The formation of the explosive compound NCl 3 during the reaction of ammonium compounds in hydrochloric acid with H 2O 2 or chlorine as an oxidant was investigated. With the use of H 2O 2 in the acidity range from 3 to 6 M only traces of NCl 3 were formed. On the other hand, when chlorine was added to 0.01–2 M NH 4Cl solutions, considerable quantities of NCl 3 were formed by a rapid reaction. At acidities ≤ 3.5 M the reaction yield was 30–65% relative to the chlorine quantity used, depending upon the intensity of the interaction between the solution and the chlorine phases. At acidities > 3.5 M and with rising reaction temperature (20–90°C), NCl 3 formation decreased. The NCl 3 NH + 4 mixtures were metastable. The decrease of NCl 3 concentration in the reaction solution after the chlorine flow had been shut off was mainly due to evaporation of the NCl 3 and only to a small extent due to conversion into the stable final products (N 2 or NO − 3). In addition, the formation of NCl 3 in recycling of precious metals (PGM), especially during the precipitation of (NH 4) 2[IrCl 6] and (NH 4) 2[PdCl 6] and during the conversion of (NH 4) 2[PdCl 6] into Pd(II) compounds, was studied. During the precipitation of (NH 4) 2[PdCl 6] considerable quantities of NCl 3 were formed.