on the alleged Conversion of Carbon into Silicon. 297 



change of tint. Having carefully selected 3*5 grs. of the 

 black residue so as to procure it free from the accidental ad- 

 mixture of sand, they were mixed with 20 grs. of carbonate of 

 potash prepared from the bitartrate and free from silica; this 

 mixture, which was perfectly black, was ignited for half an hour 

 in a closed platinum crucible, which was itself placed in a 

 covered earthen crucible carefully luted ; the fused residue 

 was black, and when treated with water left a black insoluble 

 powder; this, washed, collected, dried, and ignited in a pla- 

 tinum capsule and in contact with air, glowed like ignited 

 carbonaceous matter, and left an ash-coloured residue, which, 

 treated with chlorate and carbonate of potash, gave a fused 

 residuum entirely soluble in water; this solution, evaporated 

 to dryness with the addition of hydrochloric acid in excess, 

 and subsequently ignited, gave a slightly turbid solution with 

 water, which became perfectly clear on the addition of hydro- 

 chloric acid; this solution contained traces of platinum. The 

 first solution of carbonate of potash from the black residue 

 treated in the manner described, gave not the least indication 

 of silica.— (J. D. S.) 



Having observed that the black lining of the crucible was 

 precisely similar to the description given by Dr. Brown of 

 the films of silicon mentioned by him as lining the porcelain 

 crucible in which his experiment was mach?, and which pro- 

 cess he recommends as likely " eventually to be an ceconomi- 

 cal and convenient way of lining porcelain with silicon for 

 experimental purposes," we were desirous of ascertaining 

 whether a cheaper and more easily to be obtained substance 

 containing carbon, could not be advantageously substituted 

 for paracyanogen, so as to produce the desired object; we 

 therefore placed some lamp-black, mixed with a trace of per- 

 oxide of iron, in a Berlin crucible, into which it was tightly 

 rammed, and exposed this crucible, having previously put it 

 into an exterior one, which was covered and luted, to a 

 white heat for an hour and a half: when withdrawn it was 

 found to be coated, as high as the lamp-black had reached, 

 with a stain, differing only from that before alluded to as ob- 

 tained from paracyanogen, in being quite black ; this cruci- 

 ble was exposed to a red heat with free access of air for up- 

 wards of two hours, but the stain remained unchanged. — 

 (J. D. S.) 



We do not say that this is not silicon, but if it be, either 

 lamp-black is as capable of lining crucibles with silicon as 

 paracyanogen is, or at high temperatures the carbon is capa- 

 ble of reducing the silica of the glaze, and thus producing 

 the same effect. 



