OF ARTS AND SCIENCES. 



221 



the tubes as soon as they were disconnected, and to leave each of them 

 closed in the balance case until it was time to take the weight. The 

 U-shaped tubes with perforated ground stoppers, by which connection 

 with the lateral tubes can be instantly opened or closed, are admirably 

 adapted to this work. As an example, we give next the details of 

 one determination of carbonic acid by the method we have described. 



Details of a Determination of Carbonic Acid. 



The gas was generated from statuary marble and dilute hydro- 

 chloric acid in an apparatus precisely similar to that described and 

 figured by us in a previous paper.* It was first washed by a solution 

 of potassic bicarbonate, and then, having passed in succession over 



Fig. 3. 



calcic chloride, sulphuric acid, and phosphoric anhydride, it was con- 

 ducted into the balloon and overflow in the manner already described. 

 The gas was tested by leading the current from the overflow into a 

 familiar form of nitrogen apparatus filled with a solution of potassic 



♦ These Proceedings, vol. xxiii. p. 166. 



