Properties of the Feldspars. 117 



solid phase always reappears upon reproducing given condi- 

 tions of temperature and concentration. On the contrary, as 

 Hautefenille describes the experiment, the components of the 

 albite remain as independent solid phases, which are then 

 assembled in some manner through the intermediary action of 

 the melted tungstate. 



Notwithstanding the fact that our interest was confined for 

 the moment to the mere production of a small quantity of 

 chemically pure crystalline albite, we ventured to proceed 

 along the lines of Hautefeuille's unsuccessful trial. We first 

 prepared a chemically pure albite glass, i. e., we melted the 

 components into a homogeneous mass before adding tungstate. 

 This glass was then finely powdered, thoroughly mixed with 

 an excess of powdered sodium tungstate and maintained con- 

 tinuously for 8 days at 1100°. Upon removing from the 

 furnace at the close of the heating, both albite and tungstate 

 were found to have been completely melted and to have 

 separated into two distinct layers according to their specific 

 gravities, the albite glass being above, and showing no trace of 

 crystallization. A second charge was then prepared with only 

 50 per cent of the tungstate, powdered and mechanically mixed 

 as before, and maintained at a temperature of 900° for IT days. 

 This time we were successful. After the sodium tungstate 

 had been dissolved away with water, the albite appeared as a 

 powder of about the fineness to which it had originally been 

 pulverized, except that the fragments were now crystalline 

 and apparently homogeneous albite. In thin section, under 

 the microscope, to our considerable surprise, it appeared that 

 the original glass fragments were unchanged in form. The 

 bounding surfaces were all conchoidal fractures, as they came 

 from the hammer, and evidently had not been in solution with 

 the tungstate at all. Its optical properties showed it to be 

 undoubted albite and the specific gravity was 2*620. 



The preparation of albite which we had synthesized by heat- 

 ing with an equal weight of sodium tungstate was first purified 

 by thorough washing with warm water, but this was not suffi- 

 cient to remove all the tungstate. A determination of tung- 

 stic acid showed # 62 per cent still present, which is equiva- 

 lent to 0*78 per cent of sodium tungstate. After removing the 

 water by heating carefully to a dull redness, the product was 

 submitted to a microscopic examination, which showed it to be 

 entirely crystalline and apparently homogeneous. Determina- 

 tions of the specific gravity gave 2-620 (see table, p. 128). If 

 this is corrected for 0*78 per cent of sodium tungstate of spe- 

 cific gravity 4*2, we obtain 2-607. 



A portion of this preparation was then purified further by 

 fusing for a few minutes with acid sodium sulphate (Haute- 



