteur). 

water, but it is much more probable that it is derived 
from the air. 

Occasionally when vinegar is exposed to the air for 
a short time it will swarm with these creatures, and the 
same thing may happen in an acetifier, so that every 
drop of the vinegar has the appearance shown in Fig. 44. 


The structure of the vinegar eel is very simple (Fig. 45), 
the body is cylindrical, and ends in a sharp point, and 
the skin, which is changed from time to time, is smooth, 
structureless, and very strong. According to Czernat's 
average measurements, the length of the male's body is 
about ^g. inch, and that of the female about ^ inch. 

Vinegar eels move either backwards or forwards, and 
progress by alternately shaping themselves into an S 
and straightening out again. They appear to be in- 
cessantly darting through the vinegar in all directions, 
but always with a tendency towards the surface, for 
they are air-breathing animals. 

Fig. 45. Vinegar Eel, highly magnified (Pasteur). 

They are capable of living in very dilute alcohol or 
acetic acid, as well as in vinegar, and can resist great 
variations in temperature, not being killed until the 
temperature reaches 140 to 150 F. in one direction or 
22 F. in the other. 

Pasteur* was the first to point out how harmful the 
vinegar eel was in the manufacture of vinegar. Should 
they develop within an acetifier a struggle for air begins 

* Loc. cit. 


between them and the acetic bacteria. For a time a 
working balance may be struck between them, and the 
air shared ; but during this struggle, which may last for 
weeks, the activity of the bacteria is impaired, and though 
the conversion of alcohol into acetic acid still proceeds, 
it does so with an increased expenditure of time and a 
reduced yield. 

Should the vinegar eels gradually obtain the upper 
hand, they interfere more and more with the working 
of the apparatus, and eventually the acetification comes 
to a standstill. If, on the other hand, the bacteria get 
the mastery, they tend to deposit " mother " on the 
surface of the liquid, as the result of their obtaining 
insufficient oxygen. This skin effectually prevents the 
eels from breathing when they come to the surface, and 
so they perish and fall to the bottom of the acetifier, 
where they accumulate as a white deposit and may 
putrefy. In either case the only remedy is to clean and 
disinfect the apparatus and start afresh. 

It was only with difficulty that Pasteur could convince 
certain French vinegar makers of the advantage of getting 
rid of the vinegar eel, for so general had it become with 
them that they had begun to look upon it as an essential 
part of the process instead of a deadly enemy. 

Even after vinegar containing eels has been freed from 
them by nitration the ova remain, and under suitable 
condition will develop into eels, which will rapidly multiply 
and make the vinegar appear turbid, though without 
materially affecting its acetic strength. This after- 
development of eels is easily prevented by heating the 
vinegar to 160 F. in a sterilising apparatus, as described 
on p. 133. 


The Vinegar Mite. Another enemy of the acetic 
bacteria is known as the " vinegar mite." When once 
it obtains a footing within an acetifier it multiplies 
rapidly, interferes with the oxidation, and is not easily 
exterminated. Bersch records a case that came under 
his observation. The vinegar made in a certain Italian 
factory swarmed with these mites, which had finally 
brought the acetification to a complete standstill. The 
manufacturers attributed their presence to the soil below 
the acetifiers, but had no idea that they pointed to a 
want of care. 

It is through the aeration holes in the acetifiers that 
the mites gain access to the apparatus, and attempts 
have been made to prevent this by placing bird-lime 
round the outside of the holes, while in some of the 
more recent patents fine wire gauze is used for the same 

At first the acetic bacteria do not appear to be much 
affected by the presence of the mites, but as these increase 
.and then die and fall to the bottom their dead bodies 
begin to putrefy, and the putrefactive bacteria will sooner 
or later master the acetic bacteria. 

The vinegar in which the mites have gained the upper 
hand has a peculiar yellowish shade, and contains what 
.appear to the naked eye to be fine white specks. 

When examined under the microscope these have the 
appearance shown in Figs. 46 and 47. 

These two forms, apparently those of the male and 
iemale, are always present. They appear to belong to 
the class of Sarcoptidce. 

When once vinegar mites have become established 
within an acetifier, they can only be expelled by destroying 



them simultaneously with the acetic bacteria. For this 
purpose the vat must be emptied, and the interior thor- 
oughly washed with hot water, then well fumigated with 

Fig. 46. Vinegar Mite (Bersch). 

Fig. 47. Vinegar Mite (Bersch). 


burning sulphur until all life is destroyed, and again 
washed. It is then recharged with gyle and a little crude 
vinegar containing the bacteria, but it will be some time 
before the acetifier gets into working condition again. 

The Vinegar Fly. The vinegar fly (Drosophila funebris) 
is of very common occurrence, and may be observed in 
any vinegar works during the hotter months of the year. 
It is about one-tenth of an inch in length, and is character- 
ised by its large red eyes, red thorax, and red legs. The 
abdomen is black with yellow stripes, and the wings are 
somewhat longer than the body. According to Brannt, 
the larva is white, has twelve segments to its body, and 
four wart-like structures on the back. After eight days 
it is transformed into a yellow chrysalis. 

Vinegar makers are not in the habit of paying much 
attention to the presence of the vinegar fly, since, so far 
as is known, it does not in any way affect the manu- 
facture, and it is readily prevented from becoming a 
nuisance by keeping the works thoroughly clean and 
not allowing any spilt vinegar to lie about upon the 



Filtration Clarification Action of Ferrocyanide Sterilisation Storage- 
Distillation Composition of the Residue in the Still. 

Filtration of Vinegar. After leaving the acetifiers, the 
crude vinegar is pumped into store vats, where it is allowed 
to remain for several weeks or months to mature. During 
this storage period it deposits albuminous matter, bac- 
terial cells, etc., and undergoes partial clarification. 
In fact, the longer the vinegar can be stored the more 
readily can it subsequently be made sufficiently " bright " 
for sending out. The filters used in vinegar factories are 
technically known as " rapes/' owing to the fact that 
raisin stalks or rapes were first used for the purpose in 
the seventeenth century (see p. 6). The spent raisin 
skins left as a residue in the manufacture of British 
wines are still sometimes used for this purpose, although 
as a rule the filter bed is generally composed of other 
filtering media, such as beech chips, in conjunction with 
layers of shingle, sand, or kieselguhr. 

Paper pulp is also used for filtering vinegar, and has 
the advantage of yielding a brilliant filtrate, although it 
soon becomes clogged, and offers difficulties in the case 
of vinegar which has not been stored for a long time. 

The general appearance of the inside of a " rape " 
shed is shown in Fig. 48. 


The large vats, each of which takes a charge of about 
3,000 to 4,000 gallons, are arranged in rows down the 
sides of the shed, and each is provided with its own pump, 
and mains, so that the vinegar can be pumped into any 
of them at will. 

The filtering medium is supported upon a false bottom 
some distance up within the vat, so that a vertical section 
of a " rape " shows two layers of liquid separated by the 
filtering medium. 

It is a common practice for the " rapes " to be worked 
in groups. The vinegar from the store vats is introduced 
into the first group, and is there continually pumped 
over and over, until it is bright enough to be passed on 
to the second group of rapes. There the same process 
is repeated until the vinegar is nearly brilliant, and the 
filtration is then completed in the third group of rapes, 
which should yield a product described by the workmen 
as " candle-bright/' 

When the vinegar has been brewed from a low-dried 
malt, or when much raw grain has been used, it is extremely 
difficult to remove the last traces of suspended matter, 
and the vinegar will continue for a long time to show a 
characteristic silken opalescence, which might escape 
notice in ordinary daylight, but is very obvious when 
the bottle is held up to an artificial light. 

Clarification of Vinegar. The persistent cloudiness 
which occurs in certain vinegars is sometimes more 
rapidly removed by a process of clarification than by 
filtration. The methods employed are sometimes mechani- 
cal and sometimes chemical. In the first case an in- 
soluble substance, such as Spanish earth or kieselguhr, is 
stirred up with the vinegar, and as it subsides it carries 


clown with it the albuminous particles to which the 
turbidity is due. 

In the chemical methods the albuminous substances 
may be precipitated by the addition of a " gelatinous 
agent, such as isinglass, or a measured quantity of a 
solution of potassium ferrocyanide may be added. 

Precipitation with Ferrocyanide. This reagent will 
precipitate, not only a portion of the nitrogenous com- 
pounds, but also any iron in the vinegar, and the vats 
in which the precipitation is carried out are usually 
stained dark blue from the formation of Prussian blue. 

It is essential, however, that no excess of ferrocyanide 
should be used, and on more than one occasion vinegar 
containing such excess has caused a bright blue colour 
to appear in pickles which had been preserved in brine 
containing a trace of iron. 

The behaviour of potassium ferrocyanide in vinegar 
was investigated by Harden.* It was found that the 
oxidation which took place spontaneously in an aqueous 
solution of potassium ferrocyanide also occurred when the 
salt was dissolved in dilute (6 per cent.) acetic acid, a 
deposit of Prussian blue being formed, while hydrocyanic 
acid was liberated in accordance with the equation 

7H 4 Fe(CN) 6 + 2 = 24HCN + 2H 2 O + Fe(CN) 18 . 

The hydrocyanic acid thus produced disappeared very 
slowly from the acetic acid, the amount being but slightly 
reduced after the liquid had stood for a month. 

When, however, the ferrocyanide was added to vinegar, 
some further reaction apparently took place, for although 
the deposit of Prussian blue was obtained, it was not 

* Dr. Hamill's Report to L.G.B., 1908, p. 27. 


possible to detect hydrocyanic acid in the filtrate from 
that deposit. Possibly it had entered into combination 
with the aldehyde of some other constituent of the vinegar, 
and this explanation of the failure to detect it received 
support from the results of experiments, which showed 
that hydrocyanic acid did actually combine with some 
substance in vinegar to form an unstable compound, 
which was decomposed when the vinegar was heated. 

Although no definite proof was obtained of the forma- 
tion of hydrocyanic acid when an excess of ferrocyanide 
was added to vinegar, the evidence pointed to its pro- 
duction, and justified the conclusion that such vinegar 
should be looked upon with suspicion. 

Sterilisation of Vinegar. After filtration or clarifica- 
tion, vinegar will still contain acetic bacteria or their 
spores, and when exposed to the air will soon become 
coated with a zooglceal film. When the vinegar is sent 
out in casks, and the consumers allow air to gain access 
to it, by not replacing the spigot, this growth of the 
bacteria will occur upon the surface and make the liquid 
turbid. In other words, the casks become " mothery." 
The same thing happens in the case of bottled vinegar 
when the stopper is defective and allows air to enter 
the bottle. 

Long continued storage of the vinegar before sending 
out will check this growth of " mother/' as a large pro- 
portion of the bacteria will die when the vinegar is kept 
for some months in a well-closed vat. Want of space, 
however, may prevent this from being practicable in 
many cases, and at best it is not as effectual as sterilising 
the vinegar. 

As all the species of acetic bacteria perish at a 


relatively low temperature, it is sufficient to heat the 
vinegar to 150 F., to insure its keeping, even when 
exposed to the air, since the acetic acid will prevent the 
development of micro-organisms from without. This 
process of sterilisation is most simply effected by passing 
the vinegar through a coil surrounded by a tank of 
water, which can be heated by steam to the sterilising 
temperature. On leaving this heating tank the vinegar 
is passed through one or (preferably) two other coils 
chilled by a current of cold water, and is thus cooled down 
nearly to the normal temperature, and leaves the sterilising 
apparatus without any appreciable loss of acetic acid. 

The construction of the steriliser will be understood 
by reference to the accompanying diagram, in which 
A represents the feeding tank into which the vinegar 
is pumped, to give it sufficient height to flow through 
the apparatus. The heating tank is shown at B, and 
the cooling tanks at C, the temperature of the vinegar 
as it leaves -B and G being indicated by thermometers 
in the vinegar main at the points e and /. 

The flow of vinegar is regulated by the cock g, until 
the temperature shown at the point e is not less than 
150 F. while the temperature of the vinegar leaving the 
cooling tank should not exceed 70 to 75 F. at the point /. 

Sterilisation in this way causes a slight deposition of 
albuminous matter after the vinegar has stood for some 
time, and for this reason it is advisable to run the sterilised 
vinegar into storage vats, and to leave it for a few days 
before bottling. This is not so important in the case of 
cask vinegar, since the slight deposit will not be notice- 
able, and when once it has subsided does not affect the 
permanent brightness of the liquid. 


In addition to its action in improving the keeping 
qualities, sterilisation has also the effect of maturing 
the vinegar, and of giving a softer taste and less acid 
aroma. It is probable that this is due to its promoting 
the combination of the residual alcohol in the vinegar 
with the acetic acid, and thus accelerating the forma- 

A, Small round into which 

vinegar is pumped. 

B, Heating cylinder. 

C, Cooling cylinder. 

D, Steam pipe. 

Fig. 49. Diagram of Sterilising Apparatus. 

E, Cold water main. 

F, Outlet for water. 

G, Outlet for vinegar. 
T, T, Thermometers. 

tion of the esters to which matured vinegar owes its 



Distillation of Vinegar. The early method of distilling 
vinegar to obtain aromatic or radical vinegar has already 
been described (p. 63). The drawback to a simple dis- 
tillation at the ordinary pressure is that it is not possible 
to expel the acetic acid without at the same time over- 
heating the solid matter in the vinegar, so that empy- 
reumatic products are also distilled. Hence the early 
process was not economical, for a large proportion of 
the acid had to be left behind with the residue in the 

In the modern process the vinegar is distilled at a lower 
temperature under reduced pressure, and the distillation 
can then be carried very much further without any risk 
of burning the solid residue. 

