138 Experiments relative to the Impurities of 



But, Mr. Tilloch, I am wandering from your proper depart- 

 ment, and from what Mr. Farey is pleased to call my oivn pro- 

 per pursuit. I must return to it. And as he requests me "^ to give 

 an attentive reading, and consideration, to his paper on the 

 Strata of Antrimy in your xxxixth volume, and that I will, ere 

 long, furnish you, at some length, with my candid and free re- 

 marks on this paper, compiled chiefly from my own writings:" — 



I reply, that I shall be happy to do so, so soon as you or lie 

 can furnish me with the paper referred to, which in my remote 

 and retired situation has not reached me. 



Moy, Ireland, June 1816. W. RiCHARDSON. 



XXXVI. Experiments relating to the Impurities of Hydrogen 

 as it is commonly obtained. By M. Donovan, Esq. 



Read to the Kirwanian Society ofDulliny May 15. 



J. HE process employed for obtaining hydrogen is the decom- 

 position of water by means of a metal. For this purpose zinc 

 and iron are commonly used, with dilute muriatic or sulphuric 

 acid*. But the gas thus produced is variable in some of its 

 properties : its odour, and the colour of its flame, are not al- 

 ways the same : it therefore contains foreign matter. 



Experiments which required very pure hydrogen compelled 

 me to pay some attention to its common impurities, and to the 

 best means of removing them. 



A very small Woulfe's apparatus was arranged, the first bottle 

 containing caustic ammonia, the second lime-water, and the 

 third common water. A long continued stream of hydrogen 

 was passed through this series, from the vessel in which it was 

 generating ; and the pressure of several inches of water was ap- 

 plied. By this process, the ammonia acquired a fetid smell. 

 When mixed with muriatic acid, it exhaled the odour of sulphu- 

 retted hydrogen ; and paper moistened in acetate of lead was 

 blackened, when held over the fluid. The Hme-water contained 

 carbonate of lime ; and when the clear fluid was poured off, 

 and mixed with muriatic acid, a minute quantity of white pow- 

 der was deposited, which when separated burned blue like sul-. 

 phur. The smell of the hydrogen obtained was, by these means, 

 altered: it had now an odour precisely like phosphorus. It 

 burned with a fine green flame ; whereas before it burned blue. 



* The gun-barrel process is so very troublesome and difficult to manage^ 

 that, I believe, it is seldom resorted to. It affords, however, a very pure 

 hydrogen. 



Wishing 



