TBS/CDC 7(5811) P 3 (Revision of TZS 507: 1999) 
 
 
 
 
 
© TBS 2020                  Second  Edition 2020 
 DRAFT TANZANIA STANDARD  
 
 
 
Sodium bicarbonate – Specification  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
TANZANIA BUREAU OF STANDARDS  
 TBS/CDC 7(5811)  P3 
ii                                                                                              ©TBS 2019  – All rights reserved   
 
 
 
Foreword  
 
This Draft Tanzania Standard is being developed by the Industrial and Laboratory Chemicals 
Technical Committe e under supervision of the Chemical s Division Standards Committee and 
it is in accordance with the procedures of the Bureau.  
 
This second edition cancels and replaces the first edition (TZS 507: 1999 Sodium bicarbonate  
– Specification) , with changes  on test method for heavy metals.   
 
In reporting the re sult of a test or analysis made in accordance with this Tanzania Standard, if 
the final value, observed or calculated is to be rounded off, it shall be done in accordance with 
TZS 4 rounding  off numerical valu es.    
 DRAFT TANZANIA STANDARD                   TBS/CDC 7(5 811) P 3 
 
©TBS 1996 – All rights  reserved                                                                                               1  
 
Sodium bicarbonate – Specification  
 
 
1. Scope  
 
This Draft Tanzania S tandard prescribes the requirements and the methods  of sampling and 
test for sodium bicarbonate.   
 
This Standard does not cover  sodium bicarbonate  used directly as  baking powder  in food 
industry  which has been covered in TZS 244 1.  
 
2. Normative references  
 
<<<<<Not applicable>>>>>  
 
3. Terms and definitions  
 
<<<<<Not applicable>>>>>  
 
 
4. Requirements  
 
4.1 General requirements  
 
4.1.1 Grades   
 
The material shall be of the three su b-grades: 
 
a) Pure grade  – suitable for the fine chemical and pharmaceutical industry.  
 
b) Analytical reagent grade  – suitable as a reagent.   
 
c) Refined grade  – suitable for food industry . 
 
 
4.1.2 Description   
 
The material of the t hree grades shall be in the for m of small opaque, monoclinic crystals or 
as a white, minut ely crystalline powder free from dirt and other foreign matter.  
 
Pure grade suitable for manufacture of effervescent powders shall have particle size 
distribution as agreed to between the purchaser  and the supplier.  
 
4.2 Specific requirements  
 
The material  shall comply with requirements laid down in table 1 when tested in accordance 
with the methods prescribed in annex A. 
 
 
 
  
2                                                                                                ©TBS 2020 All rights reserved   
 
Table 1 – Requirements for sodium bicarbonate (clause 4.2) 
 
SL 
No 
 
 
 
 
 
 
(1) Characteristic  
 
 
 
 
 
 
 
(2) Requirement  Method of tes t 
(ref to clause 
numbers in 
annex A  
 
 
 
 
(6)  
Pure 
grade  
 
 
 
 
(3)  
Analytical 
reagent grade  
 
 
 
 
(4)  
Refined 
grade  
 
 
 
 
(5) 
 
 
1 
 
 
2  
 
3 
 
 
4 
 
 
5 
 
 
6 
 
7 
 
 
8 
 
 
9 
 
 
10  
 
 
11 
 
 
12  
 
 
13 
 
 
14 
 
 
15 
 
 
16   
 
Total alka linity (as NaHC O3), percent  
by mass, min  
 
pH, max 
 
Chlorides (as  Cl), per cent by mass, 
max  
 
Insoluble matter, per cent by mass, 
max 
 
Sulphate (as S O4), per cent by mass, 
max 
 
Iron (as Fe), per cent by mass, max  
 
Heavy metals (as Pb), parts per 
million (ppm) , max  
 
Arsenic (as As), parts p er million, 
max 
 
Ammonium comp ounds (as NH 4), 
parts per  million, max  
 
Phosphates (as P O4) per cent by 
mass, max  
 
Calcium and magnesium (as Ca) 
percent by mass,  max 
 
Copper (as Cu), parts per million, 
max 
 
Nitrates ( as N O3), per cent by mass, 
max 
 
Silicates ( as SiO 2), percent  by mass, 
max 
 
Potassi um (as K), per cent by mass, 
max 
 
Substances reducing iodine, percent  
by mass, max  
 
99.0 
 
 
8.6 
 
0.01 
 
 
0.5 
 
 
0.05 
 
 
0. 0015  
 
4 
 
 
1.5 
 
 
To pass 
test 
 
N/A 
 
 
N/A 
 
 
30 
 
 
N/A 
 
 
N/A 
 
 
N/A 
 
 
N/A  
 
99.0 
 
 
8.4 
 
0.001  
 
 
0.010  
 
 
0.003  
 
 
0.0005  
 
4 
 
 
0.4 
 
 
5 
 
 
0.0005  
 
 
0. 015  
 
 
0. 001 
 
 
0. 001  
 
 
0.005 
 
 
0.01 
 
 
0.006 5  
 
99.0 
 
 
8.6 
 
0.06 
 
 
0.100  
 
 
0.07 
 
 
0.004  
 
4 
 
 
1.5 
 
 
N/A 
 
 
N/A 
 
 
N/A 
 
 
 2 
 
 
N/A 
 
 
N/A 
 
 
N/A 
 
 
N/A  
 
A.2 
 
 
A.3 
 
A.4 
 
 
A.5 
 
 
A.6 
 
 
A.7 
 
A.8 
 
 
A.8 
 
 
A.9 
 
 
A.10 
 
 
A.11 
 
 
A.12 
 
 
A.13 
 
 
A.14 
 
 
A.15 
 
 
A.16 
 
Note:  
N/A = “Not applicable; stands for parameters which are not applicable  for particular grade  
 
