213 



§ 7. The crystals of (lie laevogyrate antipode ordinarily showed 

 only the bipyrainid l\ vvliicli mnst be considered as a /^/dianded 

 bipyramid here, l)ecause all phenomena are in agreement in this 

 case with Pasteur's law, as is proved beyond doubt by the hemihedral 

 symmetry of the crystals. Therefore to this bipyramid must be 

 attributed the symbol |2 1 1 2| [512]; besides the forms o, x, and 

 //, y having the symbol {1121} [4:12], appear subordinately here. 

 Because o and x were in most crystals about equally large, and 

 could not be discerned in any other way, the external habit of these 

 lefthanded crystals was not different from that of dextrogyrate salt, 

 the latter being brought into the same position as the lefthanded 

 by a rotation through 60° round the trigonal axis, with the oidy 

 difference, that the foims x and o are thereby interchanged. However, 

 if ,(• and are of unequal size, the occurrence of mirror-images 

 could be seen immediately in the crystals. The zonal relations may 

 be made cleai- by the subsequent stereographical [)rojections (Fig. 4). 

 Just as in the case of oppositely rotating rhodiuni-saMs, a non- 

 superposable hemihedrism accompanies here the contrary power 

 of rotation. 



Fig. 4. SteveographicaJ Projection of the Cri/stnl forms of d- and 

 I- Potassium- lridiHin-Ox(date (onli/ the top-ends of the cn/stals). 



§ 8. The 8|)ecilic gravities of the formerly investigated rhodioni- 

 salts, were determined at (/40 ^2,171 for the racemic compound 

 (4^ Hjj), corresponding to a molecular volume of: 260,34; and at 



(^/^o = 2,255 for each of the optically-active salts (-f- 1 Z/^^^), which 

 corresponds to a molecular volume of 222,70. From this the topical 

 axes of these salts are calculated at : 



