Agricola, Georgius, De re metallica, 1912/1950

Table of figures

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              <s>
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              the
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              cadmía;
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              this sweeping is done twice a year. </s>
              <s>The soot mixed with
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                <emph type="italics"/>
              pompholyx
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              and the
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              cadmia,
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              being chipped off, is thrown down through
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              a long chute made of four boards joined in the shape of a rectangle,
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              that they should not fly away. </s>
              <s>They fall on to the floor, and are sprinkled
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              with salt water, and are again smelted with ore and litharge, and become
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              an emolument to the proprietors. </s>
              <s>Such chambers, which catch the metallic
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              substances that rise with the fumes, are profitable for all metalliferous
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              ores; but especially for the minute metallic particles collected by washing
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              crushed ores and rock, because these usually fly out with the fire of the
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              furnaces.</s>
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              <s>I have explained the four general methods of smelting ores; now I
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              will state how the ores of each metal are smelted, or how the metal is obtained
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              from the ore. </s>
              <s>I will begin with gold. </s>
              <s>Its sand, the concentrates from
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              washing, or the gold dust collected in any other manner, should very often
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              not be smelted, but should be mixed with quicksilver and washed with tepid
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              water, so that all the impurities may be eliminated. </s>
              <s>This method I ex­
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              plained in Book VII. </s>
              <s>Or they are placed in the
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              aqua
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              which separates
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              gold from silver, for this also separates its impurities. </s>
              <s>In this method we
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              see the gold sink in the glass ampulla, and after all the
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              aqua
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              has been drained
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              from the particles, it frequently remains as a gold-coloured residue at the
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              bottom; this powder, when it has been moistened with oil made from
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              argol
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              27
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              , is then dried and placed in a crucible, where it is melted with borax
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              or with saltpetre and salt; or the same very fine dust is thrown into molten
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              silver, which absorbs it, and from this it is again parted by
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              aqua valens
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              28
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              .</s>
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              <s>It is necessary to smelt gold ore either outside the blast furnace in a
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              crucible, or inside the blast furnace; in the former case a small charge of ore
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              is used, in the latter a large charge of it.
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              Rudís
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              gold, of whatever colour
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              it is, is crushed with a
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              líbra
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              each of sulphur and salt, a third of a
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              líbra
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              of copper,
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              </s>
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