Rapid analysis of silicate, carbonate, and phosphate rocks: Revised edition

The rapid methods previously used by the U.S. Geological Survey to determine the major constituents of rocks have been modified to introduce atomic absorption spectrometry (AAS) where applicable. Two procedures are available for determining 10 constituents: one, from a single solution prepared by a nitric-acid dissolution of a lithium metaborate-lithium tetraborate fusion, and the other, a two-solution method in which one portion of sample is dissolved in an HF-H₂SO₄,-HNO₃ mixture and another portion is fused with NaOH. In both techniques, SiO₂, Al₂O₃, Fe₂O₃, TiO₂, P₂O₅, and MnO are determined spectrophotometrically, and CaO, MgO, Na₂O, and K₂O are determined by AAS. Separate portions of samples are used for the following determinations: FeO by titration with K₂Cr₂O₇ after decomposition with HF and H₂SO₄; total H₂O by its weight when evolved on heating a mixture of sample plus flux; H₂O by loss of weight at 110° overnight; CO₂ by its volume upon evolution with acid; fluorine by a new indirect measurement of SiO₂ evolved with fluorine on heating; and. sulfur by a new procedure based on a turbidimetric measurement of BaSO₄, after an aqua regia attack. Several mechanical aids and automated devices are used for the analyses.