Foote and Bradley-, — Solid Solution in Minerals. 27 



could be obtained so far as mechanical admixture was con- 

 cerned an analysis would show the oorrect formula of the 

 mineral. A sample of nephelite from Eikaholmen, Norway, 

 was chosen for analysis and freed from other minerals by use 

 of acetylene tetrabromide. The sample used in analysis floated 

 when the specific gravity of the liquid was 2"638 and sank 

 when it was lowered to 2 - 632, so that variation in the density 

 of the mineral was not more than "006. The resulting nephel- 

 ite contained a minute amount of albite which was insoluble 

 in hydrochloric acid, but the quantity was so small that it could 

 be neglected. The material obtained was, we believe, as pure 

 as it is possible to obtain nephelite by mechanical means, since 

 observations under the microscope showed the sample to be of 

 excellent quality and practically homogeneous. 



Two complete analyses and two other partial ones were 

 made on this material with the greatest care (by Bradley). 

 Only brief mention seems necessary of the methods employed 

 in the chemical analysis. Silica was determined in the usual 

 way, after dissolving the mineral in hydrochloric acid and by 

 testing its purity traces of alumina were recovered. Alumina 

 was precipitated as hydroxide and this was dissolved, repre- 

 cipitated and weighed in the usual manner. The small per- 

 centage of iron was determined volumetrically with potassium 

 permanganate. A Smith's fusion was made for the alkalies. 

 The results in detail with the ratios obtained are given below. 



Table I. 



= 2-23 

 •330 = 1-00 



•323 = 0-98 







Analy 

 T 



ses of Nephelite (Bradley). 





Nephelite from Eikaholmen 



, Norway 











1 



2 



3 



4 



Average 



Eatio 



SiO, 



44-59 



44-31 



44-37 



44-59 



44-46 



•736 



Ai a o 3 



3329 



33-02 



33-41 



32-71 



33-11 



•324 ) 

 •006 j 



*\o 3 



•96 



•96 



•96 



•96* 



•96 



K,0 



5-62 



5-62 







5-59 



5-61 



•060 ) 



Na 2 



16-59 



16-31 







18-06 



16-32 



•263 f 



H,0 



•38 



■3S* 







•38* 



•38 







101-43 



100-60 



100-29 



100-84 





The above analyses were not published at the time they were 

 made, as the formula derived from them was complex, and the 

 results could not be regarded as establishing the formula. 



* Taken from anal. I. 