  
©TBS 2020 – All rights reserved                                                                                              3 5 Packing and marking  
 
5.1 Packing  
The material shall be supplied in sound, cle an and dry container s or as agreed between the 
purchaser and the supplier p rovided that the minimum requirement is met.  
 
5.2 Labelling   
Each container  shall be securely closed, legibly and indelibly label  with the information  below  
either in English or K iswahili or in combination as agreed between the manufacturer and/or 
the supplier. Any other additional language is optional.  
 
a) Name and grade /use of the material  
b) Name of the manufacturer   
c) Recognize d trade -mark, if any  
d) Net content  
e) Date of manufacture  
f) Batch identification  
g) Instructions for safety  and storage  
 
 
 
6 Sampling   
 
Representative samples of the material shall be drawn and their conformity to that standard 
shall be determined in accordance with  the method prescribed in annex B.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
4                                                                                                ©TBS 2020 All rights reserved   
 
Annex A  
(Norm ative ) 
 
Analysis of sodium bicarbonate  
 
 
A.1 Quality  of reagents  
 
Unless specified otherwise , analytical  grade chemicals and d istilled water shall be  used in 
tests.  
 
 
A.2 Determi nation of total alkalinity   
 
A.2.1   Reagents  
 
A.2.1.1 Standard hydrochloric  acid – 1.0 M. 
 
A.2.1.2  Standard hydrochloric acid – 0.1 M  
 
A.2.1.2  Methyl orange or bromothymol blue indicator  
 
A.2.2  Procedur e   
 
Weigh  accurately 4.4  g of the material and diss olve in 100 mL of freshly b oiled and cooled 
water contained  in a conical  flask. Add 5 drops of the methyl orange or bromothymol blue 
indicator and 50 mL of   standard hydrochloric acid (1 .0 M).  Stir the contents thoroughly and 
further titrate with standar d hydrochloric acid ( 0.1 M) until the colour of the indicat or solution 
change s from yellow to pinkish orange.  Calculate the total volume i n terms of hydrochloric 
acid (1 M). 
          
A.2.3 Calculation  
                                                                                    8.4 VM  
Total alkalinity  (as NaHC O3), percent by mass    =  
                W 
 
 
where   
 
V = volume  in mL of standard hydrochloric acid ( l M) required for titration;  
 
M =   molarity of standard hydrochlori c acid used; and  
 
W = mass  in g of the material taken for the test.  
 
 
A.3 Dete rmination  of pH    
 
A.3.1  Methods   
 
The determination shall be carried out either by the electrometric method or the indicator 
method.  In case o f dispute, the electrometric method shall be conside red as the reference 
method.   
 
 
  
©TBS 2020 – All rights reserved                                                                                              5 A.3.2  Electrometric  metho d  
 
The determinatio n shall be made on I per cent (m/v solution by any pH metre with glass 
electrode  
 
A.3.3 Indicator method  
 
A.3.3.1  Reagents  
 
Bromothymol blue indicator – dissolve 0.1 g in 100 mL of rectified spirit .  
 
A.3.3.2  Procedure   
 
Weigh 1 g of  the material and di ssolve in 100 mL of water.  Take 10  mL of this solution in 
hard glass test -tube and add 0.5 mL of bromothymol blue indicator. Compare the colour 
produced with a series of buffer s olutions of known pH in the range 8.0 to 9.0.  Report as pH, 
the pH of the bu ffer solution which gives the closest match with the colour produced with the 
sample .  
 
A.3.4 Standard calibrated glass discs m ay also be used for the determinati on of pH.  
 
 
A.4   Determination of chlorides  
  
A.4.1 For pure  and refined grades   
  
A.4.1.1  Reagents   
 
A.4.1.1.1  Concentrated nitric acid  
 
A.4.1.1.2  Standard  silver nitrite solution  – 0.1 M  
 
A.4.1.1.3  Nitrobe nzene  
 
A.4.1.1.4   Standard ammonium thiocyanate solution – approximately 5 %. 
  
A.4.1.2  Procedure  
 
Weigh accurately abou t 20 g of the materi al, dissolve in water and neutralize with 
concentrated nitric acid and then add about 5 mL in excess. Boil the solution to expe l any 
dissolved carbon dioxide gas , cool and add 10 mL of standard silver nitrate solution.  Add 3 
mL of nitrobenzene , shake vigo rously and titrate with standard ammonium thiocyanate 
solution using the ammonium sulphate indicator.  
 
