Pyrotechnics, Rocketry & Explosive Science

Chemistry and Technology of Explosives Vol. 1-4

For quite a long time a reference book has been needed which would provide the reader with adequate information, both theoretical and practical, on the chemistry and technology of explosives. The objectives of the present book are to fill this gap in the chemical literature.

The first edition appeared in Warsaw in Polish in 1953-54. The second, in Czech, was printed in Prague in 1958-59. The third, in German, is being printed in Leipzig. The present fourth edition is a considerably revised and expanded version of the earlier ones.

The chemical, physical and physico-chemical properties of explosives are dealt with, and processes of manufacture are described whenever the substance in question is of practical importance.

The basis of all practical knowledge is in the underlying theory. The scientist working on technological problems in industry should never forget that science, however applied, remains a natural philosophy. This is why particular attention is paid here to the chemical and physico-chemical properties of the substances described in the book, and the author has endeavoured to bring this information up to date, hoping that the wide scope of this information will not obscure the main subject, but will help, instead, to avoid narrow specialization which creates the danger of not seeing the wood for the trees.

It is also hoped that in widening the scope of the book, it might become useful not only to students and experts on explosives, but also to all who are interested in the chemistry of such substances as nitro compounds, nitramines, nitric esters, nitric salts, azides etc. that may serve as intermediates for organic reactions.

As far as processes of manufacture of explosives are concerned, information is obviously restricted, as the exact details are seldom available. However, certain obsolete methods of manufacture are described in detail. They have been included in order to give some idea of the way such processes have developed on the basis of years of experience. This may be of some value, for the manufacture of explosives is bound to be dangerous and any method, even an obsolete one, may suggest how risks can be avoided or diminished and the kinds of precaution that can be applied.

However, it has been possible to include in the book details of a number of original processes used in the German and Japanese explosives industries during World War II which were revealed after the war mainly in CIOS, BIOS, FIAT and PB publications.

Although there was an enormous increase in the use of explosives for destructive purposes in the two World Wars it is still true to say that more explosives have been used in peace than in war. Modern civilization and modern progress would be impossible without explosives. Particular attention has therefore been paid to coal-mine explosives (Vol. III). Also a modest chapter on rocket fuels has been included in the English edition.

CLASSIFICATION OF EXPLOSIVES
EXPLOSIVES may be classified both from the chemical point of view and according to their uses. From the chemical viewpoint we distinguish between chemical individual substances and mixtures.

The former are divided into:
(1) nitro compounds
(2) nitric esters
(3) nitramines
(4) derivatives of chloric and perchloric acids
(5) azides
(6) various compounds capable of producing an explosion, for example fulminates, acetylides, nitrogen rich compounds such as tetrazene, peroxides and ozonides, etc.

Individual substances are explosive if their molecules contain groups which confer upon them explosive properties. The first attempt at a systematic approach to the relation between the explosive properties of a molecule and its structure was made by van’t Hoff [l]. He pointed out, that in the molecules of explosive compounds the following groups were present:

O-O in peroxides and ozone and ozonides
O-Cl in chlorates and perchlorates
N-Cl in nitrogen chloride
N=O in nitro compounds, nitric acid esters and salts
N=N in diazo compounds, hydrazoic acid, its salts and esters
N=C in fulminates and cyanogen
CEC in acetylene and acetylides.

A further effort to establish a relationship between explosive properties and structure has been made more recently by Plets [2]. He proposed a theory of “explosophores” and “auxoploses” in a way analogous to Witt’s suggested chromophores and auxochromes in the dyes, and Ehrlich’s suggested toxophores and autotoxes in chemotherapeutics.

