Patent GB-507328-A (GB)
Title: Improvements in or relating to safety blasting and like operations with charges containing alkali metal nitrite-ammonium salt mixtures
IPC: C06D5/10
Filed: 1937-12-13
Abstract: 507,328. Blasting-charges. TAYLOR, J., and IMPERIAL CHEMICAL INDUSTRIES, Ltd. Dec. 13, 1937, No. 34480. [Class 9 (i)] A method of initiating the self sustained decomposition of a confined blasting charge com. prising a solid mixture of an alkali metal nitrite and one or more ammonium salts consists in introducing into contact with a. portion of said mixture a liquid acidic medium of at least one molar normal concentration having a hydrogen ion concentration less than that of a 0-5 normal hydrochloric acid solution and sufficient, to decompose the alkali metal nitrite, the said acidic medium being thus capable, as it is consumed, of maintaining in the presence of the charge a pH capable of decomposing the nitrite. The confined charge preferably consists of a atoichiometric mixture in granular form of sodium nitrite and ammonium chloride. The mixture may be stabilized with a small proportion of soda ash or magnesium oxide. The acidic medium employed is preferably capable of maintaining in the presence of the charge a pH not greater than 5-2 and not less than 10 and preferably not less than 3-5. Acids which may be used for the purpose of the invention include strong monobasic acids, such as hydrochloric and nitric; ,À weak monobasic acids, such as glycollic, acetic and butyric ; monobasic acids of moderate strength, such as monochloracetic and trichloracetic ; -, strong and weak dibasic acids, such as sulphuric, chromic, oxalic; tartaric, maleic and succinic; and tribasic acids, such as phosphoric and citric. Other liquid acidic mediums which may be employed: include: (1) acid salts, such as sodium or ammonium dihydrogen phosphates; (2) buffer solutions, such as mixtures of acetic acid with sodium acetate and ammonium phosphate with diammonium hydrogen phosphate; and (3) hydrolysable salts of acid reaction, such as zinc chloride and sulphate, aluminium sulphate, copper suphate, ferric chloride or sodium, potassium and ammonium dichromate. ' It is stated that magnesium chloride and sulphate, manganese sulphate, ferrous sulphate and lead nitrate are not effective. The acidic medium may be introduced into a charged high tensile steel tube container of the kind described in Specification 431,935 by screwing the reduced portion 2 of a steel body 1 into the end of the container remote from the venting cap which is of the type in which the axes of the venting apertures are inclined rearwardly as described in Specification 436,860. The charged cartridge is loaded into the borehole with the valve member 3 in the body 1 open and the liquid acidic medium is injected by means of a force pump through the recess 7, channels 6 8 and orifice 9, whereupon the valve is screwed home so as to seal the channel 8 and the whole device is then ready to effect the blast after the predetermined delay. According to a modification. Fig. 2 (not shown), the outer end of the body 1 is internally threaded to receive a screw capsule holding a small quantity of the acidic medium under pressure of dissolved gas, the capsule being seated by a diaphragm adapted to be ruptured on screwing the capsule home. Specifications 430,750. 431,936, 431,950, 436,144,461,647, and 484,098 also are referred to.