348 
faces, making the measurements rather difficult. From ethylacetate 
we obtained occasionally also great, hexagonally bounded, tabular 
individuals. The most exact measurements were made with very 
small, almost colourless crystals, showing very constant angular values. 
Although they belong, according to their optical properties, to the 
monoclinic system, their angle 8, however, does not differ from 90°. 
Monoclinic-prismatic ; pseudo-rhombic. 
dere = 1,2289 esa he 11812. 
p== 900. 
Forms Observed: gq = {012}, predominant and yielding perfect 
reflexes; r= {101}, large and strongly reflecting ; m = {110}, smaller, 
but well developed and lustrous; 6 = {010}, narrow and dull, often 
absent; o = {212}, well developed and lustrous; a= {100}, very 
small and dull, but at least measurable; finally an extremely small 
pyramid a = {711} (2) was observed, which, however, was mostly 
absent and very badly reflecting. The aspect of the crystals is thick- 
prismatic parallel to g, with elongation in the direction of the a-axis; 
however, the crystals are often most irregularly distorted. Ordinarily 
r is present only with a single face. 
Angular Values: Observed: Calculated: 
qa: F=—(012) (101) = DI ZE — 
m:q=(110):(012) =*. 66 46 — 
q:q¢=(012):(012)= 61 3 61° 8’ 
q: b= (012): (010) =" 59°29 59 26 
q: (012):(100)= “90 "0 90 0 
0:0 =(212):(212)= 46 42 46 8 
o:q=(212):(012)= 39 34% 39 37 
o:q=(212):(012) = 67 59 68 10 
m:o = (110) (212);=" 45 2 45 4 
O27 = (212) (101), 4 23-4 
m:q=(110):(011)= 66 50 66 46 
ax = (100 (Ten WS 48 19.3 
There is a distinct cleavage parallel to {010}. 
Although the angle 8 does not differ appreciably, the optical pro- 
perties prove, however, that the compound has monoclinic symmetry : 
on {012} the extinction-angle is about 23° with respect to the a-axis; 
in the same way the extinction-angle on {010} is about 42° with 
respect to the a-axis. The optical axial plane is probably parallel 
to {010}. 
