Prof. Williamson on Chemical Nomenclature. 467 



to salts with hydrogen as base. And coupled, as it is, with Mr. 

 Foster's admission that these hydrogen-salts ought, in systematic 

 language, to be called hydric sulphate, hydric nitrate, &c, it 

 does convey Mr. Foster's assent in a very full manner to the 

 principle of the proposal which I made on the subject of Nomen- 

 clature. 



The general form of Mr. Foster's paper is, however, that of 

 an argument against my proposal ; and the paper contains some 

 statements to which my silence would probably seem to give a 

 consent, which I really cannot give. It must have been from 

 inadvertence that Mr. Foster speaks of my wishing to apply the 

 name acid to such bodies as CO 2 , SO 3 , SiO 2 , &c. ; for I merely 

 remarked that the name that belongs to them is wanted by its 

 owners, and that it does not suit the hydrogen-salts to which 

 Gerhardt wanted to transfer it. 



Mr. Foster goes into an elaborate exposition of what he con- 

 ceives to be the original meaning of the word acid, and speaks of 

 that " original meaning " as " anything but particularly clear." 

 He might safely have called it " particularly cloudy." 



Every chemist knows that the great Berzelius epitomized the 

 prevailing definition by saying that an acid is an electro-negative 

 oxide, and a base is an electro-positive oxide. No definition is 

 complete and perfect ; but^this definition is certainly clear, and 

 it does point to differences of properties among chemical com- 

 pounds which are the most characteristic and important known 

 to us. I cannot see any chance whatever of the words acid and 

 base being given up; for they describe conveniently the chief 

 differences of properties by which we classify compounds chemi- 

 cally. Mr. Foster's remark, that " the strictly scientific signifi- 

 cance of the word acid has passed away," and that the word indi- 

 cates "a distinction to which we now know that no real difference 

 corresponds," must be taken as referring to Gerhardt' s misuse of 

 the word acid, as describing salts with basic hydrogen. He 

 might have gone a step further in condemnation of that misuse 

 of the word, and have shown that the word acid never has had 

 any scientific significance as applied to hydrogen-salts. 



Mr. Foster quotes from my note (but apparently misunder- 

 stands) the statement, "In fact he [Gerhardt] systematically 

 applied the term acid to hydrogen-salts, giving the name anhy- 

 dride to acids, and leaving bases, however anhydrous they might 

 be, entirely unprovided with a corresponding name." If bodies 

 such as HNO 3 , H 2 SO 4 , H 3 PO 4 were considered to be entitled to 

 the name "acid," then for precisely similar reasons, bodies such as 

 KOH, Ba (OH) 2 would be entitled to the name "base"; and if the 

 bodies N 2 5 , SO 3 , P 2 5 , &c. formed by dehydrating these so- 

 called acids are called "anhydrides," then some corresponding and 



