Preparation of Ammonium Chromates and of Explosive Compounds.
Year: 1894

page_text: Date of Application, 16th Oct., 1894-Accepted, 9th Feb., 1895
[Communicated from abroad by THE UNITED STATES SMOKELESS POWDER Co.,
a corporation, of No. 13, Pine Street, in the City and County of San
Francisco, State of California, U.S.A.]
Preparation of Ammonium Chromates and of Explosive Compounds.
I, VICTOR ISIDORE FEENY, of 60 Queen Victoria Street, in the City and
County of London, Chartered Patent Agent 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 an improved process for the preparation of ammonium
chromates and their union with other substances. It consists in forming a solution
of ammonium picrate and potassium chromate or bi-chromate so that a transposition
of the elements takes place and new compounds are formed within the solution.
It is especially useful in the preparation of chromate or bi-chromate of ammonia,
and in the formation of explosive compounds in which these substances are used.
In carrying out this invention a solution of ammonium pierate is made, and to this
solution is added a solution of potassium chromate or bi-chromate.
When these solutions are thus united a transposition takes place which forms
potassium picrate and ammonium chromate or bi-chromate, and if an excess of
ammonium picrate is used there will also remain this excess of ammonium picrate.
If it is desired to produce the chromate or bi-chromate of ammonia, a sufficient
proportion of the mixture of ammonium picrate is employed to provide the
necessary amount for the transposition which takes place in the solution without
Jeaving any excess.
The transposition which takes place is expressed in the following equations, the
first relating to the formation of the bi-chromate and the second to the formation
of the chromate
==
2 CH. (NO), ONH₁ + K₂Cr₂O, = 2 C¸H₂ (NO₂), OK + (NH₁)₂ Cг₂O₂
2 CH (NO)3 ONH. + K.CгO. = 2 C¸H, (NO,) 3 OK + (NH₂), Cro
The potassium picrate thus formed will separate in fine crystals as it is quite
insoluble in cold water, and the ammonia chromate or bi-chromate will remain in
solution.
The crystals of potassium picrate will thus be precipitated to the bottom and may
be separated leaving the ammonium chromate or bi-chromate.
The ammonium chromate solution is then evaporated to dryness.
This process reduces considerably the cost of producing the ammonium chromates,
and is a very efficient and convenient method for so doing. When it is desired to
manufacture an explosive compound, the solution of ammonium picrate is employed,
making such an excess over what is necessary to produce the potassium picrate,
and ammonium chromate or bi-chromate as to provide for the proper proportion of
ammonium picrate which remains in the solution with the ammonium chromate or
bi-chromate.
A suitable proportion for an explosive may be as follows:-
Fourteen parts by weight of bi-chromate of potassium is dissolved in the least
possible quantity of water, and to this added eighty-six parts by weight of
picrate of ammonia, and then dried to a powder by hot air. By the transposition
which takes place, the following is the result:-Twelve parts of bi-chromate of
ammonia, twenty-five parts of picrate of potassium and sixty-three parts of picrate

page_text: of ammonia. The mixture is then evaporated until dry, the exact proportion of
the salts necessary for the explosive compound having first been arrived at by
mixing the proper proportion of the original ingredients, and if there be an excess
of potassium picrate this may be removed previous to evaporation. The solution
being then evaporated to dryness, the powder is completed with but little trouble.
Having now particularly described and ascertained the nature of this said inven-
tion and in what manner the same is to be performed I declare that what I
claim is :-
1st. The process of preparing ammonium chromates consisting in mixing a
solution of ammonium picrate and a solution of potassium chromate or bi-chromate
together, and afterwards separating the ammonium chromate or bi-chromate
solution from the precipitated crystals of potassium picrate, and evaporating the
ammonium chromate solution to dryness.
2nd. The method of preparing an explosive compound, consisting in making a
mixture of potassium bi-chromate and ammonium picrate in proper proportions, then
evaporating the resultant mixture of ammonium picrate, ammonium bi-chromate
and potassium picrate substantially as described.
Dated this Sixteenth day of October 1894.
For the Applicant,
GEDGE & FEENY,
Agents.