It is a generation since a dictionary of explosives has been published, and, in the meantime, many new explosives have been introduced. It is hoped, therefore, that this small volume, giving concise information about these special materials, may prove useful to those who have to deal with them. In Cundill and Thomson’s “Dictionary of Explosives,” issued in 1895, there are many entries of the names of inventors and of mixtures which had been proposed but have never been used commercially, nor are likely to be. As modern explosives were then in their infancy, it was no doubt wise to insert all the available information whether it appeared to be important or not; but now it seems to me better to restrict the scope of the dictionary so as to keep its size within moderate limits. Practically only explosives with special or proprietary names are therefore dealt with here. For information concerning chemical substances, such as the nitro-toluenes and other nitro-compounds, reference should be made to the textbooks on explosives and chemistry.

A few words may, however, be said here about the nitrocelluloses. These are made by treating cellulose with a mixture of nitric and sulphuric acids, and then purifying the product by washing it thoroughly with hot water. The variety of cellulose most used for this purpose is cotton, and the product obtained from it is frequently called nitrocotton, three special varieties of which are collodion cotton, pyrocollodion and guncotton (q. v.). The only other form of cellulose which is nitrated on a commercial scale is “chemical cellulose” obtained by the treatment of wood or straw. Nitrated wood cellulose has long been used for the manufacture of smokeless powders for shot-guns, and during the War the Germans made powders for rifled fire-arms from it.

No trouble has been spared to make the dictionary complete and accurate, but there must inevitably be omissions and errors in it, especially as regards the explosives of foreign countries. The author will be grateful for any additional information that may be sent him.

Explosives may be classified in various ways, according to the purpose of the classification, but the great majority of them fall naturally into two main divisions: propellants and high explosives. Propellants explode comparatively slowly, and are used to propel projectiles from fire-arms. High explosives are much more rapid in their action, and are used for bursting and shattering. Propellants are of two sorts, according as they are intended for use in shot-guns or rifled fire-arms. Those for shot-guns burn more rapidly than those for the latter, but both practically always contain a considerable proportion of nitrocellulose, gelatinised by means of such solvents as acetone or ether-alcohol, according as it is of high or low nitration. Some contain also nitroglycerine, and are then called nitroglycerine powders, whereas those that do not contain this substance are termed nitrocellulose powders. Many powders also contain other ingredients, as may be seen from the compositions given in this dictionary.

Of high explosives an important class is used for charging shells and bombs. As a rule, but not necessarily, these are not the same as the explosives used for mining operations and other general blasting purposes. Another important class is that of the coal-mine explosives, which are designed to give only a short and comparatively cool flame so as to diminish the danger of igniting fire-damp and coal-dust. Nearly half the explosives in this dictionary are coal-mine explosives. The reason for this large number is that no finality has yet been reached as to the best and safest explosives to use in coal mines. When more experience has been gained it is probable that the number of these explosives on the market will be reduced. In England the Permitted List has recently been cut down considerably.

In Great Britain these coal-mine explosives have to be submitted to the Inspectors of Explosives, and are subjected to tests for safety and strength. If they pass they are placed on the list of “Permitted Explosives,” and the compositions are published in the Explosives in Coal Mines Orders. In these Orders the upper and lower limits of the percentage of each constituent are given, but in this dictionary intermediate percentages are given so that the sum for any explosive amounts to 100. In the Explosives in Coal Mines Orders the percentage of such a substance as wood, meal or starch, is given in the dried condition, but here it is given in the air-dry state on the assumption that it then contains about 10 per cent. of moisture.

In France and Belgium also the compositions of the coal-mine explosives are published, but in Germany, as a rule, only a list of the constituents is given, and sometimes an upper or lower limit for one or more of the principal constituents. Moreover, it is not stated explicitly whether the explosives are intended for use in coal mines or for general blasting purposes. In the United States of America, explosives intended for use in coal mines are examined by the Bureau of Mines, which, however, has no power to prevent the use of others because regulations on this matter are made by the individual states. If they pass they are placed on the list of “Permissible Explosives.” The compositions are not published, but the class of composition is stated.

Until the second half of the nineteenth century, gunpowder was practically the only explosive used on a considerable scale, and it was employed for all purposes. Consequently it does not fall into any of the classes mentioned, or rather it could be placed in several of them.

Another class of explosives that has not yet been mentioned is that of the primary igniters, of which fulminate of mercury may be taken as typical. The characteristic of these is that they can be exploded or ignited by a spark or moderate friction, and consequently they can be employed to fire other, less sensitive explosives. There are, however, practically no explosives of this class which possess special or proprietary names, and consequently they are not dealt with in this dictionary.

Naini Tal, India.
1920.