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C. (See Discussion.) Solid curves based on ion size parameter 4.3 A. for carbonate and phosphate systems dashed curves based on 6.0 A. Diameter of circles equals 0.008 in pK¡.Konopik and Leberl,18 who reported a value between 11.70 and 11.95 from colorimetric data but with very insecure treatment of activity coefficients. Both references17•18 summarize older data for historical interest.Acknowledgments.-We wish to express our appreciation to the sources listed in Ref. 2 for fellowships supporting the junior author (A.

The Hammett acidity function Hi, value has been determined for hydrogen fluoride in the concentration range from anhydrous material down to about 40% hydrogen fluoride. The dryest hydrogen fluoride prepared had an H0 value of -10.2. In the course of this investigation, improved spectrophotometric cells were developed for handling hydrofluoric acid solutions and the spectrum of anhydrous hydrogen fluoride in the near infrared was determined. The effect of sodium fluoride and water on the near infrared hydrogen fluoride spectrum was investigated and an analytical method for water in hydrogen fluoride was developed based on measurements of the water absorption at 1.95 µ.Liquid anhydrous hydrogen fluoride has long been recognized as a very acidic substance despite the fact that in dilute aqueous solution it behaves as a rather weak acid.2•3 A wide variety of compounds are readily soluble in liquid hydrogen fluoride. These solutions usually exhibit substantial ionic conductivity that can be attributed to proton transfer from the acid to the solute.Hammett has discussed the use of organic indicators for the determination of relative acidity and suggested an acidity scale based on the relative

In a paper on electrolyte effects in reactions between a non-electrolyte and the hydrogen ion2 two typical examples were given, representative of electrolyte effects in (1) reactions showing specific catalysis by the hydrogen ion, and (2) reactions showing acid catalysis in the general sense. This classification has been clarified by experiments in solutions of heavy waterla and by Pedersen's analysis of prototropic reactions.'From an examination of the electrolyte effects it appeared that the inversion of sucrose and the hydrolysis of the acetals should be considered purely as catalysis by the hydrogen ion. Evidence of catalytic effects of acid molecules has been advanced by Hammett and Paull6 and by Gross, Steiner and Suess.' Experiments on the inversion of sucrose in acetateacetic acid buffer solutions have shown, however, there is no detectable catalytic effect of the molecules of such a weak acid as acetic?If we are dealing with a case of specific hydrogen-ion catalysis, we can for aqueous solutions postulate the equilibriumwhere kz << kand the equilibrium concentration is maintained at all times. The velocity constant is given by Now K will vary with the electrolyte concentration, and the resulting change in the concentration of the collision complex will cause a change in the measured velocity constant R. These changes have been observed for the hydrolysis of the acetals and for the inversion of sucrose, but even in dilute solution they seem larger than one would expect, by analogy, from an examination of the change, with electrolyte concentration, of the dis-(1) E. I. du Pont de Nemoun and Company Fellow, 1938. (2) Riesch and Kilpatrick, J . Phys. Chcm., 89, 561 (1935). (3) For references and discussion see Bonhoeffer, Trans. Faraday (4) Pedersen, ibid., 84, 237 (1938). (5) Hammett and Paul, THIS JOURNAL, 56, 830 (1934). (6) Gross, Steiner and Suess, Trans. Faraday Soc., 83, 883 (1936). (7) These experiments were camed out in this Laboratory in 1929 Sac., 84, 262 (1938). by M. L. Kilpatrick. sociation constant of anilinium or o-chloroaniliniumPedersen determined these two equilibrium constants over a convenient range of temperature, and found no great change in the heat of dissociation (MI') with temperature, in contrast to the marked variation of the heat of dissociation with temperature for uncharged acids. By analogy it might be expected that for reactions between a non-electrolyte and an ion, as represented by equation (1) , there would be little change with temperature in EA, the heat of activation computed from the integrated form of the Arrhenius equation (3)where k T , and kT, are the velocity constants at temperatures TI and Tz, respectively. This seems to be the case for the hydrolysis of diethyl acetals2An examination of the extensive literature on sucrose inversion (on which some excellent experimental work has been done) yields a n q b e r of surprises. For example, in a recent number of THIS JOURNAL we have "The activation energy of 25.7 f 0.05 kcal. found in the present work on sucrose is i...

The rate of decomposition of ozone in aqueous perchloric acid has been measured spectrophotometrically, iodometrically and manometrically, and found proportional to the three-halves power of the ozone concentration, in agreement with the reaction scheme proposed by J. Weiss. In connection with the kinetic experiments, the molar extinction coefficient of ozone at 260 m/ , and the Henry's law constant, have been determined for solutions of ozone in 0.01 M HClOi. As in the case of hydrogen peroxide, it is difficult to obtain reproducible rates of decomposition from day to day, and the greater (1)