296 Scientific Intelligence. 



be satisfactorily explicable upon the hypothesis of a hydrolytic 

 dissociation or on that of molecular aggregates. — Phil. Mag., V, 

 xxxiii, 317; J. Chem. Soc, lxiv, II, 149, April, 1893. g. f. b. 



2. On the Separation of Gases from each other under the 

 irifluence of the Electric discharge. — It has been observed by 

 Baly, that on passing the electric discharge through a vacuum- 

 tube containing only a small quantity of hydrogen the hydrogen 

 lines are observed only in the spectrum of the negative glow and 

 not at all in the body of the tube. This as he shows is due to an 

 accumulation of the hydrogen about the negative electrode; and 

 by employing tubes or suitable shape containing mixtures of car- 

 bon dioxide and hydrogen at about # 75 mm pressure, he has suc- 

 ceeded in effecting so complete a separation of the hydrogen that, 

 on sealing off the portion of the tube containing the positive elec- 

 trode, only a trace of hydrogen can be detected in it by spectro- 

 scopic tests. Mixtures of hydrogen with other gases, such as 

 nitrogen, carbon monoxide, sulphur dioxide, iodine, and mercury 

 vapor behave similarly. When a mixture of carbon monoxide 

 and carbon dioxide is used, the former gas separates at the nega- 

 tive electrode. When nitrogen is mixed with the carbon dioxide, 

 the separation of the two is very complete. Moreover sulphur 

 dioxide and carbon dioxide may be thus separated. Air must be 

 highly rarefied before separation begins and then the oxygen 

 appears to go to the negative electrode. No relation could be 

 observed between the molecular masses of the constituent gases 

 and the separation of the mixtures. The author points out an 

 apparent connection between this kind of separation and striated 

 discharges ; the striae being strongly marked only when separa- 

 tion occurs and never appearing if the contents of the tube re- 

 mains homogeneous. If the negative electrode be made a mere 

 point so as to prevent the formation of a glow around it, no stria- 

 tion nor separation is observed. Moreover pure gases do not 

 stratify, iodine, sulphur, arsenic and mercuric iodide giving only a 

 phosphorescence throughout the tube. Prepared in a state of 

 considerable purity, hydrogen itself showed but traces of stria- 

 tion ; and from this the author concludes that pure hydrogen 

 would not stratify at all, stratification being a phenomenon due 

 to the separation of two gases. — Phil. Mag., V, xxxv, 200 ; J. 

 Chem. Soc, lxiii, II, 253, June, 1893. g. f. b. 



3. On the Determination of Molecular Mass from the Pate 

 of Evaporation. — It is well known that when a non-volatile sub- 

 stance is dissolved in a fairly volatile liquid, the rate of evapora- 

 tion of this liquid is decreased. This result may probablv be 

 attributed to the fact that in the case of the solution, the surface 

 exposed is composed partly of the molecules of the volatile sol- 

 vent and partly of the molecules of the non-volatile dissolved 

 substance ; while when the solvent alone is exposed to evapora- 

 tion its surface consists wholly of volatile molecules. Evidently 

 therefore the greater the number of non-volatile molecules the 

 less the evaporation. In other words, the rate of evaporation of 



