Precise coulometric determination of acids in cells without liquid junction. Part IV. The assay of primary standard sulphamic acid

Abstract

The precise (1 to 2 p.p.m.) location of the end-point in the pre-titration of the supporting electrolyte and in the titration of sulphamic acid has been examined, and d.c. differential electrolytic potentiometry gives excellent results. The methods and simple apparatus previously described in Parts I, II and III are applied to the assay of primary standard sulphamic acid previously collaboratively assayed by mass titrimetry, and give results with an accuracy and precision of 100 p.p.m., and a 95 per cent. confidence level of 0·02 per cent., but with a positive bias of 0·014 per cent., the reasons for which are canvassed. The method is of high merit; it is simple, fast and direct, and is capable of further refinement.