CHROMIUM. 



245 



formed upon the steel under the influence of heat. The 

 tint is different, according to the thickness of the 

 film. All these colors may be seen by heating a knit- 

 ting-needle in the flame of a spirit lamp. Where it is 

 hottest it becomes blue, and this color shades off into 

 pale yellow on either side, like the colors of the solar 

 spectrum. 



Chromium 



CHROMIUM. 

 607. DESCRIPTION. Chromium is a grey 



. * 



description, metal, not readily tarnished, and so hard 



P of"so!nts, aS t0 SCratch g lass ' Jt is of no use in the 



and uses? arts in the metallic form. It is found in 

 combination with iron, as chromic iron, and also in 

 beautiful Crystals, as red chromate of lead. It may be 

 prepared from its oxide, like iron, by heating with 

 charcoal. Its compounds are much used as paints. 

 Chrome green and chrome yellow are among the 

 number. Its proper solvents are the same as those of 

 iron. The solutions of this metal are green. 



COBALT 



608. DESCRIPTION. Cobalt is another 

 grey metal, tarnishing but slightly in the 

 air. It is somewhat malleable. It is found 

 combined with arsenic, as arsenical cobalt, 

 and in some other minerals. As metal, 

 it is without useful application in the arts. It may 

 be produced like iron, by heating with charcoal, 



Cobalt de- 

 scription, pro- 

 duction, oc- 

 currence, sol- 

 vents, and 

 uses ? 



