Obituary Notices. 
543 
which are contained in it. For instance, a drop of hydrochloric 
acid being supposed to be made up of a great number of molecules 
of the composition C1H, the proposition at which we have just 
arrived would lead us to believe that each atom of hydrogen does 
not remain quietly in juxtaposition with the atom of chlorine with 
which it* first united, but, on the contrary, is constantly changing 
places with other atoms of hydrogen, or, what is the same thing, 
changing chlorine.” 
The observed facts of balanced actions of double decomposition 
led Williamson to this view, and it is interesting to note that the 
observed facts of electrolysis led Clausius quite independently to a 
sotnewhat similar hypothesis about seven years later. 
A paper read before the Chemical Society of London, June 1851, 
contains, besides further details as to the preparation, analysis, and 
vapour density of the new intermediate ethers, a very important note 
on the constitution of acetone, and an account of an intermediate 
ketone, with a very clear statement of the constitution of these 
bodies and a forecast of the general method of preparing aldehydes 
afterwards independently discovered by Limpricht and by Piria. 
In a paper in the Chemical Gazette , 1851, he points out the 
analogy between ether and the anhydrous monobasic organic acids, 
then unknown, but soon afterwards discovered by Gerhardt, who 
obtained them by a process perfectly analogous to that used by 
Williamson for the preparation of the ethers. 
As Williamson had thus, in 1850, established the “water 
type” on a secure experimental basis, so, in 1854, he extended 
similar reasoning and demonstration to the case of sulphuric acid, 
and showed how dibasic acids and their derivatives can be referred 
to the double type of water. 
In a paper communicated to the Royal Society of London he 
writes : — “ An atom of nitric acid, being eminently monobasic, is, 
as we have already shown, represented in the monobasic type 
gO by the formula in which peroxide of nitrogen (N0 2 ) 
replaces one atom of hydrogen. In like manner, hydrate of potash 
go) is obtained by replacing one atom of hydrogen in the type by 
its equivalent of potassium ; and nitrate of potash by a 