The small stills commonly used take a charge of about 
100 gallons of vinegar. They are made of tin, and are 
heated by a steam jacket. The outlet pipe of the still 
is connected with a coil immersed in a tank of running 
water, and this delivers into a receiver, in which is a 
pipe connected with a vacuum pump. Distillation is 
effected at a reduced pressure of 15 to 20 inches, and is 
continued until the still contains only a semi-solid mass 
resembling treacle. Fig. 50 shows one of the vinegar 
stills used in the works of Messrs. Beaufoy & Co. 

By interrupting the distillation at definite points it 
is possible to obtain distillates of considerably higher 
strength than the original vinegar. For example, if a 
6 per cent, vinegar be distilled, the first third of the dis- 
tillate will contain about 3 per cent, of acetic acid, the 
second third about 5-5 per cent., and the final third 
between 9 and 10 per cent. 

The residue will also retain a small proportion of 


acetic acid, while the other constituents of the malt and 
grain will be present in a concentrated form. The still 
residue, in short, is a dark malt extract, slightly acid, 
and devoid of any diastatic capacity. 

Analyses of two samples of still residues made by 
Allen * gave the following results : 

From Barley 

From Kice and 
Grain Vinegar. 

Per cent. 

Per cent. 

Total solids, . * . . - 



Ash, . . . . . 



Alkalinity of ash (K 2 0), . . ' 



Phosphoric acid, 



Nitrogen, . . ..-.' 



The distillate is sold under the names of distilled malt 
vinegar, white vinegar, and white wine vinegar, while it 
has been held by a Sheriff in Fife that distilled malt 
vinegar may legally be sold as " malt vinegar/' 

* Analyst, 1893, xviii., 241. 



DETERMINATION OF ACIDITY Automatic Supply Burette Standardisation 
of Alkali Solutions Salleron's Ac6timetre Otto's Acetometer 
Standards of Acidity Crude Pyroligneous Acid TOTAL SOLIDS 
Alkalinity of the Ash MINERAL ACIDS Detection Determination 
Combined Sulphuric Acid Methyl-acetol FORMIC ACID TOTAL 
Intensity Lovibond's Tintometer Caramel Cochineal Archil 
METALLIC IMPURITIES Iron Copper Lead Tin Arsenic Official 
Method of Testing for Arsenic. 

Determination of Acidity. The acidity of most ordinary 
vinegars may be accurately determined by titration with 
standard sodium hydroxide solution, with phenolphthalein 
as indicator. In the case of very dark samples dilution 
is necessary, or the caramel may be precipitated with 
fuller's earth, and an aliquot part of the filtrate titrated. 
" Spotting " tests with litmus paper as indicator have 
been shown by Erode and Lange * to give results about 
1 per cent, lower (in terms of f alkali solution) than 
direct titration with phenolphthalein as indicator. Hence, 
litmus is less reliable than phenolphthalein as an indicator 
for vinegar. 

Where numerous samples require titrating every day, 
as in checking the working of acetifiers, it is advisable 

* Arbeit. Kaiserl Gesundheitsamt, 1909, xxx., 1. 


to use a special stock alkali solution, with an automatic- 
supply burette, wfth a guard to prevent absorption of 
carbon dioxide. 

Standardisation of Alkali Solutions. The most rapid 
method of standardising an alkali solution is by the use 
of pure oxalic acid. The ordinary " pure " chemical 
usually requires further purification for this purpose. 
This may be readily effected by shaking the crystals 
with warm water in insufficient quantity to dissolve 
them completely, filtering the solution, and 
leaving the filtrate to crystallise. The new 
crop of crystals is dried with filter paper at 
the ordinary temperature, and kept for use 
as an original standard. 

Salleron's Ac6ti metre. The instrument 
used by the French excise officials (and by 
the Customs officers in Mauritius) for esti- 
mating the acetic strength of vinegar is a 
simple glass tube closed at one end and 
graduated into divisions. The first of these, 
starting from the bottom, is marked with 
the word " Vinaigre," and indicates the 
Fig. 51. quantity of vinegar (4 c.c.) to be taken for 

Salleron's the test 
Acetimetre. . . 

Ihis quantity ot vinegar is introduced by 
means of a 4 c.c. pipette, a drop of phenolphthalein solu- 
tion added, and then successive small quantities of a 
standard solution of sodium hydroxide,* the tube being 
closed with the thumb and shaken each time until a 
permanent pink coloration is obtained after the addition 

* Twenty c.c. neutralise 4 c.c. of dilute sulphuric acid (100 grammes of 
monohydrated acid diluted to 1,000 c.c.). 


of a single drop. The strength of the vinegar may then 
be read directly upon the scale. For acids above 25 per 
cent, hi strength corresponding dilution is necessary. 

An instrument of a similar kind, known as Otto's 
acetometer, is used by the Customs officials in Germany, 
while a more accurate tube has been devised by Dujardin. 

This method of determining the acidity of vinegar is 
only capable of giving rough estimations, although, on 
the whole, these are much nearer the truth than the 
results given by the old acetometer of the British Excise 
(p. 15). 

Standards of Acidity. The standard for the minimum 
strength of vinegar adopted in 1877 by the Society of 
Public Analysts has already been mentioned (p. 61). 
Although this limit had no legal sanction, it was generally 
accepted by the trade, and convictions for " watering " 
were from time to time obtained for the sale of vinegar 
containing less than 3 per cent, of acetic acid. 

In May, 1912, the Local Government Board recom- 
mended that no vinegar or artificial vinegar should be 
sold containing less than 4 per cent, of acetic acid. 

Since the Local Government Board has no power, 
without fresh legislation, to fix standards, it is question- 
able whether the action taken by certain public authori- 
ties against the vendors of weaker vinegars would be 
supported if an appeal were made from the convictions 
obtained in several instances. 

So clearly is this recognised in some quarters that 
certain boroughs have refused to prosecute the vendors 
of weak vinegar, and have urged that combined action 
should be taken in petitioning for the necessary powers 
to be conferred upon the Local Government Board. 


Several of the Colonies have fixed limits for the strength 
of the vinegars which may be sold within their jurisdiction. 

The question of strength is also taken into account 
in charging duties upon vinegar imported into the different 
countries, and is thus frequently brought to the notice 
of English manufacturers. 

A list of the principal Colonial tariffs for vinegar and 
acetic acid will be found in Appendix I. 

Estimation of the Strength of Pyroligneous Acid. The 
titration of crude pyroligneous acid presents considerable 
difficulty, owing to the deep colour of the liquid preventing 
the end-point of the reaction being seen. 

The strength may be approximately estimated by 
Mohr's method, in which a weighed quantity of the acid 
is stirred with a weighed quantity of barium carbonate 
until effervescence stops, after which the undissolved 
barium salt is separated, washed, dried, and weighed. 
The acids will correspond to the amount of barium 
carbonate dissolved, and are calculated as acetic acid. 
Or the undissolved carbonate may be determined by 
titration with standard nitric acid. 

Total Solid Matter. Usually a measured quantity 
(10 c.c.) of the vinegar is evaporated on the water-bath 
with frequent shaking, and the residue dried in the 
water-oven until constant in weight. The shaking of 
the dish during the evaporation accelerates the expulsion 
of the acetic acid, which is obstinately retained by the 
solid matter. Thus, it was shown by Erode and Lange * 
that a wine vinegar when evaporated without shaking 
left a residue of 0-79 per cent, containing 0-2 per cent, 
of acetic acid, while when the dish was frequently shaken 

* Arbeit. Kaiserl. Gesundheittamte, 1909, xxx., 1. 


the residue was 0-64 per cent., and contained only 0-08 per 
cent, of acid. 

In any case, titration of the acidity of the residue and 
deduction of the result from the amount obtained by 
weighing is a necessary correction. 

An approximate estimation of the total solids, accur- 
ate within about 0-1 per cent., may be rapidly made by 
titrating the acidity, and determining the specific gravity 
of the vinegar at 15 C. by means of a standard Bates* 

From the specific gravity thus indicated the amount 
corresponding to the acetic acid strength at 15 C. is 
found by reference to Oudemanns' table (p. 75). 

The difference will show the specific gravity due to the 
solid extract from the wort, and the amount of the latter 
may be found by reference to the subjoined table (p. 142), 
which is abridged from Schultze's long table. 

The following example may be given by way of illus- 
tration : 

A sample of malt vinegar had a specific gravity of 
1-014 at 15 C. and an acidity of 4-5 per cent. This 
degree of acetic acid corresponds to a specific gravity of 
1-006 ; while the specific gravity due to the solid extract is 
10-14 0-006 = 1-008. A specific gravity of 1-008 repre- 
sents 2-09 per cent, of total solids in Schultze's table, while 
the amount determined by evaporation was 2-07 per cent. 

Alkalinity of the Ash. In some cases an indication of 
the probable origin of a vinegar may be obtained by 
determining the alkalinity of the ash, since in a vinegar 
brewed from glucose the mineral acid used for the hydro- 
lysis will have combined with part of the bases, and thus 
cause the proportion of potassium oxide to be low. 



Gravity at 

15 C.C. 

Extract in 
100 Griris. 

Extract in 
100 c.c. 

Gravity at 
15 c.c. 

Extract in 
100 Grms. 

Extract in 
100 c.c. 
























































































































































In the United States' official definition of malt vinegar 
it is enacted that the ash from 100 c.c. of the sample 
shall require for its neutralisation not less than 4 c.c. 
of decinormal acid. 

Actual determination of the potassium oxide 
as practised by Tatlock usually affords a more 
satisfactory criterion than the titration of the 

The variations in this figure in different kinds of vinegar 



may be illustrated by the following results given by 
Allen * : 


Grain and Malt. 

Grain and Sugar. 



Alkalinity as KoO^j 
per 100 parts of j- 

0-091 to 0-118 





Hilger's Method. Free mineral acids in vinegar may 
be detected by means of a solution of methyl violet 
(0-1 grm. per 1,000 c.c.), which is not affected by acetic 
or other organic acids, but is changed to blue or green 
by mineral acids. The test is best applied by adding 
4 to 5 drops of the reagent to 20 c.c. of the vinegar, 
shaking the tube and comparing the colour with that 
obtained with dilute acetic acid coloured to the same 
intensity with caramel. 

Congo-red paper is also useful as a preliminary test, 
being changed to blue by free mineral acids, though it is 
not affected by acetic acid. 


Hilger's Method. Twenty c.c. of the vinegar are neut- 
ralised with N/alkali solution, with turmeric paper as 
indicator, and evaporated to about 2 c.c., and the residue 
is mixed with a few drops of a 0-01 per cent, solution of 
methyl violet 2 B and 4 c.c. of water. The liquid is 
heated to boiling point, and titrated with N/sulphuric 
acid until the colour changes to blue or greerr. It is 

* Analyst, 1894, xix., 15. 


advisable to compare the change of colour with that 
given by an aqueous solution of the methyl violet con- 
taining about the same quantity of caramel as the vinegar 
in question. 

The difference between the number of c.c. of N /alkali 
solution originally used and the number of c.c. of sulphuric 
acid required in the last titration corresponds to the 
amount of free mineral acids present. The result multi- 
plied by 1-225 gives the percentage in terms of sulphuric 


The amount of free sulphuric acid (0-1 per cent.) which 
was expressly permitted to be added to vinegar by the 
Act of George III. of 1818 was often considerably 
exceeded. Thus, in the year 1852, a body of Commis- 
sioners appointed by the Lancet * examined 27 samples 
of vinegar typical of the products of the principal manu- 
facturers in this country. The samples of only two 
makers were found to be quite free from sulphuric acid, 
while the others contained from 0-63 to 6-02 parts per 

These figures, however, included sulphuric acid present 
in the form of sulphates, the proportion of combined 
acid ranging from 0-44 to 0-39 part per 1,000, so that 
many of the samples were well within the legal limit 
for free acid. 

At the present time it is improbable that any manu- 
facturer in this country adds free sulphuric acid to his 
vinegar, although, as may be gathered from Muspratt's f 

* Lancet, Aug. 28, 1852. 
f Dictiowry of Chemistry, 1860, p. 16. 


account, the practice died very slowly. It is perhaps 
hardly necessary to add that vinegars of sufficient acetic 
strength will keep quite well without any such addition. 

Hehner's Method. A method of detecting and esti- 
mating free sulphuric acid and other mineral acids in 
vinegar was based by Hehner * upon the fact that 
potassium and sodium acetates (or tartrates) are always 
present in vinegar. If a small amount of a mineral acid 
is added, it will decompose a corresponding quantity of 
acetate or tart rate, with the liberation of the organic 
acid, but if added in excess of the corresponding quantity 
of organic salts this excess will remain as a free acid. 
Hence, vinegars that contain acetates or tartrates cannot 
contain a free mineral acid, and since on igniting these 
organic salts they are decomposed into carbonates, an 
examination of the ash of the vinegar may afford an 
indication of the presence of free mineral acid. 

If the ash is alkaline, it is probable that no free mineral 
acid has been present in the vinegar, although a quantity 
insufficient to decompose the whole of the acetates or 
tartrates might originally have been added, and it is 
possible for calcium sulphates or other calcium salts to 
be decomposed in the ignition, and to render the ash 
alkaline ; but if the ash is neutral the presence of free 
mineral acid is probably indicated. 

Estimation of Free Acid. Hehner 's method will also 
give quantitative results. Fifty c.c. of the vinegar are 
evaporated with 25 c.c. of sodium hydroxide solution, 
and the residue charred at a low temperature, mixed 
with 25 c.c. of -g- sulphuric acid, boiled, filtered, and 
washed. The filtrate is titrated with |> sodium hydroxide 

* Analyst, 1877, i., 105. 



solution, with litmus or cochineal as indicator. The 
number of c.c. of alkali required corresponds to the free 
mineral acid. 

