240 



The spodumene LiAISiJJ, is a moiioclinic* lithimiipyroxeiie. The 

 mineral is found in several places, in t lie form of colourless or feebly 

 tinged, glassv crystals of prismatic habitus, or in the form of opaque, 

 cryptocrystalline^aggregations. The transparent or coloured varieties, 

 which are strongly dichroitic, are used as a beloved precious stone ; 

 they are called: triphane, hunzlte, hiddenlte, etc. Their properties are 

 mentioned further on. 



^ 2. As was already pointed out, in a previous paper ^) on 

 lithiumsilicates, the synthesis of the pure compounds offered severe 

 difticulties, caused by the volatilibility of (he lithiumoxide at highei" 

 temperatures. The composition of the mixture is thus altered during 

 the synthesis, and the quantities of all three components must there- 

 fore afterwards be corrected, after being accurately determined by long 

 and troublesome analysis. A relatively small loss of the lithiumoxide, 

 is of considerable influence on the meltingpoint and other properties 

 of the investigated compound, because of the very small molecular 

 weight of the oxide. The analysis offered many difficulties: for 

 'notwithstanding all care and all arrangemenls ^), it often happens, 

 that some ^446^3 is found in the silica, and some SiO^ in alumina, 

 so that afterwards a controlling determination of these admixtures 

 must be made, w^hich takes a lot of time. The suiall amount 

 of Li^O is furthermore hardly determinable under the colossal excess 

 of N'a^O in the liquid; therefore, being determined as the difference 

 of 1007o with the sum of the percentages for SiO, and AlJJ^, all 

 mistakes atid inaccuracies of those determinations are summed up in 

 the number for Li,0, so that the correction of the preparation after- 

 w^ards, often depending on very slight differences in the amount of 

 Li^O, is a hazardous and not very amusing task. So it takes much 

 time to obtain products, which will not differ appreciably in their 

 constants and properties from those to be expected for the true pure 

 compounds, the criterium being given by the perfect identity of the 

 products, prepared in several ways. 



§ 3. Synthesis and Properties of the Pseudo-Eucri/ptite . 



The materials for this and other syntheses w^ere the same, 

 whose purity was before tested and described; the alumina used 

 was also provided by Baker and Adamson. It was necessary to heat it for 

 a long time in a platinum dish on the blaze, and often to stir the 

 powder with a platinum-wire, to allow the watervapour and the nitrous 

 gases, which the preparation evolved, to escape completely. The 



1) F. M. Jaeger and H. S. Klooster, these Proceedings p. 900, Febr. (1914). 



