according to van der WaaJs's Equation, 51^ 



Onnes *, but he does not communicate any results. It was 

 used independently by tlie author. Isothermal -v/r, r-curves 

 were constructed by means of the equation 



ir= — log e (3w — 1) + — , 



and a double- tangent drawn to each curve. The slope of 

 these tangents gave the values of it. As it was difficult to 

 read volumes exactly from the curve, values of it were 

 substituted in the " reduced " equation of state, and the 

 volumes determined by calculation. The tabulated results 

 were : — 



e. 



7T. 



w i- 



w 2 . 



O50 



00280 



0-4067 



45-62 



0-60 



0-0869 



4326 



16-72 



0-65 



01364 



0-4485 



11-16 



070 



0-2007 



04671 



7-799 



0-75 



0-2825 



04896 



5-642 



0-80 



3840 



05174 



4-162 



0-85 



0-5058 



05532 



3-113 



090 



06494 



0-6029 



2-337 



0-95 



0-8095 



0-6854 



1-744 



1-00 



1-0000 



10000 



1-000 



5. Clausius's method f applied by him to the equation 



1 



27(« + /3) 



KT v-ot Sd(v + j3) 2 ' 



may be easily adapted to the present purpose and the table 

 given by him % (w T hich appears to be very accurate) may be 

 used. He calculates at intervals of 6 = 0*01 the corresponding 



values of 



W 



and r^— , where II=/?/RT, itf = iy 



n w 



and "W = t' 2 — a. 



By comparing his equation with that of van der Waals 

 expressed in the form 



p 1 a 



5T~y-6 KT?; 2 ' 



it will be seen that the saturation constants ir, co ly and co 2 



* Kamerlhiffh Onnes, Comm. Leid. no. 66, p. 10 (lfOO). 



f R. Clausius, Wied. Ann. Bd. xiv. pp. 279-290 and 692-704 (1881). 



X Ibid. pp. 694-5. 



