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Overview of the determination of tungsten

Release date:2018-04-27  source:中南选矿网  Browse times:549
       The measurement of tungsten can be carried out by a gravimetric method, a volumetric method, a colorimetric method, a polarographic method, an atomic absorption spectrometry or the like. Among them, colorimetry is most commonly used. The gravimetric method of tungsten includes a Cinchonine method, an ammonium tungstate method, an 8-hydroxyquinoline method, a mercury mercuric acid method, a tungstate tungstate method, a benzidine method, a tannin-antipyrine method, and the like. The latter four methods are rarely applied due to the large number of interfering elements and stricter precipitation conditions. The ammonium tungstate gravimetric method, according to the use of the years, proves that the method has high work efficiency, low cost and easy operation. When the analytical quality requirements are high, the final burning of tungsten trioxide should be corrected for bismuth, antimony and molybdenum. The effect of the corrected tungsten is good reproducibility and high accuracy. The Cinchon weight method is a classic analytical method with good accuracy and reproducibility, and does not require a large platinum dish. The main disadvantage of the method is that the time required is relatively long, and impurities such as silicon, germanium, antimony, molybdenum and tin are also contained in the precipitate, which has been used less frequently. But for some laboratories that lack platinum, there is still value in use. The 8-hydroxyquinoline gravimetric method is relatively simple to operate, and ruthenium, osmium and molybdenum can be completely separated from tungsten. The addition of EDTA eliminates the effects of interfering elements and is suitable for the determination of tungsten in high-content tungsten ore and tungsten concentrates. The volumetric method of tungsten is determined by a precipitation titration method, an oxidation-reduction method, an EDTA indirect measurement method, and an alkali amount method. These methods are more difficult to obtain satisfactory results due to the large number of interfering elements in tungsten ore, and are often difficult to obtain satisfactory results, so they are rarely used in actual production. Recently, the Anshan Iron and Steel Chemical Laboratory proposed a volumetric method for the determination of tungsten in ferro-tungsten by complexometric titration. The sample was dissolved by acid. Most of the interfering elements were removed by precipitation with sodium hydroxide. The obtained sodium tungstate test solution was precipitated by adding lead acetate to precipitate lead tungstate. No excess of lead was titrated with EDTA at pH 5.5-5.8 without filtration. The elements that enter the alkaline solution together with tungsten are aluminum and a small amount of iron, manganese, copper, tin, etc., which are masked with acetylacetone, o-morpholine and lactic acid, respectively. Because the filtration process is omitted, the operation is relatively simple and fast. The colorimetric method of tungsten includes a dithiophenol method, a hydroquinone method, a rhodamine B method, and a thiocyanate method. The first three methods have many interfering elements, and the operation is complicated and has little practical significance. The thiocyanate method is easy to operate, has few interfering elements, and has good accuracy and reproducibility. It is a widely used method.

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