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Патент USA US2108783

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Patented mm, 1938
2,108,183;
UNITED STATES, ,PAHTIENT OFFICE
,
.
52,168.18:
.
rnocEssoF snrm'rma INORGANIC
.
SALTS raom SOLUTIONS '
.
'
George'W. Smith, Pittsburgh, Pa... assignor to '
Hall Laboratories, Inc” Pittsburgh, 2a., a cor- ,
poratlon ofl’ennsyl
No Drawing. Application March 12, 1936,
Serial No.’ 88,445
’
1'; Claims. .(01. 23-50)
' ' This invention relates-to aprocess oi.’ separat
ing inorganic salts from solutions and provides
means whereby “impurities in the solution, such
as alkaline earth\ metal salts and salts of divalent
5 heavy metals, foraexampleferrous iron and cupric '
copper, are maintained in solution during precip
itation of the inorganic salt from solution.
phosphate will increase ‘with increasing pH val
ues of the solution and decreasing‘solubility of
the substance whose precipitation isto’be avoid
ed. ~Thus, where trisodium phosphate is being
crystallized‘ from ‘a brine containing calcium as 5
an impurity, the pH value of-the brine will be
high. Furthermore, calcium phosphate is quite
_ The present invention is applicable tolthe crys
insoluble. In this case the amount of sodium tallization of common salt fromv solutions con
hexametaphosphate which should be .used is ap-_
10 talning this salt and, in addition, calcium salts ' proximately fifteen times the weight of the cal- 10
- as impurities. Virtually allv'commercial sodium cium which is present in *the solution.
.
chloride brines contain quantities of, calcium sul
phate.‘ ,These brines are evaporated either in
open vessels or under vacuum. As the brine solu- ~
15' tion becomes saturated. with sodium chloride,
crystals of sodium chloride are deposited from
solution in the bottom of the pan or crystallizer.
At the same time, the solution becomes saturated
with calcium salts, principally‘ calcium sulphate.
20 A part of this calcium sulphate precipitates under‘
- certain conditions as scale upon the heating sur
faces and a part of it precipitates as calcium sul
phate sludge along' with 'the sodium chloride,
As ‘another example,gthe invention is useful
in carrying out the precipitation of‘ ammonium
sulphate from ammonium sulphate brine to
which gaseous ‘ammonia and suIphu'ricAacid are 15-‘
continuously added. Calcium and magnesium
from the water used in making therbrine, and’
any calcium, magnesium, ferrous iron or cupric '
copper or. other divalent alkaline earth or heavy
metal present in the sulphuric acidas?impuri- ' 2o
‘ ties, may be held in solution'during the precipi-,
tatlon process‘ by‘ addition to the solutionbf
'- suitable ‘quantities of an alkali-metal - hexameta
, thereby contaminating the sodium chloride.
‘ phosphate. Calcium and magnesium ?nd their.
25, I have found that the calcium sulphate or other ' way into. sulphuric acid from the water which
calcium salt. present'in the solution of sodium
is used in the manufacture of the acid.
"25
_
‘
- chloride as an impurity may be prevented from
crystaliizlng‘ out of solution with .the sodium .
When solutions containingsodium hegrameta-l
' tering'the calcium, magnesium and other metals ‘ '
baths having atemperature of 200?.0, the con- a
‘phosphate are subjected to prolonged heating at
.
chloride upon heating the solution, if an alkali-» high temperatures, vthe metaphosphate reacts l
30 metal 'hexametapho‘sphate is added to the solu
with water to form mono-sodium -orthophos- 3O
tion. The preferred alkali-metal hexametaphos
phate which does not have-the property of seé
.phate is sodium hexametaphosphate, sometimes questering: and keeping in solution the calcium,
called “Graham’s salt". The alkali-metal hexa
magnesium and other divalent alkaline earth or
metaphosphate has the property of formlng?withy ' heavy metals. ‘The present process,_therefore,
35 calcium and magnesium and other divalent heavy is ‘not-applicable. where temperatures are em» 35
metals, soluble very slightly ionized compounds 'ployed which will cause conversion of the hexa
of these metals. In other words, the alkali¢metal metaphosphate into the orthophos'phate. For ex
hexametaphosphate has the property of seques
ample, in the'ca'se of precipitation conducted in
'
'40 in a axlluble and but slightly-ionized condition so 'version would occur very rapidly and the present 40
that
ese metals do. not precipitate along with
‘ the sodium chloride as the sodium chloride crys
tallizes fromsolution upon heating; ‘
'
The quantities of sodium hexametaphosphate.
45 for example, which should be used ior preventing
precipitation of the calcium sulphate will vary
according to the pH value of the solution and
_ according to the solubility of the substance whose
precipitation is :to be avoided.
If the sodium
‘50 chloride solution has a pH value of 7, precipita
tion of calcium sulphate may be prevented by
adding to the solution sodium hexametaphos
phate in an‘ amount about eight times by weight '
' ..
of the quantity of calcium which is present in the'
6:;v solution.
process would‘not. be applicable.
