93 



are completely decomposed, the iron in the ferrocyanide of 

 sodium becomes peroxide, and this in a few hours falls to the 

 bottom of the pot. If the right quantity of saltpetre has 

 been added, a colourless mass of fused caustic soda remains, 

 but if too large an amount of nitre has been added, the liquor 

 becomes coloured deep green, owing to the formation of man- 

 ganate of soda. It is remarkable that, in the absence of nitrate 

 of soda, the cyanogen compounds act reducingly upon the 

 sulphide of sodium ; this is seen from the fact that a portion 

 of the soda lye, which gives no sulphide reaction with a lead 

 salt, produces a blackening after the caustic alkali has been 

 heated to redness. 



The graphite may be skimmed off the surface of the fused 

 alkali, and, when washed with water and hydrochloric acid, it 

 appears in the form of an extremely fine bright powder. If 

 allowed to swim on the top of the almost red hot fused soda, the 

 graphite is oxidized gradually, and, after a lapse of about three 

 or four hours, it altogether disappears. Heated in a platinum 

 crucible by itself it is incombustible, but it generally contains 

 small particles of charcoal mixed with it, and these undergo 

 oxidation. 



The temperature at which this evolution of graphite takes 

 place is a very low one, compared with that at which graphite 

 is liberated from cast iron, for a thin iron wire can scarcely be 

 brought to a visible red heat by dipping it into the fused 

 alkali. 



From this peculiar decomposition it would appear that we 

 have good reason to assume, that the carbon contained in 

 cyanogen is present in the graphite modification ; for, if this 

 be not the case, how is it that the easily combustible charcoal 

 can withstand the oxidizing action of the saltpetre, whilst none 

 of the iron of the ferrocyanide of sodium is reduced to the 

 metallic state? 



It has, besides, been lately shown by M. Caron, that the 

 formation of steel. /. e. the combination of iron with carbon in 



