164 — 



Physical Notes. 



Chr. J. Hansen 1 ) has again issued a rejoinder in the controversy between 

 F. Krafft and himself on the one hand and C. von Rechenberg 2 ) on the other. 

 The title of Hansen's paper is "On the determination of temperature and 

 pressure in distillations in vacuo". In it he endeavours to disprove 

 von Rechenberg's view that the reduction in temperature is due to loss 

 of steam owing to condensation and explains why he appears to have 

 talked of boiling points at mm. His phrase "distillation in an absolute 

 vacuum" must not be taken as meaning that the steam from the material 

 under distillation is free from pressure, because, as a matter of fact, he 

 requires the indication of the layer of steam all through. According to 

 this, the manometer-pressure, given (too low) by Krafft and his collaborators 

 should be increased by the pressure of the steam-column above the 

 thermometer-bulb. In this respect, therefore, the author agrees with 

 von Rechenberg, who had maintained that Krafft's data were useless, because 

 the values relating to pressure and temperature did not correspond. 



Krafft 3 ) also, in two papers, attacks and seeks to controvert the state- 

 ments made by von Rechenberg. We are unfortunately unable to go into 

 these matters in further detail in this Report, and we will therefore merely 

 state that Krafft, when avoiding condensation by applying some isolating 

 material where that bad conductor of heat is applied, there is only a 

 slight difference in the temperature. He thereby proves himself that the 

 differences in temperature are caused in the main by the cooling, and 

 not by gravity. 



While this Report is in the press a paper by Chr. J. Hansen 4 ) on the 

 decreases in temperature of high-molecular vapours under low pressures 

 has made its appearance, to which we intend to refer later. 



The existence of numerous data which cannot be brought into harmony 

 with the rules of Bruhl shows that considerable uncertainty still prevails 

 as regards the applicability of spectrochemical methods for investigating 

 the atomic constitution of bodies. In view of the importance of the 

 subject, K. Auwers and F. Eisenlohr 5 ) determined to submit this question 

 to a thorough examination. For the beginning, they limited their investigation 

 to the elucidation of the problem: With what degree of exactitude can 



*) Journ. f. prakt. Chem. II. 81 (1910), 282. 



2 ) Comp. Report April 1910, 158. 



3 ) Ibidem 425 and 440. 



4 ) Zeitschr. f. physik. Chem. 74 (1910), 65. 

 b ) Berl. Berichte 43 (1910), 806. 



