268 



We then made simiiar experiments with /?-spodnmene (of Maine) 

 ill a mixlure of 20"/^^ MoO^ and 807o sodiummoljbdate at tempe- 

 ratiireis helow G5()° C. ; on heating during 122 hours on temperatures 

 between 595° and 605° C, we obtained birefringent aggregates of 

 fehy needles of the /3-modification, with often rectangular borders. 

 The refractive index was 1,527, and while the aggregates of needles 

 did not extinguish in any position between crossed nicols, the rectan- 

 gular needles often showed a normally orientated extinction. As in 

 the former case, the product had also a pale lilac hue. 



Then we made the same experiment with «-spodumene (of /^mc6>?z); 

 it was heated during 88 hours in the same mixtures at 595° to 

 605° 0. The small pieces of the «-form had got opaque and were 

 converted at their borders or totally into the /J-modification ; the 

 refractive index was 1,519. 



More experiments were made, which all taught us, that from 

 molten magmas, cooled under manifold varied circumstances, never 

 was another thing produced, than either spodumene-"glass", or 

 /?-spoduniene; however we did not succeed in getting the «-form 

 from dry magmas even a single time. As devitrilication of spodumene- 

 glass appears also never to give another phase than /?-spodumene, 

 — we are of opinion, that it may be considered as sufficiently 

 proved, (hat the /^-modification is the only stable modification below 

 the melting point. The spodiimenes of nature therefore certainhj 

 Q-A.miot be produced from dry magmas; they represent metastable 

 forms of the compound, which are very probably generated from 

 circulating solutions, that is by so-called "hydrothermal" synthesis; 

 the natural forms of the compound only appear to be preserved 

 by the enormously retarding factors, which prohibited the transfor- 

 mation into the more stable ^l-'-form. Experiments are going on, with 

 a purpose to produce the ^'-modification of the silicate by such 

 hydrothermal synthesis. The results of these experiments will be 

 discussed in a following paper. 



§ 19. Finally we can here give some data, concerning the lithi- 

 uinahiniinate : LiAlO^. Tiiis compound was prepared by heating in 

 platinum crucibles the weighed, finely ground and well mixed com- 

 ponents, — lithiumcarbonate being taken instead of Li^O, — in 

 our resistance furnaces once at 900° C, then at 1200° C. After the 

 resulting mass had been pulverized, the heating was repeated and 

 these manipulations repeated four times. Analysis of the beautifully 

 crystallized, homogeneous mass gave the following numbers; 



