Year: 1897

page_text: I, DR. AUGUST KNOP, of Rheinau, Baden, in the Empire of Germany, do hereby
declare the nature of this invention to be as follows:-
All previous attempts to prepare nitrites from nitrates by a method other than
that depending on reduction with lead, have yielded no practical result.
There are diverse processes known which employ sulphur, or sulphur com-
pounds, or carbon compounds.
Methods which make use of sulphur cannot well be carried out in practice
because the reaction is unusually violent, being attended by deflagration, and the
yield of nitrite is very small. For the same reason reduction with carbon in the
form of charcoal, coal, etc., cannot be effected in practice.
If carbon in the form of graphite or coke is allowed to attack fused saltpetre,
the carbon. enters into the reaction at a high temperature without deflagration.
The quantity of nitrite formed, however, is so small that a profitable preparation
is not to be thought of.
The process which forms the subject of my invention, however, renders possible
the use of carbon in its cheapest form by adding a certain quantity of caustic
alkali to the molten nitrate; the carbon is employed in the form of fine powder
which has also been mixed with melted caustic alkali.
The addition of caustic alkali acts, broadly, in this way: viz. that the melted
mass is mobile throughout the whole operation and that the oxidation of the carbon
proceeds quickly at a comparatively low temperature, the resulting carbon dioxide
being fixed by the caustic alkali. By mixing the carbon with fused caustic
alkali, the ready intermixture of the former with the molten mass (of nitrate)
is ensured.
By this method the re-action occurs in a short time, with nearly theoretical
yield and with such smoothness as can not be realised by the use of nitrate and
carbon, without the addition of caustic alkali.
Of the raw materials in question, viz. coal, graphite, coke, etc., coke has proved
the best.
The following quantities are used for preparing sodium nitrite:-
31 kilos of coke are stirred into 120 kilos of fused caustic soda, the molten mass
poured out and allowed to cool. 300 kilos of salpetre are then melted with
120 kilos of 90 % caustic soda in a pot, provided with a stirrer, and the caustic
soda containing the coke is introduced in pieces, a little at a time and with stirring.
The reaction proceeds with moderate frothing and is finished in some 3-4 hours.
The quantity of nitrite formed corresponds nearly with the theoretical yield. The
reaction may be expressed by the following equation:-
-

page_text: The finished melt consists of sodium carbonate, caustic soda, and nitrite, and the
last named can easily be obtained pure.
This process has great economical advantage over others. In the same time
nearly twice as much nitrite as is possible by the lead process in a melting pot,
can be produced, with a corresponding economy of fuel and wages. The amount
of coke consumed is insignificant. The caustic soda is recovered in a simple way
by causticising the sodium carbonate and is used again in the process.
Dated this 22nd day of February 1897.
ABEL & IMRAY,
Agents for the Applicant."
I, DR. AUGUST KNOP, of Rheinau, Baden, in the Empire of Germany, do hereby
declare the nature of this invention and in what manner the same is to be per-
formed to be particularly described and ascertained in and by the following
statement:-
All previous attempts to prepare nitrites from nitrates by a method other than
that depending on reduction with lead, have yielded no practical result.
There are diverse processes known which employ sulphur, or sulphur com-
pounds, or carbon compounds.
Methods which make use of sulphur cannot well be carried out in practice
because the reaction is unusually violent, being attended by deflagration, and the
yield of nitrite is very small. For the same reason reduction with carbon in the
form of charcoal, coal etc, cannot be effected in practice.
If carbon in the form of graphite or coke is allowed to attack fused saltpetre,
the carbon enters into the reaction at a high temperature without deflagration.
The quantity of nitrite formed, however, is so small that a profitable preparation
is not to be thought of.
The process which forms the subject of my invention, however, renders possible
the use of carbon in its cheapest form by adding a certain quantity of caustic
alkali to the molten nitrate; the carbon is employed in the form of fine powder
which has also been mixed with melted caustic alkali.
The addition of caustic alkali acts, broadly, in this way, viz:-that the melted
Bass is mobile throughout the whole operation and that the oxidation of the carbon
proceeds quickly at a comparatively low temperature, the resulting carbon dioxide
being fixed by the caustic alkali. By mixing the carbon with fused caustic
alkali, the ready intermixture of the former with the molten mass (of nitrate)
is ensured.
By this method the re-action occurs in a short time, with nearly theoretical
yield and with such smoothness as can not be realised by the use of nitrate and
carbon, without the addition of caustic alkali.
Of the raw materials in question, viz. coal, graphite, coke etc, coke has proved
the best.
The following quantities are used for preparing sodium nitrite:-
31 kilos of coke are stirred into 120 kilos of fused caustic soda, the molten mass
poured out and allowed to cool. 300 kilos of saltpetre are then melted with
120 kilos of 90 per cent caustic soda in a pot, provided with a stirrer, and the
caustic soda containing the coke is introduced in pieces, a little at a time and with
stirring. The reaction proceeds with moderate frothing and is finished in some

page_text: 3-4 hours. The quantity of nitrite formed corresponds nearly with the
theoretical yield. The reaction may be expressed by the following equation:-
2 NaNo + 2NaOH + C = 2NaNO, NaCО¸ + H₂O
The carbon is oxidised to carbon dioxide which combines with the caustic soda.
The finished melt consists of sodium carbonate, caustic soda, and nitrite, and the
last named can easily be obtained pure.
This process has great economical advantage over others. In the same time
nearly twice as much nitrite as is possible by the lead process in a melting pot,
can be produced, with a corresponding economy of fuel and wages. The amount
of coke consumed is insignificant. The caustic soda is recovered in a simple way
by causticising the sodium carbonate and is used again in the process.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is:-
"
Manufacture of nitrites by heating nitrates with carbon, coke in particular, in
presence of caustic alkali, substantially as described.
Dated this 3rd day of November 1897.
ABEL & IMRAY,
Agents for the Applicant.