The Chemistry of Powder and Explosives - Sciencemadness Dot Org

DINITROGLYCERIN 215
cerin. It mixes with the latter substance in all proportions and
lowers its freezing point, and was formerly used in Germany in
such mixtures in non-freezing dynamites. It has now been superseded
entirely for that purpose by dinitrochlorohydrin which is
insoluble in water, and cheaper and more convenient to manufacture.
Dinitroglycerin is never formed alone by the nitration of
glycerin but is always accompanied by the trinitrate or the
mononitrate or both. If the nitration is carried out in a manner
to give the best yields of the dinitrate, then considerable trinitrate
is formed: if the process is modified to reduce the yield
of trinitrate, then the yield of dinitrate is also reduced and some
mononitrate is formed. If 3 or 4 parts by weight of nitric acid is
added slowly to 1 part of glycerin, so that the glycerin or its
nitrated product is always in excess, then the dinitrate is the
principal product. If the order of mixing is reversed, so that the
glycerin dissolves first in the strong nitric acid, then the yield of
trinitrate is more considerable. Dinitroglycerin is formed if glycerin
is added to mixed acid which is low in nitric acid or high
in water, or which contains insufficient sulfuric acid for the necessary
dehydrating action. It is also one of the products of the
hydrolysis of nitroglycerin by cold concentrated (95%) sulfuric
acid, the trinitrate by this reagent being in part dissolved and in
part converted to the dinitrate, the mononitrate, and to glyceryl
sulfate according to the relative amount of sulfuric acid which is
used. Dinitroglycerin is separated from its mixture with nitroglycerin
and obtained pure by treating the oil with about 15 volumes
of water, separating the insoluble trinitrate, extracting the
aqueous solution with ether, washing the ether with dilute sodium
carbonate solution, and evaporating. The resulting dinitroglycerin
gives a poor heat test because of the peroxide which it
contains from the ether. Material which gives an excellent heat
test may be procured by evaporating the aqueous solution in
vacuum.
The dinitroglycerin obtained by the nitration of glycerin is a
colorless, odorless oil, more viscous and more volatile than nitroglycerin.
It causes the same kind of a headache. It has a specific
gravity of 1.51 at 15°, boils at 146-148° at 15 mm. with only
slight decomposition, and solidifies at —40° to a glassy solid
which melts if the temperature is raised to —30°, It is readily