TBS/CDC 7 (5816) P 3 (Revision of TZS 134:1981)  
 
©TBS 2020  - All rights reserved        Second Edition  
 
  
 
 
 
 
 
 
 
DRAFT TA NZANIA STANDARD 
 
 
 
 
 
 
 
 
 
Industrial common salt  — Specification  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
TANZANIA BUREAU  OF STANDARDS  
 
 
 
 
  
 
 
 
 
 
 
 
 
 TBS/CDC 7 ( 5816) P3 
2 
  
Foreword 
This Tanzania Draft Standard was prepared by the Technical Committee on  Industrial and laboratory 
chemicals under supervision of Chemicals Divisional Standards Committee and it is in accordance with 
the procedures of the Tanzania Bureau of Standards.  
This second edition cancels and replaces the first edition, TZS 134: 1981  Industrial common salt - 
Specification with the following technical revision:  
i) Introducing parameter for moisture content (on a received basis)  
ii) changing the minimum requirement for sodium chloride (as NaCl) percent, by mass for grade 1.  
For the purpose of deciding whether a particular requirement of this standard is complied with, the final 
value observed or calculated expressing the result(s) of a test or analysis shall, be rounded off in 
accordance with TZS 4 Rounding off numerical valu es. The number of significant places retained in the 
rounded off value should be the same as that of the specified value in this standard.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 TBS/CDC 7 ( 5816) P3 
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 TBS/CDC 7 ( 5816) P3 
 
 
 
 
Industrial common salt  — Specification   
 
 
1. Scope  
This D raft Tanzania Standard prescribes the requirements and the methods of sampling and tests for 
industrial common s alt. 
2. Normative references  
The following normative references are indispensable for the application of this standard. For dated 
references, only the edition citied applies. For undated references, the latest edition of the normative 
references (including amendments) applies  
TZS 4 Rounding off numerical values  
TZS 59/ISO: 3696 Water for analytical laboratory use – Specification and test method  
TZS 132 Fortified food grade Salt - Specification.   
TZS 74 Sulphuric acid - Specification  
 
3. Terms and definitions  
 
<<<<<<<<Not applicable>>>>>>>>  
 
 
4. Requirements  
 
4.1. General requirements  
 
4.1.1  Grades  
For the purpose of this standard the following grades are recognized;  
a) Grade 1 - Suitable for manufacture of hydrosulphite, optical brighteners or where high purity of 
the material is required.  
b) Grade 2 - Suitable for chemical industries, explosive and pyrotechnic industry and for the 
manufacture of caustic soda by electrolytic process.  
 
4.1.2  Description  
Industrial common salt shall be in the form of large or small colourl ess crystals , or white granular 
powder. Salt shall be free from visible contamination with clay grit, and other extraneous adulterants 
and impurities  
4.2. Specific requirements  
Industrial common salt  shall also comply with the following specific requirements given in Table 1, when 
tested according to the methods prescribed in the Annex A.  
 
 
 
DRAFT TANZANIA STANDARD  TBS/CDC 7 ( 5816) P3 
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 Table 1 – Specific requirements Industrial common salt  
SN. No  Characteristics  Requirements for  Methods of Test 
(Ref. to Clause)  
In Annex A  Grade 1  Grade 2  
i.  Moisture content  (on a received basis) , percent by 
mass, max.   1  4 A.2 
ii.  Sodium chloride (as NaCl) percent, by mass. min.  99.5 98.5 A.3 
iii.  Matter insoluble in water, percent  by mass, max.  0.05 0.2 A.4 
iv.  Calcium salts (as Ca), percent by mass, max.  0.03 0.2 A.5 
v.  Magnesium salts (as Mg) percent by mass, max.  0.01 0.1 A.5 
vi.  Sulphate (as SO 4,) percent by mass, max.  0.2 0.6 A.6 
vii.  Iron compounds (as Fe) mg/kg, max.  10 20 A.7 
 
5. Packing and labelling  
5.1 Packing  
Industrial common salt  shall be packed in a suitable container that prevents it from deterioration of its 
quality during storage, transportation and handling.  
5.2 Labelling  
Each package  shall legibly and indelibly label with the information  below  either in English or Kiswahili 
or in combination as agreed between the manufacturer and/or the supplier. Any other additional 
language is optional.  
a) Name and grade of the material;  
b) Name  and address of the manufacturer ; 
c) Trade mark, if any;  
d) Lot or batch number;  
e) Net content ; 
f) Date of manufacture ;  
g) Shall prominently display the words indicating that it is for industrial uses,  not for human 
consumption.  
 