Owing to the necessity of repeating the estimation if 
the amount of alkali originally added was insufficient, 
Allen and Bodmer * modified the test by neutralising 
the whole of the acid present in the vinegar prior to the 

In the case of vinegars, such as those derived from malt 
or grain, which contain a large proportion of phosphate, 
it is necessary to take into consideration the fact that 
any phosphoric acid liberated in the test will react with 
alkali (methyl-orange as indicator) in a different way than 
hydrochloric or sulphuric acid. The importance of this 
point has been emphasised by Richardson and Bo wen. j- 

On boiling potassium phosphate, K 3 P0 4 , with a definite 
excess of sulphuric acid, potassium sulphate and phos- 
phoric acid are produced, but on titrating the excess of 
sulphuric acid, different results are obtained when methyl- 
orange and phenolphthalein are used as indicators. 

The end point of the reaction is reached, with methyl- 
orange as indicator, when dihydrogen potassium phos- 
phate has been formed i.e., only one- third of the phos- 
phoric acid present is shown. On now adding phenol- 
phthalein the titration can be continued until dipotassium 
hydrogen phosphate is formed, accounting for another 
third of the phosphoric acid. 

Richardson and Bowen's Method. Based upon these 
considerations, Richardson and Bowen (loc. cit.) have 
devised the following process, which estimates, not only 

* Analyst, 1878, iii., 268. 

t J. Soc. Chem. Ind., 1906, xxv., 836. 


the sulphuric acid present as such, but also the phosphoric 
acid liberated from the phosphates by the sulphuric acid. 
Although part of the phosphoric acid is present as calcium 
phosphate, no material error is introduced by basing the 
calculation upon potassium phosphate. 

Twenty-five c.c. of the vinegar are evaporated to 
dry ness with 25 c.c. of ^r sodium hydroxide solution, 
and the residue charred at a temperature insufficient to 
fuse the ash. The black mass is cooled, treated with 
hydrogen peroxide (to prevent liberation of hydrogen 
sulphide), and boiled with 50 c.c. of -g- sulphuric acid. 
The filtrate and washings are titrated with ^- sodium 
hydroxide solution with methyl-orange or lacmoid (pre- 
ferably the latter) as indicator. The liquid is then boiled 
with a few drops of - sulphuric acid to expel carbon 
dioxide, the acid neutralised with -j$- alkali solution, and 
the titration with -^- sodium hydroxide solution com- 
pleted after the addition of phenolphthalein. 

To account for the remaining third of unneutralised 
phosphoric acid twice the number of c.c. of standard 
alkali used in the final titration are taken for the calcu- 

The results obtained by this method, and by Hehner's 
method with vinegars containing known quantities of 
added sulphuric acid, were as given in table on p. 148. 

The difference between the two sets of results was 
attributed to the influence of the carbon dioxide on the 
methyl-orange, which caused the results to be too high. 

By this method of Richardson and Bowen the amount 
of sulphuric acid originally added is shown, whereas 
Hehner's method gives that actually present in the 
vinegar at the time of analysis. 


Sulphuric Acid 

With Methyl Orange. 

With Lacmoid. 


and Bowen's 


and Bowen's 

Per cent. 
A, 0-098, 
B, 0-049, 
C, nil, . 

Per cent. 
+ 0-033 
- 0-033 

- 0-080 

Per cent. 
+ 0-099 
+ 0-064 
+ 0-023 

Per cent. 
+ 0-0216 
- 0-045 
- 0-098 

Per cent. 
+ 0-099 
+ 0-045 
-f 0-004 

Combined Sulphuric Acid. The proportion of sulphuric 
acid in the form of sulphates in vinegar varies consider- 
ably, as will be seen from the following analyses, made 
by the writer, of the vinegars of six of the leading manu- 
facturers : 

A, 0-03 per cent. 

B, 0-10 

C, 0-032 

D, 0-155 per cent. 

E, 0-170 

F, 0-021 

The vinegars B, D, and E were made by the inversion 
process, while the other three were mash- tun products. 

An attempt was made some years ago to condemn 
vinegars containing more than 0-03 per cent, of combined 
sulphuric acid, and several prosecutions were initiated.* 

Although the amount of combined sulphuric acid 
affords evidence that the vinegar was made by inversion 
of starch with sulphuric acid, it is not an infallible proof, 
for an amount of sulphate in excess of 0-03 per cent, 
might be also due to the use of a very hard water, or to 
sulphuring the casks, or washing them with a soluble 

* Dr. Edmunds, Public Analyst for St. James', writing in the British 
Food Journ. (1900, p. 21), stated that he regarded all vinegars containing 
more than 0-0 1 to 0-03 per cent, of sulphates as adulterated. 


sulphite, which had subsequently become oxidised to 


Detection of Methyl- Acetol. It has been shown by 
Pastureau * that certain vinegars contain methyl-acetol, 
CH 3 . CO . CHOH . CH 3 , probably derived from wood 
acid. It may be isolated by neutralising 100 c.c. of the 
sample with sodium hydroxide, and distilling the liquid 
to dryness. 

If methyl-acetol is present, the distillate will reduce 
cold Fehling's solution, and when treated with iodine 
will give a precipitate of iodoform. When treated with 
phenyl-hydrazine acetate it will yield an osazone melting 
at 243 C., and giving a red coloration when dissolved 
in ether-alcohol and tested with ferric chloride, and red 
crystals on evaporating the liquid. 

A quantitative estimation may be made by treating 
an aliquot part of the distillate with a few drops of sodium 
hydroxide solution and ammonia, and adding 10 c.c. of 
silver nitrate solution. The liquid is allowed to stand 
for 24 hours, diluted to 100 c.c., and filtered, and the 
excess of silver titrated by the cyanide method. 

From the amount of reduced silver the quantity of 
methyl-acetol is calculated by means of the equation 

3(CH 3 CO . CHOH . CH 3 ) + AgN0 3 

= 3CH 3 CO . COCH 3 + 3H 2 + Ag. 

One sample of vinegar thus examined contained 0-32 per 
cent, of methyl-acetol. Or Kling's method f of estimation 

*Journ. Pharm. Chim., 1905, [6], xxi., 593. 
f Bull. Soc. Chim., 1906, xxv., 215. 


with alkaline copper solution may be used, each gramme 
of methyl-acetol yielding 2-85 grammes of cuprous 

Estimation of Formic Acid. Fincke * has devised the 
following method of estimating formic acid in vinegar : 
Five c.c. of the sample are heated for two hours on the 
water bath beneath a reflux condenser with 5 grms. of 
sodium acetate, 40 c.c. of a 5 per cent, mercuric chloride 
solution and 30 c.c. of water, the liquid in the flask being 
completely immersed in the boiling water. The resulting 
precipitate of calomel is collected in a Gooch's crucible, 
washed with water, alcohol and ether, and dried and 
weighed. The. weight multiplied by the factor 0-0977 
gives the amount of formic acid. 

The method affords an indication of the presence of 
added acetic acid in some vinegars, since commercial 
acetic acid almost invariably contains formic acid as an 
impurity. It is essential, however, that no caramelised 
sugar should be present, for sugar yields appreciable 
quantities of formic acid when heated to 160 C., at 
which temperature caramelisation begins. 

Hence, as caramel is universally employed for colouring 
fermentation vinegars in this country, no reliance can 
be placed upon the results of the formic acid test if applied 
to coloured vinegars. 

Moreover, although formic acid does not appear to be 
produced in the manufacture of spirit vinegar, it is 
found as a normal constituent in wine vinegars, f and 
probably also in other kinds of vinegar to which no 
caramel has been added. 

*J. Soc. Chem. Ind., 1911, xxx., 82, 235, 916. 
f Analyst, 1911, xxxvi., 496. 


Determination of Total Nitrogen. The nitrogenous 
substances in malt are readily transformed into am- 
monium sulphate by Kjeldahl's process, and a clear 
solution may be obtained in about an hour by adding 
a little potassium bisulphate to the sulphuric acid. The 
addition of mercury accelerates the process, but, as a 
rule, is not necessary. From 10 to 25 c.c. of the vinegar 
are used for the determination. 

Nature of Nitrogenous Substances. Only a small pro- 
portion of the nitrogen in vinegar appears to be in the 
form of ammonium salts or albumoses precipitable by 
ammonium or zinc sulphates. In one experiment in 
which 1,000 c.c. of vinegar brewed from barley malt 
were concentrated to 100 c.c., and aliquot portions used 
for the different estimations, the following results were 
obtained by the writer : 

Per cent. 

Total nitrogen, 0-1204 

Nitrogen in precipitate given by"| 

ammonium sulphate (after evapo- 1(1) 0-0127 

ration with water and barium | (2) 0-0157 
carbonate), J 

Nitrogen in zinc sulphate precipitate, . 0-0148 

Ammoniacal nitrogen, . - . . 0-015 

Similar results were obtained with a sample of com- 
mercial malt vinegar : 

Per cent. 

Total nitrogen, . . . .< . 0-089 

Nitrogen precipitated by ammonium 

sulphate, . ' . . . . 0-008 

Ammoniacal nitrogen, . . . 0-007 


Determination of Phosphoric Acid. Of the many 
processes devised for determining small quantities of 
phosphoric acid, one of the most simple and accurate 
for the analysis of vinegar is the modification of the 
molybdate method devised by Hehner. 

The ash from 10 c.c. of the sample is dissolved in the 
smallest possible quantity of dilute nitric acid, and 
treated with a large excess of an ammonium molybdate 
solution. The basin is allowed to stand for 12 hours 
at the ordinary temperature, or for two hours on 
the top of a hot- water oven, after which the yellow 
precipitate is washed twice by decantation with cold 
water. It is then dissolved in ammonia solution, the 
liquid evaporated, and the residue dried on the water 
bath. The weight divided by the factor 28-5 gives the 
amount of phosphoric acid (P 2 5 ). 

The molybdate reagent may be prepared by dissolving 
50 grms. of molybdic acid in a mixture of 50 c.c. of 
ammonia solution and 150 c.c. of water. When cold, 
the solution is cautiously added to a cold mixture of 
280 c.c. of nitric acid and 470 c.c. of water, and the 
reagent is filtered after standing for some hours. 

As a rule, the amount of phosphoric acid in a vinegar 
brewed from malted or unmalted barley will exceed 
0-05 per cent., but the amount may be increased by the 
use of yeast foods to aid the fermentation, or may be 
reduced by clarification processes in which the wort is 
fined by the addition of soluble calcium salts. 

Reducing Sugars. The following method of estimating 
the reducing sugars in cider vinegar is recommended 
by Leach and Lythgoe* : Two portions (25 c.c. each) 

*./. Amer. Chem. S r oc., 1904, xxvi., 375. 


are taken. One is diluted with 20 c.c. of water and heated 
with 5 c.c. of hydrochloric acid for ten minutes, and then 
cooled. Both portions are neutralised with sodium 
hydroxide and made up to 100 c.c., and tested with 
Fehling's solution. The amount of reducing sugars 
ought to be the same before and after inversion, any 
increase denoting the presence of cane sugar. 

The ratio between the weights of total solids and 
dextrose affords a means of detecting glucose vinegars 
in wine vinegars (see p. 187). 

Detection of Inositol in Wine Vinegar. It has been 
shown by Meillere * that inositol is a constituent of all 
wines, and since this sugar is not decomposed during 
acetic fermentation, its separation and identification 
affords a means of distinguishing between wine vinegar 
and spirit vinegar. 

The following method of applying the test was devised 
by Fleury ( : One hundred c.c. of the vinegar are evapo- 
rated nearly to dryness, and the residue taken up with 
50 c.c. of water, neutralised with sodium hydroxide, and 
ground up with 3 grms. of barium hydroxide. The pre- 
cipitate is separated, with the aid of centrifugal force, 
and washed with 20 to 30 c.c. of baryta water, and the 
filtrate and washings freed from barium by means of a 
current of carbon dioxide, after which 10 c.c. of dilute 
lead acetate solution are added, and the new precipitate 
separated as before. The filtrate is concentrated to 
100 c.c., and treated with 10 c.c. of the official basic lead 
acetate solution (lead acetate, 300 grms. ; lead oxide, 
100 grms. ; water, 700 c.c., shaken and filtered), and 

* Journ. Pharm. Chim., 1908, [6], xxviii., 289. 
t Ibid., 1910, [7], ii., 264. 


2 grms. of neutral cadmium acetate in solution. The 
precipitate containing the inositol is washed and decom- 
posed with hydrogen sulphide, and nitrate from the 
cadmium sulphide is concentrated to a syrup, and treated 
with 20 c.c. of absolute alcohol and 5 c.c. of anhydrous 
ether, and allowed to stand for 24 hours. The crystals 
of inositol which form in the case of a wine vinegar are 
separated and identified. 

Tests of identity have been based upon the oxidation 
of the sugar into a quinonic compound, rhodizonic acid, 
some of the salts of which are of a bright red colour. 

Seidel dissolves a little of the precipitate in water, and 
treats the solution with a drop of Millon's reagent.* The 
liquid is evaporated to dryness, the residue dried at 
110 to 120 C., and treated with 3 c.c. of glacial acetic 
acid, and one drop of a 10 per cent, solution of strontium 
acetate, and the solution evaporated on the water bath. 
A bright red coloration and deposit are obtained. 

Another proof of identity is to evaporate the residue 
with Gallois' mercuric reagent, which is prepared by 
dissolving 1 grm. of yellow mercury oxide in a mixture 
of 1 c.c. of nitric acid and 10 c.c. of water, and diluting 
the solution to 20 c.c. The resulting mercury rhodizonate 
is a brilliant red salt. 

Detection of Malic Acid. Cider vinegar should 
always contain malic acid, and the following tests for 
its detection are recommended by Leach and Lythgoe f : 
The vinegar should give a precipitate with lead acetate, 

* One part of mercury is dissolved in 2 parts of nitric acid (40 B.), and 
the solution diluted with an equal volume of water, and after 24 hours 
decanted from the crystalline deposit. 

f J. Amer. Ckem. Soc., 1904, xxvi., 375. 


subsiding rapidly. The presence of malic acid is then 
confirmed by treating 5 c.c. of the vinegar with 1 c.c. of 
10 per cent, calcium chloride solution, filtering, and adding 
3 volumes of 95 per cent, alcohol to the filtrate. A floc- 
culent precipitate will be obtained if malic acid be present. 

