Rapid analysis of chromite and chrome ore

Abstract

Rapid methods for the determination of the major and of some minor constituents of chromite and chrome ore permit the complete analysis of a dozen or more samples to be performed in about 5 days with a precision comparable to that of the more conventional methods. The sample is fused with sodium peroxide in a zirconium crucible. The major constituents are determined from aliquots of a single solution of sample prepared by acidifying a water extraction of the fusion product. Cr2O3 is determined volumetrically by ferrous ammonium sulfate dichromate titration; SiOj is determined spectrophotometrically using the reduced silicomolybdate color; total iron is determined by a modified differential spectrophotometric method using orthophenanthroline. An additional aliquot, electrolyzed in a mercury cathode apparatus, is used for the titration of MgO with Versene, and for the spectrophotometric determinations of A12O3 and TiOj with alizarin redS and Tiron, respectively. The minor constituents are determined on another aliquot from which CrO^C^ has been volatilized by fuming with HCIC^ and HC1; MnO, V2Os, and NiO are then determined spectrophotometrically using the permanganate, phosphotungstovanadate, and a-furildioxime colors, respectively. Separate portions of sample are used for the determination of CaO by Versene titration, H2O by the Penfield tube method, and FeO by one or more methods. The precision of the method was tested by comparing the results of the rapid procedures with those obtained by conventional procedures on standard materials.