124 ON THE THEORY OF TYPES IN CHEMISTRY. 
In a notice of his essay, published in September, 1848, (Iéid, 
vi., 173) I endeavored to show that Laurent’s view might be 
farther extended, so as to include in the type of water “ all those 
saline combinations (acids) which contain oxygen; and im a paper 
read before the American Association for the Advancement of 
Science at Philadelphia, in Sept., 1848, I farther suggested that as 
many neutral oxygenized compounds which do not possess a saline 
character are derivatives of acids which are referable to the type 
H,O,, “we may regard all oxygenized bodies as belonging to this 
type,” which I farther showed in the same essay, is but a derivative 
of the primal type H,, to which I referred all hydro-carbons and 
their chlorinized derivatives, as also the volatile alkaloids, whieh were 
regarded “as amidized species”? of the hydro-carbons, in which the 
residue amidogen, NH,, replaced an atom of H or Cl., or what is 
equivalent, the residue NH was substituted for O, in the eorres- 
ponding alcohols. (ibid viii., 92.) 
In the paper published in Sept., 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 NO, for H, 
were necessarily monobasic, and I then pointed out the possible 
existence of the nitric anhydrid (NO,),0,, which was soon after 
discovered by Deville. Gerhardt at this time denied the existenee 
of anhydrids of the monobasic acids, while he regarded anhy- 
drids as characteristic of polybasic acids, and indeed was only led to 
adopt my views by the discovery of the very anhydrids whose forma- 
tion 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,HO,H)O,. Tribasic acids in like manner are to be 
regarded as derived from .a third equivalent of water in whicha 
bibasic residue replaces an atom of hydrogen. The idea of poly- 
meric types was further illustrated in the same paper, where three 
hydrogen types were proposed, (HH) (H,H,) and (H,H.,) corres- 
ponding to the chlorids MCI, MCl, and MCl,. It was also 
* The anhydrids of the monobasic acids correspond to two equivalents of the acid, minus 
one of water, as, 2 (Cg Hy 04)—H2 Og=C, Hg Og, while one equivalent of a bibasic acid 
(itself derived from 2 (Hy O2) loses one of water, and becomes an anhydrid as C, H, Oe— 
H, O22 =C2 O4. So that both classes of anhydrids are to be referred to the type of ane 
molecule of water H, Og. 
