IMPROVEMENTS IN THE MANUFACTURE OF CARBONATES AND BICARBONATES OF SODA AND POTARD
Year: 1866

page_text: LETTERS PATENT to George Lunge, of South Shields, in the County of
Durham, Doctor of Philosophy, for the Invention of "IMPROVEMENTS IN
THE MANUFACTURE OF CARBONATES AND BICARBONATES OF SODA AND POTARD"
PROVISIONAL SPECIFICATION left by the said George Lunge at the Office
of the Commissioners of Patents, with his Petition, on the 20th April
1866.
I, GEORGE LUNGE, of South Shields, in the County of Durham, Doctor of
Philosophy, do hereby declare the nature of the said Invention for "IMPROVE-
KENTS IN THE MANUFACTURE OF CARBONATES AND BICARBONATES OF SODA AND
POTASH," to be as follows:-
In order to effect the conversion of sulphate of soda into carbonate of soda a
solution of the former in which is suspended carbonate of baryta is submitted
to continued agitation by any of the well-known mechanical appliances suitable
for the purpose until the sulphate of soda is converted into bicarbonate, or
nearly so, by the absorption of carbonic acid from the carbonate of baryta.
The carbonic acid not so absorbed is conducted again through a similar
mixture, and from this or direct from the vessel in which the first mentioned
mixture is contained to the apparatus for recovering the carbonate of baryta, as
herein-after mentioned. When the conversion in the first vessel is sufficiently
complete the contents are run out, and the solution of bicarbonate of soda
separated from the insoluble residue, which consists mainly of sulphate of
baryta, both being then treated separately in the following manner :--

page_text: 'The solution containing bicarbonate of soda is either evaporated at a low
temperature in order to obtain bicarbonate of soda, or it is boiled down very
quickly in order to obtain on cooling the ordinary soda crystals, or it is boiled
down completely to dryness and heated in order to obtain soda ash. In
all cases the evaporating pans and drying furnaces can be so constructed as to
collect and economise the carbonic acid evolved during these processes, for
instance, by conveying it into a gasholder. The gases of the furnace fires
may also be utilized as a source of carbonic acid, but this acid may be derived
for the purposes of this. Invention from any source whatever. When from
the nature of its source it is too hot or too much charged with aqueous vapour
it may be freed from the latter by cooling and condensing it preferably in
an air condenser similar to that used in gasworks.
The precipitate separated from the solution of the bicarbonate of soda obtained
originally is treated in the following manner :-In order to recover the carbonate
of baryta, it is first dried and mixed with small coal or other suitable reducing
substances, and heated in a furnace until the sulphate of baryta is converted
into sulphide of barium, this part of the process being already well known.
The sulphide of barium may, however, be further converted into carbonate of
baryta by exposing it to the action of carbonic acid either in the solid state,
when the action of moisture or steam must be employed to assist the conversion
or preferably in solution. For this object the crude sulphide of barium from
the reducing furnace is treated with water, and the solution exposed to the
action of carbonic acid, until the sulphide of barium is completely converted
into carbonate of baryta and sulphuretted hydrogen. The former is employed
over again, and the latter is dealt with in the manner herein-after mentioned.
The carbonic acid requisite for this part of the process may be obtained from
the excess of carbonic acid which escapes from the vessels in which the mixture
of sulphate of soda and carbonate of baryta is acted upon. The sulphuretted
hydrogen generated in the above described process, together with the residuary
carbonic acid is treated in one or other of the three following methods:-
1. It may be conducted through one or more vessels similar to the dry
lime purifiers of gas works charged with oxide of iron or any other material
capable of retaining the sulphuretted hydrogen but not the carbonic acid. I pro-
pose preferably to use for this purpose the burnt iron pyrites which has passed
through the sulphurous acid kilns. The iron pyrites should be exposed to air
and moisture for some time, either in lumps or crushed, and the fine dust
generated during the process of exposure and containing much.hydrated oxide
of iron should be employed in the purifiers. The same treatment of burn
pyrites is available for the purposes of coal gas itself, but which of course form

