Chemistry and Physics. 95 



Salts. — Some years ago, Goldstein showed that many salts be- 

 came colored under the influence of the kathode discharge, and 

 that the salts so colored possessed the property of losing negative 

 electrification readily when subjected to the influence of bright 

 light. More recently, Giesel* has obtained a similar coloration by 

 subjecting the salts to the action of sodium or potassium vapor. 

 Elster and Geitel have now shown that the salts colored by 

 Giesel's method also show the photoelectric peculiarity observed 

 in those colored by the kathode discharge. They have also 

 noticed it in the case of some naturally colored specimens of rock 

 salt. Hence it would appear probable that the coloration is due 

 to a dilute solution of the metal in the solid salt, even though no 

 indications of alkalinity in solutions of these colored salts were 

 found by Abegg. There appears to be no evidence in support of 

 Kreutz's view that the presence of iron salts is the cause of the 

 coloration. — Ann. JP/iys. Chem., II, Ixii, 599-602, November, 1897. 



G. F. B. 



5. On Combustion in Rarefied Air. — Experiments have been 

 made by Benedicenti upon the combustion taking place in a 

 lamp fed with olive oil burned under various atmospheric pres- 

 sure, with the object of elucidating the question of combustion 

 at high altitudes. He finds that combustion is just as complete 

 under 360 mm pressure, corresponding to an altitude of 6000 

 meters, as at ordinary pressures, the only difference being that the 

 speed of combustion is less at the lower pressure. Moreover no 

 appreciable increase occurs in the quantity of carbon monoxide 

 produced as the pressure diminishes. — Real. Accad. Line, V, v, 

 i, 40, 1S9G ; J. Chem. Soc, Ixxiv, ii, 215, May, 1898. g. f. b. 



6. On Molecular Masses of Solid Substances. — On comparing 

 the densities of a number of solid organic substances, Traube has 

 been able to show that the volume of the group CII 2 is practically 

 the same in solid as in liquid compounds. It we assume that this 

 holds good also for the atomic volumes of the elements, it be- 

 comes possible to calculate the co-volumes for a number of solid 

 substances. This done, the result appears that the co-volume forthe 

 solid state appears to have about half the value which it pos- 

 sesses for liquids. But since a diminution of the co-volume on 

 solidification can be due only to the association of molecules, it is 

 assumed by the author that the co-volume in the solid state is in 

 reality equal to that for the liquid state, Avogadro's law holding 

 for the solid state. From this he is able to calculate the associa- 

 tion factor for the compounds referred to, and finds that it is 

 roughly equal to 2 ; all these compounds, therefore, in the solid 

 form being bi-molecular. This conclusion appears to be con- 

 firmed by a comparison of a number of inactive racemic com- 

 pounds, which are undoubtedly bi-molecular, with the cor- 

 responding active components. Since these latter are found to 

 have the same co-volumes, they also must be bi-molecular. Ap- 

 plying to inorganic salts the same method, it follows that those 



* See this Journal, TV, iv, 152, August, 1897. 



