IMPROVEMENTS IN THE MANUFACTURE OF CEMENTS
Year: 1873

page_text: LETTERS PATENT to Granville Hamilton Forbes, of Broughton
Rectory, in the County of Northampton, Clerk in Holy Orders,
Rector of Broughton, Northamptonshire, for the Invention of "Ix-
Sealed the 2nd December 1873, and dated the 4th June 1873.
PROVISIONAL SPECIFICATION left by the said Granville Hamilton
Forbes at the Office of the Commissioners of Patents, with his
Petition, on the 4th June 1873.
I, GRANVILLE HAMILTON FORBES, of Broughton Rectory, in the
County of Northampton, Clerk in Holy Orders, Rector of Broughton,
Northamptonshire, do hereby declare the nature of the said Invention
for "IMPROVEMENTS IN THE MANUFACTURE OF CEMENTS," to be as follows:-
:-
I thoroughly mix refuse or "foul lime" from gas works, for instance,
with any marl or fine clay containing the necessary quantity of silica
and alumina for the purposes of my said Invention above referred to,
in the proportion of about from 70 to 80 parts of the lime to about
30 or 20 parts of the clay in every hundred pounds by weight of the
compound,

page_text: I do not however limit myself to the above proportions as the quantity
of sulphur in the foul lime is found to vary considerably, according
to circumstances, and it is upon the quantity of sulphur in the foul lime
that the quality of the cements produced by my process depends. I
prefer to use the foul lime in such quantity and of such quality as shall
give not less than three per cent. of sulphur in the whole compound of
lime and clay. But since from the nature of the case this is not always
practicable I do not confine myself to this proportion of sulphur. The
proportion however of foul lime used should not be less than sixty-nine
(69) in every 100 parts of the compound.
After mixing the foul lime and clay as intimately as possible while in
powder I add about 25 parts by weight of coal tar or the tar produced
in the distillation of a mixture of common coal and bitumen, or any
similar bituminous substance. The tar or similar bituminous substance
is intimately mixed with the compound above specified, and the whole
is then pressed into blocks or balls and is subjected to calcination. After
being sufficiently burnt it is reduced to a fine powder; it is then ready
for use; when used it is mixed with water.
Instead of the foul lime I sometimes use a mixture of chalk or
limestone and foul lime in combination with the clay and tar. The
proportion of the chalk or limestone and the foul lime in this mixture
may for the reason above specified vary considerably with circumstances
according to the quantity of sulphur in the foul lime, but I prefer to
use the foul lime in such quantity and quality as shall give to the whole
compound of foul lime and chalk (or limestone) and clay about the same
proportion of sulphur as that specified above.
The proportion which the mixture of the two, namely, the chalk or
limestone and the foul lime bears to the clay, should be such as to give
in the calcined compound about the same proportion as those in the first
specified instance.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Granville Hamilton Forbes in the Great Seal
Patent Office on the 4th December 1873.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, GRANVILLE
HAMILTON FORBES, of Broughton Rectory, in the County of North-
ampton, Clerk in Holy Orders, Rector of Broughton, Northamptonshire,
send greeting.

page_text: WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Fourth day of June, in the year of our
Lord One thousand eight hundred and seventy-three, in the thirty-sixth
year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said Granville Hamilton Forbes, Her special
licence that I, the said Granville Hamilton Forbes, my executors,
administrators, and assigns, or such others as I, the said Granville
Hamilton Forbes, 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 CEMENTS," upon the
condition (amongst others) that I, the said Granville Hamilton Forbes,
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 Granville Hamilton Forbes, 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 :-
The principle of this Invention is so far the same as that of certain
former improvements for which Letters Patent have been granted to
mc, inasmuch as it relates to a combination of certain cement making
materials with tar, whereby the calcination of the said materials is
rendered more expeditious and effective.
By my present Invention I combine marl or clay with the foul lime
of gas works, or of soap or chemical works, and with tar or similar
bituminous substance as hereafter more fully specified.
I thoroughly mix refuse or foul lime from gas works or foul lime
from soap or chemical works with any marl or fine clay containing the
necessary quantity of silica and alumina for the purposes of my said
Invention above referred to, in the proportion of about seventy to eighty

page_text: parts of the lime to about thirty or twenty parts of the clay or marl in
every hundred parts by weight of the compound.
I do not however limit myself to the above proportions, as the quantity
of sulphur in the foul lime is found to vary considerably according to
circumstances, and it is upon the quantity of sulphur in the lime that
the quality of the cement produced by my process depends. I prefer to
use the foul lime in such quantities and of such quality as shall give not
less than three per cent. of sulphur in the whole compound of lime and
clay. But since from the nature of the case this is not always practicable
I do not confine myself to this proportion of sulphur. The proportion
however of foul lime used should not be less than sixty-nine in every
hundred parts of the compound.
! Instead of the foul lime I sometimes use a mixture of chalk and foul
lime in combination with the clay and tar, or pitch, or bituminous
substance. The proportion of the chalk and the foul lime in this mixturo
may for the reason above specified vary considerably with circumstances,
according to the quantity of sulphur in the foul lime, but I prefer to
use the foul lime in such quantity and quality as shall give to the whole
compound of lime and chalk and clay about the same proportion of
sulphur as that above specified.
The proportion which the mixture of the two, namely, the chalk and
the foul lime bears to the clay, should be such as to give in the calcined
compound about the same proportions as those which would result from
calcination in the first specified instance.
In those cases where the foul lime contains too much silica and
alumina I reduce the proportion of clay accordingly, taking care that
the proportion of clay used shall give in the whole compound not more
silica and alumina than would be requisite; for instance, in the manu-
facture of Portland cement I may use when necessary less than twenty
per cent. of clay.
There are various means by which the above specified materials may
be mixed, and I use any convenient means, but I prefer to use a mortar
mill for the purpose. I grind the foul lime (or the foul lime and the
chalk) and the clay together in the mill with sufficient water to effect
an intimate mixture of the materials. The compound is then dried
(either by artificial heat or without it) and ground a second time in the

page_text: mill with from about one-fourth to one-third of its weight of coal tar,
or the tar produced in the distillation of a mixture of common coal and
bitumen, or wood tar, or peat tar, or mineral tar, or pitch, or any
similar bituminous substance, or a combination of any two or more of
them.
When the tar or similar bituminous substance has been thoroughly
amalgamated with the compound above specified the whole is pressed
and moulded or otherwise formed (by hand or machinery) into blocks
or pieces; or it may be pressed by the action of the mill and cut out of
the pan in pieces. It is then subjected to calcination, care being taken
not to overburn it. After being sufficiently burnt it is reduced to a fine
powder, and is then ready for use as cement. When pitch is used it
should be rendered liquid by heat.
Having now particularly described and ascertained the nature and
object of my Invention, and in what manner the same is to be per-
formed or put in practice, I hereby declare that I claim, the use of the
before specified foul lime in combination with marl or clay and coal tar,
or the tar produced in the distillation of common coal and bitumen, or
wood tar, or peat tar, or mineral tar, or pitch, or other similar bituminous
substance, or a combination of any two or more of them for the purpose
of manufacturing cements as herein-before described.
In witness whereof, I, the said Granville Hamilton Forbes, have
hereunto set my hand and seal, this Second day of December
in the year of our Lord One thousand eight hundred and seventy-
three.
Witness,
HENRY SHAW,
GRANVILLE HAMILTON FORBES. (L.B.)
Schoolmaster,
Broughton,
Northamptonshire.