On Mr. Davy’s Hypothesis. 245 
impure acids and alkalies of commerce, are to be had 
every where, All the instruments and bottles are arranged 
in such a manner that they may be seen at one view when 
the chest is open, and they are so packed that they may 
readily be taken out; and, when replaced, fit in such a way, 
that the whole, when the chest is locked, may be turned 
upside down without risk of receiving injury. 
Compton-Street, Soho, - Freprick AccuM. 
March 1, 1811. 
v 
XLIV.—Olservations and Experiments concerning Mr. 
Davy’s Hypothesis of Electro-chemical Affinity.—By 
M. Donovan, Esq. 
[Concluded from p. 233.] 
‘ 
Weauen water is decomposed by means of metallic wires, 
which have an affinity for oxygen, the wire conveying po- 
sitive clectricity beeomes oxidated. When a platina wire 
is employed, it does not oxidare. But by the hypothesis 
the union ought to take place; for the platina, naturally po- 
sitive, has its energy considerably exalted, and consequently 
should unite with as much force to negative oxygen as any 
other metal under the same circumstances. The matter is 
simply thus: The canse of combination is attraction, the 
cause of attraction is existence in differently electric states : 
the more energetic these states are, the more violent is the 
attraction. Mr. Davy’s words on this part of the subject 
are: ‘ As the chemical attraction between two bodies 
seems to be destroyed by giving one of\them an electric 
State different from that which it naturally possesses, that is, 
by bringing it artificially into a state similar to the other, 
so it may be increased by exalting its natural energy. Thus, 
while zinc, one of the most oxidable of the metals, is inca- 
pable of combining with oxygen when negatively electrified 
in the circuit, even by a feeble power; silver, one of the least 
oxidable, easily unites to it when positively electrified; and 
the same thing may be said of other metals.” In the in- 
stance present, the oxygen is in the negative state, the pla- 
tina is strongly positive, and precisely in the same circum- 
stances as the silver in Mr. Davy’s instance. Why then 
do they not combine witb violence* ? 
It 
* In the Philosophical Magazine, vol. xxxili. p. 88, we find the followings 
from a Correspondent : \ 
“ Mr. Davy showed, by a refined application of his principles, that, in the 
decomposition of a neutral salt in solution, the order of the actrangement 
O38 varies, 
