IMPROVE- MENTS IN THE MANUFACTURE OF ALUM AND IN OBTAINING AMMONIA
Year: 1850

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JAMES
THOMSON WILSON, of Stratford-le-Bow, in the County of Middlesex, Chemist,
send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Royal Letters Patent under the Great Seal of Great Britain and Ireland, bearing
date at Westminster, the Seventh day of December (One thousand eight
hundred and fifty), in the fourteenth year of Her reign, did, for Herself, Her
heirs and successors, give and grant unto me, the said James Thomson
Wilson, my exors, adñiors, and assigns, Her especial licence, full power, sole
privilege and authority, that I, the said James Thomas Wilson, my exors,
adiñors, and assigns, or such others as I, the said James Thomson Wilson,
my exors, admors, 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, use, exercise, and vend, within England,
Wales, and the Town of Berwick-upon-Tweed, my Invention of "IMPROVE-
MENTS IN THE MANUFACTURE OF ALUM AND IN OBTAINING AMMONIA;" in which said
Letters Patent is contained a proviso that I, the said James Thomson
Wilson, shall cause a particular description of the nature of my said Invention,
and in what manner the same is to be performed, by an instrument 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

page_text: 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
James Thomson Wilson, do hereby declare that the nature of my said Inven-
tion, 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 :-
a very small
My improvements in the manufacture of alum relate to the mode in which
I obtain sulphate of alumina, and also to the conversion of sulphate of
alumina into alum. Hitherto in manufacturing alum directly by means of
sulphuric acid, there, have been,. so. far as I am aware, substantially only two
modes of operating. The first is, to employ at. one operation as much sul-
phuric aced as is necessary to combine with the whole available alumina of the
clay, shale, or other aluminous material which is employed, and when the
combination has been effected, separating the sulphate of alumina by repeated
washings, thereby so diluting the solutions as to require considerable evapora.
tion. This mode, though varied. in- details, has-been long in common use.
The second mode is, by adding the sulphuric acid in successive doses, to the
extent of six or seven times, obtaining.so. many successive crops of alum from
the same aluminous material without previous evaporation. This process was
patented by Mr: Spence, in One thousand eight hundred and forty-five. My
process is as follows:-I select a variety of shale which contains as little
iron, lime, or other soluble impurity as possible, and
portion of coaly matter. This material breaks down by exposure to
the weather' for 2 or 3 months into very small thin shivers, and in
this way
is obtained in the state. of fine division which is required for
economical working better than by grinding. When reduced to this state of
fine division I ignite it in kilns, similar to those used for lime; which permit a
continuous supply at the top and withdrawal at the bottom; the temperature is
more under control when burned in this way than in open heaps in the
manner of alum schist; and it is important to prevent it exceeding a low red
heat, otherwise the alumina is rendered less soluble. The coaly matter of
the shale, when once ignited; is sufficient to keep up the combustion. In
order to extract the alumina from the material thus prepared I use a vessel
which I prefer to be of the following construction; videlicet:-An
open boiler, as shewn in vertical section, which may be either round
or oblong, but which I consider best about five feet wide, four feet
deep, and 'fifteen feet or thereabouts in length, and made of malle-
able iron, smooth in the inside and lined with stout lead. At a distance of
fifteen or eighteen inches from the bottom (at a) a double or false. bottom is
placed, formed of lead of twenty-four pounds or thereabouts to the square foot,
a

