ABSTRACT
A simple and selective EDTA method using a masking and demasking technique is proposed for the determination of thallium(III). The thallium is complexed with excess of EDTA, the surplus being back-titrated (pH 5-6, hexamine buffer) with zinc sulphate solution (Xylenol Orange as indicator). 4-Amino-5-mercapto-3-propyl-1,2,4-triazole is then added and the mixture heated on a water-bath for 5-10 min to displace EDTA from its thallium complex. The EDTA liberated is titrated with zinc sulphate solution. Reproducible and accurate results are obtained in the range 5-75 mg of thallium with both the relative error and coefficient of variation not exceeding 0.4%.
ABSTRACT
A simple, rapid, and selective complexometric method is proposed for the determination of mercury(II). Mercury(II) is first complexed with excess of EDTA and the surplus EDTA is back-titrated (pH 5-6) with zinc sulphate solution, with Xylenol Orange as indicator. 4-Amino-5-mercapto-3-propyl-1,2,4-triazole is then added to displace EDTA from the Hg-EDTA complex and the released EDTA is titrated with zinc sulphate solution. Reproducible and accurate results are obtained in the range 1-40 mg of mercury, with a relative error of approximately 0.4%.
ABSTRACT
A simple, convenient and accurate gravimetric method for the determination of silver is presented. 4-Amino-3-methyl-5-mercapto-1,2,4-triazole precipitates silver quantitatively from ammoniacal tartrate medium. The complex is weighed as AgC(3)H(5)N(4)S after drying at 120-30 degrees . Separation of silver from a large number of cations is described. Application of the method for quantitative analysis of alloys and complexes of silver is reported. The average relative error for the range 20-70 mg of silver is +/- 0.25% and the relative standard deviation at the 40-mg level is 0.2%.
