T.N.T. poisoning and the fate of T.N.T. in the animal body.

Date:
1921
Catalogue details

Licence: Public Domain Mark

Credit: T.N.T. poisoning and the fate of T.N.T. in the animal body. Source: Wellcome Collection.

    12/94 (page 10)
    explosive in the ratio of something like 10 to 1. But burning petrol is a comparatively slow process and hence the effects of the burning of petrol and the detonation of an explosive can hardly be compared.. The power of an explosive is commonly decided by making a hole in a lead block, plugging the hole with a steel bung, and then firing the explosive by means of a fuse. Under these conditions the lead block will swell out and water poured into the cavity will give a rough indication of the amount of gas liberated. The violence of an explosive is measured by the rate at which the explosion spreads in a column of material, technically spoken of as the velocity of detona¬ tion. The power of T.N.T. is about 95 per cent, of that of picric acid. The velocity of its detonation is about 7,000 metres a second, that is to say a wave of detonation will run through a column of T.N.T. at 7,000 metres a second as compared with 7,800 for picric acid. T.N.T. is relatively a scarce commodity. Ammonium nitrate can be manufactured in very large quantities, and therefore to- economize T.N.T. and to make the fullest possible use of ammonium nitrate, dilution of T.N.T. by ammonium nitrate was a matter o£ early trial and experiment. The earliest mixture was roughly half of T.N.T. and half of ammonium nitrate. This was sufficiently fluid when hot to be poured under favourable conditions, but it was found to be a little too thick for factory operations, so that gradually the mixture became one of 40 per cent, ammonium nitrate and 60 per cent, of T.N.T. or 40/60 AMATOL, but in the latter months of the war another mixture was introduced consisting of four parts of ammonium nitrate to one part of T.N.T., 80/20 amatol. As regards power, amatol is more efficient than either picric acid or T.N.T. alone; taking picric acid as a standard and calling it 100, the power of 40/60 amatol is 116 and 80/20 amatol is 127, and as regards crater effects an explosive containing a large proportion of ammonium nitrate proved better than an explosive consisting of pure T.N.T. A great merit, however, of a high explosive is its insensitive¬ ness. Amatol can be filled into a shell in a manner that would be dangerous with black powder: the firing of a charge of cordite behind a shell is sufficient to give its contents a severe shock, and . if the shell were filled with a sensitive explosive there would be a very real risk that the shock of the charge would cause immediate detonation of the shell contents. In firing, too, against concrete dug-outs or armoured shelters it is important that the shell shall not detonate upon impact but shall at first attain some measure of penetration. Experience has shown that shell cases have been knocked in by the detonation of other shells and yet the amatol contents inside have not been detonated. The importance of this factor to ammunition dumps cannot of course be over-rated. The manner in which insensitive explosives are detonated is by means of a series of relays. The detonation is started by mercury fulminate which is very sensitive and fairly violent. This sets off an intermittent explosive called tetryl. The third relay or stage is crystals of T.N.T. Between the crystals of T.N.T. and the amatol in the shell is some cast T.N.T.