[ 517 ] 



XLT. On the Saturation Constants according to van tier 

 Waalss Equation. By John P. Daltox, M.A., Carnegie 

 Research Scholar *. 



A. Deduction of Constants. 



FOR the deduction of the saturation constants 6, 7r, «! 

 and Q) 2 , the following different methods are available 

 and have been used : — 



1. M. PJanck's method for the equation of Clausius may 

 be adapted to that of van der \Yaals. For this purpose an 

 independent variable $ is chosen, such that 



3o> x — 1 = 3?' sin 2 },<$>, 



and 



?)(o 2 — I = 3r cos 2 Jr<£. 



Since 



hence 



Also 



and 



Sd _ 3 _ _ Sfl 

 3©! — 1 'a* 3a» — 



3 



2 1 [~cos cf) + sin 2 4> • log tan 4-c£ 1 



3 sin 2 </> L log tan ^(f> + cos <£ J 



it = 



ScL'oCt), — co 2 — COi 



a (ft) 1 +« 2 )(«^2 — 1)(3&), — 1) 



t7 = q g S~ -. 



TThen = 90°, o) 1 = 1 = g>o, hence values of <j) must so be 

 chosen that 90°>c£>0. 



This method was used by A. Stoletow £ who calculated 

 pressures only, and gave the following results : — 



$• 



o. 



7T. 



80° 



0-9960 



0-934 



70 



09861 



0-945 



65 



O9780 



0-914 



60 



09677 



876 



55 



0-9549 



0-829 



50 



0-9395 



0776 



* Communicated bv Prof. J. P. Kuenen, Ph.D. 



t M. Planck, Wied. Ann. Bd. xiii. pp. 5:35-543 (1881). 



% A. Stoletow, J. de russ. phys. Ges. xiv. p. 167 (1882). 



