142 PROCEEDINGS OF SECTION B. 
producing bacteria; in some cases from lactose, in others 
from glucose or saccharose. The butyric bacteria first pro- 
duce lactic acid, which they convert to butyric. It is, 
therefore wrong to suppose that a bacterium which produces 
lactic acid should be called a lactic bactertum. The 
quantity of acid produced and its purity must be taken into 
account. In many of the industries in which the action 
of lactic acid is required it is preferable to use the acid itself, 
and not the bacteria, for by doing so the action is completely 
under control. 
In the manufacture of the acid any raw material that 
will furnish a solution of glucose at the cheapest possible 
rate is used. After saccharification, the wort is brought 
to a certain gravity, just as in brewing, boiled and cooled 
down to 45° C., when it is infected with a starter prepared 
from a pure culture of a selected lactic bacterum. The 
fermentation is conducted at about 45°, and the liquor, 
which should have been slightly acid, is treated with chalk, 
or with milk of lime, from time to time, so that the acidity 
is maintained at from 0-2 to 0:5 per cent. At the close 
of the fermentation the liquor is heated to kill off the bac- 
teria. After the dead bacteria are removed by filtration, 
the liquor is evaporated, and the calcium lactate allowed to 
erystallise. Tha crude lactate is decomposed with sulphuric 
acid, and the lactic acid evaporated down to market 
strength. 
The skill of the technologist is employed in regulating the 
temperature to prevent the alcohol and the acidity to 
check butyric fermentation. For economic production, over 
90 per cent, of the glucose must be fermented, and this is 
managed, inter alia, by the attenuation of the wort and care 
in the selection of the bacterium. A point of interest in 
the process is the temperature at which the fermentation 
is conducted. On the small scale, in the laboratory, a 
temperature of 37° is equivalent to 45° in a 5000-gallon vat. 
Something of a similar nature occurs in the fermentation 
of must, where the fermentation generally goes on at a 
temperature at which the yeasts would not grow in the 
laboratory. 
Lactic acid is chiefly used in the dyeing of wool, and as a 
menstruum for obtaining a solution of aluminium, tin, and 
calcium, with one acid in mordanting cotton goods. It 
also promises to play an important part in the tanning of 
leather. 