6. Sampling  
The method of drawing representative test samples of the material and the criteria for conformity s hall 
be as prescribed in Annex B . 
 TBS/CDC 7 ( 5816) P3 
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Annex A 
(Normative)  
Methods of test for Industrial common salt  
A.0 General  
Quality of reagents Unless specified otherwise, analytical grade chemicals and water distilled quality 
shall be used in tests (See TZS 59 , see clause 2).  
A.1 Preparation of sample  
A.1.1 Crush 500 g of the sample to pass through a 1 -mm sieve, dry in an air -oven at about 150  °C for 
at least 4 h. Cool  in a desiccator for subsequent tests.  
A.1.2 Accurately weigh about 20 g of the dried sample, dissolve it in 200 mL of water in a beaker. Heat 
to boiling, filter and wash to paper free of chloride. Cool and make up the solution to 1 L. Use this 
solution for subsequent tests.  
A.1.3 For trace metals analysis, dissolve completely 3 200 g of the salt sampl es in water. acidify with 
100 mL  of hydrochloric acid and stir well to dissolve all the soluble ma tter. Filter and make up to 10 L . 
Use this s olution for all trace metals analysis.  
A.2 Determination o f moisture content  
A.2.1 Procedure  - Grind  rapidly the material, as recei ved (say 100 g). in an agate mortar approximately 
to a size of 2.8 mm sieve, but do not actually sieve. The material which shall be in the form of powder 
shall be kept in an air-tight c ontainer. Weigh accurately  20 g of the material in the weighing bottle 
(about 30 mL capacity), preferabl y wide mouth square type, previ ously weighed and dried. D ry in an 
oven at 140  °C to 150  °C for at least 4 h. Cool in a desiccators  and weigh. Repeat drying, cool and 
weigh until constant mass is obtained.  
A.2.2 Calculation  
Moisture, per cent by mass = m1 −m2 ×100  
m1 
Where  
m1 = mass in g of material taken for the test and  
m2 = mass in g of the material after drying.  
 
