290 A. M. GURJAR 



F. The automatic pipette is connected through a three-way 

 cock to the stock bottle containing the Ba(0H)2 solution and is 

 filled by raising the pressure in the bottle by means of the rubber 

 bulb, L, opening the pinch-cock, 2, and turning the glass cock 

 to the proper position. The pipette is drained by turning the 

 stop-cock over, and a mouth piece, /, is provided with an inter- 

 mediate soda-lime tube, S. 



One of the arms of the U-tube, F, is fused to a cylindrical 

 separatory funnel, G, which serves as a container for the. water 

 used in diluting the Ba(0H)2 solution and in washing out the 

 tower when the aspiration is completed. This funnel is filled by 

 raising the pressure in the large stock bottle of water with the 

 rubber bulb, L, and opening the pinch-cock S. The other arm 

 of the U-tube is connected to the intake of the meter, M, which 

 in turn is connected to the aspirator. This arrangement makes 

 unnecessary a third hole in the stopper, E. The U-tube and auto- 

 matic pipette are supported by clamps attached to a standard. 



TECHNIQUE OF THE DETERMINATION 



Clean glass beads are placed in the tower, C, to a depth of 

 from 16 to 20 inches, the depth depending upon the quantity 

 of Ba(0H)2 solution to be used. The stopper, £',is placed tightly 

 in the adapter, D, at the top of the tower, and carbon dioxide-free 

 air is aspirated rapidly through the beads and tower to free 

 them of CO2 Alter about five minutes of \dgorous aspiration 

 the suction is released, and the automatic pipette is filled to the 

 mark* with Ba(0H)2 solution. Should the solution overrun the 

 mark on the pipette stem, on releasing the air pressure by opening 

 pinch-cock, /, the solution will run back in the bottle by opening 

 pinch-cock,^, and the proper level may be reached in the pipette. 

 The three-way cock of the automatic pipette is then turned over, 

 and the Ba(0H)2 solution allowed to flow into the tower. The 

 last drop is removed by blowing twice through the mouth-piece, 

 J . It was found that when blown uniformly, the pipette would 

 dehver with a maximum variation of 0.01 cc. Since 1 cc. of | 

 Ba(0H)2 is equivalent to about 6 mgm. of CO2, 25 cc, will absorb 



