3246. To Separate Copper from its Alloys

3246.     To Separate Copper from its Alloys. Copper may be separated in absolute purity from antimony, arsenic, bismuth, lead, iron, etc., as it exists in bell-metal, brass, bronze, and other commercial alloys, by fusing, for about half an hour, in a crucible, 10 parts of the metal with 1 part each of copper scales (black oxide), and bottle glass. The pure copper is found at the bottom of the crucible, whilst the other metals or impurities are either volatilized or dissolved in the flux.

3247. Copper in Fine Powder

3247.      Copper in Fine Powder. A solution of sulphate of copper is heated to the boiling-point, and precipitated with sublimated zinc. (See No. 30 (Sublimation).) The precipitated copper is then separated from the adherent zinc by diluted sulphuric acid, and dried by exposure to a moderate temperature.

3248. Reduction of Copper in Fine Powder

3248.     Reduction of Copper in Fine Powder. M. Schiff gives the following process for obtaining copper in a state of fine division: A saturated solution of sulphate of copper, together with some crystals of the salt, are introduced into a bottle or flask, and agitated with some granulated zinc. The zinc displaces the copper from its solution, fresh sulphate dissolving as the action goes on, until the whole is exhausted. Heat is disengaged during the operation. The precipitated copper must be washed and dried as rapidly as possible, to prevent oxidation.

3249. Feather-Shot Copper

3249. Feather-Shot Copper. Melted copper, poured in a small stream into cold water. It forms small pieces, with a feathered edge, hence the name. It is used to make solution of copper.

3250. Welding Copper

3250. Welding Copper. A compound of 358 parts phosphate of soda and 124 parts boracic acid is prepared, and is used when the metal is at a dull red heat; the heat is then increased till the metal becomes of a cherry-red color, and the latter is at once hammered. A hammer of wood is recommended for this purpose, as the metal is liable to soften at a high heat; and the hammer should be used cautiously. All scale and carbonaceous matter must be removed from the surface of the copper, as the success of the welding depends on the formation of an easily fusible phosphate of copper, which would be reduced to a phosphide by the presence of carbon.

3251. To Prevent the Corrosion of Copper and Other Metals

3251.    To Prevent the Corrosion of Copper and Other Metals. The best means of preventing corrosion of metals is to dip the articles first into a very dilute nitric acid, immerse them afterwards in linseed oil, and allow the excess of oil to drain off. By this process metals are effectually prevented from rust or oxidation.

3252. To Clean Coppers and Tins

3252.     To Clean Coppers and Tins. These are cleaned with a mixture of rotten stone, soft soap, and oil of turpentine, mixed to the consistency of stiff putty. The stone should be powdered very fine and sifted; and a quantity of the mixture may be made sufficient to last for a long while. The articles 6hould first be washed with hot water, to remove grease. Then a little of the above mixture, mixed with water, should be rubbed over the metal; then rub off briskly, with dry clean rag or leather, and a beautiful polish will be obtained. When tins are much blackened by the fire they should be scoured with soap, water, and fine sand.