IMPROVEMENTS IN THE MANUFACTURE OF ALCALINE OR OTHER BICHROMATES.
Year: 1860

page_text: LETTERS PATENT to Constant Pierre Eleonore Poussieur, of Paris, France,
Manufacturing Chemist, for the Invention of "IMPROVEMENTS IN THE
MANUFACTURE OF ALCALINE OR OTHER BICHROMATES.
Sealed the 7th February 1861, and dated the 18th August 1860.
PROVISIONAL SPECIFICATION left by the said Constant Pierre Eleonore
Poussieur at the Office of the Commissioners of Patents, with his Petition,
on the 13th August 1860.
I, CONSTANT PIERRE ELEONORE POUSSIER, of Paris, France, Manufacturing
Chemist, do hereby declare the nature of the said Invention for "IMPROVEMENTS
IN THE MANUFACTURE OF ALCALINE OR OTHER BICHROMATES," to be as follows:-
The Invention consists in treating oxide of chromium (whether mono or
bihydrated oxide, or even the anhydrous oxide, provided this latter has not
been previously submitted to calcination,) with an alcaline nitrate, such, for
instance, as the nitrates of potash, soda, lime,. magnesia, baryta, or other
similar suitable nitrates, either alone or in combination with a carbonate or
hydrate of the same basis, as that of the nitrate made use of or in treating a
neutral chromate according to the same principle, but with the addition of
nitric acid. The operation is performed in a reverberatory furnace, or in any
suitable vessel, and by means of suitable degrees of heat.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent
filed by the said Constant Pierre Eleonore Poussier in the Great Seal
Patent Office on the 13th February 1861.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, CONSTANT
PIERRE ELEONORE POUSSIER, of Paris, France, Manufacturing Chemist, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Thirteenth day of August, in the year of our Lord One
thousand eight hundred and sixty, in the twenty-fourth year of Her reign, did, for
Herself, Her heirs and successors, give and grant unto me, the said Constant
Pierre Eleonore Poussier, Her special licence that I, the said Constant Pierre
Eleonore Poussier, my executors, administrators, and assigns, or such others
as I, the said Constant Pierre Eleonore Poussier, my executors, adminis-
trators, and assigns, should at any time agree with, and no others, from time
to time and at all. times thereafter during the term therein expressed, should
and lawfully might make, use, exercise, and vend, within the United King-
dom of, Great Britain and Ireland, the Channel Islands, and Isle of Man, an
Invention for "IMPROVEMENTS IN THE MANUFACTURE OF ALCALINE OR OTHER
BICHROMATES," upon the 'condition (amongst others) that I, the said Constant
Pierre Eleonore Poussier, my executors or administrators, by an instru-
ment in writing under my, or their, or one of their hands and seals, should
particularly describe and ascertain the nature of the said Invention, and
in what manner the same was to be performed, and cause the 'same to be
filed in the Great Seal Patent Office within six calendar months next and
immediately after the date of the said Letters Patent.
2
NOW KNOW YE, that I, the said Constant Pierre Eleonore.Poussier, do
hereby declare the nature of my said Invention, and in what, manner the
same is to be performed, to be particularly described, and ascertained in.and
by the following statement :-
The Invention relates to certain new modes of treating oxides of chromium,
whether mono or bihydrated, or even the anhydrous oxide of chromium,
provided this latter, have not been previously submitted to a red hot calcination
or neutral chromates, with the object of obtaining alcaline or other bichromates,
such as the bichromates of potash, of soda, of ammonia, of lime, or others.
The Invention consists in treating the said oxides of chromium with a.suitable
pitrate, such, for instance, as the nitrates of potash, of soda, of lime, or others,
either alone or in conjunction with a carbonate or hydrate of the same bases;
or in treating a neutral cliromate according to the same principles, but with

page_text: the addition of nitric acid. Thus, for instance, for producing bichromate of
potash, I submit a suitable mixture of nitrate of potash and oxide of chromium,
either mono or bibydrated or even anhydrous oxide (provided this latter have
not already been submitted to a red heat) to a temperature. of from 300° to
350° centigrades, either in a reverberatory or 'other suitable furnace, in an
iron pot, boiler, or any other suitable apparatus.
The proportions of the nitrate and the oxide which gave me the best results
were to every 100 parts in weight of mono-hydrated oxide of chromium about
116 parts of nitrate of potash. After the nitrate of potash has been dissolved
in about half its weight of water the oxide is mixed therewith, after which by
a rapid evaporation the water is entirely driven off, and the mass or frit thus
obtained is kept at a degree of heat of from 300° to 350° C., till the same is
converted into bichromate of potash, the reaction beginning already before
the fusion takes place, and the same is terminated as soon as the mixture has
assumed a vivid red colour, when nearly the whole of the oxide of chromium
will be transformed into bichromate of potash; but should any notable
quantity of the oxide not have been transformed it would then be good to rise
the heat so as to melt the mass, and keep it in that state till nearly the entire
would be converted into bichromate of potash, which latter may then be
poured out on an enamelled plate of iron, or in a proper mould; in this case
it is desirable the fusing of the mass or frit should take place in an enamelled
iron.pot.or crucible, in order to prevent the apparatus from being corroded by
the acid fumes evolved during this operation; or the bichromate may be
dissolved in boiling water, and then submitted to crystallization without the
addition of any acid, the mother liquors serving further at each operation
for dissolving fresh quantities of bichromate to be crystallized. By adding
suitable quantities of carbonate of potash or of caustic potash to the above-
mentioned compound of nitrate of potash and oxide of 'chromium, the process
goes on with greater regularity and quickness, and the evolution of acid fumes
resulting for the decomposition of the nitrate is in great part prevented. I
thus, for instance, replace one-fourth part of the above-mentioned of nitrate of
potash by an equal weight of potash of commerce of an alcaline strength of
about 60 to 63 hundredth; in this case the conversion of the bichromate of
potash commences long before the melting of the dry materials takes place,
but in this case it is required for the crystallization of the bichromate to add
to its solution some nitric acid in order to form some nitrate of potash, which
remains in the mother liquor and is afterwards converted into bichromate of
potash by treating a proportionate quantity of hydrated oxide of chromium by
the above described process. This property of a mixture of nitrate of potash

