1 4 6 D O C U M E N T 1 5 7 A P R I L 1 9 2 2 polarization forces is just as secure as the fact of electrostriction. The order of mag- nitude of these forces fits excellently with the observed attractions in the noble gases. Even their temperature development is described, as far as current observa- tions go. What forces us in this situation to first want to anticipate a future, still very arbitrarily, formulizable theory for what the existing one today has long since achieved? This, when we are already certain that even in that future theory the polarization forces will continue to play their old role! Best regards, yours, P. Debye 1 addendum:[4] “Even in the useful equations of state by D. Berthelot and lately by Wohl , the volume correction and the pressure correction occurs, similarly in van der Waals.[5] Although the former poses hardly any basic difficulties of comprehension, we are kept entirely in the dark about the effect of the molecular forces, regarding both their nature and the law governing their forces. Nor can I detect any essential advancement in the experiment recently done by Debye (Physik. Zeitschr. 21, 178 (1920)),[6] if only for the reason that by attributing the attractive forces to a kind of electrostatic influence of the individual molecules, the author arrives at forces that are independent of temperature, consequently at van der Waals’s formula. But a useful theory, even if only for weakly compressed gases, would necessarily have had to lead back to D. Berthelot’s formula.[7] One can demonstrate, e.g., that the molecular forces in gaseous hydrogen act c. 50 times more weakly in the vicinity of 1000° than near boiling point for this Debye’s theory offers no explanation.[8] 156. From Maja Winteler-Einstein Quinto pr. Firenze 5 via Strozzi, 20-IV-22. [Not selected for translation.] 157. To Paul Ehrenfest [Berlin,] 21 April 1922 Dear Ehrenfest, Many thanks for the English letter and your statement about it.[1] Of course a Hamilton edition merits being published. Now Ilse showed me your postcard with the comment that St. John wants to come in June.[2] Well, we have a problem:
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