336 



LOUIS PASTEUR 



The impregnation took place on February loth, and on 

 March I5th the liquid was nearly saturated. The bubbles 

 then began to lodge in the bent part of the exit-tube, at 

 the top of the flask. A glass measuring-tube containing 

 mercury was now placed with its open end over the point 

 of the exit-tube under the mercury in the trough, so that 

 no bubble might escape. A steady evolution of gas went 

 on from the I7th to the i8th, 17.4 cc. (1.06 cubic inches) 

 having been collected. This was proved to be nearly ab- 

 solutely pure carbonic acid, as indeed might have been 

 suspected from the fact that the evolution did not begin 

 before a distinct saturation of the liquid was observed. 3 



The liquid, which was turbid on the day after its im- 

 pregnation, had, in spite of the liberation of gas, again 

 become so transparent that we could read our handwriting 

 through the body of the flask. Notwithstanding this, there 

 was still a very active operation going on in the deposit, 

 but it was confined to that spot. Indeed, the swarming 

 vibrios were bound to remain there, the tartrate of lime 

 being still more insoluble in water saturated with carbonate 

 of lime than it is in pure water. A supply of carbonaceous 

 food, at all events, was absolutely wanting in the bulk of the 

 liquid. Every day we continued to collect and analyze 

 the total amount of gas disengaged. To the very last 

 it was composed of pure carbonic acid gas. Only during 

 the first few days did the absorption by the concentrated 

 potash leave a very minute residue. By April 26th all 

 liberation of gas had ceased, the last bubbles having risen 

 in the course of April 23rd. The flask had been all the 

 time in the oven, at a temperature between 25 C. and 

 28 C. (77 F. and 83 F.). The total volume of gas 

 collected was 2.135 litres (130.2 cubic inches). To obtain 

 the whole volume of gas formed we had to add to this 

 what was held in the liquid in the state of acid carbonate 

 of lime. To determine this we poured a portion of the 

 liquid from the flask into another flask of similar shape, 

 but smaller, up to the gaugemark on the neck. 1 This 



1 Carbonic acid being considerably more soluble than other gases possible 

 under the circumstances. ED. 



8 We had to avoid filling the small flask completely, for fear of causing 

 some of the liquid to pass on to the surface of the mercury in the meas- 



: 



