New or Improved Filtering Substance for Filtering or Decoloring Liquids, Applicable for Treating Sugar Juices, and Method of Preparing the same.
Year: 1888

page_text: New or Improved Filtering Substance for Filtering or Decoloring
Liquids, Applicable for Treating Sugar Juices, and Method of
Preparing the same.
I, WILLIAM PHILLIPS THOMPSON, F.C.S. M.I.M.E. of the Agency for Foreign
Patent Solicitors, 6 Lord Street, Liverpool, and 6 Bank Street, Manchester, both in
the County of Lancaster, and. 323 High Holborn, in the County of Middlesex, Civil
Engineer, 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 present invention has for its object a filtering substance which can be applied
either by itself or mixed with the usual well known fibrous and granular filtering
substances for the purpose of purifying or filtering liquids and also for decolouring
them; one of the proposed and prominent applications of the new filtering substance
being the treatment filtering and decoloring of sugar juices. The new filtering agent
consists essentially of a finely divided vegetable (lignous) carbonized material,
preferably sawdust, which if the case require it, may be impregnated with chemical
purifying agents.
Carbonized lignous substances are already known as filtering and decolouring
agents; but carbonized wood has hitherto been used only in two forms which have
each their disadvantages.
Pieces or blocks of charcoal present to the liquid to be filtered only a reduced

page_text: surface; powdered charcoal or charcoal dust only allows the liquid to penetrate
through it with difficulty. In order to avoid the aforesaid disadvantages, the wood is
reduced by mechanical means previous to its carbonization into pieces as small as
possible, presenting a granular or an acicular structure, such as that of the particles
of saw dust and other waste products from saw mills and the like the small pieces
of wood thus obtained retain their shape without producing any dust after they have
been submitted to carbonization.
The improved filtering agent can be impregnated with various substances previous
or subsequent to the carbonizing operation. It can then be applied in various ways.
It has been found that for the purpose of precipitating sulphate of lime contained in a
liquid to be filtered saw dust may be used advantageously, over which previous or
subsequent to the carbonizing operation a solution of saturated chloride of barium has
been poured. It is allowed to stand some time and then thoroughly mixed with
a concentrated solution of carbonate of soda until the baryta is completely
precipitated.
The carbonate of barium adheres firmly to the particles of sawdust which are then
lixiviated and dried.
If the impregnation takes place before the carbonization, the dried saw dust is then
subjected to the carbonizing process. For the purpose of removing carbonate of lime
from the liquid to be filtered it is advisable to pour on the saw dust, previous to its
being submitted to carbonization, a warm solution of crystallized sulphate of magnesia
and to let it stand until the impregnating liquid has penetrated through the pores of
the wood and swells the latter. A warm solution of caustic soda (Liquor natri
caustici) is then added, the substance being stirred meanwhile, so that a small proof of
the filtered liquor begins to show an alkaline reaction. Thereupon the sawdust is
carbonizod and finally lixiviated.
The impregnating operation can also be effected after the carbonization has taken
place the method first described, however, produces a better filtering material.
The carbonate of baryta or the hydrate of magnesia formed in the above treatment
of the saw dust deposits itself in the form of a fine powder in the pores and on the
outer surface of the carbonized wood, and adheres so firmly that it cannot be removed
by mechanical means.
For the purpose of decolouring coloured liquids, a hot aqueous concentrated solution
of alum is poured on the finely divided and carbonized lignous material, a solution of
carbonate of soda then added, while the mixture is being stirred, and finally the
whole diluted sufficiently with hot water.
The precipitate formed here is hydrate of alumina which is distributed in the pores
and on the surface of the charcoal and adheres firmly thereto.
Finally the whole is lixiviated until the chloride of barium gives an insignificant
reaction. Hydrate of alumina possessing already an important superficial attracting
power for the coloring matter, ibis power is still increased by the intimate union of
"the hydrate of alumina with the charcoal.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed, as communicated to
me by my foreign correspondents, I declare that what I claim is :-
1st. The method of producing a filtering material for filtering or decoloring
liquids, which consists in the mechanical reduction of lignous substances to a small
granular or acicular structure, and the carbonization thereof and in impregnating the
lignous substance thus reduced previous or subsequent to the carbonization with
carbonate of barium (if sulphate of lime has to be separated by precipitation) or with
hydrate of magnesia (if carbonate of lime has to be separated by precipitation); and
in case it is wished to produce such a material for the purpose of decoloring liquids
pouring over the said carbonized lignous substances a saturated hot solution of alum
and the addition whilst stirring the mass, of a similar solution of carbonate of soda
and finally the lixiviation of this mixture until chloride of barium gives an insignificant

page_text: reaction, the precipitate to be obtained in the latter case being hydrated alumina
which settles in a finely divided state in the pores of the charcoal, substantially as
described.
2nd. As a filtering substance carbonized sawdust or wood finely divided by
mechanical means and afterwards subjected to carbonization.
3rd. As a filtering substance lignous matter carbonized and then impregnated with
carbonate of barium or hydrate of magnesia, substantially as described.
4th. As a decoloring substance lignous matter carbonized and treated with a
solution of alum and with a solution of carbonate of soda, substantially as described.
Datod this 23rd day of May 1888.
WM. P. THOMPSON & Co.,
Agents for the Applicant.