144 



Tk = 1172° abs. (± 900° C.) ; pu = 180 atm. ; ch — ± 3,3 



^^. = 149.10-5 ; 1/^^. = 10,74. 10-2 . 2y = hk:b, = %4: ■ /\.= =b6,4 



7 a: 7; = 1,86 ; 7\. : r,,. = 5,0. 



These values are pretty certain ; the critical temperature lies 

 — taking the vapour pressure observations between 500° and 880° 

 into consideration — almost as much as 100° lower than 1 had 

 calculated in 1916, and only 20° higher than the highest temperature 

 at which Caili.ktet c.s. have carried out their vapour pressure 

 determinations. 



That it seems at lower temperatures that the critical temperature 

 of mercury lies much higher (as among others Königsbergek and 

 Bb:ndek supposed), is owing to this that the expansion of liquid 

 mercury is ahnormally small at those temperatures (0° — 300° C). 

 But this is to be attributed to still unknown disturbing circumstances 

 (association e.g.). As little as we may conclude to entirely faulty 

 critical values from the abnormal expansibility of water in the 

 neighbourhood of 4° C. (and still far above it), or of Helium (where 

 likewise a maximum density was observed), may we do so for 

 mercury. We shall come back to this later on. 



B. Phosphorus. 



1. From the vapour pressures of liquid phosphorus, found by 

 himself between 169° and 634° (These Proc. of Oct. 17, 1914 and 

 Jan. 18, 19J5; Z. f. ph. Cliem. 88 (1914), 91 (1916)), Smits extra- 

 polated the value 82,2 atm. for the critical pressure, on the assump- 

 tion of the value 695° C, found by Wahl for the critical tempera- 

 ture of Phosphorus. It is easy to see that this value is too loiv. If 

 from the vapour pressure formula 



log - = ƒ (^ — 1^ with Tjc = 695 4- 273,1 = 968,1 we, namely, 



calculate the values of /' at ten different temperatures, we find with 

 p]^ = SO, resp. 90 atra. : 



t = 169°,0 210°,0 252°,0 298°,6 355°,7 409°,3 1 504° 550° 593° 634° C. 



p= 0,04 0,20 0,54 1,38 3,88 (7,36) 23,2 33,0 44,2 58,6 atm. 



p^ ( 3,3010 2,6021 2,1707 1,7632 1,3143 1,0362 i 0,5376 0,3846 0,2577 0,1352 ) 



P ( 3,3522 2,6532 2,22185 1,8144 1,3654 1,0874 0,58875 o,4357 0,3088 0,1863 ) 



-A - I = 1,1898 1,0039 0,8437 0,6934 0,5396 0,4187 0,2458 0,1762 0,1178 0,0672 



/ = 



2,77 2,59 2,57 2,54 2,44 (2,47) 2,19 2,18 2,19 2,01 



2,82 2,64 2,63 2,62 2,53 (2,60) 2,40 2,47 2,62 2,77 



(min) 



