464 THEORY OF TYPES IN CHEMISTRY. [XX. 



out the possible existence of the nitric anhydride (N0 4 ) 2 2 , 

 which was soon after discovered by Deville. Gerhardt at 

 this time denied the existence of anhydrides of the monobasic 

 acids, regarding anhydrides as characteristic of polybasis acids, 

 and indeed was only led to adopt my views by the discovery 

 of the very anhydrides whose formation I had foreseen.* 



In explaining the origin of bibasic acids I described them 

 as produced by the replacement, in a second equivalent of 

 water, of an atom of hydrogen by a monobasic saline group ; 

 thus sulphuric acid would be (S 2 H0 6 H)0 2 . Tribasic acids in 

 like manner are to be regarded as derived from a third equiva- 

 lent of water in which a bibasic residue replaces an atom of 

 hydrogen. The idea of polymeric types was further illus- 

 trated in the same paper, where three hydrpgen types were 

 proposed (HH), (H 2 H 2 ), and (H 3 H 3 ), corresponding to the chlo- 

 rides MCI, MC1 3 , and MC1 5 . 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 I referred sulphur- 

 ous acid S0 2 to this type, to which also probably belongs 

 selenic oxide. (At the same time I suggested that the odorant 

 form of oxygen or ozone was possibly 3 .) Wurtz, in his 

 memoir, published in 1855, adopts my view, and makes sulphur 

 vapor at 400 C., the type of the triple molecule. I further sug- 

 gested (American Journal of Science, V. 408; VI. 172) that 

 gaseous nitrogen is NN, an anhydride amide or nitryl, corre- 

 sponding to nitrite of ammonia (N0 8 ,NH 4 0) H 4 4 = NN. 

 This view a late writer attributes to Gerhardt, who adopted it 

 from me. (Ann. de Chiniie et Phys., LX. 381.) May not 

 nitrogen gas, as I have elsewhere 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 1 1 



* The anhydrides of the monobasic acids correspond to two equivalents of 

 the acid, minus one of water, as 2(C 4 H 4 4 ) H,0,= C 8 H 9 0; while one 

 equivalent of a bibasic acid (itself derived from 2HO t ) loses one of water, 

 and becomes an anhydride, as C,H,0 6 H,0, = C,0 4 . So that both classes 

 of anlmlriils are to be referred to the type of one molecule of water, H0i. 



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



