ON THE THEORY OF TYPES IN CHEMISTRY. 123 
assume two or three molecules of hydrogen or water as typical 
forms, but even look on water as the derivative of hydrogen, which 
is itself the primal type. 
As to the history of these ideas, Wurtz remarks that the propo- 
sition enunciated by Kolbe that all organic bodies are derived by 
substitution from mineral compounds is not new, but 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. Hoffman and myself had already compared the compound 
ammonias to ammonia itself’? * * * «To Gerhardt belongs 
the merit of generalizing these ideas, of developing them, and sup- 
porting them with his beautiful discovery 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 essentially reproduced by the proposition of Kolbe. 
Gerhardt reduced all organic bodies to four types—hydrogen, hydro- 
ehloriec acid, water and ammonia.—(Jéid, p. 355.) 
The historical inaccuracies of the above quotation are the more 
surprising since in March, 1854, I published in the American Journal 
of Science, (xvii. 194) a concise account of the progress of these 
views. This paper was re-published in the 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, (Sur Tes Ooim- 
binaisons Azotées, Ann. de Chimie et Physique, Nov., 1860,) where 
he showed that alcohol may be looked upon as water (H,O,) in 
which ethyle replaces one atom of hydrogen, and hydric 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 bibasic acids. In extending and developing this idea of 
Laurent’s, I insisted in March, 1848, and again in January, 1850, 
upon the relation between the alcohols and water as one of homology, 
water being the first term in the series, and H, being in like manner 
the homologue of acetene and formene, while the bases of Wurtz 
were said to “sustain to their corresponding alcohols the same 
relation that ammonia does to water.” (Am. Jour. Sci. v. 265; 
ix. 65; xiii. 206.) f 
