The danger of chemical reactions in the interaction of incompatible substances manifests itself in an increase in temperature and pressure, ignition, and finally, these reactions can be accompanied by an explosion.
By the method of a constant volume bomb, the processes of interaction of mutually reacting substances are studied, as which mixtures of combustible substances (sodium, magnesium, sulfur, and an organic liquid — glycerin) with a changing mass of the oxidizer (ammonium nitrate, ammonium perchlorate, potassium permanganate, potassium bichromate) and in a mixture of these substances of stoichiometric composition are studied: a combustible component and an oxidizer.
Analysis of the dependences of the coefficient of participation of a substance in an explosion on the coefficient of excess of an oxidizer of various interacting substances indicates that these dependences can be of two types: with an extremum and in the form of a direct dependence. Continuous increase in the coefficient of participation in the explosion with an increase in the coefficient of excess of the oxidizer indicates the ability to decompose and participate in the explosion of the oxidizer itself. This type of dependence established experimentally for the powders of combustible sulfur and magnesium with oxidizing agents-ammonium nitrate and ammonium perchlorate, shows that both combustible and decomposition products of a flammable oxidizing substance participate in the explosion. Other mixtures (magnesium, glycerin mixed with potassium permanganate, potassium bichromate) have an extremum, and the oxidizer does not participate in the pressure increase when the oxidizer content in the mixture increases.
Calculation confirms the possibility of determining chemical compatibility (incompatibility) of substances using the standard Gibbs energy. Based on the example of the experimentally established incompatibility of mixtures of magnesium and sulfur with ammonium nitrate, the calculation also shows that these substances are incompatible with each other.
In the absence of experimental data on the compatibility of substances, the input data for calculating the Gibbs energy, the information on the compatibility (incompatibility) of substances can be borrowed from tables 15–17 of GOST 12.1.004. Hazardous and especially hazardous substances indicated under numbers 3 and 4 in these tables are incompatible.
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