Improvements in the Manufacture of Refractory Materials for Building and other purposes.
Year: 1899

page_text: Improvements in the Manufacture of Refractory Materials for
Building and other purposes.
We, CHARLES FREDERICK CROSS and EDWARD JOHN BEVAN, both of 3 & 4, New
Court, Lincoln's Inn, in the County of London, Consulting Chemists, do hereby
declare the nature of this invention to be as follows:-
In the Specification of former Letters Patent granted to Alexander Imschenetzky
and dated 24th February. 1898, No. 4628, there is described a method or process for
applying silica in the form of silicate of soda to purposes of compacting mixtures
of asbestos fibre, chalk, etc., under conditions which avoid the inconveniences
together with the imperfect products resulting from previous methods of working.
In these previous methods the silica was freed by the addition of a mineral acid
which separated the silica too rapidly and in such unsuitable forms as to make it
difficult to penetrate and indurate fabrics by means of the separated silica. It is
essential for such applications that the silica should be separated gradually from its
solution so that any given material can be thoroughly penetrated with the solution
while the silica is still held in solution, but ready to separate in the gelatinous form
when applied to the material. In the process described in the said former
Specification, either a bicarbonate or carbonic acid is added to silicate of soda to
cause the separation of the silicic acid and it has been found that by that process
the separation is effected under conditions which give perfect control and enable
very hard and compact materials to be prepared, which are useful for structural and
other purposes.
Now we have found by further experiments, that similar effects may be produced
in other directions or by other means. First, we find that sulphurous acid,
preferably in the form of bisulphites, can be used in place of the bicarbonates
specified in the said former Specification, the quantity required being, as an example,
that corresponding with the equation of decomposition as under:
In another process we employ salts of ammonia with acids which combine by
preference with the soda of the sodium silicate; an unstable ammonium silicate
results which in many respects may be regarded as a solution of colloidal hydrated
silicic acid. This solution when applied to a fibrous fabric or mixtures will undergo
decomposition within the substance of the fabric itself, separating gelatinous silica,
and ammonia, the latter being recoverable under the condition that the treatment
is carried out in closed vessels.
In either case, however, although proceeding by apparently very different means.

page_text: what we aim at is the essential condition of a slow and controlled separation of the
silica in the hydrated form from the solution, and we employ the acid group of the
decomposing agent to combine with the soda of the silicate of soda; this acid group
may be either in combination with a weak base like ammonia or it may be a weak
acid combined with a molecule of a neutral salt of this weak acid, the compound
ranking in ordinary chemical language as an acid salt.
It will be seen, therefore, that we effect the separation of a silica from solution as
a soluble silicate of a base by treating the soluble silicate with an acid combined
either with a weak base or with a neutral salt as described, for the purpose of
obtaining the silica in such form and under such conditions that it will serve as
a compacting or agglomerating agent.
Dated 16th Amman 1000
Improvements in the Manufacture of Refractory Materials for
Building and other purposes.
We, CHARLES FREDERICK CROSS and EDWARD JOHN BEVAN, both of 3 & 4, New
Court, Lincoln's Inn, in the County of London, Consulting Chemists, do hereby
declare the nature of this invention and in what manner the same is to be performed,
to be particularly described and ascertained in and by the following statement:-
In the Specification of former Letters Patent granted to Alexander Imschenetzky
and dated 24th February 1898, No. 4628, there is described a method or process for
applying silica in the form of silicate of soda to purposes of compacting mixtures of
asbestos fibre, chalk, etc., in which process the silica is separated in the colloidal form
from the silicate of soda by means of a bicarbonate, or by carbonic acid, and it has
been found that by that process the separation is effected under conditions which
give perfect control and enable very hard and compact materials to be prepared,
which are useful for structural and other purposes.
Now we have found, by further experiments, that similar effects may be produced
by other means. First, we find that sulphurous acid, preferably in the form of
bisulphites, can be used in place of the bicarbonates specified in the said former
Specification, the quantity required being, as an example, that corresponding with
the equation of decomposition as under.
Tour Discipuite).
(soarum supuite).
As a typical example of this part of our invention we will describe the manufacture
of a refractory substance using sodium bisulphite.
A paste is made of asbestos and chalk or like material and squeezed to such an
extent that it can be conveniently handled. It is then dressed or moistened with a
solution of sodium silicate of known strength and, after this has been absorbed, with
a solution of sodium bisulphite made of such strength and used in such quantity as
to bring about the reaction indicated by the above equation.
The material is now dried slowly and then heated to decompose the hydrate of
silica.
The material so made can have more silica deposited within and upon it by a

