Chemistry and Physics. 155 



cently given fuller details in regard to the substance, and has 

 described also the corresponding sodium compound NaH. These 

 hydrides are colorless, transparent and crystalline, and are 

 formed by the action of hydrogen upon the metals at about 

 360°. At higher temperatures they are decomposed into their 

 elements. They are exceedingly sensitive towards moisture, and 

 are very active chemically. Potassium hydride takes fire when 

 exposed to oxygen at ordinary temperature, while both hydrides 

 ignite spontaneously in chlorine gas. When this combination 

 with chlorine takes place the sodium compound gives a blinding 

 light, and the temperature produced is sufficient to volatilize the 

 sodium chloride which is formed. — Bulletin, iii, xxviii, 1140. 



h. l. w. 



6. Combustion of the Three Varieties of Carbon. — Moissax- 

 has found that diamonds become incandescent in oxygen from 

 800° to 875°, samples of graphite at about 650° to' 70o°, and 

 amorphous carbon, according to its character, from 300° to 500°. 

 In each case, however, slow combustion began at a temperature 

 far below that of vivid incandescence ; slow formation of carbon 

 dioxide was observed with diamond at 720°, with graphite at 

 510°, and with a certain soft variety of charcoal at a temperature 

 as low as 100°. Experiments made with this charcoal in contact 

 with oxygen in sealed tubes, in one case for the space of a year 

 in the dark and in another case in sunlight during the month of 

 September, gave no evidence of slow combustion at ordinary 

 temperatures, for no carbon dioxide was detected. — Comptes 

 B.endus, cxxxv, 921. h. l. w. 



7. Ammoniacal Cnpric Chlorides. — By the action of liquid 

 ammonia upon anhydrous cupric chloride, Bouzat has prepared 

 a blue compound, OuCl 2 '6NH 3 . This has a dissociation tension 

 of 760 mm at 90°. From this substance, by loss of ammonia, a 

 blue compound, CuCl 2 '4NH 3 , and a green one, CuCl 2 "2NH 3 , are 

 produced. The first of these gives a tension of 7ti0 mm at 140°. — 

 Comptes Pendus, cxxxv, 292. a. l. w. 



8. Peculiar Radiation Phenomenon. — Many observers have 

 noticed a blackening of photographic plates in the dark, under 

 the influence of certain metals and organic bodies. J. W. Russel 

 attributes the action to superoxide of hydrogen. L. Graetz has 

 confirmed, in general, the observations of Russel. The latter 

 maintains that the action, although it penetrates various solid 

 organic substances and certain fluids, is not of the nature of a 

 radiation. Graetz does not agree with this conclusion, since the 

 action appears to penetrate thin metallic layers. Aluminum foil,, 

 of the thickness employed by Lenarcl in his research on the 

 cathode rays, is transparent to the action. One also obtains the 

 peculiar radiation if one blows away the vapor of the superoxide 

 of hydrogen from the photographic plate. Experiments of this 

 nature show that it is not the vapor merely which produces the 

 blackening. The radiation is either a direct ether radiation or 

 due to radio-active particles. One can therefore speak of H 2 2 



