322. 3
414
27 (15 0 )
-28b
-184.4
. 095
10.6
Barium chromate
B aCrO,,
253.3
Decomposes
. 0003 (16°)
- 345.6
8.7
+104b
-237.1
. 31
3.27
Barium nitrate
Ba(N03)2
261.4
592
Very slight
+17b
-151.6
. 09
10.6
Barium peroxide
Ba0
169.3
450
2
. 30
3.33
Iron oxide (red)
Fe 20 3
159.7
1565
Insol.
-197.0
. 28
3.62
Iron oxide (black)
Fe 3 0 y
231.6
1594
Insol.
+266 b
-267.3
Insol.
-218
. 074
13.5
Lead chromate
Pb C r0,,
323.2
844
Insol.
-66.3
. 13 (total 0)
7.48
Lead dioxide
PbO 2
239.2
290 (decomposes)
(lead peroxide)
. 072 (total 0)
14.0
Lead oxide
PbO
223.2
886
. 0017
-51.5
(litharge)
Insol.
-171.7
. 093 (total 0)
10.7
Lead tetroxide
Pb 3 0
685.6
500 (decomposes)
4
(red lead)
7.1
-10.6c
-95.1
. 39
2.55
Potassium chlorate
KC1O 3
122.6
356
31.60
+75.5b
-118.2
. 40
2.53
Potassium nitrate
KNO 3
101.1
334
1.7c
-0.68c
-103.4
. 46
2.17
Potassium per-
K C 10
138.6
610
4
chlorate
92.1 (25 ° ) e
+60.5 b
-111.8
. 47
2.13
Sodium nitrate
NaN0 3
85.0
307
70.9 (18°)
+92c
-233.8
. 38
2.63
Strontium nitrate
Sr(N 0 3)2
211.6
570
a Reference 4.
b Reference 1.
cReference 2.
5 4
Chemistry of Pyrotechnics
Components of High-Energy Mixtures
55
3. The alkali metals (Li, Na, K) and alkaline earth metals additional details on the properties of these and other pyrotech-
(Ca, Sr, and Ba) are preferred for the positive ion.
nic materials [1, 2, 3].
These species are poor electron acceptors (and con-versely, the metals are good electron donors), and they will not react with active metal fuels such as Mg and Al.
Potassium Nitrate (KNO 3 )
If easily reducible metal ions such as lead (Pb +2) and The oldest solid oxidizer used in high-energy mixtures, potassium copper (Cu +2) are present in oxidizers, there is a strong nitrate (saltpeter) remains a widely-used ingredient well into the possibility that a reaction such as
20th century. Its advantages are ready availability at reasonable Cu(N0
cost, low hygroscopicity, and the relative ease of ignition of many 3 ) 2 + Mg -> Cu + Mg(NO 3 ) 2
mixtures prepared using it. The ignitibility is related to the low will occur, especially under moist conditions. The pyro-
(334°C) melting point of saltpeter. It has a high (39.6%) active technic performance will be greatly diminished, and spon-oxygen content, decomposing at high temperature according to taneous ignition might occur.
the equation
I
4. The compound must have an acceptable heat of decomposition. A value that is too exothermic will produce explo-2KNO 3 + K 2O+N 2 +2.502
sive or highly sensitive mixtures, while a value that is This is a strongly endothermic reaction, with a AH value of +75.5
too endothermic will cause ignition difficulties as well as kcal/mole of KNO 3 , meaning high energy-output fuels must be poor propagation of burning.
used with saltpeter to achieve rapid burning rates. When mixed 5. The compound should have as high an active oxygen con-with a simple organic fuel such as lactose, potassium nitrate may tent as possible. Light cations (Na+, K+, NH,,+) are de-stop at the potassium nitrite (KNO 2 ) stage in its decomposition [2].
sirable while heavy cations (Pb +2 , Ba +2) should be avoided if possible. Oxygen-rich anions, of course, are preferred.
KNO 3 } KNO2 + 1/2 0 2
6. Finally, all materials used in high-energy compositions With good fuels (charcoal or active metals) , potassium nitrate will should be low in toxicity, and yield low-toxicity reaction burn well. Its use in colored flame compositions is limited, pri-products.
marily due to low reaction temperatures. Magnesium may be added to these mixtures to raise the temperature (and hence the light in-In addition to ionic solids, covalent molecules containing halo-tensity), but the color value is diminished by "black body" emis-gen atoms (primarily F and Cl) can function as "oxidizers" in sion from solid MgO.