of Types in Chemistry. 19 



water in which a bibasic residue replaces an atom of hydrogen. 

 The idea of polymeric types was further illustrated in the same 

 paper, where three hydrogen types were proposed, (HH), (H 2 H 2 ), 

 and (H 3 H 3 ), corresponding to the chlorides MCI, MCI 3 , and 

 MCI 3 . It was also illustrated by sulphur in its ordinary state, 

 which I showed is to be regarded as a triple molecule S 3 (or S 6 =4 

 volumes), and referred sulphurous acid SO 2 to this type, to which 

 also probably belongs selenic oxide. (At the same time I sug- 

 gested that the odorant form of oxygen or ozone was possibly O 3 .) 

 Wurtz, in his memoir published in 1855, adopts my view, and 

 makes sulphur vapour at 400° C. the type of the triple molecule. 

 I further suggested* that gaseous nitrogen is NN, an anhy- 

 dride amide or nitryle, corresponding to nitrite of ammonia, 

 (NO 3 , NH 4 0) - H 4 4 = NN. This view a late writer attributes 

 to Gerhardt, who adopted it from mef. May not nitrogen gas, 

 as I have elsewere suggested, regenerate under certain conditions 

 ammonia and a nitrite, and thus explain not only the frequent 

 formation of ammonia in presence of air and reducing agents, 

 but certain cases of nitrification J ? 



I endeavoured still further to show that hydrogen is to be 

 looked upon as the fundamental type, from which the water type 

 is derived by the replacement of an atom of H by the residue 

 H0 2 § . In the same way I regarded ammonia as water in which 

 the residue NH replaced O 2 . 



I have always protested against the view which regards the 

 so-called rational formulae as expressing in any way the real 

 structure of the bodies which are thus represented. These for- 

 mula? are invented to explain a certain class of reactions, and we 

 may construct, from other points of view, other rational formulae 

 which are equally admissible. As I have elsewhere said, " the 

 various hypotheses of copulates and radicals are based upon the 

 notion of dualism, which has no other foundation than the ob- 

 served order of generation, and can have no place in a theory of 



* American Journal of Science, vol. v. p. 408; vol. vi. p. 172. 



\ Ann. de Chim. et de Phys. vol. lx. p. 381. 



X The formation of a nitrite in the experiments of Cloez appears to be 

 independent of the presence of ammonia, and to require only the elements 

 of air and water (Comptes Rendus, vol. lxi. p. 135). Some experiments now 

 in progress lead me to conclude that the appearance of a nitrite in the 

 various processes for ozone is due to the power of nascent oxygen to de- 

 stroy by oxidation the ammonia generated by the action of water on ni- 

 trogen, the nitrous nitryle ; so that the odour and many of the reactions 

 assigned to ozone or nascent oxygen are really due to the nitrous acid 

 which is set free when the former encounters nitrogen and moisture. On 

 the other hand, nascent hydrogen, which readily reduces nitrates and ni- 

 trites to ammonia, by destroying the regenerated nitrite of the nitryle, 

 produces ammonia in many cases from atmospheric nitrogen. 



§ American Journal, vol. viii. p. 93. 



C2 



