875 



Fig. 8. Lilhiumorthosilicate. (Enlargem. 

 50 times; in immersion-liquid). 



§ 11. Tlie analysis of our 

 product tlms obtained, <;ave 

 5(),87„ SiO, and 49;27„ Li,0, 

 while one calculates : 50,237o 

 SIO, and 49,777o Li.O. So there 

 was an excess of 0,577o Si(K„ 

 causing the small eutectic heat- 

 efTect at 1020*=* 0. on the heating- 

 curve. The nieltingpoint of this 

 sul)stance, measured four times 

 with the element S^, was found 

 successive!}" (without correction) 

 to be : 12463 M.V. ; 12408 M.V.; 

 12399 M.V.; 12373 M.V. 



The nieltingpoint is thus con- 

 tinually lowered, which is caused 

 by the fact, that more and more Li^O evaporates, and some Li^O, 

 is generated at the same time. On cooling, retardation of the crys- 

 tallization was observed to about 12280 M. V., depending upon the 

 speed of cooling ; then, a sudden rise of temperature, caused by the 

 solidification of the mass was observed to 12320 M. V. 



To find the true nieltingpoint, we started therefore with mixtures, 

 which had a slight excess of Lt\0 ; the experiment showed, tliat 

 already after one single determination, a loss of 0,4 Li^O could be 

 [)roved, while a eutectic effect at 9775 M.V. became noticeable. 

 Finally some heatingcurves were obtained, showing no eutectic elfect ; 

 the crystallized product gave, on analysing, 50,0" /„ LiO,. With 

 thermoelement II the nieltingpoint was now 12590 M.V. (corr.), 

 corresponding with 1255°, 5 0. ± 3°. 



By means of the method of the "hollow thermoelement" (vid. § 12), 

 we determined the nieltingpoint to be: 1256° C; as to the fact, that 

 this temperature could eventually rather correspond to a three-phase- 

 equilibrium, cf. § 12 and §13 /. 



The refractive indices of the scale-shaped crystals weie measured 

 by means of the immersion-method, and found to be ;z£) = 1,614+0,003 

 and nz) = 1,594 + 0,003. The birefringence therefore was fairly 

 strong: about 0,020, perhaps somewhat less than for the metasilicate; 

 the same albite-like twinning as with the lilac crystals was also 

 observed, in this colourless product. 



The finely divided powder of the orthosilicate, like that of IMHI, 

 stimulates intensively to sneezing. 



