This paper describes a simple pocket size spectroanalytical calculator developed, in the authors' laboratory for the rapid and direct conversion of spectral line blackenings to percentage constituents. This calculator speeds up production control analysis and is considered convenient for trial of spectromethods in process of development. It is prepared in the form of a handy slide rule in which the emulsion calibration plot is replaced by a scale. While the calculator can be drawn up for any method, the scales illustrated are for low alloy steels and for aluminum Alcoa types A51S, 52S, 53S, S6S and 61S as currently used in the Material Laboratory.
