T. 8. Hunt on the Theory of Types in Chemis'ry. 259 
As to the history of these ideas, Wurtz remarks that the prop- 
osition enunciated by Kolbe that ‘all organic bodies are derived 
from mineral compounds, from which they take their origin, in 
part directly, by processes of substitution of great simplicity,” 
is not new, but “known in the science for about ten years. 
Williamson was the first who said ‘alcohol, ether and acetic 
acid are compounds comparable to water, organic waters.’ Hof- 
mann and myself had already compared the compound ammo- 
nias to ammonia itself. * * * To Gerhardt belongs the merit of 
generalizing these ideas, of developing them, and supporting 
em with his beautiful discovery of anhydrous organic mono- 
_ basic acids. Although he did not introduce into the science 
the idea of types, which belongs to Dumas, he gave it a new 
form, which is expressed and essentially reproduced by the prop- 
osition of Kolbe.” ‘‘ Gerhardt reduced all organic bodies to four 
types, hydrogen, hydrochloric acid, water and ammonia.” (Reper- 
tc., p. 355 
toire, etc., . 
this idea of mineral types is to be found in an essay by Auguste 
Laurent, (Sur les combinaisons azoteés, Ann. de Chimie et de Phys- 
ique, Nov. 1846,) where he showed that alcohol may be looked 
the type of the monobasic vinie acids, as water is the type of 
dibasic acids. In extending and developing this idea of Laurent's 
insisted in March, 1848, and again in January, 1850, upon the 
telations between the alcohols and water as one of homology, 
Water being the first term in the series, and H, in like manner 
the homologue of formene and acetene, while the bases of Wurtz 
Were said to sustain to their corresponding alcohols the same 
Pathe that ammonia does to water. (This Journal, v, 265, 1x, 
Tn We tides ‘of his‘ cmtay published: in September, 1848, (Ibid, 
¥i,178,) T endeavored to show that Laurent’s ener 
extended so as to include in the type of wee, : 
