234 DR BROWN ON THE PRODUCTION OF SILICON FROM PARACYANOGEN. 



specimen, examined on the fifteenth day, contained traces of both paracyanogen 

 and cyanogen, although the latter was present in comparatively inappreciable 

 quantities. It is curious that crude paracyanogen, kept at these temperatures, 

 should retain absorbed cyanogen with such tenacity ; but the fact is quite intelli- 

 gible when viewed in connection with the astonishing retentive pOAvers of such 

 bodies as sulphur and carbon over hydrogen and some other light gases. This 

 well known property of these and some other inflammable simple radicals seems 

 to have confirmed DAVY in his ingenious hypothesis of the compound nature of 

 the so-called elements, if, indeed, it did not suggest the conception of it to his mind. 

 That great investigator imagined that these obdurate bodies might all be composed 

 of hydrogen and an unknown basis of intense affinities, the only difference, for 

 example, between oxygen and the densest of the noble metals being, that they 

 contain the two ingredient constituents of all bodies in different proportions ; and 

 he endeavoured to establish this conjecture by experiments with the voltaic pile.* 

 The unexpectedly large quantities of hydrogen procured from selenium, and some 

 other apparently simple bodies, seemed to indicate the likelihood of the wonder- 

 ful hypothesis in question, although it was so much at variance with the whole 

 physiognomy of the elemental scale that it never received the attention even 

 which it deserved. To return from this short digression: The manner in which 

 these mixed specimens of silicon, paracyanogen, and traces of cyanogen were ana- 

 lyzed was this : the product having been triturated with a large excess of chlorate 

 of potassa, and heated till the salt was wholly decomposed, the resulting chloride 

 of potassium was washed off the pure silicon, which, in its turn, was oxidated by 

 fusion with carbonate of potassa, and separated in the form of silicic acid. A 

 substance, suspected to be silicon, could not pass through a severer ordeal. 



t>. A tube of German glass, three inches long, weighing 90 grs. was charged 

 two-thirds full (8 grs.), and heated first one hour to about 800 Fahr. and then 

 another to the lowest visible glowing temperature. The object of this experiment 

 was to produce some silicon without acting on the apparatus. The contents hav- 

 ing been thrown into melted chlorate of potassa, the unchanged paracyanogen was 

 burned away, and silicon remained diffused through the chloride ; carbonate of 

 potassa was added in excess, and the whole once more ignited in the same pla- 

 tinum crucible ; the white saline product was decomposed by hydrochloric acid, 

 and the solution dried and ignited, all in the original crucible ; and there was 

 obtained 1.7 gr. of silicic acid. The weighed tube was cleaned, weighed again, 

 and found to have sustained no loss ; and there was no visible trace of action on 

 the glass. Similar results were obtained by several repetitions of this mode 

 of making the experiment of the reduction of paracyanogen. This observation 



* Elements of Chemical Philosophy, pp. 478-489. 