page_text: and perforated closely with holes about quarter inch diameter. This false
bottom is supported by cross bars of iron covered with lead, resting on the
curved part of the sides of the boiler. A portion of this false bottom, eighteen
or twenty inches broad, is made moveable so as to allow the space below to be
examined and cleaned when needful. A different size or form of vessel may
be used, or a different material for the false bottom; but à false bottom so
placed as to permit the safe application of sufficient heat, and the thorough
drainage of the shale, is essentially necessary. When the boiler is placed in a
furnace so arranged that the flame cannot reach the false "bottom by several
inches it is then ready for use. In this vessel, upon the false bottom, I place
the prepared shale to the depth of twelve or fifteen inches, previously screening
out the larger pieces, and arranging them next the perforated bottom to pre-
vent the smaller shale passing through; I then add sulphuric acid in the
proportion of ten hundredweight of acid, specific gravity 1.845 for every
twelve hundredweight of shale, which is sufficient to extract the whole
available alumina from such as 'I-use (but the exact proportions depending on
the quality of the shale must be ascertained experiment), and add as much
water as will produce a specific gravity of 1.35 c. 14, and will fill to within'
six or eight inches of the top of the boiler, which is then covered up and kept
in a state of moderate ebullition for a period of forty-eight 'hours or thereabouts
(replacing occasionally any water lost by evaporation). At the end of this
period, in consequence of the quantity and great strength of the acid solution,
the high temperature, and the continual circulation of the liquors, the whole of
the available alumina is extracted from the shale, and the fire being with-
drawn the liquor is then run out, and although it is of great strength, yet in
consequence of the thorough drainage of the shale into the intermediate space
below the false bottom, only a very small portion adheres to it, and is suffi-'
ciently removed by being once washed through with mother liquors from the
rocking casks, or with water. This is run in with the previous strong. liquor'
to reduce its strength sufficiently for crystallizing when formed into "alum.
The shale is then thrown out, the space below cleaned out, and a new
charge introduced. Having thus thoroughly exhausted the shale of all its
available alumina at a single operation, and procured a solution of sul-
phate of alumina so strong as to require to be diluted with the washings
in order to be crystallized, 1 might convert it into alum by adding sul-
phate of potash or sulphate of ammonia in the usual way, but I have'
found that when alumina is dissolved out of shale by direct combination
with dilute sulphuric acid, a large quantity of acid remains in excess. This,
amounting to about twenty-five per cent. of the whole, when a sulphate
is added, remains in excess in the mother liquors after the alum has crystal-

page_text: lized, and is ultimately lost; and a portion of it is also retained by the alum
and renders it more troublesome to purify. To prevent this I continue the
process as follows:-I run the sulphate of alumina and washing together into
a vessel (lined with lead and heated by steam or otherwise) of considerably,
greater capacity than is necessary to contain them, and I then run the ammo-
niacal liquor as obtained from the gas works or other processes of destructive
distillation or combustion, or from any other source, or the said liquors pre-
viously distilled, or I condense therein the ammonical vapors in the process of
distillation, as may be convenient, in all which states the ammonia will combine
with the excess of acid in the liquors, and produce, when the proper quantity is
added, a solution of alum free from excess of acid. Enough ammonia is
added when a brown precipitate appears and does not readily re-dissolve; if
this should not be sufficient to combine with the whole sulphate of alumina
present (which will be the case where less than 25° remains in excess), sul-
phate can be then added instead of the ammonial liquor. When enough has
been added to convert the whole into a solution of alum (which is ascertained
by trial in the usual way), and evaporated, if needful, to the proper strength for
crystallizing, it is run out into the coolers, after allowing the impurities to
subside, and crystallized in the ordinary manner.
The mother liquors are,
when cold, pumped up and evaporated to about one
adjusting the proportions of acid, alumina, and ammonia, are again crystal-
lized; any liquors remaining over are now too. impure, and may be run to
waste or applied to any purpose for which they are available. I never allow
any mother liquors to be used as dilutents of acid, being convinced of their
being injurious when so employed.
third, and after carefully
I do not confine myself to matters of detail as here described, nor do 1
claim as my Invention all the particulars I have mentioned; what I claim is,-
First, the formation of sulphate of alumina by employing a sufficient
quantity of dilute sulphuric acid at a high temperature, and thereby
dissolving the whole available alumina of the shale operated upon at a single
operation.
Second, the use of the essential construction of boiler and arrangement of
materials therein as described, so as to allow the application of sufficient
heat to cause a thorough circulation of the liquors and a perfect drainage
of the shale, and thereby to obtain the sulphate of alumina without waste
of the materials employed.
Third, the conversion of sulphate of alumina into alum by adding ammonia
thereto in such a state that it shall combine with the excess of acid contained.
therein when obtained from shale, by directly dissolving the alumina thereof
in.dilute sulphuric acid.

