Premixture for explosive mfr. - is prepd. from ammonium nitrate and formaldehyde and contains ammonium nitrate, methyl nitrate and alkali metal formate
Pre-mixt. for the mfr. of explosives is prepd. in liq. phase by (a) mixing NH4NO3 and HCHO; (b) heating gradually to set up an exothermic reaction and keeping 1-2 hrs. at =95 degrees C; (c) vacuum distn. to reduce water content to 8-10 wt.% and (d) removing the HCOOH formed, to leave 1.wt.% HCOOH, by adding sufficient MeOH or EtOH to form Me-. or Et formate and vacuum distn. The residual HCOOH is then neutralised with alkali to pH 6.5, to form a liq. mixt. consisting of NH4NO3, mono- or dimethyl nitrate and a small quantity of alkali formate. The pre-mixt. can be worked to (1) rock-blasting explosives for underground or tunnel construction, and (2) safety mining explosives for coal mines subject to fire-damp. The explosives are water-proof and can be ignited in water-contg. drilling holes up to 24 hrs. after charging.