35 



above-mentioned experiments evince the contrary. Ou another occa- 

 sion I determined the illuminating power of some gas, and then, 

 without alteration of the quantity passing, sent the gas through a 

 U-tube containing naphthalin from the London gas-mains. The cha- 

 racter of the flame was changed from white to red, but the photo- 

 meter indicated no difference in the light given. Two other persons 

 conversant with photometry were present at this experiment and 

 agreed in the result, though up to that time they had held the pre- 

 vailing opinion as to the value of naphthalin in gas without testing 

 the statements made upon the subject. 



Another sulphur compound is said always to be present in coal- 

 gas and to be irremoveable, and which, like those I have hitherto 

 spoken of, does not affect lead-paper, viz. bisulphide of carbon. To 

 ascertain the presence of bisulphide of carbon, I pass gas through 

 strong spirit of wine (methylated spirit answers perfectly) kept at 

 about 160 Fahr. The gas and vapours pass out of the flask which 

 contains the spirit up a long tube into an inverted flask, so that all 

 which is condensed may run back into the spirit. It then passes 

 into another flask for additional condensation, and thence forward to 

 a gas-holder or burner. Bisulphide of carbon dissolved in spirit 

 becomes precipitated as a white cloud which settles to the bottom 

 of the vessel, when the spirit is copiously diluted with water. The 

 white cloudy precipitate escapes slowly by single bubbles through 

 the diluted spirit, and at length leaves a solution perfectly clear. 

 The spirit through which gas has passed, and from which it has 

 abstracted bisulphide of carbon, acts in precisely the same manner 

 upon dilution, and no one who has seen the reaction once or twice 

 can possibly mistake it. The study of other compounds led me to 

 conclude that if this substance exist as such, and not merely ly its 

 elements, in gas, it could be removed almost as easily as the naph- 

 thalin compound could be purified, and that the same process could 

 be made available to remove the sulphur of both. I thought that 

 under certain conditions the affinity of hydrogen for sulphur would 

 exceed that of carbon for sulphur, and therefore that I might obtain 

 the sulphur of bisulphide of carbon as a sulphide of hydrogen, about 

 the removal of which there is no difficulty. Experiment confirms 

 the reasoning. When hydrogen mixed with vapour of bisulphide of 

 carbon is passed through a tube filled with slaked lime or clay 



