platinous inum as a (plat'in-us). bivalent radicle.Containing plat platinum (plat'in-um)

A metallic element. It is a soft, ductile, and very malleable white metal, which is infusible at all temperatures ordinarily obtainable, but melts in the oxyhydrogen flame. It is very heavy, its sp. gr. being 21.5. Spongy p. is a porous ma obtained by heating chlorid of p. and ammonium. P. black is very finely divided metallic p., forming a soft black powder. P. has a marked capacity for absorbing hydrogen and for condensing oxygen upon its surface, and this property is especially pronounced in the case of the two varieties just described. P. is not oxidizable by exposure to air, oxygen, or water. It is not attacked by nitric acid, but is di olved by aqua reg is. It is attacked by the alkalis and alkaline cyanids and by pota ium nitrate. It forms with several metals alloys which are fusible at temperatures much below its own melting point. In composition it acts partly as a dyad, forming platinous salts, partly as a tetrad, forming platinic salts. Symbol, Pt; atomic weight, 195.