292 A. M. GURJAR 



ing the CO2 in the air employed for flushing out the air in the 

 chamber. Pinch-cock, 6, being opened, aspiration is begun at a 

 slow rate, the gases being drawn through the meter, M. The 

 meter readings show the volume of air which has been drawn 

 through the system. With bulk grain ten volumes of the capac- 

 ity of the respiration chamber completely flushes out the CO2 

 in the latter. After about one volume of air has been drawn 

 through the tower the rate of aspiration may be increased. It 

 has required about 45 minutes to complete the aspiration in the 

 studies mentioned. 



The tower is then disconnected at the stopper, E, and elevated 

 from the suction flask sufficiently to permit the beads and Ba(0H)2 

 solution to flow down into the flask. About 50 cc. of COo-free 

 water are run from the separatory funnel, G, down the sides 

 of the tower, while the latter is being revolved in such a manner 

 as to insure thorough washing of its inner wall. The suction 

 flask is disconnected from the respiration chamber, the tower 

 hfted out of the flask, and the residual Ba(0H)2 titrated against 

 a standard HCl solution, using phenolphthalein as an indicator. 

 Checks of the apparatus and method, using C. P. CaCOs have 

 demonstrated their desirability and accuracy for this purpose. 



PREPARING THE CARBON DIOXIDE-FREE WATER 



The stock-bottle for the CO2 free water may be easily filled 

 without removing the stopper by disconnecting the rubber tube 

 to which pinch-cock, 3, is attached, and connecting it to the 

 distilled-water container, opening pinch-cock, 4, and connecting 

 the tube to which it is attached to the aspirator. When suction 

 is applied by means of the latter, water is rapidly drawn into the 

 bottle. The water may be tendered free from carbon dioxide 

 by closing pinch-cock, 3, and opening pinch-cock, 5. Air may 

 thus be passed vigorously through the water, about thirty min- 

 utes of aspiration rendering it sufficiently pure for this purpose. 

 To determine its freedom from CO2, 100 cc. are titrated against 

 ■/o KOH, using phenolphthalein as an indicator. It should not 

 require more than 0.2 cc. of the KOH solution to produce a 

 permanent pink coloration. 