page_text: no part of the present Invention. When the material has become inactive
it is roasted in a furnace (the absorbed sulphur being utilized as sulphurous
acid in the ordinary way) exposed to air and moisture and used over again.
2. The sulphuretted hydrogen may be brought into contact with the
impure liquid chloride of manganese, known as "still liquor," or "chlorine
residue" mixed with carbonate of lime. This mixture will absorb the
sulphuretted hydrogen, forming sulphides of manganese and iron, and give off
carbonic acid, which latter may be conveyed back to the general gasholder.
The residuary mass containing the sulphides of iron and manganese and free
sulphur may be roasted to make it quite inoffensive and to obtain part of the
sulphur in the shape of sulphurous acid. Ou lixiviation it will then yield
sulphate of manganese, which can be used for the same purpose as the
chloride.
3. Instead of "still liquor" a solution of perchloride of iron may be
employed in this process, the same being mixed with carbonate of lime, the
generated sulphide of iron containing free sulphur may be roasted, when most
or the whole of the sulphur will be recovered as sulphurous acid, while the
peroxide of iron remaining behind may be used again for obtaining perchloride
of iron.
The methods 1, 2, and 3 may be employed singly or in combination with
each other. The processes herein described may be carried on either by
forcing the gas through the liquid or mixture contained in a vessel, or by con-
ducting the gas through a structure or combination of materials in which the
liquids or mixtures will run down in the form of a fine rain, as well understood
by persons conversant with chemical manufactures. The several processes
herein-before described as being applicable to the treatment of salts of soda
apply in like manner to the salts of potash.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said George Lunge in the Great Seal Patent Office on the 20th
October 1866.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, GEORGE
LUNGE, of South Shields, in the County of Durham, Doctor of Philosophy,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twentieth day of April, in the year of our
Lord One thousand eight hundred and sixty-six, in the twenty-ninth year

page_text: of Her reign, did, for Herself, Her heirs and successors, give and grant
unto me, the said George Lunge, Her special licence that I, the said George
Lunge, my executors, administrators, and assigns, or such others as I, the
said George Lunge, my executors, administrators, 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 Kingdom of Great Britain and Ireland,
the Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN
THE MANUFACTURE OF CARBONATES AND BICARBONATES OF SODA AND POTASH," upon
the condition (amongst others) that I, the said George Lunge, my executors or
administrators, by an instrument 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.
NOW KNOW YE, that I, the said George Lunge, 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,
that is to say :-
My said Invention has for its object the manufacture of carbonates and
bicarbonates of soda and potash by treating the sulphates of these bases in an
aqueous solution with carbonate, or preferably bicarbonate of barytes (the
latter being continuously generated in the liquid itself), and whereby the car-
bonates and bicarbonates of soda and potash are more advantageously and
economically manufactured than by the methods and processes hitherto in use.
By the adoption of my said Invention, the bye-products resulting from the
processes employed are also utilized.
It may be here observed, that in many cases the conversion of sulphate of
soda into carbonate or bicarbonate of soda is herein-after alone referred to,
but the treatment so described is likewise applicable to the analogous salts of
potash.
For the purposes of my said Invention I effect the conversion of sulphate
of soda into carbonate by means of the action of carbonic acid on a solution
of sulphate of soda, wherein carbonate of barytes is suspended, and which is
kept in constant agitation until the conversion of sulphate of soda into bicar-
bonate is completed, or nearly so. The bicarbonate of soda is easily convertible
into carbonate, as will be well understood by persons conversant with chemical
operations. The chemical reactions which take place in the conversion of
sulphate of soda into bicarbonate are the following:-The carbonate of barytes

