Chemistry and Physics. 327 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. The Solubility of Pure Radium Sulphate — S. C. Lind, J. 

 E. Underwood and C. P. Whittemore, of the U. S. Bureau of 

 Mines have found that the solubility of radium sulphate at 25° 

 C. is 21 X 10~ 8 g. in 1 c.c. of water, thus placing it among 

 the least soluble of known salts. The solubility was found by 

 the measurement of the emanation, a method giving accurate 

 results, with very small quantities of solution. Concordant 

 results were obtained by directly saturating solutions with the 

 solid sulphate and by precipitating it in solutions, and in each 

 case examining the carefully filtered liquid, so that it is evident 

 that there was no supersaturation. 



The solubility of radium sulphate,' thus found, is about 1/100 

 of that of barium sulphate, and it corresponds to the expected 

 solubility derived from the solubility curve of the sulphates of 

 the family of metals, where the solubility of CaS0 4 is 209 X 10~ 2 , 

 of SrS0 4 is 1-5 X 10-* and BaS0 4 is 2-3 X lO^ 5 . Now it 

 is known that when a solution containing a mixture of barium 

 and radium salts is partially precipitated by means of a sulphate, 

 the ratio of radium to barium is the same in the precipitate 

 as in the original solution, a result that is entirely contrary to 

 the usual behavior of precipitates of such different solubility. 

 Moreover when both barium and radium are completely pre- 

 cipitated as sulphates from solutions containing radium and 

 barium in the proportion 1 to 1,000,000, the filtrate contains only 

 about 10 -12 g. of radium per cubic centimeter, an amount 

 much smaller than that to be expected from its solubility. 

 There appears to be no perfectly satisfactory explanation of 

 these unexpected relations. 



Another rather peculiar circumstance has been brought out in 

 this investigation in the fact that an excess of sulphuric acid has 

 little or no effect upon the solubility of radium sulphate until 

 the acid is of more than 50 per cent strength, when the solubility 

 begins to increase rapidly. The usual effect of the mass-action 

 of a common ion in diminishing the solubility is therefore 

 apparently absent in this case. The solubility of radium sul- 

 phate in sulphuric acid solutions up to 25 per cent acid increases 

 by about one-half from 25° to 35° and again to the same extent 

 from 35° to 45° C. — Jour. Amer. Chem. Soc, 40, 465. 



h. l. w. 



2. The Specific Heats at Low Temperatures of Several 

 Metals. — E. D. Eastman and W. D. Eodebush have studied the 

 specific heats of sodium, potassium, magnesium and calcium in 

 reference to the law of Dulong and Petit. This law states that 



