MM. F. Reich and Th. Richter on Indium. 201 



reprecipitated by potash, and thus separated from every metal 

 except iron. By boiling the acid solution after saturation with 

 acetate of soda the iron is precipitated, and the filtrate contains 

 much of the indium, but a still larger quantity is carried down 

 with the oxide of iron. 



The best separation was effected by precipitating the iron 

 carefully by bicarbonate of sodium. If there is a large excess of 

 iron present, it is best to precipitate this metal at first incom- 

 pletely, to filter, and then to complete the precipitation of the 

 iron in the filtrate by a gradual addition of a very dilute solu- 

 tion of the bicarbonate. On boiling the filtrate and addition of 

 a little more sodium-salt, J;he indium is precipitated as hydrate or 

 carbonate. 



The solution of the chloride of indium produced with ferro- 

 cyanide of potassium a white precipitate, tinged slightly blue by 

 a trace of iron. 



Ferricyanide of potassium gives no precipitate. Sulphocyanide 

 of potassium produces a pale red coloration due to a trace of iron. 



As the oxide possesses many properties in common with alu- 

 mina (from which, however, it is distinguished by its insolubility 

 in potash, and its reducibility before the blowpipe), it is well to 

 mention that when heated on charcoal and moistened with 

 cobalt solution it does not yield a blue colour ; and after heating, 

 it completely although slowly dissolves in hydrochloric acid. By 

 adding sulphate of potassium to a solution of sulphate of indium, 

 no crystals of alum were obtained on evaporation. 



We have also ascertained in what mineral indium occurs. 

 By passing chlorine over the pure zincblende, arsenical pyrites, 

 and iron pyrites contained in the mixed ore from which the 

 indium had been prepared, it was found that the blende was the 

 only one of the minerals which contained indium. The chloride 

 of indium sublimes in the tube, and a portion of it is carried 

 over into the wash-water, whereas the greater part of the chloride 

 of zinc remains in the bulb. 



We have likewise found indium in the distilled zinc prepared 

 from the Freiberg blende, and we have obtained the oxide from 

 this source. According to our experiments, a very large quan- 

 tity of ammonia is required, in comparison to the yield of indium, 

 in order to separate this from the excess of zinc, as we obtained 

 only 1 part of the oxide of indium from 1000 parts of zinc dis- 

 solved. The precipitate thus obtained is dissolved, treated with 

 sulphuretted hydrogen, after oxidation again precipitated with 

 ammonia, and the indium and iron separated according to the 

 method above described. 