page_text: combines with a second equivalent of carbonic acid to form bicarbonate of
barytes, which latter salt being slightly soluble decomposes instantly with the
sulphate of soda existing in solution. The formation of bicarbonate of barytes,
though it is only temporary, is the principal condition of a complete decom-
position of the sulphate of soda, and the foundation of my whole Invention.
It is also necessary that the bicarbonate of barytes should be decomposed as
soon as formed to make room for a new quantity of it, because it is very slightly
soluble, and therefore I do not make it separately in order to mix the solution
with sulphate of soda (because in this case the solution is in too diluted a
state to be advantageously employed), but I make it in a solution of sulphate
of soda itself. The consequence is that every particle of bicarbonate of
barytes as soon as produced is removed from the liquid again, bicarbonate of
soda and sulphate of barytes being formed, the former remaining in solution,
and the latter constituting an insoluble precipitate. In this process no bicar-
bonate of barytes remains behind, and the liquid is accordingly ready again
to receive a new portion of bicarbonate of barytes, which is decomposed
instantly in the same manner as the first, and so on. The slight solubility of
the bicarbonate of barytes is of no importance, because a minimum of it only
need be in solution at any given time, as the reactions follow each other
closely, and it is removed from the liquid as soon as formed, so as to make
room for a new portion to be dissolved; much, therefore, depends upon the
rate at which the carbonic acid (employed as herein-after mentioned) acts on
the carbonate of barytes to convert it into bicarbonate, and it is found that
the action on native carbonate of barytes, even when the latter is very finely
ground, is very much slower than when an artificially prepared carbonate of
barytes is employed. In practise, therefore, though the reaction can be com-
pleted with native carbonate of barytes with, at the most, merely traces of
sulphate of soda remaining undecomposed, yet inasmuch as this requires a
considerable length of time, I prefer to use artificial carbonate of barytes pre-
pared in the manner herein-after mentioned as a bye-product of the process.
In the first place a solution of soda is made in a vessel constructed of wood,
iron, or any other suitable material, the same being provided with an appa-
ratus for stirring up the liquid, and which may be termed the "agitator," the
stirring apparatus employed being of any suitable character, as will be well
anderstood by persons conversant with such operations. The solution of
ulphate of soda is either made in the same vessel (which is then provided
with a steam pipe), or it is run into it from any other suitable vessel or
eceptacle. It is desirable that the solution should be nearly or completely
aturated at the working temperature. The "agitator" is provided with an

page_text: air-tight cover, with an aperture for introducing the carbonate of barytes, and
with inlet and outlet pipes for carbonic acid; the latter may, if preferred, be
placed in the sides of the "agitator." A convenient quantity of carbonate of
barytes is added, amounting at least to a chemical equivalent of the sulphate
of soda contained in the "agitator," if a complete conversion of the sulphate
of soda is desired, which will mostly be the case. For every seventy-one
parts of sulphate of soda contained in solution, apart from the impurities of
commercial "salt cake," there will be required ninety-eight parts of carbonate
of barytes computed in the dry state; when it is applied in the moist state, as
is generally advisable in my process, allowance must be made for the quantity
of moisture contained. The same proportion of ninety-eight parts of car-
bonate of barytes will apply to eighty-seven parts of sulphate of potash; a
small excess of carbonate of barytes will be found rather desirable. When
the charge has been introduced into the "agitator," which should not be filled
to the very top, a current of carbonic acid is transmitted through the liquid,
and at the same time the agitating gear is put in motion. It is advisable,
but not imperative, to multiply the jets of carbonic acid by providing the inlet
pipe with branches, coils, perforations, or the like contrivances, and even the
agitating shaft itself may contain the gas pipe, which may be connected with
it by a stuffing box, or the distribution of the gas from a single aperture may
be effected by means of the agitating gear. On the other hand, it is even
possible to dispense with the agitating gear altogether, and to cause the
agitation of the liquid by the stream of carbonic acid gas itself, which must in
such case be divided into many jets; at all events, there must be continued
agitation so as to keep the precipitate constantly suspended in the liquid and
exposed to the action of the carbonic acid; a large excess of the latter will
escape through the outlet pipe of the "agitator," and be treated as herein-
after mentioned. The temperature of the liquid may be the ordinary tom-
perature of the atmosphere, or it may be slightly elevated by means of steam,
or in any other suitable manner, but care should be taken that the tempera-
ture does not reach any high degree, because the action would be thereby
impeded. The time required for the completion of the conversion varies
according to the size of the apparatus and the concentration of the liquid, but
does not in any case exceed a few hours. It can be easily ascertained whether
the conversion is sufficiently complete; for instance, by drawing a sample
from a trial cock, allowing the solid matter to subside, sursaturating the clear
liquid with hydrochloric acid, and adding a few drops of a solution of chloride
of barium, the appearance or absence of a precipitate will shew whether it is
time to stop or not. In some cases it may be desired to stop before all the

