Rates of phosphate adsorption to PT-A (a new type of aluminium oxide hydroxide) and ALG (aluminum hydroxide gel) from a pH 3 phosphate solution were measured by a batch method. Phosphate uptake progressed mainly by the adsorption mechanism for PT-A, but dissolution of aluminum and precipitation of aluminum phosphate took place in addition to phosphate adsorption for ALG. The intraparticle diffusivities (Dp'S) of phosphate were evaluated from the time courses of adsorption using the model of pore diffusion with a Freundlich-type adsorption isotherm. The Dp values were approximately 7 x 10(-7) cm2 S-1 for PT-A and 1 x 10(-6) cm2 s(-1) for ALG. The tortuosity factors calculated from a model of parallel plate pore were 5.1 for PT-A and 6.7 for ALG; these values resembled those for porous inorganic ion exchangers. The adsorption rates are high enough for each of the samples to be utilized as a phosphate adsorbent to prevent hyperphosphatemia in patients on chronic dialysis. PT-A is favored as a phosphate adsorbent because of its high chemical stability against acid.

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A new chemical sensing system using an electrical oscillator has been developed. This sensing system measures the electrical ‘non‐linearity’ at the surface of an electrode immersed in a test solution: a sinusoidal voltage is applied to the electrode and the higher harmonics of the output current are obtained by Fourier transformation. This sensing system has been used to detect and quantify surfactant molecules in solutions. The relative intensity P2/P1 of the peaks of the second (P2) and first (P1) harmonics in the output current was found to be linearly correlated with the logarithms of the concentrations of cationic surfactants such as cetylpyridium bromide (CPB) and cetyl‐N,N,N‐trimethylammonium bromide (CTAB), but not with those of the anionic surfactant sodium dodecyl sulfate (SDS) or the neutral surfactant Triton X‐100. The reproducibility of this sensing system was shown to be excellent.