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

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

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

ground with purified sulfur [a brave move], the mixture detonated=20spontaneously after being let stand undisturbed on a shelf for only =thirty=20minutes! The experiment was repeated using the same components,=20simply placed in a plastic vial and mixed by "tumbling the vial =approximately=20ten minutes about its major axes." After approximately twenty-four hours =of=20standing behind a barricade, a similar detonation occurred. [A less=20complete 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=20spectacular, the finding that a potassium chlorate could be made which=20when ;nixed with sulfur is spontaneously detonable at room temperature=20there is a byproduct(s) of this experiment."

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

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

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

was strongly catalyzed by powdered copper metal or cupric oxide, and to =a=20lesser 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=20equipment of the AMMONIUM perchlorate plant of Western=20Electrochemical Company (now American Potash dc=20Chemical Corporation) were found to have been caused when=20the perchlorate crystals came into contact with copper tubing=20in the vibrating pan-dryer heat exchanger. When stainless=20steel was substituted for copper the fires ceased. Ammonium=20perchlorate was found to be most sensitive to ignition at a=20moisture content of 0.02 to 0.5 per cent, [how dry are your=20stars?], particularly when it is contaminated with copper and=20possibly in the presence of other metallic contaminants. This=20experience confirms other reports of the accelerating effect of=20copper 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=20followed by the first commercial electrolysis of chloride solutions for =the production of=20sodium chlorate by the French in 1866. As a result of this process large =amounts of=20chlorates became available at reasonable cost. It soon followed that =because chlorate=20mixtures had "at all times fascinated inventors on account of the large =amount of oxygen=20stored up in ***~ chlorate(s), which can be given off so readily," these =cheap and=20readably available chlorates (sodium, potassium-n, ammonium) were soon =used for the=20production of explosives. In 1890, electrolysis of sodium chlorate, lead =to the production=20of potassium and ammonium perchlorates for use in the production of =explosives.=20Although few of these chlorate/perchlorate based explosives ever found =favor in this=20country, they were widely used i!1 Europe. Their use having in all cases =been supplanted=20by the introduction of ammonium nitrate based blasting agents.

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

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

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

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

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

It was thought, as practically all bituminous coals contain pyrite, =perhaps the pyrite=20was 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=20and sulfur. Its cousin Marcasite also FeS2 decomposes rather easily into =ferrous=20sulfate and sulfuric acid!]

To the explosive B mixture was added coal dust (basically carbon, and =generally not=20considered 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=20does not report any tests performed on explosive "8" without the added =pyrite/coal=20dust, with a copper wire.

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

Due to shortages of raw materials during WW II, large amounts of =chlorates=20and perchlorates were produced. As a result the US Bureau of Mines felt=20that at war's end: "Promoters may seek to market explosives containing=20these ingredients, ***" Therefore in December 1945, they issued =Information=20Circular #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=20during the manufacture of practice land mines. A sample of the material=20[ingredients not stated, other than the fact that it contained potassium =n=20perchlorate, possible the military potassium perchlorate, barium =nitrate,=20aluminum flash mixture.] was tested in a "pressure friction apparatus."

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

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

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

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

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

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