EXTRACTION OF GOLD(III) FROM HYDROCHLORIC-ACID SOLUTIONS BY N-(THIOCARBAMOYL)BENZAMIDINES

The solvent extraction of Au(III) from hydrochloric acid solutions by N-(thiocarbamoyl)benzamidines in chloroform has been studied. The distribution of gold has been determined at constant ionic strength of 0.1 ((K+, H+)NO3-) as a function of pH and the analytical concentrations of extractant and chloride. The equilibrium data have been treated by means of the programs EXMAR and LETAGROP-DISTR. The data analysis indicates the formation of the species AuCl4HL and AuCl3. In case of 4,4'-biphenyl-bis-{N-[N''-(diethyl)aminothiocarbonyl]-benzamidine} 2:1 complexes (Au:L) are formed. Nitrate and perchlorate ions are not extracted. The studied N-(thiocarbamoyl)benzamidines exhibit high selectivities for Au(III) and Ag(I) towards Co(II), Zn(II) and Cu(II).