Separation and spectrophotometric determination of trace quantities of lithium in high-purity beryllium and beryllium...

A spectrophotometric method is described for the determination of trace quantities of lithium in beryllium metal and its oxide. Lithium is selectively separated from beryllium by extraction from 1M potassium hydroxide solution into 0.1M dipivaloylmethane in diethyl ether. Fluoride, added before the extraction, successfully masks the beryllium; as little as 3 microg of lithium can be separated from as much as 1 g of beryllium. The lithium is then back-extracted into 0.1M hydrochloric acid and is determined spectrophotometrically with o-(2-hydroxy-3,6-disulpho-1-naphthylazo) benzene arsonic acid, Thoron. In an acetone-water medium Beer's law is obeyed over the range 0.1-1.0 microg ml. The method has been applied successfully to the determination of lithium in concentrations as low as 3 ppm; the relative standard deviation for the determination of 200 ppm is 3%.