470 



nitrogen only, as Dr Brown has stated, but also carbonic acid and 

 carbonic oxide ; and the residue contained carbon. The authors, 

 however, obtained some silica in the greater number of cases ; 

 occasionally none, even from paracyanogen prepared by Dr Bi'own 

 himself ; frequently very little ; and never nearly the quantity which 

 ought to have been obtained had the whole carbon become silicon, 

 but fifteen per cent, at the utmost. 



They also varied the process with Paracyanogen, by heating it 

 alone for three days over an argand gas-flame in a malleable-iron 

 crucible, luted and coated with stucco. A nut-brown powder, weigh- 

 ing 4.2 grains, was thus obtained from 18.5 grains of Paracyanogen, 

 When 3.9 grains of this were fused with carbonate of potash, and 

 the product treated as if it contained silicate of potash, the authors 

 obtained 8.4 grains of a substance undistinguishable by any charac- 

 ters from silica. Had the brown powder been silicon, the product 

 in this form should have been 8.11 grains. This experiment was 

 twice repeated unsuccessfully. 



The authors believe the substance obtained on this and other 

 occasions to have been silica on the following grounds. It was a 

 white, gritty powder, unalterable by ebullition in aqua regia for 

 hours, or by exposure to a white heat, or to the full blow-pipe blast ; 

 fusible into a glass bead with carbonate of soda before the blow- 

 pipe ; soluble with effervescence in fused alkaline carbonates, and 

 recoverable from the product without any change of property ; con- 

 vertible, when heated with potassium, into a substance undistinguish- 

 able from silicon ; and yielding fluo-silicic acid when heated with 

 fluor-spar and sulphuric acid. 



In conclusion, they deny that it is possible to ascribe the appear- 

 ance of the silicon and silica in these experiments either to impurity 

 of the re-agents employed, or to action upon the vessels constituting 

 the apparatus. They consider, thei-efore, that silicon was produced 

 in an anomalous manner ; but they do not admit that it is proved to 

 have come from the carbon ; for it might have been derived as well 

 from the nitrogen, or from both elements together. And they state, 

 that they abandoned the farther trial of Dr Brown's processes, be- 

 cause they became satisfied, that his experiments cannot be repeated 

 at will ; and that the conditions essential to success have not been 

 ascertained, nor the details of the processes sufficiently worked out, to 

 aiford the means of establishing the transmutability of carbon into 

 silicon on quantitative grounds. 



