Abstract
Investigations of sulfide – sodium systems of heavy non-ferrous metals and their associated minerals have played an important part in course of development of modern technologies of complex processing of compound raw materials and semiproducts. Crystallization of generated structures as complex compounds – thiosalts takes place during cooling of these alloys. The reaction 3(NH4)2S + Sb2S5 → 2(NH4)3SbS4 is considered to be an example of acid-base interaction of substances which do not contain oxygen and hydrogen. Theory of acids and bases developed by M.I. Usanovich says that acidity (basicity) is a substance property, which is not connected with belonging to a certain class of compounds and is a functional characteristic of comparison of partners in a given reaction. Developing these ideas R.G. Pearson has introduced a notion of "hard" and "soft" acids and bases (HSAB) and formulated the basic principle postulating that "hard" acids preferably interact with "hard" bases, and "soft" acids – with "soft" bases. There are a number of suggestions in geological literature for the qualitative estimation of acid-base interaction in compounds which form basis of rocks. One of them, namely, acid-base characteristic that is conditional potential of ionization is the most applicable to thiosalts.