Platinum

(platf -in-um) [Sp., platina, dim. of plat a, silver]. A silver white metal occurring native or alloyed with other metals; atomic weight 195; sp. gr. 21.5; quantivalence II and IV; symbol Pt. It is fusible only at very high temperatures, and is insoluble in all acids except aqua regia. On account of these properties it is extensively used for chemic apparatus — crucibles, foils, wire, etc.; it is also employed as a reagent. P. occurs, aside from its ordinary metallic form, as a spongy ma (spongy P.) and as a fine PLATY metallic powder (P. -black), which is capable of condensing a great deal of oxygen, and hence acts as a powerful oxidizing agent. P. forms two sets of compounds, a platinous series, in which it acts as a dyad, and a platinic series, in which it acts as a tetrad. Platinic chlorid, PtCl4, is used as a reagent to detect pota ium and ammonium; also in syphilis, in doses of gr. |— ^ (0.008-0.03). 504