Re-examination of Microlite and Pyrochlore. 163 



by Prof. Shepard, on a separate portion of the mineral. Indeed, 

 his own results do not favor the conclusion he adopted. 



The columbic acid and lime represent, in their weights, nearly 

 their combining proportions. I do not, however, regard this coin- 

 cidence as proof, that all the columbic acid is really united to 

 all the lime, in the mineral. The recent discovery, by M. Rose, 

 of a columbate of uranium, may be regarded with interest, in 

 this connection. 



Pyrochlore. 



The specimens used in the following analysis, were from the 

 Fredericksvarn locality. The crystals were generally without 

 modifications ; but two of them had planes replacing the edges 

 of the octahedron, and exhibited cleavage lines. Their colors 

 varied from wax yellow to dark brown. Sp. gr. 4-203 to 4-221. 



Analysis. — A. 20 grains lost by heating 0-160, or 0-S00 per 100. 



B. The fine powder was dissolved in melted bisulphate of pot- 

 ash, and after separating all other substances, there remained 

 10-590 of pure columbic acid, or 52-950 per 100. 



C. After the fluids containing sulphate of potash, and the acids 

 used in washing the columbic acid of B, were neutralized by 

 ammonia, an excess of this alkali was added, and the pre- 

 cipitate which it produced was washed on a filter. The still 

 moist and yellowish brown mass was digested in the sulphydrate 

 of ammonia, which had been used on the columbic acid, for 

 twelve hours. By evaporation, this solution afforded a yellow 

 powder, which, by calcination, became a white oxide of tin, 

 weighing 0030. 



D. The mass on the filter, C, was redissolved in sulphurous 

 acid, containing sulphuric acid, and boiling water was used to 

 wash a few black flocks which remained. On heating the black 

 powder before the blowpipe flame, sulphur exhaled, and the addi- 

 tion of soda caused a globule of lead to separate ; converted into 

 oxide, it weighed 0-010. The soda globule left 0-030 of colum- 

 bic acid. Ammonia was used to again separate the oxides which 

 had been dissolved off the filter from lime, and the solution was 

 removed with the usual precautions, leaving the light yellow ox- 

 ides on the filter. 



E. The filter containing the oxides in D was digested in a so- 

 lution of oxalic acid ; warm water dissolved all the matter it con- 

 tained. Tartrate of ammonia and pure ammonia were added, till 

 a precipitate which first appeared was redissolved, and the fluid 



