CHAPTER 16 - Chlorine, Bromine and Iodine

Abstract

Based upon the precipitation of silver chloride, gravimetric methods have long been used for the determination of chlorine. It is, however, difficult to collect and weigh the small quantity of silver chloride obtained from rocks containing 0.05 per cent or less of chlorine. The introduction of ion-selective electrodes has given rise to new methods of analysis and adaptations of older ones for a number of elements, and chlorine is one of these. The simple and rapid determination of chlorine and fluorine in granitic rocks, using ion-selective electrodes, are known. This chapter discusses the determination of water-soluble chlorine in rock materials. The presence of water-soluble chlorine in more than trace amounts is usually indicative of halite, kalsilite, carnalite, or other evaporite mineral in the rock material. Many of the chlorine minerals are completely decomposed by heating with dilute nitric acid. The loss of chlorine may occur if the acid strength is too high or if the heating is prolonged.