1876.] Physico -Chemical Theory of Fermentation, ^c. 



153 



vessel was at once immersed with its neck downwards in a can of boiling 

 water for from four to fifteen minutes, so as to expose it and its con- 

 tents for an additional period to a temperature of 212° F. (100'^ C). 



The urine was thus boiled in its unaltered acid state and sterilized. 

 After the retorts had cooled the liquor potassae was liberated from its 

 tube in all but one of the batch, which was kept as a control experiment. 

 The liberation was easily effected. It was only necessary to give the 

 retort a sudden shake so as to drive the capillary neck of the enclosed 

 tube against its side. The tube was thus broken and immediately (owing 

 to the comparative vacuum within the retort) the liquor potassse was 

 sucked out and mixed with the fluid which it was destined to neutralize. 



The result of these experiments was similar to those executed with the 

 plugged flasks and liquor-potassse tubes. The boiled caustic potash 

 added afterwards within the sealed retorts caused the previously barren 

 fluids to ferment and swarm with Bacteria. The fluid in the control 

 experiment remained pure, though after several days, or longer, it also 

 could be made to ferment by breaking the liquor-potassse tube and 

 replacing the retort in the warm chamber. 



Effects of liherating Oxygen by Electrolysis vnthin the closed Retorts. — 

 A few other experiments were made with retorts to which platinum 

 electrodes had been fitted. These contained, as before, measiu'ed amounts 

 of urine, together with liquor-potassae tubes. All the preliminary stages 

 were similar to those of the experiments above recorded ; but just before 

 breaking the liquor-potassoB tubes in these farther experiments, oxygen 

 and hydrogen were liberated from the boiled urine by electrolysis. 



The result in the few experiments made was very remarkable. Under 

 the combined influence of liquor potasste, oxygen, and the high tempe- 

 rature of 122° F. (50° C), the sterilized urine fermented and swarmed 

 with Bacteria within the closed retorts in from 7-12 hours — that is, in a 

 much shorter time than would suflice for the occurrence of similar changes 

 in unboiled urine freely exposed to the air. 



Behaviour of some specimens of v.naltered Acid Urine under the influence of 

 the High Generating Temperature of 122'^ F. (50"^ C). 



In the course of the previous experiments it was found that occasion- 

 ally a specimen of boiled urine would ferment at a temperature of 122" F. 

 without the addition of liquor potassse. This was afterwards ascertained 

 to occur invariably (with the urine experimented upon) when the acidity 

 of the fluid was not higher than would be represented by six minims of 

 liquor potass£e to the ounce (or about 1^ per cent.). TTrines slightly more 

 acid than this sometimes did and sometimes did not ferment without liquor 

 potassse ; but when the acidity exceeded what would be equivalent to 

 two per cent, of hquor potasste, the fluid did not ferment under the 

 influence of the high generating temperature alone. Urines of all 

 degrees of acidity, however, were found to ferment under the combined 



VOL. XXY. M 



