Chemistry and Physics. 361 



elements from different sources have never shown differences in 

 atomic weight. The samples of lead chloride from the radio- 

 active minerals showed no spectroscopic differences from ordinary 

 lead chloride except the presence of a trace of copper, too minute 

 to have any effect upon the atomic weight, but the samples showed 

 radioactivity, which w r as very slight in the freshly crystallized 

 lead chloride, but increased with time and reached a maximum in 

 about 30 days. 



Attention should be called to the work of Soddy and Hyman, 

 noticed on page 91 of this volume, according to which the lead 

 from Ceylon thorite gave an atomic weight of 208*4. According 

 to the calculations, the lead derived from uranium should have 

 an atomic weight of about 206, and that from thorium about 

 208. Therefore, the results mentioned in this notice appear to 

 confirm the theory in regard to the radioactive transformations. — 

 Comities JZendus, clviii, 1676 ; Jour. Amer. Chem. Soc, xxxvi, 

 1329. h. l. w. 



2. Tico New Modifications of Phosphorus. — P. W. Bridgeman 

 has obtained two new modifications of phosphorus during an 

 investigation of the effect of high pressure upon the melting- 

 point of ordinary w T hite phosphorus. The new modification of 

 white phosphorus, which is called " white phosphorus II," was 

 first produced by increasing the pressure on ordinary white phos- 

 phorus to 11,000 kg. per cm 8 at 60° C. Its existence w T as shown 

 by a discontinuous change in the volume at this pressure, and the 

 transition, which is reversible, was found to take place at lower 

 pressures as the temperature was lowered, until it occurred at 

 atmospheric pressure at about —80°. The appearance of this 

 new form in bulk is much like that of ordinary white phosphorus, 

 but it may be a trifle yellower, and there are liable to be cracks 

 formed, as there is a volume contraction of about 2 per cent when 

 the transition occurs. Evidence was obtained that this new form 

 probably crystallizes in the hexagonal system, the usual form 

 being regular in its crystallization. The other new form of 

 phosphorus, called "black phosphorus," is more interesting than 

 the first one on account of its color and other properties, and also 

 on account of the fact that it is stable when once formed. It 

 was discovered w T hen an attempt w r as made to force white phos- 

 phorus to change to red phosphorus by the application of a high 

 pressure at a temperature below that at which the change takes 

 place w T ith appreciable velocity at atmospheric pressure. At a 

 temperature of 200° C. and a pressure of 12,000 to 13,000 kg. the 

 change takes place in from 5 to 20 minutes. The black substance 

 formed has a very much smaller volume than the original white 

 phosphorus. Attempts to produce the black phosphorus from 

 red phosphorus were unsuccessful. The fracture of the black 

 phosphorus is sometimes granular, sometimes fibrous with a 

 metallic luster, very much like graphite in appearance. It was 

 found by analysis to be practically pure phosphorus, not a com- 

 pound. The most striking difference between the new black phos- 



