IMPROVEMENTS IN THE PRODUCTION OR MANUFACTURE OF ARTICLES OF CAST IRON REQUIRED TO WITHSTAND THE ACTION OF NITRIC AND OTHER ACIDS
Year: 1881

page_text: LETTERS PATENT to Carl Friedrich Claus, of 16, Mark Lane, in the City of
London, for an Invention of "IMPROVEMENTS IN THE PRODUCTION OR
MANUFACTURE OF ARTICLES OF CAST IRON REQUIRED TO WITHSTAND THE
ACTION OF NITRIC AND OTHER ACIDS." A communication from abroad by
Dr. Hermann Uelsmann, of Koenigshutte, Silesia, in the Kingdom of Prussia.
PROVISIONAL SPECIFICATION left by the said Carl Friedrich Claus at the
Office of the Commissioners of Patents on the 3rd January 1881..
CARL FRIEDRICH CLAUS, of 16, Mark Lane, in the City of London. "IMPROVE-
MENTS IN THE PRODUCTION OR MANUFACTURE OF ARTICLES OF CAST IRON
REQUIRED TO WITHSTAND THE ACTION OF NITRIC AND OTHER ACIDS." [A com-
munication from abroad by Dr. Hermann Uelsmann, of Koenigshutte, Silesia, in
the Kingdom of Prussia.]
To obtain an iron suitable for the casting of articles required to withstand the
action of nitric acid, either gaseous or liquid, or which will withstand in a more or
less increased degree the corrosive action of a number of other acids, I alter entirely
the usual working of the blast furnace, that is to say, I begin with making certain
modifications in the methods of reduction of iron from its ores, which are different.
from those usually employed for the production of foundry pig iron.
Now to produce a pig iron which will answer the requirements named, I firstly
lessen considerably the quantity of lime or limestone usually added to the charge of
the furnace, until I obtain instead of the ordinary slag a highly acid or siliceous slag,
the more acid in fact the slag is the better for the purpose, making due allowance
however for the requisite fusibility of the same. Secondly, in order to be able to
run the blast furnace with such a highly acid slag as is required for the purpose
of this manufacture, I use blast more highly heated than is usual, and, thirdly,
I increase considerable the quantity of coke in the charge.
By maintaining these conditions I produce an iron very white in color, which
contains, according to the extent to which the conditions named have been observed,
from 5 to 15 or more per cent, of silicon.

page_text: Having produced for the purposes of this present Invention an iron suitable for
its requirements, I proceed to cast from it the articles desired in the usual way.
Where the casting of acid resisting articles at the blast furnace is not practicable,
and when I am required to remelt the pig iron produced in foundry cupola
furnaces, I find it necessary to vary the ordinary working operations of the cupola
also. Owing to the much higher fusing point of the silicon iron, I find it necessary
to use a larger quantity of coke in the cupola than is usual with ordinary pig iron,
and preferably, though not necessarily, I use heated blast or blast of higher pressure
than usual, or both. The iron may however be remelted in the bed of a rever-
beratory furnace in a reducing flame, and preferably under fleuxes protecting it
against oxidation.
By the employment of these means and the observing of these precautions I
prevent the loss by oxidation of the silicon combined with the iron, which, in this
case, should not exceed 05 per cent. of silicon, but which otherwise might result
in the loss of the greater portion of the silicon, and by such a loss the utility of the
alloy would to a great extent be destroyed.
The articles cast from the iron produced or remelted in the manner described
will resist completely the action of weak or strong nitric acid, liquid or gaseous, or
of mixtures of nitric and sulphuric acids, and also, if not entirely at least to an
increased degree, the action of other acids.
It is needless to say that by the production of such acid resisting articles of iron
and silicon, a great boon is conferred on the chemical manufacturers who either
make or use nitric and other acids. By the use of such articles of plant and tools,
constructions manufactures on a large scale are practicable, which hitherto have.
been carried out in glass. and other vessels of small dimensions.
The valuable properties (physical and chemical) of this iron silicon alloy in its
entirety have never before been turned to useful account in this manner.
In the.
manufacture of steel silicon iron has been employed before, but in it the silicon as
such is not used, since in that process it becomes destroyed and eliminated from
the iron.
To insure a noticeable increased resistance against the the action of acids, it is
requisite that the manufactured castings should not contain less than 5 to 10 per
cent. of silicon. The special advantages of castings of silicon iron are particularly
evident in the case of elements of galvanic batteries made from the same in nitric
acid cylinders, nitre pots, nitro benzol and picric acid plant, in the plant for the
manufacture of dynamite, and such like processes.

