Ammonium perchlorate can be used to produce excel-so a liquid state is not produced - the solid starting material lent colors, with little solid residue, but care must be exercised goes directly to gaseous decomposition products.
The decom-
at all times with this oxidizer. The explosive properties of this position reaction is reported by Shimizu [2] to be material suggest that minimum amounts of bulk composition should be prepared at one time, and large quantities should not be stored 2 NH,,C104 heat N2 +3H 2 0+2HC1+2.50 2
at manufacturing sites.
This equation corresponds to the evolution of 80 grams (2.5
moles) of oxygen gas per 2 moles (235 grams) of NH I C1O,, , Strontium Nitrate [Sr(NO3)2]
giving an "active oxygen" content of 34% (versus 39.2% for KC1O
This material is rarely used as the only oxidizer in a composition, 3
and 46.2% for KC10,,).
The decomposition reaction,
above 350 1 C, is reported to be considerably more complex [9].
but is commonly combined with potassium perchlorate in red flame mixtures. It is a white crystalline solid with a melting point of heat,
10 NH,,C10,,
2.5 C1
approximately 570°C. It is somewhat hygroscopic, so moisture 2
+ 2 N 2 0 + 2.5 NOC1 + HC10 4
should be avoided when using this material.
+1.5HC1+18.75H 2 O+1.75N 2 +6.3802
Near its melting point, strontium nitrate decomposes accord-Mixtures of ammonium perchlorate with fuels can produce high ing to
temperatures when ignited, and the hydrogen chloride (HCl) lib-Sr(NO 3 ) 2 -} SrO + NO + NO 2 + 0 2
erated during the reaction can aid in the production of colors.
These two factors make ammonium perchlorate a good oxidizer Strontium nitrite - Sr(N0 2 ) 2 - is formed as an intermediate in for colored flame compositions (see Chapter 7).
this decomposition reaction, and a substantial quantity of the ni-Ammonium perchlorate is more hygroscopic than potassium trite can be found in the ash of low flame temperature mixtures nitrate or potassium chlorate, and some precautions should be
[2].
At higher reaction temperatures, the decomposition is
62
Chemistry of Pyrotechnics
Components of High-Energy Mixtures
63
Sr(NO 3 ) 2 -> SrO + N 2 + 2.5 0 2
which later melts at 41_4 0 C.
The thermal decomposition of barium
This is a strongly endothermic reaction, with a heat of reaction chlorate is strongly exothermic (-28 kcal/mole). This value, con-of +92 kcal, and corresponds to an active oxygen content of siderably greater than that of potassium chlorate, causes barium 37.7%.
Little ash is produced by this high-temperature process, chlorate mixtures to be very sensitive to friction, heat, and other which occurs in mixtures containing magnesium or other "hot"
ignition stimuli.
fuels
Iron oxide (hematite, Fe 2 0 3 ) is used in certain mixtures where a high ignition temperature and a substantial quantity of molten slag (and lack of gaseous product) are desired. The thermite re-Barium Nitrate [Ba(N03)2]
action ,
Barium nitrate is a white, crystalline, non-hygroscopic material Fe2O3+2Al- A1
with a melting point of approximately 592°C. It is commonly used 2O 3 +2Fe
as the principal oxidizer in green flame compositions, gold spark-is an example of this type of reaction, and can be used to do pyro-lers, and in photoflash mixtures in combination with potassium technic welding.
The melting point of Fe 20 3 is 1565°C, and the pert hlorate .
ignition temperature of thermite mix is above 800 0 C.
A reaction
At high reaction temperatures, barium nitrate decomposes ac-temperature of approximately 2400°C is reached, and 950 calories cording to
of heat is evolved per gram of composition [2, 51.
Other oxidizers, including barium chromate (BaCrO,,), lead Ba(NO 3 ) 2 -+ BaO + N 2 + 2.5 0 2
chromate (PbCrO 4) , sodium nitrate (NaNO 3), lead dioxide (Pb0 2) , This reaction corresponds to 30.6% available oxygen. At lower and barium peroxide (Ba0 2) will also be encountered in subse-reaction temperatures, barium nitrate produces nitrogen oxides quent chapters. Bear in mind that reactivity and ease of igni-
(NO and NO
tion are often related to the melting point of the oxidizer, and the 2 ) instead of nitrogen gas, as does strontium nitrate 21.
volatility of the reaction products determines the amount of gas Mixtures containing barium nitrate as the sole oxidizer are that will be formed from a given oxidizer /fuel combination. Table typically characterized by high ignition temperatures, relative 3.2 contains the physical and chemical properties of the common to potassium nitrate and potassium chlorate compositions. The oxidizers, and Table 5.8 lists the melting and boiling points of higher melting point of barium nitrate is responsible for these some of the common reaction products.
higher ignition values.
Shidlovskiy has pointed out that metal-fluorine compounds should also have good oxidizer capability. For example, the reaction
Other Oxidizers
FeF
A variety of other oxidizers are also occasionally used in high-3 + Al } A1F 3 + Fe
energy mixtures, generally with a specific purpose in mind.
is quite exothermic (z~H = -70 kcal). However, the lack of stable, Barium chlorate - Ba(C10 3 ) 2 - for example is used in some economical metal fluorides of the proper reactivity has limited re-green flame compositions. These mixtures can be very sensi-search in this direction [ 1] .
tive, however, and great care must be used during mixing, loading, and storing. Barium chlorate can be used to produce a beautiful green flame, though.
FUELS
Barium chlorate is interesting because it exists as a hydrate Requirements
when crystallized from a water solution. It has the formula Ba(C10
In addition to an oxidizer, pyrotechnic mixtures will also contain 3 ) 2 • H 2 O.
Water molecules are found in the crystalline lattice in a one-to-one ratio with barium ions. The molecular a good fuel - or electron donor - that reacts with the liberated weight of the hydrate is 322.3 (Ba + 2
+ H 2O), so the wa-
oxygen to produce an oxidized product plus heat. This heat will CIO 3
ter must be included in stoichiometry calculations. On heating, enable the high-energy chemist to produce any of a variety of the water is driven off at 120°C, producing anhydrous Ba(C103)2, possible effects - color, motion, light, smoke, or noise.
6 4