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Cyanides from Ammonia and Alkali Carbonates.-
Two important processes which have been large producers of cyanide,
utilising the same reactions but under considerably different
working conditions, fall under this head. In Siepermann's process
(G.P. 38012 of 1886; B.P. 13697 of 1881), 9350 and 9351 of 1900)
a dry mixture of 2 parts of wood charcoal and 1 part of potassium
carbonate is introduced into the upper end of a vertical iron
retort, and is treated at a dull red heat with dry ammonia gas
introduced at a point about halfway down the length of the retort.
Absorption of the ammonia occurs with production of potassium
cyanate, probably through the intermediate formation of
potassium carbamate (according to Pfleger, see Deuts.
Gold-u.-Silber-Scheideanstalt vorm. Roessler, V. lntern.
Kongress fuer Angwandte Chimie,Berlin, 1903, 1, 638):
The product then falls into the lower part of the retort,
which is maintained at a bright red heat.
At the higher temperature the cyanate is converted into cyanide,
and carbon monoxide is produced which escapes through the upper
part of the retort with the hydrogen formed by the decomposition
of ammonia. According to Pfleger (I.e.) the conversion of the
cyanate proceeds in two stages .(c.f. . Dreclisel, J. pr. Chem.
1877, (ii], 16, 201, on a similar decomposition of alkaline earth
cyanates, Dreclisel, J. pr. Chem. 1880, [ii], 21, 77) ; Some of
the potassium cyanamide may decompose, directly into cyanide,
potassium and nitrogen, as this reaction is known to occur below 800
・C in the absence of excess charcoal.
The product of Siepermann's process is allowed to cool out of contact
with air, and is then systematically leached with exclusion of air
(B.P. 9351 of 1900). Potassium cyanide may be precipitated from the
extract by adding excess of potassium carbonate, or better by
evaporating nearly to dryness and extracting unchanged potassium
carbonate with a minimum quantity of water at 66 ・C. The residue,
containing potassium cyanide and some unconverted cyanate,
is treated with refrigerated water (between --18' and +.5辰.) to
dissolve the cyanide and leave the cyanate, and the cyanide is
crystallzed as a damp, deliquesant mass (B.P. 9352 of 1900).
Two important processes which have been large producers of cyanide,
utilising the same reactions but under considerably different
working conditions, fall under this head. In Siepermann's process
(G.P. 38012 of 1886; B.P. 13697 of 1881), 9350 and 9351 of 1900)
a dry mixture of 2 parts of wood charcoal and 1 part of potassium
carbonate is introduced into the upper end of a vertical iron
retort, and is treated at a dull red heat with dry ammonia gas
introduced at a point about halfway down the length of the retort.
Absorption of the ammonia occurs with production of potassium
cyanate, probably through the intermediate formation of
potassium carbamate (according to Pfleger, see Deuts.
Gold-u.-Silber-Scheideanstalt vorm. Roessler, V. lntern.
Kongress fuer Angwandte Chimie,Berlin, 1903, 1, 638):
The product then falls into the lower part of the retort,
which is maintained at a bright red heat.
At the higher temperature the cyanate is converted into cyanide,
and carbon monoxide is produced which escapes through the upper
part of the retort with the hydrogen formed by the decomposition
of ammonia. According to Pfleger (I.e.) the conversion of the
cyanate proceeds in two stages .(c.f. . Dreclisel, J. pr. Chem.
1877, (ii], 16, 201, on a similar decomposition of alkaline earth
cyanates, Dreclisel, J. pr. Chem. 1880, [ii], 21, 77) ; Some of
the potassium cyanamide may decompose, directly into cyanide,
potassium and nitrogen, as this reaction is known to occur below 800
・C in the absence of excess charcoal.
The product of Siepermann's process is allowed to cool out of contact
with air, and is then systematically leached with exclusion of air
(B.P. 9351 of 1900). Potassium cyanide may be precipitated from the
extract by adding excess of potassium carbonate, or better by
evaporating nearly to dryness and extracting unchanged potassium
carbonate with a minimum quantity of water at 66 ・C. The residue,
containing potassium cyanide and some unconverted cyanate,
is treated with refrigerated water (between --18' and +.5辰.) to
dissolve the cyanide and leave the cyanate, and the cyanide is
crystallzed as a damp, deliquesant mass (B.P. 9352 of 1900).
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