of Types in Chemistry. 1 7 



number of compounds, is one of the most beautiful conceptions 

 of modern chemistry * ; " and again, he declares the idea of 

 regarding both water and ammonia as representatives of the 

 hydrogen type, more or less condensed, to be so simple and so 

 general in its application, that it is worthy " to form the basis of 

 a system of chemistry f." 



We have in this theory two important conceptions : the first 

 is that of hydrogen and water regarded as types to which both 

 mineral and organic compounds may be referred; and the 

 second is the notion of condensed and derived types, according 

 to which we not only assume two or three molecules of hydrogen 

 or water as typical forms, but even look on water as the deriva- 

 tive of hydrogen, which is itself the primal type. 



As to the history of these ideas, Wurtz remarks that the pro- 

 position enunciated by Kolbe, that all organic bodies are derived 

 by substitution from mineral compounds, is not new, but has been 

 known in the science for about ten years. " Williamson was the 

 first who said that alcohol, ether, and acetic acid were comparable 

 to water— organic waters. Hofmann and myself had already com- 

 pared the compound ammonias to ammonia itself. ***** 

 To Gerhardt belongs the merit of generalizing these ideas, of 

 developing them, and supporting them with his beautiful dis- 

 covery of anhydrous monobasic acids. Although he did not 

 introduce into the science the idea of types, which belongs to 

 M. Dumas, he gave it a new form, which is expressed and essen- 

 tially reproduced by the proposition of Kolbe. Gerhardt re- 

 duced all organic bodies to four types — hydrogen, hydrochloric 

 acid, water, and ammonia J." 



The historical inaccuracies of the above quotation are the 

 more surprising, since in March 1854 I published in the Ame- 

 rican Journal of Science (vol. xvii. p. 194) a concise account of 

 the progress of these views. This paper was republished in the 

 f Chemical Gazette ' (1854, p. 181), and copies of it were by 

 myself placed in the hands of most of the distinguished chemists 

 of England, France, and Germany. In this paper I have shown 

 that the germ of the idea of mineral types is to be found in an 

 essay of Auguste Laurent §, where he showed that alcohol may 

 be looked upon as water (H 2 2 ) in which ethyle replaces one 

 atom of hydrogen, and hyclric ether as the result of a complete 

 substitution of the hydrogen by a second atom of ethyle. Hence 

 he observed that while ether is neutral, alcohol is monobasic and 

 the type of the monobasic vinic acids, as water is the type of 



* Repertoire de Ckimie Pure, 1860, p. 359. f Ibid. p. 356. 



X Ibid. p. 355. 



§ "Sur les Couibinaisons Azotees," Ann. de Chim. et de Phys. Novem- 

 ber 1846. 



Phil. Mag. S. 4. Vol. 22. No. 144. July 1861. C 



