Improvements in and relating to the Manufacture of Filters and Filtering Materials.
Year: 1899

page_text: Date of Application, 2nd May, 1899
Complete Specification Left, 16th Oct., 1899-Accepted, 25th Nov., 1899
Improvements in and relating to the Manufacture of Filters and
Filtering Materials.
We, Dr. MAX JOLLES and Dr. ADOLPH JOLLES, of IX, Türkenstrasse 9, Vienna,
Austria, Chemists, do hereby declare the nature of this invention to be as
follows:-
-
As is well known, in addition to sand, carbon, and compositions of all kinds,
asbestos and other porous silicates, as kieselguhr and sandstone, are at present
mainly employed to form filtering substrata. Asbestos is used in many ways-
viz., either directly in the form of a tissue or woven fabric, in the form of fibres
which, in order to make a filtering layer, are drawn by suction upon a perforated
support of wood or metal, or, lastly, in the form of powder which is put upon a
fine-mesh sieve so as to form a layer that serves as a filtering medium.
Now if asbestos in itself offers a very suitable filtering material, nevertheless
the filtration obtained with it, is made almost completely illusory by its present
form of employment. Filters of asbestos tissue possess, namely, the defect that
in the course of use the meshes of the tissues become loose-that is, they open
out whereby it is rendered possible for the smaller impure particles of the liquid
to be filtered, to pass along in the filtrate; whilst, again, in filters of asbestos
fibres in layers, there arises the disadvantage that the sucking-on of the asbestos
fibres can never be so effected in such a uniform manner that uncovered, i.e.
asbestos free, interstices, do not remain, which likewise give channels for the
passage of dirt particles in the filtrate. On similar grounds the process of
filtering by means of heaped up asbestos powder also often fails.
The other silicates, as kieselguhr, sandstone, clay, or mixtures of the same,
which are compressed into cylindrical or prismatic shapes by various known
processes and are then used as filter elements, exhibit, on their side, the disad-
vantage that in this condition they present to the substance to be filtered, layers
that are too thick walled or too finely porous, so that filtration can take place
only with the aid of a pressure or suction action; furthermore, the pores of these
filters are very soon stopped up by the impurities of the substance to be filtered.
In consequence of its becoming often necessary owing to this state of things to
clean and change the stopped up filter-elements, with consequent waste of time,
filtration, by means of silicates or stone-blocks of the kind mentioned, is indus-
trially too costly and difficult to perform.
Now the present invention relates to novel filters or novel filtering material
composing these filters, which is entirely free from the defects herein before men-
tioned.
This filtering material is produced as follows;-a fine-meshed tissue or
woven fabric is covered or impregnated with a thin layer of insoluble, fire-proof,
and at the same time porous substances and this layer is firmly and inseparably
united with the tissue before referred to, by the process hereinafter described.
Asbestos is especially to be recommended as the material for the fine meshed
tissue.
are indeed
Tissues of wool, peat, linen or flax, cotton, artificial wool, etc.
likewise applicable, but they are less to be recommended in as much as in con-
sequence of the subsequently necessary heating they may under certain circum-

page_text: stances prove to be less durable, and this is especially the case when the tissue
is not covered by the hereinbefore mentioned superimposed layer solas to be
perfectly uniformly dense and free from gaps, so that direct access is presented
to the hot gases. By laying on a completely enclosing layer, on the contrary,
this defect is got rid of, since a shield is formed, as it were, which, owing to its
low heat-conducting power, prevents the outer hot gases from exerting their full
heat-effect, on the tissue beneath.
C
Conformably to this invention all bodies composed for the most part of silicates,
as, for examples, asbestos, and,meerschaum-dust, tale, soap-stone, steatite, kiesel-
guhr, sand, pumice-stone, felspar, quartz, silicate of alumina, also the so-called
Paulke bleaching-clay, and terra-clara, materials which (see "Pharmaceutische
Centralhalle" Vol. 39, pages 307 and 734) consist of alumina and magnesia
silicates, furthermore bone black or other porous kinds of carbon, can be used
as insoluble, fireproof, and porous materials, and either separately or in, any
desired mixture, and in finely powdered condition, for the production of the
superincumbent layer upon the fine-meshed tissue.
