ow heat. Alloys of arsenic are converted
into basic arseniates of metal oxides, while surplus arsenic is
converted into arsenious acid, which sublimes on the tube. If too much
arsenic is used for this experiment, a dark-brown incrustation will
sublime upon the sides of the tube which will give an alliaceous
smell. If this sublimate should be deposited near the assay, then it
resembles the white sublimate of arsenious acid.

Heated upon charcoal, metallic arsenic is volatilized before it melts,
and incrusts the charcoal in the flame of oxidation as a white deposit
of arsenious acid. This sublimate appears sometimes of a greyish
color, and takes place at some distance from the assay. When heated
slightly with the blowpipe flame, this sublimate is instantly driven
away, and being heated rapidly in the reduction flame, it disappears
with a light blue tinge, while the usual alliaceous or garlic smell
may be discerned.

Arsenious acid sublimes in both glass tubes very readily, as a white
crystalline sublimate. These crystals appear to be regular octahedrons
when observed under the microscope. Upon charcoal it instantly
volatilizes, and when heated, the characteristic garlic smell may be
observed.

Arsenic acid yields, heated strongly in a glass tube closed at one
end, oxygen and arsenious acid, the latter of which sublimes in the
cool portions of the tube. Compounds of arsenic produce, in
consequence of their volatility, no reactions with fluxes. Being
heated upon charcoal with carbonate of soda, they are reduced to
metallic arsenic which may be detected by the alliaceous odor peculiar
to all the arsenic compounds when volatilized.

NINTH GROUP.--COPPER, SILVER, GOLD.

These metals are not volatile, neither are their oxides. They are
reduced to the metallic state, by fusion with carbonate of soda, when
they melt to a metallic grain. The oxides of silver and gold are
reduced _per se_ to the metallic state by ignition. In the reduction
of the oxides of this group, no sublimate is visible upon the
charcoal.

(_a._) _Copper_ (Cu).--This metal occurs in the metallic state, also
as the protoxide, and as oxides combined with acids in different salts
(carbonate of copper as malachite, etc.) The sulphide of copper is the
principal ore of copper occurring in nature. In the metallic state,
copper is of a red color, has great lustre and tenacity, is ductile
and malleable, and crystallizes in octahedrons and cubes. It melts at