A RAPID SPECTROPHOTOMETRIC METHOD FOR THE ESTIMATION OF FLUORIDE

A rapid spectrophotometric method for the estimation of fluoride has been evolved making use of the bleaching action of the fluoride on yellow cerium (IV) solutions in sulphuric acid. The percentage transmission is recorded at 425 11m. By this method 0·1 mg-25 mg of fluoride present in 25 ml of the sample can be estimated. Small amounts of phosphate, chloride, nitrate and sulphate do not interfere. It is therefore possible to carry out a direct determination of fluoride without prior distillation in presence of the above ions. The interference by other ions like sulphide, sulphite, thiosulphate, carbonate and bicarbonate can be overcome by suitable treatments. This method can be employed for both micro and macro quantities of fluoride ions in solution and offers advantages over other methods currently in use.