page_text: 1
SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Carl Friedrich Claus in the Great Seal Patent Office on the 2nd.
July 1881.
«
CARL FRIEDRICH CLAUS, of 16, Mark Lane, in the City of London. 'IMPROVE-
MENTS IN THE PRODUCTION OR MANUFACTURE OF ARTICLES OF CAST IRON
REQUIRED TO WITHSTAND THE ACTION OF NITRIC OR OTHER ACIDS."
A com-
munication from abroad by Dr. Herrmann Uelsmann, of Koenigshutte, Silesia, in
the Kingdom of Prussia.
In the manufacture of pig iron for foundry purposes the makers have hitherto
aimed at producing an iron rich in carbon and as poor as possible in other
metalloids; this they attain by arranging the proportions in the charges of the
blast furnace so that a highly calcareous slag is produced. The higher a percentage
of lime in the slag is attained the better is the desired result. There is however a
limit beyond which the addition of lime cannot be carried, and which limit is given
by the fusibility of the slag. If such limit be overstepped a slag so difficult of
fusion is produced that the furnace is liable to become choked with congealed slag
("to scaffold"). A highly calcareous though workable slag has when cooled a
stone like fracture and appearance.
In the measure as the percentage of lime to the charge is decreased, and conse-
quently the slag becomes poorer in lime, the slag assumes a more and more glass
like appearance, and becomes more fusible. After reaching a certain maximum of
fusibility, by still decreasing the quantity of lime to be added to the charge the
slag again becomes more and more infusible in proportion to such decrease, until a
point is arrived at (diametrically opposite to that before mentioned) in which the
slag becomes infusible by means of the large proportion of silica it contains, and
such a slag is called a highly siliceous slag.
With the change in the character of the slag a change in the character and com-
position of the iron produced simultaneously is brought about, that is to say, after
the slag has assumed the glassy character the iron takes up more and more of
silicon and less of carbon. When the extreme limits of fusibility of the slag con-
taining a maximum percentage of silica have been attained, a pig iron may be
produced which contains 12° to 20% of silicon.
0
Now to produce a pig iron for castings which require to resist the action of
gaseous or liquid nitric acid and of strong sulphuric acid or mixtures of nitric and
sulphuric acid, I work the blast furnace in such a manner as to produce a highly
siliceous slag and a pig iron containing not less than 5% of silicon, but which may
reach a percentage of 12% to 20% of silicon.
For this purpose I select an iron ore rich in silica, and where such ores are not
obtainable I add silica in any convenient shape (such as sand, stone, flint, and such
like materials) to the charge. As the silica requires for its fusion a base to form
therewith a fusible slag (however highly siliceous that slag may be, and if the ore
itself does not contain sufficient of such base for that purpose (besides oxide of
iron), I add lime in the smallest possible quantity, that is to say, in such quantity
as just to produce the fusion of the silica (and no more) to form a workable slag,
and to prevent the silica from taking up any or much oxide of iron and carrying it
into the slag.
In order that I may be able to produce a fusible slag as highly siliceous as
possible I further increase considerably the quantity of coke in the charge of the..
blast furnace above that which is usually employed, and I further increase the heat
and pressure of the blast for working the furnace. In proportion as these are
increased I increase hereby the percentage of silicon in the pig iron produced.

page_text: Castings may be made direct from the blast furnace, or the silion iron may be
remelted in a foundry cupola.
°
The silicon pig iron produced as above-described (containing 5% to 12 or
20% of silicon) is in proportion to its percentage of silicon.more difficult to fuse
than ordinary cast iron; it moreover is liable in the fused state to loose all or part
of its silicon in the absence of reducing agents (as would be caused. by an insufficient
charge of coke), and in the presence of an excess of oxygen.
When therefore it is required to be remelted in a foundry cupola for the making
of castings required to withstand the action of acid, I use a larger quantity of coke
in the charge of the cupola than is customary with ordinary, foundry pig, and
increase the quantity of coke in proportion to the greater percentage of silicon in
the pig. I further use blast in preference of higher pressure than that used in
cupolas with ordinary foundry pig, and prefer to use heated blast, as is usual in the
blast furnaces. The moulding and casting is otherwise carried out the same as in
ordinary foundry work.
The articles which may with advantage be cast with such silicon iron are those
belonging to the plant for all manufactures in which nitric acid, or mixtures of
nitric and sulphuric acid, or strong sulphuric acid alone is made or used and
worked. Such articles are pots, stills, pans, pipes, condensers, pumps, tools, and
vessels for storing or conveying the acids.
The silicon iron is not acted upon by the acids named, but it also resists more or
less the action of other acids or corroding agents.
I also construct or cast from this iron elements for galvanic batteries to take the
place of those now made of carbon or platinum; for which purpose it is equally
efficaceous and durable with platinum. Articles which are to be enamelled after-
wards I also cast in preference of this silicon iron, as the enamel adheres more
firmly to it.
Silicon iron has never been practically applied for the manufacture of articles in
which the silicon in the iron remained in the iron as such, and in which the peculiar
properties of silicon have been made use of. It has been used in the manufacture
of steel, but in this process the silicon becomes destroyed and converted into silicic
acid, which simply enters into the scoria and is lost. In my process it remains
with the iron in the finished article of use, and imparts to it properties ordinary
cast iron does not possess.
I claim,―
The production of castings from iron produced in the manner above specified, and
which are required to resist the action of acids and corrosion..
In witness whereof, I, the said Carl Friedrich Claus, have hereunto set my
hand and seal, this Second day of July, in the year of our Lord One
thousand eight hundred and eighty one.
CARL
RL FRIEDRICH CLAUS.
(L.S.)