546 



bv lis in four difFerent ways, jnst to get information on the. final 

 identity of sncli preparations: 



a. By melting together calcnlated qnantities of Li.-^CO^, AlJ^^and 

 SiO^, repeating this manipnlation a few times, after thoroughly 

 grinding and sieving the crystallized masses. Analysis and correction 

 were made as usual. 



b. By starting from pure Li^SiO^, ^K^K '^"d SiO^. 



c. From LiAlSiO^ and SIO^. 



d. From LiAlO^, the lithiumaluminate, and SiO^. 



The four preparations, thus obtained, were used only for the 

 definitive measurements after it had been proved by repeated ana- 

 lysis and correction, that their composition did correspond, within 

 the limits of error, with that of the formula. All these experiments 

 were made in electrically heated furnaces with oxidizing atmosphere; 

 the preparation of these substances took a long time, because of 

 the volatibility of the Li J), and the fact, that only small devia- 

 tions in the content of Li J) showed themselves of appreciable 

 infiuence on the meltingpoint and properties of the compound. 



§ 9. The purest preparation we got, w^as obtained from synthe- 

 tical eucryptite by admixture oï SiO.. Analysis gave the following data: 



I. II. Calculated : 



SiO, 64,39 7„ 64,43 7„ 64,6 7„ 

 AhO, 27,56 7„ 27,66 7« 27,4 7„ 

 Li,0 8,05 7„ 7,91 7„ 8,0 7„ 



The mass was kept dui-ing a longer time at a high temperature, 

 to allow it to crystallize totally. Then the meltingpoint was deter- 

 mined in the usual way, by means of thermoelement ///; we found : 



14 353 .17. V. 



14 341 .1/. r. 



Mean: J 4 347 J/. V. (without correction), 

 if the rate of healing was about 65 M.V. pro uiinule. As the correction 

 for the thermoelement was — 12 M.V. at this temperature, the 

 meltingtemperature is 1400° C, in terms of the nilrogenthermometer. 

 As a check the mellingpoint was now again determined by the 

 statical method : very small quantities, wrapped in platinum folium 

 were heated during a considerable time (from lialf an hour to one full 

 hour) at a certain and accurately constant temperature, and then, 

 after suddenly chilling ^) in cold mercury, investigated by means of 



1) F. M. Jaeger, Eine Anleitung xur Ausfiihrung exakter physiko-chemischer 

 Messungen bei höhereu Tempeiatuien. Groningen, 1913, Seite 73, 74. 