A.3 Determin ation of total chlorides  
A.3.1 Reagents  
A.3.1.1  Potassium chromate indicator solut ion 5 per cent  
A.3.1.2  Standard silver nitrate solution  - 0.1 mol/L .  TBS/CDC 7 ( 5816) P3 
6 
 A.3.2  Procedure  - Transfer 10 mL of the solution reserved in A.1.2 i nto a conical flask and add 1 mL 
of potassium chromate indicator solution. Titrate against standard silver nitrate solution till the reddish 
brown tinge persists after brisk shaking. Carry out a blank determination.  
A.3.3 Calculation   
Total chloride (as Cl ), per cent by mass,  = 354 .6 ×VM
m  
Where  
V = volume in mL of standard silver nitrate solution used in the titration with the material 
correction to blank.  
M = molarity of standard silver nitrate solu tion, and  
m = mass  in g of the dried sample in 10 mL of the solution taken for the test.  
A.3.3.1 Residual chloride is the chloride obtained by deducting the chloride attributed to the other 
chlorides as described in TZS 132 (see clause 2) from the total chlorides determined in A.3.3   
Sodium chloride (as NaCl), percent by mass = Residual chloride (as C I) x 1.648  
A.4 Determination of matter insoluble in water  
A.4.1 Procedure - Accurately weigh  20 g of the dried sample (s ee A.1.1), dissolve it in 200 mL of 
water  in a beaker, heat to boiling and cool. Filter the solution through a weighed or sintered glass 
crucible (G No. 4) and wash the residue till it is free from chlo rides. Dry the crucible along with the 
insoluble residue to constant mass.  
A.4.2 Calculation   
Matter insoluble in water  = 100  × m1
m2100 x m1 
Where  
m1 = mass in g of the residue, and  
m2 = mass in g of the dried sample taken for the test.  
A.5 Determination of calcium and magne sium.  
A.5.1 Reagents   
A.5.1.1 Standard calcium solution -- Weigh 1.000 g of calcium carbonate dried at 120  °C and after 
cooling dissolve it in the minimum quantity of dilute hydrochloric acid. Dilute tha t solution t o 1 L  in a 
graduated flask. 1 mL of this solution is equivalent to 0.4003 mg of calcium (as Ca).  
A.5.1.2 Standard EDTA solution - Dissolve 3.72 g of disodium ethylenedi aminetetra acetate dihydrate  
in water and dilute in a graduated  flask to 1 L . The solution shall be standardized frequen tly against 
stand ard calcium solution following the procedure given in A.5.2.  
A.5.1.3 Eriechrome black T indicator solution  - Dissolve  0.1 g of the dye in 20 mL of rectified spirit. 
This solution shall be prepared fresh every week,   
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A.5.1.4 Dilute sodium hydroxide solution approximately 10 %.  
A.5.1.5 Murexide indicator solution - Grind 0.2 g of murexide with 10 g of sodium chloride until the 
mixture is homogenous. 0.2 g of this mixture is suitable for 100 mL of the sample solution . 
A.5.1. 7 Ammonium chloride - Ammonium hydroxide buffer solutio n - Dissolve 67.5 g of ammonium 
chloride in a mixture of 570 mL of ammonium hydroxide (sp . gr 0.90) and 250 mL of water. Also 
dissolve separately a mixture of 0.931 g of disodium ethylene diamine tetra acetate dihydrate  anrl 
0.616 g of magnesium sulphate (Mg SO 4.7H 2O) in about 50 mL of water. Mix the two solutions and 
dilute to 1 L.  
NOTE – 5 mL of buffer solution added to 50 mL of distilled water should not consume more than a drop of EDTA 
solution to change to distinct blue with eriochrome black T indicator .  
A.5.2 Procedure  
A.5.2.1 Standardization of EDTA solution - Transfer 25 mL of standard calcium solution into a conical 
flask, add 25 mL of water, 10 mL of ammonium chloride ammonium hydroxide buffer solution, 5 drops 
of the· eriochrome black T indicator solution and titrate against the standard EDT A solution to pure 
blue end point.  
A.5.2.2 Titrate 25 mL of the buffer solution with EDTA solution using eriochrome black T indicattor. 
Subtract  the buffer correction for 10 mL (usually it will be 0.1 mL) from the reading obtained in A.5.2.1 
and note the final titre value. Calculate the calcium equivalent of 1 mL of EDTA solution (say A).  
A.5.2.3  Transfer exactly 100 mL of the solution p reserv ed in A.1.2 into a 250 -mL conical flask, add 10 
mL of ammonium chloride ammonium hydroxide buffer solutio n, add 5 drops of eriochrome blac k T 
indicator solution  and titra te against standard ED TA solution till wine red colour of the solution changes 
to pure blue end point. Note the volume of the standard EDTA solution used in the titration.  
A.5.2.4 Transfer exactly 100 mL of the solution preserved in A.1.2 into a 250 -mL conical flask add 6 
mL sodium hydroxide solution and stir wall. Add 0.2 g murexide (or 100 mg calcein mixed indicator) 
and titrate against standard EDTA solution till wine red colour of the solu tion changes to pure blue end 
point with murexide (or green to purple with mixed calcein indicator). Note the volume of the standard 
EDTA solution used in the  titration.  
A.5.3 Calculation  
Calcium (as Ca),  percent by mass  = A V2
m  
Magnesium (as Mg), per cent by mass =  6068  A (V1 −V2)
m  
Where  
A = Calcium equivalent in mg of 1 mL of EDT A solution determined in A.5.2.2;  
V1 = Volume in mL of standard EDTA solution used in A.5.2.4 (for Ca only);  
V2 = Volume in mL of standard EDTA solution used in A.5.2,3  
m = Mass in g of the dried taken for the test in A.1.2; and  
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A.6 Determination of sulphate  
A.6.1 Gravimetric method   
A.6.1.1 Reagents  
A.6.1.1.1 Dilute hydrochloric acid 4 mol/L  
A.6.1.1.2 Barium chloride solution 10%.  
A.6.1.2. Procedure - Dissolve about 10 g of dried sample preserved in A.1.1 in about 400 mL of water, 
filler and wash the residue free from soluble salts. Collect the filtrate and washings. Add one drop of 
methyl orange and 10 mL of hydrochloric acid or more till it is pink an d boil. Add to t he boiling solution, 
10 to 12 mL of barium chloride solution drop by drop so that the addition is in slight excess and continue 
boiling for 4 min. to obtain a granular precipitate. Allow to stand for 4 h and filter through a weighed 
sintere d glass crucible (G. No. 4). Wash the precipitate till free from chloride a nd dry to constant mass 
at 105 °C to 110  °C. Alternatively, filter through Whatman paper No. 42 and wash till it is free from 
chloride. Ignite and determine as barium sulphate.  
A.6.1.3 Calculation  
Sulphate (as SO 4) percentage by mass =   41.13 m1
m2  
Where  
m1 = massing of barium sulphate, and  
m2 = mass in g of dried sample taken for test.  
A.6.2 Volumetric method  
A.6.2.1 Reagents  
A.6.2.1.1 Standard barium chloride solution 0.025 mol/L, Dissolve 6.108 g of barium chloride dihydrate 
(BaCl.2H 2O) in water and make up to 1 L .  
A.6.2.1.2 Dilute hydrochloric acid 1 mol/L .  
A.6.2.1.3 Standard EDTA solution - Weigh 3.72 g of disodium ethylene diamine  tetra acetate dihydrate 
in water and dilute in a graduated flask to 1 litre. The solu tion shall be standardized frequently against 
standard barium chloride solution (A.6.2.1.1) and follow the procedure given in A.5.2. 1 mL  of standard 
EDTA solution is eq ual to 0.001 374 g of barium (Ba ) or 0.000 96 g of sulphate ion.  
A.6.2.1.4 Eriochrome black T indicator solutio n same as in A.5. 1.3.  
A.6.2.1.5 Ammoniumchloride - Ammonium hydro xide buffer solution same as in A.5. 1 .7.  
A.6.2.2. Procedure  
A.6.2.2.1 Pipette out 20 mL of standard barium chloride solution into a conical flask, add 2 drops of 
hydrochloric acid and 10 mL of ammonium chloride ammonium hydroxide buffer solution. Dilut e it with 
water to 50 -mL, add five drops of eriochrome black T indicator solution a nd titrate against standard 
EDTA solution to pure blue end point. Note the titre value (say Al ).  
A.6.2.2.2 Pipette out 100 mL of the solution preserved in A.1.2 and add 2 d rops of hydrochloric acid 
and heat gentle boiling. To the hot solution, add with a pipette 20 mL standard barium chloride solution. 
Boil gently for about 5 min and then cool to room temperature. The solution will be neutral or slightly TBS/CDC 7 ( 5816) P3 
9 
 acidic when tested w ith a litmus paper. Add 10 mL of ammonium chloride - ammonium hydroxide buffer 
solution and five drops of eriochrome black T indicator solution. Titrate against standard EDT A solution 
to pure blue end point. Note the titre value (say Bl ).  
A.6.2.3 Calculation  
Sulphate (as SO 4), percent by mass (on dry basis) = 0.96 A+V1−B
m 
Where  
A = volume in mL of standard EDT A solution used in A.6.2.2.1,  
V1 = volume in mL of standard EDT A solution 'used in A.5.2.3 (total Ca + Mg),  
B = volume in mL of standard EDTA solution in titration in A.6.2.2.2,  
m = mass in g of dried sample taken for the test in A.1.2.  
 
