Mesityl oxide (4-methyl-3-pentene-2-one) can be used for the solvent extraction of beryllium. It quantitatively extracts beryllium from 0.5M hydrochloric acid containing 5M potassium thiocyanate. The metal can be stripped from the organic phase with water and determined photometrically at 530 nm, as its complex with aluminon.The reagents useful for the quantitative extraction of beryllium are very limited in number. Acetylacetone (1, 2) was used as an extractant but at pH > 7.0 the reagent showed ionization to form a water soluble metal complex. In addition, excess of reagent showed serious interference in absorptiometric measurements. In extractions with dibenzoylmethane (2), ammonia showed strong interference and hydrolysis of metal was prevented by using EDTA as the masking agent. The extracted complex with thenoyltrifluoroacetone (1, 2) was so stable that for back-stripping, the solution was equilibrated for at least 80 hours with concentrated hydrochloric acid. The concentration of reagent used was also too high. The method of extraction with tributyl phosphate (3) had no practical utility. The extractions with diethyl ether (4) from fluoride were incomplete while those from thiocyanate media with diethyl ether (5) or amylacetate (6) were not quantitative in spite of using very high thiocyanate concentration. Thus, in all extractions sequestering agents like EDTA or tartaric acid (2) were used to prevent hydrolytic precipitation of beryllium. In many instances, a large volume of organic phase was used to ensure complete extraction; the period of equilibration was unusually long, and many ions showed strong interferences.The method we propose is simple, sensitive, selective, and applicable at microgram concentration of beryllium.It is not essential to use a masking agent or a large reagent volume. The extractions and stripping operations are fast.
EXPERIMENTALApparatus and Reagents. A type FEK-57 photoelectric filter photometer and a Cambridge pH meter with glass electrodes were used. Mesityl oxide (bp 127-132 °C) was B.D.H. Anal R.About 11.4 grams of beryllium nitrate (B.D.H. Anal. R) was dissolved in 100 ml of distilled water. Then 0.5 ml of hydrochloric acid was added to preserve the solution for longer duration. The solution was standardized gravimetrically (7). It was found to contain 5 mg/ml of beryllium. The diluted solution containing 20 Mg/ml of beryllium was prepared from stock solution by appropriate dilution.
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