506 



And now we shall see in what follows that — at least for Na, 

 K, Rb and Cs — the real values of 7^- lie between those obtained 

 with the factors ÖV» and 1,7, and those obtained with the factors 

 47» and 1,5. Generally nearer to the tirst group. Besides we know 

 already from former considerations that the factor by which the 

 absolute boiling point temperature must be multiplied to obtain the 

 absolute critical temperature, lies in the neighbourhood of 1,7. This 

 factor can also be smaller, but it seldom becomes smaller than 1,5. 

 For Lithium there is reason to suppose that Tjc lies probably higher 

 than would follow from 7',,. X ^Vi- The factor is there with pretty 

 great certainty =r 5,6. 



It is certainly rather remarkable that the ratio Ts : Tt,. is so 

 constant for the alkali metals, viz. about SVs- 



2. Ltthium. The melting point lies at 1790° 0. =: 452, °1 abs. 

 According to the above we may expect the critical temperature 

 between 452,1x573 = 2411° and 452,1x5 = 2713° abs. We 

 shall perform the subjoined calculations for both values of T^, 

 rounded off to 2410° and 2700°. 



The value of y follows from our formula 2/ = 1 -|- 0,038 1/7^. 

 It gives with |/7'a: = 49,09 to 51,96 the values 2,865 and 2,975, 

 i.e. y = l,43 to 1,49. This is accordingly the (reduced) coefficient 

 of direction of the 'straight diameter between D^ and D^. 



27 r y \ ... y 



From formula X 



87-1 Vr+i 



with 



yti 



0,589 or 0,598, 



hence (-^j =0,347 or 0,358, and with 8y—l = 10,46 or 10,90 

 we further find the values .^ = 0,895 or 0,886 for the* factor A in 



«fc 



RTk = — ^ -r and pjc 



-7 bk 



27 bk' 



This renders o) ::= — X -. R with 

 27 



