ICS 67.220.2 0 
 
Reference number  
DRS 473: 2021  
© RSB 2021  
  
 RWANDA 
STANDARD  DRS  
473  
 
First edition  
2021 -mm-dd 
 
Rock salt (Halite)  — Specification  
   
DRS 473: 2021  
©RSB 2021 - All rights reserved                  ii 
 In order to match with technological development and to keep continuous progress in industries, 
standards are subject to periodic review. Users shall ascertain that they are in possession of the latest 
edition  
 
 
 
 
 
 
 
 
© RSB 2021  
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ePortal: www.portal.rsb.gov.rw   DRS 473: 2021  
iii                ©RSB 2021  - All rights reserved  
 Contents  Page 
Foreword  ................................ ................................ ................................ ................................ ...................  iv 
1 Scope  ................................ ................................ ................................ ................................ .............  1 
2 Normative references  ................................ ................................ ................................ ...................  1 
3 Terms and definitions  ................................ ................................ ................................ ..................  1 
4 Requirements  ................................ ................................ ................................ ................................  2 
4.1 General requirements  ................................ ................................ ................................ ..................  2 
4.2 Specific requirements  ................................ ................................ ................................ ..................  2 
5 Radioactive characteristics  ................................ ................................ ................................ .........  3 
6 Hygiene  ................................ ................................ ................................ ................................ ..........  3 
7 Heavy metals  ................................ ................................ ................................ ................................ . 3 
8 Packaging  ................................ ................................ ................................ ................................ ...... 3 
9 Labelling  ................................ ................................ ................................ ................................ ........  4 
10 Sampling  ................................ ................................ ................................ ................................ ....... 4 
Annex  A (normative)  Determination of the chloride content  calculated as sodium chlorid e .........  5 
A.1 Apparatus  ................................ ................................ ................................ ................................ ...... 5 
A.2 Reagents  ................................ ................................ ................................ ................................ ....... 5 
A.2.1  Potassium chromate solution.  ................................ ................................ ................................ .... 5 
A.2.2  Standard 0.1 N silver nitrate solution  ................................ ................................ .........................  5 
A.3 Procedure  ................................ ................................ ................................ ................................ ...... 6 
A.4 Calculation  ................................ ................................ ................................ ................................ .... 6 
A.5 Report  ................................ ................................ ................................ ................................ ............  6 
 DRS 473: 2021  
©RSB 2021 - All rights reserved                  iv 
 Foreword   
Rwanda Standard s are prepared  by Technical Committees and approved by R wanda Standards Board (RSB) 
Board  of Directors in  accordance with the procedures of RSB, in compliance with Annex 3 of the WTO/TBT 
agreement on the preparation, adoption and application of standards.  
