124 M. Berzelius on Fluoric Acid. [Feb. 



List of the Articles sent to England by Major Macintosh. 



A skull, and three thigh bones. 

 A brass kettle. 

 A sheet of metal. 



Several strings of coloured glass beads. 

 Some strings of beads, apparently made of shells and bones. 

 The head of a pipe. 

 A conch shell entire. 



Several pieces of the same kind of shell shaped into 6rna- 

 ments. 



Article VI. 



On Fluoric Acid, and its most remarkable Combinations^ 

 By Jac. Berzelius. 



(Continued from vol. viii. p. 467.) 



Silicated Fluate of Potash. — When this salt is precipitated 

 from a weak acid, the liquid does not immediately become 

 turbid, but the salt which exists diffused through it in very 

 minute particles, communicates to it the property of reflecting 

 the prismatic colours : by degrees these subside and form a 

 transparent layer, which still exhibits a similar play of colours. 

 While moist, this salt presents the appearance of a gelatinous 

 mass, but is converted into a fine, soft, white powder by desic- 

 cation. It is very difficultly soluble in water, but not so much 

 so that it can in every case be employed advantageously in 

 making a quantitative determination of potash. It is rather 

 more soluble in boiling than in cold water, and if a saturated 

 solution be evaporated, the salt may be obtained in small crys- 

 tals, which are sometimes rhombs, and sometimes regular six- 

 sided prisms. The crystals are anhydrous. In a low red heat 

 it melts, and if the temperature be augmented, it boils and gives 

 off fluate of silica, but a very high temperature is necessary to 

 produce complete decomposition. In the open air, fluate of 

 silica is disengaged before the salt begins to undergo fusion. 

 If the ignition be performed in an open platinum crucible, parti- 

 cularly if the heat of a spirit lamp be employed, a portion of the 

 fluate is decomposed at the instant of its disengagement by the 

 circumambient vapour of water, and the neutral fluate which 

 remains at the conclusion of the decomposition is found to be 

 mixed with silica. Hence, when I wished to ascertain the 

 weight of the residual salt, I always placed the platinum crucible 

 containing the sihcated fluate within two others, and heated it 

 in a charcoal fire ; in these experiments, the interior of the first 



