256 STUDIES ON FERMENTATION. 



fact, the flask A with its neck drawn out and closed in a 

 flame, after the introduction of a thin layer of some saccharine 

 juice impregnated with a trace of pure yeast. The following 

 are the data and results of an experiment of this kind. 



We employed 60 c.c. (about 2 fluid ounces) of yeast- water, 

 sweetened with 2 per cent, of sugar and impregnated with 

 a trace of yeast. After having subjected our vessel to a 

 temperature of 25° C. (77° F.) in an oven for fifteen hours, 

 the drawn-out point was brought under an inverted jar filled 

 with mercury and the point broken ofl". A portion of the gas 

 escaped and was collected in the jar. 



For 25 c.c. of this gas we found, after absorption by potash, 

 20*6, and after absorption by pyrogallic acid, 17*3. Taking 

 into account the volume which remained free in the flask, 

 which held 315 c.c, there was a total absorption of 14'5 c.c. 

 (0*88 cub. in.) of oxygen.* The weight of yeast, in a state 

 of dryness, was 0*035 gramme. 



It follows that in the production of 35 milligrammes (0*524 

 grain) of yeast there was an absorption of 14 or 15 c.c. (about 

 I cubic inch) of oxygen, even supposing that the yeast was 

 formed entirely under the influence of that gas : this is equiva- 

 lent to not less than 414 c.c. for 1 gramme of yeast (or about 

 33 cubic inches for every 20 grains). f 



* [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 jiroportion, 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, 

 ith 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.] 



t This number is probably too small ; it is scarcely possible that the 

 increase of weight in the yeast, even under the exceptional conditions of 