A 4.1 .3 Calculation   
                                                              3.547 ( 10 M1 – V M 2) 
Chlorides (as Cl) , percent b y mass =  
                                                                          W       
   
                where   
 
M1 = Molarity  of standard s ilver nitrate;    
 
V =   volume in mL of standard amm onium thiocyanate sol ution consumed in 
the titration;  
 
M2 =   molarity of standard ammonium  thiocyanate solution ; and    
 
 W =   mass in g of the material taken for the test.  
  
6                                                                                                ©TBS 2020 All rights reserved  A.4.2  For analytical  reagent grade 
 
A.4.2.1  Apparatus  
 
Nessler  cylinders – 100 mL capacity  
 
A.4.2.2  Reagents  
 
A-4.2.2.1  Concentrated  nitric acid – density 1 .400 
 
A.4.2.2.2 Silver nitrate solution  – approximately 4 percent  
 
A.4.2.2.3  Standard chloride solution  – Dissolve 1.649 g of s odium chloride in water and make 
up the volume to 10 00 mL.  Pipette out 10 mL from this solution and dilute w ith water to 1000 
mL. One millilitre  of the diluted solution is equivalent to 0.01 mg of chloride (as Cl).  
 
A.4.2.3  Procedure   
 
Dissolve 1.000 g of  the material in 30 mL of water and add slight exces s of concentrated nitric 
acid.  Boil the solution, cool a nd add 1 mL of silve r nitrate solution. Transfer into a Nessler 
cylinder and make up the volume to 100 mL mark with water . Carry out a control test  using 1 
mL of standard chloride solution and the sa me quantities of other reagents in the same total 
volume of the reaction mixt ure.  Compare the turbidity in both the cylinders after 5 minutes.  
 
A.4.2.4 The limit prescribed in table 1 shall be taken as n ot having been exceeded if the 
turbidity produced in  the test with the material is not grater than produced i n the control test.  
 
 
A.5 Determination of insoluble  matter  
  
A.5.1 Procedure   
 
Weigh  accurately about 10 g of the material, transfer it a 400 mL beaker, add about 200 mL of 
freshly boiled water and  boil the resulting solution for 15 minutes.  Filter any undissolved 
residue through a tared Gooch or a sintered glass crucible (G No. 4) and wash the residue 
free from soluble salts with water.  Collect the filtrate and washings in a one litre graduated 
flask and dilute to mark.  Preserve the solution so  obtain ed for the test unde r A.11.  Dry the 
crucible along with the residue to constant mass at 105 °C to 110°C.  
 
A.5.2 Calculation  
              M1 
Insoluble matter, per cent by mass =  100  
             M2 
 
where  
   M1 =   mass in g of the residue; and  
 
 M2 = mass in g of the mat erial take n for the test .  
 
 
 
 
A.6 Determination  of sulphates  
 
A.6.1 For pure and refined grades  
 
A.6.1.1 Reagents   
  
A.6.1.1. 1 Concentrated hydrochloric acid   
©TBS 2020 – All rights reserved                                                                                              7  
A.6.1.1.2  Barium chloride solution – approximately 10 per cent  
 
A.6.1.2   Procedure  
 
Dissolve 10 g to 15 g of the material, accurately weighed, in about 100 mL of water . Carefully 
add concentrated hydrochloric acid to mak e it acidic, and boil to drive off completely the 
carbon dioxide formed.  Cool and filter, if necessary, thro ugh a folded filter paper.  Wash the 
filter paper tho roughly with water, collecting the filtrate and washings in a 500-mL beaker.  
Dilute to 250 mL, boil and add 10 mL of hot barium chloride solution  to the hot solution.  Boil 
again for a few minutes.   Al low the contents of the beaker to stand for 4 hours and filter 
through a tared sintered glass crucible (G No. 4) or a Gooch crucible. Wash the prec ipitate 
with hot water till it is free from chloride s and dry to constant mass at 105°C to 110°C.  
 
A.6.1.3 Calculation    
                                                                 41.15 M1 
Sulphates (as S O4), percent by mass =   
     M  
      
where  
 
  M1 = mass in g of the precipi tate; and  
 
M = ma ss in g of the material taken for the test.  
 
A.6.2  For analytical reagent grade 
 
A.6.2.1  Apparatus  
 
Nessler cylinder s – 100 mL capacity  
 
A.6.2.2 Reagents   
 
A.6.2.2.1  Concentrated hydrochloric acid   
 
A.6.2.2.2  Standard sulphate solution  – Dissolve 0.181 4 g of potassium sulphate in wa ter and 
make up the volume t o 1000 mL.  One mill ilitre of this solution is equivalent to 0.1 mg of 
sulphate (as S O4).  
 
A.6.2.3 Procedure  
 
Dissolve 2 000 g of the material in 2 0 mL of water, add 5 mL of concentrated hydrochloric  acid 
and evaporate to dryness on a water -bath.  Dissolve  the residue in 20 mL of the water and 
add a few drops of concentrated hydrochloric acid and 2 mL of barium chloride solution.   
Transfer to a Ness ler cylinder and dilute to mark.   Carry out a contr ol test in another Nessler 
cylinder using 0.6 mL of stand ard sulphate solutio n in place of the material and the same 
quantities of other reagents in the same total volume of the reaction mixture.  
 