32
ه از ماده دندم
The durable, firm and inseparable or insoluble union of the above mentioned
substances with the tissue is brought about either by means of silicic acid
separated from alkaline silicates by treatment with acids and rendered insoluble.
by subsequent heating, or by means of equally insoluble compounds (fluorides)
obtained by heating from, silico fluorides which are soluble in water or dilute
acids. It is of great importance in connexion with this that the formation of
these insoluble compounds, acting as it were as cement, should take place directly
on the tissue itself."
>!
The combination of the porous materials before-mentioned with the tissue is
effected as follows: the said porous materials are made into an uniform thick
pap, pulp, or semi-fluid, by mixing them with an aqueous solution of one or
more alkaline silicates or with a solution of silico fluorides (of any desired and
known kind) in water or dilute acids, which have the peculiarity of leaving
behind, after evaporation of the solvent as well as after the neating of the residue,
compounds (silicic acid or fluorides) insoluble in water and acids; and this pap,
pulp, or semi-fluid is laid on the tissue in a thin sheet. The coated tissue is
then, as soon it has been air-dried, exposed to a great heat. When alkaline
silicates are used a thorough soaking of the superincumbent layer with dilute
acids for the purpose of separating the silicic acid must first of all take place,
and the removal of the alkaline salts then formed is effected by subsequent
lixiviation, in so far as they have not already been volatilized by the heating.
By means of the herein before mentioned insoluble compounds, which form
at a temperature of 200°-500° C., the fire-proof and porous substances present
in the mass are cemented firmly to the tissue as well as to one another, as if by
a binding material; and the result is a thin, porous layer, which together with
the asbestos-tissue beneath, presents an excellent filtering material which can not
be passed through even by the smallest solid particles suspended in the liquid
to be filtered; this filtering material has the further advantage over the so-called
block-filters that the thin filter layer does not affect the rate of filtration too
greatly so that this nearly equals that which can be obtained by means of a
simple tissue.
!
1f, for example, the solution of magnesium silico fluorides in water or. dilute
acids is evaporated and the residue heated, there escapes, as is well known, silicium
fluorides, and magnesium fluoride remains behind as the insoluble body:
MgSiFl SIF+MgFl. The hydrochloric acid that may be added to the
water makes. no difference to the result of the preceding process. Its addition
is generally mainly intended to bring larger quantities of the silico fluorides
into solution or to prevent the formation of basic salts, and the process to be
performed in its presence in the case mentioned should be such that firstly by
the action of the hydrochloric acid on the magnesium silico fluoride hydrofluo-
silicic acid and magnesium chloride is formed, then on the subsequent heating,

page_text: It is advantageous to add to the solution of the silico fluoride an earth-alkali
chloride e.g., calcium chloride, strontium chloride &c. whereby there is formed,
after evaporating the solvent and subsequently heating the residue to
about 4000 C., with escape of silicium fluoride and hydrochloric acid, a compound
likewise insoluble and surpassing the magnesium fluoride in binding power,
which consists principally of the fluor-salt of the particular metal earth-alkali.
The soluble bodies existing in this residue, which originate partly in the course of
the process (magnesium chloride) and partly arise from the addition in excess
of the earth-alkali chloride, may be removed by subsequent lixiviation of the
filtering material.
The herein before described process may be represented by the following
It may be remarked here that a permanently firm cementing of the filtering
material is only successfully attained when the method characteristic of the present
process, of obtaining the magnesium fluoride &c., which acts as binding material,
is carried out that is to say, when the separation of the same takes place directly
on the tissue itself by heating suitable compounds, whilst a durable fastening of
the filtering material can in no way be arrived at by placing prepared magnesium
Huoride straightway on the tissue.
