Intelligence and Miscellaneous Articles. 541 
ON THE PRODUCTION OF GRAPHITE BY THE DECOMPOSITION OF 
CYANOGEN COMPOUNDS. BY DR. P. PAULT. 
The mother-liquors obtained from the evaporation of a solution of 
the so-called black ash are now commercially worked for caustic 
alkali. These liquors contain the following compounds :.— 
1. Chiefly hydrate of soda, 
2. Some quantity of carbonate of soda. 
3. Several sulphur compounds of sodium: viz. sulphide of sodium, 
hyposulphite of soda, sulphite of soda, and sulphate of soda. 
4, Sulphide of iron held in solution by the sulphide of sodium. 
5. Chloride of sodium. 
6. Several cyanogen compounds of sodium, and especially ferro- 
eyanide of sodium. 
These liquors are evaporated in large cast-iron pots, and in order 
to destroy or oxidize the sulphides of sodium and iron, as also the 
cyanogen compounds, an equivalent quantity of soda-saltpetre is 
added. All the oxidable sulphur compounds, together with the 
small quantity of sulphide of iron, are changed to sulphate of soda 
and peroxide of iron by the nitrate of soda in the boiling hquor, ata 
temperature not below 260° to 270° F. The cyanogen compounds, 
on the other hand, are not decomposed by the nitre until the 
liquor begins to pass from the watery into the dry fusion, and the 
uncombined water of the hydrate of soda has been driven off. When 
the whole mass of alkali (generally about four tons) reaches a low red 
heat, a regular evolution of gas is observed; this is evidently owing 
to the oxygen produced by the decomposition of the nitrate, and to 
the nitrogen from the decomposition of the cyanides; at the same 
time a plentiful liberation of graphite is observed, covering the whole 
surface of the liquor with a bright layer of graphite. ‘This liberation 
of graphite is still more plainly seen if no nitre be added to the liquor 
at first, or only so much as is sufficient to oxidize the sulphur com. 
pounds; but if a few pounds of nitrate of soda be added when the 
water has been driven off, and the mass is allowed to become red-hot, 
a violent reaction takes place, and a large quantity of graphite is set 
free. ‘This sudden liberation of graphite proves that this substance 
cannot be derived from the cast iron of the pot in which the fusion 
is made. So violent is the evolution of gas, that a complete cloud 
of fine particles of caustic soda is carried up into the air, rendering 
it almost impossible to remain in the neighbourhood of the operation. 
In this way all the cyanogen compounds are completely decomposed, 
the iron in the ferrocyanide of sodium becomes peroxide, and 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 black- 
ening after the caustic alkali has been heated to redness. 
The graphite may be skimmed off the surface of the fused alkali; 
