Improvements in Methods of Securing the Chemical Stability of Nitro-compounds.
Year: 1893

page_text: Date of Application, 22nd Nov., 1893-Accepted, 23rd Dec., 1893
COMPLETE SPECIFICATION.
Improvements in Methods of Securing the Chemical Stability of
Nitro-compounds.
I, ROBERT CHARLES SCHÜPPHAUS of 118 Pennsylvania Avenue Brooklyn
County of Kings State of New York United States 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:-
This invention relates to a method of preventing the decomposition or of securing
the chemical stability of nitro-compounds, it being a well known fact that such
compounds when stored for a long period of time often undergo decomposition
which, slight at first, gradually increases until the whole compound has become
more or less decomposed and otherwise chemically changed.
The nitrates of polyatomic alcohols such as glycerine and mannite and of related
compounds as the carbohydrates, for example starch, cellulose and the like, are
especially susceptible to decomposition unless they are produced in an absolutely
pure state, which is seldom the case in manufacturing these compounds for
commercial use; and whenever traces of acid or of impurities of an unstable
character remain in the finished product, decomposition always occurs after the
lapse of a more or less short period of time. To prevent this decomposition in the
finished product of nitro-compounds, various means have been devised and employed
as in the manufacture of gun cotton or nitro-cellulose, it is not unusual to
incorporate a small quantity of an alkaline substance, such as silicate of soda, to the
compound in course of its manufacture to prevent its decomposition; and in the
manufacture of dynamite it is not unusual to add carbonate of lime or magnesia for
the same purpose; and in the manufacture of pyralin, celluloid, zylonite and similar
compounds of pyroxylin and camphor, carbonate of magnesia is frequently added
during the process of manufacture. In preparing high explosives diphenylamine
and aniline are employed to prevent decomposition of such explosives and as they
are capable of complete combustion they increase the volume of gases produced and
moreover leave no residue. In addition to the fact that these compounds with
nitrous acid, which is a constant product of the decomposition of these nitro
derivatives, are themselves unstable in character, their introduction in many cases
is inadmissible because of the discoloration which they are apt to produce, as, for
instance, in making transparent celluloid. All of the above mentioned difficulties
and many others are overcome by the use of urea or carbamide as a neutralizer,
which substance is an effectual neutralizer of impurities in nitro-compounds and
absolutely prevents their decomposition.
In practicing the process the nitro-compounds are freed as far as possible from
all adherent acids by repeated washings, and they are subsequently dried, if
necessary, after which I add the urea in suitable proportions according to the
quantity of nitro-compound and the purpose for which the finished product is
intended to be used, the urea itself being dissolved in a stable menstruum or flux
compatible with the solvents employed in the respective manufactures of nitro-
compounds which solvents are usually methyl or ethyl alcohol. As above stated
the quantity of urea which is mixed with the compound is regulated by the
conditions above mentioned and varies from one-half per cent. (per cent.) to
two per cent. (2 per cent.). This solution of urea and solvent penetrates every
particle of the nitro-compounds and neutralizes any acids or other impurities that
may be present whilst the surplus or excess remains evenly distributed throughout
the whole mass. The complete neutralization thus attained is an absolute safe-
guard against decomposition, but should, however, any part of the mass be subjected
to disturbing influences or any character and decomposition set in the additional

page_text: quantity or surplus of the "neutralizer," which, as stated, remains evenly distributed
throughout the whole mass counteracts this incipient decomposition and prevents its
spreading. The acids which have to be neutralized in such compounds are sulphuric;
nitric and nitrous acids which may be found in faint traces in the adherent wash-
water. As the nitrate and sulphate of urea are perfectly stable and colorless
substances the product resulting from its use with nitro-compounds becomes absolutely
stable, and no discoloration whatever occurs as with the use of the substances
heretofore added to prevent the decomposition of the nitro-compounds as above
mentioned. Furthermore, as nitrous acid reacts with urea in a remarkable manner,
yielding carbonic acid, nitrogen and water, any nitrous acid that may be present or
become generated during the process of manufacture is thereby rendered absolutely
harmless. As urea requires a minimum of oxygen to effect complete combustion it is a
perfect neutralizer in the manufacture of high explosives and owing to its low
molecular weight a smaller quantity will neutralize a given amount of free acid than
any other organic base heretofore used for the same or similar purposes.
I do not limit myself to the quantity of urea or carbamide which may be
introduced into the nitro-compounds for the purpose above stated, since as above
mentioned the quantity of urea will vary according to the character of the nitro-
compound and the purposes for which the resulting product is to be used.
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 :-
First. The process of securing the chemical stability of nitro-compounds which
consists in adding to such compounds a suitable quantity of carbamide or urea,
substantially as and for the purpose set forth.
Second. The process of securing the chemical stability of nitro-compounds
which consists in freeing such compounds from adherent acids as far as practicable,
and then adding thereto a quantity of carbamide or urea, substantially as and for
the purpose set forth.
Third. As a new product of manufacture or composition of matter the compound
of nitrated substances and carbamide or urea.
Dated this 92nd day of Novembar 1902
GEO. H. RAYNER,
37, Chancery Lane, London, W.C., Agent for the Applicant.