The main task o f technical committees is to prepare national standards.  Final Draft Rwanda S tandards adopted 
by Technical committ ees are ratified  by me mbers of RSB Board of Director s for publication and gazettment as 
Rwanda Standards.  
DRS 473  was prepared by Technical Co mmittee RSB/TC 019, Spices, condiments and food additives  
In the preparation of this standard, reference was made to the following standard  (s): 
1) TAS 6401: Good manufacturing practices for common salt  
2) US 163: Standard of hygienic practise for milk and milk products  
3) RS 293: Milk collection centre (MCC)  
The assistance de rived from the above source is hereby acknowledged with thanks . 
Committee membership  
The following organizations were represente d on the Technical Committee on Spices, condiments and food 
additives  (RSB/TC 019) in the preparation of this standard.  
Agrotech Ltd  
Cheeter Group Ltd  
Gasabo District  
Gorilla Feeds Ltd  
Intertek Morocco  
Nyabihu TVET School  
Nyarutarama Business Incubation Centre  
Prodev Ltd  
Rwanda  Agriculture and Animal Resources Deve lopment Board  (RAB)  
Rwanda Best Farm  DRS 473: 2021  
v                ©RSB 2021  - All rights reserved  
 Rwanda Food and Drug Authority (RFDA)  
Zamura Feeds Ltd  
Rwanda  Standards Board  (RSB) – Secretariat  DRS 473: 2021  
©RSB 2021 - All rights reserved                  vi 
 Introduction   
Rock salt (Halite)  was first discovered in Winsford in Cheshire in 1844, which is the mine used by Online Rock 
salt (Halite) . Local prospectors were originally searching for coal – which, ironically, would be used to heat the  
brine -filled pans that made salt. The value of their find did not go unnoticed, however, and during the nineteenth 
century mining methods led to one million tonnes of Rock salt (Halite)  being mined between 1844 and 1892.  
Rock salt (Halite)  is found in old  ocean sea beds that have long ago dried up. The compound originates from a 
body of sea water that undergoes an intense evaporation process, leaving behind  large rings of sea salt. Then 
through the long process of geologic aging, the salt layers are covere d with marine sediments.  Rock salt (Halite)  
is the least processed form of salt. It is salt that’s taken directly from a salt mine; directly from the underground 
mineral deposit.   Rock salt (Halite)  is used just in the form is found underground.   The only processing done to 
it is that we crush it and screen it to get a size range of crystals that’s convenient to put down on the 
road.   Because of this, it’s also the lowest cost form of salt, and therefore, it’s what’s most commonly used in 
de-icing.  Undergro und salt deposits are extracted by means of drilling, blasting or cutting the rock with the 
following techniques: Continuous mining, d rilling, blasting  and solution mining.  
Rock salt (Halite)  (NaCl) is an ionic compound that occurs naturally as white cryst als. It is extracted from the 
mineral form halite or evaporation of seawater. The structure of NaCl is formed by repeating the face centered 
cubic unit cell. It has 1:1 stoichiometry ratio of NaCl  with a molar mass of 58.4 g/mol. Compounds with the 
sodium chloride structure include alkali  halides and metal oxides and transition -metal compounds. An important 
role to many important applications is structure and dynamics of water. Some applications include crystallization 
of proteins and conformational behavio r of peptides and nucleic acids.  
Rock salt (Halite)  has been used to cure and preserve meat and fish for thousands of years, this simple yet 
effective method of preserving food was a way of life for humans across the globe. The  industry that consumes 
the largest amount of Rock salt (Halite)  is by far the chemical industry. Obtaining chlorine and caustic soda is 
needed before using it in multiple applications or industrial products.  
It is normally know n that Rwanda imports a lot of amount of Rock salt (Halite) s, concerns about the quality and 
safety of importing products. This Rwanda Standard has been developed to establish requirements minimum 
for Rock salt (Halite) s 9halite ). It also exposes the domains application of Rock salt (Halite) s, with the res ults of 
supporting scientific research.  
 
