158
Chemistry of Pyrotechnics
Color and Light Production
159
TABLE 7.9 Red Flame Compositions
% by
Composition
weight
Use
Reference
I.
Ammonium perchlorate,
70
Red torch
6
NH,,ClO,,
Strontium carbonate,
10
SrC O 3
Wood meal (slow fuel)
20
II.
Potassium perchlorate,
67
Red fireworks
6
K C 10,,
star
Strontium carbonate,
13.5
SrCO 3
Pine root pitch
13.5
Rice starch
6
III.
Potassium perchlorate,
32.7
Red fireworks
9
KCIO,,
star
Ammonium perchlorate,
28.0
NH„ CIO,,
Strontium carbonate,
16.9
SrCO 3
FIG. 7.1 Emission spectrum of a red flare. Emission is concen-Red gum
14.0
trated in the 600-700 nm region. The primary emitting species Hexamethylenetetra-2.8
are SrCI and SrOH molecules in the vapor state. The composi-mine, C 6 H 12 N,,
tion of the flare was potassium perchlorate (20.5%) , strontium ni-Charcoal
1.9
trate (34.7%), magnesium (24.4%), polyvinylchloride (11.4%), and Dextrine (dampen with
3.7
asphaltum (9.0%). Source : H. A. Webster III, "Visible Spectra 3:1 water/alcohol)
of Standard Navy Colored Flares," Proceedings, Explosives and IV.
Potassium perchlorate,
44
Red signal
Unpublished
Pyrotechnics Applications Section, American Defense Preparedness KClO,,
flare (very
Association, Fort Worth, Texas, September, 1983.
Strontium nitrate,
31
little residue)
Sr(NO3)2
Epoxy fuel/binder
25
the 505-535 nanometer region of the visible spectrum - the "deep green" portion [1, 11]. The emission spectrum of a green flare was shown in Figure 4. 1.
Barium nitrate - Ba(NO 3) 2 - and barium chlorate - Ba(C 1 03)2 -
are used most often to produce green flames, serving both as the high decomposition temperature and endothermic heat of decomposition.
oxidizer and color source. Barium chlorate can produce a deep Barium carbonate (BaCO 3 ) is another possibility, but it green, but it is somewhat unstable and can form explosive mix-must be used in low percentage due to its inert anion, CO 3 .
tures with good fuels. Barium nitrate produces an acceptable An oxygen-deficient flame is required for a good-quality green green color, and it is considerably safer to work with due to its flame. Otherwise, barium oxide (BaO) will form and emit a series
160
Chemistry of Pyrotechnics
Color and Light Production
161
of bands in the 480-600 nanometer range, yielding a dull, yellow-TABLE 7.10 Green Flame Compositions
ish-green color. The reaction
2 BaCl + 0
% by
2 ~ 2 BaO + C1 2
Composition
weight
will shift to the left-hand side when chlorine is present in abun-Use
Reference
dance and oxygen is scarce, and a good green color will be I.
Ammonium perchlorate,
50
Green torch
6
achieved. A flame temperature that is too high will decompose N H,,C1O,,
BaCl, however, so metal fuels must be held to a minimum, if they Barium nitrate,
34
are used at all. A "cool" flame is best.
Ba(N0
This temperature dependence and need for chlorine source are 3)2
Wood meal
8
important to remember. A binary mixture of barium nitrate and Shellac
8
magnesium metal will produce a brilliant white light upon ignition, from a combination of MgO and BaO emission at the high tempera-II. Barium chlorate,
65
Green torch
Unpublished
ture achieved by the mixture. Addition of a chlorine-containing Ba(Cl0 3) 2 - H 20
organic fuel to lower the temperature and provide chlorine atoms Barium nitrate,
25
to form BaCI can produce a green flame. Several green flame Ba(NO3)2
compositions are given in Table 7. 10.
Red gum
10
III. Potassium perchlorate,
46
Green fireworks
6
Blue Flame Compositions
KC10y
star
Barium nitrate,
32
The generation of an intense, deep-blue flame represents the ulti-Ba(N0
mate challenge to the pyrotechnic chemist. A delicate balance of 3 ) 2
Pine root pitch
16
temperature and molecular behavior is required to obtain a good Rice starch
6
blue, but it can be done if the conditions are right.
The best flame emission in the blue region of the visible spec-IV. Barium nitrate,
59
Russian green
5
trum (435-480 nanometers) is obtained from copper monochloride, Ba(N 0 3)2