page_text: sulphate of soda is decomposed, but in most cases it is advisable to wait until
no sulphate of soda, or only mere traces of it are found in the liquid. When
the desired point is attained the mixture contained in the "agitator" is run
out into a vessel suitable for settling, and the "agitator" may be immediately
charged with a fresh solution of sulphate of soda and carbonato of barytes, as
before described.
Instead of employing an "agitator," as before mentioned, in which some
pressure on the carbonic acid gas is unavoidable, an apparatus in which such
pressure is avoided may be used, similar to the "scrubbers" of gasworks, or
the condensing towers of alkali works, where the mixture of the solution of
sulphate of soda with carbonate of barytes flows down, while the carbonic acid
gas is caused to meet it by any suitable means, as well understood; but I
prefer the arrangements before described as being more manageable, and
because a certain pressure seems even advantageous for the working of the
process. As this pressure is only equal to the depth of the "agitator" it can
easily be overcome by means of a pump or similar or analogous apparatus.
If the process is to be applied to the conversion of sulphate of potash into
carbonate of potash, it is conducted in a perfectly similar way to the one just
described for soda, and the decomposition of the potash salt is found to take
place as readily and completely as that of the soda salt.
.
The carbonic acid gas employed in the process as before described may be
derived from any convenient source, as, for instance, from the decomposition
of limestone or chalk by acids, or from a lime kilo, or from a furnace in
which coal or coke is burned in a current of air, or from an apparatus in
which carbonate of lime, with or without coal, is heated in a jet of steam, or
from an ordinary furnace fire, or from a fermenting liquid, as will be well
understood by persons conversant with chemical operations and manufactures.
I propose especially to utilize all the carbonic acid evolved in the several
stages of my process, as will be herein-after described. In most cases a pump,
or similar or analogous apparatus, will be required to force the carbonic acid
through the "agitator" and the other apparatus; and in many respects it will
be found advantageous to collect it before using in a gasholder, in which
impurities can be deposited, or even to wash it with water in a "scrubber," or
washing tub, or any other of the well-known apparatus for washing gas. The
carbonic acid when evolved from its sources in too hot a state for using
directly, and when not sufficiently cooled in the gasholder or washing appa-
ratus (if such be employed) may be cooled in any simple way; for instance, in
the "syphon pipes," as used for cooling the gas for illuminating purposes.
I will now return to the treatment of the converted contents of the

page_text: 66
"
'agitator" which have been run into a "settler," where the precipitate can
settle down and the clear solution be separated from it. The solution will
now principally contain bicarbonate of soda, sometimes with a small quantity
of mono-carbonate of soda, besides the soluble impurities of the commercial
sulphate of soda employed, and which mostly consist of a small quantity of
common salt, but there will be no sulphate of soda, or only mere traces of it,
in solution, unless the decomposition has been stopped too soon.
The pre-
cipitate collecting in the "settler" consists chiefly of sulphate of barytes which
has been formed in the process, with whatever excess of carbonate of barytes
has been employed. If the carbonate of barytes has been sufficiently
pure, the resulting sulphate of barytes will be fit to be employed as the paint
called " permanent white
or "blanc fixé," or used for recovering carbonate
of barytes as herein-after mentioned. The solution which has been separated
from the precipitate in the "settler" is removed by a cock or syphon, or by
any other convenient method, as completely as possible, and carried into an
evaporating pan. The residue is washed with water to remove the adhering
part of the solution, and the washings may be run into the evaporating pan as
well; but it is better to employ them for dissolving a fresh quantity of
sulphate of soda for a similar purpose. The solution of bicarbonate of soda
which has been run into the evaporating pan may be treated in different ways
so as to give either commercial bicarbonate of soda, or commercial soda ash,
or soda crystals. In order to obtain bicarbonate of soda the solution must be
evaporated slowly at a temperature not exceeding one hundred and fifty degrees
of Fahrenheit's thermometer, until it yields a crop of salt on cooling. This salt
can be obtained in a finely divided state by cooling the liquid suddenly, or by
frequently stirring it, and is mostly found after it has been drained and dried
to equal the commercial bicarbonate of soda. If it should be found not to
contain quite a sufficient quantity of carbonic acid, it may be exposed to a
current of carbonic acid gas by means of any of the well known apparatus for
making bicarbonate of soda, but it will require at all events only a small
quantity of gas; or a current of carbonic acid gas may be transmitted through
the solution during the evaporating process. The salt may be obtained in a
still purer state by washing it with a moderate quantity of cold water sufficient
to dissolve the impurities, but leaving behind the great bulk of the bicarbonate.
The "mother liquor" separated from the salt may be further evaporated
slowly for the same purpose as before, or it may be employed for making soda
ash or crystals. If soda ash is to be manufactured the solution coming from
the "settler" is boiled down to dryness in the ordinary way, in pans, and
lastly, in furnaces; it gives off the second equivalent of carbonic acid in a

