PRODUCED BY BODIES ACTING BY CONTACT. 9 
est importance ; it takes place only at the surface of solid bodies, 
and indeed in the ratio of the extent of that surface; but bases 
and acids act upon it in quite a different manner; the former 
excite the decomposition of the binoxide of hydrogen, the latter 
render it more stable. 
The decomposition of the chlorate of potass in contact with 
oxide of copper, binoxide of manganese, and other oxides of this 
kind, are likewise peculiarly interesting. When chlorate of 
potass is heated it melts, and, at a little higher temperature, it 
is converted into oxygen, chloride of potassium, and into hy- 
perchlorate of potass, which in turn is decomposed into oxy- 
gen and into chloride of potassium. But if, instead of heating 
the chlorate of potass alone, it is previously mixed with one of 
the oxides which I have just mentioned, it is converted into 
oxygen and chloride of potassium, at the temperature of its fu- 
sion, without the production of hyperchlorate of potass. 
To obtain an exact idea of the action of the oxides in these 
cases, we may make the following experiment. We put into 
one closed tube a mixture of oxide of copper and chlorate of 
potass, and into a second introduce only some chlorate; these 
are furnished with bent tubes for collecting the gases, and are 
placed together in a metallic bath. At a certain temperature 
the chlorate mixed with oxide of copper is completely decom- 
posed, whilst the chlorate alone does not yield a trace of oxygen. 
On mixing the chlorate of potass with silex it behaves exactly 
as the chlorate alone. 
The decomposition of the chlorate of potass is accompanied 
by a development of heat. This phenomenon occurs during the 
decomposition of the binoxide of hydrogen. To this heat, or 
rather to the cause which developes it, is attributable the simul- 
taneous decomposition of the binoxide of hydrogen and of the 
oxide of silver, as well as of other oxides which part with their 
oxygen at a high temperature. 
The conversion of lignine and of starch into dextrine, that of 
dextrine, of gum and sugar into glucose, is effected by a liquid 
body. 
It is known that on boiling starch with dilute sulphuric acid, 
it is speedily converted into dextrine and glucose. At whatever 
period of the operation we examine the liquid, we always find 
in it sulphuric acid in a free state and always in the same quan- 
tity; but the reaction, which consists of a simple fixation of 
