1866] Physics. 433 
oxygen leaves it to do its work nothing but water is left ; nothing 
being added to be washed out. 
The peroxide, as sold, contains a little acid (sulphuric) ; when 
made alkaline it does not keep so well. If a drop is put upon a 
photograph it very slowly bleaches; its use in this undiluted state 
is not recommended. Again, if the peroxide, as sold, is neutralized, 
the bleaching does not take place, at least in an hour, an ample 
time. or neutralization soda may be used. 
Hzat.—M. Cailletet has continued the experiments of Deville 
on the dissociation of compound gases at high temperatures. 
The author, by peculiar contrivances, drew air from blast 
furnaces, and submitted it to analysis. The first analysis is of gas 
taken from the hottest part of a furnace, and rapidly cooled by a 
stream of water, on the plan of M. St. Claire-Deville. The mixture 
was composed of— | 
Ig ES 
Oxygen ° . : - 15°24 15°75 
Hydrogen. 5 ° ‘ 1:80 a4 
Carbonic oxide c ; Peal 1°30 
Carbonic acid “ é feo. 00 Dai 
Nitrogen f - ; - 77°86 80°80 
100-00 100-00 
These results confirm those of Deville, and show that oxygen 
does not combine with hydrogen, carbon, or carbonic oxide at very 
high temperatures. The author afterwards took air from furnaces 
at lower temperatures, and the results show the gradual disappear- 
ance of the oxygen with the abasement of the temperature, and of 
course the increase of carbonic acid. M. Cailletet concludes that 
compound gases cannot exist at high temperatures. 
A curious fact in relation to the storage of solar heat for future 
use has been communicated by M. Jeannel to the French Academy 
of Sciences. Fused acetate of soda, allowed to cool in the open air, 
crystallizes in prismatic needles at + 58°; allowed to cool, however, 
in a limited amount’ of moist air, it does not crystallize even at zero, 
but becomes a soft translucent mass. If, after having been so 
cooled, it is exposed freely to dry air, and touched with a dry solid 
body, it suddenly assumes the ordinary crystalline form of prismatic 
needles, and rises to the crystallizmg pomt + 58°, or near it. M. 
Jeannel remarks that this experiment shows how solar heat may be 
stored up and made to re-appear again at will. It is possible, he 
says, in our climates to raise acetate of soda under bell-glasses or 
glass frames to + 59°. The acetate so exposed and cooled, sheltered 
from the air, does not crystallize, and is always ready to give out 
the heat again on being touched with a dry solid body. 
M. de Vignette Lamotte has sent tothe French Academy a long 
