IMPROVEMENTS IN THE TREATMENT AND APPLICATION OF SLAG OR THE REFUSE MATTER OF BLAST FURNACES
Year: 1852

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ALEXANDER
CUNINGHAME, of Glasgow, in the County of Lanark, North Britain, Iron
Master, 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 Eighth day of
March, in the fifteenth year of Her reign, did, for Herself, Her heirs and
successors, give and grant unto me, the said Alexander Cuninghame, Her
especial licence, full power, sole privilege and authority, that I, the said
Alexander Cuninghame, my exors, admors, and assigns, and such others, as
I, the said Alexander Cuninghame, 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 "IMPROVEMENTS IN THE TREATMENT AND APPLICATION
OF SLAG OR THE REFUSE MATTER OF BLAST FURNACES;" in which said Letters
Patent is contained a proviso requiring that I, the said Alexander Cuning-
hame, by an instrument in writing under my hand and seal, shall particularly
describe and ascertain the nature of my said Invention, and in what manner the
same is to be performed, and shall cause the same to be enrolled 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.

page_text: NOW KNOW YE, that in compliance with the said proviso, I, the said
Alexander Cuninghame, do hereby declare the nature of my said Inven-
tion, and in what manner the same is to be performed, to be particularly
described and ascertained in and by this present instrument in writing, as
follows, that is to say :-
My said Invention relates to the so treating and applying what is technically
known as "slag," or the cinder, scoria, or refuse matter discharged from iron
and other smelting or blast furnaces, that this material, which is at present
valueless or nearly so, may be turned to commercially valuable uses.
This improvement I carry into effect by various systems or modes of treat-
ment for the reduction of the constituents of the raw slag to a condition
suitably for their respective special applications. According to one system or
process I treat the slag in such manner as to obtain from it sulphate of alumina
and alum, and for this purpose the slag is first run in its melted state as it
exudes or flows from the furnace into water tanks, the effect of the water's
action being to reduce and disintegrate the material as it cools. The essential
object of this portion of the Invention is the reduction of the slag, which
would otherwise cool and set in hard masses, into an available form for after use
by very simple means; but instead of this mode of reduction the slag may be
mechanically reduced, after cooling in the usual way, by stamping and grinding,
or by other means. When so granulated or disintegrated the slag is next sub-
mitted to the action of sulphuric acid, by placing it in a leaden cistern or
tank, and pouring the acid upon it, The strength of the acid is of little prac-
tical consequence, inasmuch as the slag is decomposable by various strengths;
but I prefer to use acid of such proportionate strength that 120 parts or
thereabouts of dry acid will be applied to every 51 parts of alumina, and 40
parts or thereabouts of dry acid to every 28 parts of lime, and 40 parts of dry
acid to every 20 parts of magnesia,-alumina, lime, magnesia, and silica being
the chief constituents of the slag. The mass of material is then to be left in
this condition until sufficient decomposition takes place. Then, if sulphate of
alumina is to be obtained, this substance is to be dissolved out with the aid of
water, and afterwards separated by decantation or filtration from the sulphate
of lime and silica, the pure solid sulphate of alumina being obtained by evapo-
ration. But if alum is to be made, then a quantity of potash or ammoniacal
salts is to be added to the sulphate of alumina, the alum of commerce being
then obtained by the process of crystalization, as is well known to the practical
The residuum of hydrate of silica and gypsum is valuable as a fertilizer
for land; or instead of such application these matters may be ignited in contact
with aqueous vapour, the resultant sulphurous acid which is driven off being
man.

