exchange on Dowex 50. Under these conditions 90% of the capacity of 20-24 Dowex 50 may be exhausted in 33 sec. in the Na-H exchange.Additicmal experimental work at high solution concentrations, at various temperatures, and at various particle sizes is required to complete the study of the exchange rate of Dowex 50. Conclusions 1.Ion exchange equilibrium and rate for Dowex 50 have been shown to be consistent with the hypothesis that the resin phase is equivalent to a highly ionized salt solution.2. Assuming activity coefficients equivalent to those in strong chloride solutions, the ion exchange equilibrium data may be interpreted by the Donnan concept of membrane diffusion.3. The concentration of diffusible anions in the resin phase is lower than in the solution phase, as anticipated by the Donnan theory, but quanti-tative agreement with the theory is not obtained ni dilute solutions.4. At low solution concentrations the exchange rate for Dowex 50 is controlled by the mass action reaction rate between the ions at the surface of the particle. The driving force is the product of the activity of one ion in the resin phase and the activity of the second ion in the solution phase. The rate constant depends on the turbulence of the solution phase at the resin surface, the surface area, etc., and hence is constant only under a specified set of experimental conditions.5. The diffusion rate of hydrochloric acid and sodium chloride in the resin phase is about one fifth as great as in dilute aqueous solution. This rate indicates that interdiffusion of ions in the resin phase should be controlling in the exchange rate at solution concentrations above about 0.1 molal. Midland, Mich.
Vol. 69 the elution curves. on continued use. Phenol seemed to meet these requirements and was tested quantitatively.Spore cultures of Aspergillus 'oryzae and of Aspergillus niger were used for massive spore inoculation of 0.5% citric acid solution adjusted to pH 4.0 with ammonium hydroxide. The following concentrations (g. per 100 ml.) of phenol were added to the citrate solution; 0, 0.01, 0.02, 0.03, 0.05, 0.07, 0.10, 0.20, 0.30, 0.50, 0.70 and 1.0.Growth was evident in the first three in twentyfour hours. After six days, there was some growth in 0.03 and a slight trace in 0.05 but no growth in the higher concentrations; the same situation was
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