200 MM. P. Reich and Th. llichtcr on Indium. 



taric acid added to an acid solution of the oxide of indium pre- 

 vents its precipitation by ammonia. If sulphide of ammonium 

 be added to the tartaric acid solution saturated with ammonia, 

 a voluminous white precipitate falls down, coloured slightly 

 greenish from the presence of a trace of iron. 



Potash precipitates the hydratcd oxide from acid solutions in 

 the same" form as ammonia does, and as completely. Carbonate 

 of sodium precipitates the indium compounds also completely, but 

 the precipitate is crystalline. The white precipitate thrown 

 down from boiling solutions, after drying, dissolves in dilute sul- 

 phuric acid with effervescence ; it therefore consists of carbonate 

 of indium. 



The oxide ignited in a bulb-tube in an atmosphere of hydro- 

 gen underwent no alteration, and no water was formed. The 

 oxide, mixed with powdered charcoal and ignited in a bulb-tube 

 in an atmosphere of chlorine, yielded by moderate heat a very 

 volatile chloride, which condensed in the cold part of the tube. 

 This sublimate possessed a yellow colour, but it still contained a 

 trace of iron, and a few crystalline scales appeared white and 

 had a pearly lustre ; so that it is probable that the yellow colour 

 was due to a trace of ferric chloride. 



The chloride of indium is extremely hygroscopic. If it is 

 again heated, hydrochloric acid is evolved together with the 

 chloride, proving that this salt is at least partially decom- 

 posed. 



In the spectroscope the chloride exhibits the blue line with 

 the greatest intensity ; but owing to the volatility of this salt 

 the line is only seen for a very short time. If, however, a 

 small quantity of the oxide be brought into a small platinum 

 spoon and moistened with hydrochloric acid, the blue line is 

 seen on placing the spoon in the flame; and although the line 

 does not appear quite so brightly as when obtained according to 

 the former method, it remains visible for a much longer time; 

 indeed, by moistening the spoon with fresh hydrochloric acid, 

 the experiment may be repeated many times without more oxide 

 being needed. 



The hydrochloric acid solution of the reduced metal, treated 

 with ammonia and sulphide of ammonium, gave a greyish-brown 

 precipitate. Further investigations with larger quantities of the 

 purified substance must, however, decide whether this is the 

 true colour of sulphide of indium, or whether it is due to traces 

 of impurities. 



The mode of purification of the oxide of indium is readily 

 understood from the above reactions. The original solution is 

 treated first with sulphuretted hydrogen, the oxide of indium is 

 then precipitated in the filtrate by ammonia, redissolved and 



