204 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



electrolytically upon copper, forming a hard layer, difficult 

 to burnish and rather whiter than platinum. It was orig- 

 inally found in a blende from the Pyrenees, but has since 

 been detected in blendes from various other sources, so that 

 the discoverer thinks it may be quite widely diffused. Its 

 most important chemical feature is that it forms apparently 

 a true alum, thus belonging with indium and aluminium in 

 classification. This fact is particularly interesting when 

 considered in connection with a brief article by jMendelejeff. 

 This author some few years ago, in his paper upon the " pe- 

 riodic law," ventured upon theoretical grounds to predict the 

 existence of several then unknown metals. In all probabil- 

 ity gallium is one of these, and will fill a gap w^hich Mende- 

 lejeff pointed out in the aluminium group. The verification 

 of such a prophecy might well afford a parallel to the dis- 

 covery of the planet Neptune. 1 A. 



GALLIUM. 



M. Boisbaudran has succeeded in isolating about half a 

 gramme of this new metal, and has redetermined some of its 

 leading characteristics. In the fused state it is of a fine 

 silver white color; but in crystallizing it assumes a pro- 

 nounced bluish tint, and loses considerably in brilliancy. 

 The metal, by cooling from fusion, may be obtained in iso- 

 lated crystals, which are octahedral. The melting-point, 

 previously put at 29.5 Centigrade, is now, as a mean of six 

 closely agreeing measurements, fixed at 30.15. 



Great interest attaches to the specific gravity of gallium. 

 A few months ago it was determined to be 4.7 at 15 Centi- 

 grade, the determination being made wdth a specimen of 

 metal weighing only six centigrammes. But, calculated 

 upon the basis of Mendelejeff's law the law by which the 

 existence of gallium was predicted the value should have 

 been 5.9. Two new determinations, now published by Bois- 

 baudran, give 5.935 and 5.956. This agreement with theory 

 is very close and very striking. 6 i?, LXXXIIL, 611, Sep- 

 tember 18. _____ 



DESILVEEIZATION OF AEGENTIFEROUS ZINC. 



The desilverization process introduced by Parkes in 1850, 

 but subsequently neglected in consequence of the difficulty 



