Eschka method, chlorine

The concentrations of alkali metals and chlorine were determined directly for the fuel samples using a inductively coupled plasma-atomic emission spectrometry apparatus in order to analyse sodium and potassium contents. Chlorine content was determined by Eschka method according to ASTM D2361-66. The concentrations are given on dry basis (table 1). 

The results of experiments with ten coals from different localities are shown in Table II. For a comparative study, the total chlorine content of each coal sample was also determined by the Eschka method. 

In both methods it is possible to lose some of the chlorine during combustion unless necessary precautions are taken. Thoroughly mixing the coal sample with Eschka mixture and covering this carefully with additional Eschka mixture minimizes the loss of chlorine. In bomb combustion methods, the ammonium and sodium carbonate solutions in the bomb are used to absorb the chlorine as it is released in the combustion. The 10- and 15-minute waiting periods and the slow release of pressure on the bomb help to prevent the loss of chlorine as well. 

A modification of the oxygen bomb combustion method (ASTM D-2361) for the determination of chlorine consisted of acidifying a solution of the adsorbed combustion products and titrating the chlorine potentiometrically. A potentio-metric titration was also tried for the determination of chlorine by the oxygen flask method. Combustion products, including chlorine, were absorbed in sodium hydroxide (NaOH), and the chloride was measured using silver-silver chloride electrodes. Although there was no statistical difference in results obtained from potentiometric titration and the Eschka procedure, the latter was more precise. 

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