610 
POPULAR SCIENCE REVIEW. 
nitric oxide in the manufacture of sulphuric acid. There is no doubt tiiat 
several peroxides of cobalt with various proportions of oxygen exist. The 
writer’s experiments have shown him that the proportion of oxygen in 
peroxide of cobalt is variable, and the simplest explanation of this process 
is that a lower peroxide abstracts oxygen from the hypochlorite of lime to 
form a higher oxide, which is again decomposed into a lower oxide and 
oxygen. The peroxide made use of in one experiment, may be employed 
again to decompose a fresh quantity of hypochlorite of lime. From one- 
tenth to one-half per cent, is sufficient to effect the reaction. The following 
are the advantages of Herr Fleitmann’s method : — (1.) The evolution proceeds 
with extraordinary regularity, and the gas is collected with the greatest ease, 
which makes the process specially applicable as a lecture experiment. dVlien 
the mixture has been heated to 70° or 80° the lamp may be removed, as the 
heat of the liquid will then be quite sufficient to carry on the reaction to 
the end. 
(2.) The idIioU of the oxygen, is obtained from the material, Avhile only a 
part is procured by heating f>eroxide of manganese. 
(3.) The process has the advantage of greater cheapness than when chlorate 
of potass is employed. 
Itjs necessary to employ a clear solution of chloride of lime, as a thick or 
murky solution will froth oveir. The best method of making a clear and 
strong solution is by first extracting one portion of chloride of lime vdtli 
water, decanting the clear liquor, and then making use of that to exliaust 
another portion of the chloride. In this way it is easy to get a liquor ’v^^hich 
wdll evolve from twenty-five to thirty times its volume of oxygen. — Vide 
Annalen cler Chemie unci Pharmacie, April. • 
Explosive Compounds of Magnesium. — In experimenting with magnesium, 
Mr. J. N. Hearder, of Plymouth, is said to have discovered some explosive 
compounds of tremendous power and striking peculiarities. He ignited a 
small portion (20 grains) of one of these compounds during a lecture which 
he gave at the Pljnnouth Mechanics’ Institute, the instantaneous and dazzling 
effect of which upon the audience was like that of a flash of lightning. On 
causing two bars of magnesium to form the terminals of a powerful voltaic 
battery a most intense combustion ensued : one of the bars speedily became 
red hot, entered into ebullition, and then burnt so furiously that it became 
necessary to plunge it into water, to prevent its falling on the platform. In 
this process portions of the burning metal detached themselves, and floated, 
blazing, on the surface of the water, decomposing it after the manner of 
potassium, and liberating hydrogen, which also burnt. 
Arborization 'producedhy Bulpliate of Copper. — Very beautiful arborizations 
may be produced by placing a few crystals of sulphate of copper in a very 
diluted solution of silicate of potash. This arborization is remarkable from 
the circumstance that it seems to reproduce in the silica solution the mossy 
appearance seen in agates. The stalks very often rise in the form of an 
arch ; this takes place when the solution is at a certain' degree of saturation. 
If it is very dilute, the arborescence rises vertically, and in a straight line. If it 
is too concentrated no arborization takes place ; the sulphate of copper merely 
becomes covered with a black coating. But in a profusely dense solution a 
curious fact is observable. After the formation of the vertical stalks, fresh 
