THE FORMATION OF EXPLOSIVE CHLORINE-NITROGEN COMPOUNDS DURING THE PROCESSES OF PRECIOUS METALS SEPARATION

The formation of the explosive compound NCl3 during the reaction of am monium compounds in hydrochloric acid with H2O2 or chlorine as an oxid ant was investigated. With the use of H2O2 in the acidity range from 3 to 6 M only traces of NCl3 were formed. On the other hand, when chlor ine was added to 0.01-2 M NH4Cl solutions, considerable quantities of NCl3 were formed by a rapid reaction. At acidities less than or equal to 3.5 M the reaction yield was 30-65% relative to the chlorine quanti ty used, depending upon the intensity of the interaction between the s olution and the chlorine phases. At acidities > 3.5 M and with rising reaction temperature (20-90 degrees C), NCl3 formation decreased. The NCl3/NH4+ mixtures were metastable. The decrease of NCl3 concentration in the reaction solution after the chlorine flow had been shut off wa s mainly due to evaporation of the NCl3 and only to a small extent due to conversion into the stable final products (N-2 or NO3-). In additi on, the formation of NCl3 in recycling of precious metals (PGM), espec ially during the precipitation of (NH4)(2)[IrCl6] and (NH4)(2)[PdCl6] and during the conversion of (NH4)(2)[PdCl6] into Pd(LI) compounds, wa s studied. During the precipitation of (NH4)(2)[PdCl6] considerable qu antities of NCl3 were formed. (C) 1997 Elsevier Science B.V.