Apparatus and Processes. 249 



the cup which held it, will be found to contain, silicon mixed with the 

 fluoride of potassium, and with this indeed the whole of the powder 

 deposited is contaminated. Silicuret of potassium is likewise formed 

 in the cup, since on the afFussion of water, a fetid evolution of sili- 

 curetted hydrogen ensues. By repeated infusions, first in cold, and , 

 afterwards in boiling water, aggreeably to the directions of Berzelius, 

 the silicon is left in the state of a brownish ash colored powder. 



Thus obtained, silicon does not appear to be acted on either 

 by sulphuric, nitric, fluoric, or muriatic acids ; nor when exposed to 

 nitrate of potash liquified by heat. It seems to be soluble for the 

 most part in a mixture of nitric and fluoric acid, which by analogy we 

 may call nitro-fluoric acid j but after exposure for eighteen hours to 

 this solvent, a small proportion of a black matter remained undissolv- 

 ed. This is, in all probability, carbon derived from the potassium, 

 which, according to Berzelius, when obtained by Brunner's process, 

 is liable to be combined with carbon. The solution of nitro-fluoric 

 acid, decanted from the residual black powder into a solution of 

 pearlash, gave a copious, white, gelatinous precipitate like silex, 

 which, when thrown into a large quantity of water, subsided undis- 

 solved. When on subjecting the silicon to red hot nitrate of potash, 

 anhydrous carbonate of the same alkali was added, so as to cooperate 

 with the nitre, an explosive efiervescence took place. AH the sili- 

 con disappeared, and a compound resembling the silicate of potash 

 was produced. This anomalous reaction may be considered as char- 

 acteristic of silicon. 



The impression that the black matter insoluble in the nitro-fluoric 

 acid, was carbon, is confirmed by the fact, that after the silicon had 

 been digested for some hours in strong nitric acid, and finally boiled 

 in it to dryness, it dissolved in nitro-fluoric acid without any such 

 residuum. 



2. Improved process for the evolution of Boron. 



By means of an apparatus represented by the annexed engraving, 

 I have succeeded in evolving boron by the reaction of potassium with 

 vitrified boracic acid, in vacuo, without encountering the evil of any 

 explosive action, to which the process, as heretofore conducted, in 

 pleno, has been found liable. 



A circular brass plate, is prepared, like the plate of an air pump, 

 so as to produce with any suitable receivers properly ground, an air- 

 tight juncture. It is supported on the upper end of a hollow brass 