page_text: available for the production of sulphuric acid in the usual way, whilst the resi-
duary silica and lime may be employed in the manufacture of mortar, cement,
or material for general plastic purposes. By this general process the several
useful products of sulphate of alumina and alum, all which are valuable
manufacturing materials, as well as manures and plastic substances, are produced
at an economical rate from a substance which at present is not only worthless,
but is actually a source of great expense and annoyance to the smelter.
Another portion of my Invention relates to the manufacture or production
of alumina, silica, & chloride of calcium from the slag. The raw material is
first reduced by any or either of the processes which I have already described
herein, and it is then deposited in a vat or vessel of stone, or other suitable
material. Upon the prepared slag so placed, a quantity of muriatic acid is then
poured, the acidulous solution being of any strength or acidification, although
I prefer acid containing about 108 parts of dry acid for every 51 parts of the
alumina, 36 parts of dry acid for every 28 parts of lime, and about 36 parts of
dry acid for every twenty parts of magnesia contained in the quantity of slag
under treatment. When the mass is sufficiently decomposed the resultant
solution of chloride of alumina and chloride of calcium is to be separated by
filtration or decantation, leaving the pure hydrate of silica undissolved, this
latter substance being well washed to clear the solution from it. From this
solution so obtained I procure the earth alumina by two separate processes;
first, by precipitation with milk of lime, ammonia, or other precipitant, and
subsequent filtration, but lime is to be preferred from its cheapness; and,
second, by evaporating the solution to dryness, igniting the residuum, and dis-
solving out the chlorides of calcium and magnesium with the aid of water or
water acidulated with muriatic acid. I obtain the chloride of calcium, con-
taminated with a litte chloride of magnesium, by evaporating the solution as
obtained by either of the modes of obtaining alumina which I have previously
described. The alumina, silica, and chloride of calcium thus obtained are
economically applicable for various purposes; for example, the alumina is
suitable for making alum & sulphate of alumina, as well as the acetate and
other salts of alumina, and the decomposition of the salts of potash and soda,
with the assistance of steam, and for the production of various piginents. The
silica is applicable, amongst other uses, for the manufacture of pottery and
general ceramic uses, as well as for the finer kinds of glass, and the production
of silicates of potash and soda. It is, besides, most valuable as a manure, and
also for the production of mortar & cements, in combination with lime &
other matters, pure hydrate of silica being well known to be the most important
constituent of the best hydraulic mortars. The chloride of calcium possesses

page_text: various uses, and from its peculiar property of fixing ammonia it is suitable for
admixture with guano, independent of its own intrinsic value as a fertilizer.
A third branch of my Invention has reference to the employment of slag for
the purification of pyroligneous acid, in which application there is as well some
economical gain in the amount of alumina obtainable from the slag. At pre-
sent it is usual at certain stages of the processes for making pyroligneous acid,
or vinegar from wood, to saturate the crude acid with lime for the production of
acetate of lime. Now instead of lime I use the reduced or disintegrated slag in this
manufacture, thus obtaining a solution of the mixed acetate of alumina and lime.
By precipitation of the alumina from this solution with the aid of milk of lime, a
large quantity of the tar and other matter in the treated matter is carried down,
whilst at the same time an acetate of lime is formed, just as if lime itself had
been used instead of slag. After ignition the precipitated alumina is applica-
ble to the various uses to which I have herein-before referred; or by another
modification, instead of adding milk of lime to the compound solution of
acetate of lime and alumina, the solution may be evaporated nearly to dryness,
and then placed in a retort, when the portion of the acid which is in combina-
tion with the alumina may be distilled off at a very moderate heat, the acetate
of lime remaining being dissolved out from the insoluble alumina with the
assistance of water. The reduced slag is also applicable for the decomposition
of certain salts. Thus, in order to produce muriatic acid and alkali from the
muriates of potash and soda, a quantity of slag is placed in a retort, which is
then subjected to the action of heat, whilst aqueous vapour and the vapour of
muriate of potash or soda are passed through the retort. This treatment dis-
engages the acid, and the bases of the salt found in combination with the slag
may be separated with the aid of water and carbonic acid, or by cementation
with lime, a quantity of alumina being obtained at the same time, as will be
evident to the practical chemist. Instead of introducing the slag by itself it
may be first ground, and then mixed into balls or masses with the salt, adding
some plastic substance for this combination, or a reverberatory furnace may be
used instead of the retort. The prepared slag is also applicable for the decom-
position of the other salts of potash and soda, according to minor modifications
to suit it for the particular salt to be treated.
Having now described and particularly ascertained the nature of my Inven-
tion, and the manner in which the same is or may be used or carried into effect,
I may observe, in conclusion, that I do not confine or restrict myself to the
precise details or arrangements which I have had occasion to describe or refer
to, as many variations may be made therefrom without deviating from the
principles or main features of my Invention. But what I consider to be novel

page_text: and original, and therefore claim as the Invention secured to me by the herein-
before in part recited Letters Patent, is, the treatment and application of the
slag or refuse matter from blast furnaces for the purposes herein-before
described.
In witness whereof, I, the said Alexander Cuninghame, have hereunto
set my
hand and seal, this Sixth day of September, in the year of our
Lord One thousand eight hundred and fifty-two.
AND BE IT REMEMBERED, that on the Sixth day of September, in the
year of our Lord 1852, the aforesaid Alexander Cuninghame came before our
said Lady the Queen in Ier Chancery, and acknowledged the Specification
aforesaid, and all and every thing therein contained and specified, in form above
written. And also the Specification aforesaid was stamped according to the
tenor of the Statute made for that purpose.