From: "donald haarmann" <donald-haarmann@worldnet.att.net>
Newsgroups: alt.engr.explosives
Subject: Frozen Gelignite
Date: Wed, 26 Jan 2000 22:57:15 -0500

The Journal of the Society of Chemical Industry
Vol. XXVI -- 1907 pg. 1296

Explosion which occurred during the operation of thawing gelignite in
connection with the construction of the new Great Western Railway line
from Clarbeston Road to Fishguard, in the county of Pembroke on the 26
Feb., 1906 ; Circumstances attending an --.. Captain M. B. Lloyd, H. M.
Inspector of Explosives.

A CHARGEMAN was engaged in thawing five froze gelignite cartridges,
before use, in a warming pan. He had emptied out the cooled water from
the jacket of the warming-pan, and was replacing it by hot water from a
can recently taken from the fire, when a slight hissing noise was heard
and immediately afterwards the explosion occurred. The effect on the
warming-pan itself was remarkable. Of the lid no traces were found except
the small fragments taken out of the men's wounds; the body of the
warming pan, on the other hand, showed no signs of having had an
explosion in it. The hissing was undoubtedly that produced by the active
decomposition of the gelignite, which rated sufficient gas to blow off
the lid of the warming pan, and carry with it the top cartridge, which
had been across the end of the others and which might well, from its
size, have been slightly jammed in the flange of the lid. On the lid
reaching the ground the cartridge, already in an extremely sensitive
condition, detonated violently. In discussing the probable cause of the
explosion. Capt. Lloyd dismisses as wholly improbable that pouring
boiling water into the outer chamber of a warming pan should cause an
explosion of well purified gelignite, or, seeing that the lid of the
warming-pan was on, that a spark should have caused the initial
decomposition. He arrives at the conclusion that the explosive itself was
unstable, and that the hot water raised it to a sufficiently high
temperature to determine its active decomposition. The purity of
gelignite is determined by the Abel heat test, and no discoloration of
the starch-iodide paper should be produced, at a temperature of 160o F.,
in less than 10 minutes, if the explosive has, been well purified. Dr.
Dupré's examination of a sample from the same batch of explosive
showed a heat test of over half an hour, but be suspected, owing to the
abnormally high heat test, that the explosive had been treated with a "
masking agent," which whilst having no action in improving the stability
of the explosive, effectually prevented any indication by the heat test.
The substance most usually employed for this purpose is mercuric
chloride. On keeping a sample of the explosive for six weeks at a
constant temperature of 90o F., the heat test fell to 15 minutes. At the
end of 12 weeks the heat test had fallen to 11 minutes.

So small a proportion of the mercury salt as 0.00025 per cent. is
sufficient to mask the heat test for a considerable time. The presence of
mercury was definitely proved by the spectroscopic method. Captain Lloyd
considers that the use of masking agents of this description can only
have one effect, and that to conceal the instability of the explosive.
The offence against the Act is one, too, which is liable to be a cause of
great danger, in that with an explosive so treated, there is no means of
finding out whether it is dangerously unstable or not; or, even worse, a
test may lead to the, belief that dangerously unstable explosives are of
good quality, and fit for prolonged storage, for a voyage through the
tropics, or for somewhat drastic treatment for the purpose of thawing
them. The conclusions drawn from the investigation of the accident
are:--(1).  That the explosive ignited spontaneously in the warming-pan.
(2). That the explosion occurred outside the warming-pan but in close
proximity to the lid. (3). That one at least of the cartridges was made
of extremely unstable explosive. (4). That an unauthorised and illegal
ingredient had been added to the explosive which had the effect of
concealing its lack of stability.

-G W. MC


-----------
Gelignte:

65% gelatine of ...

96 3/13% NG  62.500%
 3 11/13    collodion cotton    2.500%

35% absorbing powder....

24% wood pulp   8.400%
  1     soda           0.350%

Oscar Guttmann
The Manufacture of Explosives
MacMillan 1895



--
donald j haarmann
----------------------------
An explosion may be defined as a loud noise
accompanied by the sudden going away of
things from the places where they were before.
                   Joseph Needham