218 Goooh and Boynton — Estimation of Barium. 



described is obviously only approximate, some barium chloride 

 going into solution in the 2:1 mixture of acetone and acetyl 

 chloride, while the solubility of the strontium chloride turns 

 upon the amount of water originally present — that is, upon the 

 development of hydrogen chloride: 



It appears, therefore, that the method which rests upon the 

 action of a 4:1 mixture of acetone and acetyl chloride upon the 

 concentrated solution of the chlorides affords easy and exact 

 means for the separation and estimation of barium associated 

 with calcium and magnesium. It is not recommended for the 

 separation of barium from strontium. 



Art. XXI. — A Feldspar Aggregate Occurring in Nelson 

 Co., Virginia; by William M. Thornton, Jr. 



Near Rose's Mill in Nelson Co., Virginia, the General 

 Electric Company recently carried on some mining operations 

 with the view of obtaining rutile, where it occurs as a rock- 

 forming mineral in the unique rock type "nelsonite."* To give 

 some idea of the nature of this peculiar rock, an analysis of the 

 rutile phase is here inserted : 



Analysis of JVelsonite. — General Electric Company's mine' 

 1-^ miles northwest of Rose's Mill. Essential minerals :— Rutile 

 (Ti0 2 ) and apatite (Ca 5 FP 3 12 ). Accessory minerals : — Ilmen- 

 ite (FeTiO,), pyrite (FeS s ), and quartz (SiO a ). 



Si0 2 0-67 per cent 



Fe 3 2-87 



FeO 5-04 " 



MgO 0-15 " 



CaO 12-16 " 



H.O (at J10° C.) 0-09 



H„0 (above 110° C.) 0-11 



TiO„__ .... 69-67 " 



P 2 0" 5 9-41 



CI .. i trace " 



F 0-70 



S 0-34 " 



101-21 

 Excess O — 0-39 



Summation = 100-82 



At this place the narrow, well-defined dike of nelsonite 

 intersects a metamorphosed pegmatite. The pegmatite is 



*Name proposed by T. L. Watson, Director Virginia Geological Survey. 

 Sae Mineral Resources of Virginia, 1907, p. 300. 



