XX.] THEORY OF TYPES IN CHEMISTRY. 463 



types is to be found in an essay of Auguste Laurent (Sur les 

 Combinaisons Azote*es, Ann. de Chiniie et Physique, Novem- 

 ber, 1846), where he showed that alcohol may be looked upon 

 as water (H 2 2 ) 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 2 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. 

 Journal of Science, V. 265 ; IX. 65 ; XIII. 206.) 



In a notice of his essay, published in September, 1848 

 (Ibid., VI. 173), I endeavored to show that Laurent's view 

 might be further extended, so as to include in the type of 

 water " all those saline combinations (acids) which contain oxy- 

 gen " ; and in a paper read before the American Association for 

 the Advancement of Science at Philadelphia, in September, 

 1848, I further suggested that as many neutral oxygenized 

 compounds which do not possess a saline character are deriva- 

 tives of acids which are referable to the type H 2 2 , " we may 

 regard all oxygenized bodies as belonging to this type" which I 

 further showed in the same essay to be but a derivative of the 

 primal type H 2 . To this I referred all hydrocarbons and their 

 chlorinized derivatives, as also the volatile alkaloids, which 

 were regarded as " amidized species " of the hydrocarbons, in 

 which the residue amidogen, NH 2 , replaces an atom of H or 

 Cl, or, what is equivalent, the residue NH is substituted for 

 2 in the corresponding alcohols. (Ibid., VIII. 92.) 



In the paper published in September, 1848, I showed that 

 while water is bibasic, the acids which like hypochlorous and 

 nitric acids were derived from it by a simple substitution of Cl 

 and N0 4 for H, were necessarily monobasic, and I then pointed 



