( 58(3 ) 



KoNV we rcliirii to llic ('\|K'i'iiii('iital \ ei-ififulioii of '"/.■. 



1 Gr. //.^ al 0^' ('. aiid J alm. occupying a space of 11127 cM\, 

 ('i is expressed in ccM\ (Mpial 1o 2o7i) X 1<> ^ X m*- -"' *'t'"^'^' ^'»^ 

 critical (h'ns'itij is: 



1 



di. — = 0,0848. 



28.70 



Accoi-diiig to the theorem of the straight diameter of Matiiias we have : 



wliich (|iiaiilit\ ^f has been foiuidliy N'oixc; and Matiiias to dilfei- little 



fi-om unity for dillercnt non-associating sid)stances. 



Dewak ^) found the density of the licjuid ])hase at the melting point 



of //, (nr,5) to he (l,().S(), so we lind, neglecting the density d^ of 



the vapour : 



0,080 16,5 ^ ^ 



— 2 = 1— ^ = 0.408, 



d], 31.0 



A\ liicli yields for di : 



0,086 



,], — _ — 0.0348. 



2.468 



in perfect agreement with the value of'//, we ha\e calcidaled above. 



We now proceed to the calculation of the other critical quantities 

 T,, p,, X and ): 



We lind for 7/: 



8 a 0,9549 X 1,0456 ^ _ 8 a ^ nnn ^* 



RTi. — X-^ ^-^— ^ = l.OKJ X -^ — = 0,299—, 



'^ 21 H 0.9883 21 hk bk 



With ^/ = 30(), /v;s.= ^->i^ ^vt' lind therefore 



0.0094 — ^ = 0.100. 

 273 



so 



Ti. = 27°.2. 



This value is somewhat too low: the experiment has yielded 



We find for the ci-iiical pressure: 



_ 1 ^ _0j> 439 X 1,093 X " - = 0,0387 ^. 



^'''21bi,^^ 0,9883 ' ^^27/./;^ ' b^' 



1) 1. c. bl. 477. Dewar finds Die melting point to be 10' a 17'; the critical 

 temperaluie lo be 30^ a 32° absolute teniperatuie. [The density of the liquid 

 ])hase at the boilingpoint (20° a 21°) has been estimated to be ± 0,07, but then 

 the vapour density may no more be neglected.] 



