CHEMICAL PROPERTIES OF MINERALS. 127
be separated from each other by heat. Only the Osmium-indium strongly
heated in the closed tube with saltpetre is decomposed, forming osmium
acid, known from its pecu- liar pungent odor. The usual mixture of
platinum grains is soluble in nitro-chloric acid, leaving
osmium-iridium. From this solution the platinum is thrown down
by sal-ammonia as a double chloride of platinum and ammonium. From the
solution evaporated, and again diluted, with cyanide of mercury, the palladium separates as cyanide of palladium. The rhodium may be separated by its property of combining with fused bisulphate of potassa, which is not the case with platinum or iridium.
Cerium, when
no iron-oxide is present, produces, with borax and salt of phosphorus,
in the oxidating flame, a red. or dark-yellow glass, which becomes very
pale when cold, and colorless in the reducing flame. Lanthanium oxide forms a white colorless glass; didymium, a dark amethystine glass.
Iron, the
peroxide and hydrated peroxide, become black . and magnetic before the
blowpipe, and form, with borax or salt of phosphorus, in the oxidating
flame, a dark-red glass, becoming bright-yellow when cold; and in the
reducing flame, especially on adding tin, an olive-green or
mountain-green glass. The peroxide colors a bead of horax containing
copper oxide, bluish-green ; the protoxide produces red spots. Salts of
protoxide of iron form a green solution, from which potassa or ammonia
throws down the protoxide as a hydrate, which is first white, then
dirty-green, and finally yellowish-brown. Carbonate of lime produces no
precipitate. The salts of the peroxide, on the other hand, form yellow
solutions from which the peroxide is thrown down by potassa or ammonia
as a flaky-brown hydrate. Carbonate of lime also causes a precipitate.
• Chromium forms, with borax or salt of phosphorus, a
