4 
PROFESSOR DANIELL AND DR. MILLER ON THE 
derived from considerations purely chemical. The double diaphragm cell which we 
chiefly employed in these experiments, is represented in the annexed wood-cut. 
A and B are the two halves of a stout glass cylinder, accurately ground so as to fit 
with shoulders liquid tight. C is a hollow ring of glass, also ground on either side, with 
a flat shoulder to fit against the two half cylinders, which are pressed home by the 
screws. Each side of the ring is furnished with a rim, which is grooved to admit of 
a thin piece of bladder being tied over it to form a kind of drum ; at K is a small hole 
to admit of the cavity being filled with a liquid. D and E are two bent tubes, fitted 
to the two half cylinders for collecting the gases evolved in the experiments, g and h 
are two circular platinum electrodes connected by wires, i, f (passing through corks 
in the necks of the half cylinders), with the battery. The apparatus when adjusted 
forms three compartments, each of which may be filled with the same or a different 
liquid, and the whole may be supported on a light frame of wood. 
We will not attempt to describe the particulars of every experiment referred to in 
the following pages, for their number is very great, and their details would be both 
tedious and useless ; we will only select some of the principal, in the results of which 
we can trace no ambiguity ; and have no doubt we shall obtain credit for every care 
in determining the purity of the substances which we employed, and in making the 
various analyses which were required. 
(a.) A strong solution of tribasic phosphate of soda and water (2NaO, HO, P 2 0 5 ) 
(rhombic phosphate) was placed in the platinode cell of the diaphragm apparatus ; 
the centre cell and the zincode cell were both charged with a dilute solution of soda 
(^g-). The power of twenty cells of the small constant battery was transmitted 
through it, oxygen was evolved at the zincode, and in thirty-seven minutes 48 cubic 
inches of hydrogen were collected from the platinode ; the experiment was then 
stopped and the solutions examined. 
The liquid from the zincode cell was carefully neutralized with nitric acid, and 
then gave a copious yellow precipitate with nitrate of silver, soluble in nitric acid, 
and in ammonia, the well-known characters of the tribasic phosphate of silver (3AgO, 
P 2 0 5 ). The solution in the platinode cell had become much more alkaline than at 
first, but when neutralized with nitric acid, gave a similar yellow precipitate with 
