AN IMPROVED GYPSUM CEMENT
Year: 1872

page_text: LETTERS PATENT to William Robert Lake, of the Firm of Haseltine,.
Lake, & Co., Patent Agents, Southampton Buildings, London,
for the Invention of "AN IMPROVED GYPSUM CEMENT."-A communi-
cation from abroad by Emil Friederich August Schott, of Seesen,
Germany, Chemist.
COMPLETE SPECIFICATION filed by the said William Robert Lake
at the Office of the Commissioners of Patents, with his Petition
3
and Declaration, on the 13th July 1872, pursuant to the 9th
Section of the Patent Law Amendment Act, 1852.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
ROBERT LAKE, of the Firm of Haseltine, Lake, & Co., Patent Agents,.
Southampton Buildings, London, send greeting.
WHEREAS I am in possession of an Invention for "AN IMPROVED
GYPSUM CEMENT," and have petitioned Her Majesty to grant unto me,.
my executors, administrators, and assigns, Her Royal Letters Patent for

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cated to me from abroad by Emil Friederich August Schott, of Seesen,
Germany, Chemist.
NOW KNOW YE, that I, the said William Robert Lake, do hereby
declare that the following Complete Specification, under my hand and
seal, fully describes and ascertains the nature of the said Invention, and
in what manner the same is to be performed, in and by the following
statement ---
-
I reduce natural anhydrite by any known mechanism to a coarse
grained or fine powder, and mix it with 73.5% of limestone powder or
chalk. The mixture thus obtained is heated in a puddling furnace so
that it becomes liquid, and then it is crutched by means of iron tools
through a side opening and cooled. The furnace is then again filled.
To melt the mixture I use the well known furnace of Siemens' as
employed to puddle pig iron, or any other furnace by which a tempera-
ture of 2000° C. can be obtained, the melting of the mixture being only
obtained at a full white heat. This operation can also be accomplished
by various other manipulations without departing from the spirit of this.
Invention.
If the limestone is difficult to pulverize it may be first burned and
reduced by slacking to powder. The subsequent operations being the
same in either case.
Where anhydrite is not conveniently obtainable other material may
be employed consisting chemically of sulphate of lime. The operation
is the same, but the proportion of the mixture must be calculated in
relation to the chemical component of the raw material in such a way
that the mixture contains 40 parts of sulphurous anhydrite and 56 parts
of lime (oxide of calcium) whatever the other ingredient may be. The
mass smelted in the puddling furnace contains basic sulphate of lime,
a chemical combination of two equivalents of lime and one equivalent of
sulphate of anhydrite, which has the property of hardening when powdered
or pulverized and mixed with water. The melted mass is reduced by
machinery to a powder of different sizes which forms the cement ready
for use.
The coarser of which, the grains are of the size of gunpowder,
is principally used as cement for hydraulic work, whereas the fine
powder is applied to stucco work. The latter is mixed with a slight
quantity of water, and the wetting and hardening of the mass is finished
in from ten to twenty hours. A piece of the coarse grained powder;
'

page_text: caked in water becomes hard in about a month, of fine powdered mass
in from 8 to 14 days. The coarse grained mass thrown into water sinks
to the ground and hardens very slowly but very effectually.
*
The neutral sulphate of lime heated alone sinters in a white heat to a
crystalline mass, whereby it loses some sulphuric acid but does not
become soft and less liquid. The oxide of calcium is a fireproof. body.
It is well known that combinations of weakly burnt gypsum and lime
are used for building purposes as mortar, but they are quite unfit for
use as hydraulic cement. All those mixtures rapidly moisten by the
action of the burned gypsum and harden afterwards in the air by taking
up carbonic acid, but put into water pieces made of such combinations
become soft and lose all consistency. Combinations of anhydrite.or.
outburnt gypsum with lime do not harden in water and differ from my
gypsum cement in the same way as a mixture of argillaceous earth or
clay and lime differs from Portland cement.
My gypsum cement is a basic sulphate of lime as Portland cement is
chiefly a basic silicate of lime. The chemical combination is (C₁ O₂)
SO, and it will combine with 7 parts of water, whereas a mixture of
equal parts of sulphate of lime and oxide of calcium takes up only
3 parts of water, which is effected under great heat, whereas gypsum
cement does not become warm in water.
It is clear that this Invention is of great importance; large quantities
of anhydrite nearly worthless being stored up in the mountains and
infinite masses of gypsum being thereby made profitable for commercial
purposes.
The gypsum cement takes up water slowly, but otherwise it has the
same qualities as Portland cement, of which it may take the place in
nearly all cases. It is distinguished from almost all other cements by
its light color, and can be used in more cases as it may be applied to
stucco work and the manufacture of artificial marble.
The cost of manufacture is less than that of Portland cement, because
the raw material is very cheap, and mixed in a dry state the mixture
need not be made very carefully. The effect of fuel is much greater in
puddling furnaces than in intermitting blast furnaces as used generally
in the manufacture of Portland cement. The moment when the gypsum
cement is burned can be easily ascertained by any, workman, and no.
loss is occasioned by unfit or overburnt products.

page_text: Having thus fully described the said Invention as communicated to
me by my foreign correspondent, and the manner of performing the
same, I wish it understood that I claim the compound of equal parts
of sulphate of lime and oxide of calcium which becomes liquid, and is
employed in the manufacture of gypsum cement in puddling furnaces
as herein described; also the use of this melted mass in a pulverized.
state as hydraulic cement in the manner above specified.
In witness whereof, I, the said William Robert Lake, have here-
unto set my hand and seal, this Thirteenth day of July, in
the year of our Lord One thousand eight hundred and seventy-
two
Witness,
WILLIAM JOHN LOWE.
W". ROBT. LAKE. (L.S.)