415 



Mesitylene. 



dn 

 Temperature-interval: 



dt 



between — 20o,8 and 0^ 

 O „ 75 



75 „ 110 



110 „ 150 



Triphenylmethane. 

 between 138° 4 and 156^ 

 156 „ 171 

 171 „ 194 

 194 „ 212 



Bromobenzene. 



between — 17,°5 and +125,''5 

 125,5 „ 153 



in Erg: 



2,40 

 2,20 

 2,06 

 1,97 



1.59 

 3.03 

 4.46 

 4.83 



2,38 

 2,53 



para-Fluorobromobenzen e. 



between —21° and 0° 2,41 



O „ 45 2,09 



45 „ 117 1.97 



117 „ 150 2,49 



between 



Pseudocumene. 

 Temperature- interval -. 



dn 

 df 



between —21° and 0^ 

 O „ 26 

 26 „ 146 

 146 „ 166 



between 



Chlorobenzene. 

 -16° and |-25^ 

 25 „ 50 

 50 „ 122 



in Erg: 



1,60 

 2,00 

 2,18 

 3,0 



2,20 

 2,42 

 2,60 



between 



meta-Dichlorobensene. 



-22° and 0° 2,79 



O „ 25 2,23 



25 „ 91 2,11 



91 „ 117 1,88 



117 „ 136 1,64 



136 „ 160 1,51 



meta-Fluorotoluene. 



between —71° and — 20°5 2,85 



—20,5 „ O 2,49 



O „ 25,4 2,38 



25,4 „ 45,3 1,99 



45,3 „ 84,9 1,85 



Especially the last mentioned foiu- cases prove once more verj 



strikingly the fact, that -- cannot be considered as a constant, but 



ot 



tiiat it is itself a function of temperature: in most cases in such a 

 way, tiiat it will decrease with increasing temperature. With cliloro- 

 and hroinobenzene however evidently just the reverse happens. In the 

 same way benzene, toluene, p-vi/Iene and mesiii/Iene belong to the first 

 group of subst.inces, while the isomeric pseudocumene manifests on 



the contrary an increase of -r- with rising temperature. Ihc devia- 



tions of the linear decline are so great and in most cases so system- 

 atical, that they can by no means be accounted for by experimental 



ö/t 

 errors; the variability of ~- with the temperature must therelore 



ot 



be considered as an essential fact. 



Groninyen, June 1914. Laboratory of Inoryanic Cheniistry 



of the University. 



