( 664 ) 
orientation of the elasticity-ellipsoid is therefore in the same order: 
y,8,@ in which «>> g> y. The double refraction is feeble. 
On {100} and {O01} orientated extinction ; on {010} the very small 
inclined angle of the elasticity axis with the vertical axis could not 
be sharply defined on account of the strong absorption; it is not 
distinguishable from 90°. 
The specific gravity of the crystals was found to be 1.240 at 15°; 
the equivalent volume is, therefore, 143.53 and the topical axes become: 
4: Ww = 4,2368 : 4,1623 : 8,1626. 
The complete isomorphy of p-Nitrodiethylaniline and p-Nitro- 
sodiethylaniline is therefore firmly established. The properties of both 
substances are given here by way of a comparison. 
p-Nitrodiethylaniline : p-Nitrosodiethylaniline : 
Monoclino-prismatie. _ Monoclino-prismatic. 
a:6:¢ =1,0342: 1 USS Deer te OM Sree 21,9611. 
yi: @ = 4,4276 :4,2807 :8,4710. | pip: @ = 4,2363 :4,1623 : 8.1626. 
di | d = 1,240 
y = 158,36 | v = 143,53 
Angular values : | Angular values: 
(110) : (100) = 45° 34’ (110) : (100) = 45° 254’ 
(100) : (402) = 51° 13’ (100) : (102) = 48° 174’ 
(100) : (001) = 80° 34’ (100) : (001) = 85° 43’ 
In ethyl-acetate + ligroine the In ethyl-acetate + ligroine the 
habitus is flattened towards {100} habitus is flattened towards {100} 
elongated towards the c-axis; some- and elongated towards the c-axis. 
times towards the D-axis. 
Very completely cleavable towards | Very completely cleavable towards 
{001}, fairly so towards {010}, with | {O01}, fairly so towards {010} with 
a conchoidal fracture. conchoidal fracture. 
On {001} violet reflexion. On {O01}, and on {O10}, {102} 
violet reflexion. 
Optical orientation : 7, By a. Optical orientation: y, 8, 4, 
Double refraction, positive. ~ Double refraction, positive. 
On {100 a but little-inclined On $100) a but little-inclined 
axial image with small axial angle; axial image with small axial image; 
axial plane parallel the /-axis for axial plane parallel the b-axis; 
the red, parallel the c-axis for the rhombic dispersion : 9 Sv. 
green rays; dispersion: @ << v. 
Colour : brownish-yellow. Colour: emerald green. 
Strongly pleochroic: blood red- Strongly pleochroic: violet-pale 
orange-yellow. ereen-bluishgreen. 
On ¢ absorptionbundles. |___On c absorptionbundles. 
i p 
