RECENT ADVANCES IN SCIENCE 401 



of inhomogeneous liquids, where the inhomogeneity arises from 

 the contiguity of solid crystals, from admixture and from 

 alterations in structure. 



Gaubert (Compt. Rend. 163, 392-4, 191 6) has obtained 

 anisotropic liquids by the evaporation of solutions of anisal-p- 

 amidoazotoluene in ether, chloroform, benzene, etc., and finds 

 that the forms obtained are not the same as those obtained by 

 the fusion of the pure solid. He has also determined (ibid. 164, 

 pp. 405-7, 191 7) the rotary power of some salts of cholesterol. 

 While the relation between the rotation-dispersion and the 

 absorptive properties is confirmed, the results regarding the 

 sign of the rotation are different from those obtained by Stumpf 

 (Physik. Zeit. 11, p. 780, 19 10). 



In a series of papers, Grandjean has confirmed and greatly 

 extended the observations made by Mauguin (Compt. Rend. 

 156, p. 1246, 191 3) with reference to the orientation of aniso- 

 tropic liquids on crystals. The former (Bull. Soc. franc. Min. 

 39, pp. 164-213, 1916) finds that when a drop of an anisotropic 

 liquid such as azoxyphenetole, azoxyanisol or anisaldazine, 

 is placed on a good cleavage surface of a mineral such as 

 blende, rock-salt, pyrophyllite and so forth, the orientation of 

 the anisotropic liquid often bears some simple relation to the 

 symmetry of the crystal. The three liquids named orientate 

 themselves so that the unique axis lies in some definite direction 

 parallel to the cleavage face, so long as the latter approxi- 

 mates to the so-called " perfect cleavage," that is, so long as 

 the crystal surface is a perfect plane. Other substances, how- 

 ever, have a tendency to orientate themselves so that the optic 

 axis is normal to the cleavage surface ; this may be due to 

 some disturbing influence such as minute particles of solid, 

 deformations in surface of liquid, etc. In the second paper 

 (Compt. Rend. 164, pp. 105-7, I 9 I 7) the variation in the orien- 

 tation of the optic axis is discussed and the conclusion is reached 

 that this variation is much greater than the variation in direc- 

 tion of the cleavage face and consequently than the deforma- 

 tion of the lattice of the crystal. In a third paper (ibid. 

 pp. 636-9) the orientation of salts of cholesterol and the oleates 

 on crystals is described. It is found that, in the case of the 

 positive liquid form of cholesteryl caprinate on the cubic 

 cleavage (100) of rock-salt, the optic axis is parallel to the 

 diagonals of the cube face and that, on the cleavage of zinc- 



