( 32 ) 



Measured : Calculated : 



q:q= (Oil) : (Oil) =* 63°43V; — 



0:0 =(111): (111) =* 47 52 — 



0:q={lll): (Oil) =* 74 207, — 



0:q =:: (111) : (01 1) = 45 427, 45°42' 



^:^* =(0.11): (010)= 58 87, 58 87, 



b:o =(0J0):(111)= 66 6 66 4 



No distinct plane of cleavage is present. An optical investigation 

 was quite impossible owing to the opaqueness of the crystals. 



Sp. Gr. =2,211 at 8° C; the eqniv. vol.: 127,09. 

 Topic parameters : x : V' : to = 4,0397 : 7,1147 : 4,4516. 



E. Nitro-3-5-Dibroniobenzene. 



Structure: C^Hj (NOj(i) . Br^s; . Br(5); m.p. : 104°,5. The compound 

 has already been measured by Bodkwig (Zeitschr. f. Kryst. 1. 590); 

 my measurements quite agree with his. 



Monodino-prismatic. 



BoDEWiG finds «:/^:c = 0,5795:l: 0,2839, with ,^=56°12'. Forms: 

 |110|, llOOj, |001| and jOJlj. 



I take ^ := 85°26' and after exchanging the a-, and c-axis 



a : 6 : c = 0,5678 : 1 : 0,4831, 



with the forms |011|, |001|, |201| and |211!. Completely cleavable 

 towards |201|. -Strong, negative double refraction. 



Sp. Gr. =2,363 at 8° C; equiv. vol. =118,91. 

 Topic axes: -/ : if. : to = 4,3018 : 7,5761 : 3,660J. 



The great analogy in the relation a:b of this and of the previous 

 substance is remarkable ; also that of the value of angle /?. 



P. Nitro-3-4-Dibromo-Beiizene. 



Structure CgHg (NO,) i; . Br 3) . Br^4: ; m-i). 58^ C. Has been measured 

 by Groth and Bodewig (Berl. Ber. 7.1563). MonocUno-prismatic. 



rt: 6 = 0,5773:1 with i?=78°31'. Forms |001|, |T10| and |100|, 

 tabular crystals. Completely cleavable towards |100|, distinctly so 

 towards |010|. The optical axial plane is |010| ; on a both optical 

 axes (80°) are visible. I found the sp. gr. at 8^ C. to be 2,354. The 

 equivalent volume is therefore 119,34. 