The li mit prescribed in table 1 shall be taken as not having exceeded  if the turbidity in the test 
with the materia l is not grater than  that in the control test.  
 
A.7 Test  for iron  
 
A.7.1 Apparatus  
 
Nessler cylinders  
 
A.7.2 Reagents   
 
A.7.2.1  Concentrated  hydrochloric acid   
8                                                                                                ©TBS 2020 All rights reserved   
A.7.2.2 Ammonium  persulphate  
 
A.7.2. 3 Butanolic  potassium thiocyanate solution  – Dissolve 10 g of potassium thioc yanate in 
10 mL of water.  Add sufficient n -butanol to make up to 100 mL and shake vigorously until the 
solution is clear.  
 
A.7.2.4 Standard iron solution  – Dissolve 0.702 g of fe rrous ammonium sulphate          
(FeSO4.  6H 2O) in 10 mL of dilute sulfuric  acid (10 percent v/v) and dilute with water to 1 000 
mL.  Dilute 10 mL of this solution to 100 mL. One millilitre  of the diluted solution is equivalent 
to 0.01 mg of iron (as Fe).  
 
A.7.3 Procedure  
 
Dissolve 10 00 g of the material in 25  mL of water and ne utralize wit h 5 mL of concentrated 
hydrochloric.  Add 30 mg of ammonium persulphate and boil to oxidize the iron.  Cool and 
transfe r completely into a Nessler cylinder.  Ad d 15 mL of butanolic and allow it to separate.  
Carry out a control t est in another Nessler cyli nder using 1.5 mL of the standard iron solution 
for the pure grade, 0.5 mL for the analytical reagent grade and 4 mL for the refined grade 
respectively in place of the mat erial and the same quantities of other reagents in the sam e 
total volume of the react ion mixture.  Compare the colour produced.  
 
The limit prescribed in table 1 shall be taken as not having been exceeded if the intensity of 
colour produced in the test with  the material is not grater than that produced in the cont rol 
test. 
 
 
A.8 Test for heavy metals  
 
A.8.1 Apparatus : 
A.8.1.1 Microwave digester,  
A.8.1.2 Nessler cylinder 50 mL,  
A.8.1.3 Filter + Funnel  
 
A.8.2 Reagents:  
A.8.2.1 Conc hydrochloric acid, HCl,  
A.8.2.2 Hydrogen peroxide H 2O2 - 30%w/v  
 
A.8.3 Procedures.  
Weigh 0.1 - 0.5g of sample  into a digestion vessel and add 6 mL of conc . HCl and 1 mL of 
Hydrogen peroxide swirl gently to mix, place the mixture in to microwave digester and digest 
till it is complete . 
Cool the sample to room temperature; d ilute the sample w ith not more than 20 mL of 
deionized water, filter the resulting solution into Nessler’s cylinder and add water to make the 
final volume to 50 mL. 
 
A.8.4 Determination  
Determine heavy metals  content s using ICP.   
 
A.9 Test ammonium compounds  
 
A .10.1 Appara tus  
 
Nessler cylinders – 50 mL capacity  
 
A.9.2 Reagents   
  
©TBS 2020 – All rights reserved                                                                                              9 A.9.2.1 Sodium hydroxide solution – 10 %  
 
A.9.2.2 Nessler solution  – Dissolve 10 g of potassium iodide in 10 mL of ammonia -free water 
and add to it slowly, while stirring, saturated mercuric chlor ide solution until a s light 
permanent precipitate is formed.  Add 30 g of potassium hydroxide and, when it has 
dissolved, add 1 mL more of mercuri c chloride solution and dilute to 200 mL with ammoni a-
free water.  Allow to settle overnight, decant the clear  solution and keep it in a bottle closed 
with a well-fitting  rubber stopper.  
 
A.9.2.3 Standard ammonium chloride solution  – Dissolve 0.296 g of am monium chloride 
(NH 4CL) in water and dilute to 100 mL, dilute 10 mL of this solution to 1  000 mL.  One millili tre 
of this diluted so lution is equivalent to 0.001 mg of ammonium (as NH 4). 
 
A.9.3 Procedure  
 
A.9. 3.1  For pure grade – Dissolve 1.0 g of the mat erial in 10 mL of water, add 20 mL of 
sodium hydroxi de solution and warm the reaction mixture.  
 
A.9.3.2 For analytical reagent grade – Dissolve 2.0 g of the material  in 45 mL of water and 
add 15 mL of sodium hydroxide.  Filter through a sintered glass cruc ible, previously washed 
with sodium hydroxide soluti on.  Take 6 mL of the filtrate, dilute with water to 50 mL and add 
2 mL of Nessler solution.   In a control test, having an equal volume of the solution and 
containing 1 mL of standard ammonium chloride s olution and 1.5 mL of sodium hydroxi de 
solution, add  2 mL of Nessler solution.  
 
