134 * INDIUM. 



I. Separation of the Indium. 



a. BY MEANS OF ZINC. The granulated zinc is 

 dissolved in dilute sulphuric or hydrochloric acid, 

 taking care to leave a small quantity of zinc not dis- 

 solved. The solution is heated to the boiling point, 

 and kept there until no trace of gas is discernible. A 

 spongy, metallic substance is obtained in this way, 

 consisting mostly of lead, and which contains, also, 

 arsenic, iron, cadmium, and all the indium of the ori- 

 ginal zinc, if care has been taken to leave in the liquid 

 an excess of zinc. It can be shown that all the indium 

 is precipitated by testing the filtered liquid with am- 

 monia, adding enough to dissolve the precipitate 

 formed, filtering and examining the residue with the 

 spectroscope. 



b. BY MEANS OF ACETATE OF SODA. This method 

 of separation depends upon the tendency of the indium 

 to form basic salts, a property which belongs to it as 

 much as to the oxide of iron. It is applicable for so- 

 lutions containing indium and chloride of zinc. 



A little sulphuric acid is added to the solution, if 

 it does not already contain it. It is then neutralized 

 with carbonate of soda until the liquid remains cloudy. 

 Acetate of soda is then poured upon it, and boiled for 

 some time. A precipitate is thus formed of basic sul- 

 phate of indium, together with iron and a little oxide 

 of zinc, which is filtered and washed. It is preferable 

 to decant it on the filter, the precipitate being gelatin- 

 ous, and quickly filling the pores of the filter. 



C. BY THE MEANS OF CAEBONATE OF BAEYTA. 



The oxide is completely precipitated, even when cold, 

 from its solution by the carbonate of baryta ; the liquid 

 should be acidulated by either nitric or hydrochloric 

 acid. It is mixed when cold with carbonate of baryta 

 recently precipitated, stirred for some time, and then 



