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To Clean Coppers and Tins

the remainder with distilled water.

These are cleaned with a mixture of rotten add dilute hydrochloric acid, by drops, as stone, soft soap, and oil of turpentine, mixed long as it occasions a precipitate, and filter to the consistency of stiff putty. The stone the whole, after being moderately heated, should be powdered very fine and sifted; and upon a small paper filter. Treat the filtered a quantity of the mixture may be made liquid with a stream of sulphuretted hydrosufficient to last for a long while. The articles should 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. gen; collect the black precipitate, wash it, and digest it in strong nitric acid; when entirely dissolved , precipitate the lead with sulphuric acid dropped in it, evaporate the precipitate to dryness, the excess of sulphuric acid being expelled by a rather strong heat applied towards the end. should be washed, dried, and exposed to slight The dry mass ignition in a porcelain crucible. The resulting dry sulphate is equal to .68 per cent. of its weight in lead. 3256. To Find the Percentage of Lead in Lead Ores. This can be done by applying the test in the wet way (see No.

Lead.se Lead is only prepared on the 3255), and multiplying the weight of the pro large scale. It is usually extracted from duct obtained in grains by .68. It may also galena, a natural sulphuret of lead, by roast- be found in the dry way, as follows Plunge duct obtained in grains by .68. It may also , a natural sulphuret of lead, by roast- be found in the dry way, as follows: Plunge ing the ore in a reverberatory furnace, and a conical wrought iron crucible into a blast afterwards smelting it along with coal and furnace, raised to as high a heat as possible; lime. Its specific gravity, in a state of abso- when the crucible has become of a dull red lute purity, is 11.38 to 11.44, but ordinary heat, introduce into it 1000 grains galena lead seldom exceeds 11.35. It melts at about (lead ore) reduced to powder, and stir it gently with a piece of stiff iron wire flattened at the end. This wire must never be suffered to get red hot. To prevent the ore from adhering, after 3 or 4 minutes, cover up the crucible; and when at a full cherry-red heat, add 2 6120 Fahr., and when very slowly cooled, crystallizes in octohedrons. It is malleable and ductile, but devoid of elasticity. Lead is not dissolved by muriatic, sulphuric, or the vegetable acids, unless by free contact with air, and then very slowly: but nitric acid or 3 spoonfuls of reducing flux (see No. 3464), rapidly oxidizes it, forming a solution of ni- and bring to a full white heat; in 12 to 15 trate of lead. Pure water, put into a leaden minutes, after having scraped down the vessel, and exposed to the air, soon corrodes scoria, etc., from the sides of the crucible, it, and dissolves the newly-formed oxide; but into the melted mass, the crucible should be river and spring water exert no such influ- removed from the fire, and the contents tilted ence, the carbonates and sulphates in such into a small brass mould, observing to run water destroying its solvent power. may be alloyed with most metals, except latter back with a piece of green wood. The Lead out the metal free from scoria, by raking the those which differ greatly from it in specific scoria is then those which differ greatly from it in specific gravity and melting point. It has a strong spoonful of flux, and this second reduction affinity for gold and silver, and is therefore added to the first. The weight in grains of employed to separate those metals, by cúpel- the metal obtained, divided by 10, gives the lation, from other metals and minerals. 3254. Cautions on the Use of Lead ore. percentage of metallic lead in the sample of for Cisterns, &c. Ordinary water, which abounds in mineral salts, may be safely kept 1 ounce sugar of lead (acetate of lead) in 1 3257. Το Make a Lead Tree. Dissolve in leaden cisterns; but distilled and rain pints distilled water ; add a few drops of water, and water that contains scarcely any saline matter water, and water that contains scarcely any speedily corrode, and dissolve a portion of lead, when kept in vessels of that acetic acid; place the liquid in a clear white glass bottle and suspend a piece of zinc in it by means of a fine thread secured to the cork.

IRON. the to carbonize the oil. In this way the cast ron. Iron is only prepared on large scale. It is obtained by smelting iron absorbs oxygen at the moment the oil is the ore along with coke and a flux (either face a thin coat of brown oxide, which ada flux (either decomposed, and there is formed at the surlimestone or clay). The crude iron thus ob- face a thin coat of brown oxide, which adtained is run into moulds, and then consti- heres very strongly to the metal, and will tutes cast iron or pig iron. By the subse- admit of a high polish, giving it quite the apquent process of refining, (puddling , welding,) pearance of the finest bronze. it is converted into soft iron or wrought iron.