Experiments on the Gas from Coal. 16.') 



from its known powers of saturatioUj might Iiave been deemed 

 equivalent to the effect. The proportion employed by Mr. Lee 

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

 lime, after the addition of the quantity of water necessary to re- 

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

 with a cul)ic foot (about 71 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 one ten thousandth of its volume. For some 

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

 similar proportion of fresh liuie, 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 pre- 

 •serves its perfect whiteness, thereby demonstrating the complete 

 removal of the sulphuretted hydrogen. In this state of purity, 

 its odour, also, is so nuich diminished as scarcely to be at all of- 

 fensive. 



In order to ascertain whether any, and what portion of de- 

 fiant 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 1/5 100 



Twice washed 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 second washing is 

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

 that the recent gas, by being kept a fortnight in bottles com- 

 pletely 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 whicii 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 un- 

 washed gas, whether by keeping or by the action of lime li<|Uor, 

 is chiefly condensable matter, partly perhaps an ethereal oil and 

 partly a suljstance which it is desirable to lemove, rather than 

 to allow it to lie deposited in a solid form, in the small pipes, or 

 in the burners. 



L 3 The 



