Mr Cqnnell on the Chemical Constitutwn of GadoUmte. 301 



of this mineral, particularly with a view to the question whether 

 glucina enters into their constitution in notable quantity. 



The only specimen of gadolinite which I could procure, ca- 

 pable of affording a quantity with which I could attempt deter- 

 mining the proportion of its constituents, (and that much less 

 than I could have wished, being only ten grains,) was one of 

 which the locality was not more particularly marked than as 

 being Fahlun ; and which exactly resembled, both as to the 

 matrix and as to the mineral itself, specimens which I have 

 seen labelled as from Broddbo near Fahlun. The gadolinite 

 which it contained occurred in grains of the size of a small pea 

 disseminated in granite. Its colour was black, or very dark 

 green ; lustre vitreous, and fracture conchoidal; and it possess- 

 ed all the other usual external characters of the mineral. 



Besides this specimen, which was the principal subject of 

 analysis, two others, of smaller size, were examined generally, 

 the one from Finbo, and the other, I have reason to believe, 

 from Broddbo. 



The manner of proceeding was as follows: — The mineral, 

 reduced to fine powder, was boiled in nitro-muriatic acid ; and 

 the silica afterwards obtained in the usual manner. From the 

 solution of the other constituents, the oxide of cerium was sepa- 

 rated by means of crystals of sulphate of potash, and subsequent 

 solution of the double salt, and precipitation by boiling with 

 potash. Thus far the analysis is sufficiently simple ; but the 

 best method of obtaining the remaining constituents is not so 

 easily determined. To separate the oxide of iron, I tried ben- 

 zoate of ammonia, in the preliminary examination of one of the 

 smaller specimens, but I found, as Dr Thomson also observed, 

 that not merely benzoate of iron was thrown down, but some of 

 the other constituents of the mineral also. I then had recourse 

 to the method of tartaric acid, and hydrosulphuret of ammonia. 

 1'he liquid, which had been acted on by the crystals of sulphate 

 of potash, was precipitated by ammonia, and the precipitate, 

 after being collected on a filter, was dissolved in muriatic acid. 

 Solution of tartaric acid, and afterwards ammonia in excess, 

 were added, and the iron precipitated by hydrosulphuret of 

 ammonia. The residual liquid was then evaporated to dryness, 

 and the residue completely incinerated by long exposure to a 