According to Plets the explosive properties of any substance depend upon the presence of definite structural groupings, called explosophores. The auxoploses fortify or modify the explosive properties conferred by the explosophore. Plets divided all explosives into eight classes containing the following groups as explosophores:

(1) -NO2 and -ONO2, in both inorganic and organic substances
( 2 ) – N = N – a n d -N=N=N- in inorganic and organic azides
(3) –NX2, for example in NCl3 (X- a halogen)
(4) -N=C in fulminates
(5) -OC1O2 and -OC1O3 in inorganic and organic chlorates and perchlorates
respectively
(6) -O-O- and -O-O-O- in inorganic and organic peroxides
and ozonides respectively
(7) -CEC- in acetylene and metal acetylides
(8) M-C metal bonded with carbon in some organometallic compounds.

Although this classification is in principle correct, the distinction between the terms “explosophore” and “auxoplose” is very vague and of little practical value. A further step in the classification of explosives was made by Lothrop and Handrick [3]. They collected and classified all the available information on the performance of explosives and related it to four factors: oxygen balance, “plosophoric” groups, “auxoplosive” groups, heat of explosion.

A plosophore has been defined as a group of atoms which is capable of forming an explosive compound on introduction into a hydrocarbon. According to these authors there are two classes of plosophores differing sharply in effectiveness and consistency in producing power. Hence it is suggested that these be called “primary” and “secondary” plosophores.

Primary plosophores include nitrate esters, aromatic and aliphatic nitro groups and the nitramine group.

The secondary plosophores that comprise the remainder include such groups as azo, azide, nitroso, peroxide, ozonide, perchlorate, etc.

If more than one type of these groups is present such a molecule may be named a hybrid according to Lothrop and Handrick. Groups which do not themselves produce explosive properties, but may influence them in the same way that auxochromic groups vary the colour intensity and shade of a dye, are called auxoplosives by these authors. We may quote hydro- XY~, carboxyl, chlorine, sulphur, ether, oxygen, amine, etc. as examples of such groups.

* Although the classification of groups existing in explosive molecules suggested by Lothrop and Handrick may be accepted, their far-reaching postulations concerning a close relation between the oxygen balance and performance of explosives aroused strong criticism [4]. It is known that the oxygen present, for example, in carbonyl or hydroxyl groups, has little effect on the performance of an explosive. This is due to the high heat of formation of C-O and C-O-H bonds. On the contrary, the low (negative) heats of formation of N–O and CEC bonds are of great significance in relation to the performance of explosives.

That is the reason why the performance of picric acid (trinitrophenol) is only vary slightly higher than that of trinitrobenzene and why the performance of trinitroanisole is much the same as that of trinitrotoluene.

The low value of the explosive power of oxygen atoms bonded with carbon and hydrogen atoms in such a group as COOH had already been stressed by Stettbather [5], who also pointed out that an exception is provided by peroxides and ozonides which form exothermic bonds that considerably enhance explosive performance. However, the slightly better performance of picric acid compared with trinitrobenzene is probably the result of the former’s greater ability to detonate. The ease of detonation of picric and styphnic acids as compared with trinitrobenzene is well known. D. Smolenski and Czuba [6] recently pointed out that dinitrophenol detonates more readily than dinitrobenzene.

It is also well known from the classic work of L. Wöhler and Wenzelberg [7] that the sensitivity to impact of aromatic nitro compounds increases with increase in the number of substituents for a given member of the nitro groups. Explosive mixtures can be divided into:

(1) those with at least one explosive component
(2) others where there is no explosive component.

The classification of mixtures will be dealt with in detail in Vol. III. According to their uses explosives are divided into high explosives, propellants (‘low explosives”) and primary explosives or initiators.

High explosives may be class&d according to their physical properties as powdery, meltable, semi-meltable and plastic. Propellants may be grouped on the basis of chemical composition into gun powder and similar mixtures, nitrocellulose (single base) and nitroglycerine (double base) powders. With respect to their uses and some properties they are divided into black powder, smokeless and flashless powders, and rocket propellants.

Primary explosives and their mixtures are divided into those used for filling ignition caps and those used in detonators.





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