Year: 1899

page_text: I, GERHARD NICOLAAS VIS, Doctor of Philosophy, at Schweizerhalle, near Basle,
Switzerland, Chemist, do hereby declare the nature of this invention to be as
follows:-
The present invention relates to the purification of brine, especially of brine rich
in magnesium salts, and is devised to render the purification more effective than
hitherto.
Brines which are rich in magnesium salts are difficult of purification as the
magnesium salts contained cannot be reduced to unsoluble magnesium hydroxyde by
means of lime without causing a corresponding amount of soluble lime salts (especially
chloride of calcium) to be formed in the brine, in order to remove which a consider-
able quantity of soda is required; on the other hand; the magnesium contained
therein is obtained in the form of almost worthless magnesium hydroxide.
I have found that brines rich in magnesium salts and sulphates can be purified in
a simple manner by means of the following process which is moreover, not only
inexpensive but even profitable.
The improved process consists first in the combined use of the reaction which takes
place between magnesium salts and caustic lime resulting in the precipitation of
magnesium hydroxide and of the fact that a considerable part of the gypsum in
solution in the brine can be caused to separate out by the addition to the brine of
easily soluble sulphates, such as sulphate of sodium, alum and the like with constant
stirring, so that a maximum of magnesium hydroxide and gypsum is obtained, and,
secondly, in transferring the sulphuric acid contained in the gypsum to the
magnesium hydroxide by first treating the said mixture of magnesium hydroxide
and gypsum with carbonic acid in the presence of steam whereby the magnesium
hydroxide is converted into magnesium carbonate, and then agitating the now exist-
ing mixture of gypsum and carbonate of magnesium with water whereby the magnesium
carbonate is caused to react with the gypsum so that sulphate of magnesium and
carbonate of calcium are formed.
In carrying out the invention the brine to be purified is mixed with the quantity
of caustic lime found necessary by analysis and previously slaked with water, together
with the soluble sulphate, the mixture being kept continually agitated. The addi-
tion of the sulphate is determined with regard to the formation of chloride of
calcium which takes place from the chloride of magnesium present. I usually prefer
to make use of sulphate of sodium. The agitation is to be continued for about
30 hours.
The mixture of precipitated magnesium hydroxide and gypsum obtained is
separated from the brine by filtration, and freed from the adhering brine as completely
as possible by washing with water. This washing must not, however, be continued
too long, in order not to dissolve too much gypsum. After washing the filtrate is
stirred up with water, carbonic acid (for instance purified furnace gas) is introduced,
and also steam, in order to prevent the formation of soluble bicarbonates of magnesium
and of lime by excess of carbonic acid, the stirring. being continued during this
treatment with carbonic acid.

page_text: The brine filtered from the mixture still contains per 1 cubic metre :
1.77 kilos. of sulphate of calcium, and 15.00 kilos. of sulphate of sodium.
The sulphate of calcium is precipitated as carbonate of lime by the addition of
1.4 kilo. sodium carbonate per cubic metre, and thus a brine entirely free from
gypsum is obtained containing the above 1500 kilos. of sodium sulphate which
remain in the mother liquor on boiling and can be used in the purification of a fresh
quantity of brine.
Dated the 18th day of November 1899.
W. P. THOMPSON & Co.,
322, High Holborn, London, W.C., Patent Agents for the Applicant.
COMPLETE SPECIFICATION.
Process for the Purification of Brine.
I, GERHARD NICOLAAS VIS, of Schweizerhalle, near Basel, Switzerland, Doctor of
Philosophy and Chemist, 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 relates to the purification of brine, especially of brine rich
in magnesium salts, and is devised to render the purification more advantageous
than hitherto.
Brines which are rich in magnesium salts are difficult of purification as the
magnesium salts contained cannot be reduced to insoluble magnesium hydroxide by

page_text: while sulphate of calcium is formed according to the reaction:
MgSO4 + Ca(OH)₂ = Mg(OH), + CaSO.
Part of the calcium sulphate formed enters in solution the remainder being separated
out.
It is important to separate out so much sulphate of calcium together with the
magnesium hydroxide that both are present in the precipitate in the proportion of
their molecular weights, that is about 235 parts of sulphate of calcium to 100 parts
hydrate of magnesium. This is attained, as said, by adding besides the caustic lime
a suitable quantity of Glauber salt (sulphate of sodium), such addition having the
effect, as described in my British Patent No. 7107, dated April 4th, 1899, to cause
sulphate of calcium to separate out in proportion to the quantity of Glauber salt added.
In carrying out the invention the brine to be purified is mixed with the quantity
of caustic lime found necessary by analysis and previously staked with water, together
with the proportion of soluble sulphate required for obtaining the mixture in the
proportions above stated, the mixture being kept continually agitated. I usually
prefer to make use of sulphate of sodium. The agitation is to be continued for
about 30 hours.
The mixture of precipitated magnesium hydroxide and gypsum obtained is separated
from the brine by filtration, and freed from the adhering brine as completely as
possible by washing with water. This washing must not, however, be continued too
long, in order not to dissolve too much gypsum. After washing the filtrate is stirred
up with water, carbonic acid (for instance purified furnace gas) is introduced, and also
steam, this latter in order to prevent the formation of soluble bicarbonates of
magnesium and of lime by excess of carbonic acid; the stirring being continued
during this treatment with carbonic acid.
As soon as the hot inass no longer colours turmeric paper brown, shewing that all
the magnesium hydroxide is transforined into magnesium carbonate-which usually
will be found after about 12 hours agitation, it is allowed to settle, the clear solution
is drawn off, and the deposit treated repeatedly with hot water until no more sulphate
of magnesium washes out,

page_text: The brine filtered from the mixture still contains per 1 cubic meter:
1.77 kilos. of sulphate of calcium, and 15·00 kilos. of sulphate of sodium.
The sulphate of calcium is precipitated as carbonate of lime by the addition of
1.4 kilo. sodium carbonate per cubic meter, and thus a brine entirely free from
gypsum is obtained containing the above 15.00 kilos. of sodium sulphate which
remain in the mother liquor on boiling and can be used in the purification of a fresh
quantity of brine.
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 purification of brine rich in magnesium salts with the transforma-
tion of the latter into Epsom salts which consists in agitating the brine together
with caustic lime and a soluble sulphate (sulphate of sodium, alum and the like)
precipitating thereby a mixture of magnesium hydroxide and gypsum, filtering,
freeing the filtrate from dissolved gypsum by treatment with soda or equivalent
reagents, filtering and boiling, and treating the above precipitate (mixture of mag-
nesium hydroxide and gypsum) with carbonic acid, stirring the mixture of magnesium
carbonate and gypsum obtained with water, and causing the solution of magnesium
sulphate thus obtained to crystallise, substantially as specified.
1000
W. P. THOMPSON & Co.,
Of London, Liverpool, Manchester and Birmingham.