124 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
[August 13, 1870. 
Oil of turpentine, ether, aldehyde, or bitter almond 
oil, that have been shaken with air, will convert sul¬ 
phurous acid into sulphuric, and decolorize tincture 
of indigo; even sulphurous acid, and many solid or¬ 
ganic substances, will, while undergoing oxidation, 
determine the oxidation of other substances, organic 
and inorganic. 
Tliis remarkable property was noticed more than 
thirty years ago by l)e Saussure* as being possessed 
by putrefying substances; and it is worth while to 
recall to mind his experiments. “ When vegetable 
mould, or the humus contained in various soils, or 
moist seeds that have undergone fermentation, are 
kept under a bell jar filled with oxygen, this gas is 
gradually converted into carbonic acid.” Though 
this is not very remarkable, the following fact is veiy 
much so :—“ If hydrogen gas be mixed with the 
oxygen it is converted into water. As the hydrogen 
disappears, half of its volume of oxygen disappears 
also.” 
“ When carburetted hydrogen, carbonic oxide, or 
the hydrogen obtained by the action of red-hot iron 
on w r ater, are, in this experiment, substituted for hy¬ 
drogen obtained by dissolving zinc with acids, they 
do not undergo oxidation.” Saussure adds, “ These 
decaying substances act upon the mixture of oxygen 
with hydrogen in the same way as platinum, and 
those gases which prevent the action of platinum 
also prevent the combination in this case.” 
It seems to me nothing can be more evident than 
that the oxidation of hydrogen in contact with de¬ 
caying materials and oxygen is a purely chemical 
process that has been further elucidated by the ex¬ 
periments of Schonbein and by the formation of 
ozonized oxygen. 
The oxidation of ammonia to nitric acid in the 
presence of alkaline bases and in soils containing 
much humus is also due to the same circumstance. 
Evidently, decaying substances are capable of con¬ 
densing oxygen from the air and bringing it into 
such a condition that it can combine with other sub¬ 
stances which do not combine with oxygen at low 
temperatures, except when aided by these absorbents 
of oxygen. 
Let us suppose that, in place of the hydrogen in 
Saussure’s experiment, alcohol vapour were brought 
in contact with decaying w r ood or some material acting 
in like manner, and then we shall have an explana¬ 
tion of the production of acetic acid from alcohol. 
In consequence of the oxidation of its hydrogen, al¬ 
cohol is [first converted into aldehyde, and this by 
further oxidation passes into acetic acid. It is known 
that the theory of acetification was first suggested by 
Dobereiner in his memoir on “ the behaviour of pla¬ 
tinum sponge towards air and alcohol vapour;” and 
that the method introduced by Schiitzenbacli in 1823 
for the manufacture of vinegar is based on this 
theory. 
In this operation wood-shavings or fragments of 
charcoal are used for determining the oxidation. At 
one of the largest vinegar factories in Germany, the 
dilute alcohol receives no admixture during the whole 
operation; besides air and wood-shavings or char¬ 
coal, there is no other material concerned, and the 
fresh supply of dilute alcohol is only mixed with a 
little of the unfinished vinegar from a previous ope¬ 
ration. The proprietor of these works, Hr. Riemer- 
sclimied, sent me some of the beech-wood shavings 
which had been used uninterruptedly for twenty- 
five years; and in reply to my inquiry as to whether 
the Mycoderma aceti took part in the production of 
vinegar, he states that, so far as can be seen, the 
shavings that have been thirty years in use are quite 
free from that fungus. According to his data, a 
hectolitre of wine containing 9 per cent, of alcohol, 
is converted into vinegar within three days. 
If the fermentation of acetic acid were determined 
by the growth and development of the vinegar- 
plant, it might be expected that this fungus would 
increase in some proportion to the acetic acid formed 
when alcohol was used, as well as when fermented 
liquors were used. This really takes place when 
wine is used, and especially with fermented beer- 
wort, which contains nitrogenous material and phos¬ 
phates that serve as food for the Mycoderma aceti. 
The production of the fungus is a continual source 
of hindrance in factories where beer-wort is used, 
since the interstices of the wood-shavings are gra¬ 
dually stopped up by its growth, and thus free circu¬ 
lation of air is prevented so far as to stop the forma¬ 
tion of vinegar. 
How r ever, the dilute alcohol used in vinegar works 
does not contain food for the vinegar-plant, and yet 
acetic acid is produced without its aid. If the spirit 
contains amylic alcohol, valerianic acid also is 
formed. 
Microscopic examination of the wood-sliavings 
sent me by Hr. Riemerschmied did not show the 
presence of Mycoderma aceti. They had merely the 
brown colour of decayed w T ood, and the structure 
was quite unaltered. 
It is entirely beyond doubt that the vinegar- 
plant is capable of causing the conversion of alcohol 
into acetic acid, but tliis effect is not the result of a 
physiological process. For the conversion of alcohol 
into acetic acid oxygen only is necessary, and that 
the Mycoderma aceti does not and cannot furnish. 
Analyses of the air discharged from the vessels where 
the vinegar is made, show that the oxygen con¬ 
sumed hi the oxidation of alcohol is taken from the 
air, and the only part taken by the vinegar-plant hi 
the process is that of determining the absorption of 
oxygen ; it is active only in virtue of this chemical 
property, and it can be replaced by a large number 
of dead materials or parts of plants.'" 
These well-known facts prove that the production 
of acetic acid from alcohol is not brought about by a 
physiological process; acetic acid is not a product of 
the Mycoderma aceti, but a product of oxidation. 
(To be continued.') 
* The comparatively large amount of nitrogenous material 
remaining after the fermentation of beer-wort or wine-must,, 
containing little sugar, is a main cause of the beer or wine 
turning sour, for that nitrogenous material has a great ten¬ 
dency to attract oxygen. In German breweries gypsum is 
added to the boiling wort with the object of reducing the 
amount of nitrogenous material, and fermentation is carried 
on at a low temperature to avoid formation of acetic acid. 
In the manufacture of spirit from potatoes and maize, sul¬ 
phurous acid has been found very useful for augmenting the 
yield of alcohol by preventing formation of acetic acid. The 
maize is mashed with water containing some sulphurous acid. 
In Austria and Hungary this procedure has been dealt with 
as a mystery, and manufacturers have paid large sums for 
being taught it. I have ascertained, by special experiments,, 
that a moderate amount of sulphurous acid has scarcely any 
influence on the fermentation of beer-wort or of sugar with, 
yeast. 
* Bibl. Univ. de Geneve, Feb. 1834. 