 
 
 DRS 473: 2021  
1                ©RSB 2021  - All rights reserved  
 Rock salt (Halite) — Requirements  
1 Scope   
This Draft Rwanda Standard specifies  requirements , sampling and test  methods  for Rock salt (Halite)  used as 
an ingredient for further processing  in food industry . 
2 Normative references   
The following documents are referred to in the text in such a way that some or all of  their content constitutes 
requirements of this document.  For dated references, only the edition  cited applies. For undated references, the 
latest edition of the referenced document (including any amendments) applies.  
AOAC 920.46, Metals and other constituents in baking po wder 
AOAC 999.11,  Lead,  Cadmium,  Copper,  Iron and zinc in foods. Atomic absorption spectrophotometry after dry 
ashing  
ISO 13164 -3, Water quality — Radon -222 — Part 3: Test method using emanometry  
ISO 2479, Sodium chloride — Determination of matter insoluble in water or in acid and preparation of principal 
solutions for other determinations  
ISO 2480, Sodium chloride for industrial use — Determination of sulphate content — Barium sulphate 
gravimetric method   
ISO 2482, Sodium chloride — Determination of calcium and magnesium contents — EDTA complexometric 
methods  
ISO 2483, Sodium chloride — Determination of moisture content (loss of mass at 110 °C)  
ISO 9696,  Water quality — Gross alpha activity — Test method using thick  source  
ISO 9697 , Water quality — Gross beta activity — Test method using thick source  
RS CAC/RCP 1, General principles for food hygiene — Code of practice  
RS EAS 38, Labelling of pre -packaged foods — Specification  
RS ISO 649 , Animal feeding stuffs — Sampling  
3 Terms and definitions   
For the purposes of this standard, the follow ing terms and definitions apply    
©RSB 2021 - All rights reserved                  2 
 3.1 
mineral  
 naturally occurring homogenous inorganic solid substance having a definite chemical composition and 
characteristic of crystalline structure , colour and hardness.  
3.2 
rock salt (Halite)   
coarsely crystalline, sedimentary rock containing massive, fibrous  and/or granular aggregates  
3.3 
 food grade packaging material  
packaging material, made of substances which are safe and suitable for their intended use and which will not 
impart any toxic substance or undesirable odour or flavour to the product  
4 Requirements  
4.1 General requirements  
Rock salt (Halite)  in its nat ural form shall be: 
a) in the form of a crystalline solid; white or pale pink or light grey in colour ; 
b) free from  any synthetic organic compounds ; 
c) free from any harmful constituents ; and  
d) free from visible contaminants such as clay, grit or extraneous adulterants and impurities.  
4.2 Specific requirements  
Rock salt (Halite)  shall comply with the specific requirements in Table 1 when tested in accordance with test 
methods specified therein.  
Table 1  Specific requirements  for Rock salt (Halite)   
S/N Composition  Requirement  Test method  
i.  Moisture content mass, Max  0.2  ISO 2483  
ii.  Sodium chloride content (as NaCl) per cent by mass, 
min. 95 Annex A 
iii.  Calcium (as Ca) water soluble, % on dry matter 
basis, max.  0.5 ISO 2482  DRS 473: 2021  
3                ©RSB 2021  - All rights reserved  
 iv.  Magnesium (Mg) water -soluble, % on dry matter 
basis, max.  0.5 ISO 2482  
v.  Sulphate (as SO4), % on dry matter basis, max  0.2 ISO 2480  
vi.  Water insoluble matter, per cent by mass, max.  0.2 ISO 2479  
NOTE: These requirements are on moisture -free basis  
5 Radioactive characteristics  
Rock salt (Halite)  shall not exceed limits  for radioactive materials stipulated in Table 2 when tested in 
accordance with test methods specified therein.  
Table 2 — Limits for radioactive materials in Rock salt (Halite)  
 S/N Radioactive material  Maximum Limits in Bq/L  Test method  
i.  Gross alpha activity  0.5 ISO 9696  
ii.  Gross beta activity  1 ISO 9697  
iii.  Radon (Rn) concentration, Max 
Bq/m3 400   ISO 13164 -3 
6 Hygiene  
Rock salt (Halite)  shall be produced, prepared and handled in accordance with RS CAC/RCP 1 . 
7 Heavy metals  
Rock salt (Halite)  shall not exceed   maximum limits for heavy metals in table 3 when tested in accordance with 
test methods specified therein.  
Table 3  Maximum limits for heavy metals  
S/N Heavy metal  Maximum limits  mg/kg  Test method  
i.  Arsenic  0.2 AOAC 920.46  
ii.  Copper  2.0 AOAC 999.11  
 
 
 iii.  Lead  0.1 
iv.  Cadmium  0.05 
8 Packaging  
 Rock salt (Halite)  (halite)  shall be pack aged and supplied in  food grade packaging materials and suitable  
weather -resistant material  complying w ith relevant standards.   
©RSB 2021 - All rights reserved                  4 
 9 Labelling  
In addition to the requirements of RS EAS 38, the following specific labellin g requirements shall apply  and shall 
be legibly and indelibly labelled on each container : 
a) name of product;  
b) guaranteed percentage (by weight) of major nutrients reported as sodium  (as Na) , chloride  (as Cl) , calcium  
(as Ca) , magnesium  (as Mg) , potassium  (as K) , and sulphate  (as SO4) ; 
c) net weight of the product;  
d) batch number;  
e) name and physical address of the manufacturer /importer/packer ; 
f) manufacture date ; 
g) instructions for use and storage conditions ; and  
h) declaration for unique attributes for custom made p roducts shall be declared on packaging.  
10 Sampling  
Sampling of Rock salt (Halite)  (halite) shall be in accordance RS ISO 6497 . 
 
