remove traces of bleaching matter, and dried) by means of a quill pen.
When the marks thus produced are dry, the paper is cut into pieces of the
same size as the test paper previously described, in such a way that each
piece has a brown line across it near the middle of its length, and only
such strips are preserved in which the brown line has a breadth varying
from 1\2 mm. to 1 mm. (1/50 of an inch to 1/25 of an inch).

~Testing Dynamite, Blasting Gelatine, and Gelatine Dynamite.~--Nitro-
glycerine preparations, from which the nitro-glycerine can be extracted in
the manner described below, must satisfy the following test, otherwise
they will not be considered as manufactured with "thoroughly purified
nitro-glycerine," viz., fifteen minutes at 160° F. (72° C.).

~Apparatus required.~--A funnel 2 inches across (_d_), a cylindrical
measure divided into grains (_e_), Fig. 47.

~Mode of Operation.~--About 300 (19.4 grms.) to 400 grains (26 grms.) of
dynamite (_b_), finely divided, are placed in the funnel, which is loosely
plugged by freshly ignited asbestos (_a_). The surface is smoothed by
means of a flat-headed glass rod or stopper, and some clean washed and
dried kieselguhr (_c_) is spread over it to the depth of about 1/8 inch.
Water is then poured on from a wash bottle, and when the first portion has
been soaked up more is added; this is repeated until sufficient nitro-
glycerine has collected in the graduated measure (_e_). If any water
should have passed through, it must be removed from the nitro-glycerine by
filter paper, or the nitro-glycerine may be filtered.

[Illustration: FIG. 47.--APPARATUS FOR SEPARATING THE NlTRO-GLYCERINE FROM
DYNAMITE.]