232 DR BROWN ON THE PRODUCTION OF SILICON FROM PARACYANOGEN. 



only that it was denser and darker. It was thrown into carbonate of potassa, pre- 

 viously fused with a little nitre in a platinum crucible ; reaction and effervescence 

 speedily ensued, and ended in its solution and the production of a transparent 

 liquefied compound. On refrigeration, this was decomposed by an excess of 

 hydrochloric acid in the crucible in which it had been formed. The acid solution 

 was evaporated to dryness, and the product ignited. Water now dissolved away 

 chloride of potassium, and left a fine, white, gritty powder, insoluble alike in acids 

 and alkalis, infusible in melted microcosmic salt, but instantly dissolving with 

 effervescence in fused carbonate of potassa, and then forming a saline solution in 

 water, from which it was separated by acids as a bulky gelatinous hydrate, which 

 was dissolved by both acids and alkalis, and became insoluble in the former by de- 

 siccation at a temperature short of redness, and in both by the process of ignition. 

 The properties thus presented by the white gritty powder are the most remarkable 

 and distinctive properties of the silicic acid. Such is one method of preparing 

 silicic acid from paracyanogen and carbonate of potassa. The carbonate employed 

 in this and all the following experiments was prepared from the bitartrate of 

 potassa, and ascertained to be pure. 



It must be added, that the operation now described is difficult of per- 

 formance. If the heat be too low, an outer crust of silicon protects the para- 

 cyanogen from complete decomposition. If it be so high as to fuse the para- 

 cyanogen, the decomposition is swift and perfect, but the product is spread over 

 the interior of the crucible, which is lined with a thinner or thicker coating of 

 pure silicon, incapable of being separated from the porcelain by mechanical means. 

 Even in this case, however, it is easy to prove that the lining film is silicon, as 

 the reactive characters of that substance are quite unique. This may eventually 

 be an economical and convenient way of lining porcelain with silicon for experi- 

 mental purposes. 



4. Two grains of the dark ignited substance procured by the last process yielded 

 4.11 grs. of silicic acid ; 1 gr., 2.06 grs. ; and 0.8 gr., 1.57 gr. The subject of these 

 synthetic experiments was inferred to have been pure silicon, because the latter 

 numbers of the series are within hundredths of the weights of silicic acid which 

 should be produced from the corresponding weights of silicon, according to the 

 generally received atomic weight of that body. 



Although it appears to be the direct inference from these observations that 

 silicon was produced from paracyanogen, some may suppose it equally probable 

 that, by some unintelligible act of substitution, the silicon may have been brought 

 out of the glass tubes and the porcelain crucible in which it made its appearance. 

 Now, it is impracticable to remove this objection to the composition of the appa- 

 ratus as a source of fallacy in this form of the experiment ; because the pro- 



