'M2 



solidification therefore is found 80° or 90° below the true tempe- 

 rature of equilibrium: solid ^ liquid, although the velocity of crys- 

 tallisation can by no means be called very small. F'rom this fact 

 also the discrepancies in the data of different authors are to be explained : 

 1330° 0. (DiTTLER and Bat.ló), 1307° C. (Ginsberg), etc. In this case 

 also, the usual method of cooling appears to give no reliable results. 

 A remarkable fact is the relatively appreciable increa^fe of the 

 volume of the molten mass on crvstallisation ; it is immediately 

 observable by the deformation of the platinum-crucible, (fig. 1). That 



really this phenomenon is caused 



r~ J in this case by a volume-change like 



I 1 that of water into ice at the freezing- 



^^\ Jz^~^ point, and that it need not be explai- 

 ^, ^^ ]5 " ned in the manner mentioned in the 



Piq-j^^ case of the spodumene, can be demon- 



Increase of the volume of molten «Crated by tlie determination of the 

 Eucryptite on crystallisation. specific gravities of the crystallized 



mass, and of that of the beautiful, colourless "glass", obtained by 

 suddenly chilling the liquid. The expansion seems to be about 37o 

 of the original volume. 



§ 5. The crystallized substance, obtained by slowly cooling the 

 liquid, is opaque and greyish white. Microscopical investigation 

 showed it to be a cryptocrystalline aggregation of irregularly shaped, 

 grain-like crystals, which are so small, that even with an 800-times 

 enlargement, they can hardly be seen ; they possess a very weak 

 birefringence. Greater pieces seem to be built up between crossed 

 nicols by innumerable lighting points ; such aggregations always show 

 an undulatory extinction. In no case crystals with determinable 

 borders were found. As a "mean" refractive-index the value : 

 ;?u =: 1,531 ± 0,002 was obtained. 



The specific gravity at 13°,6 C. was pycnometrically found to be : 

 f/40= 2,365, and at 25°,1 C : r/40= 2,362 ; we used orthochlorotolaene 

 (1,0825 at 25°,1 C.) as immersion-liquid. 



As follows clearly from those values for the refraction of light 

 and for the specific gravity, the natural eucryptite must be another 

 modification of the compound LiAlSiO^ ; therefore we will distinguish 

 the artificial silicate 1)y the name : pseudo-eucryptite. M. 



1) Ginsberg (Zeits. f. anorg. Ghem. 73. 291 (1911)) describes his preparation in 

 the following manner : completely isotropous, uniaxial negative in convergent pola- 

 rised light, with a birefringence smaller than that of nepheline. Weyberg asserts 

 to have obtaineil an "eucryptite" of rhombic symmetry, by the reaction oiLuSO^, 

 on kaoline in solution. Gf. also the experiments of Thugutt, Zeits. f. anorg. Ghemie 

 2. U6. (1892). 



