Brush and Dana — Mineral Locality at BranchvUle. 201 



times, and enough water to increase the total volume to LOO 

 cm*, or a little more. A platinum spiral is introduced, a trap 

 made of a straight two-bulb drying-tube cut o£E short is hung 

 with the larger end downward in the neck of the flask, and 

 the liquid is boiled until the level reaches the marls put upon 

 the flask to indicate a volume of 35 cm 8 . Great care should be 

 taken not to press the concentration beyond this point on ac- 

 count of the double danger of losing arsenious chloride and 

 setting up reduction of the arseniate by the bromide. On the 

 other hand, though 35 em ; is the ideal volume to be attained, 

 failure to concentrate below 40 enr 1 introduces no appreciable 

 error. The liquid remaining is cooled and nearly neutralized 

 by sodium hydrate (ammonia is not equally good), neutraliza- 

 tion is completed by hydrogen potassium carbonate, an excess 

 of 20 cm 3 of the saturated solution of the latter is added, and 

 the arsenious oxide in solution is titrated by standard iodine in 

 the presence of starch. 



With ordinary care the method is rapid, reliable and easily 

 executed, and the error is small. In analyses requiring ex- 

 treme accuracy all but accidental errors may be eliminated 

 from the results by applying the corrections indicated. 



Art. XXVI. — On the Mineral Locality at Branchville, Con- 

 necticut: Fifth Paper; by George J. Brush and Edward 

 S. Dana. With analyses of several manganesian phos- 

 phates ; by Horace L. Wells. 



It is now nearly twelve years since we published our first 

 paper* upon the Branchville minerals. It will be remembered 

 that the material which formed the basis of our early work was 

 that which Mr. Fillow had brought to light in his excavations, 

 some two years previous, in search for mica. It was this lot of 

 minerals, sagaciously selected and preserved by Mr. Fillow, 

 that we found so remarkably rich in phosphates of manganese, 

 including a number of new and interesting species. f During 



* See this Journal, xvi. 33, 114, July and August, 1878; Second Paper, xvii, 

 359, 1879; Third Paper, xviii, 45. 1879: Fourth Paper, xx, 257, 1880. 



f It may be useful here to recall that our investigations have shown that, 

 besides apatite, amblygonite and some others, the following phosphates are 

 present: 



Lithiophilite : a manganese triphylite, essentially LiMnPO., ; massive, cleavable, 

 of a salmon-pink to clove-brown color. 



Eosphorite: a manganese childreuite, essentially MnAl(OH)P0 4 + 2PL0; in or- 

 thorhombic crystals and massive, of a rose-pink color. 



Triploidite: near triplite, essentially Mn(MnOH)P0 4 in fibrous aggregates and 

 monoclinic crystals isomorphous with wagnerite. 



Dickinson ite : a phosphate of manganese, iron and sodium; in bright green 

 chlonte-like foliated aggregates, rarely in pseudo-rhombohedral crystals. 



