Flame Photometric Determination of Lithium, Rubidium, and Cesium in Silicate Rocks

Abstract

For the flame photometric determination of the trace alkali elements, lithium, rubidium, and cesium, in silicate rocks, the alkali metals and magnesium are separated from the other rock constituents by sulfuric acid and hydrofluoric acid decomposition followed by precipitation of the ammonia group with solid calcium carbonate. Calcium is removed from the filtrate by precipitation of the sulfate in 50% ethyl alcohol. The alcohol is removed from the final filtrate by evaporation and the salts are dissolved in water.Flame interference from sodium and potassium is compensated by use of appropriate standard solutions.The method shows a precision and accuracy within 10% in the range from 10 to 200 p.p.m. of the alkali metal and is sensitive to 5 p.p.m. of lithium, 10 p.p.m. of rubidium, and 5