501 



group of Titanium. Here data are still more greatly wanting, as we have 

 not even an idea of the probable values of hk through compounds of 

 which the critical temperature has been determined. We can, there- 

 fore, only assume them in approximation between those of the 

 elements of the principal group. Thus we might put: 



Ti Zr Ce Th 



bjc . 10^ -= 182,5 237,5 292,5 402,5 



y'ajc . 10'' = 35 37 39 4l' 



With respect to Titanium we find with 2y = 3,68, X = 0,827 : 

 66,92 X 1225 



'' = — iW--^^^^'" 



In consequence of this 2y = 1 + 0,04 X 67,0 becomes = 3,68. 

 We then calculate for D^ : 



3,68X48,1 177,0 



^" = 182,5.10-5x22412 = 4Ö;9Ö = ^- (^^^^^'l^^^^) 



At ordinary temperatures Weisz and Kaiser (1910) found 3,99 

 (amorph, 85,65 »/„, i.e. 3,2 Vo 0, + 11,15 % iron) and 5,17 (molten 

 97,47„). MoissAN(1895) and Meijer (1899) found 4,87 (molten 27^0). 

 At last Hunter found the value 4,50 (lOOV») in 1910. The real value 

 will, therefore, no doubt lie in every case between 4 and 5, so 

 that the value calculated by us is again in fairly good agreement. 



For the melting point Burgess and Waltenberg (1914) found 1795°, 

 Hunter (1910) from 1800° to 1850°. If we take the round value 

 1800° C. = 2073° abs., 7^ -. T,, becomes =247. We have finally 

 for pk : 



0,0306 X 1225.10-4 

 ^' = 333,06. 10-^^ = ^^^'^^"^- 



9. Zircon. Here we have with 2y = 3,51, A =0,841: 

 68,09 X 1369 

 ''' = 23.75 = 2!L» abs. 



From this follows 2y = 1 + 0,04 X 62,7 = 3^, so that for D, 

 we calculate: 



_ 3,51 X 90,6 317,6 



^» - 237,5.10-5x22412 = 52;^ == M! • (calculated) 



This is again in fairly good harmony with the experimentally 

 found value, viz. 5,95 to 6,39 (Wedekind and Lewis, 1910), and 

 6,40 (Weisz and Nkumann, 1910). The former two authors worked 

 resp. with powdery (96,5 7„) and molten Zircon (91,3 to 96,5 7,); 



