[en] It is known that stability of composite compounds in solutions is defined by great amount of parameters characterising metal and ligand cations. As such situation makes the development of theoretical quantitative approach difficult, now one have to be satisfied with different types of qualitative classifying schemes which are based on generalization of experimental facts. There are a lot of such schemes and one of them is the Luis's principle of hard acids and bases. According to Pirson's principle the soft acid such as ions of noble metals react with soft bases because soft acids have affinity to sulphur and nitrogen. Therefore we have synthesised and studied complex forming properties of phosphorous acids and their derivatives. The obtained results on the extraction of Au, Ag, Pt, Pd and Os have shown that these compounds are chelatoforming complex forming ones. Research on the noble metals extraction from acid medium by neutron-activation analysis method shows that: Some of these compounds can be used as effective group reagent in regard to gold, silver and palladium. (0.1-1.0 M, 97-99 %); Compounds with acetylene bonds are more suitable for extracting gold and silver ions from HCl (88-90 %) and H₂SO₄ mediums (97- 83 %) respectively. In the low concentrated acids gold and silver ions can be extracted better by S - benzene-sulphonate from chloride acid medium in organic phase (Au-87 %, Ag-93 %) than from sulphuric acid (Au-24 %, Ag-69 %); Extension of O-alcil radicals in S-β ephoxipropiltio-phosphate molecules leads to little change of silver's extraction efficiency at 0.1-1.0 M H₂SO₄, while increase of HCl concentration leads to sharp reduction of this efficiency (from 86 till 5%)

[en] At present the methods of determination and extraction of platinum metals, the extraction methods are widely used in analytical chemistry. With the purpose of revealing effective extractors for noble metals' ions Au, Ag, Os, Pt, Pd, Ir and to do comparative analysis with corresponding dialkyl-tio-phosphates the synthesis of a number S-alkyl-ethyl-xanthates was carried out. All the obtained compounds were characterized by physical and chemical constants, their structures were determined by the data of spectral analysis. The process of silver ion extraction from the chlorine, sulfuric and nitric acids were investigated by neutron-activation analysis using radioactive Ag-110 isotope obtained by irradiation of the metal in the WWR-SM reactor. The dependence of the efficiency of silver extraction on the reagent structure and on an acidity and nature of the solution was determined. The optimum conditions of the metal extraction from solutions of mineral acids were found. The conditions for a selective separation of silver from gold, osmium, platinum, palladium and iridium ions with the help of the obtained compound were determined