The addition of the alcohol will also precipitate dextrin, 
but this may be detected by a dextro-rotatory reading 
in the polarimetric test. 

A precipitate should also be obtained with calcium 
sulphate after drying the calcium chloride precipitate, 
dissolving it in nitric acid, and evaporating the solution 
on the water bath to convert the calcium malate into 
calcium oxalate, which is then decomposed by boiling 
with sodium carbonate. The filtrate from the calcium 
carbonate is then acidified with acetic acid, and tested 
with calcium sulphate solution. 

Tartaric Acid. If the total solids left on evaporation 
of wine vinegar be treated with absolute alcohol, a 
granular residue of hydrogen potassium tartrate will be 
left undissolved. The nature of this deposit may be 
confirmed by dissolving it in the smallest possible quantity 
of hot water, and stirring the solution in a watch-glass 
by means of a glass rod. The cream of tartar will then 
be re-deposited in streaks following the lines of the rod. 

The following confirmatory test of identification, 
devised by Deniges, may also be applied : The crystals 
are added to a reagent consisting of 3 c.c. of sulphuric 
acid and 3 drops of a solution of resorcinol (2 grms. in 
100 c.c. of water acidulated with 5 c.c. of sulphuric acid), 
and the mixture heated to 130 to 140 C. In the presence 
of tartaric acid an intense carmine-red coloration is 


For the estimation of the potassium bitartrate 25 c.c. 
of the vinegar are evaporated to a syrup. This is dissolved 
in 25 c.c. of water, and the solution mixed with 100 c.c. 
of alcohol-ether (1 : 1), and allowed to stand for 24 hours 
in a cool place. The resulting precipitate is washed with 
alcohol-ether, and dissolved in hot water, and the solu- 
tion titrated with ~ alkali. Each c.c. required corre- 
sponds to 0-0188 grm. of potassium bitartrate. 

Citric Acid. This may be detected by the test devised 
by Deniges for wines : Ten c.c. of the vinegar are 
shaken with 1 grm. of lead peroxide and 2 c.c. of mercuric 
sulphate solution, and filtered. About 5 c.c. of the 
filtrate are boiled and treated with a drop of a 1 per cent, 
solution of potassium permanganate solution ; after 
decolorisation an additional 10 drops are added, one by 
one. Normal wine vinegars yield a slight turbidity in 
this case, while those containing 0-10 grm. or more of 
citric acid per litre give a pronounced turbidity. 

Oxalic Acid. The following method is recommended by 
Calvet * : Fifty c.c. of the vinegar are neutralised, and 
the oxalic acid precipitated as calcium oxalate by means 
of calcium acetate. The precipitate is washed and 
oxidised with a standardised sulphuric acid solution of 
potassium permanganate ; or it is sulphated, dried, and 
weighed as calcium sulphate. The weight multiplied by 
the factor 18-55 gives the amount of oxalic acid per litre 
of vinegar. 


The recommendation of the Local Government Board, 
to the effect that the only colouring matter which it 

* Alcool Mtthylique, Vinaigres, 1912, p. 136. 


should be permissible to add to vinegar should be caramel 
is almost universally accepted in this country. 

Vinegar brewed from malt or malt and cereals is of 
too pale a colour to be generally acceptable, except in 
Scotland, and it is, therefore, essential to add some 
colouring matter to meet the popular taste. Although 
aniline dyestuffs may possibly be used for this purpose, 
caramel has long been regarded as the most suitable 
colouring matter from every point of view. 

Measurement of Colour Intensity. Owing to the great 
variations in the tinctorial power of different varieties of 
caramel, it is not easy to fix upon a standard substance 
upon which to base subsequent measurements. Even if 
a standard solution is made up from a particular sample 
of caramel and kept for comparison with subsequent 
samples, gradual fading takes place, especially if the 
bottle is exposed to the light. Some slight decomposi- 
tion and deposition of the pigment is also inevitable in 
the course of time. 

An iron compound which, when dissolved, would give 
the required shade of colour might possibly be used for 
the purpose, but this would involve the use of an absol- 
utely pure salt, which would have to be weighed out 
and dissolved before each comparison, since it would 
not be stable in solution. 

Iodine solutions of standard strength were adopted by 
the Berlin Congress of 1903 for measuring the colour of 
malt products, but they are only suitable for light-coloured 
worts, since the tint of iodine is considerably redder than 
that of strong malt worts. 

To obviate this drawback Brand and Jais * suggested 

* ges. Brauw., 1906, xxix., 337. 


the use of aniline dyestuffs to obtain a standard corre- 
sponding in intensity of shade to iodine, and equivalent 
in colour tone to the colouring matter of malt or caramel 
at all concentrations. 

This system has the same drawbacks as the use of an 
iron salt, especially the deterioration of the tinctorial 
value of the standard solutions on keeping. 

Hence, the invention of Lovibond's tintometer has 
been of material service to all who have to match and 
keep a record of colours, and the apparatus is now ex- 
tensively used in many industries. 

Lovibond's Tintometer. The use of this instrument 
is based upon a comparison of the coloured substance 
with a series of standard coloured glasses, which can be 
blended in such a way as to give the same colour 

For the purposes of brewers and vinegar makers a 
special series of these glasses approximating to the colour 
of solutions of malt extract or caramel is provided, the 
liquid being placed in a glass cell 1 inch or J inch in width, 
while the numbered glasses are placed in a small holder, 
and viewed simultaneously through the instrument in a 
good light. 

It has been shown by Baker and Hulton * that agree- 
ment between the results obtained by different observers 
depends on various conditions, such as the relation of 
the instrument to the source of light, and from the results 
of their experiments they make the following recom- 
mendations : (1) The tintometer should be used in a 
horizontal position directed to a north window covered 
with white tissue paper ; (2) it should not be more than 

* Journ. Inst. Brewing, 1907, xiii., 26. 


2 to 3 feet from the window ; and (3) the opal screen 
of the instrument should be discarded. 

In the writer's experience it is possible to match the 
colours of most vinegars by means of the " 52 " series 
of glasses, although in some cases a glass of the " 50 " 
series may be required. 

When examined in a 1-inch cell the pale vinegars of 
commerce range from about 5 to 10 in the " 52 " series, 
medium- coloured vinegars from 15 to 20, and dark 
vinegars from 30 to 40. 

In the case of the darkest products it is advisable to 


Fig. 52. Lovibond's Tintometer. 

dilute the liquid with an equal volume of water, since 
the results of two observers will agree better under such 
conditions than when a very dark liquid is examined 
without dilution. 


The Fuller's Earth Test. It is frequently possible to 
precipitate the whole of the added caramel by treating 
the vinegar with a little fuller's earth that has been 


proved to be active in this respect. For example, wood 
vinegar may usually be completely decolorised in this 

But when applied to vinegars which owe part of their 
colour to products formed in the drying of the malt or 
grain too much reliance must not be placed upon this 

Thus, it has been shown by Dubois * that the amount 
of colour removed from a cider vinegar may vary from 
nothing to 72 per cent., and that the proportion will 
differ with different kinds of earth. Hence, a sample of 
vinegar which gave no deposit when treated with one 
earth, would be regarded as containing added caramel 
when treated with another earth. Nor are the results 
given by the same earth uniform. Thus, in Dubois' 
experiments, an earth which removed no colour from one 
pure vinegar removed the larger proportion from another 
pure sample. 

At best, the test must be regarded as a preliminary one. 
If all colour is removed, caramel is undoubtedly present, 
while if little or no colour is removed the sample may be 
regarded as free from caramel. But in the case of most 
vinegars, from which about 25 to 75 per cent, of colour 
is removed, the test is inconclusive. 

Lichthardt -f uses a method of precipitation with 
tannin as a test for caramel in vinegar, flavouring extracts, 
etc. Five c.c. of a solution of 1 grm. of gallotannic acid 
and 0-75 grm. of sulphuric acid (sp. gr. 1-84) in 50 c.c. 
of water are added to the vinegar, and the mixture heated 
until the precipitate that first forms is dissolved. The 

* J. Amer. Chem. Soc., 1907, xxix., 75. 
t*/. Ind. Eng. Chem., 1910, ii., 389. 


liquid is then allowed to stand for 12 hours, and in the 
presence of caramel a light or dark brown deposit will 
be present. 

The objection to this test is that albuminous substances 
and iron compounds also react with tannin, so that the 
formation of a precipitate is not a conclusive indication 
of caramel. 

The method officially used in France for wine vinegar is 
to shake 50 to 100 c.c. of the sample with 50 c.c. of 
ether, to allow the colourless ethereal layer to evaporate 
spontaneously, and to test the residue with 2 to 3 drops 
of freshly prepared 1 per cent, solution of resorcinol in 
hydrochloric acid. In the presence of caramel a rose 
coloration will be obtained (Fiehe's reaction). 

If the ethereal layer is coloured, it should be washed 
with water rendered slightly ammoniacal, and evaporated. 
Or, if necessary, the residue may be taken up with 25 c.c. 
of water, and the solution boiled with a little egg-albumin 
(white of egg), the colouring matter being removed by 
the coagulated albumin. 

It has been shown by Anderson * that pure cider 
vinegars contain furfural, and that Fiehe's reaction is, 
therefore, not necessarily an indication of the presence 
of caramel in such vinegars. 

Amthor j- bases a method of detecting caramel upon 
its precipitation with paraldehyde. Ten c.c. of the 
vinegar are mixed with 30 c.c. of paraldehyde and suffi- 
cient absolute alcohol to obtain a clear solution, and the 
mixture left for 24 hours in a closed flask. 

The precipitate is washed with absolute alcohol and 
dissolved in water, and the solution evaporated to 1 c.c., 

* Ibid., 1914, vi., 214, t Zeit - ana l- Chem., xxiv., 30. 



and heated for 30 minutes at 100 C. with a small quantity 
of an acetic acid solution of phenyl-hydrazine. If the 
precipitate consisted of caramel an amorphous compound 
(probably composed of phenyl-hydrazones and osazones) 
is obtained. 

Various colorimetric methods of estimating caramel 
have been suggested (e.g.) by Smith, Amer. J. Pharm., 
1911, Ixxxiii., 411), but since commercial samples vary 
widely in their chemical composition, according to the 
different methods of manufacture in use, none of these 
can lay claim to much accuracy. 

In practice caramel is bought upon the basis of its 
colouring capacity without reference to the chemical 
compounds to which its colour is due. 

The method recommended by a Committee of the 
Institute of Brewing * is essentially the same as that 
used by the present writer for many years : Ten grms. 
of the sample are dissolved in 100 c.c. of water at 15-5 C., 
and the solution diluted to a litre, and compared in a 1-inch 
cell with glass of "52 " series in Lovibond's tintometer. 

Coloured Wine Vinegars. The coloration of wine 
vinegars with cochineal or archil is allowed by the French 
law. The official methods used in France in the detec- 
tion of these colouring matters are as follows : 

Cochineal. Twenty-five c.c. of the vinegar are shaken 
for five minutes with 20 c.c. of ether, and the ethereal 
extract treated with a few drops of ammonia solution. 
In the presence of cochineal a carmine red coloration is 

As a confirmatory test 4 c.c. of the vinegar are neutral- 
ised and treated with 1 c.c. of a 1 per cent, solution of 

* Jovrn. Inst. Brewing, 1910, xvi., 529. 


ammonium alum followed by 1 c.c. of a 10 per cent, sodium 
carbonate solution. The resulting lake will be bluish- 
violet, and the filtrate violet, if the colouring matter was 

Archil. Twenty-five c.c. of the vinegar are made 
slightly alkaline with ammonia, and shaken with 10 c.c. 
of amyl alcohol, a violet coloration being obtained in the 
presence of archil. The extract is evaporated, and the 
residue treated with one drop of sulphuric acid, which 
gives a coloration changing to bluish-violet on addition 
of ammonia. 


Vinegar is very liable to become contaminated with 
metallic impurities, such as iron and copper, derived from 
hoops upon the vats, brass taps, and the like, with which 
it may come into contact. 

Iron. The presence of traces of iron is mainly of 
importance from the fact that when the vinegar comes 
in contact with the wood in a new barrel a black iron 
tannate will be formed, which will cause the vinegar to 
become dark and unsaleable. 

The presence of iron may be detected by adding 
potassium ferrocyanide directly to the vinegar, and it 
may be estimated colorimetrically in the ash by means 
of the same reaction. 

Copper, Lead, and Tin. For the detection of these 
metals 100 c.c. of the vinegar are boiled with 10 c.c. of 
hydrochloric acid, and potassium chlorate introduced in 
small quantities at a time until a colourless solution is 
obtained. This is treated with sodium acetate to remove 


the hydrochloric acid and a current of hydrogen sul- 
phides passed through the liquid. 

Copper may be estimated electrolytically in the vinegar 
itself. A few drops of nitric acid are added to 100 c.c. 
of the sample, which is then electrolysed for 30 minutes 
with a current of 2 vols. and 1 amp. per square decimetre. 
The copper is deposited on the electrodes in the usual 

In testing for lead the ash from the vinegar is moistened 
with acetic acid and treated with an excess of dilute 
ammonia solution, and the liquid boiled and filtered. 
This treatment is repeated several times to effect complete 
extraction, and the filtrates are united, and made up to 
a definite volume. In the presence of copper a brown 
coloration will be obtained on the addition of potassium 
ferrocyanide to a small part of the liquid. 

If no copper is found, the solution is rendered acid 
with hydrochloric acid, and tested for lead with a solution 
of hydrogen sulphide. 

