
CHAPTER Xi! 
WAS PASTEUR RIGHT IN HIS EXPLANATION OF THE 
FACT THAT GUARDED NEUTRAL OR SLIGHTLY 
ALKALINE INFUSIONS PREVIOUSLY HEATED TO 
100° C. WILL OFTEN FERMENT? 
ERHARDT says in his ‘ Traité de Chimie 
Organique” (t. iv., 1856, p. 547): ‘‘ Many 
substances which alone or in the moist state are not 
oxidised by the air, undergo such a process as soon 
as they come into contact with an alkali. Thus 
pure alcohol exposed to the air will remain pure 
indefinitely, and without becoming acid; but if a 
little potash be added to it, it speedily absorbs 
oxygen and becomes converted into vinegar and a 
brown resinous substance. It is clear from this that 
potash ought to favour certain fermentations, since 
it favours the absorption of oxygen, and the presence 
of this helps to develop ferments.” He also says 
(loc. czt., p. 556), “It is known that meats and 
vegetable substances soaked in vinegar are preserved 
from decomposition, at least for a certain time... . 
The majority of acids produce the same effect as 
vinegar.” 
Facts of this kind were doubtless well known 
to Pasteur, and he could also easily have satisfied 
himself concerning the relative amount of fermen- 
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