RICHARDS. — MODIFICATIONS OF HEMPEL'S GAS-APPARATUS. 277 



inventions do not always stand the test of indiscriminate use. Accordingly 

 a large class in gas analysis has been asked to use the ne*v devices, with 

 favorable outcome. 



The pipette and burette were tested as follows. A definite amount of air 

 was run into the burette, and the volume measured with the usual care. 

 Pure carbon dioxide was then run in from a generator, and the gain in 

 volume was noted. This known mixture of air and carbon dioxide was 

 run over into the new pipette, and after suitable shaking the residual air 

 was returned to the burette and measured. 



These figures, taken at random from among the results of the class, 

 agree with one another as well as could be expected ; and since the posi- 

 tive deviation balances the negative, there is no constant error. No 

 trouble was experienced as to manipulation. 



I am much indebted to Mr. Bisbee, the assistant, and to the gentlemen 

 of the class in gas analysis, for their kindness in carrving out the practical 

 trial of the apparatus. 



Cambridge, May 3, 1901. 



