TRANSACTIONS OF THE SECTIONS. 47 
readily than the corresponding hydride or chloride; and therefore the chemical 
character of acetic and of trichloracetic acids depends much more on the oxidized than 
on the other constituent, and they thus have a marked resemblance. The oxidized 
constituent is united to the other in a manner different from that in which oxalic 
acid is united to bases in the oxalates, inasmuch as, while the basic water of 
hydrated oxalic acid is displaced when oxalic acid unites with a base, in hydrated 
acetic and trichloracetic acids there is the same proportion between the basic water 
and the oxidized carbon as there is in oxalic acid. 
Now has not this a great resemblauce to the view entertained by most modern 
chemists, that acetic acid is a compound of the radical carboxyl (half a molecule of 
oxalic acid) and the radical methyl (half a molecule of methyl gas), that trichlor- 
acetic acid similarly contains the same radical carboxyl and the radical C Cl,, and 
that the prominent chemical properties of these bodies depend upon their contain- 
pip Mette and that they therefore resemble each other ? 
he modern view contains nothing inconsistent with that of Berzelius; but it no 
doubt contains something more: it contains an explanation of the difference between 
the manner in which carboxyl is united to methyl in acetic acid, and the manner in 
which oxalic acid is united to bases in the oxalates. But it will surely be admitted 
that Berzelius was here far ahead of his opponents—so far ahead, that they alto- 
gether failed to see his meaning, and looked upon his argument as a clumsy device. 
The treatment by Berzelius of the constitution of the sulpho-acids furnishes a 
aia, similar case. These are now regarded as compounds of the radical 
O, OH (which we may call sulphoxyl). This radical is half a molecule of hypo- 
sulphuric acid ; and Berzelius considered them coupled compounds of hyposulphurie 
acid, adopting at once the view first brought forward by Kolbe in his classical me- 
moir on the sulphite of perchloride of carbon and the acids derived from it. 
I might pursue the history of the carbon- and sulpho-acids further, and trace the 
development of the theory of their constitution through the discoveries of Kolbe, 
and his beautiful application to the cases of carbon and sulphur of Frankland’s far- 
sighted speculation on the constitution of the organo-metallic bodies, pointing out 
the relation of Kolbe’s views of the constitution of acids, alcohols, aldehydes, and 
ketones to the Berzelian theory on the one hand, and to the opinions of modern 
chemists on the other; but the greater part of such an historical sketch has been 
given very recently by Kolbe himself in the ‘Journal ftir praktische Chemie,’ and 
I may therefore omit it. 
It would be easy to bring forward cases to show that our present views can be 
directly derived from the substitution theory and the types of Dumas and Gerhardt, 
through the complications of multiple and mixed types and the labyrinthine 
formule to which these gave rise, to the wonderfully simple and comprehensive 
system of Kekulé ; but that is unnecessary, as this development has been fully and 
ably described by more than one thoroughly competent writer. 
We have been discussing a case in which Berzelius was right in considering a 
compound of carbon, oxygen, and chlorine as composed of two parts—an oxide and 
a chloride of carbon. It is only just that we should take some notice of cases, at 
first sight similar, in which modern chemists would be inclined to think that he was 
wrong. This is the more necessary, as an examination of these cases will enable 
us to see what was the really valuable contribution made to speculative chemistry 
by the substitution theory. 
Compounds containing three elements were formulated in two different ways by 
Berzelius :— 
Ist. One of the elements was represented as combined with a radical composed 
of the other two, as:—hydrocyanic acid, H,.C,N,; ether, C, H,,.0. 
2nd. The ternary compound was represented as composed of two binary com- 
pounds, having one element common, as :—caustic potash, KO, H, 0; chromochloric 
acid, 2Cr O,, Cr Cl,. 
Phosgene gas was at first formulated in the former of these ways as CO, Cl,; but 
latterly he was forced, in consistency, to give up all radicals containing oxygen or 
other strongly electro-negative element*, and to write the formula of phosgene gas 
* In 1838 Berzelius was inclined to regard C, O,, to which he gave the name “ oxaty],” 
as the radical of oxalic acid and oxamide, 
