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a
somewhat expensive piece of apparatus, and any one not wishing to incur
such an outlay may obtain results nearly as good with the beam balance
previously described. In its use for this purpose a sinker in the shape
of a cylindrical bulb is suspended from a position marked by a notch
near the end of the long arm. By putting shot in the pans and using the
rider d, the beam is brought to a horizontal position with the
sinker in air. The sinker is then immersed in the heavy solution, and a
weight is selected, which, when placed near the end of the beam will
bring the latter to a horizontal position. The position of this weight
gives relatively the weight of the heavy solution displaced by the
sinker. After washing, the sinker is immersed in water, and the same
weight is placed nearer the fulcrum until the beam becomes horizontal.
The position of this weight gives relatively the weight of the water
displaced by the sinker. The larger weight divided by the smaller gives
the desired specific gravity.
By
employing proper formulae, weights of bodies may be found if their
specific gravities be known, or the specific gravity of one, if its
weight and the weight and specific gravity of another be known.
Thus
if a diamond is set in a gold ring, it is often desirable to know the
weight of the diamond, or its specific gravity, or the specific
gravity, and hence the fineness, of the gold of which the ring is
composed, withÂout removing the stone. Each of these values, and even
others, can be found by employing the following formulae. These are
derived from two equations in which A represents the weight of the
stone, a its specific* gravity; B the weight of the gold, and b its
specific gravity; and C the combined weight of the ring and stone, and
c their specific gravity.
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