ined especially for the
purpose of determining that point.

_Selenium_ will likewise sublime by heat as does sulphur. This is the
case if selenides are present. Selenium gives off the smell of decayed
horse-radish.

When the persalts are heated they are reduced to protosalts, with the
elimination of a part of their acid. This will be indicated by the
blue litmus paper.

If some of the neutral salts containing a volatile acid be present,
they will become decomposed. For instance, the red nitrous acid water
of the nitrates will indicate the decomposition of the salt,
especially if it be the nitrate of a metallic oxide.

If there is an odor of sulphur, then it is quite probable, if no free
sulphur be present, that a hyposulphite is decomposed.

If an oxalate be present, it is decomposed with the evolution of
carbonic oxide, which may be inflamed at the mouth of the tube; but
there are oxalates that give off carbonic acid gas, which, of course,
will not burn. A cyanide will become decomposed and eliminate nitrogen
gas, while the residue is charred. Some cyanides are, however, not
thus decomposed, as the dry cyanides of the earths and alkalies.

There are several oxides of metals which will sublime, and may be thus
examined in the tube. _Arsenious acid_ sublimes with great ease in
minute octohedral crystals. The oxides of tellurium and antimony will
sublime, the latter in minute glittering needles.

There are several metals which will sublime, and may be examined in
the cold portion of the tube. _Mercury_ condenses upon the tube in
minute globules. These often do not present the metallic appearance
until they are disturbed with a glass rod, when they attract each
other, and adhere as small globules. Place in the tube about a grain
of red precipitate of the drug stores and apply heat, when the oxide
will become decomposed, its oxygen will escape while the vaporized
mercury will condense upon the cold portion of the tube, and may there
be examined with a magnifying glass.

_Arsenic_, when vaporized, may be known by its peculiar alliaceous
odor. Arsenic is vaporized from its metallic state, and likewise from
its alloys. Several compounds which contain arsenic will also sublime,
such as the arsenical cobalt. Place in the bulb a small piece of
arsenical cobalt or "fly-stone," and apply heat. The sulphide of
arsenic will first rise, but soon the arsenic will adhere to the sides
of the tube.

The metals tellurium and ca