278 



H. L. Wheeler — Double Halides of 









Measured. 



Calculated 



m a r, 



1010 ^ 1011 



*35° 6' 





r a c, 



1011 a 0001 



54 43 



48° 18' 



r * z, 



1011 aOIII 



47 15 



48 18 



r a r, 



1011 aHOI 



89 50 



90 14 



s a s, 



18917 a 19817 



6 40 



6 21 



The basal cleavage was prominent and sections parallel to 

 this showed abnormal optical properties. Thin plates from 

 the crystals like fig. 4 showed middle and end sections with 



Fig. 4. 



Fig. 



extinctions in the directions indicated by the arrows. In con- 

 vergent light no interference figure was observed. This salt 

 then like 3RbBr . 2SbBr 3 and 3EbI. 2AsI 3 is only pseudo-hex- 

 agonal being abnormal in its optical properties. 



Rb CI . Sb Cl v —The crystalli- 



I 



£ 



Fig. 6. 



zation of this salt is monoclinic. 

 Crystals were obtained 10 mm 

 long. The forms observed 

 were 



a, 100, i-l m, 110, I e, 101, l-l 



c, 001, O d, 101, — l-l p, 111, 1 



The habit is shown in fig. 6. The axial ratio \&d:b:c 

 1-732 : 1*000 : 1-085 ; /3 = 001 * 100 - 65° 34'. 



a~c, 100 a 001 

 a*m, 100 a 110 

 ce, 001 a 101 

 m*m, 110 a 110 

 a'^e, 100 a 101 

 p a e, 111 a 101 

 p.,c, 111 a 001 

 CacZ, OOIaIOI 

 d*a, 101 a 100 



Measured. 



*65° 34' 



*57 37 



*37 36 



64 46 



76 54 



46 28 



• 56 50 



24 21 



41 24 



Calculated. 



64° 46' 

 76 50 

 46 23 

 56 52 

 24 22 

 41 12 



