Febeuaet 21, 1908] 



SCIENCE 



293 



Equilibrium in the System Silver Nitrate 

 and Pyridine: Louis Kahlenbeeg and 

 Robert K. Brewer. 



The entire curve of equilibrium was de- 

 tei'mined from the freezing point of pyri- 

 dine —48.5° to 110° C. From —65°, the 

 freezing point of the saturated solution to 

 — 24° a solid of the composition AgNOj • 

 6C5H5N is in equilibrium with the solu- 

 tion. From —24° to +48.5° the solid in 

 equilibrium with the solution is AgNOj • 

 3C5H5N. From +48.5° to +79°, AgNOj • 

 2CgH5N is in equilibrium with the solu- 

 tion; and above the latter temperature 

 pure AgNOs is in equilibrium with the 

 solution. 



Note on the Solubility Product: Julius 



Stieglitz. 



Arrhenius's work {Zt. phys. C/i.,XXXI., 

 197) on the solubilities of silver salts of 

 the fatty acids in the presence of sodium 

 salts of the same acids destroyed the last 

 vestige of the theoretical foimdation of the 

 solubility product constant by showing 

 that the solubility Cmoi of the non-ionized 

 salts is not a constant, but decreases with 

 the increased concentration of salt solu- 

 tions. A decreasing molecular solubility 

 Cmoi and an increasing value for C'X 

 C/Cmoi as is found for strong electrolytes 

 is consistent with a constant solubility 

 product C'XC and the author shows that 

 satisfactory constants are obtained for each 

 of the silver salts by calculation from the 

 data of Arrhenius. Such a constant, even 

 if only an empirical and not a natural con- 

 stant, is of great practical value in work 

 on solubilities. 



Tivo New Methods of Determining the Sec- 

 ondary Ionization Constants of Dibasic 

 Acid: Herbert N. McCoy. 

 1. The concentration of the free acid in 

 an aqueous solution of the normal and acid 

 sodium salts of a weak dibasic acid is 



found by partition with an immiscible sol- 

 vent. Titration of the aqueous solution 

 gives the remaining data for the calcula- 

 tion of the ionization constant of the sec- 

 ond hydrogen ion. 



2. This same constant may also be cal- 

 culated from the values of the equivalent 

 conductances of very dilute solutions of 

 the normal salt and the acid salt. The 

 results of the two methods agree with one 

 another and also with those obtained by 

 other methods as well as could be expected. 



The Preparation of TJrano-uranic Oxide 

 and a Standard of Radioactivity: Geo. 

 C. Ashman and Herbert N. McCoy. 

 Pure UO is obtained by igniting pure 

 uranyl oxide in an electric muffle at 650 to 

 700° C. At much lower temperatures de- 

 composition is incomplete, at higher tem- 

 peratures oxygen is slowly lost. Standards 

 of radioactivity consist of films of the oxide 

 UO about 40 sq. em. in area and 0.7 to 

 0.9 g. in weight, deposited by a special 

 process, on flat, circular plates of copper. 

 Films so made having equal area, have 

 identical activity. The ray activity due 

 to 1 sq. em. of such a film is taken as the 

 unit of radioactivity. 



The Three Component System— CuO, SO3, 

 H2O at 25 Degrees: J. M. Bell and "W. 

 C. Taber. 



Purified copper oxide or copper hydrox- 

 ide was added in excess to a solution of 

 copper sulphate, and the solid and liquid 

 phases analyzed for copper and sulphuric 

 acid after the system had come to equilib- 

 rium. In plotting the results on a tri- 

 angular diagram, by joining the corre- 

 sponding points of the solid and liquid 

 phases, it was found that the lines did not 

 meet within the triangle, indicating that 

 the solid phases consist of a series of solid 

 solutions, and are not definite chemical 

 compoimds of the nature indicated by the 



