242 DR BROWN ON THE PRODUCTION OF SILICON FROM PARACYANOGEN. 



little fragments are colourless like glass. In fine, it is possessed of the crystalline 

 structure without the crystalline form. Its specific gravity is 2.11. 



3. Introduce an ounce of anhydrous ferrocyanide of potassium, mixed with 

 twice as much cyanide of potassium,* into a Berlin crucible of the capacity of five 

 ounces, and lute the lid tightly on, without leaving any aperture for the escape of 

 volatile products. Put the whole into a large earthen crucible, half full of gyp- 

 sum paste, and then filled with the same, so as to include the smaller crucible in 

 a mass of stucco. After setting, and desiccation at 400, let it be heated to the 

 highest red in a wind-furnace for eight hours. 



The design of this process is twofold ; to hinder, by pressure, the quick de- 

 composition of the constituent paracyanogen, and prevent the sublimation of the 

 ingredient and superadded cyanide; and, by this double artifice, to produce the slow 

 transformative decomposition of the former floating free in the liquefied excess of 

 the latter, in the expectation that, in accordance with the indications of a great 

 many proximate trials, the siliciuret should be evolved crystalline in both struc- 

 ture and form. The product is interesting : water dissolves out the cyanide, and 

 there remains neither paracyanide nor carburet, but a large-grained sediment of 

 transparent, nearly colourless, and very hard little crystals of siliciuret of iron. 

 They resemble white sand, or cut-glass ; and can be pulverized only in a steel 

 mortello. Reduced to an impalpable powder, and ignited in the air, they oxidate, 

 and are changed into a red calx, from which hydrochloric acid extracts peroxide 

 of iron and separates silicic acid. Chlorate of potassa may be deoxidated on them, 

 in any excess, without producing the slightest effect. They decompose melted 

 carbonate of potassa with eifervescence, silicated alkali and iron, in the peculiar 

 condition already noticed, being the products of the reaction. When prepared 

 during a longer time, and at a lower temperature, than has been directed above, 

 they are opaque, like white enamel ; heated to a red heat out of the air, they 

 become clear and colourless ; and, when subjected to the power of a full white 

 heat in shut iron tubes, they assume a green tinge, and resemble the chrysolite. 

 Their specific gravity is 2.53. This number was found by introducing 10 grs. of 

 the sand into a common density-bottle, which was then weighed after it had been 

 filled up with distilled water: The latter weight, subtracted from the known 

 weight of the bottle when filled with water alone increased by 10 grs., gave the 

 weight of a volume of water equal to the bulk of 10 grs. of the substance under 

 examination. They are infusible by the common blast-furnace of the smithy and 

 the ordinary blowpipe, so that the sand cannot be run into large masses ; but, 



* The cyanide of potassium employed in the performance of these experiments was partly prepared 

 from the ferrocyanide of potassium by heat, and partly procured from a London manufactory ; but in both 

 cases it was ascertained to be completely free of silicic acid. 



