[′sōd·ē·əm ‚klȯr·ō′plat·ən‚āt] (inorganic chemistry) Na2PtCl6·4H2O A yellow powder, soluble in alcohol and water; used for zinc etching, indelible ink, plating, and mirrors, and in photography and medicine. Also known as platinic sodium chloride; platinum sodium chloride; sodium platinichloride.