Agricola, Georgius, De re metallica, 1912/1950

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              <s>
                <pb pagenum="243"/>
              Mix one part of this ore, when it has been roasted, crushed, and washed, with
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              three parts of some powder compound which melts ore, and six parts of lead.
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              </s>
              <s>Put the charge into the triangular crucible, place it in the iron hoop to which
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              the double bellows reaches, and heat first in a slow fire, and afterward
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              gradually in a fiercer fire, till it melts and flows like water. </s>
              <s>If the ore does
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              not melt, add to it a little more of these fluxes, mixed with an equal portion
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              of yellow litharge, and stir it with a hot iron rod until it all melts. </s>
              <s>Then
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              take the crucible out of the hoop, shake off the button when it has cooled,
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              and when it has been cleansed, melt first in the scorifier and afterward in
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              the cupel. </s>
              <s>Finally, rub the gold which has settled in the bottom of the cupel,
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              after it has been taken out and cooled, on the touchstone, in order to find out
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              what proportion of silver it contains. </s>
              <s>Another method is to put a
                <emph type="italics"/>
              centum­
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              pondium
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              (of the lesser weights) of gold ore into the triangular crucible, and
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              add to it a
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              drachma
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              (of the larger weights) of glass-galls. </s>
              <s>If it resists melting,
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              add half a
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              drachma
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              of roasted argol, and if even then it resists, add the
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              same quantity of roasted lees of vinegar, or lees of the
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              aqua
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              which separates
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              gold from silver, and the button will settle in the bottom of the crucible.
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              </s>
              <s>Melt this button again in the scorifier and a third time in the cupel.</s>
            </p>
            <p type="main">
              <s>We determine in the following way, before it is melted in the muffle
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              furnace, whether pyrites contains gold in it or not: if, after being three times
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              roasted and three times quenched in sharp vinegar, it has not broken nor
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              changed its colour, there is gold in it. </s>
              <s>The vinegar by which it is quenched
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              should be mixed with salt that is put in it, and frequently stirred and dissolved
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              for three days. </s>
              <s>Nor is pyrites devoid of gold, when, after being roasted and
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              then rubbed on the touchstone, it colours the touchstone in the same way that
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              it coloured it when rubbed in its crude state. </s>
              <s>Nor is gold lacking in that,
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              whose concentrates from washing, when heated in the fire, easily melt, giving
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              forth little smell and remaining bright; such concentrates are heated in the
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              fire in a hollowed piece of charcoal covered over with another charcoal.</s>
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            <p type="main">
              <s>We also assay gold ore without fire, but more often its sand or the con­
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              centrates which have been made by washing, or the dust gathered up by
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              some other means. </s>
              <s>A little of it is slightly moistened with water and heated
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              until it begins to exhale an odour, and then to one portion of ore are placed
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              two portions of quicksilver
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              28
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              in a wooden dish as deep as a basin. </s>
              <s>They are
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              mixed together with a little brine, and are then ground with a wooden pestle
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              for the space of two hours, until the mixture becomes of the thickness of dough,
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              and the quicksilver can no longer be distinguished from the concentrates
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              made by the washing, nor the concentrates from the quicksilver. </s>
              <s>Warm, or
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              at least tepid, water is poured into the dish and the material is washed until
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              the water runs out clear. </s>
              <s>Afterward cold water is poured into the same dish,
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              and soon the quicksilver, which has absorbed all the gold, runs together
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              into a separate place away from the rest of the concentrates made by
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              washing. </s>
              <s>The quicksilver is afterward separated from the gold by means
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              of a pot covered with soft leather, or with canvas made of woven
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              threads of cotton; the amalgam is poured into the middle of the cloth or </s>
            </p>
          </chap>
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