the ore in a frying-pan heated over a gas flame, or in an ordinary oven,
until a cold bright piece of metal or glass is no longer damped when
held over it. The loss of weight in grains = moisture.

Properly, however, this work should be done by the assayer, if only for
the following reason. It is assumed that the dry ore of the sampler and
of the assayer are the same thing; according to the nature of the ore,
this may or may not be the case. The assayer, however, uses the sample
which he has dried for his moisture-determination, as the dry ore on
which he makes his other assays, and no variation in moisture would
influence the other and more important determinations. Some ores are
sent to the smelter with from 5 to 15 per cent. of adherent water. In
these cases it is best to spread out the sample, and taking equal
portions fairly at regular intervals, weigh into a Berlin dish 20 grams.
This should then be dried over a sand-bath, or if the ore is likely to
be injured by excess of heat, over a water-bath until the weight is
constant. The loss of weight multiplied by 5 gives the percentage of
water present.

Example:--

Weight of dish + wolfram 32.67 grms.
" " dish 12.67 "
-----
" " wolfram 20.00 "

" " dish + wolfram 32.67 "
" " " dried 30.15 "
-----
" " water 2.52 "