IMPROVEMENTS IN THE PURIFICATION OF ALKALINE SOLUTIONS
Year: 1879

page_text: LETTERS PATENT to Eustace Carey, Holbrook Gaskell, the younger, and
Ferdinand Hurter, Ph.D., all of Widnes, in the County of Lancaster, Chemical
Manufacturers, for the Invention of "IMPROVEMENTS IN THE PURIFICATION OF
ALKALINE SOLUTIONS."
Sealed the 3rd October 1879, and dated the 18th July 1879.
PROVISIONAL SPECIFICATION left by the said Eustace Carey, Holbrook
Gaskell, and Ferdinand Hurter at the Office of the Commissioners of Patents
on the 18th July 1879.
EUSTACE CAREY, HOLBROOK GASKELL, the younger, and FERDINAND HURTER,
Ph.D., all of Widnes, in the County of Lancaster, Chemical Manufacturers.
"IMPROVEMENTS IN THE PURIFICATION OF ALKALINE SOLUTIONS."
Our Invention relates to the purification of alkaline solutions in order to effect
the destruction of the substances known as ferrocyanide of sodium and ferrocyanide
of potassium, or, in other words, the compound or compounds consisting of sodium
or potassium with cyanogen and iron, which may be contained in such alkaline
solutions.
In carrying out our Invention in order to effect this object we subject alkaline
solutions containing ferrocyanides to the action of atmospheric air, or to the action
of atmospheric air and carbonic acid, or we add to the alkaline solutions sulphur
or any compound containing sulphur, such, for example, as hyposulphites or poly-
sulphides, which will at an elevated temperature act in the required manner upon
the compounds of ferrocyanogen contained in the alkaline solutions, or any two or
more of the before mentioned decomposing agents may be employed in combination
if found desirable.
The solution thus prepared is next subjected to an elevated temperature, after
which the iron which has been precipitated may be separated by settling, filtration
or other convenient method.
In carrying this part of our Invention into effect we propose to employ apparatus
so constructed that the process of heating may be carried on continuously, the
solution constantly passing through the apparatus.
As a convenient method of accomplishing this result we propose to force the
solution through a boiler consisting of a coil or coils, or a chamber or passage or
passages heated upon the exterior by a furnace or otherwise, and arranged in such
a manner that the solution shall be caused to pass continuously along in one or
more streams so as to ensure that each and every portion of the solution shall be
heated to the required temperature.
J

page_text: .
SPECIFICATION_in_pursuance of the conditions of the Letters Patent filed by
the said Eustace Carey, Holbrook Gaskell, and Ferdinand Hurter in the Great
-Seal-Patent Office on the 17th January 1880.
EUSTACE CAREY, HOLBROOK GASKELL, the younger, and FERDINAND HURTER,
"Ph.D., all of Widnes, in the County of Lancaster, Chemical Manufacturers.
"IMPROVEMENTS IN THE PURIFICATION OF ALKALINE SOLUTIONS."
Our said Invention relates to the purification of alkaline solutions in order to
effect the destruction of the substances known as ferrocyanide of sodium and ferro-
cyanide of potassium, or, in other words, the compound or compounds consisting of
sodium or potassium with cyanogen and iron, which may be contained in such
alkaline solutions.
In carrying out our said Invention in order to effect this object we subject
alkaline solutions containing ferrocyanides to the action of carbonic acid, in con-
junction with atmospheric air or oxygen, or in lieu of atmospheric air or oxygen we
add to the to the alkaline solutions sulphur or any compound containing sulphur,
such, for example, as hyposulphites or polysulphides, which will at an elevated tempe-
rature act in the required manner upon the compounds of ferrocyanogen contained
in the alkaline solutions, or any two or more of the before mentioned decomposing
agents may be employed in combination if found desirable.
This preliminary treatment will vary according to the composition of the solution,
and in deciding on the kind of treatment the following points should be taken into
consideration:-
1. The ultimate object is the decomposition of the ferrocyanides by means of a
sulphur compound, which at an elevated temperature can part with some of its
sulphur; such sulphur compounds are the hyposulphites and the polysulphides; the
monosulphides are unsuitable for the purpose.
6
× 1
The quantities of such sulphur compounds should be at least five molecules of
hyposulphite for every molecule of ferrocyanide, or
molecule of polysulphide
containing atoms of sulphur for every one molecule of ferrocyanide contained in
the solution. Thus if a pentasulphide Na, S 5 be employed containing 5 atoms
1; one and a half molecules of pentasulphide are therefore
necessary for every molecule of ferrocyanide (Na, Fe Cys). The following equa-
tions represent the decompositions which take place in the second or final
operation :-
of sulphur
6
=
119
די
a 0

