102 
THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
[August 6, 1870. 
chief experiments made in reference to the disap¬ 
pearance of ammonia are the following :— 
I. 100 grm. sugar, dissolved in a litre of yeast-water, 
mixed with a trace of yeast, and left to ferment. 
The yeast-water contained .... ’038 grm. ammonia. 
The fermented liquid contained *020 „ 
Deficiency.’018 „ 
II. 100 grm. sugar, 10 of fresh yeast, mixed with '2 tar¬ 
trate of ammonia. The liquid contained— 
Before fermentation .*0185 grm. ammonia. 
After fermentation. - 0015 ,, 
Deficiency .-0170 ,, 
III. 19’57o grm. sugar, "525 yeast, and ’475 tartrate of 
ammonia. The liquid contained— 
Before fermentation.*088 grm. ammonia. 
After fermentation ."071 „ 
Deficiency.’017 „ 
In these three experiments, the quantities of am¬ 
monia in the fermented liquids were in the ratio, 
1:2:5, and it is rather striking, that the deficiencies 
were nearly the same in all three instances. It is, 
moreover, not easily explicable that, in these three 
experiments, a part of the ammonia should have 
served for the production of a nitrogenous constitu¬ 
ent, while in the fermented liquid there was still a 
residue of nitrogenous substances, which are admir¬ 
ably suited as food for yeast-cells, and certainly 
much more so than ammonia ; in fact, the fermenta¬ 
tion would have gone on just the same in the three 
mixtures 'without any addition of ammonia. 
The constancy in the loss of ammonia, notwith¬ 
standing the dissimilar quantities of ammonia, 
would appear rather to indicate an error in the me¬ 
thod of determination common to all the experi¬ 
ments ; but I will not lay any stress on this suppo¬ 
sition. The confirmation of the most important thing, 
viz. the increase of yeast by the ammonia in the 
fermented mixture, has been left entirely unheeded 
by Pasteur. 
It is clear that if he had added an ammonia salt 
to one of two mixtures of a known quantity of sugar 
with the same quantity of yeast-water and a trace 
of yeast, lie should, in the two cases, have found a 
difference in the quantity of yeast produced. If the 
ammonia had been applicable for the production of 
yeast, the mixture with ammonia should have 
yielded more yeast than the others 'without ammo¬ 
nia. 
The capability of ammonia to serve for the forma¬ 
tion of yeast is, therefore, not inferred Rom the 
fact that the quantity of yeast was increased in the 
presence of ammonia, but from the fact, that the de¬ 
termination of ammonia in the fermented liquid 
showed a loss. The only satisfactory evidence in 
favour of Pastern’s view, that the ammonia contri¬ 
buted to the formation of yeast is, as already stated, 
yet to be furnished. 
The experiments of Duclaux * seem to admit of 
the inference, that ammonia has no influence on the 
formation of yeast. He fermented 40 grm. of sugar 
with 15 grm. yeast and 1 grm. dextro-tartrate of 
ammonia, and found that the yeast was reduced 
from 2'5011 grm. to 2'326 grm., or about 8 per cent., 
as in Pasteur’s experiment without ammonia. But 
in all liquids that contain material adapted for feed¬ 
ing yeast, there is an increase hi the quantity of 
yeast. However, I will not lay any further weight 
on these considerations, but will turn to Pasteur’s 
main experiments, by which he believes that the 
formation of yeast from non-nitrogenous substances 
and ammonia has been directly proved. 
When a mixture of 10 grm. sugar, 100 c.c. water, 
TOO grm. tartrate of ammonia, and '075 to ’080 grm. 
yeast-asli, was mixed with a trace of yeast, evolu¬ 
tion of carbonic acid commenced in a few hours'; the 
sugar was partially decomposed and the yeast in¬ 
creased ; ‘0062 grm. of ammonia had disappeared 
(= 5'2 milligrams nitrogen), while the yeast pro¬ 
duced weighed ‘043 grm., and this should have 
contained the nitrogen of the ammonia, or upwards 
of 11 per cent, of nitrogen. Pasteur has described 
very minutely the progress of this experiment, and I 
believe it is possible to infer with tolerable certainty 
from liis account, that there was essentially no 
vinous fermentation, but that a true lactic fermenta¬ 
tion took place. There was, indeed, a sensible 
production of alcohol, but I suspect that the quan¬ 
tity of alcohol was not determined by him, because 
it was too small. However, 4 5 grm. sugar was de¬ 
composed, and it was, for the most part, converted 
into an organic acid, equivalent to *597 sulphuric 
acid. This organic acid consisted chiefly of lactic 
acid. 
I have many times repeated tliis experiment with 
great care, and obtained nearly the same results as 
Pasteur so far as relates to the formation and increase 
of the yeast. The only alteration that I made in the 
mixture consisted in heating the liquid to boiling, 
and allowing it to cool in the vessel before adding 
the yeast. In another instance I took sugar that 
had previously been heated to 160° C., at which tem¬ 
perature it is known not to lose its capability of fer¬ 
menting.* I also found that, after twenty-four hours, 
some carbonic acid was evolved, and that the greater 
part of the sugar was converted into an organic acid, 
the nature of which was not determined. 
From one of these mixtures I distilled off 25 c.c., 
and determined the specific gravity of the distillate 
to be '99968, or scarcely different from that of water. 
By means of Lieben’s delicate test, however, alcohol 
could be detected in it. 
There is no doubt that, under these conditions, a 
decomposition takes place, and that there is some 
formation of alcohol, which probably originates from 
the yeast added, although its quantity is so small. 
But the whole process lias no resemblance to that 
taking place in a sugar solution, to which so much 
nitrogenous substance has been added, as would cor¬ 
respond to the nitrogen of 'I grm. neutral tartrate of 
ammonia (= 15'2 milligrams nitrogen). For instance, 
in a mixture of 100 c.c. sugar solution, containing 
5 grm. sugar and 16 c.c. of a decoction of fresh yeast, 
there was, after adding a trace of yeast, in eight 
hours a sensible fermentation; successive bubbles of 
carbonic acid were evolved slowly but continuously, 
while the bottom of the vessel became covered with 
a distinct layer of very white yeast, that increased in 
thickness until all the sugar was decomposed. 
I am fully conscious that, in researches of tliis land, 
a negative argument does not excite any special con¬ 
fidence, for it does not require any particular art not 
# ‘Comptes Kendus,’ fix. 450. 
* According to analyses made by Prof. Volfiard at the in¬ 
stigation of Prof. Nageli, the wliitest and most transparent 
crystals of sugar always contain nearly "o per cent, of nitrogen. 
