gold

A metallic element known from the earliest times. It is a soft, bright yellow, lustrous substance, and is exceedingly tenacious, malleable, and ductile. It is not oxidized at any temperature by contact with water or oxygen, and is not attacked by any acids except selenic acid and a mixture which, like nitro hydrochloric acid, contains nascent chlorin. It is also attacked by alkalis. Symbol, Au (from aurum); atomic weight, 196.2. None of the salts of gold are of great therapeutic importance. Siguier's g. salt. See gold and sodium chlorid. fulminating g. A compound of g. and ammonium, Au20s(NH3)4. It was formerly employed as a diaphoretic. It is a greenish or brownish powder, exploding readily and with great violence on either heating or percu ion, g. and sodium chlorid. Chrestien's (or Figuier's) g. salt, NaAu- CU + 2H2O, forming bright yellow prismatic crystals, of saline taste, readily soluble in water. Its use has been suggested in tertiary syphilis, g. bromid. A compound of g. and bromin. See g. tri bromid. g. chlorid. A compound of g. and chlorin. See g. tri chlorid, which is the g. chlorid of the pharmacopeias, g.-foil. See g.- leaf. g. iodid. A compound of g. and iodin. See g. tri-iodid, which is the g. iodid used in medicine, g.-leaf. Metallic g. in the form of very thin laminae. g. mono bromid. Aurous bromid, AuBr, a greenish yellow, micaceous powder, insoluble in water, g. mono chlorid. Aurous chlorid, AuCl, an unstable yellowish powder, g. mono-iodid. Aurous iodid. Aul, a lemon yellow crystalline body, which turns green on exposure to the air, at the same time decomposing with the deposition of metallic gold. g. perchloric!. See g. tri chlorid. g. sponge. A porous and spongy form of metallic g. used by dentists; obtained by adding oxalic acid to a solution of g. chlorid, heating, washing the deposit with hot water, drying on filtering paper, and then heating below redne till the particles cohere slightly, g. terchlorid. See g. tri chlorid. g. thread. See Coptis. g. tri bromid. Auric bromid; a black crystalline ma , AuBr3, soluble in water. It forms with the bromin compounds of other metals double bromids called bromaurates, used like the mono bromid. g. tri chlorid. Auric chlorid, AuCk; formed by di olving g. in nitro hydrochloric acid, or by the action of chlorin on g.-leaf. The anhydrous salts form reddish crystals. When combined with two molecules of water, AUCI3 + 2H2O, it forms deliquescent and efflorescent, dark yellowish red crystals, the chlorure d'or combination of the Fr. with Cod. G. tri chlorid occurs in other chlorids, forming the chloraitrates. g. tri cyanid. Auric cyanid, Au(CN)3,- an unstable substance, forming large crystalline tablets readily soluble in water and alcohol. According to some writers, it occurs only in combination with hydrocyanic acid and other cyanids. g. tri-iodid. Auric oxid (or an hydrid), AU2O3, sometimes improperly called auric acid; a blackish brown powder occasionally used in medicine.