A NEW SPECTROPHOTOMETRIC METHOD TO DETERMINE HG(II) WITH [ZN(1-3-DITHIOLE-2-THIONE-4,5-DITHIOLATE)(2)](2-) ANIONIC COMPLEX

A new method is presented for a spectrophotometric determination of tr ace mercury in aqueous solution by using the anionic complex [Zn(1-3-d ithiole-2-thione-4,5-dithiolate)(2)](2-) ([Zn(DMIT)(2)](2-)). In alkal ine solutions (pH = 12.0 divided by 12.5) in the presence of Hg(II) at room temperature a metal exchange reaction occurs rapidly with the fo rmation of [Hg(DMIT)(2)](2-). Heating the reaction mixture to 60 degre es C, the excess zinc complex partially decomposes. Using a solution o f [Zn(DMIT)(2)](2-) treated in the same way as a check, it is possible to show the absorption band of the mercury complex. [Hg(DMIT)(2)](2-) has an intense absorption band in the visible with a maximum at 500 n m and a molar absorptivity of 1.45.10(4) dm(3) mol(-1) cm(-1) in solut ion it follows the Lambert-Beer law in the 0.96.10(-6) - 4.80.10(-6) M range. The procedure is compared with the dithizone method.