xii THE HALOGENS 249 



A very clear statement was made by Auguste Laurent 

 (1807 1853), who regarded all acids as salts of hydrogen, 

 strictly analogous with the salts of silver or zinc, but 

 differing from them in taste and volatility. 



After considering the general resemblance between the 

 compounds of zinc and those of an element X, which turns 

 out to be hydrogen, he writes : 



" If hydrogen had been a comparatively fixed body, and 

 its oxide fixed and solid, no one would have thought of 

 excluding it from the metals. . . . 



" Dumas has even gone so far as to conceive, that if we 

 could but condense hydrogen, it would present a metallic 

 aspect. 1 . . . 



" For my part I do not see any difference between acids 

 (meaning thereby the salts of hydrogen) and ordinary salts ; 

 neither do I recognise any difference between these two 

 kinds of bodies, and the group of oxides in general " 

 (Chemical Method, Cavendish Society Reprints, 1854, 41). 



In Laurent's opinion, there is a profound difference 

 between the acids as salts of hydrogen and the oxides 

 from which many of them are derived by the addition of 

 water. 



" Having thus associated certain compounds, which 

 chemists separate, I proceed now to separate certain other 

 compounds which they associate. The anhydrous and the 

 hydrated acids are always confounded and employed, 

 theoretically at least, the one for the other. Nevertheless, 

 these bodies do not present any analogy ; under no circum- 

 stances whatever, do they comport themselves in the same 

 manner : their functions are entirely different. Take for 

 example the anhydrous sulphuric acid and the sulphate of 

 hydrogen. The first does not combine with metals ; the 

 second does combine with them, at the same time liberating 

 hydrogen. The first unites directly with the metallic oxides ; 



1 Liquid hydrogen, which Dumas described as " hydrogenium " to 

 indicate its metallic character, is not a metal, but resembles the 

 paraffins, to which series it really belongs. 