When copper is present an addition of a small quantity 
of potassium cyanide should be made before applying 
the test for lead, The ferrocyanide test for copper and 
the hydrogen sulphide test for lead may be used for the 
colorimetric estimation of traces of those metals, the tint 
produced being matched with standard solutions of lead 
and copper salts. 

Tin. The ash of the vinegar is fused with sodium 
hydroxide, and the mass extracted with boiling water 
containing a little hydrochloric acid. The filtered extract 
is tested with hydrogen sulphide, which in the presence 
of tin gives a yellow coloration or precipitate. 

Arsenic. The discovery, in 1900, that several cases of 


peripheral neuritis had been caused by drinking 
beer containing arsenic drew general attention to the 
possibility of the occurrence of dangerous amounts of 
arsenic in other food products. 

The Royal Commission appointed in 1901 to investigate 
the subject found that the glucose used in the preparation 
of these arsenical beers contained quantities of arsenic 
ranging from 0-015 to 0-131 per cent., and that in the 
case of one sample of beer the amount of arsenic reached 
3 grains per gallon. 

The original source of this arsenic was discovered in 
the sulphuric acid used in the preparation of the brewing 
sugar, some of the samples of acid containing as much 
as 2-5 per cent, of arsenic (as arsenious acid). 

Arsenic was also detected in other beers brewed from 
malt, the poison being ultimately traced to the fuel used 
for the kilns. 

Since vinegars are brewed upon similar lines to beer, it 
is not surprising that traces of arsenic were found in many 
samples, and that serious, if not dangerous, quantities 
were present in vinegars made by the conversion process, 
where impure sulphuric acid had been employed. 
. Another possible source of arsenic in vinegar is the 
caramel, which is almost universally employed as a 
colouring material. This is often prepared from glucose, 
and the use of impure acid in the hydrolysis of the starch 
has been known to cause arsenic to be present in the 

After the publication of the report of the Royal Com- 
mission in 1903 precautions were taken by the maltsters 
and the manufacturers of brewing sugars to prevent 
recurrence of the trouble, and, as a rule, the malt now 


upon the market seldom contains over -^i F grain of arsenic 
per pound. 

In 1901 a Conjoint Committee of the Society of Chemical 
Industry and of the Society of Public Analysts was 
appointed to examine and report upon the various methods 
of detecting and estimating arsenic, and in the following 
year issued the subjoined report,* which, if exactly fol- 
lowed, will give accurate results under all conditions : f 

" MATERIALS REQUIRED Hydrochloric Acid. The purest hydro- 
chloric acid obtainable is very rarely free from arsenic. To the ' pure ' 
acid, as purchase^ for analysis, diluted with distilled water to a specific 
gravity of 1-10, sufficient bromine is added to colour it strongly yellow 
(about 5 c.c. per litre), sulphurous acid, either gaseous or in aqueous solution, 
is then added in excess, and the mixture is allowed to stand for at least 
twelve hours, or hydrobromic and sulphurous acid may be used The 
acid is then boiled till about one-fifth has evaporated, and the residue 
can either be used directly or may be distilled, the whole of the arsenic 
having volatilised with the first portion. 

" Sulphuric Acid. This is more frequently obtainable arsenic-free than 
hydrochloric acid. If not procurable, to about half a litre of sulphuric 
acid ' pure for analysis/ a few grammes of sodium chloride are added, and 
the mixture distilled from a non-tubulated glass retort, the first portion of 
about 50 c.c. being rejected. For the purpose of the test to be described, 
one volume of the distilled acid is diluted with four volumes of water. 

" Nitric acid can, as a rule, be obtained free from arsenic without much 
difficulty ; the pure redistilled acid should be used. This should be tested 
by evaporating 20 c.c. in a porcelain dish, which should then be washed 
out with dilute acid, and tested as described in this report. 

" The purified acids should be prepared as required, and should not be 
stored for any length of time. If this is unavoidable, however, Jena flasks 
are to be preferred, since most bottle glass is liable to communicate traces 
of arsenic. 

" Zinc. Arsenic-free zinc is obtainable from chemical dealers. It should 
be regranulated by melting it and pouring it from some height into cold 

* The report is condensed here ; the directions for testing beer are also 
appk'cable to vinegar. * f Analyst, 1902, xxvii., 48. 



" Lime. Caustic lime, even when made from white marble, is not always 
free from arsenic. A selection must, therefore, be made from various 
samples. If pure lime is not obtainable, magnesia may equally well be 
used, and can be more readily obtained of sufficient purity. 

" Calcium Chloride. This salt often contains arsenic, and before being 
used as a drying agent must be freed from the volatilisable part of the 
impurity by moistening it with strong hydrochloric acid, fusing and re- 

" Apparatus. A bottle or flask holding about 200 c.c. (for frothing 
materials preferably wider at top than bottom) is fitted with a double- 


Fig. 53. Arsenic Apparatus. 

bored cork, india-rubber stopper, or with a ground-in glass connection, 
carrying a topped funnel (holding about 50 c.c.), and an exit tube. The 
latter is connected with a drying tube containing, first, a roll of blotting 
paper soaked in lead acetate solution, and dried, or a layer of cotton wool 
prepared in a similar way, then a wad of cotton wool, then a layer of granu- 
lated calcium chloride, and finally a thick wad of cotton wool. To this 
tube is fitted a hard-glass tube drawn out as shown in the figure, and of 
such external diameter that at the place where the arsenic mirror is to be 
expected the tube just passes through a No. 13 Birmingham wire gauge 
(corresponding with 0-092 inch). The exact size is not material, but all 


tubes used for standards and tests should be as nearly as practicable of the 
same diameter. A good Bunsen flame is used to heat the hard-glass tube 
close to the constriction. About 1 inch of tube, including the shoulder, 
ought to be red hot. A piece of moderately fine copper gauze (about 1 inch 
square) wrapped round the portion of tube to be heated assists in insuring 
equal distribution of heat. A suitable form of apparatus is shown in the 
accompanying figure. 

" About 20 grammes of zinc are placed in the bottle and washed with 
water to clean the surface, as particles of dust may contain arsenic ; all 
parts of the apparatus are connected, and a sufficient quantity of acid 
(prepared as previously described) allowed to flow from the funnel, so as 
to cause a fairly brisk evolution of hydrogen. When the hydrogen flame, 
which during the heating of the tube should be kept at as uniform a height 
as possible (about a quarter of an inch), burns wi^h a round, not pointed, 
tip, all air has been removed from the apparatus. The Bunsen burner 
should then be placed under the hard-glass tube as described, and more 
acid (10 to 20 c.c. are generally enough) run in as required. With good 
materials no trace of a mirror is obtained within half-an-hour. 

" Great care must be taken that when additions of acid are made to the 
zinc no bubble of air is introduced, since in presence of air the arsenic mirror 
may become black and unevenly distributed, whilst it is brown when the 
experiment has been properly conducted. 

" Should the blank experiment not be satisfactory, it must be ascertained 
by changing the materials methodically whether the fault lies with the 
acid, zinc, other materials, or with the apparatus. 

" Preparation Of Standard Mirrors. When a satisfactory blank experi- 
ment has been obtained a series of standard mirrors must be prepared 
under the following conditions : A hydrochloric acid solution of arsenious 
oxide containing in each c.c. 0-001 milligramme As 4 6 is prepared by diluting 
a stronger solution with distilled water. Two c.c. of this solution (equal 
to 0-002 milligramme of arsenious oxide) are introduced into the apparatus, 
a new tube having been joined to the drying tube. If the zinc is sensitive 
a distinct brown mirror is obtained after twenty minutes. It is important 
to note that some ' pure ' zinc is from a cause at present unknown * not 
sufficiently sensitive that is to say, the addition of minute quantities of 
arsenic produces no mirrors. The portion of tube containing the mirror 
should be sealed off while still filled with hydrogen ; in contact with air 
the mirrors gradually fade. Mirrors are now similarly made with 0-004, 
0-006, 0-008, and 0-01 milligramme of arsenious oxide. With a little 

* Chapman and Law, Analyst, 1906, 3. 


patience it is easy to obtain the deposits of arsenic neatly and equally 
distributed. The standard mirrors, properly marked, are mounted on a 
white card or porcelain slip. It is to be understood that the first stage of 
every test must be a blank of at least twenty minutes. 

" Organic materials, such as yeast, beer, etc., cannot be tested when 
sulphuric acid is used, without destruction of organic matter, whilst as a 
rule they can be directly tested with hydrochloric acid. 

"Procedure without Destruction of Organic Matter. The apparatus is 
started, and a blank experiment allowed to go on for 20 minutes. If 
no trace of deposit is obtained 10 c.c. of the liquid to be tested and about 
10 c.c. of hydrochloric acid are put into the funnel and slowly introduced 
into the bottle without air-bubbles. Some materials (beers, for example) 
are apt to froth ; hence the necessity for slow introduction. If after about 
10 minutes no mirror appears, another 10 c.c. of the liquid, with 10 c.c. 
of hydrochloric acid, are added, and the experiment continued for 15 to 
20 minutes, acid being added from time to time as may appear 

" Malt. Fifty grammes of the malt are placed in a 300 c.c. separator 
funnel with a stopcock ; 50 c.c. of hydrochloric acid, prepared as described, 
and 50 c.c. of water are warmed to about 50 C. and poured on the malt. 
The whole is then allowed to digest for 15 to 20 minutes with frequent 
agitation, and the acid then allowed to run off by the stopcock. About 
60 c.c. of the acid liquor is thus obtained, of which 20 c.c. contains the 
arsenic from 10 grammes of malt. 

" Sugar and other brewing materials are dissolved in water, 10 c.c. of 
acid added, and the solution tested direct, operating upon 10 to 20 grammes 
of material. 

" Destruction of Organic Matter (a) Acid Method. Ten grammes of the 
substance are placed in a 3-inch porcelain crucible, and covered with pure 
distilled nitric acid (about 10 to 15 c.c.). The whole is then heated on a 
sand bath until the evolution of brown fumes ceases. Three c.c. of con- 
centrated arsenic-free sulphuric acid are then added, and the heating 
continued until the mass just begins to char, when a further quantity of 
5 c.c. of nitric acid is added. The heating is now continued until all acid 
is expelled, leaving in the crucible a black, nearly dry, charred mass. The 
crucible is about half filled with water, and a few c.c. of hydrochloric acid 
or dilute sulphuric acid run in (according as the one or the other is to be 
used in the Marsh apparatus), the whole being allowed to extract for about 
half -an-h our on a water-bath. It is then filtered into a porcelain basin, 
the charred mass washed with hot water, and the filtrate concentrated 
down to about 30 c.c., which is allowed to cool, and is then ready for the 


test. It is essential that the mass should be thoroughly charred, and that 
the solution when filtered should be colourless. 

" In the case of beer, 10 to 20 c.c. are evaporated to dryness, and the 
residue oxidised as above stated. 

" (6) Basic Method. The materials are mixed with pure lime or magnesia 
(1 gramme for 20 c.c. of beer), dried, and incinerated. For sugars or other 
solid materials about half their weight of base is employed. The ash is 
dissolved in hydrochloric acid, and the solution tested. 

" The proof that the mirrors are arsenical is obtained as follows : The 
narrow portion of the tube containing the mirror (which should not be 
denser than that produced by 0-01 milligramme of arsenious oxide) is cut 
off, the hydrogen replaced by air, and the ends sealed up. The tube, held 
in the tongs, is then heated by drawing it repeatedly through the flame 
of a Bunsen lamp until the mirror has disappeared. On cooling, minute 
crystals of arsenious oxide deposit, the sparkling of which can be seen 
by the naked eye if the tube be held before a luminous flame, and which 
can be readily identified under the microscope by their crystalline form. 

" This test, as recommended, is one of such extreme delicacy that with 
quantities of 20 grammes (or 20 c.c. ) it will give an indication of the presence 
of 0-000015 per cent, (or 1 part in 7,000,000) of arsenious oxide." 



Interpretation of Results CHEMICAL STANDARDS Acetic Strength Total 
Solids ' k Original Solids " Nitrogen and Phosphoric Acid Optical 
Standard MALT VINEGARS The Malt Vinegar Question Composi- 
tion of Malt Vinegars Cider Vinegar Wine Vinegar Whey Vinegar 
Fruit and Herb Vinegars Date Vinegar Spirit Vinegars Essig- 
sprit Wood Vinegar Composition of Artificial Vinegars. 

THE interpretation of the results of an analysis is by no 
means an easy problem in the case of certain kinds of 
vinegar. Although analysis will show that a vinegar 
must be a wood vinegar or spirit vinegar or distilled 
vinegar, it is not possible to state with certainty the 
origin of some grain vinegars. For example, a safe 
deduction may be drawn from the deficiency of certain 
constituents that a vinegar has not been manufactured 
in a normal way from malted or unmalted barely, but it 
may not be justifiable to assert that it has not been derived 
from a mixture of malted barley and unmalted cereals- 
In the absence of legal standards for the composition of 
the different kinds of vinegar, the analyst can only draw 
probable conclusions from a comparison of his figures 
with the average results of products presumably brewed 
in the same way. The danger of placing too much reliance 
upon such comparisons was shown in a recent prosecution 
for the sale of a vinegar which the analyst asserted was 
not wholly derived from malt. The Stipendiary, in dis- 


missing the case, remarked, " This is not an analysis, but 
a guess/' 


Acetic Strength. The standard suggested by the 
Local Government Board in their definitions of vinegar 
and artificial vinegar, of a minimum of 4 per cent, of acetic 
acid, has already been mentioned. 

There have been numerous prosecutions and con- 
victions for the sale of vinegar containing less than 
4 per cent, of acetic acid, and the bulk of the vinegar 
sold throughout the country is now in excess of the 
4 per cent, standard. 

