64 System of Chemistry, by Prof. Berzelius. 



On the other hand, if, instead of qualities, we resort to composi- 

 laon as the criterion of a salt ; if, as in some of the most respectable 

 chemical treatises, we assume that the word salt is to be employed 

 only to designate compounds consisting of a base united with an acid, 

 we exclude from the class chloride of sodium, and all other " haloid 

 salts," and thus overset the basis of the distinction between "halogene'* 

 and " amphigene'^ elements. 



Moreover, while thus excluding from the class of salts, substances 

 which the mass of mankind will still consider as belonging to it, we 

 assemble under one name combinations opposite in their properties, 

 and destitute of the qualities usually deemed indispensable to the 

 <class. Thus under the definition that every compound of an acid 

 •and a base, is a salt, we must attach this name to marble, gypsum, 

 felspar, glass, and porcelain, in common with Epsom salt, Glauber's 

 salt, vitriolated tartar, pearlash, fee. But admitting that these objec- 

 tions are not sufficient to demonstrate the absurdity of defining a salt, 

 as a compound of an acid and a base, of what use could such a defi- 

 nition be, when, as I have premised, it is quite uncertain what is an 

 acid, or what is a base. To the word acid, different meanings have 

 been attached at different periods. The original characteristic sour- 

 ness, is no longer deemed essential ! Nor is the effect upon vegeta- 

 ble colors treated as an indispensable characteristic. And as res- 

 pects obvious properties, can there be a greater discordancy, than 

 that which exists between sulphuric acid, and rock crystal ; between 

 vinegar, and tannin ; or between the volatile, odoriferous, liquid, pois- 

 on, which we call prussic acid, and the inodorous, inert, concrete, 

 material for candles called margaric acid ? 



While an acid is defined to be a compound capable of forming a 

 salt with a base, a base is defined to be a compound, that will form 

 a salt with an acid. Yet a salt is to be recognised as such, by being 

 a compound of the acid and base, of which, as I have stated, it is 

 made an essential mean of recognition. 



An attempt to reconcile the definitions of acidity given by Berze- 

 lius, with the sense in which he uses the word acid, will in my appre- 

 hension, increase the perplexity. 



It is alleged in his Treatise, p. 1, Vol. II, " that the name of acid 

 is given to silica, and other feeble acids, because they are suscepti- 

 ble of combining with the oxides of the electropositive metals, that is 

 to say, with salifiable bases, and thus to produce salts, which is pre- 

 cisely the principal character of acids J^ Again, Vol. I, p. 308, speak- 



