182 THE ATOMIC WEIGHTS. 



INDIUM. 



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 T 35 S rm - indium gave .6243 grm. In 2 O 3 . 

 .699 .8515 



Hence, in mean, In = 110.61, if = 16 ; a value known now to he 

 too low. 



An un weighed quantity of fresh, moist indium sulphide was also dis- 

 solved in nitric acid, yielding, on precipitation, 



.2105 grm. In 2 O 3 and .542 grm. BaSO 4 . 



Hence, with BaS0 4 = 233.505, In = 112.03 ; also too low. 



Soon after the publication of Reich and Richter's paper the subject 

 was taken up by Winkler .f He dissolved indium in nitric acid, evap- 

 orated to dryness, ignited the residue, and weighed the oxide thus 

 obtained. 



5574 S rm - I* 1 gave .6817 S rm - In 2 O 3 . 

 .6661 " .8144 " 

 .5011 " .6126 " 



Hence, in mean, if = 16, In = 107.76 ; a result even lower than the 

 values already cited. 



In a later paper by Winkler J better results were obtained. Two 

 methods were employed. First, metallic indium was placed in a solu- 

 tion of pure, neutral, sodio-auric chloride, and the amount of gold pre- 

 cipitated was weighed. I give the weighings and, in a third column r 

 the amount of indium proportional to 100 parts of gold : 



In. Au. Ratio. 



.4471 grm. .8205 grm. 57-782 



.8445 1.4596 " 57.858 



Mean, 57.820, .026 



Hence, if Au = 195.743, .0049, In = 113.179, .0517. 

 Winkler also repeated his earlier process, converting indium into 

 oxide by solution in nitric acid and ignition of the residue. An ad- 



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

 t Journ. fur Prakt. Chem., 94, 8. 

 % Journ. fur Prakt. Chem., 102, 282. 



