Other Oxidizers
A variety of other oxidizers are also occasionally used in highenergy mixtures, generally with a specific purpose in mind. Barium chlorate - Ba(C10 3 ) 2 - for example is used in some green flame compositions. These mixtures can be very sensitive, however, and great care must be used during mixing, loading, and storing. Barium chlorate can be used to produce a beautiful green flame, though.
Barium chlorate is interesting because it exists as a hydrate when crystallized from a water solution. It has the formula Ba(C103 ) 2 • H2O. Water molecules are found in the crystalline lattice in a one-to-one ratio with barium ions. The molecular weight of the hydrate is 322.3 (Ba + 2 CIO 3 + H 2O), so the water must be included in stoichiometry calculations. On heating, the water is driven off at 120°C, producing anhydrous Ba(C103)2, which later melts at 41_4 0C. The thermal decomposition of barium chlorate is strongly exothermic (-28 kcal/mole). This value, considerably greater than that of potassium chlorate, causes barium chlorate mixtures to be very sensitive to friction, heat, and other ignition stimuli.
Iron oxide (hematite, Fe 20 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 reaction,
is an example of this type of reaction, and can be used to do pyrotechnic welding. The melting point of Fe 20 3 is 1565°C, and the ignition temperature of thermite mix is above 800°C. A reaction temperature of approximately 2400°C is reached, and 950 calories of heat is evolved per gram of composition.
Other oxidizers, including barium chromate (BaCrO,,), lead chromate (PbCrO 4) , sodium nitrate (NaNO 3), lead dioxide (Pb0 2 ), and barium peroxide (Ba0 2 ) will also be encountered in subsequent chapters. Bear in mind that reactivity and ease of ignition are often related to the melting point of the oxidizer, and the volatility of the reaction products determines the amount of gas that will be formed from a given oxidizer /fuel combination.
Shidlovskiy has pointed out that metal-fluorine compounds should also have good oxidizer capability. For example, the reaction
is quite exothermic (z~H = -70 kcal). However, the lack of stable, economical metal fluorides of the proper reactivity has limited research in this direction.