page_text: and hydrated oxide of chromium of transforming directly into bichromate of
potash at a temperature not exceeding 400° C., I apply to the hitherto known
processes of manufacturing bichromate of potash, by which means those pro-
cesses become much more economical and are in general greatly improved.
But before describing this part of my Invention, and in order to make the
same better understood, and also in order to show the practical utility arising
from this improvement, I must mention here that in respect to the hitherto
known processes of manufacturing bichromates in general, and whatever
may be the salt of potash made use of; viz., either a nitrate, carbonate
or sulphate, or whatever may be the respective proportions of these salts in
their mixture with lime and the chromium mineral, at the temperature at
which it is required to work in the old processes, a neutral chromate is
constantly formed in the proportion of one equivalent of oxide of potassium
to one equivalent of chromic acid; now in order to transformi this neutral
chromate into a bichromate, it is requisite to deprive it of one half of its
base, which is done by treating with the required proportion of a suitable
acid or acids, sulphuric acid being the only mineral acid which. I have found
that may be advantageously made use of. But this mode of acting,as
will be easily understood, is very expensive, in as far as. oxide of potassium
being dear, having to bear in this, the entire expense of the production
of the bichromate, besides which, the quantity of bichromate obtained. is
less than that of the neutral chromate employed, so that whichever of. the
hitherto known processes might have been resorted to, every hundred pounds
neutral chromate operated upon, would yield only, and cannot possibly yield
more than about 75 pounds of bichromate of potash. It is obvious, therefore,
that if, instead of depriving the neutral chromate of one half of its oxide of
potassium for the purpose of converting the same into a bisalt, it were possible
to make the oxide-of this neutral chromate subservient for producing the
bichromate, a double- quantity of this latter would be obtained from the same
quantity of potash; this now. is the result to be obtained by my improvement,
by the aid of which 150 pounds of bichromate of potash may be obtained from
every 100 pounds of neutral chromate of potash acted upon according to the
method I will now fully describe. For this purpose, after having obtained a
solution of the neutral chromate of potash by any suitable process, and by the
aid of any suitable salt of potash, I. concentrate the solution to abont 30° or
32° Beaumé, and while hot throw into it by small portions at a time about
two-thirds of the quantity of nitric acid that would be required for fully satu-
rating the solution; the liquid is then left to settle for several hours, and after
baving become perfectly clear, the same is drawn. off from the sediment and

page_text: heated in a cast-iron pot, retort, or other suitable apparatus, with a quantity
of hydrated oxide of chromium equal to that contained in the solution of the
neutral chromate operated upon;. the strength of this latter having been ascer-
tained previously by means of a salt of lead. The liquid is now. evaporated
to dryness, diligently stirring in order to prevent the salt from adhering to the
bottom of the vessel. The reaction takes place in the same manner as when
using. the nitrate of potash alone, and commences long before the fusion of the
materials has taken place, and. is finished when the hydrated oxide of chro-
mium has nearly entirely disappeared. As soon as the dry mass assumes a
vivid red colour the conversion is finished, and the bichromate may further
be obtained either in the crystallized state, or be fused and run out on ena-
melled plates.or moulds in the. manner as was described above. But instead
of extracting at once the whole of the bichromate, I may after the addition.of
the nitric acid, crystallize out of the liquid only, that portion of the bichromate
of potash as results from the action of the nitric acid, aud which portion
consequently represents the amount of bichromate of potash as would have
been produced when acting.according to the hitherto known processes; and
treating now the mother liquor with a proportionate quantity of hydrated
oxide of chromium, I will obtain at the next operation, and by acting according
to my above described methods, a quantity of bichromate of potash equal to
that obtained at the first crystallization.
Bichromate of Soda.-Because of the great solubility of the bichromate of
soda and of the salts of soda in general, this bichromate has hitherto not been
produced on a, large or manufacturing scale, and in fact, whatever may be
the acid made use of for treating the neutral, chromate a salt is formed,
which remains mixed. with the bichromate of soda, the crystallisation of which
latter, even when pure, takes place with the utmost difficulty. The processes
above described for the manufacture of bichromate of potash are equally.appli-
cable to the production of bichromate of soda on a manufacturing scale. For
this purpose, I prefer taking about equal parts in weight of nitrate of soda and
monohydrated oxide of chromium, and I follow the same treatment as has been
above described,, for manufacturing bichromate of potash according to my
improved methods. The mixture of nitrate of soda and oxide of chromium
is maintained for 3 to 4 hours at a heat of from 300° to 350° C., in an iron
pot or other suitable vessel or apparatus, after which nearly the whole of the
mass will be converted into bichromate of soda, which I then dissolve in a
suitable quantity of water; in order to separate the extraneous matters. there-
from, and also the oxide of chromium, which would not have been converted
into bichromate; the liquid is left to stand till clear, and after having been

