236 Prof. Rose 07i a new and advantageous Method of 



sodium after diying it. On account of the difficult solubility of 

 tlie fluoride of sodium, the mass is very slowly acted upon by 

 the water, although the insolubility is somewhat diminished by 

 the preseuce of the chloride of potassium. After twelve hours 

 the mass has become so far softened that it may be removed 

 from the liquid and broken down in a porcelain mortar. Large 

 globules of aluminium are then discovered, weighing from 0*3 to 

 0*4 grm. (5 to 6 grains), which may be separated; latterly I 

 have found them of 0'5 grm. (7*7 grs.). 



The smaller globules cannot well be separated from the unde- 

 composed kryolite and the alumina always produced by washing, 

 owing to their being specifically lighter than the latter. The 

 whole is treated with diluted nitric acid in the cold ; the alumina 

 is not dissolved thereby, but the little globules then first assume 

 their true metallic lustre. They are dried and rubbed on fine 

 silk muslin, the finely-powdered undecomposed kryolite and 

 alumina pass through, while the globules remain on the gauze. 



The melted mass should be treated with water in a platinum 

 or silver vessel ; a porcelain capsule would be powerfully acted 

 upon by the fluoride of sodium. The solution, after standing 

 till clear, may be evaporated to dryness in a platinum capsule in 

 order to obtain the fluoride of sodium, mixed, however, with 

 much chloride of potassium. 



The small globules of aluminium may be iinited by fusion in 

 a small, well-covered porcelain crucible under a layer of chloride 

 of potassium. They cannot be united without a flux. They 

 cannot be united by mere fusion, like globules of silver for in- 

 stance, for though they do not appear to oxidize on ignition in 

 the air, they become coated with a scarcely perceptible film 

 of oxide which prevents their running together into a mass. 

 This fusion with chloride of potassium is always attended with 

 a loss of aluminium. A button weighing 3*85 grms. lost, when 

 so treated, 0-05 grm. The chloride of potassium when dissolved 

 in water, left a small quantity of alumina undissolved, but the 

 solution contained none. Another portion of the aluminium had 

 undoubtedly decomposed chloride of potassium, and a portion of 

 chloride of aluminium and chloride of potassium must have been 

 volatilized during the fusion. Other metals, as copper and silver *, 

 behave in a similar manner. 



I therefore followed the instructions of Deville, and melted 

 the globules under a stratum of chloride of aluminium and 

 sodium in a covered porcelain crucible. The salt was first 

 incited, and then the globules of metal added to the melted 

 mass. There is no loss, or a very trifling one of a few milli- 

 grams of metal, by this process. 



* Poggendorflf's Annahn, vol. Ixviii. p. 28/. 



