112 Composition of the Atmosphere 



dition for use; this would result in delay, with always a possibility that 

 the expansion might fracture the glass vessel. Furthermore, as the slightly 

 more dilute solution ultimately used for the routine analyses was so much 

 stronger than the solution recommended by Hempel, it was thought that 

 the coefficient of absorption rather than the completeness of absorption 

 would be sacrificed by employing a less concentrated solution. 1 In the 

 supplementary study made of the comparative value of the various potas- 

 sium pyrogallate solutions, the formulas recommended by both Haldane 

 and Hempel were tested as to their absorptive powers. In all, four dif- 

 ferent solutions were used: 



(1) Hempel's solution, prepared according to his formula. Five grams 

 of pyrogallol were dissolved in 15 c. c. of water and mixed with 120 

 grams of potassium hydroxide dissolved in 80 c. c. of water. Stick potas- 

 sium hydroxide not purified by alcohol was used in all the solutions. 



(2) Hempel's solution, prepared by a modified formula. Inasmuch as 

 stick potassium hydroxide contains from 5 to 25 per cent of water, instead 

 of using 120 grams of stick potassium hydroxide as in the first solution, 

 only sufficient was used to be equivalent to 120 grams of anhydrous 

 potassium hydroxide. To maintain the proper proportion of water, the 

 amount in the stick caustic potash was included in the 80 grams required 

 by Hempel's formula. As the particular lot of stick caustic potash in use 

 at that time was found by alkalimetry to contain 92 per cent of potassium 

 hydroxide, 130 grams of this chemical was mixed with 70 c. c. of water and 

 subsequently the 5 grams of pyrogallic acid added. 



(3) The potassium pyrogallate solution used throughout this research. 

 This is described on p. 80. 



(4) Haldane's formula, requiring a saturated solution of potassium 

 hydroxide in water, with a specific gravity of 1.55. The solution is made 

 in the proportion of 1 gram of pyrogallic acid to 10 c. c. of the potassium- 

 hydroxide solution and hence has the greatest density of all the solutions. 



For purposes of comparison, both outdoor air and cylinder air were 

 analyzed in this study, exactly the same routine being followed in all 

 analyses, and with all four solutions. (See p. 100.) The results are in- 

 corporated in table 71. 



The results of these two series of analyses point conclusively to 

 marked differences in the results obtained with solutions of varying 

 strength. These differences may be attributed either to an incomplete- 

 ness of absorption or to the formation of carbon monoxide. That in- 

 completeness of absorption by the weaker solutions can account in any 

 measure for the differences here observed seems hardly probable when the 

 analyses for January 26, 1912, are considered. The results obtained 

 on that date show that extending the time during which the air was in 

 contact with the reagent for an additional 12 minutes made barely an 



1 For a criticism of the use of potassium pyrogallate as an absorbent of oxygen, see 

 B. Tacke, Archiv fur die gesammte Physiologie, 1886, 38, p. 401. 



