﻿Dynamical Ideas in Chemistry. 4G3 



compound" (p. 424); and he proposes to revert to this usage, 

 confining the word acid to what Gerhardt called " anhydrides." 

 Certain bodies which resemble hydric, ferrous, and ferric chlo- 

 rides are termed " normal salts" and " acid in their properties.'" 

 Dr. Williamson also remarks that "chemists might just as well 

 limit the word acid to the salts of lead, calling the acids them- 

 selves " anplumbates," as say with Gerhardt, that hydrogen - 

 salts are the only acids, and that the real acids are not acids, but 

 only anhydrides ; " and he adds that ' ' the hydrogen-salts can- 

 not with any consistency be called acids." Professor Foster* 

 defends the common application of the word " acid." He shows 

 that, for some little time prior to the definition of Gerhardt, the 

 term included both hydric salts and hydrides ; but that, as a 

 matter of fact, " in perhaps ninety-nine cases out of a hundred, 

 when an acid was spoken of as taking part in, or resulting from, 

 a reaction, it was a hydrogen-salt, and not an anhydrous acid, 

 that was meant." On the whole, however, he is disposed to 

 think that the word "indicates a distinction to which we now 

 know that no real difference corresponds," and advocates term- 

 ing acids "hydric salts," and the anhydrides, what they really 

 are, merely "oxides." 



Alkali originally signified crude potash. Van Helmont, 

 Sylvius, Lemery, and Boerhaave applied it in a general sense to 

 bodies which effervesce with acids; but Boyle recognized as 

 alkalies certain substances which do not act in that manner. 

 The iatro-chemists noticed that they neutralize the effects of 

 acids. Kunkel limited the name to what also might, as he be- 

 lieved, be transformed into acids ; ready union with acids was 

 the characteristic advocated by Stahl. When alkalies came to 

 be divided into caustic and effervescent, it was assumed that 

 the action of lime in transforming the latter into the former 

 kind consisted in a transference of one of its own constituents 

 to the effervescent alkali. This constituent was supposed by 

 Lemery and others to consist of igneous particles ; Kunkel as- 

 signed to it both weight and acid properties. Stahl supposed 

 that alkalies contain a minimum of the primitive acid, of which 

 common acids and neutral and alkaline salts are also partakers. 

 Black, by an admirable series of inductive experiments carried 

 out quantitatively, showed that fixed air is the cause of loss or 

 diminution of causticity. Meyer controverted this conclusion ; 

 and a train of reasoning, which we may still admire for its sub- 

 tlety and system, led him to refer causticity to the acidumpingue 

 — an igneous matter of acid nature. So ably did Meyer support 

 this theory, that two of the most eminent contemporary che- 

 mists gave it special refutation. 



* Phil. Mag. S. 4. vol. xxi. p. 262. 