page_text: "
gaseous form, partly in the pan and partly in the furnace; and this gas
may be employed over again in the "agitator" or elsewhere. As for the
rest it does not matter in what kind of pans or furnaces the solution is
boiled down, provided it can be kept clean therein it will always yield a
remarkably pure soda ash, mostly even stronger than required for com-
mercial purposes; but it can easily be brought down to the commercial
strength by mixing it with common salt or sulphate of soda; or these salts
may be added in suitable proportions during the process of boiling down
in the pan or furnace. Soda ash may also be obtained from the solution
of bicarbonate, coming from the "settler by boiling it down as quickly as
possible to the required strength, when the excess of carbonic acid is mainly
evolved in boiling though never completely. If a current of air is transmitted
through the boiling liquid the removal of the carbonic acid is facilitated, and
the creation of a vacuum by condensing the vapours will also act in a similar
manner. At all events the crystallization must be carefully managed, because,
sesqui-carbonate of soda may crystallise among the ordinary soda crystals;
according to the degree of concentration and the more or less complete
removal of the second equivalent of carbonic acid; the two crystallisations will
take place one before the other, and when well watched can be separted by
removing the liquid after the first crystallization into another vessel where the
second crystallization can take place. In some cases it may be advantageous
to boil down the solution further than required for cystallizing, in order to
remove more carbonic acid, and then to add as much fresh water or weak
solution as required for a good crystallization. It need hardly be said that
soda crystals can readily be obtained from the dry soda ash, manufactured as.
described above, by dissolving and treating it in the way generally adopted in
chemical manufactories. If sulphate of potash has been employed in the
agitator" the resulting solution will contain bicarbonate of potash. From
this solution can be obtained solid bicarbonate of potash by treating it pre-
cisely in the same manner as described above for solid bicarbonate of soda,
and carbonate of potash will also be obtained from it in the same manner as
soda ash from the corresponding solution, namely, by boiling down to a suffi-;
cient state of dryness and heating until the second equivalent of carbonic acid
is given off.
CC
I will now proceed to describe the manufacture of artificial carbonate of
arytes to be used for the purposes of my said Invention, although I do not
claim such manufacture, except so far as it forms a part of the combination
of processes which are included in my Invention. For this purpose I employ
s raw material either finely ground native sulphate of barytes, or the artificial

page_text: product attained in my in my process and deposited in the "settler," as men-
tioned above. It has been before mentioned that this latter precipitate must
be washed to remove the solution of bicarbonate of soda; it is then dried; pre-
ferably by the waste heat from some of the furnaces of the manufactory. The
dried artificial precipitate, or the ground native sulphate of barytes, or a mixture
of both, is mixed with a suitable quantity of coal, either with or without the
addition of tar, oil, or other analogous carbonizing substances, and heated, for
instance, in a reverberatory furnace until the sulphate of barytes is sufficiently
reduced to sulphide of barium. It is unnecessary for me to give any further
particulars of this process because it is well known to every chemist, and
practised in several places. The reduced mass is lixiviated with warm water,
when the sulphide of barium is dissolved out; the residue will mostly contain
some unreduced sulphate of barytes, and may be employed over again for the
reducing process. The solution of sulphide of barium should not be so strong
as to solidify or to deposit many crystals on cooling. This solution is exposed
to the action of carbonic acid, which will decompose it in the following
manner-Carbonate of barytes will be thrown down as a precipitate, and
sulphuretted hydrogen will be evolved in a gaseous form. As a source of
carbonic acid for this part of the process I propose to use the gas which
escapes unabsorbed from the "agitator," and a great excess will always be
required. In my process, however, this part of the carbonic acid thus escaping
is not lost, as I employ it for the recovering of carbonate of barytes from
sulphide of barium. I conduct the gas so escaping from the "agitator"
"agitators," if there be more than one, through a pipe into an apparatus, in
which it acts on the sulphide of barium. This apparatus may greatly vary in
it may be, for instance, a closed tub containing the solution of sulphide
of barium, with an inlet pipe for carbonic acid, and an outlet pipe for sulphu-
retted hydrogen and the unabsorbed gases; in this case there will be some
means required to overcome the pressure of the liquid, as in the "agitator
itself. It is also convenient to provide such tubs with revolving stirrers to
distribute the gas better in the liquid. Instead of using such tubs similar to
the "agitator" described before, it is quite possible here to employ an appa-
ratus similar to a "scrubber" or condensing tower. This would be an erection
made of iron, bricks, stone, wood, or any other suitable material in the form of
a column or tower surmounted by a cistern, from which the solution of sulphide
of barium flows down, the carbonic acid being made to enter this tower, and
the residuary gas escaping through an outlet, either into a similar tower, or
when all but completely freed from carbonic acid into the place where the
sulphuretted hydrogen has to be further treated. In order to multiply the area
form;
or
19

