﻿Chemistry. 317 









Measured. 



xx' 



124^124 



= 



28° 46' ) 



x"x'" 



124 ,s 124 



= 



28° 31' f 



xx" 



124 ^ 1 24 



— 



48° 44' / 



x'x'" 



124 ^ 124 



= 



48° 55' j 



zz' 



112 a 112 



— 



53° 47' ) 



z"z'" 



112^112 



= 



53° 44' f 



zz" 



112 ^ 112 



= 



44° 45' / 

 44° 46' \ 



z'z'" 



11 2 xv 112 



= 



mm'" 



110 ,s 110 



=r 



79° 25' 



Calculated (Kokscharowj. 

 28° 28' 



48° 54' 



53° 48' 



44° 46' 

 80° 10' 



A comparison of these angles and of those obtained by 

 Penfield shows a considerable variation among themselves ; 

 while on th'e whole they correspond tolerably well with the 

 measurements by Kokscharow of Kussian crystals. 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry. 



1. Contributions from Chemical laboratory of Harvard Col- 

 i, under the direction of Professor Cooke.* — Mr. Geokge W. 

 Leighton has made an analysis of a mica from Leon Co., Texas, 

 which attracted notice as it presented characters intermediate be- 

 tween those of the vermiculites and the muscovites. The mica is 

 opaque except in thin laminae and has obviously undergone altera- 

 tion. Cleavage basal, eminent ; laminae flexible, but brittle and 

 non-elastic. Luster pearly. Color brownish to yellowish green. 

 Double refraction negative. Biaxial ; with bisectrix nearly if 

 not absolutely normal to the cleavage, the optical angle in air 

 measuring about 37-J- , but could not be measured accurately on 

 account of opacity. In blowpipe flame the laminae separate, 

 swelling to more than double the original thickness, and melting 

 on the edges, showing fusibility 5-6. Blowpipe flame strongly 

 colored with potash, barely tinged with soda, and with traces of 

 lithia. No fluorine could be detected by the usual tests. 



The analysis was made in the usual way, fusing with Na 2 C0 3 

 for the silica, decomposing with HF for the alumina, iron, and 

 magnesia, and by Lawrence Smith's method for the alkalies. The 

 iron was all in the ferric condition, and was determined volu- 

 metrically after weighing A1 2 3 and Fe 2 3 together. The potash 

 was weighed as chloroplatinate, and the water was determined by 

 ignition. In the following table, the results of the analysis are 

 given in column I. In column II, are the corresponding per 

 cents of oxygen, and in column III, are given for comparison the 

 results of an analysis of a mica from Hirschburg, taken from Dana's 

 System of Mineralogy, last edition, and classed by him among the 

 muscovites. 



* Proceedings of the American Academy of Arts and Sciences, vol. xxii, 158. 



