W. J. Comstock—<A nalyses of some American Tantalates. 131 
ART. ree agi ee of some American Tanialates ; by W. J. 
Com (Contributions from the Laboratory of the Shef. 
eld “Scientific ey No. LVIL) 
THE following paper contains analyses of three American 
tantalates which have not been aati investigated, and 
which offer some points of especial interest 
Sang analy ‘zed was from a massive piece, a few ounces in 
weight. Specific gravity = 6°88. 
I. i. Me 
Ta.05 60°50 59°35 59°92 1349 } asat 
Nb20s 23°02 24°24 23°63 0882 5 ~ 
e 2:90 12°82 12°86 
MnO 3-09 3°03 0431 } -2302 
MgO 0°35 0°32 0°34 
Total 99°86 9°76 
R,0;: RO = 1: 1°03 and 6b): Ta.O, = 1: 1°53 or nearly 2: 3. 
o. II was from Northfield, Mass. The portion analyzed w 
f Mean. Ratios. 
Ta.O; 57-23 56°57 56°90 “1281 9281 
Nb.O; 26°62 27°01 26°81 *1000 ' 
FeO 10°11 9°98 10°05 "1397 t “9995 
MnO 5°92 5°85 5°88 “0828 
AX otal, 99°88 99°41 
R.0O,: RO = 1°025: abs eae egos 5-1. 
No. III was from Branchville, Conn. Its occurrence was 
described by Messrs. Brush and Dana,* and the specimen anal- 
yzed was given to me by them. Only a small quantity of the 
mineral was found at the locality, and enough for one analysis 
was all that could be obtained pure. Its powder was brownish- 
ay, and in thin fragments it was slightly translucent. Spe- 
cifie gravity =6-59. 
Ta.0 52-29 T173 ). 
Nb:0; 30°16 apt oes 
MnO 15°58 2194 
FeO 0°43 0059 } +2319 
CaO 0°37 0066 
Total, 
R,O D1) FOOT on Nb.O; : oie ee 1: 104. 
Tantalic aid: niobie acids were separated by Marignac’s 
method,+ in the application ¢ of which I have a all neces- 
* This Journal, July, 1878, p. The specific gravity, by a typographical 
error, as I am informed, is there sien 56 — of 6°5 
+ Archive 8 des Sci. phage et Nat., Jan., 
