Nitro-Explosives: A Practical Treatise | Page 8

lost in
the subsequent process of washing to which the nitro-compound is
subjected, in order to remove the excess of acids, the retention of which
in the nitro-glycerol is very dangerous. Nitro-glycerol, which was
formerly considered to be a nitro-substitution compound of glycerol,
was thought to be formed thus--
C_{3}H_{8}O_{3} + 3HNO_{3} = C{3}H_{5}(NO_{2})_{3}O_{3}
+ 3H_{2}O;
but more recent researches rather point to its being regarded as a nitric
ether of glycerol, or glycerine, and to its being formed thus--
C_{3}H_{8}O_{3} + 3 HNO_{3} = C{3}H_{5}(NO_{3})_{3} +
3H_{2}O. 92 227
|OH The formula of glycerine is C_{3}H_{8}O_{8}, or
C_{3}H_{5}|OH |OH
|ONO_{2} and that of the mono-nitrate of glycerine, C_{3}H_{5}|OH
|OH
|ONO_{2} and of the tri-nitrate or (nitro-glycerine),
C_{3}H_{5}|ONO_{2} |ONO_{2}
that is, the three hydrogens of the semi-molecules of hydroxyl in the

glycerine have been replaced by the NO_{2} group.
In the manufacture upon the large scale, a mixture of three parts by
weight of nitric acid and five parts of sulphuric acid are used. From the
above equation it will be seen that every 1 lb. of glycerol should give
2.47 lbs. of nitro-glycerol ((227+1)/92 = 2.47), but in practice the yield
is only about 2 lbs. to 2.22, the loss being accounted for by the
unavoidable formation of some of the lower nitrate, which dissolves in
water, and is thus washed away, and partly perhaps to the presence of a
little water (or other non-nitrable matter) in the glycerine, but chiefly to
the former, which is due to the acids having become too weak.

CHAPTER II.
_MANUFACTURE OF NITRO-GLYCERINE._
Properties of Nitro-Glycerine--Manufacture of
Nitro-Glycerine--Nitration-- The Nathan Nitrator--Separation--Filtering
and Washing--The Waste Acids-- Treatment of the Waste Acid from
the Manufacture of Nitro-Glycerine and Gun-Cotton.
~Properties of Nitro-Glycerine.~--Nitro-glycerol is a heavy oily liquid
of specific gravity 1.6 at 15° C., and when quite pure is colourless. The
commercial product is a pale straw yellow, but varies much according
to the purity of the materials used in its manufacture. It is insoluble in
water, crystallises at 10.5° C., but different commercial samples behave
very differently in this respect, and minute impurities prevent or delay
crystallisation. Solid nitro-glycerol[A] melts at about 12° C., but
requires to be exposed to this temperature for some time before melting.
The specific gravity of the solid form is 1.735 at +10° C.; it contracts
one-twelfth of its volume in solidifying. Beckerheim[B] gives the
specific heat as 0.4248 between the temperatures of 9.5° and 9.8° C.,
and L. de Bruyn gives the boiling point as above 200°.
[Footnote A: Di-nitro-mono chlorhydrin, when added to nitro-glycerine
up to 20 per cent., is said to prevent its freezing.]

[Footnote B: _Isb., Chem. Tech._, 22, 481-487. 1876.]
Nitro-glycerine has a sweet taste, and causes great depression and
vertigo. It is soluble in ether, chloroform, benzene, glacial acetic acid,
and nitro-benzene, in 1.75 part of methylated spirit, very nearly
insoluble in water, and practically insoluble in carbon bisulphide. Its
formula is C_{3}H_{5}(NO_{3})_{3}, and molecular weight 227.
When pure, it may be kept any length of time without decomposition.
Berthelot kept a sample for ten years, and Mr G. M'Roberts, of the
Ardeer Factory, for nine years, without their showing signs of
decomposition; but if it should contain the smallest trace of free acid,
decomposition is certain to be started before long. This will generally
show itself by the formation of little green spots in the gelatine
compounds, or a green ring upon the surface of liquid nitro-glycerine.
Sunlight will often cause it to explode; in fact, a bucket containing
some water that had been used to wash nitro-glycerine, and had been
left standing in the sun, has in our experience been known to explode
with considerable force. Nitro-glycerine when pure is quite stable at
ordinary temperatures, and samples have been kept for years without
any trace of decomposition. It is very susceptible to heat, and even
when quite pure will not stand a temperature of 100° C. for a longer
period than a few hours, without undergoing decomposition. Up to a
temperature of 45° C., however, properly made and purified nitro-
glycerine will remain unchanged almost indefinitely. The percentage
composition of nitroglycerine is as follows:--
Found. Theory for C_{3}H_{5}(N0_{2})_{3}.
Carbon 15.62 15.86 per cent. Hydrogen 2.40 2.20 " Nitrogen 17.90
18.50 " Oxygen ... 63.44 "
The above analysis is by Beckerheim. Sauer and Adou give the
nitrogen as 18.35 to 10.54 per cent. by Dumas' method; but I have
never found any difficulty in obtaining percentages as high as 18.46 by
the use of Lunge's nitrometer. The decomposition products by
explosion are shown by the following equation--
2C_{3}H_{5}(NO_{3})_{3} = 6CO_{2} + 5H_{2}O + 6N + O;

that is, it contains an excess of 3.52 per cent. of oxygen above that
required for complete combustion; 100 grms. would be converted into--
Carbonic Acid (CO_{2})