514 Mr Varley, 'On the Absorption of 



Coal Gas. 



The ordinary Cambridge coal gas led directly into the 

 apparatus through calcium chloride drying tubes gave the 

 following figures : 



Mean value of current when vessel filled with air =119*6 

 „ „ ,, „ coal gas = 2O0 



showing that 83 / o of the light had been absorbed by the coal 

 gas. 



In order to test whether some part of this large absorption 

 might not be due to the presence of acetylene in the gas, it was 

 passed through an ammoniacal solution of cuprous oxide in order 

 to remove all the acetylene, then through sulphuric acid to remove 

 the ammonia and dry the gas. 



The results now obtained were as follows : 

 Mean value of current when vessel filled with air= 117"3 

 Mean value of current when vessel filled with coal 

 gas from which the acetylene had been removed = 89 "0 

 showing that now only 24 °/ of the light had been absorbed — an ab- 

 sorption of the same value as that observed for the chief constituents 

 of coal gas, ethylene and marsh gas. In order to afford a further 

 check on the conclusion that the large amount of absorption was due 

 to acetylene, the latter experiment was repeated with the single 

 difference that the cuprous monoxide solution was removed. The 

 absorption was again over 80°/ o . 



Sulphur Dioxide. 



The sulphur dioxide was obtained directly from liquefied 

 sulphur dioxide as supplied commercially in bottles. The 

 absorption was so large when the gas was at atmospheric pressure 

 that it was thought better to measure the intensity of the light 

 after it had passed through the gas at a reduced pressure and 

 from this calculate what the absorption would be at atmospheric 

 pressure. 



Mean value of the current when vessel filled with air = 117 - 5 



„ „ ,, S0 2 at 25 mms. pressure = 52*3 



giving an absorption of 44*5 °/ in passing through 10 cms. of gas 

 at 25 mms. pressure, equivalent to a length of 032 cms. at 

 atmospheric pressure. 



Another experiment gave 



Mean value of the current when vessel filled with air = 79*3 

 „ „ „ S0 2 at 28 mms. pressure = 39'6 



