Chemistry and Physics. 587 



contained less than 0*01 per cent of impurities, which is a very 

 satisfactory result. The zinc and cadmium had been purified by 

 distillation, the tin by electrolysis, and the lead by the reduction 

 of a pure salt. The author classifies commercially pure metals 

 into grades of purity, a maximum of 10 per cent impurity repre- 

 senting the first grade, while maxima of 1 per cent, 0*1 per cent, 

 and 0-01 per cent represent the second, third and fourth grades, 

 respectively. He remarks that technical products of the fourth 

 grade, that is with less than 0*0 1 per cent of impurities, may be 

 obtained at present in the cases of gold, silver, platinum, mer- 

 cury, copper, tin, lead, cadmium and zinc. This does not take 

 into account the possible presence of small amounts of oxygen in 

 the more oxidizable metals. — Zeltschr. analyt. Chem., lxxiv, 407. 



h. l. w. 



5. The JSffect of Temperature upon Radio-active Disintegra- 

 tion. — That high temperature has no detectable influence on the 

 intensity and nature of y-rays from various radioactive sub- 

 stances has been conclusively demonstrated by the investigations 

 of Bronson, Engler, Schmidt and others. Perhaps the severest 

 test was that applied by Rutherford and Petavel, who showed 

 that the y-radiation from radium emanation exposed momentarily 

 to a pressure of about 1200 atmospheres and a temperature at 

 least as high as 2500° C, produced by an explosion of cordite, 

 was not altered at the instant of explosion. A temporary reduc- 

 tion of 9 per cent in the activity, observed after the explosion, 

 was due to a change of distribution of radium C within the bomb, 

 caused by its volatilization and subsequent condensation, and was 

 in complete agreement with the decrease calculated theoretically. 

 On the other hand, the results obtained with /3-rays have been 

 very discordant, save in one respect, namety, that high tempera- 

 ture seems to have some effect on the emission of rays of this 

 kind. Since the question is of great theoretical importance, it is 

 worthy of note that the matter has been finally settled by the 

 systematic investigation of Alexander S. Russell, who under- 

 took the work at the request of Professor Rutherford. 



The furnace used consisted of a silica tube 12*5 cm long, 2*2 cm 

 internal diameter, open at both ends, and wound with a helix of 

 platinum wire. The whole was jacketed with " Kieselguhr " for 

 thermal insulation. The temperatures were measured with a 

 platinum rhodium thermo-couple. A value of 1150° C. was easily 

 attained but usually not exceeded. The radio-active materials 

 studied were sealed in quartz tubes which were suspended cen- 

 trally in the furnace by means of thin nickel wire. When thus 

 mounted there was a clear path between every point of the tube 

 and the lead electroscope, the distance being from 40 to 60 cru . 



In the case of pure radium C, deposited on nickel by von 

 Lerch's method, the decay of the radiations during three hours 

 was measured, the containing quartz tube being maintained at 

 1150° C. for the first 90 minutes, and at room temperature for the 

 rest of the time. The /3-rays were studied over the entire inter- 



