• 1819.] Dr. Henry's Experiments on the Gas from Coal. 339 



admixture with any atmospherical air, that might accidentally 

 remain in the gasometer. Wishing to examine the gas in a 

 perfectly recent case, and finding it impossible to make the 

 necessary experiments with sufficient accuracy in a shorter 

 interval, I was obliged to be satisfied with procuring it every 

 other hour. In this place, I shall only state the general results, 

 and I shall describe, in a subsequent part of the paper, the 

 methods of analysis, in cider that other persons who may 

 chocse to compare my experiments with their own may conduct 

 them under equal circumstances. 



By the expression impure gas is to be understood the gas 

 precisely in the state in which it was collected from the retort ; 

 and by purified gas, the same product after being freed from 

 carbonic acid and sulphuretted hydrogen by solution of pure 

 potash, applied in very small quantity, relatively to the volume of 

 the gas, and with the least agitation adequate to the effect. 



Table I. 



Shoiuiug the Quality of Gas from WIQlb . of Cannel , at different 

 Periods of the Distillation. 



Excluding from the calculation the azotic gas, with various 

 proportions of which the products were contaminated, the follow- 

 ing table shows the quantity of oxygen gas consumed, and of 

 carbonic acid produced, by the really combustible part of the 

 gas. 



Table II. 



Showing the Quality of the really combustible Part <f the Gas at 

 different Periods of Distillation. 



Take oxygen. Give carl), acid. 



-100 measures of half hour's s:as 225 118 



1 

 3 



6 



7 

 9 



m 



12 



hour's gas 220 



210 



206 



200 



176 



150 



103 



y2 



117 

 114 

 108 

 98 

 83 

 70 

 45 



