Intelligence and Miscellaneous Articles. 175 



12. The crystals of gallium-alum do not act on polarized light 

 (between two Mcols at extinction). 



13. A small crystal of gallium-alum was kept some time under 

 water, and then removed into a slightly supersaturated solution of 

 alumino-ammoniacal alum ; it immediately began to grow, and de- 

 termined the crystallization of the liquor. 



14. With ammonia in excess, gallium-alum behaves like the other 

 salts of this metal : a portion of the oxide is precipitated ; the other 

 part remains in solution. 



15. The very acid solution of Ga 2 Cl 6 is precipitated by the yel- 

 low prussiate (specimen 4). 



16. The ammoniacal solution of sulphate of gallium is decom- 

 posed by the voltaic current. Metallic gallium is deposited on 

 the platinum plate which serves as negative electrode. The posi- 

 tive electrode becomes covered at the same time with a whitish 

 coating, consisting of a pellicle which is easily detached from the 

 platinum and is insoluble in a large excess of NH 3 (specimen 5). 

 In a first operation 1*6 milligramme was deposited in 4 hours 30 

 minutes on a platinum plate of about 185 square millims. superficies. 

 The surface of the positive electrode was 877 square millims. The 

 pile was composed of five bichromate couples (zincs 17 X 10 centims.) 

 coupled in tension. The sample which I have the honour to offer to 

 the Academy (No. 1) weighs 34 milligrammes : it was deposited in 5 

 hours 40 minutes, on a surface of 123 or 124 square millims. ; the 

 positive electrode had a surface of 877 square millims. ; the current 

 was supplied by ten bichromate elements (zincs 17 X 10 centims.) 

 coupled in tension. 



17. Electro-deposited gallium forms a very adhesive layer. It is 

 hard. It cannot be very well polished by rubbing it with an agate 

 burnisher ; a better polish is obtained by forcible compression under 

 the burnisher : these two operations were performed on two faces 

 of specimen 1. By the latter method the metal acquires a brilliant 

 lustre, and appeared to me rather whiter than platinum. When 

 the electric current is suitably regulated, as well as the relative 

 dimensions of the electrodes, the gallium presents a fine frosted 

 surface of silvery whiteness, finely granulated, and strewed with 

 brilliant points, which the microscope shows to be crystals. 



18. Deposited on platinum, gallium does not oxidize notably 

 during the washing with cold or boiling water*, nor when dried at 

 nearly 200° in free air. It decomposes water acidulated with HC1 

 cold, and more rapidly when heated, with brisk liberation of hy- 

 drogen. 



The salts of gallium which have hitherto served for my researches 

 were derived from the blende of Pierrefit, of which a copious supply 

 was obligingly sent me by M. Malgor, Engineer of the Mine ; but 

 I have ascertained the presence of the new metal in other ores of 

 zinc, especially in a transparent blende from Santander, given me 

 by M. Eriedel. I believe that gallium will be met with in all the 



* The polished surface, however, is a little dulled after several days, 

 doubtless in consequence of a slight superficial oxidation. 



