Abstract
Thiosemicarbazide forms a soluble blue complex with copper (II) in acidic aqueous solution. The complex has two absorption peaks at 356 mμand 700 mμ, respectively. The peak at 356 mμ is high enough so that an almost coloress solution containing 3 ppm of copper (II) and thiosemicarbazide has an absorbance of 0.26 at this wavelength.
Copper (II) (0.52.0 ppm) is determined by the measurement of 356 mμ absorbance after an addition of 0.05 g. of thiosemicarbazide with 1.0 ml of 35% hydrochloric acid to 50ml of solution. The calibration line is given by a regression equation y=0.0874x+0.0018, where y is the absorbance at 356 mμ for the copper (II) concentration (ppm) x. The standard deviation is 0.02 ppm at the level of 1 ppm.
There hardly was any substance except iron (III) which would give much interference with the determination of copper (II).
Measurements by the continuous variation method and the molar ratio method showed that the composition of the complex was 1 (Cu) : 2 (thiosemicarbazide) in molar ratio.
Solution, below pH 4, containing the complex did not show any change in its absorbance after having been kept at 15 to 40°C for 24 hours.
The application of this method to industrial wastes, preliminarily treated, was successful. The rapidity and simplicity are the advantages of this method.
