Page:The New International Encyclopædia 1st ed. v. 18.djvu/223

* SILVER. 1T9 SILVES. tained in solution in the form of a chloride are: the Augustiu process, using brine as a solvent and metallic copper as a precipitant; the I'atera process, where sodium tliiosulphate, and the Kiss process, where calcium thiosulphate is the solvent. In the Russell process the silver as metal or sulphide is brought into solution by sodium- copper thiosulpliate. and in the Zicrvogcl process the silver is converted into a sulphate and dis- solved in hot water. The Aiiguxliii process is now rarely practiced and need not be mentioned further. The Patera process is used in Mexico and to some extent in the United States. As car- ried out in the best mills in the United States the process is brielly as follows: The ore is crushed, dried, and roasted with salt in furnaces. The roasted ore is first treated with water in large vats in order to wasli out certain salts of the base metals which are soluble in water. After the water is drawn oH' the vats are filled with sodium thiosulphate solution, which dissolves the silver chloride. The liquor is then run into other tanks for precipitation. If there is lead in the liquor this is first precipitated by adding sodium carbonate, and the remaining liquor drawn into other vats. Here the silver is precipitated by adding sodium sulphide. The precipitate is then drawn off and pressed in filter presses to extract the entrained liquor, when it is dried and cupelled with a lead bath to secure the metallic silver. In the Kiss process a solution of calcium thio- sulpliate is used for extracting the ores after a ehloridizing roasting, the silver being precipi- tated from the liquors by calcium sulphide. In the Russell process the silver present in the ore as metal or sulphides is dissolved bv a solution of sodium-copper thiosulphate and precipitated by a solution of sodium sulphide. The Zierrogel process is used in treating copper ores contain- ing silver. By careful roasting the silver in such ores is converted into silver sulphate, and this is dissolved out by treating the roasted ore with hot water. From this solution the silver is precipitated by metallic copper. Electkolytic Process. The electrolytic proc- ess is used only to separate the silver from lead- silver and zinc-silver allovs produced by the dry process, and is inferior to the zinc process of desilveriiation previouijly described. It has, therefore, not come into extensive use. The silver alloy is remelted and cast into plates which are used as anodes with sheet-brass plates as cath- odes. The electrolyte is a solution of lead sulphate in sodium acetate. Bibliography. Egleston, The Metallurrii/ of Silver, Gold, and Mercjtry in the United States (New York, 1887-90) ; Collins, The Metal- hh-fly of Lead and Silver (London, 1809-1901) ; Eissler, The Metallurgy of Argentiferous Lead (ib., 1891): Hofman, The Metallnrgy of Lead and the Desilvcri::ation of Base Bullion (New York. 1809) ; Wilson. Ci/am'de Processes for Gold and Silrer Ores (ib.. 1896) ;, id.. The Chlori- nation Process (ib., 1897). SILVER^ Free Coin age of. See Bimetallism. SILVER, IVIemcal Uses of. IMetallic silver is not used as a therapeutic agent, but is em- ployed in surgery in the form of wire for sutur- ing wounds and uniting bone fragments. The silver salts of the materia medica are the nitrate, the oxide, and the iodide. Nitrate of sHver has already been partly considered under the title Li.NAK t'ALsric (q.v.J. t^xtcrnally the silver preparations are astringent, stimulating, and hemostatic; in concentrated solution, cau.stic. Of late years a number of compounds of silver and albumen or nuclcin have been made, w'ith the ob- ject of eliminating the irritant properties of sil- ver nitrate while preserving its alterative and tonic qualities. Argyrol and protargol are repre- sentatives of this class, and are largely replacing the nitrate. These are useful in catarrhal con- ditions or specific inflammations of the mucous membrane of the eye, nose, throat, middle ear, urethra, and vagina, and are emploj'ed as topical applications in conjunctivitis, chronic pharyngi- tis, or laryngitis, in gleet (chronic urethritis), and inllammation of the vagina or cervix uteri. Internally silver salts, principally the nitrate, are useful in gastric ulcer in combination with hyoscyanius as a pill. In chronic ulceration of the colon from dysentery, keratin-coated pills (which are not dissolved in the stomach) may be given, and high injections of weak silver solu- tion thrown into the bowel. Nitrate of silver is a remedy of value in idiopathic or non-syphilitic spinal sclerosis, but it is often ineffectual. It has been used in various other nervoits diseases, such as chorea and epilepsy, but does little good. When the silver salts are given for an}' length of time they are deposited in the tissues, giving rise to a peculiar pale slate-blue color of the skin. Argi/ria. as this condition is called, is not very amenable to treatment, but potassium iodide may help to eliminate the substance from the tissues. SILVER-BELL TREE. See Snow-Drop Tree. SILVERFIN. A minnow {Notropis Whip- plci), common in clear streams of the northern interior of the United States. It is four inches long, and leaden silvery in color, with a large black spot on the upper posterior part of the dorsal fin. See Plate of Dace and Minnows. SILVER-FISH, or Fi.sh-3Ioth. See Bkistle- TAIL. SILVER GRAYS. A name given in New York to that faction of the Whig Party corre- sponding to the Cotton Whigs of Massachusetts, which considered the slavery question settled by the compromise of 18.50. SILVERING GLASjj. See Mirror. SILVER LACE. See C4old Lace. SILVERSIDE, or Sand-Smelt. A slender fish of the family Atherinidfe. which seldom ex- ceed six inches in length. The silversides jjo in large schools in the tropical and temiierate shore- waters. A few are found in fresh waters. All have a silver band along the side, whejjce their name. When large enough they are highly es- teemed as food. See Plate of Mullets. d Al- lies. SILVER WEDDING. See Wedding Anni- versaries. SILVES, sel'vesh. A town of Portugal, on the Silves River, 115 miles southeast of Lisbon. Cork-cutting is its main industry. In the eleventh century l^ilves was the capital of the Moorish kingdom of Algarve and was captured by the