For the purpose of manufacturing the novel filter which is here in question, a
frame (provided with an outlet cock) of any desired known kind, of wood or
metal for single elements preferably of hexagonal or cylindrical shape, for several
interconnected filter-elements of prismatic (parallelopipedon) or cubical shape
is surrounded on all sides by a fine-meshed asbestos tissue on which is placed a
thin layer of a material, which is produced in the following manner :-
One or more of the herein before mentioned fire-proof and porous substances
-for example, asbestos powder, Paulke bleaching clay, bone black, or a desired
mixture of such substances-is stirred into a hydrochloric acid solution of magne-
sium silicofluoride and calcium chloride, the density of which is about 30°-0° Bé.,
until a uniform paste results. This paste is smeared over the asbestos tissue.
After this is completely smeared over, one waits until it is air-dried and then
puts the frame for from 1 to 2 hours in an oven, heated to a temperature of
about 2000-500° C. The element taken out of the oven is cooled and washed
until none of the substances (for example, calcium chloride) adhering to the filter,
are found in the wash-water in soluble form.
The filter-element is then placed in a vessel of sheet iron or other suitable
material, and its discharge pipe is joined tight with the suitably provided outlet
of the vessel.
In the case of filters of larger size several elements are placed in this way
in a large vessel of sheet iron or cement, and their outlets are united to a common
discharge pipe of the vessel.
Filtration goes on sufficiently of itself by reason of the difference in level of
the dirty water and the filtrate. But the rate of filtration can be increased by
lengthening the discharge pipe, or by using pressure, or by elevating the dirty
water vessel, the filter vessel being of course necessarily closed on all sides
and made of correspondingly strong material,

page_text: For producing the firm connexion between the tissue and the superimposed
layer an aqueous solution of water glass may be used instead of a solution of
silico fluorides.
F. WISE HOWORTH,
46, Lincoln's Inn Fields, London, W.C.,
Agent for the Applicants.
Improvements in and relating to the Manufacture of Filters and
Filtering Materials.
We, Dr. Max JOLLES and Dr. ADOLPH JOLLES, of IX. Turkenstrasse 9, Vienna,
Austria, 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:
As is well known, in addition to sand, carbon, and compositions of all kinds,
asbestos and other porous silicates, as kieselguhr and sandstone, are at present
mainly employed to form filtering strata. Asbestos is used in many ways-
iz, either directly in the form of a tissue or woven fabric; in the form of fibres
which, in order to make a filtering layer, are drawn by suction upon a perforated
support of wood or metal; or, lastly, in the form of powder which is put upon a
fine-mesh sieve so as to form a layer that serves as a filtering medium.
Now although asbestos is a very suitable filtering material, nevertheless the
filtration obtained with it is made almost completely illusory by its present form
of employment.
Filters of asbestos tissues possess, namely, the defect that in the course of use
the meshes of the tissues become loose-that is, they open out-so that the
smaller impure particles in the liquid to be filtered, can pass away with the
filtrate; whilst, again, in the case of filters of asbestos fibres in layers, there is
the disadvantage that the asbestos fibres can never be sucked-on so uniformly
as to avoid uncovered--i.e. asbestos-free, interstices, which give rise to channels
that allow particles of dirt to pass into the filtrate. On similar grounds the
method of filtering by means of heaped-up asbestos powder also often fails.
The other silicates, as kieselguhr, sandstone, clay, or mixtures of the same,
which are compressed into cylindrical or prismatic shapes by various known
methods and are then used as filter elements, exhibit, on their side the 'dis-
advantage that in this condition they present to the substance to be filtered, layers
that are too dense or too finely porous, so that filtration can take place
only with the aid of pressure or suction action; furthermore, the pores of these
filters are very soon stopped up by the impurities of the substance to be filtered,
so that frequent cleaning and changing of the stopped-up filter-elements with
consequent waste of time, are involved. Hence filtration by means of silicates or
stone-blocks of the kind mentioned, is commercially too costly and difficult.
Now the present invention relates to novel filters or novel filtering material
composing these filters, which is entirely free from the defects herein before men-
tioned.
This filtering material is produced as follows: a fine-meshed tissue or
woven fabric is covered or impregnated with a thin layer of insoluble, fire-proof,
and at the same time porous substances, and this layer firmly and inseparably
united with the tissue before referred to, by the process hereinafter described.
