Existence of Compound Radicals in Amphide Salts. 59 



then the whole nature of the body changes, it is insoluble in wa- 

 ter, and even in the strongest alkaline solutions, and can only be 

 brought back to its former state by being fused with potash at a 

 red heat. Here it is evident that the acid properties and the wa- 

 ter go together; and we may conclude, that in order to manifest 

 strong acid properties, the acid must be in its hydrated form. 

 But in that hydrated form, if the water acted as a base simply, 

 the tendency of the acid to combine with other bases should be 

 inferior to that of the dry acid ; for if we place oil of vitriol and 

 barytes together, the water must be first expelled before the ba- 

 rytes and sulphuric acid can unite, and hence an impediment 

 would exist to their union which should not occur with cold ba- 

 rytes and dry sulphuric acid in vapor, and yet cold barytes and 

 oil of vitriol will combine with such intensity as to produce ig- 

 nition, whilst the barytes must be heated before it begins to 

 combine with the dry sulphuric acid. The water, therefore, is 

 essential to the manifestation of strong acid properties, and it does 

 not exist in combination with the acid merely as a base. What, 

 then, is the constitution of a hydrated oxygen acid? 



"When muriatic acid (HC1) acts on zinc, the metal is taken 

 up, forming ZnCl, and hydrogen is expelled, and if, in place of 

 zinc, oxide of zinc be taken, the effect is the same, except that 

 the hydrogen combining with the oxygen of the oxide forms 

 water; HC1 and ZnO giving ZnCl and HO. Now we have in 

 oil of vitriol the elements SO"H combined together ; when put 

 in contact with zinc, H is expelled, and S0 4 Zn is formed, and 

 with ZnO and S0 4 H, there are produced S0 4 Zn, and HO is 

 set free. In both cases, of which the former may be taken as 

 the type of all the haloid salts, and the latter of all salts formed 

 by oxygen acids, there is H as the element which is removable 

 by a metal, precisely as one metal is replaceable by another, as 

 indeed from the real metallic character of hydrogen may be con- 

 sidered to occur in this case. Every acid may, therefore, be 

 considered to consist of hydrogen combined with an electro- 

 negative element, which may be simple, as chlorine, iodine, flu- 

 orine ; or may be compound, as cyanogen, NC 2 , and yet capable 

 of being isolated ; or as occurs in the great majority of cases, its 

 elements may be such as can only remain together when in com- 

 bination. Thus oil of vitriol does not contain SO 3 and HO, but 

 consists of hydrogen united to a compound radical SO 4 . Liquid 



