Sentence Examples

  • Ferrous oxide is the usual cause of discoloration.
  • The potassium salt may be prepared by adding potassium cyanide to ferrous sulphate solution, the brown precipitate so formed being then heated with potassium nitrite: 5 KNC + 2 FeSO 4 = 2 K 2 SO 4 + KFe2(NC)5, 2 KFe 2 (NC) 5 + 2 KNO 2 = 2 FeO + 2 K2Fe(NC)5 NO.
  • If the substance does not melt but changes colour, we may have present: zinc oxide - from white to yellow, becoming white on cooling; stannic oxide - white to yellowish brown, dirty white on cooling; lead oxide - from white or yellowish-red to brownish-red, yellow on cooling; bismuth oxide - from white or pale yellow to orange-yellow or reddish-brown, pale yellow on cooling; manganese oxide - from white or yellowish white to dark brown, remaining dark brown on cooling (if it changes on cooling to a bright reddishbrown, it indicates cadmium oxide); copper oxide - from bright blue or green to black; ferrous oxide - from greyish-white to black; ferric oxide - from brownish-red to black, brownish-red on cooling; potassium chromate - yellow to dark orange, fusing at a red heat.
  • The specific gravity of gold obtained by precipitation from solution by ferrous sulphate is from 19.55 to 20.72.
  • The precipitants in use are: ferrous sulphate, charcoal and sulphuretted hydrogen, either alone or mixed with sulphur dioxide; the use of copper and iron sulphides has been suggested, but apparently these substances have achieved no success.