page_text: repetition of the above process, viz.:-dressing, soaking or otherwise impregnating
with sodium silicate followed by dressing, soaking or impregnating with a solution
of sodium bisulphite of sufficient strength and in sufficient quantity to liberate the
whole of the silica contained in the said silicate.
We have also found that salts of ammonia with acids which combine by preference
with the soda of the sodium silicate (such for example as the sulphate or chloride of
ammonium) can also be employed in lieu of bicarbonates. In this case an unstable
ammonium silicate results which in many respects may be regarded as a solution of
colloidal hydrated silicic acid. This solution when applied to a fibrous fabric or
mixtures will undergo decomposition within the substance of the fabric itself, separat-
ing gelatinous silica, and ammonia, the latter being recoverable if the treatment is
carried out in closed vessels.
As an example of our process using an ammonium salt we will describe the use of
ammonium chloride. The paste being as before prepared, is moistened, dressed, or
impregnated with sodium silicate solution, followed by a similar treatment with a
solution of ammonium chloride(salammoniac) the following reaction taking place, viz. :—
Na₂0.3 (SiO2) + 2 NHCl = 2 NaCl + 3 (SiO2) + OH₂ + 2NH¸
If this operation were carried out in a closed vessel the ammonia could be drawn
off and saved by any of the devices, such as passing it into dilute sulphuric acid, well
known to chemists.
The anhydrous silica is produced by drying and heating the material and if further
depositions of silica are needed they are obtained by further treatment, i.e., dressing,
soaking, or impregnating with sodium silicate, followed by dressing, soaking or
impregnating with ammonium chloride as described above.
Any other ammonium salt may be substituted for the chloride if proper adjust-
ment of the molecular proportion thereof to the molecular weight of the silicate
be made.
In both the above described processes although proceeding by apparently very
different means, what we aim at is the essential condition of a slow and controlled
separation of the silica in the hydrated form from the solution, and we employ the
acid group of the decomposing agent to combine with the soda of the silicate
of soda; this acid group may be either in combination with ammonia or it may be a
weak acid combined with a molecule of a neutral salt of this weak acid, the compound
ranking in ordinary chemical language as an acid salt.
It will be seen, therefore, that we effect the separation of silica from a solution
containing a soluble silicate of a base by treating the soluble silicate with an acid
combined either with a weak base or with a neutral salt as described, for the purpose
of obtaining the silica in such form and under such conditions that it will serve as a
compacting or agglomerating agent.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we declare that what we
claim is:
1. In the manufacture of refractory materials from asbestos mixed with chalk and
the like, upon and between the fibres and particles of which gelatinous silica is
deposited from a soluble silicate with which the substances are impregnated, the
employment of sulphurous acid or bisulphites for decomposing the silicate within
the substance of the fabric, substantially as described.
2. In the manufacture of refractory materials from asbestos mixed with chalk and
the like, upon and between the fibres and particles of which gelatinous silica is
deposited from a soluble silicate with which the substances are impregnated, the
employment of normal or acid ammonium salts, other than bicarbonate of ammonium,
for decomposing the silicate, substantially as described.

page_text: 3. In the manufacture of refractory materials from asbestos mixed with chalk and
the like as claimed in Claim 2, the recovery of the liberated ammonia as herein
indicated and described.
4. The manufacture of refractory materials by the methods, substantially as herein
described.
Dated Guis 20th day of March
D. YOUNG & Co.,
11 & 12, Southampton Buildings, London, W.C., Agents for the Applicants.