1061 



As 1 — (/? — V,):(n — 7j) also = {n — i3) : {71 — '/.), we may 

 also write: 



n — ,i =r (« — 7,) (1 - 0,02 |/r) , {n < 0,7) . . (40a) 



ill which n — /i is determined by the eqiialion of state (37). Equation 

 (40") may serve among others to determine the de()endence of \\vi 

 reduced liquid volume on the temperature at low temperatures. 



17. Calculation of the b-vahies from the isotlieriiis of Argon. 



In order to be able to draw up the reduced equation of state of 

 Arg'on, we must in the first place accurately know the critical data. 

 For the critical dcMisity Qk I took the value 0,53078 from Coinm. 

 Leiden J 31 (Mathias, Kamerlingh Onnes and Crommklin). Abbreviated 

 therefore 0,531. In this it is assumed that the straight diameter remains 

 straight up to the critical point. The values of Crommelin in Comm. 

 115 (r.;r. = 0,509) and Comm. 118' (0^. = 0,496) are both too low. 



For T]c has been taken — 122°,44C = 150,65 absolute, and for 

 />A- the value 47,996, shortened to 48,0 — both from Comm. 115. 



For .s" we assumed the value 6-=3,424 from Comm. 131. In Comm. 

 120a (Kamerlingh Onnes and Crommelin) a too low value, viz. 3,283, 

 lias been given (in connection with the too slight critical density). 



At last the value of/ We derive from Comm. 120'' ƒ > 2,577 X 

 X 2,3026, hence ƒ ^ 5,933. (Comm. 115 gives the too low value 

 5,712). From 5= 8/': (8 + ƒ') — see 1, formula (7)— would follow 

 ƒ =5,986. And from ƒ =r 8y — see I, formnla (17) — follows with 

 7 = 0,7446 the value ƒ = 5,957. Now /• = /(l-|-r/) — see I, 

 formula (5) — hence, as (f is small positi\e, /' sliglitly greater than 

 /''. We may therefore safely conclude to the value 6,00 for f from 

 the two values 5,99 and 5,96 for /', which also fulfils the condition 

 ƒ > 5,93. ^^ 



Comm. 13J gives 0,0026235 Tk -. Qk as reduced coefficient of 

 direction for the straight diameter, giving with the above given 

 values of Tk and q^ the value y ^ 0,7446. We saw just now that 

 this value yields a good value for f'. From .v = 87 : (1 -|- 7) would 

 follow 7 = 0,748 for 7. The former value from Comm. 120a, viz. 

 0,003050 7^.:()^• = 0,9027, is much too high, and would be quite in 

 contradiction with our temperature-relation 27 — 1 =: 0,038 j/J', 

 which yields 0,738, in good harmony with 0,745, but not in harmony 

 with 0,903, which high value of 7 would belong to substances of 

 the Isopentane type with a critical temperature of about 450 absolute, 

 i.e. three times as high as that of Argon. 



We see from this how useful the above table in § 15, in con- 



