Toxicity and spectrophotometric determination of sulphur dioxide in air using a new absorbing agent
An aqueous solution of succinyldihydroxamic acid (SDHA) is proposed as an efficient absorbing agent for ambient sulphur dioxide. The agent (SDHA) is easy to prepare, has an absorption efficiency of approximately 100% and its resulting sulphite solution is stable for more than 30 d. The absorbed sulphur dioxide has been subsequently determined spectrophotometrically by condition optimised p-aminoazobenzene-formaldehyde in hydrochloric acid. The pink dye formed has an absorption maximum at 505 nm. The proposed method is superior to the widely used tetrachloromercurate method in terms of manipulation, speedy results and use of stable, pure and non-toxic reagents. The interference from nitrogen dioxide has been removed by the use of sodium azide-malonyl dihydrazide. The procedure has been applied to the determination of sulphur dioxide both in the vicinity of a superphosphate fertiliser plant and in work-room air.