Ui 



heating was cheeked when the weiglit of the disl» renicained eonstant 

 after repeated liealings. Analysis then sliowed, that an ahnost pure 

 Al^O^ (100',,) was preseni ; even no ap[)recial)le trace of iron could 

 be demonstrated with the nsnal reagents. 



To point out the change of composition, taking place on heating 

 mixtures of known composition during the melting of the mass, the 

 numbers here following can serve very well: a mixture of 6,23 gram 

 Li^CO,, 8,61 gram A/.,C\ and 10,16 gram SiO^, was melted in 

 a closed platinum crucible iu the KLETCHER-furnace at 1500^ C. 

 After crystallisation, the mass was tlnely ground and sieved, melted 

 again, and this process repeated three times. Instead of the expected 

 composition /, the composition Jl was found by analysis to be : 



/ // 



SiC\ 47,7% 48,6 7o 



AU\ 40,4 7o 40,9 7„ 



LU) 11,9 7, 10,5 7„ 



As there was thus 1,5 7fl Li.^0 too little, 0,055 gram AL/J^ 

 and 0,718 gram dry Li^CO^ were added to 18,92 gram of the 

 resulting product, and this mixture was then heated four times in 

 platinum crucibles, by means of small resistance-furnaces, at 900° or 

 1000'^ C, the mass being linely ground and sieved after every 

 melting. Then the preparation was a^aiu heated once at 1450° C. 

 in a resistance-furnace. Analysis gave : 



Unserved : Calculated : 



SiO, 47,9 »/„ 47,7 7„ 



AU), 40,1 \ 40,4 7„ 



LLO 12,0 7„ 11,9 7« 



The deviation from the exact composition is so slight, that this 

 preparation could safely be used for the study of the properties of 

 the compound. 



§ 4. The meltingpoint of this preparation was determined several 

 times by means of a calibiated thermoelement (N°. Ill) The mean 

 value of all readings was 14200 M.V. ± 2 M.Y. ; as the correction 

 of this element with respect to tiie standardelement, which was 

 standardized by means of Sosman's element G, was — J 2 M.Y. ; 

 the meltingpoint of the substance, in terms of the Washington nitro- 

 gengasthermometerscale, can be tixed at 1388° C 



The heat-effect on melting is only small ; as a result of that, on 

 cooling down the molteu mass, one finds a retardation of its crystal- 

 lisation up to about 12840 M. V. ; then crystallisation takes place 

 while the temperature increases only to 1306"^ C. The point of 



