Ores, roasting

The chlorination process, introduced in Europe in 1843, roasted ore with chlorides, followed by a hot brine leach and subsequent precipitation of the silver on copper. In 1887 it was discovered that gold and silver can be recovered by sodium cyanide, and this process displaced the dangerous chlorination process. By 1907 the cyanide process, where a cyanide solution is mixed with 2inc dust to precipitate the silver, was universally in use. 

Anhydrous zinc chloride can be made from the reaction of the metal with chlorine or hydrogen chloride. It is usually made commercially by the reaction of aqueous hydrochloric acid with scrap zinc materials or roasted ore, ie, cmde zinc oxide. The solution is purified in various ways depending upon the impurities present. For example, iron and manganese precipitate after partial neutralization with zinc oxide or other alkah and oxidation with chlorine or sodium hypochlorite. Heavy metals are removed with zinc powder. The solution is concentrated by boiling, and hydrochloric acid is added to prevent the formation of basic chlorides. Zinc chloride is usually sold as a 47.4 wt % (sp gr 1.53) solution, but is also produced in soHd form by further evaporation until, upon cooling, an almost anhydrous salt crystallizes. The soHd is sometimes sold in fused form. 

Ziac sulfate was made by 15 companies ia 1980 from secondary materials (93%) and from roasted ore, ie, ziac oxide (7%). The ziaciferous material reacts with sulfuric acid to form a solution, which is purified. After filtration, the solution is heated to evaporation and heptahydrate crystals are separated. It is sometimes sold ia this form but usually as the monohydrate [7446-19-7] which is made by dehydration at ca 100°C. Very pure ziac sulfate solution is made ia the manufacture of the pigment Hthopone [1345-05-7] ZnS-BaSO, and of ziac by electrowinning (see ZiNC AND ZINC ALLOYS). 

Alternatively, the carbon reduction can be replaced by reduction of the roasted ore with fresh galena ... 

Abbrand, m. burnt or roasted ore waste (in forging, etc.) loss by burning, consumption calcination. 

Rost-erz, n. roasted ore, calcined ore. -er-zeugnis, n. product of roasting, of calcining, etc. (see rdsten). 

Silver was formerly extracted by cyanide solution of Ag2S, the resulting Ag(CN)2 being treated with zinc to afford the metal roasted ores could also be extracted with mercury to give silver amalgam. Presently much silver is extracted by workup of the anode slime from the preparation of non-ferrous metals (Pb, Cu) pure silver is obtained by electrolysis of AgN03. 

Fe203 iron oxide natural, calcinated or roasted ore... 

Then the roasted ore is combined with sand, powdered limestone, and some unroasted ore (containing copper(II) sulfide), and heated at 1,100°C in a reverberatory furnace. Copper(II) sulfide is reduced to copper(I) sulfide. Calcium carbonate and silica react at this temperature to form calcium silicate, CaSiOs The liquid melt of CaSiOs dissolves iron(II) oxide forming a molten slag of mixed silicate ... 

Several leaching processes are known. One such process, known as the Patera process, developed in the mid 19 century, involves roasting ore with sodium chloride foUowed by leaching with sodium thiosulfate solution. Silver... 

Vanadium usually is recovered from its ores by one of two processes, (1) leaching raw mineral with hot dilute sulfuric acid, and (2) roasting ore with common salt to convert vanadium into water soluble sodium vanadates. In the sulfuric acid leaching process, vanadium is extracted from acid leach liquors by solvent extraction with an aliphatic amine or an alkyl phosphoric acid in kerosene. The organic solvent extract then is treated with an aqueous solution of ammonia in the presence of ammonium chloride to convert vanadium into ammonium metavanadate. Alternatively, the organic extract is treated with dilute sulfuric acid or an aqueous solution of soda ash under controlled conditions of pH. Vanadium is precipitated from this solution as a red cake of sodium polyvanadate. 

Earlier in this chapter, we described the preparation of S02 from burning fossil fuels and roasting ores as sources of S02 that are replacing the burning of sulfur. 

The process patented by Jumau1 involves the extraction of the roasted ore with an ammoniacal solution of ammonium sulphate or sulphite. Sulphurous acid reacts with the solution thus formed, precipitating either cuprous sulphite or cupro-cupric sulphite ... 

VENA TRANSVERSA — A Cross-way. A Crossing Vein VENA USTA — Roasted Ore. 

The chief minerals of arsenic include orpiment, As S (from Latin anripigmentum, yellow pigment), realgar, AsS (a red substance), arseno-lite, As Op, and arsenopyrite, FeAsS. Arsenic trioxide (arsenious oxide) is obtained by roasting ores of arsenic. The element is made by reducing the trioxide with carbon or by heating arsenopyrite ... 

The concentrate or the rich sulfide ore is then roasted in a furnace through wiiich air is passing. This removes some of the sulfur as sulfur dioxide, and leaves a mixture of Cir.S, FeO, SiO, and other substances. This roasted ore is then mixed with limestone to serve as a flux, and is heated in a furnace. The iron oxide and silica combine with the limestone to form a slag, and the cuprous sulfide melts and can be drawn off. This impure cuprous sulfide is called matte. It is then reduced by blearing air tlirough the molten material ... 

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