The limit prescribed in table  1 shall be taken a s not having been exceeded if the intensity of 
colour produced in that test with the material is not greater than that produced in the control 
test.  
 
A.10  Test for phosphates  
 
A.10.1 Apparatus   
 
Nessler cylinders  – 50 mL capacity .  
 
A.10.2 Reagents   
 
A.10 .2.1 Dilute sulfuric  acid – approximately 2.5 M and 0.5 M . 
 
A.10 .2.2 Phosphate  reagent A  – Dissolve without heating 5 g of powdered ammonium  
molybdate in 100 of dilute sulfuric  acid (0.5  M). 
 
 A.10 .2.3 Phosphate reagent B  – Dissolve w ithout heating 0.2 g of methyl -p-aminophenol 
sulphate ( metol) and  20 g of sodium metabisulphite in 100 mL of water.  
 
 A.10 .2.4 Standard  phosphate s olution  – Dissolve 0.286 0 g of potassium dihydrogen 
phosphate (K H2PO 4) in wate r   and make up the volume to 1  000 mL.  Dilute 10  mL of this 
solution to 1 00 mL with water.  One millilit re of the diluted solution is equivalent to 0.02 mg of 
phosphate (as P O4).  Keep the solution in a waxed bottle.  
 
A.10 .3 Procedure  
 
Dissolve 2.00 g of the material in 20 mL of water, add 7 mL of dilut e sulfuric  acid (2.5 M ) and 
1 mL each of phosphate reagents A and B.  Dilute with water to 50 mL and place in water 
bath at 60° C for 10 minutes.  Carry out a control test using 0. 5 mL of standard phosphate 
solution in place of the material  and the same qu antities of other reagents in the same total 
volume of the reaction.  
  
10                                                                                                ©TBS 2020 All rights reserved  The limit prescribed in Table 1 shall be taken as not havi ng been exceeded if the intensity of 
colour produced  in the test with the material is not greater than that prod uced in the cont rol 
test. 
 
 
A.11  Determination  of calcium and magnesium  
 
A.11 .1 Reagents   
 
A.11 .1.1 Standard  calcium solution  – Weigh 1.00 g of calcium carbonate dried at 120° C and  
dissolve it in the minimum quantity of dilute hydrochloric acid.  Dilute th e solution to on e litre 
in a graduated flask.  One millilit re of this solution is equivalent to 0.4008  mg of calcium (as 
Ca). 
 
A.11 .1.2 Standard  EDTA solution – Dissolve 3.72 g of di sodium ethylen e diamine tetracetate 
dehydrate in water and dilute in a gra duated flask to one litre.  The solution shall be 
standardized frequently against the standard calcium solution, follo wing the procedure given 
in A.11.2.1. 
  
A.11 .1.3 Briochrome black T indicator solution  – Dissolve 0.1 g of the dye in 20 mL of rectified 
spirit.  This sol ution shall be prepared fresh every week .  
  
A.11 .1.4 Ammonium chloride  – ammonium hydroxide buffer solution  – Dissolve 67.5 g o f 
ammonium chloride in a mixture of 570 mL of ammoni um hydroxide (sp gr 0.90) and 250 mL 
of water.  Also dissolv e separately a m ixture of 0.931 g of disodium ethylene diamine 
tetraacetate  dehydrate and 0.616 g of magnesium sulphate (MgS O4 7H2O) in about 50  mL of 
water.  Mix the two solutions and dilute to o ne litre.  
 
NOTE  – Five millilitre s of the buffer solution ad ded 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 indicato r. 
 
A.11 .2 Procedure  
 
A.11 .2.1 Standardization of ED TA solution  – Transfer 25 mL of standard calcium solution in to 
a conical fla sk, add 25 mL of wat er, 10 mL of ammonium chloride -ammonium hydroxide 
buffer solution, 5 drops of the eriochrome black T indicat or solution and titrate against the 
EDTA solution to  pure blue end point.  
 
A.11 .2.2 Titrate 25 mL of the buffer solution with EDTA solution using er iochrome black T 
indicator. Subtract the buffer correction for 10 mL (usually, it will be 0.1  mL) from the r eading 
obtained in A.11.2.1 and not the final titre value.  Calculate the calcium equivalent of 1 mL of 
EDTA sol ution (say A).  
 
A.11 .2.3 Transfer exactly  100 mL of solution preserved in A. 5.1 into a 250 mL conical flask.  
Add 20 mL of ammonium hydroxide bu ffer solution, 5 drops of erochrome black T indicato r 
solution and titrate against standard EDTA   solution till  wine red colour  of the solution 
changes to pure blue end -point.  Note the volume of EDTA solution used in the titration.  
 
A.11 .3 Calculation   
              AV  
Calcium and magne sium (as Ca), pe rcent by mass =        100  
               M 
Where,   
A = calcium  equivalent  calculated in g o f 1 mL of EDTA solution in A.11.2.2; 
V =   volume in mL of standard EDTA solution used  in A.11. 2.3; and  
M =   mass in g of the material taken for the test in A.5.1. 
 
