Chemistry and Physics. 165 



being brought into contact with n molecules of sodium chloride 

 produces x molecules of hydrogen chloride and sodium acetate, 

 then d 2 x d 3 xz=zd 1 (1— x) d t (n— x) ; a result agreeing with that 

 given by experiment. The author shows that it is possible to 

 deduce from this equation a value for the so-called " avidity " 

 measured by Thomsen and Ostwald, and he finds that for mono- 

 basic acids, the avidities for any given dilution are approximately 

 proportional to the degrees of dissociation of the acids at this 

 dilution. This conclusion agrees with Ostwald's results. The 

 author also points out that the theory of Guldburg and Waage is 

 applicable only to equilibrium between four electrolytes, when 

 two of them are strongly dissociated ; and further that one ol 

 the conclusions of this theory, that the avidities of acids are pro- 

 portioned to the square roots of their affinity-coefficients, is incor- 

 rect. Since the decomposition of certain salts by water, ob- 

 served by Walker to follow the ordinary laws of mass action, 

 takes place in accordance with the equation given above, it seems 

 necessary to assume that water is an electrolyte and is partially 

 dissociated. — Zeitschr. Physik. Chem.,v, 1, Feb., 1890; J. Oh. 

 tioc, lviii, 437, May, 1890. G. f. b. 



4. Coincidences between lines of different spectra. — Professor 

 Rttnge of the Technical High School in Hanover examines meth- 

 ods given by various authors for discriminating real from acci- 

 dental coincidences between the lines of different spectra, and 

 applies the result of his own analysis to Griinwald's speculation 

 on the composition of the elements. It will be remembered that 

 Griinwald believed that his hypothesis was most strongly sup- 

 ported by the agreement between the wave-lengths of the lines 

 in the spectrum of water, as deduced by him from those of the 

 hydrogen spectrum, and their values as obtained by observation. 

 Professor Runge, however, finds that the distribution of differ- 

 ences is in perfect accordance with the one expected for an equal 

 number of wave-lengths chosen at random. The distribution of 

 differences gives no more reason to believe the coincidences real 

 "than to believe in a connection between the mantissas of log sin, 

 and the spectrum of water." — Phil. Mag., June, 1890, pp. 462- 

 466. j. t. 



5. Hertz's experiments. — L. Boltzman shows the experiments 

 of Hertz to a large audience, even when the primary circuit is at 

 a distance of 8*7 meters from the secondary circuit, by making 

 the minute sparks in the secondary circuit connect the pole of a 

 battery with an electroscope. As long as no spark passed be- 

 tween the terminals of the secondary circuit, the electroscope 

 remained uncharged by the battery. When the circuits were 

 36*8 meters apart, it was estimated that the length of the sec- 

 ondary spark was -g-oVo of a millimeter. The method employed by 

 Boltzman serves also to examine interference phenomena. — Ann. 

 der Physik und Chernie, No. 6, 1890, p. 399. J. t. 



6. Stationary light waves. — Otto Wiener, by the employ- 

 ment of a peculiar photographic process, has succeeded in show- 