A.7 Test for iron (Fe) 
A.7.1 Apparatus  
Nessler cylinders  - 50 mL capacity.  
A.7.2  Reagents   
A.7.2.1 Hydrochloric acid - 5 mol/L , free from iron.  
A.7.2.2 Concentrated nitric acid  
A.7.2.3 Potassium thiocyanate solution -- 5 % (m/v )  
A.7.2.4  Dilute sulphuric acid - 2.5 mol/L .  
A.7.2.5 Standard iron solution -- Dissolve 2.819 of iron (ll) ammonium sulphate [FeSO 4(NH 4) SO 4.6H 2O] 
in 10 mL of dilute sulphuric acid and dilute with water to 1 000 mL. Transfer 10 mL of the solution to             
1 000 -mL volumetric flask and dilute again to mark. One milli litre of this solution is equivalent to 4 µg of 
iron (as Fe).  
A.7.3 Procedure - Weigh accurately  2 g of the material and dissolve it in about 20 mL of water. Add 
about 5 mL of hydrochloric acid in order to make the solution acidic and 2 mL of nitric acid and boil to 
oxidize iron salts . Cool and transfer to a Nessler cylinder, add 5 mL of potassium  thiocy anate solution, 
dilute to th e mark with water and stir well into a secon d Nessler cylinder, add 5 mL of hydrochloric acid 
and 2 mL of nitric acid, 5 mL of the s tandard iron solution for Grade 1  and 10 mL of standard iron 
solution for Grade 2 materials and 5 mL of potassium thiocyanate solution. Dilute to the mark and stir 
well. Compare the colour of the solutions in the two cylinders.  
A. 7.3.1 The limit prescribed in Table 1 shall be taken to have not been exceeded if the intensity of 
colour pro duced with the sample is not greater than that produced by the standard iron solut ion.  
 
