HYDROGEN, 201 



SEC. III. HYDROGEN WATER HAREMS BLOWPIPE. 



HYDROGEN. 



The name is derived from u^wp and ysvvaw, or ysivofwu, signifying 

 the generator of water ; the popular name is inflammable air ; the 

 miners call it wild fire. 



1. DISCOVERY. 



It was probably known to the ancients, but Mr. Cavendish, A. D. 

 1766, first proved it to be a distinct gas,* as Dr. Black had done 

 nine years earlier with respect to carbonic acid gas, which was the 

 first aeriform body, other than common air, whose existence was 

 established, and hydrogen was the second. f 



2. PROCESS. 



It is always obtained, directly or indirectly, from the decomposi- 

 tion of water. 



(a.) Fragments of zinc, or iron filings, or turnings, 1 part, sul- 

 phuric acid 2 parts, water 5 or 6 parts ; add the water to the metal ; 

 then the acid by separate portions, with intermediate agitation, the 

 vessel being held under a chimney, till the effervescence comes on, 

 when the gas must be received over water, in inverted vessels filled 

 with that fluid. A glass retort, or a glass flask, furnished with a bent 

 tube is all the apparatus that we need. A vessel of lead, or even of 

 plate tin, will answer very well, but its opacity is an inconvenience. 

 Muriatic answers nearly as well as sulphuric in obtaining this gas, but 

 the latter is much cheaper. 



(6.) It is obtained still purer, by the decomposition of water, by 

 iron ; see water. 



(c.) A purer gas. Hydrogen gas as obtained by the above pro- 

 cesses, is not quite pure ; if washed with a little lime water, or caustic 

 potash, it is deprived of carbonic acid, and of sulphuretted hydrogen, 

 which sometimes arises from sulphur in the zinc, and by being 

 passed through alcohol, it loses its odor, which is probably owing to 

 a volatile oil,{ supposed to be generated between the carbon in the 

 metal and the hydrogen. A little carburetted hydrogen is very apt 

 to remain ; and to have the gas absolutely pure, the zinc must be pre- 



* Phil. Trans, v. 66. p. 144. 



t Carbonic acid gas was discovered in 1756 or 7; hydrogen in 1766 ; nitrogen 

 in 1772 ; oxygen and chlorine in 1774. These important discoveries laid the found- 

 ation of the pneumatic chemistry. 



t Which, on diluting the alcohol, makes its appearance, after a few days, upon 

 the surface of the water. Other authors suggest that arsenical particles derived 

 from the zinc, cause the smell. 



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