Hydrogen as it is commonly obtained. 139 



Wishing to try if hydrogen, procured by means of zinc, con- 

 tain sulphur, I repeated the experiment with that metal. Sul- 

 phuretted hydrogen and sulphur were obtained as before ; and 

 the gas gave the same smell and flame as the former. 



By repeating the process, with muriatic acid, it was proved 

 that the sulphur had not been afforded by the sulphuric acid. 

 And trials on different specimens of iron and zinc offered the re- 

 sults already stated. 



Thus common hydrogen contains an admixture of sulphuretted 

 hydrogen which is not absorbed during the passage of the ga't 

 tlirough the water in which it is received ; and thi,s admixture 

 affects both its smell and the colour of its flame. 



From these facts, it appeared that the water resulting from 

 the combustion of common hydrogen should contain sulplauic 

 acid. A large quantity of hydrogen was therefore collected in 

 new dry bladders provided with pipes and stop-cocks, and the 

 combustion was suffered to go on slowly, in a new and perfectly 

 clean globe, kept cool under water. The water produced was 

 tested with muriate of barytes, which caused a precipitation j it 

 also reddened water tinged with violets. 



The experiment was repeated with this difference, that the 

 gas, previously to its reception into the bladders, was suffered to 

 remain over water for twenty-four hours, and was frequently 

 agitated. In this case, the water produced did not afford a pre- 

 cipitate with nuiriate of barytes. 



During the revolution which took place in chemistry towards 

 the end of the last century, there v\-as a controversy concerning 

 the product of hydrogen burnt in ox\gen. The advocates of the 

 new doctrine statetl that the result is water. The opposite party 

 maintained that an acid is the product. Acid was, in some 

 cases, certainly found ; but it was conceived by the framers of 

 the new system to be formed by the combustion of a httle azote, 

 from which it is difficult to free oxygen. In other trials no 

 trace of acid could be detected. The foregoing statements ren- 

 der it proljabie that,wlien acid was produced, it might have been 

 the sulphuric, l)ut so much diluted as to be difficult to recognitje; 

 and when there was no trace of acid, the hydrogen had perhaps 

 lain so long over water that the sulphur was taken up entirely. 



The hydrogen, which had been freed from sulphur and car- 

 bonic acid, had a remarkable smell of phosphorus. This might 

 be really owing to phosphorus, for some kinds of iron have been 

 proved to contain it; or it might be owing to arsenic. Either 

 of these would be acidified by passing the impure hydrogen 

 through nitrous acid, and the gas might be obtained in a state 

 of purity. 



A long continued stream of the gas was therefore passed through 

 • a set ics 



