D. CHEMISTRY AND METALLURGY. 195 



the air. This subject has, however, been fully investigated 

 by WolfFhugel, who finds that, while a given quantity of 

 fresh air yields a very visible ozone reaction, yet ten or 

 twelve times that quantity taken from the interior of dwell- 

 ings produces no effect, even when the rooms are unused, 

 having previously been well aired. Wolffhugel has also 

 shown that there is a great absence of ozone in the air near 

 the ground. 7 (7, 11, 122. 



DECOMPOSITION OF WATER. 



Gladstone and Tribe find that when aluminum foil and 

 iodine are placed together in water, hydrogen is copiously 

 evolved. The same phenomenon takes place if aluminic io- 

 dide be substituted for iodine, its formation really being the 

 first part of the reaction just described. Aluminic bromide 

 or chloride acts in much the same manner, the aluminum 

 used being almost completely oxidized. The same experi- 

 menters sought to determine whether zinc or iron, heated 

 with solutions of their respective iodides, would yield hy- 

 drogen, and obtained only negative results. These metals, 

 however, with aluminic iodide in water, produced readily a 

 copious evolution of the gas. Aluminum alone decomposes 

 water, according to Deville, only at a white heat. But 

 Gladstone and Tribe, by simply coating aluminum foil either 

 with copper or platinum, procured couples which eftected 

 the decomposition quite easily at the low temperature of 

 100 Centigrade. 21 A^ 822, Sejyt^mber, 1875. 



DECOMPOSITION OF WATER BY PLATINUM. 



Deville and Debray find that when a mixture of potassium 

 cyanide and spongy platinum is heated together in the neigh- 

 borhood of a little water, at about 500 or G00, a vacuum 

 having first been established, great quantities of hydrogen 

 are evolved, and the well-known platino-cyanide of potassi- 

 um is formed. The hydrogen is not pure, but contains small 

 quantities of ammonia, and from four and a half to twelve 

 per cent, of carbonic oxide. 6 jB, January 24. 



CRYOIIYDRATES. 



About a year ago Professor Guthrie described under the 

 above name a set of hydrates which exist only at very low 



