752 



273,09 + 286,55 = 559,64, pk = 44,62 atm., a = 0,9732. (The 



27 f y \ 

 value of A follows from our formula ^. = 7; — — r — ~t > i" which 



7 = 0,933 was taken). On account of this the values of RT at 

 t = 6° C. up to 65° C. (this last inclusive), viz. 1,0184, 1,0550, 

 1,0916, 1,1282, 1,1648, 1,2015, 1,2381, were resp. diminished by 

 13. 20, 32, 48, 68, 99, and 142 units of the last decimal. As it con- 

 ceins only a slight correction, the values of />^• and Uk were taken 

 for h and <(. The value of r, in the correction term was calculated 



from i\ = — =: '- X -r (96,04 is the molecular weight of 



' (l\_ 22412 d, ^ 



Cg H5 F), while for ^/, the values of the vapour density interpolated 



from Young's table (calculated at these low temperatures by Young 



on the supposition that Boyle's law still holds) were substituted. 



For the temperatures from 75° C, the values of p (reduced to 



atm.) and (/, measured directly by Y^'oung, were used. At 75°, 85°, 



and 95° the values of p : d\ were obtained by taking every time 



the middle value of the corresponding quotients at 70° and 80°, 



80° and 90° 90° and 100°. 



P 

 The values of a might be calculated from Jt X -r-^' by expres- 



sing also d^ in normal units; i.e. all the values from 14,07 to 9,52 

 (inclusive) must for this purpose still be multiplied by 96,04 -. 22412 

 = 0,004285. We have, however, not done so, and determined the 

 limiting value of jr X p ■■ d^d', for T = Tk from ak- Then ak is 

 namely = 0,0408 (see above), hence the limiting value in question 

 is = 0,0408 : 0,004285 = 9,52. 



According to van der Waals's expression the values of a must 



be proportional to 2 — j X^ — . That this is not accurately fulfilled 



appears e. g. from the following calculation for two arbitrary tem- 

 peratures. At 5°C. (4 : f/i = 0,3403, hence 2 — 1/(^4 : c/J = 1,4166. 

 For 130° C. is c4 : f/, = 0,4019, 2 — l/= 1,3660. Hence the ratio is 

 = 1,037, while the corresponding ratio of the values of a, viz. 

 14,07:12,93. has the value 1,088. On the assumption of simple 

 proportionality with \/^d^ we find the same value 13,8 at the two 

 temperatures for the "quotient" given in the above table. The last 

 assumption has, moreo\'er, the great advantage that the critical tem- 

 perature does not appear there, as it does with van der Waals, as 

 a very special temperature. The product ajeV-^Vk can, namely, bé 

 considered as a simple factor of proportionality, whereas van der 

 Waals's v^ cannot be eliminated in the relation between a and v. 



