Determination of Tungsten in Low-Grade Tungsten Ores

A field method for the determination of tungsten in soils

“…Only Z of 15 soil samples analyzed in our laboratory contained enough molybdenum in the final aliquot to impart an amber color to the isopropyl ether layer. Since the intensity of the color of the molybdenum thiocyanate complex ion is considerably less than that of the tungsten thiocyanate ion (Grimaldi and North, 1943;Sandell, 1950), and since tungsten is 4 to 5 times as abundant as molybdenum in the earth's crust (Goldschmidt, 1937), these results are not surprising. The adaptation of a method to field use requires the omission of unnecessary steps, particularly those using additional or larger quantities of reagents; therefore, except for the rare but easily discernible case of molyb-· denum interference, f:Oncentrated hydrochloric add is not added to tp.e sample solution (See p.…”

“…In order to test the usefulness of the method, several soils were analyzed by an accepted colorimetric laboratory procedure using the same reaction (Grimaldi and North, 1943), and by the proposed field method. The results are shown in table I.…”

Analysis of tungsten in low grade ores and geological samples

“…Among the reagents, thiocyanate and dithiol are widely used for the determination of small amounts of tungsten present in low grade ores and geological samples. Grimaldi and North (1943), were the first to suggest the determination of tungsten in rocks by dissolution in acids, reduction and formation of a soluble colour complex with thiocyanate. Sandell (1950) described in detail a method for the quantitative determination of tungsten in low grade ores.…”

Colorimetric Determination of Columbium and Tungsten in High-Temperature Alloys

“…Molybdenum is retained to a large extent with the columbium and tungsten in the initial separation (9) and would interfere in the determinations of both columbium (17) and tungsten (6,16), if provision were not made for its removal.…”