( 790 ) 



of the planes. Nevertheless the complete isomorphism with the chloro- 

 eompound may be clearly shown ; of course the differences are some- 

 what larger than in the case of isomorphoiis substitution products in 

 which one atom only is replaced by another and not three at the 

 same time, as is the case here. 



§ 2. ]n the following the crystalforms of the diverse substitu- 

 tionproducts are described. 



Tri-p-Jodotriphenylmethane. 



(C, H, J)3:0H; m. p. J32°C. 



This compound was kindly presented to me for investigation by 

 prof. 0. Fischer of Erlangen. 



From ligroïn it crystallises in small, 

 refractive, pale yellow needles which are 

 readily measurable. From benzene, howe- 

 ver, a double compound Q.OY\\Sih\m^ benzene 

 crystallises in large transparent prisms. 

 The chloi'O- and bromo-compounds, how- 

 ever, do not unite with benzene; from 

 the benzene solution the crystals of the 

 pure compounds are always deposited. 



A. Tri-jJ-Jodotinphenylmethane, from 

 ligroïn. 



The symmetry is rltombic-hipyramidal ; 

 the axial ratio is calculated as : 



a:h:c = 0,5765 : 1 : 0,8798. 



Evidently this substance is directly 

 isomorphous with the CI and the Br- 

 compound although here the differences 

 are again more considerable than usual 

 on account of the simultaneous substitu- 

 tion of three isomorphogeneous atoms. 

 Pio' 1. Forms observed : m = [110}, well deve- 



Tri-p-Jodotriphenylmethane. loped and lustrous ; a ^= |i00|, very nar- 

 row and dim; ^ = [Ollj, yielding good reflexes; p = |130|, very 

 narrow and dull. 



Angular values : Measured : 



m : m = (110) : (llO) = *59° 557,' 

 m: q = (IW) : (Oil) — 70^" 307,' 

 q: q = (Oil) : (Oil) = *82^ 41' 

 m: q = (110) : (130) zr= 30' 15' 

 Distinctly cleavable along m. 



'Ttv 



I 



Calculated 



70° 447,' 



30" 30' 



