223 



and to, =r |1 1 Ij, about equally broad, giving sharp reflexes; .? = MOlj, 

 broad and well reflecting, but as all faces of the ortliodiagonal-zone, 

 often showing oscillating angles; r = jl()l|, extremely narrow and 

 dull; rf=:|100j, hardly observable, in most cases totally absent; 

 ^ = {021|, very naiTOw and dull. The external habit is that of 

 hemimorphic thin plates parallel to |0()1|, with a slight elongation 

 in the direction of the />-axis. 



No distinct cleavage could be found. 



Angular Values -. 



6' : tü, = (OTO) : (111) = 

 C : CO, = (001): (Illj = 

 C: (;, = (001): (111) = 

 c: a = (OOlj : (10 0) = 

 C : s =(001): (r01) = 

 O,:co\ = (lll): (111) = 

 S : CO, = (101): (111) = 

 q: c =(012): (0 01) = 

 b': O', = (010): (111) = 



On |001| the directions of extinction are orientated parallel to 

 and normal to the orthodiagonal. The crystals are not appreciably 

 dichroitic; their birefringence is feeble. The optical axial plane is 

 |010|, with a feeble, inclined dispersion; one axis emerges on jOOlj 

 at the border of the field. 



The crystal-form of the corresponding dextrogyratory antipode is 

 reproduced in fig. 4. 



The specific gravity of the crystals 



1 so 



was at 18° C. found to be : d\t =2,31 7; 

 the molecular volume is therefore: 

 238,76, and the topical parameters 

 become: /: ip: to = 6,1471 : 5,7790: 

 : 6,7423. Analysis proved that the 



salt contains l^ H^O; on heating at 120° C. it is decomposed, 



assuming a brown colour. 



If the specific gravity of the racemic compound be also taken 



into account, (c/fso -^ 2,251; F= 257,80), it appears, in comparing 

 it with the con-esponding potassium-rhodium-oxalate^), that the sub- 



Fig. 4. Dextrogyratory 

 Potassium-RJiodium-Malonaie. 



M The topical parameters of the racemic malonate, after interchange of the 

 a- and c-axis, becomes: ^ : i|j ; w = 6,2484: 5.7947: 7,1329. 



