SMBS Grades
SMBS Grades
SMBS Grades
M 5323 e
April 1999 (rws)
Sodium Metabisulfite
Grades
Sodium
Sodium
Sodium
Sodium
Sodium
Metabisulfite
Metabisulfite PHOTO GRADE
Metabisulfite FOOD GRADE
Bisulfite Solution 38 40 %
Bisulfite Solution FOOD GRADE
Basic Chemicals
Chemical names
Commercial names
Sodium Metabisulfite
Sodium Metabisulfite PHOTO GRADE
Sodium Metabisulfite FOOD GRADE
Chemical formula
Na 2S 2O 5
Molar mass
190.1 g
CAS No.
7681-57-4
EINECS No.
231-673-0
Chemical name
in aqueous solution
Commercial name
Chemical formula
NaHSO 3
Molar mass
104.06 g
CAS No.
7631-90-5
EINECS No.
231-848-0
Properties
Sodium Metabisulfite and Sodium Metabisulfite FOOD GRADE and PHOTO
GRADE are microcrystalline powders with a faint odour of sulfur dioxide;
their bulk density lies between 1.0 and 1.2 kg/l.
Sodium Bisulfite Solution 38 40 % and FOOD GRADE are clear, slightly
yellowish liquids with a strong odour of sulfur dioxide, and pH values
between 3.9 and 4.4.
Sodium metabisulfite decomposes at temperatures above 120 C. If the
containers in which it is stored are not tightly closed, it rapidly absorbs
moisture and is oxidized. The amount of water absorbed by the product in
closed containers depends on the rate of diffusion, which in turn depends
very much on the temperature and relative humidity. Under unfavourable
storage conditions, this may lead to the formation of hard aggregates in
the product, i. e. caking.
All the grades of sodium metabisulfite are readily soluble in water. In
aqueous solution they are in the form of sodium bisulfite, i.e. in the same
form as in our products Sodium Bisulfite Solution 38 40 % and FOOD
GRADE. However, the solution prepared in this way is of higher purity.
Sodium bisulfite solutions undergo oxidation on standing in air.
(g/100 g)
10
15
20
25
30
35
40
Temperature, C
NaHSO 3
Concentration
Density
(g/100 ml)
Amount of Na 2S 2O 5
Required for
Preparation
(g/100 ml)
10.59
16.50
22.86
29.75
37.23
45.19
53.80
9.67
15.07
20.88
27.18
34.01
41.27
49.14
105.9
110.0
114.3
119.0
124.1
129.1
134.5
(g/100 ml)
60
50
40
30
20
10
10
0
10
15
20
25
30
35
40
45
Concentration, g/100 g
Fig. 1
Product specifications
The values and test methods stated in the product specifications below were valid when this Technical Leaflet
was drawn up, but subsequent changes are possible. The current product specifications are available on request.
The only values which are binding are those in the relevant specification sheets then provided.
Sodium Metabisulfite
Property
Unit
Na 2S 2O 5
(g/100 g)
SO 2
(g/100 g)
pH (5 % solution)
NaCl
Typical Value
Limit
Test method
98.0
min. 97.2
66.0
min. 65.5
calc.
< 4.6
4.0 4.8
(mg/kg)
20
max. 50
RCA/Q-IC-01
Heavy metals as Pb
(mg/kg)
max. 10
Iron
(mg/kg)
<5
max. 10
Na 2SO 3 + Na 2SO 4
remainder
calculated
Limit
Test method
Unit
Typical Value
Na 2S 2O 5
(g/100 g)
98.7
min. 98
SO 2
(g/100 g)
66.5
min. 66
calc.
