434 MM. T. GEAHAM ON THE ABSORPTION AND 



The charged cornettes were always freely exposed to air for some time before occluded 

 gas was extracted from them and measured, so as to allow the escape of any loosely 

 attached gas. 



6. The same cornettes were heated and cooled in a stream of dry air, in like manner 

 as they had been treated with other gases. The occluded air given out in one hour 

 amounted in two different experiments to 1*15 and 095 cub. centim. respectively. The 

 gas of the second experiment gave 



0-82 cub. centim. Nitrogen . = 86-3 

 0*08 „ ,, Carbonic acid = 84 

 0"05 „ „ Oxygen . . = 5'3 



0-95 100-0 



The whole occluded air amounts to 0-2 volume of the gold, and is principally nitrogen. 

 The indifference of gold to oxygen is remarkable, and contrasts with the power of silver 

 to occlude the same gas. 



Silver. 



1. Fine silver, in the form of wire, 2 millims. in diameter, with its surface duly puri- 

 fied, was first heated alone in the porcelain tube, and then exhausted of gas by the 

 Sprengel tube in the usual way. The natural gas derived from this metal was small in 

 quantity, and it appeared to come off almost entirely in one hour. The silver wire 

 weighed 108 8 grms., and had a volume of 10-37 cub. centims., taking the specific gravity 

 of pure silver as 10-49. The gas extracted amounted to 



2*2 cub. centims. in thirty minutes. 



Silver wire therefore appeared to hold occluded 0-289 volume of gas, principally 

 carbonic acid. There is reason, however, to suppose that the occluded gas may really 

 be oxygen, and that the latter was converted into carbonic acid at the temperature of 

 extrication, by a trace of carbon existing in the fine silver. 



2. The same quantity of silver wire was now charged with hydrogen, by being heated 

 to redness and afterwards cooled slowly in that gas. The gas extricated amounted to 



2-3 cub. centims. in forty-five minutes. 

 0-2 „ „ in fifteen minutes. 



2-5 „ ,, in one hour. 



