Mr. Davy’s Hypothesis of Electro-chemical Affinity. 247 
dicate the equal intensities of the powers thrown in. The 
vessel ad is made of metal, lest it should be thought that 
the change resided in the surface if made of glass, and 
contains a quantity of oxalic acid in solution. The other 
vessel / contains solution of lime, which ‘being naturally 
positive admits the use of glass for the convenience of 
seeing the result. The stop-cock is furnished with a long 
insulating handle, and the whole is set on an insulated 
stool. Matters being in this state, a full stream of positive 
electricity was poured in from a very powerful machine, 
through the two conducting wires. After the pith-balls 
were proved by wax, and the quadrant electrometers ob- 
served to stand the same number of degrees, the stop-eock 
was turned by its glass handle. On the mixture taking 
place, the oxalate of lime immediately precipitated. 
Having emptied and dried the apparatus, the whole. was 
arranged as before. The metallic vessel contained solution 
of oxalic acid, the glass-vessel was empty. <A stream of 
electricity was poured into the solution, and the stop-cock 
meanwhile opened: when the fluid touched the wire of the 
pith-balis in J, the pith-balls immediately diverged with 
positive electricity; clearly demonstrating that the acid so- 
lution had carried with it positive electricity. 
In the experiment the agency of negative electricity 
cannot be suspected. If any had been produced by the 
contact of the two svlutions, it must have been immediately 
destroyed by the constant streams pouring in from the ma- 
chine. I made use of oxalic acid and lime, these substances 
being instanced by Mr. Davy as remaining in different 
states when separated. r 
Oxygen and substances in which oxygen predominates, 
as acids, are attracted to positively electrified surfaces, and 
are repelled by surfaces negatively electrified. These bodies 
are therefore themselves in the negative state. Now if for- 
example phosphorous acid be negative and oxygen in the 
same state, why have these’substances so strong an attrac- 
tion, and why do they combine to form phosphoric acid ? 
It might be said that the phosphorus in the acid being po- 
sitive, although combined with oxygen in the negative 
state, but not to saturation, yet has an excess of positive 
electricity, and that this excess attracts the additional quan- 
tity of negative oxygen. Were this the case, phosphorous 
acid with its positive excess should be repelled by the posi- 
tive and attracted ‘by the negative pole; which is not only 
contrary to fact, but contrary to the hypothesis. i 
can 
