A systematic study on the analysis of binary acid mixtures by extraction method has been made, using ethyl ether as extractant.It has been shown that, as ordinarily carried out, this method is not applicable to systems containing strong acids.Based on the assumption that in systems containing a very weak and a strong acid, the extraction constant of the former would remain constant while that of the latter would vary with its own concentration, two procedures were proposed for such systems: (a) by successive approximation and (b) by addition of sulphuric acid.Both were found to be satisfactory.In order to test the validity of the fundamental assumption of these two procedures, a graphical method was proposed.It not only confirms the assumption but is also more accurate and coavenient whan both (a) and (b), the maximum deviation from the theoretical value being within 0.4%.When the mixture contains two strong acids, neither of the above methods is satisfactory.For such systems a standard curve method was proposed and studied in detail.Depending on the nature of the solutes, this method can be used either simply or with addition of sulphuric acid to yield satisfactory results.