Determination of iron(II) in silicates by gravimetric titration

Abstract

A4 rapid method, suitable for batch working, is described for determining iron(I1) in silicates. Hot 1 + 1 hydrofluoricsulphuric acid decomposes the subsample in a polypropylene bottle previously filled with carbon dioxide.After dilution with a boricphosphoricsulphuric acid mixture, iron(I1) is titrated gravimetrically with potassium dichromate solution, in the bottle used for sample decomposition. A sample-preparation procedure that minimises oxidation of iron(I1) is described. Results obtained for iron(I1) in various international reference rocks by the proposed method agree well with recommended values.Keywovds : Ivon(II) determination ; silicates ; gyavimetvic titvation French and Adamsl have published a procedure for determining iron(I1) oxide in rocks that involves decomposition of the sample by treatment with a hot 1 + 1 mixture of concentrated hydrofluoric and sulphuric acids. A modification of this procedure is used by the CSIRO Division of Alineralogy, North Ryde, New South Wales.2 The latter procedure differs from the former procedure mainly in that the sub-sample is decomposed in a narrow-mouthed 125-ml polypropylene bottle previously filled with carbon dioxide, rather than in a 60-ml wide-mouthed polypropylene bottle, and the redox titration is performed with potassium dicliromate solution and sodium diplienylamine sulplionate, rather than with cerium( IV) sulpliate solution and N-phenylanthranilic acid as titrant and indicator, respectively.Tlie procedure described in this paper is simpler than the two procedures referred to above for the following reasons. Experimental Sample-preparation EquipmentThis consists of the following items installed in a sample-preparation room with dust extraction facilities for operator safety.Hydrniilic lnboirntory cruslzerbreakel. with tuizgsten carbide working faces. Obtainable from Rocklabs, P.O. Box 28-362, Auckland 5, h'ew Zealand.J n ~l c r i r s l w uiith nzaj?gajiese haideized steel plates. As an alternative to the hydraulic laboratory crusherbreaker.Sicbtccliizik tungsten carbidecobalt riizg griizder, 300-ml. M'eighing about 11.6 kg and obtainable from Siebtechnik, lIiihlheim, Federal Republic of Germany.TT-cdrrg Znborntoyv Liibmtiizg cup mill, Type ML\T 954/2. Obtainable from KHD Industrieanlagen SiccZ ndnptoi/ base. This allows the Siebtechnik grinder to be used with the Il'edag vibrating cup mill. Humbold t IVedag, Federal Republic of Germany.Il'eighing about 2.7 kg. 48 RICE : DETERMINATION OF IRON(II) IN

Determination of ferrous iron in rock and mineral samples by three volumetric methods

“…In the other method, the Fe(II) ions are oxidized upon release by an oxidizing agent present in excess during the decomposition of the sample and the excess then determined (Johnson and Maxwell 1981). Ferrous iron in the solution is measured by volumetric, spectrophotometric, polarographic or ion chromatographic methods (Rice 1982, Bruce etal. 1987, Kiss 1987, Moore 1979, Kanai 1990).…”

Petrochemistry of intrusive rocks in Tha Takiap district, Chachoengsao province

“…Loss on ignition was determined by heating 1 g of fine powder sample at 1,1 00 °C for 1 hour and reweighting. Moreover, ferrous oxide (Iron (II) oxide: FeO) was determined by Gravimetric Titrations Technique described by Rice (1982).…”