STUDIES ON COLORIMETRIC DETERMINATION OF ANTIMONY (Ⅱ)CRYSTAL VIOLET MALACHITE GREEN METHOD Tsho

Rhodamine B and methyl violet have been considered as seusitive reagents for colorimetric determination of antimony.As crystal violet and malachit green also belong to the group of triphenylmethane dyes,containing=N⁺<_y^x group in their structure formulas,they might have therefore analogeous reaction with anti- mony,forming coloured complexes.This paper deals with the study and development of crystal violet and malachite green as reagents for colorimetric analysis of anti- mony,and the results of our investigations are summarized below: 1.Pentavalent antimony in acid solution reacts with both crystal violet and malachite green,forming coloured complexes,which are soluble in benzene. 2.The benzene solution of the coloured complex formed from crystal violet shows maximum absorption at 602 mμ,while that of coloured complex formed from malachite green shows maximum absorption at 634 mμ. 3.Both coloured complexes are unstable in aqueous solution but fairly stable in benzene. 4.Each mole of crystal violet and malachite green requires one mole of antimony to form coloured complex. 5.Concentration of antimony in the range of 0.2—1.0γ per ml can be determined by the use of crystal violet and malachite green colorimetrically with high accuracy. The proposed procedure may be summarized as follows: To 5 ml of sample(about 0.015 mg of Sb)in a measuring cylinder add 2.5 ml of 10N hydrochloric acid and 0.5 ml of 1N NaNO₂,shake and allow to stand for 2 minutes.Add 0.7 ml of urea solution and shake for 1 minute,then dilute with water to 20 ml.Transfer the solution into separating funnel,add 20 ml of benzene and 0.5 ml of 0.2% aqueous solution of reagent and shake immediatly for 5 minutes.Draw off the benzene solution and determine its trans- mittancy with photoelectric colorimeter.