Agricola, Georgius, De re metallica, 1912/1950

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    <archimedes>
      <text>
        <body>
          <chap>
            <p type="main">
              <s>
                <pb pagenum="239"/>
              are equal portions of very minute lead granules, melted salt,
                <emph type="italics"/>
              stíbíum
                <emph.end type="italics"/>
              and
                <lb/>
              iron slag Or else take equal portions of gold ore, vitriol, argol, and of salt.
                <lb/>
              </s>
              <s>So much for the fluxes.</s>
            </p>
            <p type="main">
              <s>In the assay furnace, when it has been prepared in the way in which I
                <lb/>
              have described, is first placed a muffle. </s>
              <s>Then selected pieces of live charcoals
                <lb/>
              are laid on it, for, from pieces of inferior quality, a great quantity of ash collects
                <lb/>
              around the muffle and hinders the action of the fire. </s>
              <s>Then the scorifiers are
                <lb/>
              placed under the muffle with tongs, and glowing coals are placed under the
                <lb/>
              fore part of the muffle to warm the scorifiers more quickly; and when the lead
                <lb/>
              or ore is to be placed in the scorifiers, they are taken out again with the
                <lb/>
              tongs. </s>
              <s>When the scorifiers glow in the heat, first of all the ash or small
                <lb/>
              charcoals, if any have fallen into them, should be blown away with an iron
                <lb/>
              pipe two feet long and a digit in diameter; this same thing must be done
                <lb/>
              if ash or small coal has fallen into the cupels. </s>
              <s>Next, put in a small ball of lead
                <lb/>
              with the tongs, and when this lead has begun to be turned into fumes and
                <lb/>
              consumed, add to it the prepared ore wrapped in paper. </s>
              <s>It is preferable that
                <lb/>
              the assayer should wrap it in paper, and in this way put it in the scorifier,
                <lb/>
              than that he should drop it in with a copper ladle; for when the
                <lb/>
              scorifiers are small, if he uses a ladle he frequently spills some part of the
                <lb/>
              ore. </s>
              <s>When the paper is burnt, he stirs the ore with a small charcoal held in
                <lb/>
              the tongs, so that the lead may absorb the metal which is mixed in the ore;
                <lb/>
              when this mixture has taken place, the slag partly adheres by its cir­
                <lb/>
              cumference to the scorifier and makes a kind of black ring, and partly
                <lb/>
              floats on the lead in which is mixed the gold or silver; then the slag must
                <lb/>
              be removed from it.</s>
            </p>
            <p type="main">
              <s>The lead used must be entirely free from every trace of silver, as is that
                <lb/>
              which is known as
                <emph type="italics"/>
              Víllacense.
                <emph.end type="italics"/>
                <emph type="sup"/>
              26
                <emph.end type="sup"/>
              But if this kind is not obtainable, the lead
                <lb/>
              must be assayed separately, to determine with certainty that proportion of
                <lb/>
              silver it contains, so that it may be deducted from the calculation of the
                <lb/>
              ore, and the result be exact; for unless such lead be used, the assay will be
                <lb/>
              false and misleading. </s>
              <s>The lead balls are made with a pair of iron tongs,
                <lb/>
              about one foot long; its iron claws are so formed that when pressed
                <lb/>
              together they are egg-shaped; each claw contains a hollow cup, and when
                <lb/>
              the claws are closed there extends upward from the cup a passage, so there
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              are two openings, one of which leads to each hollow cup. </s>
              <s>And so when the
                <lb/>
              molten lead is poured in through the openings, it flows down into the hollow
                <lb/>
              cup, and two balls are formed by one pouring.</s>
            </p>
            <p type="main">
              <s>In this place I ought not to omit mention of another method of assaying
                <lb/>
              employed by some assayers. </s>
              <s>They first of all place prepared ore in the
                <lb/>
              scorifiers and heat it, and afterward they add the lead. </s>
              <s>Of this method I
                <lb/>
              cannot approve, for in this way the ore frequently becomes cemented, and
                <lb/>
              for this reason it does not stir easily afterward, and is very slow in mixing
                <lb/>
              with the lead.</s>
            </p>
          </chap>
        </body>
      </text>
    </archimedes>
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