" " moisture 0.1513 "

0.1513 ◊ 20 = 3.026 ~3.02%.~

[Illustration: FIG. 3.]

Sometimes it may be advisable to dry 10 grams, in which case multiplying
the loss by 10 will give the percentage. The dried ore should be
transferred to a weighing-tube (fig. 3), and reserved for the subsequent
determinations. The weighing-tube with the ore must be marked, and kept
in a desiccator.

Most ores and inorganic substances can be dried, and their moisture
determined by the loss in this way. When, however, the substance
contains another somewhat volatile ingredient, it is exposed over
sulphuric acid in a desiccator for two days (if _in vacuo_, all the
better), and the loss determined. Moisture in dynamite should be
determined in this way.

When water is simply mechanically mixed with a substance it presents but
little difficulty. The combined water is a different matter. Slaked
lime, even when perfectly dry, contains much water; and if the water of
soda crystals were separated and frozen, it would occupy a volume equal
to that of the original crystals. Perfectly dry substances may contain
much water, and this combined water is retained by different materials
with very unequal vigour. Sodium sulphate and sodium phosphate crystals
lose water even when exposed under ordinary conditions to dry air. Soda
crystals when heated melt, and at a moderate temperature give off their
water with ebullition. The temperature at which all the water is given
up varies with each particular salt; the actual determination of the