Published online by Cambridge University Press: 27 March 2009
1. Comparisons are made of the results obtained in the analysis of clays, especially of clay fractions separated from soils, by the standard sodium carbonate fusion method and by attack by means of mixed acids. Provided certain precautions are taken, in the latter case, the percentages of silica obtained are shown to be comparable with those given by the fusion method.
2. A possible disadvantage of the acid method is that the attack of the clay is not invariably successful, but treatment of the silica with hydrofluoric acid provides a convenient and reliable means of detecting those cases in which failure occurs. Such clays must be decomposed by fusion with sodium carbonate.