126 SCIENCE PROGRESS 



lead, it in no way alters the validity of the high value found 

 by Richards and Lambert for lead from definitely radioactive 

 minerals. 



In the same school the atomic weights of cadmium, praseo- 

 dymium, carbon, and sulphur have also been the subjects of 

 revisory investigations. 



An electrolytic determination of cadmium in cadmium 

 chloride led to a slightly higher value than the present inter- 

 national figure, and a value 0*3 higher than the accepted value 

 was obtained for praseodymium as a result of the analysis of 

 the pure chloride. Prof. Richards {Jour. Am. Client. Soc. 191 5, 

 37, 95) has obtained the value 12*000 for carbon (Ag = 107*880, 

 Na = 22*995), as compared with the standard value 12*005, by 

 means of the reactions between sodium carbonate and hydro- 

 bromic acid on the one hand, and between hydrobromic acid 

 and silver nitrate on the other. A value 32*065 for sulphur, 

 which he regards as the most trustworthy value hitherto re- 

 corded, was obtained by means of the reaction between sodium 

 carbonate and sulphuric acid. 



The extended search which is being made by the Dutch 

 school of chemists, led by Cohen, for the presence of allotropic 

 modifications in metals hitherto unsuspected of possessing this 

 property has been extended to potassium. From observations 

 {Kgl. Akad. Wet. Amst. 191 5, 17, 11 15) on its coefficient of ex- 

 pansion, it is concluded that a modification, ft potassium, is 

 present in ordinary samples of the metal. The new modification 

 passes into the ordinary form at about 59°'5 C, so that the metal 

 as it is commonly encountered must be regarded as metastable. 

 Advance in a similar field is due to Angel {Bull. Soc. Cliim. 191 5, 

 17, 10), who has succeeded in producing a new violet-grey form 

 of selenium by rapid cooling of the vitreous variety after heating 

 to 220 C. This new form possesses a remarkable photoelectric 

 sensitivity, but, as might be expected, is very unstable. 



Of exceptional interest is the thorough though fruitless 

 search for an unknown alkali metal to fill the vacant place in 

 the Periodic Table below caesium. Prolonged fractional crystal- 

 lisation of a large quantity of caesium nitrate obtained from the 

 mineral polluxite (Baxter, Jour. Am. Client. Soc. 1915, 37, 286) 

 failed to give any indications of the presence of an allied metal of 

 higher atomic weight in the least soluble fractions. 



From the few papers on inorganic chemistry appearing in 



