Process of Manufacturing Alkaline Bichromates
Year: 1895

page_text: Date of Application, 14th May, 1895-Accepted, 15th June, 1895
Process of Manufacturing Alkaline Bichromates.
I, MARC WAHRAM BEYLIKGY, Chemist, of Tenafly, in the County of Bergen
and State of New Jersey, United States of America, do hereby declare the nature
of my invention, and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement -
My invention particularly relates to the manufacture of the bichomates of
potash and soda and the object of my improvements is to provido a simple and
economical process of producing those bichiomates of a quality suitable for use in
the arts.
To this end I first produce a double chromate of lime and the alhalı, whether
soda o potash, to be bichromated, which I accomplish by roasting a mixture of
chione iron ore, lime and an oxygenated compound of the radical metal of the
alkalı, of proper proportions. For this purpose, having finely ground the chiome
ore and alkaline salt and intimately mixed them with lime, I preferably form the
mass into bricks, and then roust in any suitable form of furnace to which air may
be freely admitted.
The proper proportions of the materials to be employed will vary with the varying
percentages of sesquioxide of chromium in the chrome ore and of alkali in the salt
thereof used. In general terms mix them in such proportions that for every
molecule of sesquioxide of chromium, theto shall be present two atoms of the
alkaline metal and enough lime (either hydrate or carbonate) to form a normal
silicate of lime with such silicic acid as may enter the mixture from the chromne ore
aud alkaline salt and also one equivalent of lime extra to form in conjunction
with the sesquioxide of chromium and the alkali the double chromate desired
(R,CaCr,Og, in which R, may represent either potassium or sodium). In case
the acid in combination with the alkali is such as forms a stable compound with
Ime at high temperature (e.g. sulphate) the amount of lime that will thus enter
into combination must also be allowed for. To the aggregate amount of line thus
provided for, I preferably add not less than five per cent. of overdose in order to
accomplish fully and effectually the reactions, and facilitate the lixiviation.
The exact amount and proportions of the materials to be used in any given case
may be determined by check trials or may be readily calculated as will be well
understood by those skilled in the art.
In performing the roast the temperature should, in order to prevent loss of the
alkal, be first gradually raised to about the melting point of silver and so main-
tained for a time until the neutral chromate of the alkali under treatment is wholly
formed; it should then be raised to a bright orange and be kept at this point as
nearly as may be, until the reaction is completed. This is indicated first by the
reddish yellow color assumed by the mass and by its becoming agglutinated and
rendered compact or by some appropriate chemical test as when upon digesting the
roasted material simply and repeatedly with strong hydrochloric acid in great excess,
no blackish residue can be perceived. The roasting is then discontinued and the
resulting double chromate of lime and the alkalı under ticatment, which is readily
soluble in water, is separated from the other products of calcmation by lixiviation.
The next step of the process is the elimination of the lime from the solution thus
obtained so as to obtain in solution bichromate of potash or soda as the case may
be. This may be accomplished in various ways which will readily occur to those
skilled in the art. I have found that a desirable method is to treat the double