page_text: 2. The solutions which are afterwards to be exposed to an elevated temperature,
as hereinafter explained should not contain any appreciable amount of any sub-
stances which will form an insoluble deposit when exposed to an elevated tempe-
rature and pressure; such substances, which are chiefly silica and alumina, must be
removed by suitable means; we precipitate them by carbonic acid, and separate
them by settling or filtration, or other convenient method.
In carrying out our said Invention we usually perform the two operations of
oxydising and carbonating simultaneously by blowing or forcing into the alkaline
solution gas containing oxygen and carbonic acid, such as may be obtained from
the combustion of fuel, or from a lime kiln or other suitable source. We usually
employ the waste gases from a revolving black ash furnace, previously cooling these
gases if necessary. In the case of solutions we have usually to treat we find that
fuel gases containing about 10 to 13 % of carbonic acid and from 9 to 6% of
oxygen are the most suitable, but the proportion of carbonic acid and oxygen
required will depend upon the composition of the solution to be treated.
The solution thus prepared is next subjected to an elevated temperature, after
which the iron which has been precipitated may be separated by settling, filtration
or other convenient method.
In carrying this part of our Invention into effect we prefer to employ apparatus
so constructed that the process of heating may be caried on continuously, the
solution constantly passing through the apparatus.
As a convenient method of accomplishing this result we force the solution through
a coil or coils, or a chamber or passage or passages, heated upon the exterior by a
furnace or otherwise, and arranged in such a manner that the solution shall be
caused to pass continuously along in one or more streams so as to ensure that
each and every portion of the solution shall be heated to the required tempè-
rature.
The temperature required for the decomposition of the ferrocyanides varies again
with the sulphur compounds used, and is the lower the more atoms of sulphur the
compound contains in one molecule. The temperature is highest for the hypo-
sulphite, being about from 350° to 360° F. It is lowest for the pentasulphide,
where the decomposition takes place at about from 250° to 270° F.
The polysulphides are however usually not available, and we prefer to heat the
solution to between 350° and 360° F.
In order to prevent boiling of the solution in the apparatus the solution should
be kept under pressure, corresponding at least to the tension of steam at that
temperature, which is about 120 pounds to the square inch, but in order to make
absolutely certain that no evaporation may take place should the temperature rise
a little above 360° F., we prefer to keep the solution under a very much higher
pressure, usually varying from two hundred pounds to three hundred pounds per
square inch.
The accompanying Drawings represent one example of the varied forms of
apparatus which may be employed in carrying out this part of our said Invention.
Figure 1 represents a longitudinal vertical section of the apparatus; Figure 2 is
a plan of the same with the top arch removed; and Figure 3 is an end view with
the front wall removed.
The apparatus shewn in the Drawing consists of a triple ram pump A capable of
delivering the necessary quantity of liquid against a pressure or head of, say, three
hundred pounds to the square inch. This pump sends the liquid into the coil B, which
is arranged within a chamber C so as to be heated by a furnace D, the products of
combustion from which escape to a chimney at a. We prefer to employ one con-
tinuous coil of pipes, presenting sufficient heating surface to allow the liquid to
become heated to 350° F. in passing once through the entire length of pipes.
Between the pump and the entrance to this coil we place a pressure gauge E, and
either an "accumulator" or (as shewn in the Drawing) a safety valve F, or both,
to prevent fracture of apparatus in case of an accidental stoppage in the coil. We
prefer the coil to be arranged so that the liquid enters at the highest point, and

page_text: issues at the lowest, and we avoid as far as possible any upward movement of the
liquid, all with a view to sweep out solid particles, should any enter the tubes along
-with-the-liquid
At the outlet end we insert into the pipes a thermometer at G to indicate the
temperature of the liquid.
The pressure may be conveniently kept up by causing the solution to pass through
a valve or valves loaded to the necessary pressure. We find it advisable to fork
the exit pipe, as shewn at b, b, and to employ two such valves furnished with the
necessary stop cocks H, H, so that one may be repaired while the other is working,
I, I, being escape boxes for the liquid. In carrying out this process it is of
importance to avoid as far as possible the entrance of solid substances into the
coil, and it is well to filter the solution. Every attention should be paid to the
removal of silica and alumina from the solution, as these substances cause an
incrustation of the pipes. When working with soda solution care should also be
taken not to use the alkaline solutions in too concentrated a condition. The
solubility of carbonate of soda in water is less at 350° F. than at 220° F., and if
too concentrated a solution is introduced into the coil monohydrated carbonate of
soda will be deposited. Should any deposit in the pipes take place from this cause
it can be removed by passing water through the apparatus.
If the temperature is kept at 350° F., and sufficient sulphur compounds aro
present the whole of the ferrocyanides will be converted into sulphocyanides, and
the iron they contained will be held in suspension as sulphide or oxide of iron.
The solution should be freed from this precipitate by settling, filtration or other
convenient method, and is then ready for evaporation or crystallisation and the
production of white alkali or crystals.
Having now described and particularly ascertained the nature of our said Inven-
tion and the manner in which the same is or may be used or carried into effect, we
would observe in conclusion that what we consider to be novel and original, and
therefore claim as the Invention secured to us by the hereinbefore in part recited
Letters Patent is,―
The system or mode of purifying alkaline solutions by submitting the same to
the action of sulphur or sulphur compounds added to or produced in such alkaline
solutions, and of carbonic acid, the solutions thus treated being then subjected to an
elevated temperature in order that the iron which they contain may be separated
therefrom, substantially as herein before described.
In witness whereof, we, the said Eustace Carey, Holbrook Gaskell, the
younger, and Ferdinand Hurter, have to this our Specification set our hands
and seals, the Sixteenth day of January, One thousand eight hundred and
eighty
EUSTACE CAREY.
(L.S.)
(L.S.)
--HOLBROOK-GASKELL,-JUNIOR.--(L.S.)
FERDINAND HURTER.