LYDDITE: THE NEW EXPLOSIVE.

Otago Witness, Volume 16, Issue 2351, 16 March 1899, Page 49

LYDDITE: THE NEW EXPLOSIVE.

(Chambers's Journal.)

Probably one of the most interesting features of the Omdurman campaign, from it military standpoint, was the great success achieved by the lyddite shells, which, used for the first time in actual warfare by the British army, proved that lyddite is the best -explosive as yet discovered for use in shells. It is the object of the present article to give a short description of this substance, which is destined to j)lay an important part in the wars of the future. Lyddite is only a variety of picric acid, which has been melted and allowed to solidify, thereby becoming denser. Melinite, recently introduced into the French army, is also another form of picric acid ; indeed, most of the so-called " new " explosives consist of this substance in one or other of its forms, disguised by different names. The history of picric acid as an explosive is remarkable, and furnishes a striking example of how great discoveries may frequently result from accident. Picric acid was discovered in 1771, and for more than a century was used as a dye for wool, silk, and leather, without its explosive powers being .suspected. Some ten 3 r ears ago, however, a lire occurred at a chemical work in Manchester, and spread to a shed containing a quantity of this acid. Being melted by the heat, the acid flowed until it came into contact with a quantity of litharge stored in the same building. A terrible explosion followed, and subsequent investigation revealed the fact that under certain conditions picric acid behaved as a powerful explosive. Further experiments have made clear the necessary conditions ; and at the present time picric acid bids fair to outrival all other explosives for the purpose of filling shells. Before proceeding to describe the manner in which this body is caused to, liberate its explosive power, it will be advisable to give a brief account of its manufacture and common properties, in order that the sequence muy be made clear. Pure phenol, or carbolic acid (the common disinfectant obtained from coal-tar), is placed in a vessel with an equal amount of strong oil of vitriol (sulphuric acid), and the temperature raised to the boiling point of water. Strong nitric acid, (aauafortis) is then, alkffifid. io

Soav into the mixture, after which the AA'hole is cooled, leaving a solid mass of yellow crystals in the vessel. These crystals are filtered and drained,' and afterAA'ards Avashed Avitli cold Avater — Avhen the residtie is pure picric acid. The crystals so obtained haA-e an intensely bitter taste, and for this reason have been largely employed on the Continent for the adulteration of beer. If handled, picric acid stains the fingers a golden yelloAA'. If heated gently, it melts quite tranquilly, and may be poured from one vessel to another. If strongly healed, it chars with a slight fizzle ; if hammered on an anvil no detonation occurs, as in the case of most oth?r cxplosiA^es. A cursory examination, such as the foregoing, gives no indication of its latent powers, and it is therefore a matter of little Avonder that they should have remained undiscovered for more than a century. . . ". The shock necessary to explode picric acid in all its forms is furnished by a class of bodies knoAvn as "detonators." These are sensitiA-e bodies which explode with great violence ; and if placed in contacc Avith'a large mass of picric acid, the shock to which their explosion gives rise causes the Avhole charge to detonate, an extremely small quantity of the detonator sufficing to set into action an indefinitely large quantity of the acid.