or, what comes to the same thing, he can dissolve away his superfluous
gelatine at a lower temperature than would otherwise be necessary.

The cleanest rain-water which can ordinarily be collected in a town is
not sufficiently pure to be used with advantage in the preparation of
the nitrate bath, it being advisable to use the purest distilled water
for this purpose; and in many cases it is well to carefully distill
water for the bath in a glass apparatus of the kind figured below.

[Illustration]

A, thin glass flask serving as a retort. The tube, T, is fitted
air-tight to the flask by a cork, C.

B, receiver into which the tube, T, fits quite loosely.

D, water vessel intended to keep the spiral of lamp wick, which is shown
as surrounding T, in a moist condition. This wick acts as a siphon, and
water is gradually drawn over into the lower receptacle, E.

L, spirit lamp, which may, in many cases, be advantageously replaced by
a Bunsen burner.

A small metal still, provided with a tin condensing worm, is, however, a
more generally serviceable arrangement, and if ordinary precautions are
taken to make sure that the worm tube is clean, the resulting distilled
water will be nearly as pure as that distilled in glass vessels.

Such a still as that figured below can be heated conveniently over an
ordinary kitchen fire, and should find a place among the appliances