Sodium Peroxide Fusion

Colson described an alkali fusion for the determination of down to 500 ppm of sulfur in polymers [13, 14], in which the sulfate in the digest is determined by titration with N/lOO sodium hydroxide or by photometric titration with N/lOO barium perchlorate. 

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Insoluble iridium dioxide from the sodium peroxide fusion is dissolved in aqua regia, oxidized with nitric acid, and precipitated with ammonium chloride as impure ammonium hexachloroiridate(IV), To purify this salt, it is necessary to redissolve the compound and precipitate out the... 

Iron ware. Iron crucibles may be substituted for those of nickel in sodium peroxide fusions. They are not so durable, but are much cheaper. 

Micro amounts of sulfur in polymer are usually determined by oxygen flask combustion, sodium peroxide fusion in a metal bomb followed by titration [30], pyroluminescence [36] or ICP-AES. An oxygen flask combustion photometric titration procedure capable of determining total sulfur in polymers in amounts down to 50 ppm was reported. The repeatability of the sulfur determination in polyolefins in the oxygen flask is 40% at 50 ppm level, improving to 2% at the 1 % level [21]. Crompton [31] has also combined Schoniger flask combustion with a colorimetric procedure for the determination of phosphorous in polymers in various concentration ranges (0.01 to 2%, 2 to 13%). 

Applications Basic methods for the determination of halogens in polymers are fusion with sodium carbonate (followed by determination of the sodium halide), oxygen flask combustion and XRF. Crompton [21] has reported fusion with sodium bicarbonate for the determination of traces of chlorine in PE (down to 5 ppm), fusion with sodium bisulfate for the analysis of titanium, iron and aluminium in low-pressure polyolefins (at 1 ppm level), and fusion with sodium peroxide for the complexometric determination using EDTA of traces of bromine in PS (down to 100ppm). Determination of halogens in plastics by ICP-MS can be achieved using a carbonate fusion procedure, but this will result in poor recoveries for a number of elements [88]. A sodium peroxide fusion-titration procedure is capable of determining total sulfur in polymers in amounts down to 500 ppm with an accuracy of 5% [89]. 

Uranium in mineral ores An approximately 10 per cent solution of the sample containing 25-50 per cent free nitric acid (by volume) is prepared by a suitable method (e.g. a potassium hydroxide or sodium peroxide fusion, followed by treatment with nitric acid). A portion of the sample (0 05 ml) is spotted upon filter paper in the usual manner and allowed to dry in the air. The solvent consists of 2-methyltetrahydroxyfuran (tetrahydrosylvan) saturated with water and to which sufficient concentrated nitric acid has been added to give a 2-5-10 per cent concentration of nitric acid. The paper strip is removed when the solvent front has moved 5-7 cm beyond the test patch, and dried in a current of warm air. The uranium moves in a narrow band near the solvent front. The paper is sprayed with 1 per cent potassium hexacyanoferrate(II) solution. A brown stain appears in the presence of uranium. The quantity of uranium may be estimated by comparison with standard stains prepared with known amounts (0-1-200 pg) of uranium. 

Enzweiler, J., Potts, P.J. The separation of platinum, palladium and gold from silicate rocks by the anion exchange separation of chloro complexes after a sodium peroxide fusion an investigation of low recoveries. Talanta 42, 1411-1418 (1995)... 

Lead can be recovered from mineral samples by sodium peroxide fusion (R3)(R8) followed by dissolution of the melt In nitric acid. For many roclc and soil samples, leaching with hot dilute (L 3) nitric acid (H13) or with hot concentrated sulfuric acid followed by nitric acid (P2) or with a sulfuric acid-hydrofluoric acid mixture (I2) has been found to be adequate. 

Method 2.6 Determination of Macro-amounts of Sulfur in Polymers. Sodium Peroxide Fusion - Titration Procedure... 

This sodium peroxide fusion - titration procedure [40] is capable of determining total sulfur in polymers in amounts down to 500 ppm. 

When the sodium peroxide fusion is carried out as described, only a small amount of insoluble matter should be found in the aqueous extract of the fusion product, but this material can interfere with the detection of the end-point of the titration. For the best results the extract should be set aside overnight, so that a clear portion can be withdrawn for titration. 

Sodium peroxide fusion in a metal bomb has also been used to decompose polymers prior to the determination of down to 50 ppm sulphur. In the procedure described in Method 81 sodium is removed from the fusion product by means of a cation exchange resin and the sulphate is determined by titration with standardised 0.005M barium perchlorate. Chlorine, fluorine and nitrogen in amounts up to 2 mg. in the sample are without serious effect on the determination of sulphur. The effect of larger amounts of fluorine can be suppressed by the addition of boric acid. 

METHOD 81 - DETERMINATION OF MACRO-AMOUNTS OF SULPHUR IN POLYMERS. SODIUM PEROXIDE FUSION - TITRATION PROCEDURE. ... 

Enzweiler, J., Potts, P. J., and Jarvis, K. E. (1995). Determination of platinum, palladium, ruthenium and iridium in geological samples by isotope dilution inductively coupled plasma mass spectrometry using a sodium peroxide fusion and tellurium coprecipitation. Analyst (London) 120(5), 1391. 

If the sample is refractory, use the sugar carbon-sodium peroxide fusion method described by Muehlberg. After dissolution of the sample In this manner, transfer the acidified solution to an appropriate volumetric flask and dilute so that the final solution Is In nitric acid. 

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