CHEMICAL PROPERTIES OF MINERALS. 123
ignited
with solution of cobalt, it assumes a fine blue color. It is thrown
down by potassa or soda as a white voluminous precipitate, which in
excess of the alkali is easily and completely soluble, but is again
precipitated by muriate of ammonia. Carbonate of ammonia also produces
a precipitate which is not soluble in excess.
Glucina, Yttria, Zirconia, and Thorina are
not properly distinguished by blowpipe tests, though the minerals in
which they occur are well marked in this way. In solution, glucina acts
with potassa like alumina; but the precipitate with carbonate of
ammonia.is again soluble, with excess of the alkali, and the two earths
may thus be separated. Yttria is precipitated by potassa, but is not
again dissolved by excess of the alkali. With carbonate of ammonia it
acts like glucina. It must be observed, however, that the substance
formerly named yttria is now considered a mixture of this earth with
the oxides of erbium, terbium, and lanthanium. Zirconia acts with
potassa like yttria, and with carbonate of ammonia like glucina.
Concentrated sulphate of potassa throws down a double salt of zirconia
and potassa, which is very little soluble in pure water.
III.----THE METALS.
Arsenic and
its sulphuret on charcoal yield fumes, with a smell like garlic, and
sublime in the closed tube. The greater number of alloys of arsenic in
the reducing flame leave a white deposit on, the charcoal; or, where it
is in larger proportion, give out grayish-white fumes with a smell of
garlic. Some alloys also yield metallie arsenic in the closed tube. In
the open tube all of them yield arse-nious acid, and those containing
sulphur also sulphurous fumes. Many arsenic acid salts emit evident
odors of arsenic when heated on charcoal with soda; and some sub-
