works technology over the past several centuries have come Although black powder has been replaced in most of its for-from these two Asian nations.
mer uses by newer, better materials, it is important to recog-The noted English scientist Roger Bacon was quite familiar nize the important role it has played in modern civilization.
with potassium nitrate/charcoal/sulfur mixtures in the 13th cen-Tenney Davis, addressing this issue in his classic book on the tury, and writings attributed to him give a formula for preparing chemistry of explosives, wrote "The discovery that a mixture of
"thunder and lightning" composition [5]. The use of black pow-potassium nitrate, charcoal, and sulfur is capable of doing useder as a propellant for cannons was widespread in Europe by the ful work is one of the most important chemical discoveries or in-14th century.
ventions of all time ... the discovery of the controllable force of Good-quality black powder was being produced in Russia in gunpowder, which made huge engineering achievements possible, the 15th century in large amounts, and Ivan the Terrible report-gave access to coal and to minerals within the earth, and brought edly had 200 cannons in his army in 1563 [6]. Fireworks were on directly the age of iron and steel and with it the era of ma-being used for celebrations and entertainment in Russia in the chines and of rapid transportation and communication" [5].
17th century, with Peter the First among the most enthusiastic Explosives are widely used today throughout the world for supporters of this artistic use of pyrotechnic materials.
mining, excavation, demolition, and military purposes. Pyro-By the 16th century, black powder had been extensively stud-technics are also widely used by the military for signalling and ied in many European countries, and a published formula dating training. Civilian applications of pyrotechnics are many and to Bruxelles in 1560 gave a 75.0/15.62/9.38 ratio of saltpeter/
varied, ranging from the common match to highway warning charcoal /sulfur that is virtually the same as the mixture used flares to the ever-popular fireworks.
today [51!
The fireworks industry remains perhaps the most visible ex-The use of pyrotechnic mixtures for military purposes in rifles, ample of pyrotechnics, and also remains a major user of tradi-rockets, and cannons developed simultaneously with the civilian tional black powder. This industry provides the pyrotechnician applications such as fireworks. Progress in both areas followed with the opportunity to fully display his skill at producing col-advances in modern chemistry, as new compounds were isolated ors and other brilliant visual effects.
and synthesized and became available to the pyrotechnician.
Fireworks form a unique part of the cultural heritage of many Berthollet's discovery of potassium chlorate in the 1780's resulted countries [7]. In the United States, fireworks have traditionally in the ability to produce brilliant flame colors using pyrotechnic been associated with Independence Day - the 4th of July. In compositions, and color was added to the effects of sparks, noise, England, large quantities are set off in commemoration of Guy and motion previously available using potassium nitrate-based Fawkes Day (November 5th), while the French use fireworks compositions. Chlorate -containing color-producing formulas were extensively around Bastille Day (July 14th). In Germany, the known by the 1830's in some pyrotechnicians' arsenals.
use of fireworks by the public is limited to one hour per year -
The harnessing of electricity led to the manufacturing of mag-from midnight to 1 a.m. on January 1st, but it is reported to be nesium and aluminum metals by electrolysis in the latter part of quite a celebration. Much of the Chinese culture is associated the 19th century, and bright white sparks and white light could with the use of firecrackers to celebrate New Year's and other
6
Chemistry of Pyrotechnics
A*
important occasions, and this custom has carried over to Chinese communities throughout the world. The brilliant colors and booming noises of fireworks have a universal appeal to our basic senses.
To gain an understanding of how these beautiful effects are produced, we will begin with a review of some basic chemical principles and then proceed to discuss various pyrotechnic systems.
REFERENCES
1.
U.S. Army Material Command, Engineering Design Handbook, Military Pyrotechnic Series, Part One, "Theory and Application," Washington, D.C., 1967 (AMC Pamphlet 706-185).
2.
J. R. Partington, A History of Greek Fire and Gunpowder, W. Heffer and Sons Ltd. , Cambridge, Eng. , 1960.
3.
Ding Jing, "Pyrotechnics in China," presented at the 7th International Pyrotechnics Seminar, Vail, Colorado, July, 1980.
4.
T. Shimizu, Fireworks - The Art, Science and Technique,
pub. by T. Shimizu, distrib. by Maruzen Co., Ltd., Tokyo, 1981.
5.
T. L. Davis, The Chemistry of Powder and Explosives, John Wiley & Sons, Inc., New York, 1941.
6.
A. A. Shidlovskiy, Principles of Pyrotechnics, 3rd Edition, Moscow, 1964. (Translated as Report FTD-HC-23-1704-74
by Foreign Technology Division, Wright-Patterson Air Force Base, Ohio, 1974.)
7.
G. Plimpton, Fireworks:
A History and Celebration, Double-
day, New York, 1984.
A grain of commercially-produced black powder, magnified 80 times.
Extensive mixing and grinding of moist composition produces a homogeneous mixture of high reactivity. A mixture of the same three components-potassium nitrate, sulfur, and charcoal-that is prepared by briefly stirring the materials together will be much less reactive.
(J. H. McLain files)
2BASIC CHEMICAL PRINCIPLES
ATOMS AND MOLECULES
To understand the chemical nature of pyrotechnics, one must begin at the atomic level. Two hundred years of experiments and calculations have led to our present picture of the atom as the fundamental building block of matter.
An atom consists of a small, dense nucleus containing positively-charged protons and neutral neutrons, surrounded by a large cloud of light, negatively-charged electrons. Table 2.1
summarizes the properties of these subatomic particles.
A particular element is defined by its atomic number - the number of protons in the nucleus (which will equal the number of electrons surrounding the nucleus in a neutral atom). For example, iron is the element of atomic number 26, meaning that every iron atom will have 26 protons in its nucleus. Chemists use a one or two-letter symbol for each element to simplify communication; iron is given the symbol Fe, from the old Latin word for iron, ferrum. The sum of the protons plus neutrons found in a nucleus is called the mass number. For some elements only one mass number is found in nature. Fluorine (atomic number 9, mass number 19) is an example of such an element. Other elements are found in nature in more than one mass number. Iron is found as mass number 56 (91.52%), 54 (5.90%), 57 (2.245%), and 58 (0.33%) . These different mass numbers of the same element are called isotopes, and vary in the number of neutrons found in the nucleus. Atomic weight refers to the average mass found in nature of all the atoms of a particular element; the atomic weight of iron is 55.847. For calculation purposes, these 7
8
Chemistry of Pyrotechnics
Basic Chemical Principles
9
TABLE 2.1 Properties of the Subatomic Particles TABLE 2.2 Symbols, Atomic Weights, and Atomic Numbers of the Elements
Particle
Location
Charge
Mass, amusa
Mass, grams
-24
Atomic
Atomic weight,
Proton
In nucleus
+1
1.007
1.673 X 10