on the Peroxide of Hydrogen. 37 
of oxygen, than the metal has, the liquid becomes negative, thus ac- 
ting the part of the copper plate of a battery, while the metal be- 
comes positive, supplying the place of the zine plate. The liquid is 
thus resolved into water and oxygen. If the metal be very oxyda- 
ble, it retains the oxygen, which is evolved if gold, platina, &c. be 
used. We need scarcely refer to the-wires of a battery, for a paral- 
lel case. 
When the peroxide of hydrogen comes in contact with the oxide 
of silver, the oxygen escapes from both, and the latter is reduced to 
the metallic state. To comprehend this most singular fact, it must 
be remembered, that metals combine, under certain circumstances, 
with more oxygen than under other circumstances ; and it must be 
especially recollected, that when the peroxide of potassium is placed 
in water, it gives off oxygen, and becomes a protoxide. — It is not 
going too far then, to suppose that a peroxide may result from the ac- 
tion of the peroxide of hydrogen on the oxide of silver, that this 
peroxide exists under no other circumstances, and is, like the perox- 
ide of potassium, decomposed by water. The conclusion will, per- 
haps, warrant this assumption. The oxide of silver, then, being put 
into the peroxide of hydrogen, the latter having no aftinity for oxy- 
gen, becomes negative, while the former, becoming positive, receives 
oxygen, and becomes a peroxide, to which the excess of oxygen 
must adhere very slightly. But the fluid in immediate contact with 
this peroxide has, by yielding its oxygen, been converted to water ; 
and we have, now, in contact, not peroxide of hydrogen and protox- 
ide of silver, but protoxide of hydrogen and peroxide of silver. The 
effect is, a total change in the electrical phenomena. The peroxide 
of silver becomes negative, and the protoxide of hydrogen positive. 
This galvanic influence forces the silver to reject the whole of the 
oxygen, returning to the metallic state; hence results the incorrect 
opinion, that the oxide of silver has decomposed the liquid, without 
receiving oxygen ; while, in reality, it has only received oxygen at 
one moment, to change its electricity, and reject it in the next instant. 
The same effect is produced by other oxides reducible by heat alone ; 
the oxide being reduced to a metallic state. 
Those protoxides which are not reduced by heat alone, become 
peroxides; and these peroxides are not reduced to a metallic form, 
as in the above cases, because the galvanic effect produced by their 
contact with water, is too slight. In this respect, they differ from the 
peroxide of potassium, and the (supposed) peroxides of silver, gold, 
&c. which cannot exist in water. 
