263 



or 



T. 



IT. 



the symmetry of these molecules is a rather high one : in a compound 

 of formula /, there is a homopolar trigonal axis perpendicular to the 

 plane of the ring, three homopolar binary axes (including 60) in 

 the plane of the ring, and three vertical planes of symmetry passing 

 through the trigonal axis and bisecting the angle between two suc- 

 cessive binary axes; moreover, there is a symmetry-centre, and the 

 whole symmetry is that of class D%. In a molecule of formula // 

 there is a heteropolar senary axis perpendicular to the plane of 

 the ring, and six vertical planes of symmetry passing through it, 

 but there is no symmetry-centre, and the whole configuration has 

 the symmetry of the class C%. As both configurations have symme- 

 try-elements of the second order, there is, of course, no possibility 

 of resolving the optically inactive substance into active antipodes, 

 the arrangements being both congruent with their mirror-images. 

 The same would be true for inosites with configurations as: 



and 



in. 



where /// has the symmetry of class C^, and IV that of the class S, 

 both belonging to those figures, which are superposable with their 

 mirror-images. Inosites of this kind should, therefore, not be resolvable. 

 Such is the inactive, non-resolvable inosite: phaseomannite l ) which, 



!) G. Tanret, Compt. rend, de 1'Acad. d. Sc. Paris, 84, 393, (1877); 86,486, 

 (1878); Ann. de Chim. et Phys., (5). 23, 391, (1881); V. Von Zepharovitsch, 

 Sitz. Ber. d. Akad. d. Wiss. Wien, 58, (//), 121, (1868); A. Villiers, Compt. rend., 

 84, 393, (1877); G. Wyrouboff, Bull, de la Soc. Min., 25, 160, (1902); J. V. Lewis, 

 Proceed. Cryst. Soc. London, 2, 49, (1882); Ref.: Zeits. f. Kryst., 1, 406, (1877); 2, 



