BiocHEMiCAL Bulletin 



Volume III OCTOBER, 191 3 No. 9 



A MODIFIED HEMPEL GAS PIPETTE 



STANLEY R. BENEDICT 

 (Department of Chemistry,Cornell University Medical College, New York City) 



(WITH PLATE l) 



In the use of the Hempel pipette the shaking necessary to obtain 

 complete absorption of a gas is undesirable from two Standpoints. 

 It is time-consuming and, unless the connections are exactly right, 

 air is apt to enter the apparatus during the protracted period of 

 vigorous shaking which is often necessary. 



Van Slyke, in his latest apparatus for amino nitrogen determina- 

 tion, employs a small motor for shaking the pipette, and thus obvi- 

 ates the awkward procedure of shaking by hand. 



The modified form of apparatus here described was designed 

 to eHminate entirely any necessity for shaking in the Hempel appa- 

 ratus to secure complete absorption. The figure is almost self-explan- 

 atory (Plate i). At p is a three-way stop-cock, through which the 

 gas is allowed to enter b through the tube h. The gas thus bubbles 

 through the Solution contained in b, collects at the top, and is drawn 

 out through the tube d_, after turning p. The intimate mixture of 

 gas and liquid effected by bubbling the gas through the Solution is 

 sufficient to ensure a complete reaction if the process is repeated once 

 er twice. We have used the apparatus in this laboratory in a large 

 number of determinations, with highly satisfactory results. 



