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 cadmium are susceptible of solution, but the heat required is a high one.  This is best done upon charcoal.

The perchloride of mercury sublimes undecomposed in the bulb, previously undergoing fusion.

The protochloride of mercury likewise sublimes, but it does not undergo fusion first, as is the case with the corrosive sublimate.

The ammoniacal salts all are susceptible of sublimation, which they do without leaving a residue.  There are, however, several which contain fixed acids, which latter are left in the bulb.  This is particularly the case with the phosphates and borates.  A piece of red litmus paper will readily detect the escaping ammonia, while its odor will indicate its presence with great certainty.  The halogen compounds of mercury, we should have mentioned, also sublime, the red iodide giving a yellow sublimate.

The bulb is also a convenient little instrument for the purpose of heating those substances which phosphoresce, and likewise those salts that decrepitate.