page_text: drawn off from the sediment the liquid.is evaporated to dryness in a cast-iron
pot or other suitable vessel; I thus obtain the bichromate of soda as a saline
powder, which may be employed in this state, but, which I prefer fusing at a
moderate and regulated heat and then pour out on enamelled plates, and thus
get the bichromate. of soda in the state of an amorphous, anhydrous, very
soluble and deliquescent. salt of a vivid red colour, and. which may replace
bichromate of potash in most operations in which this latter is employed.. In
the same manner as has been said in respect to bichromate of potash a solu-
tion of the neutral chromate of soda may be, treated, with a quantity of nitric
acid corresponding about with two-thirds of the quantity required for entirely
saturating the salt; I afterwards proceed with the hydrated oxide of chromium
in the same manner, as has been explained, for the manufacture of bichro-
mate of potash, taking care, however, as much as possible to prevent. the
mixture from fusing, unless I should wish to pour the mass on enamelled
plates, in order to obtain the salt in the amorphous state.
Bichromate of Ammonia. For obtaining this salt, by. my process, I begin
by forming-a neutral-chromate of lime or of barytes, to which I subsequently
add a proportional quantity of sulphate: or of bisulphate of ammonia, and keep
the solution in the boiling state during the time required for the decomposition
fully to take place; the escaping free ammonia is collected in a suitable
receiver, while the remaining liquid will contain the bichromate of ammonia
and is to be very carefully concentrated, so as to prevent any decomposition. of
the bichromate taking place. For a great many industrial purposes the
bichromate of ammonia may be used in this liquid state after having been
drawn off from the sediment, but if required the bichromate may be crystal-
lized out in the usual manner. All the soluble as well as the insoluble
bichromates, such, for instance, as those of barytes, of strontia, of magnesia, of
zinc, and those which resist a temperature of 250° to 350° may, by treating
them with their corresponding nitrates, be obtained as a saline powder
and sufficiently pure for, being usefully employed for industrial purposes, by
substituting their proportional weights for that of the nitrate of potash, and
operating further according to the above described improved processes.. Thus,
for instance, for producing bichromate of lime I take for every 100 parts, in
weight of nitrate of lime about 60 parts of monohydrated oxide of.chromium,
and further treat in the manner above described in respect to bichromate
of potash.. I must add here that instead of adding at once to the hydrated
oxide of chromium the nitrate of the basis, the bichromate of which is to be
produced, I may form-this nitrate by double decomposition in the solution, thus,
for instance, instead of taking the nitrate of potash I might take a mixture of

page_text: nitrate of lime and sulpfate of potash, which will when the operation is
effectuated at a suitable degree of heat give rise to nitrate of potash and sul-
pfate of lime, and thus produce a similar effect as if nitrate of potash had
been used at once.
I finally must observe that the above described processes for manufacturing
bichromates may also be made use of for the manufacture of neutral chromates
by suitably altering the relative proportions of the oxide of chromium and
of the nitrate made use of for this purpose; and the said neutral chromates
may by these methods be obtained in the same manner as has been said in
respect to the manufacture of the bichromates, viz., either in the state of solu-
tion, or in a crystallized or in the amorphous state and sufficiently pure for
being serviceable for industrial purposes.
And having now described the nature of my Invention, and the manner in
which the same may be put into practical effect, I declare that I do not intend
to restrict myself to the exact proportions given in the above Specification;
but what I claim as my Invention is, manufacturing bichromates of alcaline or
of earthy basis, such as the bichromates of potash, of soda, or others by
-treating,―
1ly, oxide of chromium, whether the mono or biyhdrated, or even the anhy-
drous oxide of chromium (provided this latter have not been previously
calcined to a red heat), with an alkaline nitrate or with a combination of salts
yielding such nitrate by double decomposition, the said alkaline nitrate being
caused to act on the oxide of chromium, either alone or conjointly with a
carbonate or a hydrate of the same basis as that of the alkaline nitrate.
Or, 2ly, by treating a neutral chromate in conjunction with nitric acid
with equivalent proportions of hydrated oxide of chromium.
In witness whereof, I, the said Constant Pierre Eleonore Poussier, have
hereunto set my hand and seal, this Ninth day of February, One
thousand eight hundred and sixty-one.
Witness,
A. G. BRADE.
C. P. E. POUSSIER. (L.s.)