Chemistry and Physics. 137 



its original properties in hydrogen peroxide than in water. 

 Spring concludes also, from determinations of the specific heat 

 of hydrogen peroxide, that the potential energy of the elements 

 is not completely used in forming this compound. 



Brtjhl (Berichte, 1895, 2847) has recently described some 

 important work upon the subject under consideration. Using 

 Wolffen stein's process, usually omitting, however, the extraction 

 with ether, he has prepared hydrogen peroxide in a water-free 

 condition. The boiling-point of his purest product was 69*2° at 

 26 n,m . He observed that the distilled substance is much more 

 stable than that which is less pure, and that the nearly water- 

 free liquid suffered scarcely any decomposition when kept cool 

 and in a dark place for five or six weeks. Agitation promotes 

 decomposition, as does also an increase in the surface with which 

 the substance is in contact. Sharp points and rough surfaces 

 have a marked action, and when the compound is brought into 

 contact with a ground-glass surface the decomposition is violent. 

 Paper, cloth, wool and asbestus cannot be used for filtering the 

 concentrated liquid ; in fact, wool is ignited by contact with a 

 small amount of it. Gun-cotton does not decompose it and can 

 be used for its filtration. Briihl considers the specific gravity of 

 hydrogen peroxide as the best criterion of its purity. The 

 highest specific gravity which he obtained was, d% =1-4584, while 

 a liquid containing 99*48 per cent of the pure substance, accord- 

 ing to analysis, had a density of 1*4094. He experienced no 

 trouble from explosions when solutions were concentrated and 

 purified simply by evaporation and distillation, but some material 

 which had been repeatedly treated with ether gave off much gas 

 with an odor of ozone upon distillation, and an oily, colorless resi- 

 due, which did not volatilize at 100° was left. This fluid, amount- 

 ing to only I or 2 CC showed but slight explosive properties 

 when a drop of it was conveyed into a Bunsen flame by means of 

 a platinum spatula; but when a glass rod with a sharply cut end 

 was brought into contact with the remainder, a fearfully violent 

 explosion took place which caused much damage in the labora- 

 tory. A part of this particular sample of hydrogen peroxide bad 

 previously caused a serious explosion in Spring's laboratory. 

 Brtihl believes that the explosive compound is formed by the 

 action of hydrogen peroxide upon ether, but nothing is as yet 

 knOwn concerning its composition. 



Having determined the molecular refraction and dispersion of 

 the pure hydrogen peroxide, with the result that the numbers 

 found were much larger than those calculated for di-hydroxyl, 

 Brtihl concludes that the oxygens in the compound must have a 

 multiple linking between themselves. This conclusion conforms 

 with Traube's formula, HO: OH, but Brtihl objects to this on 

 the ground that neither oxygen nor the other members of the 

 same periodic group show trivalence. But since sulphur, sele- 

 nium and tellurium show tetravalence, and since there is already 

 ground for supposing the existence of tetravalence in oxygen, as, 