At lower tem- I
peratures, such as 100° C., the sodium hexameta
phosphate will havean effective life of two or
three hours and the process would, therefore, be'
feasible at ‘atmospheric boiling- ‘temperatures, 45'
provided such temperatures were not maintained ~
for too long a time- ' Where vacuum is employed
in carrying out. the precipitation, the tempera
ture may be as low as 50 to 60° C., and at'these
temperatures the hexametaphosphate has an in- 50
de?nite" life and may be used in processes in
which such temperatures are employed for 24
hours
or m 'e'.
.
l
.
'
While I p fer to use sodium'lhexametaphos
The quantities of sodium ,hexameta- I. phate, other alkali-metal hexametaphosphates 55
2,108,788
2
ammonium salt from a solution containing the
same and in addition! an impurity oi the group
consisting of alkaline earth metal salts and salts
‘may be used; such, for example, as potassium,
lithium or ammonium hexametaphosphates.
The invention is applicable to the separation of
inorganic salts from solutions containing as im
of divalentheavy metals, which comprises add
purities any of the alkaline earth or divalent ' ing an alkali-metal hexametaphosphate to‘the
heavy metals. For example‘, sodium hexa'metaphosphate holds in solution calcium, magnesium,
solution to hold the impurities in solution, and
evaporating the solution to precipitate the alkali
ferrpus iron,- cupric copper, lead, strontium, metal or ammonium salt;
'
' barium, manganese, zinc, cadmium, cobalt, and
'5. A process of separating an inorganic salt
10 the like. When these metals or their salts are, of the group consisting of sodium chloride, tri- 10
present as impurities, they may be held in solution during Precipitation of the inorganic Salt by
adding suitable amounts of an alkali-metal
hexametaphosphatetothe solution.
115
sodium phosphate and ammonium sulphate from
a solution containing the same and in addition
an impurity of the group consisting of alkaline
-
earth metal salts and salts of divalent heavy
I have deslcribed Several applications of my
invention.
metals, which comprises adding an alkali-metal l5
It is to'be understood, however, that - hexametaphosphate to the solution to hold the’
these applications are illustrative only and that
the invention is not limited thereto, but maybe
otherwise embodied within the scope of the fol20 lowing claims.
‘
I claim:
'
impurities in solution, and'evaporating the solu
tion to precipitate the inorganic salt.
6.~A process of separating an alkali-metal or
ammonium salt from a solution containing the 20
_
same and in addition an impurity of the group
’ l. A process of separating an alkali-metal or ‘ consisting of alkaline ‘earth metal 'salts and salts
ammonium salt from a solution containing the
of divalent heavy metals, which comprises add.
same and in addition an impurity of the group
25 consisting of alkaline earth metal salts and salts
_ of the divalent heavy metals, which comprises
'adding an alkali-metal hexametaphosphate to the
solution to hold the impurities in solution, and
ing an alkali-metal hexametaphosphate to the
solution to hold the impurities in solution, and 25
evaporating the'solution at a temperature below
about 100° C. to precipitate the alkali-metal or
ammonium salt.
,
evaporating the solution under vacuum to pre-
. 7. A process of separating an alkali-metal or
30 cipitate the alkali-metal or ammonium salt.
2- AJDI‘BCBSS of separating an alkali-metal or.
ammonium salt from a‘ solution containing the
same and in addition an alkaline earth metal salt
as an impurity, which comp es adding an
‘ 35 alkali-metal hexametaphosphate to the solution
.
ammonium salt from a solution containing the 30
same and in addition an impurity oi the group
consisting of alkaline earthmetal salts and salts
of divalent heavy metals,‘ which comprises adding
an alkali-metal hexametaphosphate to the solu
tion to hold the impurities in solution, and 35
to hold the alkaline earth metal salt in solution,
and evaporating the solution to precipitate the
evaporating the lution at a temperature below
about 100° C. and under reduced pressure to
alkali-metal or ammonium. salt.
precipitate the alkali-metal or'ammonium salt.
-
- 3. A process of separating an alkali-metal or
8. A process of separating an alkali-metal
40 ammonium salt from a solution containing the
same and in addition calcium salt as an impurity.
chloride from a solution containing the same and 40
in addition a calcium salt as an impurity, which
which comprises adding an' alkali-metal hexametaphosphate to the solution to hold the calcium
salt in solution, and evaporating the solution
45 to precipitate the alkali-metal or ammonium in-
comprises adding an alkali-metal hexametaphos
phate to the solution to hold the calcium salt in
solution, and Ievaporating the solution to pre
45
cipitate' the alkali-metal chloride.
organic salt. '
.
,GEORGE w. ‘sm'rn.
4. Aprocess of separating an alkali-metal or
'
Patent No. ; 2,168,783.
CERTIFICATE
I
0F CORRECTION -
.
February 15', 195a.
GEORGE'W. shim.
v
‘
It I,is hereby
certified‘ that.
error
appears in the printed specification -
of the above numbered patent‘ requiring correction as follows :‘ Page 2, first.
vcolumn, line 14.5-14.6; c1aim§,-’strike_out the word "inorganid'g‘andthaat the ‘ ‘
said Letters Patent should be read with this ‘correction therein that the
same may conform to the record. of the‘ case in the Patent Office.- Q
‘- Signed-and sealed this 29th day‘ of March, A. D. 1958.