  
©TBS 2020 – All rights reserved                                                                                              11 A.12  Test for copper  
 
A.12 .1 Apparatus   
 
Nessler cyli nders – 50 mL capacity .  
 
A.12 .2 Reagents    
 
A.12 .2.1 Concentrated hydrochloric acid  
 
A.12 .2.2 Concentrated  nitric acid  
 
A.12 .2.3 Citric  acid 
 
A.12 .2.4 Dilute  ammonium hydroxide – approximately 5 M. 
 
A.12 .2.5 Sodium diethyl dithiocarbamate solution  – Dissolve 1.0 g of sod ium 
diethyldithiocarbamate in 1 000 mL of copper free water. Filter and keep in an amber bottle 
and protect from strong light.   
 
A.12 .2.6 Standard cooper solution  – Dissolve 0.392 8 g of copper sulphate pentahydrate in 
copper free water and  make up the volu me to 1 000 mL.  Take 100 mL of this  solution and 
dilute again to 1 000 mL.  One millilitre of the diluted solution contains 0.01  mg of copper (as 
Ca). 
 
A.12 .2.7 Chloroform                                                                         
 
A.12 .3 Proced ure  
 
Weigh 1.000 g of the material and dissolve it in about  50 mL of water. Neutralize with 
concentrated hydrochloric acid and  add 4 to 5 drops of concentrated nitric acid.  Boil  and cool.  
Add 1 g of citric acid and adjust p H to 9 by add ing dilute ammoni um hydroxide. Add 10 mL of 
sodium diethyldithiocarbamate solution and extract the yellow colour produced four times with 
2.5 mL portions of chloroform.  Collect the chloroform ext racts and filter through a dry filter 
into a Nessler cylinde r.   Carry out a control test using 3 mL of standard copper solution in 
place of the material.  
 
The material shall be considered not to have exc eeded the limit prescribed in table 1 if the 
intensi ty of the colour produced with the material is not greater t han that produced  in the 
control test.  
 
 
A.13    Test for nitrate  
 
A.13 .1   Reagents  
 
A.13 .1.1 Dilute  sulfuric  acid – approximately  2.5 M. 
 
A.13.1.2 Concentrated  hydrochloric acid 
 
A.13 .1.3 Potassium nitrate solution – 0.001 M .   
 
A.13 .1.4 Concentrated sulfuric  acid  
 
A.13 .1.5 Standard indigo carmine solution – Dissolve 0.20 g of indigo carmine in 400  mL of 
diluted sulfuric  acid and add 20 mL of concentrated hydrochloric acid and sufficient dil ute 
sulfuric  acid to produce 1 000 mL. Standardize the solution so that 10 mL added to 3.3 mL of 
potassium nitrate solution is just decolourized on adding 13 mL of concentrated sulfuric  acid 
and heating to boiling.  One millilitr e of this solution is equi valent to 0.002 mg of nitrate (as 
NO3).  
12                                                                                                ©TBS 2020 All rights reserved   
A.13 .2 Procedure   
 
Disso lve 2.000 g of the material in 10 mL of dilute sulfuric  acid, add 1 mL of standard indigo 
carmine solution followed by 10  mL of concentrat ed sulfuric  acid and heat to boiling.  
 
 A.13 .2.1 The limit prescribed in table 1 shall be taken as not having been ex ceed ed if the 
blue colour produced in the test with the material does not entirely disappear.  
 
 
A.14  Test for silicates   
 
A.14 .1 Apparatu s    
 
Nessler cylinders – 50 mL capacity .  
 
A.14 .2 Reagents   
 
A.14 .2.1 Dilute sulfuric  acid – approximately 0.5 M . 
 
A.14.2.2 Amm onium molybdate solution  – Dissolve 10 g of ammonium molybdate in 1 00 mL 
of dilute sulfuric  acid ( 0.5 M).  
 
A.14 .2.3 Sodium citrate solution  – Dissolve 8 g of sodium citrate Na 3C6H5O7.2H2O) in 100 mL 
of water.  
 
A.14 .2.4 Potassium  metabisulphite so lution  – Dissolve 20 g of potassium metabisulphite and 
1 g of hydroquinone in 100 mL of water.  
 
A.14 .2.5 Anhydrous sodium carbonate  
 
A.14.2.6 Standard silicate  solution  – Fuse 0.100 g of pure, precipitated silica with anhydrous 
sodium carbonate in a plati num cruc ible and leach the melt with water, neutralize with dilute  
sulfuric  acid and dilute to 1 000   mL.  Dilut e 10 mL of this soluti on to 100 mL. One m illilitre of 
the diluted solution  contains 0.01 mg of silica (as Si O2).  Store in a polyethylene bottle . 
 
