Improvements in the Manufacture of Nitrites of Soda and Potash.
Year: 1896

page_text: Date of Application, 3rd Mar., 1896
Complete Specification Left, 27th Nov., 1896-Accepted, 2nd Jan., 1897
KJVISIONAL SPECIFICATION.
Improvements in the Manufacture of Nitrites of Soda and Potash.
LEWIS GORDON PAUL 123 Palace Road, Tulse Hill, London S.W. Manu-
facturing Chemist do hereby declare the nature of this invention to be as
follows:-
This invention relates to the manufacture of nitrites of soda & potash from the
nitrates of the same by the use of sulphur & caustic soda or potash.
The method of carrying this invention into effect is by heating the nitrates with
the caustic alkali, & adding sulphur gradually to the melted mass.
As an example of the production of nitrite of soda from nitrate of soda, I take
say 100 lbs. of nitrate of soda, of say 4 per cent. impurity & melt it in an iron pan
with about 50 lbs. of solid caustic soda of 70 per cent. strength, & heat the
mixture to such a temperature, that the sulphur when added does not deflagrate,
& then add, about 14 lbs. of flowers of sulphur gradually, & stirring all the time.
The sulphur dissolves quickly & the nitrate becomes reduced to nitrite.
When all the sulphur has been added the melt becomes thicker, & to complete
the reaction, I raise the temperature until the melt becomes thinner & eventually
clear.
By withdrawing samples from time to time from the melt, & applying the usual
tests to show that the quantity of uitrite formed does not increase the end of the
reaction is easily indicated.
The purification of the nitrite & separation from the sulphate of soda formed at
the same time, can be effected by fractional crystallization.
About chemically equivalent proportions of nitrate of potash, & of caustic.
potash can be substituted for the nitrate of soda & caustic soda given in the above
example.
Dated this 2nd day of March 1896.
COMPLETE SPECIFICATION.
Improvements in the Manufacture of Nitrites of Soda and Potash.
LEWIS GORDON PAUL 123 Palace Road, Tulse Hill, London S.W. Manu-
facturing Chemist do hereby declare the nature of this invention and in what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement:-
This invention relates to the manufacture of nitrites of soda and potash from the
nitrates of the same by the use of sulphur and caustic soda or potash.
The method of carrying this invention into effect is by heating the nitrates with
the caustic alkali and adding sulphur gradually to the melted mass.
As an example of the production of nitrite of soda from nitrate of soda, I take
say 100 lbs., of commercial nitrate of soda, and melt it in a cast iron pan with
Price 8d.1

page_text: 40 lbs. of solid caustic soda (containing 70 % Na,O) and then gradually add
14 lbs. of flowers of sulphur to the melted mass, stirring vigorously the whole
time.
The temperature should be maintained at such a degree that the sulphur does
not burn when added to the melt.
I find that a temperature ranging hetween 240 to 250 deg. C., is very suitable
for the reaction.
The sulphur dissolves quickly and the nitrate becomes reduced to nitrite.
When all the sulphur has been added the temperature of the melt is raised and
the agitation stopped.
The heating is continued until the melt begins to froth, when the agitation is
renewed and continued until the surface of the melt is free from froth, the
increased temperature being maintained.
When the froth has subsided the melt becomes thinner and clearer and can be
removed from the pan.
In order to avoid the violent reaction which takes place on the addition of
sulphur to the melt, when too large a percentage of caustic soda is present, I find
it more convenient to add the requisite quantity of the latter in several separate
portions.
Thus, using the same proportions as in the foregoing example, to the 100 lbs. of
nitrate of soda I add only 16 lbs. of caustic soda and then 5 lbs. of sulphur. The
remaining amount of caustic soda (24 lbs.) is then added in 3 further portions of
eight pounds each, 3 lbs., of sulphur being added after each of the three portions of
caustic soda.
The addition of the sulphur is made in the same way and under the same
conditions as mentioned above.
By this modification the reaction proceeds much more smoothly.
The purification of the nitrite and separation from the sulphate of soda produced
at the same time can be effected by fractional crystallization.
About chemically equivalent proportions of nitrate of potash and of caustic
potash can be substituted for the nitrate of soda and caustic soda given in the
above example.
I am aware that sulphides have been suggested for the transformation of nitrates
into nitrites and that they will transform a certain proportion, but, I have not been
able to transform a beneficial quantity by their use and I do not claim the making
of nitrite from nitrate by the use of such sulphides when separately prepared and
afterwards used for the reduction of nitrate to nitrite.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
The melting together of nitrate of soda or potash with caustic soda or potash
and the addition of sulphur to the melt for the production of nitrite of soda or
potash as described.
Dated this 26th day of November 1896.
L. GORDON PAUL.