Abstract
After filtering AgSCN precipitate, which was formed by the addition of the known excess amount of Ag+ to the thiocyanate solution, (DDC)2Cu carbon tetrachloride solution was added to the filtrate. Color intensity of the organic phase decreased as the followingexchange reaction proceeded between the excess Ag+ and (DDC)2Cu.
Therefore, SCN- was determined through the estimation of Ag+, which was evaluated by the diminition of (DDC)2Cu color in CCl4.
The following procedure was recommended for the determination of 0-90ug of SCN-. The pH of the sample solution was adjusted to 4.7 with acetic acid-sodium acetate buffer solution, and 10 ml of 1.6x 10-4 mol//AgNO3 solution was added. After standingfor about 20 minutes, AgSCN precipitate was filtered through a No.5C paper filter which was treated previously with AgNO3 solution and was washed with water. The filtrate was poured into the separatory funnel (100 m/), the volume was made up to 60 ml and 10 ml of 0.8x10-4 mol// (DDC)2Cu carbon tetrachloride solution was added. Then, after shakingit for about 10 minutes and allowing it to stand for about 5 minutes, the absorbance of the organic phase was measured at 438 nm against the pure carbon tetrachloride solution.
The relationship between thiocyanate ion content, ranging from 0-90.6 jig, and its absorbance was linear and the apparent molarabsorptivitywas found to be 3.8 x 104. The standard deviation and the variation coefficient at the SCN- level of 45.3 respectively. Atg were 3.7 x 10-3 and 0.63%, respectively.