Henry
(Seal) -7
Arscl'aie, '
Acting Commissioner'of Patents.
2,108,788
2
ammonium salt from a solution containing the
same and in addition! an impurity oi the group
consisting of alkaline earth metal salts and salts
‘may be used; such, for example, as potassium,
lithium or ammonium hexametaphosphates.
The invention is applicable to the separation of
inorganic salts from solutions containing as im
of divalentheavy metals, which comprises add
purities any of the alkaline earth or divalent ' ing an alkali-metal hexametaphosphate to‘the
heavy metals. For example‘, sodium hexa'metaphosphate holds in solution calcium, magnesium,
solution to hold the impurities in solution, and
evaporating the solution to precipitate the alkali
ferrpus iron,- cupric copper, lead, strontium, metal or ammonium salt;
'
' barium, manganese, zinc, cadmium, cobalt, and
'5. A process of separating an inorganic salt
10 the like. When these metals or their salts are, of the group consisting of sodium chloride, tri- 10
present as impurities, they may be held in solution during Precipitation of the inorganic Salt by
adding suitable amounts of an alkali-metal
hexametaphosphatetothe solution.
115
sodium phosphate and ammonium sulphate from
a solution containing the same and in addition
an impurity of the group consisting of alkaline
-
earth metal salts and salts of divalent heavy
I have deslcribed Several applications of my
invention.
metals, which comprises adding an alkali-metal l5
It is to'be understood, however, that - hexametaphosphate to the solution to hold the’
these applications are illustrative only and that
the invention is not limited thereto, but maybe
otherwise embodied within the scope of the fol20 lowing claims.
‘
I claim:
'
impurities in solution, and'evaporating the solu
tion to precipitate the inorganic salt.
6.~A process of separating an alkali-metal or
ammonium salt from a solution containing the 20
_
same and in addition an impurity of the group
’ l. A process of separating an alkali-metal or ‘ consisting of alkaline ‘earth metal 'salts and salts
ammonium salt from a solution containing the
of divalent heavy metals, which comprises add.
same and in addition an impurity of the group
25 consisting of alkaline earth metal salts and salts
_ of the divalent heavy metals, which comprises
'adding an alkali-metal hexametaphosphate to the
solution to hold the impurities in solution, and
ing an alkali-metal hexametaphosphate to the
solution to hold the impurities in solution, and 25
evaporating the'solution at a temperature below
about 100° C. to precipitate the alkali-metal or
ammonium salt.
,
evaporating the solution under vacuum to pre-
. 7. A process of separating an alkali-metal or
30 cipitate the alkali-metal or ammonium salt.
2- AJDI‘BCBSS of separating an alkali-metal or.
ammonium salt from a‘ solution containing the
same and in addition an alkaline earth metal salt
as an impurity, which comp es adding an
‘ 35 alkali-metal hexametaphosphate to the solution
.
ammonium salt from a solution containing the 30
same and in addition an impurity oi the group
consisting of alkaline earthmetal salts and salts
of divalent heavy metals,‘ which comprises adding
an alkali-metal hexametaphosphate to the solu
tion to hold the impurities in solution, and 35
to hold the alkaline earth metal salt in solution,
and evaporating the solution to precipitate the
evaporating the lution at a temperature below
about 100° C. and under reduced pressure to
alkali-metal or ammonium. salt.
precipitate the alkali-metal or'ammonium salt.
-
- 3. A process of separating an alkali-metal or
8. A process of separating an alkali-metal
40 ammonium salt from a solution containing the
same and in addition calcium salt as an impurity.
chloride from a solution containing the same and 40
in addition a calcium salt as an impurity, which
which comprises adding an' alkali-metal hexametaphosphate to the solution to hold the calcium
salt in solution, and evaporating the solution
45 to precipitate the alkali-metal or ammonium in-
comprises adding an alkali-metal hexametaphos
phate to the solution to hold the calcium salt in
solution, and Ievaporating the solution to pre
45
cipitate' the alkali-metal chloride.
organic salt. '
.
,GEORGE w. ‘sm'rn.
4. Aprocess of separating an alkali-metal or
'
Patent No. ; 2,168,783.
CERTIFICATE
I
0F CORRECTION -
.
February 15', 195a.
GEORGE'W. shim.
v
‘
It I,is hereby
certified‘ that.
error
appears in the printed specification -
of the above numbered patent‘ requiring correction as follows :‘ Page 2, first.
vcolumn, line 14.5-14.6; c1aim§,-’strike_out the word "inorganid'g‘andthaat the ‘ ‘
said Letters Patent should be read with this ‘correction therein that the
same may conform to the record. of the‘ case in the Patent Office.- Q
‘- Signed-and sealed this 29th day‘ of March, A. D. 1958.
Henry
(Seal) -7
Arscl'aie, '
Acting Commissioner'of Patents.
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