page_text: chromate solution with an insoluble fatty acid, such as ordinary commercial oleic
acid. For this purpose I may prepare a coarse filter of absorbent material, which
is proof against the action of diluted acids, such as ordinary cotton waste or woollen
flocks, oi, preferably, asbestos. This is impregnated with the fatty acid and the
double chromate solution is then allowed to pass slowly through it, so as to come
thoroughly into contact with the fatty acid in the filter. The lime constituent of
the double chromate combines with the fatty acid in preference to the alkaline
constituent forming a calcareous soap, which is insoluble in the accompanying
inenstruum, which consists of bichromate of the alkalı under treatment, dissolved,
which way then be drawn directly from the filter to evaporating pans or tanks and
concentrated to recover the bichiomate in solid for in
The soluble fatty acids while powerful enough to abstract from normal
chromates, the portion of basic element that tenders them neutral, unlike the other
acids will not go beyond this limit so as to set free any chromic acid, no matter
how largely they may be in excess, so that the line is neatly separated from the
bichromate formed without loss of the latter, and remains in the filter together with
any excess of fatty acid left unacted upon
After the bichromate solution is withdrawn from the filter, the filter is washed with
water to remove any adherent bichromate and then treated with diluto hydrochlouc
acid, which decomposes the calcareous soap forming a soluble calcium chloride
which may then be washed out with free affusion of water, the fatty acid being
thus regenerated and remaining in the filter by virtue of the capillary attraction of
the fibrous substances composing it. The filter is then ready for the passage of the
next batch of lixiviate
The calcium chloride solution produced may be allowed to run to waste, or, in
case sulphurie neid can be obtained more cheaply than hydrochloric acid, it may be
collected in tanks and treated with sulphuric neid rather less in amount than would
be required for the entire decomposition of the calcium chloride
Upon this treatment the lime removed from the filtering apparatus will subside
in the form of very sparingly soluble calcium sulphate and leave the hydrochlone
acid in its original state of activity, ready to be again used in the removal of lime.
The words alkali" and "alkaline" a used herem do not refer to the lime
employed, but include only that alkali whether potash or soda, the bichromate of
which is to be formed
Any of the oxygenated compounds of potassium or sodium may be used for the
purpose hereinbefore specified. I prefer, however, on account of their cheapuess
to use either a potash oi soda feldspar or the sulphate of potash or soda as the case
may be. Where a feldspar is need' in which both potash and soda occur the two
bichromates may be produced at one operation, since the bichromate of soda on
account of its greater solubility, will remain in solution after the bichiomate of
potash is crystallized out and may be' recovered separately by further evaporation
of the mother liquor of crystallization
The advantages of my invention will be readily apparent since by using a double
chiomate of lime and the alkali instead of a simple chromate as in the processes
Now in use. I enable the bichromate to be produced and recovered more neatly and
economically than has heretofore been possible. Thus low grade chrome ores can
be used as conveniently as those of high ginde; the alkali is derived from the
cheapest sources, no alkali auxiliary to the operation is wasted, the consumption
of sulphuric acid is reduced to a minimum; there is no chance of error in the
process of acidification, the bichromate is obtained pure in the first cystallization
and no part of the product is wasted in the mother liquor; advantages, the totality
of which is not presented by any process heretofore known.
Having now particularly described and ascertamed the nature of my said inven-
tion, and in what manuer the same is to be performed, I declare that what I
clain is
1. The herembefore described uocess of manufacturing the bichromates of notash

page_text: and soda which consists in roasting together chrome ore, lime and an oxygenated
compound of the radical metal of the alhal to be bichromated in such proportions
and at such a temperature as to produce a double chromate of lime and such alkalı,
separating such double chromate from the other products of the roast by lixiviation
and finally separating the line from the lixiviate thus obtained, thereby leaving the
bichromate of the alkali in solution.
2. The herein before described process of manufacturing the bichromates of potash
and soda which consists in roasting together, chrome ore, lime and an oxygenated
compound of the radical metal of the alkali to be bichromated in such proportious
and at such a temperature as to produce a double chromate of lime and such alkalı,
separating such double chromate from the other products of the roast by lixiviation,
separating the lime from the lixiviate thus obtamed, thereby leaving the desired
bichromate in solution and finally separating the bichi omate from such solution.
3. The process of manufacturing bichiomates of potash and soda which consists
in forming a solution of a double chromate of lime and the alkali to be
bichromated, eliminating the lime from such solution, thereby obtaining a solution
of the bichromate of such alkali and finally separating the bichromate from the
solution.
4. The hereinbefore described method of preparing a double chromate of lime
and an alkali which consists in roasting together a mixture of lime, chrome ore and
and an oxygenated compound of the radical metal of such alkali in proper
proportions and at a proper temperature, substantially as set forth.
5. The hereinbetore described method of eliminating the lime constitutent from
the double chromate of lime and the alkali through the agency of an insoluble
fatty acid, like the oleic, converting thereby, such double chromate neutral salts
into a bichromate of potash or soda, as the case may be.
6. Tho hercinbefore described process of manufacturing the bichromates of
potash and soda which consists in producing a double chromate of lime and the
alkali to be bichromated by calciuing a mixture of chrome iron ore, lime and an
oxygenated compound of the radical metal of such alkali; separating such double
chromate from the other products of elumiantion by lixiviation and finally treating
the lixiviate with an insoluble fatty acid so as to remove the lime and leave the
bichromate of the alkali in solution.
7. In the manufacture of alkaline bichromates the method of removing the lime
from a solution of a double chromate of lime and an alkah which consists in passing
the solution through a filter containing an insoluble fatty acid, thereby causing the
lime to combine with the acid so as to form a calcareous soap and drawing off the
resultant solution of bichromate of the alkali from the filter.
Dated to Lith dow of Mo 1805
F. WISE HOWORTII,
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicant.