IMPROVEMENTS IN THE MANUFACTURE OF CERTAIN SALTS OF SODA AND MAGNESIA
Year: 1846

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, PETER
WARD, of Oldbury, in the County of Worcester, Chemical Manufacturer,
send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Royal Letters Patent under the Great Seal of the United Kingdom of Great
Britain and Ireland, bearing date at Westminster, the Sixth day of July, in
the tenth year of Her reign, did, for Herself, Hei heirs and successors, give
and grant unto me, the said Peter Ward, my exors, adiñors, and assigns,
Her especial licence, full power, sole privilege and authonty, that I, the said
Peter Ward, my exors, admors, and assigns, or such others as I, the said
Peter Ward, my exors, adñors, or assigns, should at any time agree with,
and no others, from time to time and at all times during the term of years
therein expressed, should and lawfully might make, usc, exercise, and vend,
within England, Wales, and the Town of Berwick-upon-Tweed, my Inven-
tion of "IMPROVEMENTS IN THE MANUFACTURE OF CERTAIN SALTS OF SODA AND
MAGNESIA;" in which said Letters Patent is contained a proviso that I, the
said Peter Ward, shall cause a particular description of the nature of my said
Invention, and in what manner the same is to be performed, by an instru-
ment in writing under my hand and seal, to be inrolled in Her said Majesty's
High Court of Chancery within six calendar months next and immediately
after the date of the said in part recited Letters Patent, as in and by the same,
reference being thereunto had, will more fully and at large appear.
NOW KNOW YE, that in compliance with the said proviso, I, the
said Peter Waid, do hereby declare that the nature of my said Invention,

page_text: and the manner in which the same is to be performed, are fully described and
ascertained in and by the following statement thereof, that is to say.―
My Invention relates,―
Fust, to improvements in the manufacture of carbonate of soda. And,
Secondly, to improvements in the manufacture of Epsom salts.
And in order that my Invention may be fully understood, and readily carried
into effect, I will proceed to describe the means pursued by me.
It is well known to those engaged in the manufacture of soda ash that, after
the liquor or lyes from the black ash has been evaporated or salted down, that
the ash thus obtained contains a large quantity of caustic soda and sulphuret
of sodium. To render this ash into a fit state for making soda crystals, it is
desirable to convert the caustic soda into carbonate of soda, and the sulphuret
of sodium into sulphite or sulphate of soda, and for this purpose it is usual to mix
sawdust with the ash, either during the operation of salting it down in the furnace,
or after that it has been drawn therefrom, and previous to its being introduced
into the carbonating furnace. This mixture of ash and sawdust, when brought
into the carbonating furnace, is worked in the usual way, with a slow fire at
first, to burn off the sawdust, the fire is then increased sufficiently to commu-
nicate to the ash a red heat, and maintained until the ash is in a proper state
to be used for making crystals of soda. During this process I find that whilst
the sawdust is in a state of combustion the caustic soda and sulphuret of sodium
are fused and form small globules, which retard the process of carbonating, and
the conversion of the sulphuret of sodium into sulphite or sulphate of soda, it
is also a matter of experience that the caustic alkali dissolves a portion of the
sawdust or carbonaceous matter, and gives to the alkaline solutions a greenish
or dark color (that is, if the ash be drawn from the carbonating furnace before
the action of the file has fully removed the coloring matter). In consequence
of the difficulty experienced in getting rid of the coloring matter in the carbo-
nating surface it is usual to employ a solution of the chloride of lime in order
fully to remove this greenish or dark tiut from the alkaline liquors, previously
to making use of them in the manufacture of crystals of soda. In order to
obviate these difficulties which occur in the process just mentioned, and
to obtain a more perfect carbonate of soda, I take carbonate of magnesia in
the state of fine powder, in the proportion of from three to seven per cent.
of the dry ash, according to the quantity of caustic soda and sulphuret of
sodium which may be present in the ash operated on, and I mix this propor-
tion of such carbonate of magnesia with the alkaline liquors when they are
being boiled down to the state of ash in the salting-down furnace, or with the
asb after has been drawn from that furnace, and previously to its being intro-

