satisfactory solution of the problem has been found. Among the substances
that have been proposed and used with more or less success, are nitro-
benzene, nitro-toluene, di-nitro-mono-chlorhydrine, solid nitro
derivatives of toluene,[A] are stated to lower the freezing point of
nitro-glycerine to -20°C. without altering its sensitiveness and
stability. The subject has been investigated by S. Nauckhoff,[B] who
states that nitroglycerine can be cooled to temperatures (-40° to -50° C.)
much below its true freezing point, without solidifying, by the addition
of various substances. When cooled by means of a mixture of solid carbon,
dioxide, and ether, it sets to a glassy mass, without any perceptible
crystallisation. The mass when warmed to 0°C. first rapidly liquefies and
then begins to crystallise. The true freezing point of pure nitro-
glycerine was found to be 12.3°C. The technical product, owing to the
presence of di-nitro-glycerine, freezes at 10.5° 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