positions contain a large excess of potential fuel, and their ex-3 suggests that impurities
could be quite an important factor in determining the reactivity plosive properties are greatly diminished as a result. Smoke and ignition temperature of chlorate-containing mixtures. It is mixtures must react with low flame temperatures (500°C or less) vitally important that the KCIO
or the complex dye molecules will decompose, producing black 3 used in pyrotechnic manufacturing operations be of the highest possible purity, and that all soot instead of a brilliantly colored smoke. Potassium chlorate possible precautions be taken in storage and handling to pre-is far and away the best oxidizer for use in these compositions.
vent contamination of the material.
Potassium chlorate is truly a unique material. Shimizu has McLain has reported that potassium chlorate containing 2.8
stated that no other oxidizer can surpass it for burning speed, mole% copper chlorate as an intentionally-added impurity (or ease of ignition, or noise production using a minimum quantity
"dopant") reacted explosively with sulfur at room temperature of composition [2]. It is also among the very best oxidizers for
[7]! A pressed mixture of potassium chlorate with realgar (ar-producing colored flames, with ammonium perchlorate as its senic sulfide, As
closest rival. Chlorate-containing compositions can be prepared 2S2) has also been reported to ignite at room temperature [2].
that will ignite and propagate at low flame temperatures - a Ammonium chlorate, NH,,C10
property invaluable in colored smoke mixtures. By altering the 3 , is an extremely unstable compound that decomposes violently at temperatures well below 100 0 C.
fuel and the fuel/oxidizer ratio, much higher flame temperatures If a mixture containing both potassium chlorate and an ammonium can be achieved for use in colored flame formulations. KC10 3 is salt is prepared, there is a good possibility that an exchange re-a versatile material, but the inherent danger associated with it action will occur -- especially in the presence of moisture - to requires that alternate oxidizers be employed wherever possible.
form some of the ammonium chlorate
It is just too unstable and unpredictable to be safely used by the pyrotechnician in anything but colored smoke compositions, and NH,,X + KC1O3 HZO NH4C103 + KX
even here coolants and considerable care are required!
(X = C1- , N0 -3 , C1O,, , etc.)
Potassium Perchlorate (KCIO,,)
If this reaction occurs, the chance of spontaneous ignition of the mixture is likely. Therefore, any composition containing both a This material has gradually replaced potassium chlorate (KC10 3 ) chlorate salt and an ammonium salt must be considered extremely as the principal oxidizer in civilian pyrotechnics. Its safety rec-hazardous. The shipping regulations of the United States De-ord is far superior to that of potassium chlorate, although cau-partment of Transportation classify any such mixtures as "for-tion - including static protection - must still be used. Perchlor-bidden explosives" because of their instability [8]. However, ate mixtures, especially with a metal fuel such as aluminum, can compositions consisting of potassium chlorate, ammonium chlor-have explosive properties, especially when present in bulk quan-ide, and organic fuels have been used, reportedly safely, for tities and when confined.
white smoke production [1].
Potassium perchlorate is a white, non-hygroscopic crystalline Colored smoke compositions are a major user of potassium material with a melting point of 6101C, considerably higher than chlorate, and the safety record of these mixtures is excellent.
the 356°C melting point of KC10 3 . It undergoes decomposition at A neutralizer (e.g., MgCO
high temperature
3 or NaHCO 3 ) is typically added for
storage stability, as well as to lower the reaction temperature heat
KC1O,,
KC1 + 2 0 2
60
Chemistry o f Pyrotechnics
Components of High-Energy Mixtures
61
forming potassium chloride and oxygen gas. This reaction has taken to keep mixtures dry. The hygroscopicity problem can be a slightly exothermic value of -0.68 kcal/mole [2] and produces substantial if a given composition also contains potassium nitrate, substantial oxygen.
The active oxygen content of KC1O,, -
or even comes in contact with a potassium nitrate-containing mix-46.2% - is one of the highest available to the pyrotechnician.
ture.
Here, the reaction
Because of its higher melting point and less-exothermic de-H?O
composition, potassium perchlorate produces mixtures that are NH L C1O k + KNO3
KC1O y + NH„NO 3
less sensitive to heat, friction, and impact than those made can occur, especially in the presence of moisture. The exchange with KC1O 3 [2].
Potassium perchlorate can be used to pro-
product, ammonium nitrate (NH,,N0 3 ) is very hygroscopic, and duce colored flames (such as red when combined with stron-ignition problems may well develop [2]. Also, ammonium per-tium nitrate), noise (with aluminum, in "flash and sound"
chlorate should not be used in combination with a chlorate-con-mixtures), and light (in photoflash mixtures with magnesium).
taining compound, due to the possible formation of unstable ammonium chlorate in the presence of moisture.
Ammonium Perchlorate (NH,,CIO,,)
Magnesium metal should also be avoided in ammonium perchlorate compositions.
Here, the reaction
The "newest" oxidizer to appear in pyrotechnics, ammonium perchlorate has found considerable use in modern solid-fuel rocket 2 NH,,C10,, + Mg } 2 NH 3 + Mg(Cl0 4 ) 2 + H 2 + heat propellants and in the fireworks industry.
The space shuttle
can occur in the presence of moisture. Spontaneous ignition may alone uses approximately two million pounds of solid fuel per occur if the heat buildup is substantial.
launch; the mixture is 70% ammonium perchlorate, 16% aluminum Under severe initiation conditions, ammonium perchlorate can metal, and 14% organic polymer.
be made to explode by itself [10] . Mixtures of ammonium per-Ammonium perchlorate undergoes a complex chemical reac-chlorate with sulfur and antimony sulfide are reported to be con-tion on heating, with decomposition occurring over a wide range, siderably more shock sensitive than comparable KC1O 3 composi-beginning near 200°C.
Decomposition occurs prior to melting,
tions [2].