1820.] Dr. Henry's Experiments on the Gas from Coal. 33 



is five pounds of fresh burnt lime to 200 cubic feet of gas. The 

 iime, after the addition of the quantity of water necessaiy to 

 reduce it into powder, is passed through a sieve, and then mixed 

 with a cubic foot (about 7i wine gallons) of water. This is 

 found to be enough to purify the gas sufficiently for ordinary 

 purposes ; but it still retains a minute proportion of sulphuretted 

 hydrogen, which, from the shade of colour produced in the 

 test, may be estimated at about -j-wro*'^ of i*^ volume. For 

 some purposes, the same gas is therefore washed a second time 

 with a similar proportion of fresh lime, which, without being 

 removed from the cistern, is again employed to give the first 

 washing to another quantity of fresh gas. After the second 

 purification, the gas produces no change whatever in the test, 

 which preserves its perfect whiteness, thereby demonstrating the 

 complete removal of the sulphuretted hydrogen. In this state 

 of purity, its odour also is so much diminished as scarcely to be 

 at all oflensive. 



In order to ascertain whether any, and what portion of defiant 

 or carburetted hydrogen gas is lost by the action of the lime 

 liquor, I compared, with the greatest care, the products of the 

 combustion of the recently prepared gas, and of the same gas 

 after one and two washings with lime and water. 



Consumed oxygen. Gave carb. acid, 



100 measures of the unwashed gas . . 190 108 



Gas once washed 175 100 



Twice v/ashed 175 100 



The frequent repetition of similar experiments fully satisfied 

 me that the fresh prepared gas from coal does in fact sustain, by 

 agitation with lime liquor, a loss of combustible matter amount- 

 ing to about 8 or 10 per cent. ; but that the secorid washing is 

 not attended with any further appreciable loss. I found also that 

 the recent gas, by being kept a fortnight in bottles completely 

 filled with it, and well stopped, so as to exclude all agency of 

 the water in which they were inverted, was diminished in com- 

 bustible matter about half the foregoing amount. On the other 

 hand, gas which had been washed with lime liquor suffered no 

 change, when kept under like circumstances for an equal time. 

 It is probable, therefore, that what is separated from the 

 unwashed gas, whether by keeping or by the action of lime 

 liquor, is chiefly condensable matter, partly perhaps an etherial 

 oil, and partly a substance which it is desirable to remove, rather 

 than to allow it to be deposited in a solid form, in the small 

 pipes, or in the burners. 



The little effect of the lime liquor on the olefiant gas, which 

 I had not anticipated, admits, however, of being satisfactorily 

 explained on known principles. Water and similar fluids absorb, 

 according to Dalton, about one-eighth, according to Saussure, 

 about one-seventh, of their volume of olefiaut gas. The utmost 

 Vol. XV. N° I. C 



