[Illustration: FIG. 30.]
A convenient plan for filling a burette from below is shown in fig. 30.
The diagram explains itself. The bottle containing the standard solution
is connected with the burette by a syphon arrangement through the glass
tube and T-piece. The flow of liquid into the burette is controlled by
the clip. When this clip is opened, the burette fills; and when it is
closed, the burette is ready for use in the ordinary way.
~Measuring Gases.~--Lange's nitrometer (fig. 69) is a very convenient
instrument for many gasometric methods. It requires the use of a fair
quantity of mercury. In fig. 31, there is a representation of a piece of
apparatus easily fitted up from the ordinary material of a laboratory.
It is one which will serve some useful purposes. It consists of a
wide-mouthed bottle fitted (by preference) with a rubber cork. The cork
is perforated, and in the perforation is placed a glass tube which
communicates with the burette. The burette is connected by a rubber tube
and a Y-piece, either with another burette or with a piece of ordinary
combustion-tube of about the same size. The wide-mouthed bottle contains
either a short test-tube or an ordinary phial with its neck cut off. In
working the apparatus the weighed substance is put in the bottle and the
re-agent which is to act on it, in the test-tube; the cork is then
inserted.
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