 
 
 
 
 
 
 
 
 DRS 473: 2021  
5                ©RSB 2021  - All rights reserved  
 Annex  A 
(normative)  
 
Determination of  the chloride content  calculated as sodium chloride  
A.1 Apparatus  
Normally available laborato ry glassware.  
A.2 Reagents  
A.2.1  Potassium chromate solution.  
Dissolve 5 g of potassium chromate (K2CrO4) in 100 mL of water.  
A.2.2  Standard 0.1 N silver nitrate solution  
A.2.2.1  Preparation  
Dissolve 17.0 g of silver nitrate (AgNO3) in 1 000 mL of water. Store the solution in the  dark.  
A.2.2.2  Standardization  
A.2.2.2.1  Carry out the standardization in triplicate.  
A.2.2.2.2  Weigh out accurately 5.8 g of analytical reagent grade sodium chloride (NaCl) (previously dried at 
200 °C ± 50 °C for 2 h and cooled to room temperature in a desiccator ) into a 1 L volumetric flask and dissolve 
it in approximately 200 mL of water. Adjust the temperature of this solution to 20 °C and dilute it to 1 000 mL 
with water at the same temperature. Pipette 25 mL of the sodium chloride solution at 20 °C into a 250  mL conical 
flask, add 1 mL of potassium chromate solution, and titrate with the 0.1 N silver nitrate solution until a faint 
reddish -brown colour persists after brisk shaking.  
A.2.2.2.3  Carry out a blank titration using the same procedure but replacing the  25 mL sodium chloride 
solution with 25 mL water.  
A.2.2.2.4  Calculate the mean normality of the silver nitrate solution from the triplicate determinations.  
 
Where,  
 
©RSB 2021 - All rights reserved                  6 
 N is the normality of silver nitrate solution,  
A is the mass of sodium chloride, in grams, in 1 000 mL solution,  
b is the volume of silver nitrate solution, in millilitres, required to titrate 25 mL of sodium chloride solution, and  
c is the volume of silver nitrate solution, in millilitres, required to titrate the blank.  
A.3 Procedure  
A.3.1  Carry ou t the determination in triplicate on each of the test samples.  
A.3.2  Pipette 50 mL of the principal solution reserved in accordance with ISO 2479 at 20 °C, into a 250 mL 
volumetric flask and dilute to 250 mL with water at the same temperature. Mix well and  pipette 25 mL of this 
solution at 20 °C into a 250 mL conical flask. If the solution is acid to litmus, neutralize with sodium bicarbonate 
solution; if the solution is alkaline, add dilute nitric acid (1:10) drop by drop until the solution is acid to litm us and 
then neutralize with sodium bicarbonate solution. Add 1 mL of potassium chromate solution and titrate with the 
standard 0.1 N silver nitrate solution until a faint reddish -brown colour persists after brisk shaking.  
A.4 Calculation  
Calculate the chloride  content as NaCl, on a moisture -free basis (and free -flowing agent -free basis, where 
relevant), as a percentage, as follows:  
 
where  
C is the chloride content, as NaCl, expressed as a percentage (by mass),  
a is the volume of silver nitrate solution, in millilitres, used in the titration,  
N is the normality of the silver nitrate solution,  
B is the mass of sample, in grams, in 1 000 mL principal solution, corrected for moisture content and, where 
relevant, the drier content.  
A.5 Report  
Report the chloride cont ent of each test sample as the mean of its triplicate determinations.  
 
DRS 473: 2021  
7                ©RSB 2021  - All rights reserved  
 Bibliography  
[1] IS 7005 -1973, Standard for Hygienic Conditions for Production, Processing, Transportation and distribution 
of Milk. Indian Standards Institution.  
[2] IS. 3219:1990, Standard o f practice for hygiene for Hygiene in the Food and Drink Manufacturing Industry. 
National Standards Authority of Ireland.  
[3] CAC/DL 22 -1997, Guidelines for the design control measures for street vended foods in Africa. Standards 
Alimentarius commission  
 
 
 
 
 
 
 
 
 DRS 473: 2021  
 
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