OXIDES. 293 



hydrates may be obtained by precipitating solutions 

 of their salts with potassa, soda, or ammonia. The hy- 

 drate of the oxide of copper, and peroxide of iron, 

 may serve as examples. The former is blue and the 

 latter a reddish brown. 



734. The hydrated oxides of nickel, co- 

 ted oxid dis- bait, tin and copper, produced from soliu 

 soiveinam- tion o f these meta i s b y t h e addition of 



moma ? J 



ammonia, are again re-dissolved in an 

 excess of ammonia. That of copper dissolves with a 

 beautiful blue color, which is conclusive evidence that 

 the liquid with which the experiment is made contains 

 copper in solution. 



735. USES. Oxide of magnesium or 



Give the uses 



of some of the magnesia, and mercury, among others, are 

 oxide* ? used in medicine, and white oxide of zinc, 



as a paint. Litharge or protoxide of lead is employed 

 in making flint-glass and varnishes. Red lead is used 

 as a paint. Oxide of bismuth is employed as a cos- 

 metic. 



736. Oxide of manganese is used to 



C lor laSS U1 ' le aild Vi let Oxide f 



glass by the cobalt, to color it blue : oxides of copper, 



oxide of man- 



ganese, cobalt, and chromium, to impart a green color to 

 C dx pC &c 7 n ' lass and P orcelaitl j peroxide of iron, 

 to give it a yellowish red, and protoxide, a 

 bottle-green. Sub-oxide of copper gives to glass a 

 beautiful ruby red. Silver and antimony are employed 

 to produce different shades of yellow and orange. Vi- 

 olet and rose color, are obtained by means of the purple 

 of cassius, a beautiful purple precipitate, containing 



