Engineering Chemistry S Datta

342 ENGINEERING CHEMISTRY
belonging to this class. Composition is approx. 91.5% nitroglycerin, 8% nitrocotton
and 0.5% CaCO 3
. Blasting gelatin is a solid, elastic material. Lower ratio of nitrocotton
in nitroglycerin gives viscous liquid instead of the solid mass. They excell others by
four important properties—high bulk density, highest water resistance among dynamites,
stick well to holes into which they are loaded because of their plastic nature
and lastly they excell from the point of view of fumes. They are not sensitive to shock
and hence are preferred for use under wet conditions. They are mainly used for
submarine blasting, blasting of hard rocks, underground blasting like deep-well shooting,
tunnel driving etc. Disadvantage is that they are costly compared to others.
(iii) Gun cotton or cellulose nitrate. It is prepared by steeping cotton for 30 minutes in a
cooled mixture of conc. H 2
SO 4
and conc. HNO 3
C 6
H 7
O 2
(OH) 3
+ 3HNO 3
⎯⎯→ C 6
H 7
O 2
(NO 3
) 3
+ 3H 2
O
Dry gun cotton can be ignited by shock. It explodes very sharply if set on fire. Dry
gun cotton is used in torpedos, submarines, as a propellant in rifles, artillery shells.
Rate of explosion of it can be controlled by mixing other substances.
(iv) Ammonia dynamites. These are dynamites in which a portion of the nitroglycerin
has been replaced by ammonium nitrate. Their strengths are equivalent to straight
dynamite but of lower velocity.
They possess some attractive properties for which they have wide use. These are—
effectiveness, cheapness, insensitiveness to shock and friction, non-inflammability.
The only disadvantage is their low water resistance, so they are not fit to be used in
wet condition.
(v) Cordite. It is made by 65 parts of gun cotton, 30 parts of nitroglycerine and 5 parts of
vaseline in acetone. This paste is rolled and cut into pieces of different sizes Vaseline
acts as a stabilizer and cooling agent on the powder. After the evaporation of the
acetone, the horny cordite remains. Gun cotton controls the explosive reaction of
nitroglycerine and it can be safely used for large caliber naval guns.
(vi) Gelignite. This powerful explosive is a mixture of 65% blasting gelatine and 35%
absorbing powder. It is used for under-water works.
Permissible dynamites. These are high explosives specially used for gasy coal mines
etc. where inflammable gases are present.
The common permissible contain (a) about 80% ammonium nitrate, (b) low percentage
of nitroglycerine as sensitizing agent, dynamites, (c) fibrous combustible material to utilize
the excess oxygen of ammonium nitrate and absorbing nitroglycerine.
The gelatinous type of permissible dynamites contains a higher percentage of
nitroglycerine and lower content of ammonium nitrate along with a small percentage of
nitrocotton. This is mainly used for blasting in wet conditions.
Commercial High Explosives Containing No Nitroglycerine
(i) Ammonium nitrate explosives. This type of explosive, called Notramon, is a safe
but high-velocity agent. It is incapable of detonating under the influence of blasting
cap but once initiated by booster charge it can propagate explosion indefinitely.
Ammonium nitrate is highly deliquescent salt, but this disadvantage can be overcome