144 REPORT OF THE CHEMIST OF THE 
(5) The addition of larger amounts of sugar along with yeast 
delayed the souring of the milk to such an extent that coagulation 
did not occur for five or six days or longer. 
(6) In the samples to which yeast and the larger amounts of 
sugar (20 to 40 grams) were added, the acidity appeared to be 
greater for one or two days than in the case of untreated milk. 
This was probably due to the action of carbon dioxide upon the 
calcium of the calcium casein of the milk, by which free casein 
was formed, and this on titration would neutralize more alkali and 
thus increase the apparent acidity of the milk. A part may be due 
to the action of carbon dioxide upon the phosphates of milk and a 
small part to such by-products of the alcoholic fermentation as have 
power to neutralize alkali. P 
(7) In general, this set of experiments appeared to indicate that 
the formation of acid and final souring of milk are delayed when 
milk contains yeast and sugar and these undergo alcoholic fermen- 
tation. The results could not decisively furnish information as to 
whether the active agent in delaying acid formation was the carbon 
dioxide or some other fermentation product. To settle this point 
other experiments were necessary. 
} 
SECOND EXPERIMENT: EFFECT OF PASSING STREAM OF CARBON DIOXIDE 
GAS THROUGH MILK UPON KEEPING POWER. 
We tried the effect of passing a stream of carbon dioxide gas 
through milk at pressures varying from that of the atmosphere to 
four or five pounds, but no effects on the keeping power of the 
milk were noticeable. 
It occurred to us that only such amounts of carbon dioxide gas 
would be efficient as might be obtained under higher pressure. As 
a clue to this point, the pressure of carbon dioxide formed by kumiss 
several days old was measured and found to be 45 pounds to the 
square inch. We then decided to repeat our previous experiments 
and at the same time, for comparison, to treat milk under pressure 
with carbon dioxide alone.? 
‘It may be well to mention that after this work was finished our attention 
was called to a note by Mowry and Michel (Compt. Rend., 115: 959-960, 
1892), in which they state as a result of some of their work that milk 
saturated with carbon dioxide would keep at a low temperature for eight 
days. They also state that the effect of the carbon dioxide is merely to 
check the growth of the bacteria. The bacteria are not killed. 
