494 



2y> so that y has the high vahie 2,11- [For "ordinary" substances 

 wiih critical temperature of about 400° to 625° absolute (125 to 

 350° 0.) we find for this the value 0,9 a 1]. For all other elements 

 of the carbon group we shall find values for 2/, lying between 4 

 and 3. 



Hence we find : 



4,22 V 12 50,6 



D = -—- = ■= 2,26. (calculated) 



1«'0. 10-5 ^^ 22412 22.4 - — ^ ^ 



For graphite (at high temperatures all carbon forms are converted 

 to graphite, and this is therefore the only stable form at 7\) D = 2,10 

 to 2,25 at ordinary temperatures, according to different statements. 

 Thus among others Moissan gives from 2,10 to 2.25, Meyer from 

 2,14 to 2,25; LE Chatei.ier has found 2,255 for artificial Acheson- 

 graphite. The value for the limiting density D^, calcubited, by us is 

 therefore in excellent harmony with the experimental value at the 

 ordinary temperature, which will be only very little lower. 



The value of pu is now found from 



1 «A: 



^^ ~ 27 • ^ ^ 



in which / = 0,781 (see above). Hence with Vak='è2.\0'^, 



64 = 10.10-*: 



1024.10-* 

 PU = 0,0289 X ^Q^ ^Q_3 = 2970 atm. 



From the formula 



'°^"£='^='"(f:-0 



follows at Ts ^ 4200° (7s is properly speaking the boiling point, 

 but probably represents the sublimation point at 1 atm. here) and 



Ps = 1 •• 



/6470 

 = f.'' - 



3,473=/,^» — - 1 



from which follows /V = 3,473 : 0,540 = 6,43, i.e. ƒ, = 6,43 X 

 X 2,303 = 14,8. This ^ alue is \Q\'y well possible, as according to 

 one of our formulae (see "New Relations" I) f]^ = 8y, when a 

 and b at Tjc are independent of T, so that fk would be = 16,9. 

 And fs is always somewhat smaller than fk. 



If 'Tjc is really = 6470° abs., Tk : Ts would be =1^ for carbon. 



3. Süicium. If we assume here I'^ajt = 34 . 10-^, we get with 

 A ^0,816 (2y = 3,81, see below) and èjt = 155 . 10-^ = 15,5 .10-*: 



