DETERMINATION OF CARBON DIOXIDE 289 



the gases must be passed through it. It cannot be employed 

 where the time element is significant. The method of Truog^ 

 in which the carbon dioxide is absorbed in a measured quantity 

 of I Ba(0H)2 solution contained in a special absorption tower, 

 and the residual barium hydroxide titrated against a standard 

 HCl solution, seemed best adapted to this purpose. The ad- 

 vantages of this method, together with a discussion of titrimetric 

 methods, are presented by Truog. In assembling the apparatus 

 certain difficulties were encountered, however, and an attempt 

 was made to overcome them. Thus the original form of absorp- 

 tion tower did not provide an adequate means for transferring 

 the standard Ba(0H)2 solution, and C02-free water from the 

 stock bottles to the absorption tower without exposing them to 

 the atmosphere. An automatic pipette was accordingly con- 

 structed which was connected to both the stock bottle and the 

 tower in such a manner that the Ba(0H)2 solution could be trans- 

 ferred and measured through a closed system protected from the 

 laboratory air by soda-lime tubes. A convenient arrangement 

 for rendering the wash- water free from CO2 without disconnecting 

 the reservoir w^as also assembled. These additions rendered the 

 apparatus more efficient for plant respiration studies, and they are 

 described in detail in this paper. 



DESCRIPTION OF THE APPARATUS 



The complete apparatus is illustrated in the accompanjdng 

 figure. The absorption flask and tower tube are similar to those 

 employed by Truog, except that the tube is provided mth an 

 adapter, D, at the top. This adapter has a belled top, which not 

 only affords a tight connection with the rubber stopper, E, but 

 can be readily separated from the stopper in disconnecting the 

 several parts of the apparatus. This adapter is connected to 

 the tube, C, by means of a packing of pure gum tubing. The 

 stopper, E, has two holes, one of which admits the tip of the 

 automatic pipette, H, and the other the lower tube ol the U-tube, 



^ Truog, E. Method for the determination of carbon dioxide and a new form of 

 absorption tower adapted to the titrimetric method. Jour. Ind. and Engin. 

 Chem. 7: 1045-1049. 1915. 



