422

ELEMENTS OF MATERIA MEDICA.

of iron, metallic gold in the finely divided state, by protochloride of tin,a dirty purple precipitate (the purple powder of Cassius), and by protoni-trate of mercury, a black precipitate : borax which has been touched withit acquires a pink or rose colour when fused with the blowpipe.

Physiological Effects. —Gold, like other metals, has been frequentlysupposed to be inert while it retains its metallic condition, but in this aswell as in some other instances the accuracy of the assumption has beendenied. Both Chrestien {Sur un Nouv. Remede dans le Traitm. des Mai.Vtn. Paris , 1811) and Niel ( Rech. et Observ. sur les Effets des Prep. d’Or,Paris , 1821), as well as other writers, assert that finely divided metallicgold ( pulvis auri) produces the same constitutional effects as those causedby the various preparations of this metal, but in a milder degree, while itexcites little or no local irritation. It is said to promote the secretionsof the skin, kidneys, and salivary glands.

Uses. —It has been employed as an antivenereal and antiscrofulousremedy by Chrestien, Niel, and others, with considerable success. It issaid to be preferable to the other preparations of this metal in delicateand nervous subjects, females, and infants. Gold leaf ( aurum foliatum seulamellatum) is used by dentists for filling decayed teeth, and formerly byapothecaries for covering pills {ad inaurandas seu obducendas pilulas.)

Administration. —It has been administered internally in doses offrom a quarter of a grain to a grain three or four times a day. Chrestienused it by way of friction on the tongue and gums. Niel employed itendermically (that is, applied it to the skin deprived of the epidermis) in theform of ointment composed of one grain of gold and thirty grains of lard.

Pulvis Auri (Fr. Cod.) is prepared by rubbing leaf gold {aurum inlaminas exilissimas complanatunt) with sulphate of potash, sifting andwashing with boiling water to remove the sulphate: or by adding proto-sulphate of iron to chloride of gold, and washing the precipitate, first withwater, then with dilute nitric acid.

Au ri Terchlo'ridum. — Terchlo'ride of Gold.

Preparation. —In the French Codex this is ordered to be prepared bydissolving, with the aid of heat, one part of gold in three parts of nitro-hydrocliloric acid. The solution is to be evaporated until vapours ofchlorine begin to be disengaged, and then allowed to crystallize.

Properties and Composition. —Chloride of gold is in the form ofsmall crystalline needles, of an orange-red colour, inodorous, and hav-ing a strong, styptic, disagreeable taste. It is deliquescent, on whichaccount it should be preserved in a well-stoppered bottle : it is soluble inwater, alcohol, and ether. When heated it evolves chlorine, and is con-verted, first into protochloride, and then into metallic gold, which is leftin the spongy state. It reddens litmus, stains the cuticle purple, isreduced by many metals (as iron, copper, tin, zinc, &c.), by several ofthe non-metallic elementary substances (as phosphorus), by some metallicsalts (as protosulphate of iron), and by many organic bodies (as charcoal,sugar, gum, gallic acid, extractive, &c.), all of which, therefore, areincompatible with it. Nitrate of silver occasions a precipitate of chlorideof silver and oxide of gold : hydrochloric acid removes the latter.—(Forother characteristics, vide p. 422). Tercliloride of gold consists of 1 eq.gold = 200 + 3 eqs. chlorine, 108. The before-mentioned crystals also