TBS/CDC 7 (5816) P3 (Revision of TZS 134:1981)

©TBS 2020 - All rights reserved Second Edition

DRAFT TANZANIA STANDARD

Industrial common salt — Specification

TANZANIA BUREAU OF STANDARDS

TBS/CDC 7 (5816) P3

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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 values. The number of significant places retained in the rounded off value should be the same as that of the specified value in this standard.

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TBS/CDC 7 (5816) P3

Industrial common salt — Specification 1. Scope

This Draft Tanzania Standard prescribes the requirements and the methods of sampling and tests for

industrial common salt.

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 colourless 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

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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 SO4,) 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 shall

be as prescribed in Annex B.

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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 samples in water. acidify with

100 mL of hydrochloric acid and stir well to dissolve all the soluble matter. Filter and make up to 10 L.

Use this solution for all trace metals analysis.

A.2 Determination of moisture content

A.2.1 Procedure - Grind rapidly the material, as received (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 container. Weigh accurately 20 g of the material in the weighing bottle

(about 30 mL capacity), preferably wide mouth square type, previously weighed and dried. Dry 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 Determination of total chlorides

A.3.1 Reagents

A.3.1.1 Potassium chromate indicator solution 5 percent

A.3.1.2 Standard silver nitrate solution - 0.1 mol/L.

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A.3.2 Procedure - Transfer 10 mL of the solution reserved in A.1.2 into 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 solution, 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 CI) x 1.648

A.4 Determination of matter insoluble in water

A.4.1 Procedure - Accurately weigh 20 g of the dried sample (see 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 chlorides. 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 magnesium.

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 that solution to 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 ethylenediaminetetraacetate dihydrate

in water and dilute in a graduated flask to 1 L. The solution shall be standardized frequently against

standard 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 solution - 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 (MgSO4.7H2O) 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 EDTA 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 preserved in A.1.2 into a 250-mL conical flask, add 10

mL of ammonium chloride ammonium hydroxide buffer solution, add 5 drops of eriochrome black T

indicator solution and titrate against standard EDTA 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 solution 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), percent 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 and boil. Add to the 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

sintered glass crucible (G. No. 4). Wash the precipitate till free from chloride and 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 SO4) 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.2H2O) 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 solution 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 equal 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 solution same as in A.5. 1.3.

A.6.2.1.5 Ammoniumchloride - Ammonium hydroxide 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. Dilute it with

water to 50-mL, add five drops of eriochrome black T indicator solution and 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 drops 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

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acidic when tested with 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 EDTA solution

to pure blue end point. Note the titre value (say Bl).

A.6.2.3 Calculation

Sulphate (as SO4), percent by mass (on dry basis) = 0.96 A+V1−B

m

Where

A = volume in mL of standard EDTA solution used in A.6.2.2.1,

V1 = volume in mL of standard EDTA 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 [FeSO4(NH4) SO4.6H2O]

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 millilitre of this solution is equivalent to 4µg 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 thiocyanate solution,

dilute to the mark with water and stir well into a second Nessler cylinder, add 5 mL of hydrochloric acid

and 2 mL of nitric acid, 5 mL of the standard 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 produced with the sample is not greater than that produced by the standard iron solution.

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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 thoroughly 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 manufacture.

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 shall 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.

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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 Preparation 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 into 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 characteristics 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 requirements given in Table 1.