1835.] Chemical Analysis of Gadolinite, fyc. 407 



Suspecting that the increase of weight in this analysis, 

 which rather exceeds 4 per cent., might have been owing 

 to the yttria not having been sufficiently ignited, * it was 

 repeated in the following manner : — 



A. 30 grs. of the finely powdered mineral were boiled 

 in a flask with nitro-muriatic acid till the whole was decom- 

 posed. The silica separated in the usual way, and most 

 carefully washed with boiling distilled water, weighed, 

 after ignition, 7*3 grs. It was beautifully white and 

 pure. 



B. The residual solution was mixed with sal-ammoniac, 

 and evaporated to dryness. When again dissolved only a 

 mere trace of platinum remained. 



C. The solution was now mixed with oxalic acid, and, to 

 ensure the precipitation of any manganese that might exist 

 in the mineral, the whole was evaporated to dryness. The 

 white matter remaining undissolved on digesting the mass 

 in water, after being well washed and ignited, weighed 15 

 grs. It was of a light-yellow colour. 



D. It was dissolved in nitric acid. The solution was 

 evaporated to dryness, the residue dissolved in a small 

 quantity of water, and crystals of sulphate of potash were 

 allowed to remain in the solution for a week. The clear 

 liquid was then drawn off, and the white matter, after being 

 well washed in a saturated solution of sulphate of potash, 

 was dissolved in dilute nitric acid, and precipitated by am- 

 monia, and boiled in a flask, to ensure the complete sepa- 

 ration of the sulphuric acid. The peroxide of cerium, after 

 ignition, weighed 1*400 grs. = 1*3 grs. protoxide. 



E. The sulphate of potash solution from (D) was mixed 

 with a solution of carbonate of ammonia in great excess. 

 To what remained after the clear liquid had been drawn off" 

 fresh solutions were added, and this was repeated six times 

 before the whole was dissolved. There remained only a 

 few flocks, not weighing 0*01 gr. As they became black 

 when dried they probably consisted of oxide of manganese, 

 but the quantity was too small to permit the use of re-agents 

 to determine its nature. 



* We had found that the carbonate of cerium is not decomposed by exposure 

 to a pretty strong red heat. 



