on the alleged Conversion of Carbon into Silicon. 303 



of silica contained in the carbonate of potash was thus ascer- 

 tained, 200 grains of it were mixed with 50 grains of dry prus- 

 siate of potash, and ignited to redness in the same iron tube, 

 closed with an iron plug and luted with China clay, for three 

 hours ; when cool, the contents of the tube were washed out 

 with water and a little hydrochloric acid ; a powerful odour of 

 prussic acid was observed, and when the hydrochloric acid 

 had been added to supersaturation, abundance of Prussian 

 blue was formed ; this was evaporated to dryness, and pure 

 nitric acid added to the residue, the mixture transferred to a 

 flask and heated ; when the Prussian blue was entirely decom- 

 posed, the contents of the flask were evaporated to dryness, 

 ignited, and boiled with water and hydrochloric acid ; the co- 

 lourless insoluble matter collected, dried and ignited, proved 

 to be silica, and weighed 0*33 grain, showing a gain of 0*03 

 grain of silica, a quantity so small as readily to have been 

 originally mixed with the 50 grains of ferrocyanide of potas- 

 sium, or to be merely the error of experiment. — (R. H. B.) 



When 30 grains of dried ferrocyanide of potassium were 

 mixed with four times its weight of pure carbonate of potash 

 and ignited in an iron box, inclosed in a closely covered and 

 luted earthen crucible, to a white heat for three hours, the iron 

 box was found on examination to have fused, and this fused 

 iron quite malleable : this experiment was of course spoilt, and 

 is merely mentioned to show the heat employed by us when we 

 speak of a white heat. — (J. D. S.) 



Another experiment, with twice the quantities of ferrocya- 

 nide and carbonate employed in the last experiment, and ex- 

 posed to a full yellow heat for three hours, also failed from the 

 energetic action of the fused contents on the iron box, by 

 which the bottom of the box was corroded and perforated. 

 —(J. D. S.) 



Another experiment was tried upon 150 and 600 grains 

 of the ferrocyanide and carbonate respectively, and ignited in 

 a gun-barrel, protected by luting and well secured at the orifice, 

 for six hours, at a full yellow heat. Notwithstanding the pre- 

 caution of luting, the gun-barrel was corroded, and evidently 

 from the action of the fused materials, and thus a great portion 

 of the contents were lost; what remained was washed out by 

 digesting water upon it for twenty-four hours, and the black in- 

 soluble matter separated from the alkaline solution, which latter 

 evolved a strong odour of hydrocyanic acid on the addition 

 of hydrochloric acid ; the black residue, when ignited, was con- 

 verted into a reddish brown powder, entirely soluble in hydro- 

 chloric acid : when these two solutions were evaporated toge- 

 ther to dryness, and the Prussian blue formed decomposed by 



