EXPERIMENT STATION BULLETINS. 



265 



arm, to a modified Hempel pipette specially made for the purpose in which all rubber 

 connections were excluded. The bulb of the pipette, the nearest the milk container 

 when connected, was so made as to be above the second bulb, next to the Geissler pump. 

 From the very top part of the bulb next to the container extended upright 5 cm. in length, 

 a capillary tube; this then turned to a horizontal position for 10 cm.; finally turned 

 downward in a vertical direction and connected with the mercury valve of the con- 

 tainer, previously described, by means of its female portion. In the middle of the 

 horizontal portion of this capillary connecting tube was another three way stop-cock 

 which facilitated the filling of the tube with mercury. Therefore the container could 

 be directly connected with the pipette through the capillary tube by means of the 

 mercury connection. Before beginning to pump the gas off, the upper bulb of the 

 pipette and the capillary arm were filled completely with dry mercury by means of the 

 three way stop-cocks. This was done so effectually that no traces of air were present. 

 A Geisslers pump was then attached to the upper stem of the lower bulb of the pipette, 

 the air was removed, thus creating considerable pressure upon the mercury in the 



M,:liM] r 



pipette. The stop-cock in the upper arm of the container was then turned so that the 

 gas from the milk could escape and be drawn over into the upper bulb of the pipette 

 and thus collected there. When the operation of pumping was completed the stop-cock 

 in the upper arm of the container was again turned off. To this three way stop-cock 

 was attached a Hempel burette, filled with mercury, by means of pressure tubing also 

 filled with mercury. (It is understood that all rubber tubing connections throughout 

 the entire experiment were further safeguarded by wiring.) 



As soon as the pressure of the pump was released and reduced to normal conditions 

 all of the gas was drawn over through the capillary tube and three way stop-cock into 

 the burette where it was held for analysis. In carrying out the analyses of the gases 

 we used Hempel's methods entirely, employing his pipette and White's (12) burette 

 corrected for temperature and barometric pressure. The carbonic acid gas was absorbed 



(12.) Jour, of the American Chemical Society, Vol. XXII. No. 6, 1900. 

 .34 