There is, however, no general agreement on the point, 
and even during the current year conflicting decisions 
have been given by magistrates. 

Legal standards for the strength of vinegar are found 
in the food regulations of some of the Colonies and in 
foreign countries. For example, in Australia and in the 
United States the same minimum standard for strength 
(4 per cent.) has been adopted. 

Standard for Total Solids. Early in 1907 the London 
and Country Vinegar Brewers' Association passed a 
resolution, to the effect that the conditions specified in 
the Admiralty contract were a correct definition of what 
No. 20 Vinegar should be : 

" The vinegar of No. 20 trade denomination, which 
contains 5-17 per cent, or 22-6 grains by weight of real 
acetic acid (C 2 H 4 2 ) per fluid ounce. It shall have a 
specific gravity at 60 F. of 1-017 to 1-021, and be whoUy 
the product of alcoholic, acetous fermentation in the 


vinegar itself, and that they were prepared to support 
local authorities in establishing such a standard, and 
that higher and lower strengths of vinegar be based on 
this definition/' * 

No attempt was made by the Local Government Board 
to give force to this proposed standard of a minimum of 
total solid matters. In fact, one firm declined to support 
the resolution upon the ground that to leave a large 
proportion of unfermented substances in the wash would 
lead to bad and uneconomical brewing. 

Moreover, a well-attenuated wash from an all-malt 
brew might have a much lower specific gravity than a 
wash prepared from glucose containing a large amount 
of unfermentable substances. At best, such a standard 
would have had the effect of making a sharper differenti- 
ation between brewed and artificial vinegars, which are 
usually sold at a cost that would not permit of the addition 
of suitable substances to raise the specific gravity. 

Calculation of "Original Solids." An empirical but 
convenient method of comparing the analytical results 
of the examination of vinegars of different acetic strength 
was devised by Hehner.f 

It is based upon a calculation of the percentage of the 
different constituents upon 100 parts of the solid matter 
estimated to have been present in the original wort. 
Since 180 parts of dextrose can be theoretically converted 
into 120 parts of acetic acid, the " original solids " are 
found by multiplying the percentage of acetic acid by 
the factor 1-5 and adding the product to the amount of 
total solids still remaining in the vinegar. 

For example, in the case of a vinegar containing 4-92 

* Dr. Hamill's Report, 1908, p. 16. t Analyst, 1891, xvi., 92. 


per cent, of acetic acid and 2-27 per cent, of total solids, 
the "original solids" would be (4-92 x 1-5) + 2-27 = 
9-65 per cent. 

It was pointed out by Allen and Moore * that in practice 
the yield of acetic acid seldom exceeds two-thirds of 
the theoretical amount, so that a more correct estimation 
of the original solids in the wort would be made by multi- 
plying the amount of acetic acid by ^ ( = 2-25) and 
adding this result to the total solids found in the vine- 
gar. Applying this method of calculation to the example 
given above, the " original solids " would be 13-44 per cent. 

As it is impossible, owing to the variety of materials 
used for brewing, and the variations in the loss on aceti- 
fication, to arrive at a true figure for the " original solids," 
there seems to be no advantage in substituting the value 
as calculated by Allen and Moore for the theoretical 
value suggested by Hehner. 

Nitrogen and Phosphoric Acid. The proportion of one 
or both of these constituents calculated upon the " original 
solids " of the vinegar is usually taken into consideration 
in giving an opinion upon the origin of a vinegar. 

In the case of a vinegar brewed from an average barley 
malt, the amounts of nitrogen and phosphoric acids in 
the " original solids " will usually exceed 0-5 per cent., 
and the two quantities of the two constituents will be 
approximately equal. This is, of course, assuming that 
no process has been used whereby the proportion of 
either is reduced. 

Barley malts vary widely in their composition, as is 
shown by the following analyses by Salamon t of sixteen 
samples of dried malt : 

* Ibid., 1893, xviii., 245. 1 7. Soc. Chem. Ind. f 1885. 




Total Nitrogen 

Total Nitrogen 
from Soluble 

P 2 5 . 

Lowest, . 

Per cent. 

Per cent. 

Per cent. 

Per cent. 

It will thus be seen that malt made from badly-germi- 
nated barley will contain much less soluble nitrogen 
than that from well-grown barley that has germinated 

At the same time, it is hardly probable that vinegar 
made from a malt containing only relatively small 
amounts of soluble nitrogen and phosphoric acid, such 
as the lowest figures recorded above, would contain less 
than the 0-5 per cent, of each constituent calculated 
upon the original " solids/' 

But the conditions are totally different when a mixture 
of malted barley or other malt with raw grain is used, 
as is obvious from a glance at the following analyses 
made by Gilbert : * 





Per cent. 

Per cent. 

Per cent. 

Per cent. 

Moisture, . 










Gums and sugars, 





Albuminoids (soluble 

and insoluble), 





Cellulose, . 





Fat, . . . .:". 





Ash, . . - . 





Total, . ' ._ 





* Quoted by Nettleton, The Manufacture of Spirit, p. 392. 


Again, according to von Bibra,* the ash of rye ranges 
from 1-97 to 2-05, and the proportion of phosphoric acid 
therein from 42-38 to 50-35. 

Hence, vinegars brewed from mixtures of a malted 
grain with any of these raw grains would show enormous 
variations in the proportions of nitrogen and phosphoric 
acid. If rye were used the values for both the con- 
stituents would be very much lower than if barley 
were the grain, while if rice were the cereal employed 
the percentages would be still less, and would fall far 
below those of a vinegar brewed from an average malted 
barley or a mixture of malt and barley. 

For these reasons it is obvious that even if the defini- 
tion of malt vinegar as a cereal product, the sacchari- 
fication of which has been initiated by the diastase of 
malt, were generally accepted, the difficulty of distin- 
guishing analytically between the different classes of 
cereal vinegars would remain. 

If prepared cereals are employed, the results will differ 
from those obtained with ordinary raw grain, as is shown 
by the following analyses of prepared grain, which have 
often been used in the manufacture of vinegar. These 
results are quoted by Nettleton.f 

The effect of the torrefying process on the barley is 
to reduce the oil and water, and to increase the propor- 
tion of starch, while leaving the amounts of mineral 
constituents and nitrogenous substances practically the 

In the case of the flaked preparations similar changes 
take place, while the amounts of ash, nitrogenous sub- 

* Odrungstechnische Untersuchungs-metJioden (Bauer), p. 143. 
t The Manufacture of Spirit, p. 394. 



stances, and phosphoric acid are but little affected, after 
making allowance for the different proportions of water 
in the cereal before and after treatment. 

Torrefied or 
Popped Barley. 

Flaked Maize. 

Flaked Maize 

Per cent. 

Per cent. 

Per cent. 

Moisture, . 




Oil, .... 






I 8-54 

Starch and sugars, 







Woody fibre and cellulose, 

6-03 J 




the oil) 

Mineral ash, 



Chapman * has shown that the proportion of phosphoric 
acid in a vinegar depends, not only upon the composition 
of the cereal, but also upon the nature of the mineral 
salts in the brewing water. 

This was illustrated by the following experiments, in 
which two different malts were mashed with waters of 
different degrees of hardness, and the proportions of 
phosphoric acid in the filtrates were determined : 

MALT, A. Phosphoric Aeid (P 2 6 )- 

Grains per Gallon. 

Distilled water, . . . .46-56 

Water containing 20 grains total solids, 42-44 
Very hard water, . . . .30-44 


Distilled water, .... 44-77 

Water containing 20 grains total solids , 37-61 
Very hard water, . . . .26-88 

* Analyst, 1912, xxxvii., 123. 



In the case of vinegars brewed with very hard water 
Chapman found that almost the whole of the phosphoric 
acid was left in an insoluble condition (tribasic calcium 
phosphate) on ignition of the total solids. 

For these reasons he deprecates the fixing of an official 
standard for phosphoric acid in vinegar. 

In like manner, the proportion of nitrogen is influenced 
by the conditions of brewing. If low-dried malt and low 
mashing temperatures be used, the nitrogen will be 
higher than if high-dried malts are employed, or part of 
the wort be boiled after mashing, as is sometimes done 
to promote the final filtration of the vinegar. The addi- 
tion of ferrocyanide as a clarifying agent (see p. 131) 
precipitates proteins, and this reduces the proportion of 
nitrogen, and these instances afford further illustrations 
of the dangers mentioned by Chapman (loc. cit.) " of 
setting up official standards for the composition of manu- 
factured foodstuffs/' 

Optical Standard. In 1906 malt vinegar was defined 
by the United States Department of Agriculture (Circular 
No. 19) as " a product made by the alcoholic and 
subsequent acetous fermentations, without distillation, 
of an infusion of barley malt, or cereals whose 
starch has been converted by malt, is dextro-rotatory, 
and contains in 100 cubic centimetres (20 C.) not 
less than 4 grammes of acetic acid, not less than 
2 grammes of solids, and not less than two-tenths 
(0-2) gramme of ash ; and the water-soluble ash 
from 100 c.c. of the vinegar contains not less than 
9 milligrammes of phosphoric acid (P 2 5 ), and re- 
quires not less than 4 c.c. of ^ acid to neutralise its 


It has been shown by Chapman * that vinegar brewed 
from barley malt and cereals need not necessarily be 
dextro-rotatory, but that the proteins and their hydro- 
lytic products may cause the vinegar to show a Isevo- 
rotation. For example, practically the whole of a manu- 
facturer's stock of vinegar showed a Isevo-rotation of 
0-56 to 0-76 when examined in a 200 mm. tube, 
although no sugar had been used in the brewing. 

The Malt Vinegar Question. Few problems that have 
arisen in the administration of the Food and Drugs Acts 
have presented more difficulties than the question of 
what is or is not " malt vinegar," for there is no legal 
definition of the product, and all attempts to obtain a 
binding decision have hitherto proved fruitless. 

As far back as 1894 the subject came into prominence 
in connection with certain vinegar prosecutions in the 
Midlands, and a Conference of the Society of Public 
Analysts f was held with the idea of obtaining some 
concerted agreement upon the point. 

In the course of the discussion it soon became evident 
that there was a great divergence in the views held by 
leading Public Analysts on this subject. For example, 
while one speaker held that " malt vinegar " ought to be 
derived solely from malted barley, a second was pre- 
pared to pass a product brewed from a mixture of 10 per 
cent, of malt and 90 per cent, of barley, and a third 
remarked that " no one would doubt for a moment but 
that ' malt ' was a term applied to a mixture of malt 
and barley only/' Still greater latitude was allowed by 
another Public Analyst, who urged the Society to adopt 
the view that malt vinegar was " a product initiated by 

* Analyst, 1912, xxxvii., 123. t Analyst, 1894. 


malt alone ; raw grain may be used with it in the mash- 
tun, because the utilisation of its starch is absolutely 
restricted to the action of the malt, and therefore the 
constituents of the wort may be said to be strictly malt 
products/' He would not admit " the products of starch 
hydrolysed by sulphuric acid or in other ways than by 

The desirability of some agreement being reached, 
both in the interest of the profession and of the public, 
was pointed out by more than one speaker, while Mr. 
A. H. Allen remarked that he regretted that the vinegar 
manufacturer had sometimes been hardly dealt with by 
the Public Analyst. 

It was hardly surprising, however, in view of the 
divergency of opinions, that the discussion should have 
ended without any definition of " malt vinegar " having 
been formulated by the Society. 

The result has been that individual Public Analysts 
when called upon to examine samples of malt vinegar 
have had to form their own definitions and fix their own 
standards, and conflicting decisions which settle nothing 
are constantly being given in the police courts all over 
the country. 

For example, it was decided some years ago in the 
North of England that a vinegar manufactured from a 
mixture of malt and flaked maize was " malt vinegar," 
and costs were allowed against the county authori- 
ties, whereas in 1912 a Worcestershire bench held that 
flaked maize or maize grits ought not to be a constituent 
of malt vinegar, and fined the defendants. 

We have thus the farcical position that a man is re- 
garded as an honest man for selling in one part of England 


an article for the sale of which in another county he would 
be subjected to a criminal prosecution. 

The want of some authoritative statement has been 
so keenly felt that in 1911 the Association of Vinegar 
Brewers requested the Local Government Board to fix 
a definition for malt vinegar. The Board replied (Dec. 
15th, 1911), that they had no power to fix legal definitions 
for vinegar, but they suggested definitions that might 
be acceptable to all concerned in the manufacture and 
examination of vinegars, viz. : 


" Vinegar is a liquid derived wholly from alcoholic 
and acetous fermentations ; it shall not contain less 
than 4 grammes of acetic acid (CH 3 . COOH) in 100 cubic 
centimetres of vinegar ; it shall not contain arsenic in 
amounts exceeding 0-0143 milligramme per 100 cubic 
centimetres of vinegar, nor any sulphuric or other mineral 
acid, lead or copper, nor shall it contain any foreign 
substance or colouring matter except caramel. Malt 
vinegar is derived wholly from malted barley or wholly 
from cereals, the starch of which has been saccharified 
by the diastase of malt. 


" Artificial Vinegar is any vinegar or substitute for 
vinegar containing or derived from any preparation 
containing any added acetic acid which is not wholly 
the product of alcoholic and subsequent acetous fer- 


mentation. It shall contain not less than 4 grammes 
of acetic acid (CH 3 . COOH) in 100 cubic centimetres of 
the artificial vinegar. It shall not contain arsenic in 
amounts exceeding 0-0143 milligramme per 100 cubic 
centimetres of vinegar, nor any sulphuric or other mineral 
acid, lead or copper, nor shall it contain any foreign 
substance or colouring matter except caramel." 

It will be seen that this definition for malt vinegar 
restricts the use of the term to the products of the mash- 
tun, and excludes those made by the conversion process. 
It thus supports the view put forward by several public 
analysts that the term " malt " should refer to the agency 
by which the starch of the grain is hydrolysed. 

