Cadmium oxide, CdO, is a brown powder of specific gravity 6.5, which can be prepared by heating the metal in air or in oxygen; or by ignition of the nitrate or carbonate; by heating the metal to a white heat in a current of oxygen it is obtained as a dark red crystalline sublimate.
It may be condensed to a dark red liquid which is decomposed by moist air into chromic acid and chromic fluoride.
It forms a yellowishwhite deliquescent mass, which melts on heating, and at a sufficiently high temperature it yields a dark red liquid.
Silver chromate, Ag2Cr04, is a dark red amorphous powder obtained when silver nitrate is precipitated by an alkaline chromate.
The scale preparations of iron, so called because they are dried to form scales, are three in number, the base of all being ferric hydrate: (a) Ferrum tartaratum, dark red scales, soluble in water.
It crystallizes in dark red octahedra which are almost insoluble in cold water.
The free acid forms dark red deliquescent crystals and is obtained by decomposing the silver salt with hydrochloric acid, or the barium salt with dilute sulphuric acid.
The hexachloride, WC1 6, is obtained by heating the metal in a current of dry chlorine in the absence of oxygen or moisture, otherwise some oxychloride is formed; a sublimate of dark violet crystals appear at first, but as the hexachloride increases in quantity it collects as a very dark red liquid.
The leading silver minerals are native silver; argentite or silver glance, Ag 2 S, usually containing small amounts of lead, copper and tin; dyscrasite or antimonial silver, Ag 2 Sb to Ag,3Sb, an isomorphous mixture of silver and antimony; proustite or light red silver ore, Ag 3 AsS 3; pyrargyrite or dark red silver ore, Ag 3 SbS 3; stephanite, Ag 5 SbS 4; miargyrite, AgSbS2; stromeyerite, CuAgS; polybasite, 9(Cu 2 S,Ag 2 S) (Sb 2 S 3, As 2 S 3); cerargyrite or horn silver, AgCI; bromite or bromargyrite, AgBr; embolite, Ag(C1,Br); iodite or iodargyrite, AgI.
When kept for some time in sealed tubes it changes to a yellowish liquid, from which a yellow flocculent substance gradually separates, and finally it suddenly solidifies to a dark red mass, which appears to be a polymeric form.