Readily cleavable along 0. On m and p right-angled little etch- 
figures are visible in cassia-oil, which correspond with the indicated 
symmetry. In the vertical zone the direction of the optical elasticity 
axis is orientated on all the planes. Anaxial image was not observed. 
The specifie gravity of the needles as determined by means of a 
solution of mercuric-potassium-iodide was 1,721 at 14°. The equi- 
valent-volume is therefore 111.56 and the topical axes become; 
y:W:w — 5,5190 : 85272 : 2,3706.. 
b. 1-3-Dichloro-2-Nitro-Benzene. 
CAH Cla Cig(NOs 
(1) (3) (2) 
Fig. 2a 
1-3-Dichloro-2-Nitro-Benzene. 
’ 
melting point: 71° C. 
The compound ery- 
stallises from carbon 
disulphide in large, 
colourless, thin plates 
of parallelogram shape 
or also in smaller thick 
crystals as shown in 
figs. 2a and 25. The 
crystals are often 
opaque and difficult 
to measure ; sometimes, how- 
ever, they are more lustrous 
and very clear. 
Monoclino-prismatic. 
a:b :c=0,6696 : 1 :0,4149. 
p= STROE 
Forms observed : a =}1L00} 
generally strongly predomi- 
nating and always sharply 
reflecting; g = {011}, lustrous and either quite as narrow as o or 
else the broadest developed of all, so that the crystals appear short- 
prismatie towards the clino-axis; 0 = {111}, generally small, mostly 
streaked parallel with a:o and reflecting rather dullisly ; 6 = {010}, 
very small and often only present in a rudimentary form. 
Measured : Calculated : 
a:o = (100): (441) =* 58°44’ — 
gag (OLO — 
arg OO OIS ES Ae — 
ong (OLD =S 127 55 128°25/ 
Oni — (ela) Or) — PAS Ae 
a= b= (100) (010) = 90 0 
o:0=(111): (111) = 38 38 (about) 38 16 