A.14 .3 Procedure   
 
Dissolve 2. 00 g of the material in 20 mL of water in a platinum dish, neutralize with about 10 
mL of dilute sulfuric  acid, add  2 mL of the acid in excess and dilut e to 50 mL.  Transfer 10 mL 
of this solution into a Nessler cylinder. A dd 1 mL of dilute sulfuric  acid and 5 mL of ammonium 
molbdate solution.  Allow to stand for 5 mL minutes and then add 5 mL of sodium  citrate 
solution followed by 5 of potassium metabis ulphite solution. Dilute to 50 mL. Carry out a 
control test in another N essle r cylinder using 2 mL of standard silicate solution in place of the 
sample and the same quantities of other reagents in the sam e total  volume of the reac tion 
mixture.  Stand  both the cylinders in a boiling water bath for 5 minutes, cool and compare th e 
colour prod uced in the two cylinders after 5 minutes.  
 
The limit prescribed for  silicates shall be taken as not having been exceed ed if any blue 
colour produced in the test with the material is not deeper than that  produced in the control  
test. 
 
A.15  Determin ation of potassium  
 
A.15 .1 Apparatus  
 
Flame photometer  – Equipped  with interference filter.   
 
A.15 .2 Reagents     
©TBS 2020 – All rights reserved                                                                                              13  
A.15 .2.1 Standard potassium solution  – Weigh exactly 1 g of pota ssium chloride, dissolve in 
distilled water and dilute to one litre with  distilled water in a measuring fla sk.  This solution 
contains 0.1 g KC l per 100 mL. 
 
A.15 .2.2 Calibration graph – Take 10 , 20, 40, 60 and 80 mL of standard potassium solution 
(see A.15.2.1) and dilute to 100 mL with distilled water  in different measuring flasks.  Each 
flask now contains 0.01, 0 .02, 0.04, 0.06 and 0.08 g KC l per 100 mL. Use these dilute 
solutions to obtain a correspond ing galvanometer reading as g iven in A.15.3.1 and pl ot the 
concentration against galvanometer reading in a rectangular co -ordinat ion graph . Draw a 
smooth curve over the points which gives  a calibrat ion graph in the range 0.01 to 0.1 per cent 
KCl. 
 
A.15 .2.3 Sample solution – Dissolve approximately 10 g of the  sample in minimum quantity of 
distilled water and dilute to 100 mL of measur ing flask with distilled water.  
 
A.15 .3 Procedure  
 
A.15 .3.1 Use a flame photometer equipped with atomizer, burner and optical selective device 
consisting of reflectors, lenses an d diaphragms; and measuring instrument consisting of 
photocell, amplifie r and  sensitive galvanometer. The galvanometer scale ranges from 0 to 100 
divisions which measure  the intensity of the radiation tra nsmitted by the element.  
 
A.15 .3.2 Insert the potass ium filter corresponding to wavelength 767 nm, light  the burner fed 
by illuminating gas (laboratory gas ), adjust  the specified air pressure between 0.5 to 0.6 
kg/cm2 and maintain the above air pressure co nstant, such that flame is non -luminous by 
turning t he control knob.  First spray distilled water and adjust the pointer to zero in 
galvanometer scale by zero adjustment knob. Then spray the KC l standard solution ( A.15.2.1) 
and adjust the deflection to max imum 100 by using sensitivity control knob.  Again,  spray 
water to see that the pointer comes to zero; then spr ay a standard  solution to indicate 100. 
Repeat till water reads zero and standard solution reads 100 with same adjustment during 
both operations.  A reading zero by water and  with the  same adjustmen t 100 by standard 
solution indicate that the instrument has been made re ady for measurement.  
 
A.15 .3.3 Without altering the earlier adjustment of the instrument , spray various dil uted 
solutions prepared i n A.15.2.2 and obtain a calibration graph in the ran ge 0.01 percent KC l.  
After washing with distilled water, spray the samp le so lution and obtain the galvanometer 
reading.  From the graph, read out the corresponding concentration of KC l in the solution (s ay 
A). 
 
A.15 .4 Calculation   
      A 
Potassium, per cent by mass   =   52.35  
                                                                 M 
where  
 
A = concentration  of KC l in the sample solution ; and   
 
M = mass of dried sample taken for the test.  
 
 
A.16 Test for substances reducing iodine  
 
A.16 .1 Reagents   
 
A.16 .1.1 Starch solution – Triturate 5 g of starch and 0.01 g of  merc uric iodide  with 30 mL of 
water in mortar.  Pour the resulting paste into one litre of boiling water and boil for 3 minutes. 
Allow the solution to cool and decant off the clear li quid.  
 
A.16 .1.2 Standard i odine solution – 0.005 M.   
14                                                                                                ©TBS 2020 All rights reserved   
A.16 .2 Procedure   
 
Disso lve 10 g of the material in 200 mL of freshly boiled and cooled water. Add 2 mL of starch 
solution and titrate with standard io dine solution.  
 
The material shall be taken to have passed the test if not more than 0.5 mL of iodine solution 
is required t o pro duce a permanent blue colour . 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
©TBS 2020 – All rights reserved                                                                                              15  
 
 
 
Annex B  
(Normative ) 
 
Sampling of sodium bicarbona te 
 
 
B.1 General  requirements of sampling  
 
In drawin g, preparing, storing and handling test samples, the following precautio ns a nd 
directions shall be observed:  
 
B.1.1 Precautions shall be taken to protect the sample, the material being sampled, the 
sampli ng instrument and the containers for samples from ad ventitious contamination.  
 
