SAFETY OF COPPER/BRASS SCREENS WITH CHLORATE=20
COMPOSITIONS
by
The WiZ (Donald J Haarmann)

(The following article was in response to Ed Raszkowski's Question in =
PGI=20
Bulletin No. 38.)

Dr. McLain and Donald Lewis; Effects of Phase Change in Solid-Solid=20
Reactions-1966, [my copy courtesy of E.R.], determined that when a=20
mixture of potassium n chlorate was doped with copper chlorate, and then =

ground with purified sulfur [a brave move], the mixture detonated=20
spontaneously after being let stand undisturbed on a shelf for only =
thirty=20
minutes! The experiment was repeated using the same components,=20
simply placed in a plastic vial and mixed by "tumbling the vial =
approximately=20
ten minutes about its major axes." After approximately twenty-four hours =
of=20
standing behind a barricade, a similar detonation occurred. [A less=20
complete discussion of this work is reported in Dr. McLain's book; pg. =
78.]

They concluded as a result of these experiments that; "Aside from the=20
spectacular, the finding that a potassium chlorate could be made which=20
when ;nixed with sulfur is spontaneously detonable at room temperature=20
there is a byproduct(s) of this experiment."

The doctrine of using brass, bronze or copper screens, tools=20
and jigs for pyrotechnic mixing and loading for non-sparking=20
properties certainly needs to be reexamined in light of these=20
findings. Emphasis added]

The warning is repeated by Ellern. (Pg. 304)

J.C. Shumacher; Perchlorates: Their Properties, Manufacture and Use;=20
page 206+ff reports that the "***decomposition [of ammonium perchlorate] =

was strongly catalyzed by powdered copper metal or cupric oxide, and to =
a=20
lesser extent by sodium chlorate, lithium or potassium dichromate."=20
"emphasis added]

even more importantly he states on page 215:

For example a number of fires in the drying and packaging=20
equipment of the AMMONIUM perchlorate plant of Western=20
Electrochemical Company (now American Potash dc=20
Chemical Corporation) were found to have been caused when=20
the perchlorate crystals came into contact with copper tubing=20
in the vibrating pan-dryer heat exchanger. When stainless=20
steel was substituted for copper the fires ceased. Ammonium=20
perchlorate was found to be most sensitive to ignition at a=20
moisture content of 0.02 to 0.5 per cent, [how dry are your=20
stars?], particularly when it is contaminated with copper and=20
possibly in the presence of other metallic contaminants. This=20
experience confirms other reports of the accelerating effect of=20
copper on the thermal decomposition of ammonium=20
perchlorate, and pyridine perchlorate. [Emphasis added.]

The development of cheap electricity during the later part of the 19th =
century, was=20
followed by the first commercial electrolysis of chloride solutions for =
the production of=20
sodium chlorate by the French in 1866. As a result of this process large =
amounts of=20
chlorates became available at reasonable cost. It soon followed that =
because chlorate=20
mixtures had "at all times fascinated inventors on account of the large =
amount of oxygen=20
stored up in ***~ chlorate(s), which can be given off so readily," these =
cheap and=20
readably available chlorates (sodium, potassium-n, ammonium) were soon =
used for the=20
production of explosives. In 1890, electrolysis of sodium chlorate, lead =
to the production=20
of potassium and ammonium perchlorates for use in the production of =
explosives.=20
Although few of these chlorate/perchlorate based explosives ever found =
favor in this=20
country, they were widely used i!1 Europe. Their use having in all cases =
been supplanted=20
by the introduction of ammonium nitrate based blasting agents.

Because of an increasing number of accidents resulting from n the use of =
chlorate=20
explosives, the US Bureau of Mines performed "Frictional Impact" testing =
of chlorate=20
explosives between September, 1911 and February 1, 1919. [Why they took =
eight=20
years to complete these tests is not recorded!] The results were =
reported in: Bureau=20
of Mines; Tech. Paper 234, 1919.