On the other hand, it permits the use of any cereal 
(including rice or maize), provided that sufficient malted 
grain is present to effect the hydrolysis. 

Unfortunately, this definition has not been generally 
accepted by Public Analysts, for since it appeared there 
have been several prosecutions for the sale of vinegars 
derived in part from products other than malt, and 
there has been the usual result of conflicting decisions 
by magisterial benches in different parts of the country. 
It is to be hoped that before* long this definition may be 
legalised by statute so as to put an end to the present 
state of uncertainty and confusion. 

The following analyses, made by the writer, show the 
characters of the products sold as malt vinegar by 
leading manufacturers, the samples having been bought 
at various times during the last twelve years : 





S-O^ I 5 I> CO t' CO 
"3,'S C, ! uO^OO 
O ^ ; ^ 

CO GO CO tO t> 00 

I - 

> iC<|j IP^I-HI (C-li i i le^f^S^C^i i I-H 



Vinegars made by the same manufacturers as Nos. 
IV., XII., and XV., and giving similar analytical results, 
have been made the subjects of prosecution, on the 
grounds of not being wholly malt products. The low 
nitrogen and phosphoric acid results were attributed by 
the defence to the use of cereals other than malted barley- 
In some cases there were acquittals and in others con- 

The vinegar No. XI. was remarkably high in nitrogen 
and abnormally low in phosphates, and for this reason 
the makers were prosecuted, but won their case. The 
explanation of the abnormal figures is that the vinegar 
was brewed from a mixture of green malt and rice, the 
former being responsible for the high nitrogen and the 
latter for the low phosphoric acid. 

Several of the vinegars included in the above table 
were admittedly manufactured by the conversion process. 
No. XVI. was a typical instance, and it was characterised 
by a high percentage of mineral matter, in which, too, 
there was a large proportion of sulphate. 

The low proportion of total solids in No. IX. is unusual, 
and has on more than one occasion been the subject of 
comment. It could be satisfactorily accounted for by 
the fermentation having been carried to a lower point 
than is usually the case. 


Very little cider vinegar is manufactured in this 
country, but in the United States it is in much greater 
demand than either wine or malt vinegar. 

Analyses of twenty-two typical samples of various 


origin were published by Leach and Lythgoe,* and from 
their results they suggest that certain chemical standards 
should be fixed. Thus, in their opinion, pure cider vinegar 
should contain at least 4-5 per cent, of acetic acid and 
2 per cent, of ash (which should be at least 6 per cent, 
of the total solids, and have an alkalinity equivalent to 
at least 65 c.c. ~ acid per 1 grm.). Not less than 50 per 
cent, of the phosphates should be soluble in water. The 
reducing sugars should not vary in amount after inversion, 
and should not exceed 25 per cent, of the total solids. 
The specific rotation of the clarified vinegar should be 
between -0-1 and -4-0 Ventske (200 mm. tube). 
The presence of malic acid should be ascertained by the 
lead acetate and calcium chloride tests (see p. 154). 

In the opinion of Tolman and Goodnow,t the older 
analyses of cider vinegar are not applicable to the vinegars 
which are now being made by the " quick " process. 
Their experiments indicated that the loss in volume 
during acetification was so small that it was possible, 
without correction, to compare the results with those 
given by the original cider. This contained on the average 
7-7 per cent, by volume of alcohol and 0-27 per cent, of 
acetic acid, and yielded a vinegar containing 5-77 per 
cent, of acetic acid and 0-4 per cent, of alcohol, the loss 
of alcohol during acetification being thus over 20 per 

The total solids, ash, and glycerin were but little 
affected by acetification, while the non-sugars were sub- 
stantially the same in the cider and the vinegar. Alde- 
hydic compounds were formed, and it was necessary to 

* J. Amer. Chem. Soc., 1904, xxvi., 375. 
t.7. Ind. Eng. Chem., 1913, v., 928. 


evaporate the vinegar repeatedly to expel these ; other- 
wise the sugars were overestimated by Fehling's solution 
by 0-15 to 0-2 grm. per 100 c.c. 

The fixed acids were greatly reduced by acetification, 
and fell as low as 0-04 per cent, (as malic acid) ; on the 
other hand, the pentosans increased by about 50 per 

The following analysis of a French cider vinegar is 
given by Calvet * : Total acidity as acetic acid, 4-71 ; 
fixed acidity (as H 2 S0 4 ), 0-19; total solids, 1-98; re- 
ducing sugars (as dextrose), 0-27 ; ash, 0-26 ; and alcohol, 
0-7 per cent. 


Wine vinegar is the predominating product of France, 
just as malt vinegar is in this country, and cider vinegar 
in the United States. Red or white wines are used in 
the manufacture, and the resulting vinegars accordingly 
vary in colour. 

As a rule, the acetic strength is considerably higher 
than in the case of malt vinegar, and is usually not less 
than 7 or 8 per cent. The specific gravity is low, owing 
to the small amount of solid matter present. 

An analysis made by the writer of one of the principal 
French wine vinegars sold in this country gave the fol- 
lowing results : Specific gravity, 1-017; acetic acid, 
7-2; total solids, 1-7 ; ash, 0-25; phosphoric acid, 0-042; 
and nitrogen, 0-013 per cent. 

Vinegars made from British wines contain more total 
solids than French wine vinegars, and these are of a more 

* LOG. cit., p. 61. 



viscous character from the presence of the sugar in the 

The distinguishing characteristics of genuine grape 
wine vinegars are the presence of tartaric acid and inositol, 
for the detection of which see pp. 155, 153. 

The following results were obtained in the analysis of 
white wine vinegars by the Municipal Laboratory of 
Paris : 

j Specific 
j Gravity. 







Per cent. 

Per cent. 

Per cent. 

Per cent. 

Per cent. 

Maximum, 1-0213 

3-19 0-46 






1-38 0-56 





1-0175 1-93 0-22 




The presence of glucose vinegar in wine vinegar may 
be detected, according to Delluc,* by the fact that in the 

OY'i'T'Q r*4- 

former the ratio of -^ approximates to unity. This 


is shown by the following analyses of white and red 
vinegars made from coloured glucose syrups : 

White Vinegar. 

Red Vinegar. 

Specific gravity at 15 C., 
Acetic acid, per cent., . . . 
Total solids, per cent., 
Reducing sugars, as dextrose, . 

total solids 







For the method of determining reducing sugars, see 
p. 152. 

* Calvet, loc. cit., p. 61. 


Wine vinegars are frequently adulterated in France 
with spirit vinegar ; or, rather, the vinegar is prepared 
by acetifying a mixture of wine and dilute alcohol. 

Distilled wine vinegar is made by distilling either 
red or white wine vinegar under reduced pressure (see 
p. 135). It is commonly sold under the name of white 
wine vinegar, and this name is also wrongly applied to 
distilled malt vinegar. 


This is made from the whey of milk fortified with 
sufficient sugar to give the alcohol necessary for the 
production of the acetic acid. 

A sample examined by Filaudeau and Vitoux * had the 
following characters : Specific gravity at 15 C., 1-0184 ; 
total acidity as acetic acid, 6-51 ; fixed acidity as lactic 
acid, 0-18 ; total solids, 2-10 ; reducing sugars, as lactose, 
1-44; nitrogenous substances as casein, 0-17; ash, 
0-14 ; sodium chloride, 0-09 ; and insoluble ash (tribasic 
calcium phosphate), 0-11 per cent. 


Vinegar may be made from any fruit containing suffi- 
cient sugar for the production of the necessary alcohol. 

In other cases e.g., raspberry vinegar the vinegar 
is made by steeping the fruit in distilled vinegar and 
sweetening the product with cane sugar. 

A similar process is employed in preparing tarragon 
and other products of the same nature, the herbs being 

* Ann. des Falsificat., 1909, ii., 208. 



steeped in a brewed or distilled vinegar to impart the 
necessary flavour. 


A few years ago a spirited attempt was made in this 
country to create a demand for date vinegar in place of 
malt vinegar. The products put upon the market had a 
characteristic flavour and aroma, somewhat recalling that 
of a wine vinegar. 

Compared with a normal barley malt vinegar, they 
were low in nitrogen and phosphoric acid. Three com- 
mercial samples examined by the writer in different 
years gave the following percentage results : 

Acetic Acid. 

Total Solids. 


Phosphoric Acid. 





















In spite of much advertising, date vinegar never 
became a serious competitor of malt vinegar, and of 
late years appears to have disappeared from the market. 


The manufacture of vinegar from dilute alcohol has 
become a serious competitor of the old-established in- 
dustry of wine vinegar in France, since the product can 
be sold at a much lower price. 

Spirit vinegar is usually coloured with a little caramel, 
to make it resemble wine vinegar more closely. Its 
odour is much more pungent, and lacks the bouquet 


of the wine product. It contains much less solid matter 
and ash than wine vinegar, but differs from dilute acetic 
acid in containing alcohol, aldehyde, and tartaric acid. 

The following analysis shows the composition of a 
typical French product : Total acidity as acetic acid, 
7-68 ; fixed acidity (as H 2 S0 4 ), 0-03 ; total solids, 0-22 ; 
tartaric acid, 0-08 ; and ash, 0-04 per cent. ; ratio : 

f xtract , 34-9. 

Essigsprit or Vinegar Essence. A German product is 
prepared from potato spirit by a fermentation process. 
It usually contains about 11 to 12 per cent, of acetic 
acid, and has a slight yellow tint, and an agreeable aro- 
matic odour. Until recently, it was imported into this 
country in large quantities, and used for pickling purposes 
as a cheap substitute for malt vinegar. 

A typical sample examined by the writer had the 
following characteristics : Acetic acid, 12-3 ; total solids, 
0-16 ; and ash, 0-02 per cent. 

A concentrated acetic acid is also made by neutralising 
the Essigsprit with lime and distilling the calcium acetate 
with sulphuric acid. Spirit acid thus prepared has a much 
more pleasant aroma, and contains fewer impurities than 
much of the wood acetic acid imported into England. 


Wood vinegar, as its name denotes, is nothing more 
than dilute acetic acid, coloured with caramel, and 
sometimes flavoured by the addition of a small quantity 
of brewed vinegar. 

It has a pungent odour of acetic acid, and lacks the 



aroma of malt vinegar, although it is frequently fraud- 
ulently sold under the name of " malt vinegar/' 

The following analyses of commercial samples of 
artificial vinegar were made by the writer during the 
last ten years : 



Sold as 

at 155 C. 





















" Wood 









" Pale malt 








" Double re- 

fined malt 








. . 

" Malt 







' :, ". 

In the case of the " double refined malt vinegar/' the 
whole of the colouring matter could be precipitated by 
fuller's earth, but this was not possible with the last 
sample. It was, therefore, probable that in the latter 
vinegar some of the colour was derived from the addition 
of grain vinegar as a flavouring agent. 

The traces of phosphoric acid and nitrogen were pro- 
bably present in the caramel used for colouring these 
products. The high ash of the last sample was due to 
the presence of 0-18 per cent, of common salt. 

Artificial vinegars usually contain at least 4 per cent, 
of acetic acid, and there have been numerous prosecutions 
for the sale of products of lower acidity (see p. 172). 




British India- 
Vinegar in casks, . . . . 2 per cent, ad valorem. 
Vinegar not in casks, . . . .5 ., 

Vinegar in casks, ..... 2| ,. 
Vinegar not in casks, . . . 5 ,, 

Vinegar not exceeding 8 degrees by Salleron's 

acetimetre, .... per gall. Rs. .0 7 T S T cts. 
(With an additional duty of T 9 T cts. for every degree 
above 8 degrees by Salleron's acetimetre.)* 

Seychelles, . . . . . . 12 1 per cent, ad valorem. 

Vinegar, vinegar essence, and acetic acid vinegar (standard 
as prescribed by Departmental Bye-laws), the product of 
malt, grain, or fruit juice by alcoholic and acetic fermenta- 
tion, containing not more than 6 per cent, of absolute 

acetic acid, per gall. 006 

Vinegar not the product of malt, grain, or fruit juice, per gall. 020 
Solutions containing more than 6 per cent., but less than 

30 per cent., per gall. 039 

For every 10 per cent, additional, . . . ,, 013 

All kinds, per gall. 006 

* See p. 138. 


New Zealand- 
Vinegar not exceeding 6-5 per cent, of acidity as acetic acid, 

per gall. 006 

Otherwise, 7J 

Acetic acid up to 30 per cent, strength, . . per Ib. 00 1$ 

For every 10 per cent, additional acidity, . OJ 

Fiji, per gall. 006 

British South Africa- 
Glacial acetic acid 

(1) In bottles, etc., not exceeding an imperial quart 

Under British preferential tariff, . per gall. 146 

Under general tariff, . . . . 1 12 5 

(2) In larger quantities 

British preferential tariff, ... 140 

General tariff, 1 11 11 

Vinegar, vinegar essence, acetic (other than glacial) and 
pyroligneous acids, not exceeding proof strength 

(1) In bottles, etc., not exceeding 1 quart 

British preferential tariff, 010 

General tariff, . . . . . . .011 

(2) In larger quantities 

British preferential tariff, . . . . .006 

General tariff, . 007 

And in addition in either case for each degree of strength in 
excess of proof 

Under British preferential tariff, . . per degree 003 
Under general tariff, . . . " .' 004 

(Note. " Proof " will be held to be equal to 6 per cent, of absolute acetic 
acid, and shall be determined in the manner prescribed by the Customs. 
In Cape of Good Hope, the sale is prohibited of vinegar to which have 
been added ingredients injurious to health, and which does not contain 
at least 3 per cent, of absolute acetic acid (Act No. 19 of 1908).) 

Nyasaland Protectorate, . . . . . 10 per cent, ad valorem. 