B.1.2 To draw a representative sample, the co ntent s of each container selected for sampling 
shall be    mixed as thoroughly as possible by suitable means.  
 
B.1.3 The sample sha ll be placed in suitable, clean, dry and air -tight g lass or other suitable 
containers on which the material has no action.  
 
B.1.4   Each sample container shall be sealed air -tight after filling and marked with full details 
of sampling, the date of samplin g and the year of manufacture of the material.  
 
B.1.5 Sample s shall  not be taken in an exposed place.  
 
 
B.2 Scale of samplin g  
 
B.2.1 Lot – All the containers in a single consignment of the material drawn from a single 
batch of manufacture shall constitute  a lot.  If a consignment is declared or known to co nsist 
of different batches of manufacture, the containers belonging to t he sa me batch shall be 
grouped together and each such group shall constitute a separate lot.  
 
Samples shall be tested form each lot for ascertaining conformity of the material to the 
requirements of the specification . 
 
B.2.2 The number ( n) of containers to  be chosen from a lot shall depend on the size of the lot 
(N) and shall  be in accordance with columns 1  and 2 of table 2.  
 
 
Table 2 – Scale of sampling  
 
  
 
Lot size  
 
N 
(1)  
Number of  containers to be 
selected  
n 
(2) 
 
Up to 50  
51 to 200  
201 to 400  
401 to 650 
651 to 1000   
3 
4 
5 
6 
7  
16                                                                                                ©TBS 2020 All rights reserved   
 
 
B.2.3 These containers shall be selected at random from the lot and in order to ensure the 
randomness  of selection random sampling procedures may be foll owed.  
 
 
B.3 Test samples and referee sample  
 
B.3.1 Preparation of test s ample s 
  
B.3.1.1  Draw with an appropriate sampling instrument a small portion of the material from 
different parts of each container  selected.  The total quantity of the material drawn  from each 
container shall be sufficient to conduct the tests for all th e cha racteristics give n under 3 and 
shall not exceed 1 kg.  
 
B.3.1.2  Thoroughly mix all portions of the material drawn from the same  container.  Out of 
these portions a small but equal  quantity shall be taken  from each selected container and   
shall be wel l mixed up together so as  to form a composite sa mple weighing not less  than 60 0 
g. This composite  sample shall  be divided into three  equal parts , one  for the purchaser, 
another for the  supplier and the third to be used as  referee sample.  
 
B.3.1.3  The remai ning portion of the material from each container (after a small quantity 
needed for the formation  of composite sample has been taken ) shall be divide d into three 
equal parts, each part  weighing not less than 100 g.  These parts shall be immediately 
transfe rred to thoroughly dried bottles which are then sealed air -tight with stoppers and 
labelled with all the particu lars of sampling giv en under B. 1.4 The material in each such 
sealed bott le shall constitute an individual test s ample.  These individual sample s shall be 
separated into three identical sets of samples in such a way that each set has an individual 
test sample representing each  container selected, one of these three sets shall b e sent to the 
purchaser, another to the supplier and third shall be used  as referee sample.  
 
B.3.2 Referee sample  
 
The referee sample shall consist of the composite sample (see B. 3.1.2) and a set of indiv idual 
sample s (see B.3.1.3) marked for this purpose and shall bear the seals of the purchaser and 
the supplier. These shall be ke pt at a place agreed to between the purchaser and the supplier 
and shall be used in case of dispute between the two.  
 
 
B.4 Numb er of tests  
 
B.4.1 Tests for the determination of to tal alkalinity shall be conducted on each of the 
individual samples for all the three grades.  For refined grade, tests for heavy metals and 
arsenic also shall be conducted on each of the individual sampl es. 
    
B.4.2   Test for the remaining characteristi cs shall be conducted on the composite sample . 
 
 
B.5 Criterion for confo rmity   
  
B.5.1   For individual sample  
 
B.5.1.1  For total alkali nity  
 
The test results for total alkalinity shall be recorded and t he mean and the range for these test 
results shall b e calculated as follows : 
 
  Mean (X) = Sum of the test results divided by th e number of test results   
©TBS 2020 – All rights reserved                                                                                              17  
  (R) = The difference  between the maximum and the minimum values  
of the test results  and t he value  of expression ( X – 0.6R) shall  be 
calculated.  If t he value of this expression is equal to or greater than 
the limit specif ied for the relevant grade in table 1, the lot shall be 
declared to have satisfied the requirements for the characteristic.  
 
 B.5.1. 2 For heavy metal and arsenic   
 
The lot shall be dec lared as conforming to the requirements for these characteristics if eac h of 
the samples satisfies the test laid down in A.8 and A.8. 
 
B.5.2   For composite sample  
 
The test results on the composite sampl e shall meet the corresponding requirements 
specifie d in table 1.  
 
B.5.3   A lot shall be declared as c onforming to the spe cification i f it satisfies the requirements 
for each of the characteristics listed in table 1.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
18                                                                                                ©TBS 2020 All rights reserved   
 
 
 TBS/CDC 7(5811)  
 
 
©TBS 2020 – All rights reserved