page_text: duced into the carbonating furnace. The ash, thus mixed with the carbonate
of magnesia, is put into the ordinary carbonating furnace and submitted to the
usual treatment, for about three hours for seven hundredweight of ash
The advantages derived from the use of carbonate of magnesia in this
operation are twofold,―
In the first place, the carbonate of magnesia, being infusible at the greatest
temperature required in this operation, has the effect of keeping the mass of
ash in a porous and open state, thereby greatly facilitating the conversion
of the sulphuret of sodium into sulphite or sulphate of soda, and the caustic
soda into carbonate of soda.
In the second place, the carbonate of magnesia being subjected to a red
heat, as is the case in this process, gives out carbonic acid, which, uniting with
the caustic soda, forms carbonate of soda.
The ash when taken from the carbonating furnace is dissolved in water, the
magnesia subsides and carries down with it any oxide of iron that may be
present in the solution of the carbonate of soda, and leaves the liquor in a fit
state for making crystals of soda. If, on examination, the liquoi derived from
the ash be not clear and fiee from color, it shews that the ash did not remain
sufficiently long under the influence of the fire in the carbonating furnace to
produce the above effect. The magnesia, thus precipitated, is separated from
the liquor, and, after being washed with water to remove alkaline liquor fully
from it, is allowed to settle in a tank, and when taken from the tank it may be
dried and used to advantage in the same manner as the carbonate of magnesia
as above described in the manufacture of soda ash; or else it may be trans-
ferred into suitable vessels of stone or lead, where sulphuric acid and water
may be added in such proportions as will produce a saturated solution of
sulphate of magnesia of about the specific gravity 1165. I prefer making use
of sulphuric acid of the specific gravity of 1750, in order that it may, when
mixed with water, produce sufficient heat to dissolve readily the magnesia
The saturated solution of sulphate of magnesia, thus obtained, I pump into
another vessel, and add enough of sulphuret of magnesium to precipitate any
iron which is present in the state of sulphate of iron By this addition of
sulphuret of magnesium sulphuret of iron and sulphate of magnesia are formed.
Sulphuret of calcium may be used in this process to supply the place of the
sulphuret of magnesium. In this case, sulphuret of iron and sulphuret of lime
will be the salts formed. It is necessary to use the sulphuret of calcium cau-
tiously, for, should it be added in excess, it will decompose the sulphate of
magnesia.
.

page_text: sulphuiet of magnesium or calcium until a black precipitate ceases to take
place.
The sulphuret of calcium which may be made available in the foregoing
process I prepare from vat waste, an oxysulphuret of calcium produced during
the decomposition of the sulphate of soda in the manufacture of soda ash. It
may be obtained in a state fit for use by pouring hot water on the vat waste
and allowing it to remain about six hours in the vat, and then running it off
When the sulphuret of iron has subsided I draw off the clear liquor and
convey it into a leaden pan, and boil it until it acquires the usual specific
gravity; it is afterwards run into crystallizing vessels, and finished in the usual
manner. If, after the separation of the sulphuret of iron from the liquor, as
above mentioned, it is found to contain any coloring matter, derived from the
sulphuric acid or any other source, a clear liquor may be obtained by mixing a
small quantity of chloride of lime in solution to the liquor previous to boiling
it, preparatory to crystallization.
The sulphuret of magnesium I prepare as follows -I take sixty parts by
weight of the diy sulphate of magnesia, and forty parts by weight of coke finely
powdered, and, having introduced them into a common iron retoit, I subject
the retort to the action of fire until the whole mass shall have been maintained
at a red heat for about six hours. The contents of the retort are afterwards
taken out, and when cold dissolved in hot water. The liquor thus obtained,
being separated from the insoluble impunities, is then fit for use.
I would state that heretofore Epsom salts have been manufactured from
magnesian limestone, which requires to be calcined and washed in order to
separate the carbonato of magnesia, and I find that in some cases native car-
bonate of magnesia is found in a state of purity, or else so slightly mixed that
it may be considerd pure for the purposes of my Invention Now part of my
Invention consists in employing native carbonates of magnesia in the manu-
facture of Epsom salts without subjecting them to calcination and washing;
and the native carbonates of magnesia which I have employed have been lately
imported from Giecce, and when I employ native carbonate of magnesia,
without calcining and washing, for the manufacture of Epsom salts, I either
apply it, first, in the manufacture of carbonate of soda, as above explamed, or
else I put the native ore into a vessel and pour sulphuric acid upon it, and
then proceed to treat it in a manner similar to that used (as herein-before
described) for converting the magnesia, after its separation fiom-the soda ash
liquor, into Epsom salts or sulphate of magnesia.
Having thus described the nature of my Invention, and the best manner I
am acquainted with for performing the same, I would have it understood that

page_text: I do not confine myself to the precise details, so long as the peculiar character
of any part of my Invention be retained. But what I claim is,-
First, the application of magnesia, or its carbonates, in the manufacture of
carbonate of soda, as herein described.
Secondly, I claim the manufacture of Epsom salts by employing magnesia
after it has been used in the making of carbonate of soda.
I also claim the use of sulphurets of magnesium and calcium, to separate the
iron held in solution with the sulphate of magnesia.
And I also claim the use of native carbonates of magnesia, as herein
described, without first calcining and washing, when manufacturing Epson
salts.
In witness whereof, I, the said Peter Ward, have hereunto set my
hand and seal, this Fourth day of January, in the year of our Lord
One thousand eight hundred and forty-seven