page_text: The second part of my Invention relates to obtaining ammonia. It is
well known that this substance is formed not only in the destructive distillation
of coal in close vessels, as in the manufacture of coal gas, but also in cases of
ordinary combustion, where the air is freely admitted, as well as in other
processes where the air has more limited access, as in coke ovens. In such
cases hitherto, however, except that deposited in soot, the ammonia thus formed
has been allowed to pass into the atmosphere along with the other products of
combustion. The object of my Invention is to obtain this ammonia, where
such processes are carried on on the large scale, by separating it from the
other gaseous products before they are discharged into the atmosphere. This
can be done to some extent by simply cooling them, when the ammonia is
partially condensed along with the moisture, as in 'coal gas.
But the cooling
apparatus requires to be so large, and the liquor is so weak, while the cooling
destroys the draft of the chimney, that this mode is unadvisable. I, therefore,
collect the ammonia directly by bringing it into contact with some substance
which shall absorb it readily, even at a high temperature. The best substance
for this purpose is sulphuric acid, and the apparatus I use for collecting the
ammonia thereby is a modification of one frequently used in washing coal gas,
that is to say, a hollow column filled with coke or, preferably, large rounded
pebbles, through which the gas is made to pass upwards, while the condensing
liquor is made to trickle downwards, so as to keep the materials in the interior
continually moist. I prefer this apparatus, as it affords sufficient surface for
condensing the ammonia without obstructing the draft of the chimney. In
arranging it for this purpose, it is needful that the area of the cross section
shall be at least five or six times that of a chimney sufficient to give draft to
the ovens or furnaces, and twelve or fifteen feet high, and that the interior of
the column, if constructed of iron, as well as the cisterns at top and bottom,
shall be lined with lead. If built of brick, the interior should be lined with
fire brick and clay, exposed to a strong heat before being used. A space of
three feet in depth should be left clear under the coke or pebbles, which can
be supported on cross bars. Into this space, and at such a distance from the
fire that the apparatus shall not be injured by the heat, the smoke or gaseous
products is introduced from the main flue leading from a series of coke ovens
or furnace or series of furnaces (or if in blast furnaces, when the inflammable
gases are inducted away for use, then these gases are so introduced). They
then pass upwards, and at the top pass out by a pipe or flue leading directly
into the chimney by which the draft is given. Into a cistern, placed under or
at the bottom of the column, sulphuric acid (only so diluted that the ammonia
salt formed may not be so strong as to crystallize in the interior of the column)
is placed, and forced up when needful into a cistern placed on the top, so

page_text: pierced in the bottom with very small holes or otherwise arranged that the
dilute acid may be evenly distributed over the upper surface,, so as to be con-
tinually, trickling downwards and keeping the materials moistened therewith.
To insure this, if the heat be strong, water must be added, from time to time,
as is found necessary. The liquor on descending is received into the lower
cistern, and thus the same charge of.,acid is caused to .circulate again and
again until neutralized, when it is run off, to be manufactured by filtration
and crystallization, and a new charge introduced. The soot which may be
deposited in the column will generally be carried down by the liquor. A more
copious, effusion, however, occasionally. will facilitate the clearing of the in-
terior, where it should not be allowed to accumulate. Instead of this apparatus
it may occasionally be advantageous to use a different one, as that of wet lime
purifiers.of gas, and to force the gas through, such apparatus by means such
as is adopted with coal gas. Other well known acid or saline substances may
be used to collect the ammonia, but I know none at once so simple, efficient,
and economical as sulphuric acid.
But I do not confine myself to the special apparatus or means of operating
here described. What I claim is, the obtaining ammonia from the gaseous.
products of coke ovens and furnaces, or places other than close vessels used
for the combustion or partial combustion and distillation of coal, by passing
such gaseous matters through or in.contact with.acid, water, or other substance
capable of collecting the same.
In witness whereof, I, the said James Thomson Wilson, have hereunto
set my hand and seal, this Sixth day of June, in the year of our Lord