Chemical Absorption of Gases. 



359 



Here it is at once seen that the rate of absorption in the 

 lighter gas (hydrogen) is greater than when the carbonic 

 dioxide is diffused through air ; also that the hypothesis as to 

 the relation between the rate and the pressure of the gas does 

 not hold. This latter point, however, is more marked in some 

 of the other experiments that follow. Although the mano- 

 meter continued to rise very slowly a few millimetres after 

 the sixtieth minute, it is not considered necessary to record 

 the observations beyond this limit. 



Sulphuretted Hydrogen. — This gas was prepared both from 

 sulphide of antimony, previously boiled with dilute hydric 

 chloride to decompose any trace of carbonate that might be 

 present, and also from ferrous sulphide; it was found, however, 

 more convenient to employ the latter material. As ferrous 

 sulphide usually contains particles of metallic iron, which give 

 rise to an evolution of hydrogen, the material was finely 

 ground, mixed with sulphur, and ignited, the operation being 

 repeated twdce. The gas obtained from this prepared sulphide 

 gave off only a very small quantity of unabsorbable gas, which 

 could influence the results but slightly. 



The densities of sulphuretted hydrogen and carbonic dioxide 

 are as 17 : 22; and the following results show how much more 

 rapidly the former is absorbed than the heavier gas C0 2 . This 

 is noticeable especially at the start ; the rate, especially in 

 hydrogen, rapidly decreases as the pressure diminishes. 



SH 2 in Air. Barometer, 769*4. 



Time, 

 minutes. 



Manometer- 

 reading, 

 millimetres. 

 n. 



Difference of 

 pressures. 



Ratio. 



n' — n 







] 



2 



3 '.'.'.'.'.'. 



4 



5 



7 



10 



15 

 20 



25 



30 



40 



50 



60 



29 



194-8 

 263-2 

 294-2 

 310-8 

 321-6 

 337-1 

 355-2 

 379-8 

 398-4 

 411 

 420-7 

 431-4 

 438 

 442 



165-8 

 68-4 

 31 

 16-6 

 10-8 

 15-5 

 18-1 

 24-6 

 18-6 

 126 



9-7 

 10-7 



6-6 



4 



•412 

 •453 

 •535 

 •651 