 
 
 TBS/CDC 7 ( 5816) P3 
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 Annex B  
(Normative)  
Sampling of industrial common salt  and conformity criteria  
B.1. General requirements  
B.1.0  In drawing, storing, preparing and handling test samples the following precautions shall be 
observed.  
B.1.1  Samples shall not be taken at a place exposed to weather.  
B.1.2  Precautions shall be taken to protect the samples, the sampling instrument and the containers 
for samples from adventitious contamination.  
B.1.3  To draw a representative sample, the contents of each container selected for sampling shall be 
mixed thorough ly by suitable means.  
B.1.4  The samples shall be placed in suitable, clean dry and air -tight containers.  
B.1.5  Each sample container shall be sealed air -tight after filling and marked with full details of 
sampling, the date of sampling and year of manufa cture.  
B.2 Scale of sampling  
B.2.1 Lot  
B.2.1.1 For heaps and wagons  - Each individual heap or wagon shall constitute a separate lot.  
B.2.1.2  All packages in a single consignment of common salt of the same grade drawn from single 
batch of manufacture sh all constitute a lot. If the consignment is declared to consist of different -
batches, the batches shall be marked separately and the group of containers in each batch shall 
constitute a separate lot.  
B.2.1.3  The number of packages (n) to be selected from the lot shall depend upon the size of the lot 
(N) and shall be in accordance with Table 2.  
Table 2 - Number of packages to be selected for sampling  
Lot size ,  Number of packages to be selected,  
N n 
Up to 50  3 
50 to 100  4 
101 to 150  5 
151 to 300  6 
301 and above  7 
 
B.2.1.4  The packages shall be selected at random from the lot and in order to ensure randomness of 
selection procedure given in methods for random sampling may be followed.  
 TBS/CDC 7 ( 5816) P3 
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 B.3 Preparation of test samples  
B.3.1  For wagon, and lorry  - From each wagon or lorry draw with an appropriate sampling instrument, 
several portions of the material from different parts, for. example, front, middle and back, and at 
different depths. Collect about 25 kg of the sample in this way.  
B.3.2  For heaps  - In case of heaps draw samples from different heights, depths and intervals. The 
quantity of sample drawn from each height should be proportional to the quantity of salt present in that 
section. Collect about 25 kg of the sample in this way.  
B.3.3  Prepa ration of composite sample  - Spread out the samples collected and mix (see B.3.1 and 
8.3.2) on a level, clean and hard surface. Flatten it out first and then scoop the mass together into a 
cone. Flatten the heap again and divide into four portions. Remove the two diagonally opposite 
quadrants. Mix the remaining two portions well again, form into a cone and repeat this process until 
finally above 2 kg of the material is left. This shall be called the composite sample. This composite 
sample shall be divided i nto three parts one for the purchases, another for the supplier and the third 
as a referee sample.  
Transfer the samples to separate, clean and dry sample containers and label with full identification 
particulars.  
B.3.4 Packages  
B.3.4.1  From each of the packages selected according to B.2.1.4 withdraw portions of about 500 g 
each from different para and collect about 1 kg of sample from each package.  
B.3.4.2  Out of these portions, equal quantities of the material shall be taken and mixed  thoroughly to 
form a composite sample of about 500 g. The composite samples shall be divided into three parts, one 
for the purchaser one for the supplier and the third used as referee sample.  
B.3.5  The referee test samples consisting of composite sample shall bear the seals of both the 
purchaser and the supplier. They shall be kept at a place agreed to between the purchaser and the 
supplier, and shall be used in case of any dispute between the two.  
B.4 Number of tests  
Tests for determination of all the c haracteristics given in Table 1 shall be performed on the composite 
sample.  
B.5 Criteria for conformity  
B.5.1  The lot shall be considered as conforming to this specification if the test results carried on the 
composite sample satisfy the corresponding req uirements given in Table 1.