The flame-photometric determination of alkalis in ceramic materials

Abstract

The flame-photometric method in general use for the determination of alkalis in the ceramic industries was originally devised for the EEL, Model 100, flame photometer, with a coal gas flame, which is not now generally available. Current supplies of town gas, propane and methane (natural gas) flames are compared and interferences evaluated. Perchloric and hydrochloric acids are found to have a depressant effect; sodium is enhanced by potassium and is subject to spectral interference by calcium.

Propane is chosen as the preferred fuel. The effect of chlorine-containing acids is eliminated by the use of sulphuric and nitric acids for the initial decomposition and the spectral interference from calcium by the addition of aluminium sulphate; sodium-potassium inter-element effects are eliminated by the use of a caesium buffer. Although the procedure is principally devised to give optimum results with aluminosilicates, its extension to high-lime materials is also considered.