from the Nature of Coal Gas. 437 



On passing a stream of the gas obtained from Welsh culm 

 through a solution of acetiie of lead with excess of acetous 

 acid, it instantly produced a copious black precipitate, which 

 effervesced strongly with nitric acid, and yielded much sul- 

 phuretted hydrogen gas. 



A quantity of gas which had been repeatedly agitated in 

 contact with a solution of acetite of silver with excess of 

 acid, when suffered to burn under a gardener's bell-glass 

 filled with common air, deposited a dew on the inner sur- 

 face of the bell ; the moisture produced permanently reddened 

 a blue cabbage leaf, and caused a precipitate in acetate of 

 barytes ; the precipitate was insoluble in dilute nitric acid; 

 the gas therefore still contained either sulphureous or sul- 

 phuric acid ; and hence the gas, when intended for the illu- 

 mination of dwellings, should be procured at a bright red 

 heat. The odour of it becomes under this condition di- 

 minished, and the property of blackening paint is but slight 

 and feeble. 



The method recommended to deprive the gas of its odour, 

 by passing it through lime-water, or through lime in a state 

 of ignition, was found to be absolutely insufficient ; continued 

 agitation with lime diffused through water to the consist- 

 ence of cream, with a portion of alkaline ley, was found to 

 deprive the gas of part o£ its strong odour. 



If the gas from coal be suffered to stand over water for 

 some days, or if it be agitaled with that fluid, its property of 

 producing a brilliant white light is much impaired. It then 

 burns with a blueish flame instead of a white pnt^ : hence, 

 for the purpose of illumination, the gas should be used as it 

 issues from the distillatory vessel. 



Whether the sulphuretted hydrogen gas spoken of is an 

 accidental or unavoidable ingredient in the gas of coal, I 

 have not been able to learn. Indeed the whole nature of the 

 gas seems to be but ill understood by chemists themselves. 

 For, notwithstanding the merit which Mr. Henrv's paper 

 in the Philosophical Transactions for 1808, p. II, describing 

 an apparatus for the analysis of the compound inflammable 

 gas, contains, the results of his experiments cannot be ac- 

 curately relied on. The imperfection of the apparatus em- 



£ P 3 ployed 