page_text: of contact between the liquid and the gas, suitable shelves may be constructed
within the tower to break the flow of the liquid and to compel the gas to
make a circumambient road; or the towers may be filled with coke, bricks,
pebbles, or the like, but I do not prefer the latter way, as the interstices
between the pieces of coke or other substance employed are too easily filled
up with the precipitate of carbonate of barytes in course of formation. If the
towers are of sufficient height the flow of the solution of sulphide of barium
may be so regulated that it shall arrive at the bottom completely decomposed,
but if that is not the case it is pumped up again and run down again in the tower
until the decomposition is complete. Whether this be the case can be easily
ascertained by various reactions, for instance, by dipping a paper soaked with
a salt of lead into the liquid; so long as the paper is turned brown by the
liquid the action of carbonic acid has to be continued. When the decom-
position is finished, that is to say, when the whole of the barytes is precipitated
from the liquid as carbonate, the mixture is run into a suitable vessel, where
the precipitate may settle down. The supernatant liquid, which is nothing
but water, may be run away; but if the sulphide of barium from the
"agitator" has not been completely washed this supernatant liquid will
contain certain quantities of the salt of soda, and it may then be used up for
dissolving purposes and the like. The precipitate of carbonate of barytes
will be applicable immediately in the "agitator." Instead of carbonating the
sulphide of barium in solution it might be done also by exposing the solid
sulphide of barium in a damp state, with or without the introduction of steam
to the action of carbonic acid, and an apparatus with a row of shelves or
stages may be provided for this purpose to offer a great surface to the action
of the carbonic acid; but as it is difficult to insure the complete conversion
of the sulphide of barium into carbonate of barytes in this manner I prefer
effecting the carbonization in a solution of sulphide of barium. Everything
herein-before mentioned with regard to the recovery of carbonate of barytes
applies equally to the sulphate of barytes obtained in the decomposition of
potash, and to that obtained when sulphate of soda is treated, and the same
remark applies to the treatment of the sulphuretted hydrogen evolved during the
decomposition of sulphide of barium. The quantity of sulphuretted bydrogen
given off during the decomposition of sulphide of barium is very considerable,
and will be equivalent to the sulphate of soda or potash decomposed. Of
course this gas cannot be allowed to escape into the open air, but must be
absorbed, retained, or decomposed in some manner so as to become innocuous.
The gas may be made to pass through one or more arrangements of apparatus
constructed similarly to the "purifiers" of gasworks charged with several

page_text: layers of a material capable of absorbing sulphuretted bydrogen. It would be
preferable, but rarely advisable; in this instance, to fill these purifiers with
bydrated lime, for the spent lime is not only not fit for easily recovering the
sulphur therefrom, but it presents also a very unpleasant smell; it is therefore
preferable to use some other material more suitable for the purpose. A very
convenient material is the burnt pyrites which accumulates there, and which
consists principally of sesqui-oxide of iron. When exposed for some time to
the action of air and moisture the sesqui-oxide of iron is gradually hydrated
and the mass crumbles down to the state of a powder. It is then in a fit
state for being used in "purifiers" in order to absorb the sulphuretted
hydrogen evolved in my process, either by itself, or mixed with sawdust.
When it has lost its absorbing power for sulphuretted hydrogen it may be
exposed to the air, and it will thereby recover its activity again, the sulphide of
iron being wholly or partially oxidised. When there is a sufficient per-centage
of sulphur in the mass so that it has become unfit for further use in the
purifiers, it is roasted in a furnace similar to those used for burning sulphur
or pyrites, and the sulphurous acid evolved may be utilised in lead chambers
for the manufacture of sulphuric acid.
Another method which I propose is as follows:-A mixture is made of
carbonate of lime (chalk) and of the impure chlorides of manganese or iron
which remain in the stills used for generating chlorine gas, and which are
known as "still liquor" or "chlorine residue." The sulphuretted hydrogen
is brought into contact with this mixture (which requires to be kept in
constant agitation), and by which it will be absorbed, forming sulphides of
manganese and iron. The carbonic acid evolved need not be lost, but may be
employed in the first stage of my process. The mixture must be sufficiently
dilated with water to allow an easy passage of the gas. It may be contained
in one or more vats or tubs with covers, into which the gas enters at the
bottom, and after traversing the liquid escapes at the top; but unless the
contents of the vessels are kept in constant agitation the absorption will not be
complete. It is best to employ at least two such vats, and to arrange the inlet
and outlet pipes for the gas by means of valves, cocks, or other suitable con-
trivances in such a way that each of the vats can be made the first or the
second of the series. It is then easy to keep the contents of each vessel long
enough in it to utilise their absorbing power as much as possible, the first vat
always being the one which is already nearly saturated, the second the one
which has been charged at a later time, and the fresh contents of which are
fit for totally absorbing the sulphuretted hydrogen still escaping from the first
When the contents of the latter are completely saturated it is emptied,
vat.

