Intelligence and Miscellaneous Articles. 459 



and the dilution extended to 2G50 litres, the rosolates were in the 

 presence of an equivalent of free base, and the hydrolysis was 

 sufficiently avoided. Unlike the previous great deviations these 

 solutions showed now only small differences. 



The salts of the following groups showed finally equal spectra : 

 (4) Diazoresorcine, (5) Diazoresorujine, (6) Chromoxalates. The 

 absorption is relatively small ; the investigation was therefore 

 made by the photographic method. The chromoxalates all exert 

 an absorption in the violet and ultraviolet. The boundaries had 

 all the same position with the exception of the solutions of copper 

 and aluminium salts, which exceptions the author ascribes to a 

 hydrolytic decomposition. 



(7) Safrosine. — Here again the aluminium and copper salts show 

 a deviation which is distinct with the former and just perceptible 

 with the latter. 



(8) p-Rosaniline, (9) Aniline Violet. — The different intensity 

 of the absorption-spectra which the salts of some acids show is 

 explained by their insolubility. 



(10) Chrysaniline, (11) Chrysoidine. — The salts of this last 

 group which were prepared with various acids showed a develop- 

 ment like that observed with rosolic acid. They have different 

 spectra, which, however, assume the same appearance, if the solution 

 contains an equivalent of the acid in the free state along with 

 the neutral salt. The deviations originally observed may be referred 

 to an hydrolysis. — Abhandl. der Kgl. Sachs Gesellscliaft, vol. xviii. 

 p. 281, 1892. Bulletin der Physik, ]\ T o. 8, p. 534, 1892. 



ON THE PHYSICAL SIGNIFICATION OF h IN VAN DER WAALS' 

 EQUATION. BY E. HEILBORN. 



What is called the covolume of gases, b, is proportional, as gene- 

 rally accepted, to the space u occupied by the whole of the 

 molecules contained in the unit volume. It may therefore be 

 written 



b = A ie, 



where A is a constant for all gases. Van der Waals finds (" On the 

 Continuity of the Liquid and Gaseous States of Matter," p. 384 of 

 the English translation) from considerations based on the theory 

 of probabilities the number 4, while O. E. Meyer (Kinetische 

 Theorie der Gase, p. 298), also from theoretical considerations, 

 deduces 4 V2. 



To decide this question we may utilise the equation deduced by 

 Dorn and Exner, 



_ n 2 -l 



H - >2 2 + 2' 



