Two rapid methods for the decomposition and chemical analysis of clays were adapted for use with 20-40mg size samples, typical amounts of ultrafine products (< 0.5 micrometer diameter) obtained from modern separation methods for clay minrals. The results of these methods were compared with those of 'classical' rock analyses. The two methods consisted of mixed lithium metaborate fusion and heated decomposition with HF in a closed vessel. The latter technique was modified to include subsequent evaporation with concentrated H2SO4 and re-solution in HCl, which reduced the interference of the fluoride ion in the determination of Al, Fe, Ca, Mg, Na, and K.-from Authors
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Comparison of rapid methods for chemical analysis of milligram samples of ultrafine clays.