An Improved Process for the Separation of Silicic Acid from Argillaceous Substances.
Year: 1896

page_text: Date of Application, 19th Mar., 1896-Accepted, 2nd May, 1896
COMPLETE SPECIFICATION.
An Improved Process for the Separation of Silicic Acid from
Argillaceous Substances.
I, FERDINAND BRÜNJES of Langelsheim am Harz, Germany, Factory
Proprietor, 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 :-
The processes hitherto known for the analysis of argillaceous substances by
means of the waste sulphuric acid of the tar or oil industry, therefore in the
presence of organic substances, with the view of transforming the silicic acid into
the granular insoluble modification for the purpose of the separation of the
formed sulphate of alumina have entirely failed commercially. Such processes
have for basis that argillaceous substances composed according to the formula
Al2O3 + SiO2 + 2 H2O, are treated with waste sulphuric acid to decompose them in
such a
way that with cleavage off of the silicic acid into soluble gelatinous
modification, sulphate of alumina is at once formed. Upon heating the mixture of
the formed sulphate of alumina and gelatinous silicic acid containing also the
organic matters of the waste sulphuric acid to temperatures absolutely necessary
for transforming the gelatinous into the granular modification required for the
analysis, such nauseously smelling and strongly colouring products of the organic
matters are evolved eveu under 100° Celsius that the waste sulphuric acid cannot
in practice be employed in connection with the reduction of the formed sulphate of
alumina which reduction, owing to the organic matters of the waste sulphuric acid
already begins at said temperature, but the separation of the silicic acid which has
been brought only to the above temperature is quite impracticable commercially as,
owing to it being still too muddy it cannot be separated from the formed strongly
coloured sulphate of alumina either by decanting or filtering. The resulting
sulphate of alumina to be obtained in small quantities is strongly coloured and has
such a nauseous odour that its employment commercially is out of the question.
In order to remove the strongly colouring and nauseously smelling organic
substances and to obtain the silicic acid in a coarse grained modification for the
separation it was found necessary in the usual processes with the use of waste
sulphuric acid for opening out argillaceous substances, to heat the analysis until
the combustion of the carbon arising from the waste acids took place, but the
temperatures necessary to attain this end are so high that the formed sulphate of
alumina is so completely decomposed that only basic sulphate of alumina remains
behind and as this is almost insoluble in water the separation therefrom of the
silicic acid is impracticable.
As distinguished from the aforesaid processes the essential feature of this
invention consists in adding, in the opening out of argillaceous substances by
means of sulphuric acid, organic substances such as molasses, sugar, starch flour
and generally such substances as are carbonised or coked by the sulphuric acid at
100° C., said organic substances being added, for the separation of the formed
sulphate of alumina, to the extent of 0.1 to 0.5 per cent, for each 1 per cent. of the
silicic acid to be split off.

page_text: The organic substances are carbonised or coked direct by the sulphuric acid used
in the analysis and at such a low temperature that:-
1. Colouring and nauseously smelling products do not present themselves.
2. Reduction by said products of the formed sulphate of alumina does not
under any circumstances take place.
3. The transformation of the gelatinous soluble silicic acid into the insoluble
granular modification at the temperatures necessary therefor and the separation of
the formed sulphate of alumina is complete.
In this process the separated gelatinous and likewise the quartzlike silicic acid
from the argillaceous substances places itself in contact with the coke particles in
molecular form derived from the organic substances and thereby forming coke like
cakes which may be easily washed out from the formed sulphate of alumina in
filters or filter presses for the purpose of the separation of the silicic acid.
The organic substances are with advantage previously heated with the sulphuric
acid to be used in the analysis up to from 90° to 100° Celsius and then the
argillaceous substances opened out by this mixture.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :--
process for the separation of silicic acid from argillaceous substances
consisting in adding to the argillaceous substances or to the sulphuric acid such
organic substances which like molasses, sugar, starch flour etcetera, are carbonised
by the sulphuric acid at a temperature under 100° Celsius, substantially as
hereinbefore described...
Dated this 19th day of March 1896
CAPITAINE & VON HERTLING,
89 Chancery Lane, London, W.C., Agents for the Applicant.