page_text: filled with a fresh mixture again, and the way of the gas is now reversed, so
that this vat becomes the second. It is obvious that a similar arrangement
can be made if three or more vats are used.
Another plan is to employ "scrubbers" similar to those used in the recovery
of carbonate of barytes, in which a stream of the dilute "still liquor" and
chalk trickles down while the gas ascends in the tower. According to the
height of the columns more or fewer "scrubbers" will be required. When
the absorbing mixture has lost its efficacy it has to be replaced by a fresh
quantity. The spent mixture when allowed to settle, and after being freed
from the liquid part by draining, contains large quantities of the sulphides of
manganese and iron. This mass when roasted gives off part of the sulphur
as sulphurous acid, and the latter may be employed as commonly done in
lead chambers; the roasted residue will still retain part of the sulphur in the
shape of sulphate of manganese. As this compound acts for this purpose in
the same way as chloride of manganese or "still liquor," it may be used in
the place thereof in the process of absorbing the sulphuretted hydrogen by
stirring the residue in water, and adding a fresh quantity of chalk if the first
quantity should have been spent. Instead of "still liquor" a solution of
perchloride of iron may be employed in this process, the same being mixed
with carbonate of lime; the generated sulphide of iron containing free sulphur
may be roasted, when most or the whole of the sulphur is recovered as
sulphurous acid, while peroxide of iron remains behind, and may be used
again for obtaining perchloride of iron. All these methods as herein-before
indicated may be employed singly or in combination with each other. It will
be noticed that in my process the sulphur of the sulphate of soda or potash
originally employed is not lost, as in the ordinary process of soda manufacture,
but is turned to use over and over again.
Having thus fully declared and ascertained the nature of my said Inven-
tion, and the manner in which it is to be performed, I would observe in
conclusion that I do not claim the use of the several processes and details
of manufacture herein-before mentioned and described, except in connection
with my said Invention, neither do I limit or restrict myself to the precise
details herein-before set forth, as variations may be made therein without
departing from the principles or main features of my said Invention, and that
what I consider novel and original, and therefore claim as constituting the
Invention secured to me by the said herein-before in part recited Letters
Patent, are,
First, the conversion of the sulphates of soda and potash into the bi-
carbonates of those bases by conducting a stream of carbonic acid through a

page_text: mixture of a solution of the before-mentioned sulphates and carbonate of
barytes, by the methods and in the manner substantially herein-before set
forth and described, or any mere modifications thereof.
Secondly, the treatment of the solutions of bicarbonates of soda and potash
obtained in accordance with my said Invention, so as to yield either solid bi-
carbonates or crystals, or ash, in the manner substantially herein-before set
forth and described, or any mere modifications thereof.
Thirdly, the recovery of the carbonate of barytes from the sulphate of
barytes for the purposes of my said Invention, by the methods and in the
manner substantially herein-before set forth and described, or any mere
modifications thereof.
Fourthly, the absorption or decomposition of sulphuretted hydrogen evolved
in the performance of the before-mentioned processes, by the means and in
the manner substantially herein-before set forth and described.
And, fifthly, the renewed employment of the carbonic acid given off in the
aforesaid various processes, by the methods and in the manner substantially
herein-before set forth and described, or any mere modifications thereof.
In witness whereof, I, the said George Lunge, have hereunto set my
hand and seal, this Seventeenth day of October, in the year of our
Lord One thousand eight hundred and sixty-six.
Witness,
E. P. H. VAUGHAN,
.
54, Chancery Lane,
Agent for the Patentee.
GEORGE LUNGE. (L.S.)