Improvements relating to the Extraction of Nitro-glycerine from the Waste Acid Formed in the Manufacture of Nitro-glycerine.
Year: 1892

page_text: COMPLETE SPECIFICATION.
Improvements relating to the Extraction of Nitro-glycerine from the
Waste Acid Formed in the Manufacture of Nitro-glycerine.
1, JAMES LAWRENCE, of Paulsboro, in the County of Gloucester, State of New
Jersey, United States of America 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 :-
In the process of manufacturing nitro-glycerine, the glycerine is mixed with
nitric and sulphuric acid whereby there is formed nitro-glycerine. The nitro-
glycerine formed is then separated from the waste acids, and this may be
accomplished in several well known ways, one of which is to allow the acid to pass
out the bottom of the tank or vessel, until practically all of said acid is removed,
leaving the nitro-glycerine in the tank for subsequent treatment in the ordinary
manner. It has been well known that this waste acid which is carried away from
the nitro-glycerine tank contains a certain amount of glycerine which has not been
acted upon by the nitric acid in the said tank, and also a certain amount of nitric
acid. Prior to my discovery, the waste acid was treated only for the recovery of
the acids. I have discovered that by cooling this waste acid to a certain tem-
perature, a reaction takes place between the glycerine and the nitric acid in the
waste acid,, whereby there is produced from the waste acids a certain amount of
nitro-glycerine dependent upon the amount of nitric acid and glycerine therein. I
carry out this process preferably in the following manner:
The waste acids from the nitro-glycerine vat are run into a lead tank, having a
lead pipe coil inside, through which cold water is drawn by means of a small pump
driven by compressed air or steam. The tank is protected on the outside with a
jacket of mineral wool cased in wood and has a lid of wood dipped in hot paraffin
wax. The temperature of the entering acid is usually from 50 to 65 degrees Fahr.
The temperature of the cooling agent should be as low or lower than the freezing
point of nitro-glycerine, and higher than the freezing point of the acids. Nitro-
glycerine freezes or solidifies at or about forty-five degrees Fahr. while the waste
acid freezes at about thirty-five degrees. So that the temperature to which I
reduce this mixture of glycerine and waste acids is between thirty-five and forty-
five degrees F. preferably between thirty-nine and forty one as this has given the
best results.
By this treatment of the waste acids I have discovered that the nitric acid in the
waste acids becomes active, combining with the glycerine, forming nitro-glycerine,
which rises to the surface, and can be removed. This refrigeration should be
continued for a considerable period with occasional agitation, as the process is slow.
I have found in practice that from three to four days are necessary to carry out
the operation successfully although if the product desired be less or the percentage.
recovered be less, of course the time may be proportionately reduced. Each day
the nitro-glycerine collected on the surface is taken out and placed in a wooden
tank containing water at sixty-five degrees F. from which it is drawn off to be
treated with alkaline solution in the ordinary manner. By my process for a given
quantity of glycerine I can increase the ultimate yield from six to nine per cent. If
desired sulphuric acid may be added to the waste acid before or during the cooling
of the waste acid as the yield of nitro-glycerine may be increased thereby.
The above is the preferred method of carrying out my process, but the process
may be carried out in any suitable vessel surrounded by ice water and the acids
may be stirred by means of paddles driven by hand or by power. Again a
refrigerating machine may be used to cool the acids, but in all cases care should be
taken that the acids are not cooled to the freezing point. As a rule they should be

page_text: cooled to within four degrees of their freezing point and about five degrees F. below
the freezing point of nitro-glycerine.
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 :-
1. The hereinbefore described method of producing nitro-glycerine from waste
acids and recovering the same, which consists in cooling the waste acids from the
nitro-glycerine tank to a temperature below the freezing point of nitro-glycerine
and above the freezing point of the acids.
2. The hereinbefore described method of producing nitro-glycerine from waste
acids and recovering the same, which consists in cooling the waste acids from the
nitro-glycerine tank to a temperature below the freezing point of nitro-glycerine
and above the freezing point of the acids and agitating said acids during said
cooling.
3. The hereinbefore described method of producing nitro-glycerine from waste
acids and recovering the same, which consists in adding sulphuric acid to the waste
acids from the nitro-glycerine tank, and cooling the same to a temperature below
the freezing point of nitro-glycerine and above the freezing point of the acids.
Dated this 97th day of April 1849
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.