342 



of copper or iron in the way followed for obtaining- paracyanogen, 

 the interior of the tubes was found to be lined with scales, which 

 consisted, not of paracyanide or carburet of these metals, but of 

 their siliciuret. And when paracyanogen was heated in a pla- 

 tinum crucible several times in succession till the crucible would 

 absorb nothing more, a compound was obtained which was a sili- 

 ciuret of platinum, containing four per cent, of silicon. 



3. When paracyanogen is decomposed in the preceding experi- 

 ments, the nitrogen given oflf" corresponds with what is conta? 



by theory in the compound which yields it. A variety of experi- 

 ments of analysis were mentioned to this effect ; from which a 

 further corroboration was derived of the conclusion derived from 

 the author's previous researches, that the silicon could come only 

 from the carbon of the paracyanogen. 



4. A siliciuret may be obtained from the paracyanide of iron. 

 Under this section, the author first described the process by which 

 a pure paracyanide of iron may be obtained from ferrocyanide of 

 potassium ; and stated that he had found this compound to consist 

 of one equivalent of nitrogen, two of carbon, and one of iron. He 

 then observed that he had been led to suppose this compound to be 

 the true compound radicle of the so-called ferrocyanides ; ou which 

 subject he proposed to make ere long a distinct communication to 

 the society. He next proceeded to explain the results of nu- 

 merous experiments on the influence of heat on the paracyanide 

 of iron ; from which it appeared that, under a high temperature 

 and pressure, a compound was obtained, in which carbon could 

 not be detected, but instead of it silicon, in the proportion of 28.5 

 per cent. To these remarks were added others on ferrocyanide 

 of potassium, which he considers to be resohed in the process 

 into cyanide of potassium evolved by sublimation, and paracy- 

 anide of iron, which at the same time is decomposed, and yields 

 disiliciuret of iron. The product obtained in these two ways is 

 in general partly in the form of a coaly powder, partly in fused 

 obsidian-like masses. But if the ferrocyanide of potassium be 

 heated with its own weight of cyanide of potassium, as a non-re- 

 active flux, the disiliciuret is obtained in a semicrystalline form, 

 which in fine powder is colourless, and is seen before the micros- 

 cope to be transparent like glass ; and sometimes there is an 

 approach to a crystalline form, nay, small particles may be dis- 

 covered with the microscope which are regular octahedres. The 

 disiliciurets of iron thus produced wpre treated of by the author in 



