INDIRECT TENSAMMETRIC METHOD FOR THE DETERMINATION OF NONIONIC SURFACTANTS .3. PROPERTIES OF THE ANALYTICAL SIGNAL OF MIXTURES OF NONIONIC SURFACTANTS

Seven binary and three multi-component mixtures of non-ionic surfactan ts and a mixture of ethylene glycol and PEG 400 were investigated usin g tensammetry with ''normal'' recording and one binary mixture by usin g ''reverse'' recording. Within the initial section of the Gamma-shape d calibration graph, the investigated mixtures show no or small deviat ions from the plot for the standard (Triton X-100) and most of the mix tures show good additivity. In the case of two mixtures showing deviat ion from additivity the results deviated less from the plot for the st andard than would be expected presuming additivity. Within the range 0 .1-1.0 mg l(-1) the mixtures can be determined using a Triton X-100 ca libration graph without serious error. The shape of the calibration gr aph as a whole depends strongly on the average number of oxyethylene s ubunits of a mixture, but depends only slightly on the molecular weigh t distribution of the mixture. Therefore, the behaviour of polydispers e surfactants can be simulated by a mixture of two different polydispe rse surfactants.