MODERN EXPLOSIVES.

Hawera Star, Volume XLVIII, 13 September 1924, Page 6

MODERN EXPLOSIVES.

TWO CLASSIFICATIONS

. u interesting review of the application of modern high explosives was given in a lecture delivered by Captain W. 11. Key-Jones at a recent meeting of the Auckland Officers’ Club. 11 Explosives may be. classified into tivo groups, high explosives and low explosives,” said the lecturer. Low explosives are dispersive in their effect, and produce their effect by rapid combustion and production of a large volume of gas. They are used as the propellents of projectiles, s nch as rifle bullets and shells, also for demolition work where a dispersal effect is required. The most,' commonly known low explosives are black powder, cor-dite,-balistite, E.C., Schultz, and amberite.

High explosives produce their effect by detonation, that is; by instantaneous disintegration into gases. Their effect is shattering, owing to the fact that if applied to solids they instantaneously produce terrific pressure and shatter the solids to pieces. If a properly tamped charge of black powder was applied to a steel girder lying on the ground and fired, it ■would move the steel girder as a whole, whereas if a high explosive, say gun-cotton, were applied in the same way, its effect would be to cut the steel girder in two, hardly moving the girder at all, and, at the break;* a portion of the steel girder would be shattered into small pieces. The most commonly known high explosives are nitro-glycerine, guncotton, dynamite, blasting gelatine, gelatine, dynamite, nitro-benzine, trini-tro-toluol, known as T.N.T., aminol, and the various fulminates.

These two broad classes of explosives may be again divided each into two sub-classes—low explosives that are low explosives under all 'conditions, and those, such as cordite and the other nitro low explosives, that will detonate if they get a sufficient shock. Then there are the high explosives that- require a fair amount of shock to detonate, and those that are very sensitive. Sensitive high explosives are nitro-glycerine and the fulminates. The lecturer demonstrated how sensitive a high explosive can be by causing a small portion of nitro-iodide to detonate with a sharp report by merely touching it with the tip of a. feather. He then described the various explosives mentioned above, with reference to their military value, aud outlined the .methods of firing by electricity.