Note 118 — Chapter VI · THE PHYSIOLOGICAL THEORY OF FERMENTATION.

[It may be useful for the non-scientific reader to put it thus:—that the 25 c.c. which escaped, being a fair sample of the whole gas in the flask, and containing (1) 25 - 20·6 = 4·4 c.c., absorbed by potash and therefore due to carbonic acid, and (2) 20·6 - 17·3 = 3·3 c.c., absorbed by pyrogallate, and therefore due to oxygen, and the remaining 17·3 c.c. being nitrogen, the whole gas in the flask, which has a capacity of 315 c.c., will contain oxygen in the above proportion, and therefore its amount may be determined, provided we know the total gas in the flask before opening. On the other hand, we know that air normally contains, approximately, 1/5th its volume of oxygen, the rest being nitrogen, so that, by ascertaining the diminution of the proportion in the flask, we can find how many cubic centimetres have been absorbed by the yeast. The author, however, has not given all the data necessary for accurate calculation.—D.C.R.]