INDIUM. 137 



acid oxidizes it rapidly. Heated to redness it vola- 

 tilizes and barns with a violet flame, which deposits 

 a yellow coating on the sides of the crucible. Its 

 specific gravity at 15 is equal to 7.362. Its equiva- 

 lent, according to Winckler, is 35.9. 



V. Combinations of Indium. 



The oxide (In O) seems to be the only combination 

 with oxygen. It is honey-colored, and transparent 

 when it is prepared by the calcination of the hydrate: 

 heated it becomes brown. 



The calcined oxide is slightly soluble in acids when 

 cold ; dissolves rapidly in them when heated. 



The salts of indium are white. Zinc precipitates 

 indium from its solution in the form of brilliant scales. 



The hydrate of oxide of indium forms a bulky, 

 white precipitate, which resembles aluminum, and 

 yields like this metal a horny mass when dry. It is 

 completely insoluble in ammonia, potassa, and soda. 



The carbonate and phosphate of indium are white. 



In the solutions of oxides of indium the yellow fer- 

 rocyanide of potassium gives a white precipitate. The 

 red ferridcyanide and sulphocyanide of potassium, 

 gallic acid, and chromate of potassa give no precipi- 

 tate. 



The oxalate of indium is crystalline 



The sulphate gives imperfect crystals. 



The nitrate crystallizes with difficulty in an aqueous 

 solution. 



The very acid solutions give small prisms joined in 

 bundles. 



The sulphide of indium is separated in the form of 

 a yellow gelatinous precipitate, which, when dried, 

 gives hard and brittle fragments. The presence of 

 acids prevents the precipitation of indium by hydro- 

 sulphuric acid ; it is not the same with the sulphide of 



12* 



