444 M. Winkler on Indium, 



far more convenient for the production of the new metal. Besides 

 small quantities of lead, iron, arsenic, and cadmium, it contains 

 0*0418 per cent, of indium. 



The method given by the discoverers, of precipitating by 

 ammonia*, in which oxide of indium is absolutely insoluble, 

 may be used ; and besides the method of separating given by 

 Weselskyf, the following may be used: — 



Granulated zinc is dissolved in dilute acid, care being taken 

 that a small quantity remains undissolved, and the liquid boiled 

 until there is no more disengagement of gas. In the precipi- 

 tate formed, which mainly consists of lead, all the indium is 

 contained, together with some arsenic, iron, and cadmium. 



Or to the solution some sulphuric acid is added, and it is then 

 neutralized with carbonate of soda until a feeble turbidity ensues ; 

 acetate of soda being added, the whole is then boiled for a time. 

 A ferruginous basic sulphate of indium is thus precipitated, 

 together with some oxide of zinc, which is washed by decantation. 



Either of the precipitates obtained by the above methods is 

 dissolved in nitric acid, the lead precipitated by sulphuric acid, 

 and the other foreign metals by sulphuretted hydrogen ; the 

 latter removed by warming, the iron oxidized by chlorate of pot- 

 ash, and precipitated by ammonia. The precipitate contains 

 indium, together with iron and some zinc. This is dissolved in 

 acetic acid and heated with sulphuretted hydrogen, which precipi- 

 tates all the indium, with some iron and zinc, which adhere to it 

 very pertinaciously. They are best removed by dissolving the 

 sulphide in hydrochloric acid, boiling well to expel sulphuretted 

 hydrogen, and allowing the mixture to stand for twelve to twenty- 

 four hours with excess of carbonate of baryta. This process is 

 well adapted for the quantitative determination of indium. 



The. oxide is best reduced by heating it in a very slow current 

 of hydrogen. The metal is thus obtained in several small 

 globules, which can be melted under cyanide of potassium to a 

 regulus. 



Indium in its colour resembles platinum ; it is softer than lead, 

 can be cut with a knife, and rolled out in thin sheets by very 

 slight pressure. It colours paper, and takes the brightest polish 

 with a fine cloth. It retains its lustre in the air. It dissolves 

 in dilute hydrochloric and sulphuric acids with disengagement 

 of hydrogen, gives sulphurous acid with concentrated sulphuric 

 acid, and is quickly oxidized by nitric acid. Heated in a cru- 

 cible to bright redness, it evaporates and burns with a violet light 

 to a yellow oxide. Its specific gravity is 7'362 at 15°. 



The oxide InO appears to be the only one. It is of a straw- 



* Phil. Mag. S. 4. vol. xxvii. p. 199 et seq. 

 t Ibid. vol. xxix. p. 328. 



