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Pyrethrum – Pyroxylic Spirit

Pyrethrum

in botany, a genus of Chrysanthemex.

Pyrheliometer

an instrument invented by Pouillet for measuring the amount of heat radiated from the sun.

Pyrites

an isometric mineral occurring frequently crystallized, also massive, in mammillary forms with fibrous structure, and stalactitic with crystalline surface. Occurs abundantly distributed in rocks of all ages, either as crystals, crystal-grains, or nodules, also in metalliferous veins.

PYROGALLIC ACID

Pyrogallic Acid

in chemistry, pyrogallol, an acid, discovered by Scheele. Extensively used in photography as a reducing agent.

Pyrograph

an apparatus for engraving on wood or leather by means of a red-hot metallic point.

Pyroligneous Acid

impure acetic acid, obtained by the destructive distillation of wood.

Pyrolusite

one of the most important of the ores of manganese. Used in preparing oxygen gas, with which it parts at a red heat; and also in glass making.

Pyrope

in mineralogy, one of the garnet group. Color, a deep-red; transparent. Found associated with serpentines, and in streams in Bohemia. Much used in jewelry.

Pyroscope

an instrument, invented by Leslie, to measure the intensity of heat radiating from a hot body or the frigorific influence of a cold body. The instrument is like a differential thermometer, one ball being covered with thick silver-leaf; the other ball is naked and forms the pyroscope.

Pyrosoma

the sole genus of Pyrosomidæ, a family of Tunicata, with three species. They are brilliantly phosphorescent, and Péron compared them to small incandescent cylinders of iron.

Pyrotechny

in the proper sense, the science which teaches the management and application of fires. In the more popular sense, however, the word chiefly refers to the art of making fireworks. The principal ingredients used are purified saltpeter, sulphur, and charcoal.

Pyroxylic Spirit

WOOD SPIRIT, or WOOD NAPHTHA, a mixture of acetone, methyl-alcohol, acetate of methyl, etc., obtained by the destructive distillation of wood in the manufacture of PYROLIGNEOUS ACID (q. v.). It is of nearly equal value to alcohol in making varnishes, as it dissolves the resins, oils, and other similar substances.

It is used in making METHYLATED SPIRIT (q. v.).