Silver refining

Silber gare,/. silver refining, -gefaait, m. silver content, -gewinnung, /. extraction of silver, -glanz, m. silvery luster silver glance, argentite. 

Silber-rhodanid, n. silver thiocyanate, -solbe, /. Pharm.) colloid silver ointment, -salpeter, m. silver nitrate, -salz, n. silver salt, -sau, /. silver ingot, -scfaaum, m. silver in thin leaves, or an imitation of it. -scheidtmg, /. separation of silver silver refining, -schein,... 

With the in situ ion-exchange method (Fig. 5), dilute sulfuric acid is used to precipitate the silver in the resin beads as silver sulfide instead of removing it with regenerant. The resin that is inside the ion exchange unit is used for many cycles without a loss in capacity. When the resin eventually loses its capacity to recover silver, or when there is sufficient silver to make recovery worthwhile, it is sent to a silver refiner who incinerates it to remove the silver. This may occur after between six months and a year. 

The ore is crushed and ground in.ball mills to pass through a 30-mesh sieve. It is mixed with suitable fluxes (limestone and quartz) and smelted in small blast-furnaces having a capacity of 25 to 30 tons per twenty-four hours. The products obtained are (i) flue dust, which is returned to the furnaces, and crude arsenious oxide, which is resublimed and sold (ii) a silicate slag, which is thrown away unless it contains more than 10 ounces of silver per ton (iii) crude silver bullion, which is mechanically detached and cupelled to a fineness of 994 before it is sold to silver refiners and (iv) a speiss of cobalt, nickel, iron, and copper arsenides, containing considerable amounts of silver. The crude silver bullion contains about three-fourths of the silver present in the ore. 

PURGATOR ARGENTI - Silver Refiner PUTRIFICIREN — To Putrefy... 

Fig. 22 Mobius and Balbach-Thum cells for silver refining.

Silver refining to dore specification is modelled on BRM practice, and is followed by a conventional parting plant operation employing Balbach Thum cells. 

The first industrially accepted process for silver refining was patented by Moebiusin 1884 who used an acidic stiver nitrate electrolyte. An industrial plant was commissioned in 1885 and the modern refining of silver still follows this pioneering work quite closely. 

Table 4.9 Comparispn of silver refining In the Moebius and Balbach-Tbiun cells...

Insoluble, black gold residues are recovered from the anode slimes of silver refining cells and are combined with gold collected from the cleaning of anode scrap. Tliis material is water washed on a filter to remove nitrates, boiled with H2SO4 to dissolve silver, then washed with water to remove soluble silver. The resulting yellow gold sand is dried, melted and cast into anodes, which typically have a composition Au 99.2%, Pd 0.5%, Ag <0.1% and Pt <0.08% wt. 

The term verditer appears to have only come into use in the late seventeenth century, whereas before that time there were other cuprammoniinn blues foimd in recipes but only intended for small scale or individual production. The term verditer came about when large scale production as an industrial by-product of silver refining occurred. Recipes from before 1600 differ from verditer in chemical composition and manufacture (Harley, 1982). 

Table 4.9 Comparison of silver refining in the Moebius and Balbach-Thum cells...

Silver Refining - 220 104 - E - E acid leach slimes of silver refinery containing Cu, Au, Ag, So. Te, Pt and Pd, moderate aeration... 

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