Asbestos is especially to be recommended as the material for the fine-meshed
tissue.
Tissues of wool, peat, flax, cotton, artificial wool, are indeed likewise applicable,

page_text: but they are less to be recommended inasmuch as in consequence of the subse-
quently necessary heating they may, under certain circumstances, prove to be
less durable, and this is especially the case when the tissue is not covered by the
herein before mentioned superimposed layer in a manner perfectly dense and free
from gaps, so that direct access is presented to the hot gases. By laying on a
layer completely enclosing the tissue, on the contrary, this defect is got rid of,
since a shield as it were, is formed which, owing to its low heat-conducting
power, prevents the outer hot gases from exerting their full heating effect on the
tissue beneath.
Conformably to this invention all insoluble bodies composed for the most part
of silica or silicates, as, for examples, asbestos and meerschaum dust, talc, soap-
stone, steatite, kieselguhr, sand, pumice stone, felspar, quartz, silicates of alumina,
also the so-called Paulke bleaching clay and terra clara, materials which (see
"Pharmaceutische Centralhallë Vol. 39, pages 307 and 734) consist of alumina
and magnesia silicates, furthermore, bone-black or other porous kinds of carbon,
can be used as insoluble, fire-proof and porous materials, and either separately or
in any desired mixture, and in finely powdered condition, for the production of
the superincumbent layer upon the fine-meshed tissue:
The durable, firm and inseparable or indissoluble union of the above-mentioned
substances with the tissue is brought about either by means of silicic acid
separated from alkaline silicates by treatment with acids and rendered insoluble
by subsequent heating, or, by means of equally insoluble compounds, (fluorides)
obtained by heating from silico-fluorides which are soluble in water or dilute
acids. It is of great importance in connection with this that the formation of
these insoluble compounds, acting as it were as cement, should take place directly
on the tissue itself.
The combination of the porous materials before mentioned with the tissue is
effected as follows; the said porous materials are made into a uniform thick
paste, pulp, or semi-fluid, by mixing them with an aqueous solution of one or
more alkaline silicates or with a solution of silico-fluorides (of any desired and
known kind) in water or dilute acids, which have the peculiarity of leaving
behind, after evaporation of the solvent as well as after the heating of the residue,
compounds (silicic acid or fluorides) insoluble in water and acids; and this pap,
pulp, or semi-fluid is laid on the tissue in a thin sheet. The coated tissue is
then, as soon as it has been air-dried exposed to a great heat. When alkaline
silicates are used a thorough soaking of the superincumbent layer with dilute
acids for the purpose of separating the silicic acid must first of all take place,
and the removal of the alkaline salts then formed is effected by subsequent
lixiviation, in so far as they have not already been volatilized by the heating.
By means of the herein before mentioned insoluble compounds, which are formed
at a temperature of 200°-500° C., the fire-proof and porous substances present
in the mass are cemented firmly to the tissue as well as to one another, as if by
a binding material; and the result is a thin, porous layer, which together with
the asbestos-tissue beneath presents an excellent filtering material which cannot
be passed through even by the smallest solid particles suspended in the liquid
to be filtered; this filtering material has the further advantage over the so-called
block filters that the thin filter-layer does not affect the rate of filtration too
greatly, so that this nearly equals that which can be obtained by means of a
simple tissue.
==
If, for example, the solution of magnesium silico-fluoride in water or suitable
dilute acids, as in hydrochloric acid, is evaporated and the residue heated, there
escapes, as is well known, silicium fluoride, and magnesium fluoride remains
behind as the insoluble body; MgSiFl SiF+MgFl. The hydrochloric
acid that may be added to the water makes no difference to the result of the
preceding process. Its addition is generally mainly intended to bring larger
quantities of the silico-fluorides into solution or to prevent the formation of basic
salts, and the process to be performed in its presence in the case mentioned should

page_text: The filtering material can be cemented to the before mentioned tissue so as
to be permanently firm only when the process characteristic of this invention
is employed that is to say when the magnesium fluoride which acts as a binding
material, is separated out directly on the tissue by the heating of suitable com-
pounds. It is impossible to insure a permanent cementing of the filtering
material by placing already prepared magnesium fluoride on the tissue.
