CHEMISTRY 127 



iodide and various alkylammonium salts are as highly ionised in formamide as in aqueous 

 solution. The equivalent conductivity for a salt dissolved in an organic solvent increases 

 with dilution, and the limiting value Xco may be deduced, as for aqueous solutions, on 

 the basis of a linear relationship between the equivalent conductivity and the cube 

 root of the concentration (see Philip and Courtman, /. Chem. Soc., 1910, 97, 1261; 

 Walden, Zeitsch. physikal. Chem., 1911,75, 257). Walden confirms the general validity 

 of the rule according to which the product of Xoo for a given salt and the viscosity of 

 the solvent is a constant. 



The evidence bearing on the validity of Ostwald's dilution law as applied to acids 

 in aqueous solution (see E. B. ix, 217 et seq., 'article " Electrolysis ") has recently been 

 examined by Kendall (/. Chem. Soc., 1912, 101, 1275), who finds that the most probable 

 value for the ionic conductivity of hydrogen is 347.2 at 25 (313.9 at 18). A new dilu- 

 tion formula, shown to be in harmony with the experimental conductivity data for 



acids of all types, is proposed, viz: -, r- =k+c , where k and c are constants 



(i m; v m 



for each acid, and m is the coefficient of ionisation. 



The position of colloidal solutions, relatively to crystalloidal solutions on the one 

 hand and to mechanical suspensions on the other, has been made clear with the help 

 of the ultramicroscope. The movements of colloidal particles are in harmony with the 

 assumptions of the kinetic theory, and the agreement between the observed and calculat- 

 ed values for trfeir velocity amounts to a proof of the kinetic nature of heat (see Brownian 

 Movement and Molecular Reality, by Perrin, 1910; Ostwald's Outlines of General Chem- 

 istry, p. 485), : 



In connection with the osmotic activity of colloids, the case of Congo red especially 

 has been investigated (Bayliss, Proc. Roy. Soc., B., 1909, 81, 269; 1911, 84, 229; Biltz, 

 Zeitsch. physikal. Chem., 1909, 68, 357; 1910, 73, 481; 1911, 77, 91). It seems, however, 

 that peculiar inequalities of concentration are set up on two sides of the osmotic mem- 

 brane, and it is therefore not permissible in this and similar cases to deduce the molec- 

 ular weight from the recorded osmotic pressure (see Donnan, Zeitsch. Elektrochem., 

 191 1, 17, 572; J. Chem. Soc., 1911, 99, 1554; Moore, Roaf and Webster, Biochem. J., 

 1911, 6, 10). 



The phenomenon of adsorption attracts much attention, especially since it has a 

 bearing on such practical problems as the mechanism of dyeing, the nature of the tan- 

 ning process and the purification of sewage. Reference may be made here to investi- 

 gations dealing with the adsorption of gases by charcoal (Homfray, Proc. Roy. Soc., 

 A., 1910, 84, 99; Titoff, Zeitsch. physikal. Chem., 1910, 74, 641), of sugars by charcoal 

 (Herzog and Adler, Zeitsch. physiol. Chem., 1909, 60, 79), of acids by wool (Georgievics, 

 Monatsch., 1911, 32, 655; 1912, jj, 45), of iodine by starch (Barger and Field, J. Chem. 

 Soc., 1912, lor, 1394) and of dyes by sand and natural fibres (Dreaper and Davis, /. 

 Soc. Chem. Ind., 1912, jr, 100). Experiments on the adsorption of acetic acid from its 

 aqueous solutions by charcoal show the occurrence of a maximum of adsorption. The 

 validity, therefore, of the usual adsorption formula x = kc n must be limited (Schmidt, 

 Zeitsch. physikal. Chem., 1910, 74, 689; 1912, 78, 667; Arrhenius, J. Chem. Soc., 1912, 

 102, ii, 139). 



It is well known that the course of a chemical change may be profoundly modified 

 by the presence of foreign substances. Recent quantitative study of the photochemical 

 reaction between hydrogen and chlorine has shown that this change is inhibited by oxy- 

 gen, nitrogen chloride, nitric oxide, ozone and chlorine dioxide, while carbon dioxide, 

 nitrogen, nitrous oxide and chlorine monoxide act only as diluents (see Chapman and 

 MacMahon, /. Chem. Soc., 1910, 97, 845). In several well-known cases the presence of 

 water is necessary for the occurrence of chemical change. The rate of decomposition 

 of moist ozone at 100, however, is not appreciably different from that of the carefully 

 dried gas (Chapman and Jones, /. Chem. Soc., 1911, Qp, 1811). 



Analytical Chemistry. From the mass of detail work published in this branch only 

 one or two points of general interest and importance can be selected. 



