368 Intelligence and Miscellaneous Articles. 



aud still more difficult to maintain, the sheath, which at the 

 smallest agitation is transformed into ci'epiiating bubbles. 



This resonant form of electrolysis is accompanied by a super- 

 ficial disaggregation of the negative electrode ; the liquid soon 

 becomes charged with a very heavy black powder, which is essen- 

 tially composed of a hydride of platinum ; this decomposes in a 

 vacuum above 400° * and corresponds to the formula Pt^H. 



"We have hitherto only been concerned with the phenomena 

 met with at the negative pole. A sheath may also be observed 

 on the positive pole. For this purpose it is sufficient to invert 

 the conditions of the experiment, to attach to the negative pole the 

 wire of 4-5 millim., always deeply immersed in the same water 

 acidulated to ^^, and to gradually immerse the positive electrode, 

 which is a wire of 1"6 millim. diameter. There is considerable 

 difficulty in obtaining the sheath, which does not form sharply with 

 less than 50 volts, but which in return is remarkably persistent ; it 

 is moreover much less luminous. 



If the sheath is first of all formed on the stout wire, which is 

 immersed to a depth of 2 to 3 centim., in proportion as the stout 

 wire is immersed the sheath elongates to the point at which it 

 disappears suddenly; but at the same time the strength of the 

 current increases, and the other electrode may become so much 

 heated as in turn to be covered with a luminous sheath, or M'ith 

 crepitating bubbles. 



Similar phenomena, though far less intense, are met with in 

 water acidulated with phosphoric acid. The normal decomposition 

 is disturbed with greater difficulty, as has already been pointed out 

 by M. Mascart t. — Gomptes Benclus, Feb. 11, 1889. 



ON THE ELECTKOLYTIC BEHAVIOUK OF MICA AT HIGH 

 TEMPERATURES. BY W. H. SCHULTZE. 



The results of this investigation are as follows : — 

 Mica split parallel to the planes of cleavage shares with glass the 

 property of becoming a better conductor for the current as the 

 temperature rises. After reaching a maximum, its conductivity 

 diminishes ; and at a certain high temperature it becomes infinitely 

 small. 



Comparing mica and glass, it is seen that even at a high tempe- 

 rature the former is the better insulator. — Wiedemann's Annalen, 

 vol. xxxvi. p. 635, 1889. 



* Berthelot, Annates de Chimie et de Physique, 5th series, vol. xxx. 

 p. 530 (1883). 

 t Journal de Physiqixe, series 2, vol. i. p. Ill (1882) . 