For the purpose of manufacturing filters according to this invention, a
frame (provided with an outlet-cock) of any desired known kind of wood of
metal for single elements preferably, of hexagonal or cylindrical shape, and for
several interconnected filter-elements of prismatic (parallelopipedal) or cubical
shape is surrounded on all sides by a fine-meshed asbestos tissue, on which is
placed a thin layer of a material which is produced in the following manner:-
One or more of the herein before mentioned fire-proof and porous substances
-for example, asbestos-powder, Paulke bleaching-clay, bone-black, or any desired
mixture of such substances-is stirred into an aqueous or hydrochloric or other
suitable acid solution of magnesium silicofluoride and calcium chloride, the
density of which is about 30° 50° Bé., until a uniform paste results. This paste
is smeared over the asbestos tissue...
After this is completely smeared over, it is air-dried and the frame is then put
for from 1 to 2 hours in an oven, heated to a temperature of about 200°-500° C.
The element taken out of the oven is cooled and washed until none of the sub-
stances (for example, calcium chloride) adhering to the filter, is found in the
wash-water in, soluble form. The filter-element is then placed in a vessel of sheet
iron or other suitable material, and its discharge pipe is connected by a water
tight-joint with a suitable outlet with which the vessel is provided. In the
case of filters of larger size several elements are placed in this way in a large
vessel of sheet iron or cement, and their outlets are united to a common discharge
pipe with, which the vessel is furnished."
Filtration goes on sufficiently of itself by reason of the difference in level of
the dirty water and the filtrate. But the rate of filtration can be increased by
lengthening the discharge pipe, or by using pressure, or by elevating the dirty

page_text: water vessel, the filter-vessel being, of course, necessarily closed on all sides
and made of correspondingly strong material.
For producing the firm connexion between the tissue and the superimposed
layer an aqueous solution of waterglass may be used instead of a solution of
silico-fluorides.
Having now particularly described and ascertained the nature of the said
invention, and in what manner the same is to be performed, we declare that what
we claim is:-
1. A filter in which the operative filtering material consists of a tissue (pre-
ferably of asbestos) which is firmly and durably covered by or united with a layer
formed either of substances that are insoluble in water, acids, and alkalies, and
are fire-proof and porous, as asbestos-powder, talc, kieselguhr, bone-black and the
like or of any desired mixture of such substances either by means of silicic acid,
which is produced directly on the tissue in insoluble form from alkaline silicates
by the action of acids and subsequent heating, or by means of insoluble compounds
(fluorides) separated from soluble silico-fluorides directly on the tissue itself by
heating.
2. The production of filtering material according to Claim 1, by first of all,
in order to obtain a firm and durable union with the tissue, mixing the porous,
fire-proof, and insoluble substances of the kind referred to in Claim 1, which form
the superincumbent layer on the said tissue, with an aqueous solution of water
glass or with an aqueous or dilute-acid solution of silicofluorides of any known
desired kind; then spreading the resultant pasty mass on a tissue stretched over
a frame of any desired shape; and finally after the coated tissue has been air-
dried, and, if alkaline silicates are employed, soaked with acids, exposing it for
from one or two hours to a temperature of about 200°-500° Centigrade.
3. In the production of filtering material according to Claim 2, mixing with
the aqueous or acid solution of a soluble silicofluoride that serves to produce the
superincumbent pasty mass, with chlorides of the metals of the alkaline earths,
as calcium chloride, strontium chloride, with which the said solution or the
residue resulting from the evaporation of their solvent likewise reacts, on heating,
to form insoluble compounds, as calcium fluoride.
4. The improved manufacture of filters and filtering materials herein before
set forth.
n
J 11
13
1
1000
F. WISE HOWORTH,
46, Lincoln's Inn Fields, London, W.C.,
Agent for the Applicants.