( 661 ) 
Brownish-yellow crystals, short prismatic or somewhat extended 
towards the /axis and flattened towards {100} with a beautiful 
reddish-violet reflexion on {LOL}. 
Monoclino-prismatic. 
lo) Res AOR sil pallets 
B — 80°34’. 
The measurements are identical with those formerly given by 
me. The habitus of the erystals is, however, different from those 
previously obtained from alcohol (Fig. 2): ¢ and give ideal 
reflexes; a very good, but often somewhat curved; ¢ alone has a 
violet reflexion ; the reflex is coloured light-lilac. Etch-figures on {100! 
corresponded with the indicated symmetry. 
Very completely cleavable parallel {O01}; fairly so towards {010} 
with conchoidal fracture plane. 
Optical behaviour. The optical behaviour of the compound is very 
interesting. (Fig. 3). 
First of all the crystals are strongly pleoehroie ; on {001}, sulphur- 
yellow and blood red; the inflexion indicates the direction of the 
vibration of the polarised rays; on {O10} yellow and orange; on 
{100} yellow and orange-yellow. On {O01} are seen in convergent 
light two red absorption hyperboles like the opening arms of an 
axial cross. 
On {100} an eccentric axial image is visible, the axial angle is very 
small so that there is apparently present the image of a monaxial crystal 
with a crossing of the axial planes for red and green light. The axes for 
the red lie in a plane | b-axis, for the green in one | c-axis. The angle 
for the red rays is smaller than that of the green rays. The double 
refraction is positive; the first diagonal inclines to the normal 77 
the plane of symmetry ; on {100} there are, therefore, at the same 
time an inclined and a horizontal dispersion. 
The angle of inclination is somewhat larger than in the ease of 
the nitroso-derivative. 
2. p-Nitrosodiethylaniline. 
Some time ago') I made some preliminary communications on 
paranitrisodiethylaniline C,H,(NO) N(C,H,), melting point 82°,2. I 
(4) * (1) 
have since succeeded in obtaining this compound in a form more 
1) PF. M. Jarcer. Ueber morphotropische Beziehungen hei den in der Amino- 
Gruppe substituirten Nitro-Anilinen. Z. f. Kryst. 40 (1904) 112—146. 
