312 PKOCEEDINGS OF THE AMERICAN ACADEMY 



tralize a certain quantity of baryta water, before and after the action 

 of the air, represents the carbonate of barium formed, and from this 

 quantity the carbonic acid present in the air is estimated. 



The baryta water used in this process was prepared by dissolving 7 

 grms. of hydrate of baryta in one litre of water. The precise strength 

 of this solution, as determined in the manner described below, was such 

 that 1 c. c. of the solution corresponded to 1,087 mgrm. of C0 2 . This 

 solution was kept in a glass bottle, to the rubber stopper of which was 

 fitted a tube containing soda-lime, and another tube just large enough 

 to allow the passage of a pipette for drawing the baryta water. 



In order to guard against the action of carbonic acid on the baryta 

 water contained in the pipette from the mouth of the person using it, a 

 tube filled with caustic potash was attached to its larger end. The 

 soda-lime apparatus, noticed above, acted in the same capacity as the 

 potash tube toward the carbonic acid in the air of the room. 



The solution of oxalic acid was prepared as follows : — A saturated 

 solution of pure oxalic acid in water was made and allowed to crystal- 

 lize. These crystals were dried between folds of blotting-paper, and 

 for one half-hour over concentrated sulphuric acid. 2.8636 grms. 

 were then weighed out, dissolved in water, and the solution diluted to 

 one litre. 1 c. c. of this solution corresponds to 1 mgrm. of C0 2 . 



The strength of the baryta water was determined as follows : — 

 25 c. c. of the baryta solution were transferred to a small flask, and 

 the oxalic-acid solution run in from a Mohr's burette, until a drop of 

 the mixture failed to give the alkaline reaction (a brown ring on deli- 

 cate turmeric paper). 



Repeated trials showed that 23 c. c. of the oxalic-acid solution were 

 required to exactly neutralize 25 c. c. of the baryta water. 



Three large glass bottles, with tightly fitting glass stoppers, were 

 used for holding the air, in which the carbonic acid was to be deter- 

 mined. The capacity of each was obtained by filling with water and 

 then measuring the same, by means of a flask holding 1,000 c. c. and 

 a cylinder, graduated to single c. c. In this manner the capacity of 

 bottle No. 1. reduced to 0° C, and 760 m. m. bar. press, was found to 

 be 5824.10 c. c, that of No. 2, 6166,11 c. c, and of No. 3, 6240.57 c. c, 

 an allowance of 50 c. c. being made in the calculation for the baryta 

 water used in the process. Previous to each experiment the bottles 

 were thoroughly cleansed and then dried by passing a current of heated 

 air through them. 



