1. A permanent photographic picture or print in platinum black.
2. The process by which such pictures are produced.
(Plat"i*nous) a. (Chem.) Of, pertaining to, or containing, platinum; used specifically to
designate those compounds in which the element has a lower valence, as contrasted with the platinic
compounds; as, platinous chloride
Platinum black (Chem.), a soft, dull black powder, consisting of finely divided metallic platinum obtained
by reduction and precipitation from its solutions. It absorbs oxygen to a high degree, and is employed
as an oxidizer. Platinum lamp (Elec.), a kind of incandescent lamp of which the luminous medium
is platinum. See under Incandescent. Platinum metals (Chem.), the group of metallic elements
which in their chemical and physical properties resemble platinum. These consist of the light platinum
group, viz., rhodium, ruthenium, and palladium, whose specific gravities are about 12; and the heavy
platinum group, viz., osmium, iridium, and platinum, whose specific gravities are over 21. Platinum
sponge (Chem.), metallic platinum in a gray, porous, spongy form, obtained by reducing the double
chloride of platinum and ammonium. It absorbs oxygen, hydrogen, and certain other gases, to a high
degree, and is employed as an agent in oxidizing.
(Plat"i*num) n. [NL., fr. Sp. platina, from plata silver, LL. plata a thin plate of metal. See
Plate, and cf. Platina.] (Chem.) A metallic element, intermediate in value between silver and gold,
occurring native or alloyed with other metals, also as the platinum arsenide It is heavy tin-white metal
which is ductile and malleable, but very infusible, and characterized by its resistance to strong chemical
reagents. It is used for crucibles, for stills for sulphuric acid, rarely for coin, and in the form of foil and
wire for many purposes. Specific gravity 21.5. Atomic weight 194.3. Symbol Pt. Formerly called platina.
(Plat"i*tude) n. [F., from plat flat. See Plate.]
1. The quality or state of being flat, thin, or insipid; flat commonness; triteness; staleness of ideas of language.
To hammer one golden grain of wit into a sheet of infinite platitude.Motley.
2. A thought or remark which is flat, dull, trite, or weak; a truism; a commonplace.
(Plat`i*tu`di*na"ri*an) n. One addicted to uttering platitudes, or stale and insipid truisms.
"A political platitudinarian." G. Eliot.
(Plat`i*tu"di*nize) v. i. To utter platitudes or truisms.
(Plat`i*tu"di*nous) a. Abounding in platitudes; of the nature of platitudes; uttering platitudes.
(Plat"ly) a. Flatly. See Plat, a. [Obs.]
(Plat"ness), n. Flatness. [Obs.] Palsgrave.
(Pla*tom"e*ter) n. [Gr. flat + -meter.] See Planimeter.
(Pla*ton"ic Pla*ton"ic*al) a. [L. Platonicus, Gr. : cf. F. platonique.]
1. Of or pertaining to Plato, or his philosophy, school, or opinions.
2. Pure, passionless; nonsexual; philosophical.
Platonic bodies, the five regular geometrical solids; namely, the tetrahedron, hexahedron or cube, octahedron,
dodecahedron, and icosahedron. Platonic love, a pure, spiritual affection, subsisting between persons