Investigated was: "A certain potassium chlorate explosive that is used =
in the United=20
States and is designated Chlorate Explosive B." [Potassium chlorate, =
sugar, gum=20
arable]. The mixture had come under suspicion because a number of =
premature=20
explosions had occurred during its use in bituminous coal mines. Quoted =
from the=20
report are the following examples:

1. "While inserting copper needle in a charge *** the charge exploded."

2. "The charge exploded while the copper needle was being inserted in =
the charge=20
bore hole."

3. "While pushing a 12-inch cartridge into bore hole, with copper needle =
inserted=20
about 6 inches in it, *** charge exploded."

They felt that: In view of the frequency of these accidents and the =
seeming ease with=20
which they took place, not being explainable by the sensitiveness of the =

explosive itself to friction, it was considered advisable to determine, =
if possible,=20
the cause of the excessive sensitiveness to friction.

It was thought, as practically all bituminous coals contain pyrite, =
perhaps the pyrite=20
was the cause of the accidents. [Now time out for a little mineralogy -- =
Pyrite or=20
"Fools Gold" is iron-sulfide (FeS2), it can with time break down to =
form, iron oxide=20
and sulfur. Its cousin Marcasite also FeS2 decomposes rather easily into =
ferrous=20
sulfate and sulfuric acid!]

To the explosive B mixture was added coal dust (basically carbon, and =
generally not=20
considered safe with potassium chlorate, by most pyros) and finely =
ground pyrite.=20
=A2/hen the mixture was stirred with a copper needle it ignited! =
Unfortunately the paper=20
does not report any tests performed on explosive "8" without the added =
pyrite/coal=20
dust, with a copper wire.

"Pendulum friction" tests, were also performed, [This test was developed =
to replace the=20
then standard "broomstick" test i.e. beat on a sample of the explosive =
with a broomstick=20
and if it fails to detonate, or crack when tested repeatedly, it =
receives a passing grade!]=20
on various chlorate explosives, however they failed to repeat the same =
tests with=20
either pyrite and/or coal added, and then compare the results. Despite =
these=20
shortcomings it was concluded that the detonation of the explosive was =
due to the=20
increase in "Friction Sensitivity" as a result of the added pyrite. In =
light of current=20
information it would appear that the real cause of the premature =
ignition may have=20
been the copper wire!

Due to shortages of raw materials during WW II, large amounts of =
chlorates=20
and perchlorates were produced. As a result the US Bureau of Mines felt=20
that at war's end: "Promoters may seek to market explosives containing=20
these ingredients, ***" Therefore in December 1945, they issued =
Information=20
Circular #7340; Hazards from Chlorates and Perchlorates in Mixtures with =

Reducing Materials.

One part of this report is of interest. Due to a fatal accident that =
occurred=20
during the manufacture of practice land mines. A sample of the material=20
[ingredients not stated, other than the fact that it contained potassium =
n=20
perchlorate, possible the military potassium perchlorate, barium =
nitrate,=20
aluminum flash mixture.] was tested in a "pressure friction apparatus."

The test:
consists essentially of a cylindrical brass plunger that exerts a=20
fixed pressure and rotates at a fixed speed upon a small=20
weight of the sample contained in a brass cup. Only materials=20
exceedingly sensitive to friction, such as the initiating=20
explosives, will fire in this test. The mixture ignited during the=20
test and was found to have a friction sensitivity slightly less=20
than that of mercury fulminate. [Emphasis added.]

Once again the source of ignition may have been copper ions from the=20
brass!

Although hard evidence is lacking, it would seem certain that careful =
pyros=20
will avoid using copper dust, in any of their comps. And will refrain =
from n=20
using copper/brass screens when processing mixtures containing chlorates =

if not perchlorates. In the older literature there can be found stars =
made=20
using combinations of potassium chlorate, and sulfur, along with various =

copper salts (copper sulfate, etc.) these are not recommended for use, =
as=20
even then they had a bad reputation.

Mixtures containing Sulphur and a Chlorate, Black oxide of=20
Copper or Sulphide of Copper (and probable all Sulphides and=20
Sulphites) with chlorate should be avoided. Purple fires which=20
generally contain one of the above compounds of Copper have=20
an especially bad name for going off spontaneously. - C.T.=20
Brock, 1872.