INDIUM. 219 



3.1044 grammes gallium ammonium alum, upon ignition, 

 left .5885 grm. Ga^Os- 



Hence Ga = 68.071. If = 16, Ga = 68.233. 



.4481 grammes gallium, converted into nitrate and ig- 

 nited, gave .6024 grm. GaaO^. 



Hence Ga = 69.538. If = 16, Ga = 69.693. 



These values, assigned equal weight, give these means : 

 If = 15.9633, Ga = 68.854. If O = 16, Ga = 68.963. 



In brief, for all practical purposes, 69 may be assumed as 

 the atomic weight of gallium. 



iisrmuM. 



Reich and Richter, the discoverers of indium, were also 

 the first to determine its atomic weight.* They dissolved 

 weighed quantities of the metal in nitric acid, precipitated 

 the solution with ammonia, ignited the precipitate, and 

 ascertained its weight. Two experiments were made, as 

 follows : 



■5 '35 g'"'"'''- indium gave .6243 grm. IHjOg. 

 .699 " .8515 



Hence, in mean. In = 110.61, if = 16; a value known 

 now to be too Ioav. 



An unweighed quantity of fresh, moist indium sulphide 

 was also dissolved in nitric acid, yielding, on precipitation, 



.2105 grm. In^Oj and .542 grm. BaSO^. 



Hence, with BaSO, = 233, In = 111.544; also too low. 



Soon after the publication of Reich and Richter's paper 

 the subject was taken up by Winkler.f He dissolved in- 

 dium in nitric acid, evaporated to dryness, ignited the resi- 

 due, and weighed the oxide thus obtained. 



* Journ. fur Prakt. Chem., 92, 484. 

 f Journ. fiir Prakt. Chem., 94, 8. 



