technical product, owing to the
presence of di-nitro-glycerine, freezes at 10.5 deg. C. According to Raoult's
law, the lowering of the freezing point caused by _m_ grms. of a substance
with the molecular weight M, when dissolved in 100 grms. of the solvent,
is expressed by the formula: [Delta] = E(_m_/M), where E is a constant
characteristic for the solvent in question. The value of E for nitro-
glycerine was found to be 70.5 when calculated, according to Van't Hoff's
formula, from the melting point and the latent heat of fusion of the
substance. Determinations of the lowering of the freezing point of nitro-
glycerine by additions of benzene, nitro-benzene, di-nitro-benzene, tri-
nitro-benzene, p.-nitro-toluene, o.-nitro-toluene, di-nitro-toluene,
naphthalene, nitro-naphthalene, di-nitro-naphthalene, ethyl acetate, ethyl
nitrate, and methyl alcohol, gave results agreeing fairly well with
Raoult's formula, except in the case of methyl alcohol, for which the
calculated lowering of the freezing point was greater than that observed,
probably owing to the formation of complex molecules in the solution. The
results show that, in general, the capacity of a substance to lower the
freezing point of nitro-glycerine depends, not upon its freezing point, or
its chemical composition or constitution, but upon its molecular weight.
Nauckhoff states that a suitable substance for dissolving in nitro-
glycerine, in order to lower the freezing point of the latter, must have a
relatively low molecular weight, must not appreciably diminish the
explosive power and stability of the explosive, and must not be easily
volatile at relatively high atmospheric temperatures; it should, if
possible, be a solvent of nitro-cellulose, and in every case must not have
a prejudicial influence on the gelatinisation of the nitro-cellulose.

[Footnote A: Eng. Pat. 25,797, November 1904.]

[Footnote B: _Z. Angew. Chem._, 1905, 18, 11-22, 53-60.]

~Manufacture of Nitro-Glycerine.~--Nitro-glycerine is prepared upon the
manufacturing scale by gradually adding glycerine to a mixture of nitric
and sulphuric acids of great strength. The mixed acids are contained in a
lead vessel, which is kept cool by a stream of water continually passing
through worms in the interior of the nitrating vessel, and the glycerine
is gradually added in the form of a fine stream from above. The
manufacture can be divided into three distinct operations, viz.,
nitration, separation, and