[Illustration: FIG. 48.--TEST TUBE ARRANGED FOR HEAT TEST.]

~Application of Test.~--The thermometer is fixed so as to be inserted
through the lid of the water bath into the water, which is maintained at
160° F. (72° C.), to a depth of 2-3/4 inches. Fifty grains (= 3.29 grms.)
of nitro-glycerine to be tested are weighed into the test tube, in such a
way as not to soil the sides of the tube (use a pipette). A test paper is
fixed on the hook of the glass rod, so that when inserted into the tube it
will be in a vertical position. A sufficient amount of a mixture of half
distilled water and half glycerine, to moisten the upper half of the
paper, is now applied to the upper edge of the test paper by means of a
glass rod or camel's hair pencil; the cork carrying the rod and paper is
fixed into the test tube, and the position of the paper adjusted so that
its lower edge is about half way down the tube; the latter is then
inserted through one of the holes in the cover to such a depth that the
lower margin of the moistened part of the paper is about 5/8 inch above
the surface cover. The test is complete when the faint brown line, which
after a time makes its appearance at the line of boundary between the dry
and moist part of the paper, equals in tint the brown line of the standard
tint paper.

~Blasting Gelatine, Gelatine Dynamite, Gelignite, &c.~--Fifty grains (=
3.29 grms.) of blasting gelatine are intimately mixed with 100 grains (=
6.5 grms.) of French chalk. This is done by carefully working the two
materials together with a wooden pestle in a wooden mortar. The mixture is
then gradually introduced into the test tube, with the aid of gentle
tapping upon the table between the introduction of successive portions of
the mixture into the tube, so that when the tube contains all the mixture
it shall be filled to the extent of 1-3/4 inch of its height. The test
paper is then inserted as above described for nitro-glycerine. The sample