Uganda Protectorate, 10 

British East Africa, 10 


Imported in Zeyla, 5 

Imported in other ports, ....? 



Nigeria, 10 per cent, ad valorem. 

Gold Coast 

Imported west of the Volta, . . . 10 

Imported east of the Volta, . . . 4 

Sierra Leone, 10 

Gambia, . 5 

Vinegar and acetic acid (not exceeding proof strength 

Under British preferential tariff, . . per gall. 4-93 
Under intermediate tariff, . . . 6-17 

Under general tariff, . . . . 7-40 

With additional duties of 0-74d., 0-86d., and 0-99d. for each 

degree under proof. 

(The strength of proof shall be held to equal 6 per cent, of absolute acetic 
acid, and shall be determined in the manner prescribed by the Governor - 


In cask, .per gall. 7-40 

In bottle, 30 per cent, ad valorem. 

Bahamas, . . 20 

Jamaica, ...... . 16f 

St. Lucia, per gall. 004 

St. Vincent, . 10 per cent, ad valorem. 

Barbados, .... . 10 

Grenada, . 10 

Virgin Islands, per gall. 003 

St. Christopher, . ,,004 

Antigua, 004 

Monserrat, .... 004 

Dominica, 003 

Trinidad and Tobago- 
Acetic acid below 6 per cent, strength, . per gall. 006 
Acetic acid above 6 per cent, strength, 026 
Vinegar, 006 

APPENDIX t. 195 

All kinds, ........ 10 percent, ad valorem. 

British Honduras- 
All kinds, 12 

British Guiana 

Vinegar, containing less than 10 per cent, of acetic acid, 

per gall. 005 

Per barrel of 9 gallons, . ..... . . 020 

All kinds, . 8 per cent, ad valorem. 

No import duties are charged in the following countries : 

Aden, Straits Settlements, Hong-Kong, Falkland Islands, N.E. 
Rhodesia, St. Helena, and Gibraltar. 



PRIOR to the year 1872 the only vinegar upon which duty was charged in 
France was that made from beer, the raw materials for which were taxed 
in accordance with a law of 1816. The duty levied in 1872 upon alcohol 
intended for the manufacture of spirit vinegar led to complaints from the 
vinegar makers of the unfair advantage given to the manufacturers of 
wine vinegar, with the result that in 1 875 a uniform tax was imposed upon 
vinegar of every description in accordance with the following tariff. The 
strength of the vinegar is based upon the results obtained with Salleron's 
acethnetre (p. 138). 


Frail cs. 


1. Vinegars containing 8 per cent, or less acetic acid, 

9 to 12 per cent, acetic acid, 

13 to 16 per cent, acetic acid, 

2. Acetic acids and vinegars containing 17 to 30 per cent. 

acetic acid, 18-75 

Acetic acids and vinegars containing 31 to 40 per cent. 

acetic acid, . . . . . . .25 

Acetic acids and vinegars containing more than 40 per 

cent, acetic acid, ...... 52-52 

3. Glacial acetic acid in the solid condition, . . 62 -50 per 100 kilos. 




Acetal, 52. 
Acetaldehyde, 52. 
Acetates of lime, 66. 
Acetic acid, Anhydrous, 59. 

Boiling point of, 76. 

from lime acetate, 66. 

verdigris, 62. 

wood, 65. 

Glacial, 61. 

Manufacture of, 62, 66. 

Optical refraction of, 174. 

Oxidation of, 55. 

Pharmacopceial, 57, 58, 


Properties of, 70. 
Radical, 60. 

Real, 16, 17, 60. 

Specific gravity of, 76. 

bacteria, 32. 
enzymes, 30. 

strength, 137, 172. 

Acetification, Chemical reactions in, 

Early theories of, 20. 

in practice, 115. 

Orleans process of, 100. 

Oxidation in, 50. 

Quick process of, 105. 

Slow process of, 99. 

Acetifiers, 105. 
Acetimetre, 138, 192. 
Acetites, 58. 
Acetometer, 14, 139. 
Acetous acid, 58. 
Acetum, 1. 

distillatum, 57. 

Acetylic acid, 60. 

Acidity, Determination of, 137. 

Standards of, 139. 

Aeration of acetifiers, 1.16. 

devices, 110. 

tubes, 112. 

Alchymy, 1. 

Alegar, 7. 

Alkalinity of ash. 141. 

Alkalised vinegar, 3, 57. 

Analysis of vinegar, 137. 

Aniline colours, 157. 

Antigua vinegar duties, 194. 

Archil, 163. 

Arsenic Committee, 166. 

Estimation of, 166. 

in vinegar, 164. 

Artificial vinegar, 191. 

Definition of, 181, 192. 

Australian vinegar duties, 192. 
standards, 172, 192. 


Bacillus aceti vini, 43. 

acetigenus, 42. 

acetosus, 42. 

curvus, 42. 

Orleanensis, 42. 

oxydans, 42. 

rancens, 43. 

Schutzenbachii, 43. 

vini acetati, 43. 

xylinoides, 43. 

xylinus, 41, 47, 54. 

Bacteria, Acetic, 32. 

Action of light on, 44. 

Involution forms of, 36. 

Pure cultures of, 47. 

Bacterial theories of acetification, 27, 


Bacterium aceti, 31, 33. 
Enzyme of, 31. 



Bacterium Kutzingianum, 33. 

Pasteurianum, 33. 

Barbados vinegar duties, 194. 
Beaufoy's vinegar works, 9. 
Bermuda vinegar duties, 194. 
Bersch's acetifier, 114. 
Berzelius' theory of acetificatlon, 20. 
Boerhave's process, 6, 7. 
Boorde's dyetary, 7. 
British Guiana duties, 195. 
Honduras duties, 195. 

India duties, 192. 

East Africa duties, 193. 
South Africa duties, 193. 

Buchner's acetic enzymes, 30. 

Canada vinegar duties, 194. 
Caramel in vinegar, 150, 181. 

Detection of, 159. 

Estimation of, 162. 

Catalytic theory of acetification, 20. 

Ceylon vinegar duties, 192. 

Chemical standards for vinegar, 171. 

Cider vinegar, 184. 

Citric acid in vinegar, 156. 

Clarification of vinegar, 130. 

Claudon's apparatus, 103. 

Cochineal, 162. 

Coloured wine vinegar, 162. 

Colouring matters, 156. 

Colour measurement, 157. 

Conversion process, 89. 

Copper in vinegar, 163. 

Crystals of Venus, 63. 

Cyprus vinegar duties, 195. 

Date vinegar, 189. 
Diamond vinegar, 19. 
Distillation of vinegar, 135. 

Early apparatus, 3. 

of radical vinegar, 63. 
Distilled verdigris, 62. 

vinegar, 136. 

Domestic manufacture, 4. 
Dominica vinegar duties, 194. 

Dujardin's acetometer, 139. 
Duties on vinegar, 10. 
Colonial vinegar, 192. 


East Africa vinegar duties, 193. 
Enzyme of acetic bacteria, 29. 
Enzymic theories of acotification. 

22, 27, 28. 
Essig-sprit. 64, 190. 

Composition of, 190. 

Ethyl acetate, 53. 
Examination of vinegar, 137. 
Excise Commission on vinegar, 9, 13. 

list of vinegar brewers, 11. 

vinegar duties, 10. 

Fermentation of wort, 91. 
Ferrocyanide precipitation, 131. 
Fiehe's reaction, 161. 
Fielding, 98. 
Fiji vinegar duties, 193. 
Filtration of vinegar, 129. 
Fining of vinegar, 131. 
Flaked maize, 86. 

Composition of, 177. 

rice, ~" 

Formic acid in vinegar, 150. 
French vinegar duties, 196. 
Fruit vinegars, 188. 
Fuller's earth test for caramel, 159. 


Gambia vinegar duties, 194. 
Gelatinised grain, 86. 
Gluconic acid, 54. 
Glucose vinegar, 187. 
Gold Coast vinegar duties, 194. 
Grenada vinegar duties, 194. 
Group system of acetification, 120. 
Gyle, Acetification of, 98. 

Distribution of, 106. 

Preparation of, 77. 

Storage of, 97. 



Hansen's vinegar bacteria. 32. 
Hehner's estimation of sulphuric 

acid, 145. 

Hot liquor backs, 82. 
Hydrocyanic acid in vinegar, 131. 


Import duties on vinegar, 192. 
Indian vinegar duties, 192. 
Inositol in wine vinegar, 153. 
Iron in vinegar, 163. 

Jamaica vinegar duties, 194. 

Lead in vinegar, 163. 

Legislation on vinegar, 10. 

Licences for vinegar, 13. 

Liebig's theory of acetification, 21, 


Light, Action on acetic bacteria, 44. 
Lime acetates, 66. 

acid, 66. 

Lovibond's tintometer, 158. 
Luck's acetifier, 114. 

Maize, Composition of, 175. 

Flaked, 177. 

Malic acid in cider vinegar, 154. 
Malt, Composition of, 175. 

vinegar, 179. 

Definitions of, 178, 181. 

standards, 139, 172, 178. 

vinegars, Composition of, 183. 

Malta vinegar duties, 195. 
Manufacturing processes, Early, 5. 
Mashing machines, 81. 
Process of, 83. 

Mash-tun, 77. 

Mauritius vinegar duties, 192. 

Methyl-acetol, 149. 

Metallic impurities in vinegar, 163. 

Mineral acids in vinegar, 143. 

Montserrat vinegar duties, 194. 

Mother-of -vinegar, 20, 117, 121. 

Mucilage in vinegar, 14. 

Mycoderma aceti, 20, 23, 25, 32, 47. 

mm, 25. 


Nageli's mechanical theory, 27. 
New Zealand vinegar duties, 193. 
Newfoundland vinegar duties, 194. 
Newton's apparatus, 70. 
Nigeria vinegar duties, 194. 
Nitrogen in vinegar, 151, 174. 
Nitrogenous substances in vinegar, 


Numbers of vinegar, 16. 
Nyasaland vinegar duties, 193. 

Oats, Composition of, 175, 176. 
Optical standard for vinegar, 178. 
Orleans process, 100. 
Original solids, 172. 
Otto's acetometer, 139. 
Oudemann's acid table, 75. 
Oxalic acid in vinegar, 156. 
Oxidation, Chemical process of, 68. 
Ozone in acetifiers, 69. 

Papua vinegar duties, 192. 
Parachute, Yeast, 95. 
Pasteur's acetification theory, 23. 
Pharmacopoeial requirements for 
acid, 73. 

vinegar, 17. 

Phosphates in vinegar, 174. 

Estimation of, 152. 

Plate acetifiers, 115, 117. 



Platinum black oxidation, 51, 56, 


Popped barley, 86, 177. 
Precipitation processes, 131. 
Proof acid, 16, 193, 194. 

vinegar, 12, 14, 193, 194. 

Prussic acid in vinegar, 132. 
Pyroligneous acid, 65, 66. 

Estimation of strength of, 


Quick process, 105. 

Radical vinegar, 16, 60. 
Rapes, 129. 

Real acetic acid, 16, 17, 60. 
Refrigerators, 91. 
Rozier's experiment, 51. 
Rye, Composition of, 175. 


Salleron's acetimetre, 138, 196. 
Schultze's extract table, 142. 
Seychelles vinegar duties, 192. 
Sierra 'Leone vinegar duties, 194. 
Singer's apparatus, 114. 
Siphon distributors, 109. 
Slow process, 99. 
Soda acid, 66, 67. 
Somaliland vinegar duties, 193. 
South Africa duties, 193. 
Sparge in acetifier, 107. 

mash -tun, 80. 

Specific gravity of acetic acid, 75. 

vinegar, 141. 

Spirit acid, 190. 

of vinegar, 3. 

vinegar, 64, 101. 

vinegars, 189. 

St. Christopher vinegar duties, 194. 
St. Lucia vinegar duties, 194. 
St. Vincent vinegar duties, 194. 
Stahl's theory, 21. 

Standards for vinegar, 172. 
Sterilisation of vinegar, 132. 
Still for vinegar, 135. 

residues, 136. 

Strength of vinegar, 19, 61, 139, 172. 
Succinic acid in vinegar, 54. 
Sugar, Addition to wort, 88. 
Estimation of, 152. 

Sulphates in vinegar, 148. 
Sulphuric acid, 12, 14, 144. 

Combined, 148. 

Estimation of, 145. 

Tarragon vinegar, 188. 
Tartaric acid in wine vinegar, 15o. 
Temperatures in acetification, 118. 
Tin in vinegar, 163. 
Tintometer, 158. 
Tipping trough, 108. 
Tobago vinegar duties, 194. 
Torrefied barley, 86. 

Composition of, 177. 

Total solids, 140. 

Standard for, 172. 

Trade numbers, 16. 
Trinidad vinegar duties, 194. 


Uganda vinegar duties, 193. 
United States vinegar standard, 17* 
Uvula aceti, 21. 

Verdigris, 62. 

Vinegar, Alkalised, 57. 

Artificial, 181, 191. 

bacteria, 31. 

- beer, 8, 12. 
Cider, 184. 

Commission, 9, 13. 

Date, 189. 

- Distilled, 136. 

eel, 122. 

fields, 98. 



Vinegar fly, 128. 

Malt, 139, 179. 

manufacturers, 111. 
mite, 126. 

plant, 8, 54. 

Proof, 12, 14, 193, 194. 

Radical, 16, 57, 60. 

- stills, 13, 135. 

Wine, 183, 186. 

Virgin Island vinegar duties, 194. 


Wagenmann's graduator, 113. 

Whey vinegar, 183. 

White wine vinegar, 136, 188. 

Wine vinegar, Composition of, 183. 
Distilled, 183. 

Manufacture of, 100. 

White, 136, 188. 

Wood acid, 65. 
vinegar, 190. 

Yeasts for vinegar brewing, 93. 

Zooglceal condition of bacteria, 34. 







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