336 Scientific Intelligence. 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. A Method for Calculating the Boiling 'joints of Metals. — 

 The view was advanced by F. Krafft about four years ago that 

 the essential process of boiling in a vacuum consists in overcom- 

 ing gravity, and that this, on the surface of the earth, is equiva- 

 lent to the atmospheric pressure. As a proof of this fact he 

 showed that the elements mercury, cadmium, zinc, potassium, 

 sodium, bismuth and silver require just the same addition of heat 

 to bring them from the point of the commencement of volatiliza- 

 tion in a vacuum to the point of boiling in a vacuum, as is 

 required to bring them from the latter point to the point of boil- 

 ing under atmospheric pressure. In order to obtain further 

 data in regard to this interesting relation, Krafft and Knocke 

 have determined the data under consideration for arsenic, and 

 have found : 



Commencement of evaporation, ,nm . 96° 



Sublimes at mra 325° 



Sublimes at 760 m,n 554° 



Difference in each case ... 229° 



They found with thallium : 



Commencement of evaporation, mm 174° 



Boiling-point at mm ... 818° 



Since the difference here is 644°, the calculated boiling point at 

 760 mm is 1462°. In this manner, from data furnished by Krafft 

 and his co-workers, Moissan calculated the approximate boiling 

 point of copper as 2240° and of gold as 2530°, and he found by 

 distilling in an electric furnace an alloy consisting of equal parts 

 of copper and gold, that the copper boiled off faster than the 

 gold, thus showing a lower boiling point of the copper, as indi- 

 cated by the calculation. — Berichte, xlii, 202. h. l. w. 



2. Some Properties of the Radium Emanation. — About two 

 years ago Rutherford observed that the emanations of radium, 

 actinium, and thorium were completely absorbed by cocoanut 

 charcoal at ordinary temperatures. He has recently repeated 

 this experiment with the radium emanation, using much larger 

 quantities, and has found that the actual volume of this emanation 

 capable of absorption at room temperatures is very small. For 

 example, several grams of the charcoal are required to absorb 

 completely the emanation from 200 mg. of radium at ordinary 

 temperature, although the volume of the gas is only one-tenth of 

 a cubic millimeter. As was to be expected, the absorptive 

 power of the charcoal increases rapidly with the lowering of the 

 temperature. It was found that 0*8g. of charcoal from which 