pH (5 % solution)
4.4
4.0 4.5
Na 2S 2O 3
(g/100 g)
max. 0.04
RCA/Q-S-063
NaCl
(mg/kg)
20
max. 30
RCA/Q-IC-01
Heavy metals as Pb
(mg/kg)
max. 10
Iron
(mg/kg)
<3
max. 5
Insoluble matter
(g/100 g)
< 0.01
max. 0.5
Na 2SO 3
(g/100 g)
<1
max. 1.5
Na 2SO 4
remainder
calculated
Unit
Na 2S 2O 5
g/100 g
SO 2
g/100 g
pH (10 % solution)
NaCl
Typical value
Limit
Test method
98.0
min. 97.2
66.0
min. 65.5
calculated
< 4.6
4.0 4.8
RCA/Q-S-066
mg/kg
20
max. 50
RCA/Q-IC-01
Heavy metals as Pb
mg/kg
max. 10
Iron
mg/kg
<3
max. 5
Arsenic
mg/kg
< 0.1
<1
Lead
mg/kg
< 0.1
<1
Copper
mg/kg
<1
Mercury
mg/kg
< 0.03
< 0.1
Selenium
mg/kg
< 0.1
<1
Zinc
mg/kg
<1
Na 2SO 3 + Na 2SO 4
remainder
calculated
Unit
NaHSO 3
(g/100 g)
SO 2
(g/100 g)
Density (at 20 C)
(kg/l)
Iron
(mg/kg)
Typical value
Limit
Test method
39.0
37.5 40.5
calculated
24.0
min. 23.1
RCA/Q-S-054
1.310 1.345
max. 50
1.330
< 20
Unit
Typical Value
Limit
Test method
NaHSO 3
(g/100 g)
39.0
38.0 40.0
RCA/Q-S-054
Na 2SO 3
(g/100 g)
max. 0.7
RCA/Q-S-054
Na 2SO 4
(g/100 g)
max. 1.5
RCA/Q-IC-01
Cl
(mg/kg)
max. 150
RCA/Q-IC-01
Density
(kg/l)
1.335
1.320 1.350
3.9 4.4
max. 20
pH (as is)
Fe
(mg/kg)
< 10
Heavy metals as Pb
(Cd, Cu, Cr, Pb, Zn)
(mg/kg)
< 2 (each)
As
(mg/kg)
<1
Se
(mg/kg)
<1
Hg
(mg/kg)
< 0.05
Application
In the chemical and pharmaceutical industries for various purposes, e. g.
As a reducing agent, for purifying and isolating aldehydes and ketones, for
destroying waste bromine, in the preparation of dyes.
In drinking water treatment to remove excess chlorine.
In special cases to remove oxygen from boiler feed water.
In the treatment of wastewater, e.g. from electroplating plants, to neutralize
chromic acid; to remove excess chlorine in the neutralization of cyanide.
For cleaning and bleaching wool, jute and other vegetable fibres.
In textile dyeing and printing to prepare indigo vats and to solubilize other
dyes.
For solubilizing tanning extracts.
In the paper and pulp industry for bleaching ground wood.
In the photographic and film industry for preparing developer solutions, for
acidifying fixing baths.
Safety
Biological effects
All the sodium metabisulfite grades have a faint odour of SO 2 and irritate
the eyes and respiratory tract. On contact with acids, they may evolve
hazardous quantities of toxic SO 2 gas.
In the water course, sodium bisulfite causes severe oxygen depletion and
may therefore harm aquatic organisms. Further details can be found in our
safety data sheets for the individual products.
Safety advice
MAK for SO 2:
TLV for SO 2:
2 ppm = 5 mg/m 3
2 ppm = 5 mg/m 3
All sodium metabisulfite grades should be stored under cool and dry
conditions. They are stable for six months if the storage temperature does
not exceed 25C and the relative humidity does not exceed 45 %.
If higher temperatures and/or higher humidities occur during storage, this
may lead to a decrease in the SO 2 content and the pH of the aqueous
solution. Similar effects are produced by wide variations in the storage
temperature. The chemical changes may be accompanied by the formation
of more or less hard agglomerates. Compression also causes caking for
example if pallets are stacked on top of one another.
Sodium Bisulfite Solution 38 40 % and Sodium Bisulfite Solution FOOD
GRADE have only limited stability: the solutions should be used up within a
short time. Sodium metabisulfite may crystallize out at temperatures below
10 C.
Note
The information submitted in this publication is based on our current
knowledge and experience. In view of the many factors that may affect
processing and application, these data do not relieve processors of the
responsibility of carrying out their own tests and experiments; neither do
they imply any legally binding assurance of certain properties or of suitability for a specific purpose. It is the responsibility of those to whom we
supply our products to ensure that any proprietary rights and existing laws
and legislation are observed.
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Petrochemikalien und Anorganika
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