Improved Process for Purifying Brines.
Year: 1890

page_text: Date of Application, 16th Sept., 1890-Accepted, 8th Nov, 1890
COMPLETE SPECIFICATION.
Improved Process for Purifying Brines.
I, HERBERT JOHN ALLISON, of 52 Chancery Lane, London, in the County of
Middlesex, Patent Agent, do hereby declare the nature of this invention (which has
been communicated to me from abroad by Mauricio Manuel Monsanto, of the City
of Hoboken, County of Hudson, State of New Jersey, United States of America,
Civil Engineer), and in what manner the same is to be performed to be particularly
lescribed and ascertained in and by the following statement :-
The object of this invention is a new and useful process for the purification of
brines for the production of merchantable salt.
The invention consists in the application to the brine of the salt tri-sodium
phosphate (Na, Po₁) for eliminating the lime, magnesia, iron, etc., and their
compounds out of the brine by forming insoluble phosphates with the phosphoric
acid of the tri-sodium phosphate, so that these impurities can be extracted, by
subsidence or filtration, from the brine.
The impurities ordinarily found in brines are the sulphates, carbonates and
chlorides of lime, magnesia and iron, which substances form scale on the heating
surfaces of the evaporating pans and also produce impure salt.
The base of Na, Po, being sodium, it will have no effect whatever on the chloride of
sodium, but through the decomposition, by the phosphoric acid, of the compounds of
lime, magnesia, etc., the liberated sulphuric acid of the sulphates will form sulphate
of soda from the soda of the Na, Po, which sulphate of soda is highly soluble and will
remain in the mother liquid and is not injurious to health nor detrimental to the
quality of the salt made.
The chlorine liberated from the impurities will also combine with the sodium of
the Naz Po, thereby forming common salt, chloride of sodium, increasing, consequently,
the output.
4
The sodium phosphate, though of alkaline re-action is not caustic but perfectly
neutral and has the property of preserving iron and of saturating any free acids that
may be introduced in the brine or that may be produced in the process of manu-
facture, which is not the case with ordinary sodium phosphate.
The calcium and magnesium, which are converted in this process into insoluble
phosphates, are very light and flocculent and have the property of enveloping other
impurities, an action similar to that of gelatinous substances or of coagulated
albumen, and clarifies in the same way.
The tri-sodium phosphate has, as found in practice, the further unexplained
property of destroying the adhesive quality of sulphate of lime to the heating
surfaces of the brine-evaporating vessels, and of preventing the formation of scale
thereon even when a less quantity of the Na, Po, is used than is required to fully
saturate the sulphate of lime; therefore much less of the tri-sodium phosphate than
any other purifying compound is required in making good commercial salt, and its
use is very economical.
The tri-sodium phosphate may be applied to the brine when the latter is in the cold
state in tanks, or when it is hot.
The precipitate may be allowed to subside to the bottom of the containing vessel
and clarified and purified brine be drawn off from above it, or the whole contents
of the vessel may be passed through a filter, preferably through a filter press, or the
tri-sodium phosphate may be introduced directly into the evaporating vessel, where
it will convert the impurities in the brine into harmless precipitates which will remain
in a flocculent condition in the mother liquid.
This tri-sodium phosphate may also be applied in combination with any inert
granulated substance, such as charcoal, coke, sawdust and the like, which substance

page_text: would materially aid in the separation from the brine, by subsidence or filtration of
the impurities therein, especially if the filtration be done through a filter press, as the
combination of the granular substance with the flocculent precipitate would produce
a porous mass that would prevent the serious clogging of the filter and could readily
be cleaned off.
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
1. In the manufacture of salt, the process substantially as herein described, of
purifying brines by introducing therein tri-sodium phosphate in sufficient quantity to
decompose and precipitate the impurities in the brine, and in then separating the
purified brine from the precipitate by decantation or filtration, as set forth.
2. In the manufacture of salt, the process substantially as herein described, of
purifying brines by introducing therein tri-sodium phosphate to decompose and
precipitate the impurities in the brine, as set forth.
Dated this 16th day of September 1890.
ALLISON BROS.,
Agents for the Applicant.