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GOL

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GOL

metal. When the matter in the cone is becomei'olid, it may eafily be got out by inverting thecone and giving it a few blows in this fituation :it will be found to Confift of a reguline mafs ofgold and antimony covered by a fcoria compofedof the former alloy of the gold united to thefulphur of the antimony. The gold howeverftill retains a little of its alloy, and in coni'e-quence requires to be again melted a fecoitd oreven a third or fourth time with the fame quan-tity of fulphuret of antimony. From thefe laftfulions the gold receives only a flight additionof antimony, as this metal unites with it only inproportion as it is deprived of its own fulphurby the fmall portion of alloy yet remaining inthe gold. Thefe proceffes being duly performed,the antimony is to be feparated in the manneralready defcribed and the gold remains perfectlypure. Where the proportion of antimony isconfiderable, it is likely that its feparation fromthe gold,, which is ufually a tedious bufinefs,might be expedited by a judicious fufion withfulphur, which converting part of the antimonyinto fulphuret would caufe its fpontaneous fepa-ration from the reft. The metals from whichgold may be purified with particular advantageby means of antimony are iron, copper, tin,lead and filver.

Separation of a fmall quantity of Gold from alarge quantity of Copper.

In old gilt copper wire, button-makers’ clip-pings, and auriferous copper from Japan andother places, although the proportion of preciousmetal is too great to be neglefted, yet it is byno means fufficiently large to admit of feparationby the cupel or by fulphuret of antimony. Theprocefs of eliquation, or of fufing the copperwith a large quantity of lead, , and then expofingthe mixture to a heat capable of melting outthis latter while the former ftill continues folid,although practifed with fuccefs in the feparationof filver from copper has been repeatedly at-tempted in vain for the extraftion of gold.But die following method, firft publifhed byAlonzo Barba, may on this occafion be refortedto with good effect.

Let the copper be firft melted and granulatedby being poured into water; then heat themetal red-hot in a crucible, and project on it atdifferent times portions of common fulphur till'the whole becomes black and brittle; then reduceit in a mortar or by any other convenient wayto a fine powder and fubject it to amalgamationin the fame manner as the proper ores of gold;the mercury will diffolve out the whole of thelatter metal without exerting the leaft action on

the fulphuret of copper, which may afterwardsbe brought to the malleable metallic ftate byreading and fufion, as already deferibed in thearticle copper.

There is another method however ftill moreadvantageous which may be employed for thispurpofe. Equal weights of fulphur and lithargeare to be mixed together and combined by haftyfufion into a black fparkling mafs: the gold-holding copper being then melted, the fulphur-etted lead is thrown in by fmall quantities at atime till its amount nearly equals that of thecopper. All the ingredients, in confcquenceof the lead being in the ftate of oxyd, unitetogether into an uniform mafs. When thewhole is in compleat fufion fome finely pulver-ized charcoal is added at two or three feveraltimes, being carefully ftirred in with a piece offtrong copper wire. The charcoal immediatelydeoxygenates the lead, which finking to the bot-tom in its metallic form, draws with it thewhole of the gold alfo, leaving a fcoria of ful-phuretted copper floating on its furface. The goldis afterwards freed from the lead by cupellation.

This fame procefs might no doubt be appliedto the feparation of gold from iron.

Separation of gold from Silver .

If the proportion of gold is very fmall, thebell way of feparating it from the filver is bymeans of fulphur. For this purpofe the alloy ismelted, and granulated by being poured intocold water kept conftantly in agitation by awicker brulh or rod. Of the granulated metalfrom an eighth to a fifth is referved, and thereft is well mingled with about an eighth of itsweight of pulverized fulphur, which readilyadheres to the moift grains. This mixture isput into a covered crucible and gently heatedfor fome time, that the metal may be thorough-ly penetrated by the fulphur: when this iseffected, the fire is to be raifed, and the mafsbrought into fufion. In thefe circumftances itmight be thought that the gold, on account ofits great fpecific gravity, having alfo no affinitywith fulphuretted filver, would fall in drops tothe bottom of the crucible, and there unite intoa mafs by itfelf. This however is not the cafe;the fulphuretted filver forms a tough vilcousfluid, in confequence of which the minutegrains of gold are prevented from fubfiding.When therefore the mafs has been in full fufionabout an hour, fo that the fulphur is compleatlyunited with the filver, and any accidental excefsof it has burnt oft, one third of the referveafilver in grains is added, and as foon as meltedis ftirred with a wooden rod in order to mix it