KENYA STANDARD  DKS 2927 :2020  
ICS ##.### 
First  Edition  
  
 © KEBS yyyy  
 Industrial Solvents and Chemicals  —
Sodium bicarbonate  — Specification  
 
 
 
 
 
 
 
 
ii © KEBS 2020  – All rights reserved  
 TECHNICAL COMMITTEE REPRESENTATION  
The following organizations were represented on the Technical Committee:  
University of Nairobi  
Government Chemist  
MOTIHUD &PW -Materials Divis ion. 
Agro Chemical and Food Company  
Spectre International  
Associated Battery Manufacturers  
KIRDI  
KOKO Networks  
Consumer Information Network  
Kenya Revenue Authority  
ABIB Chemicals  
Kenya Association of Manufacturers  
Kenya Bureau of Standards -  Secretariat  
REVISION OF KENYA STANDARDS  
In order to keep abreast of progress in industry, Kenya Standards shall be regularly reviewed.  Suggestions for 
improvements to published standards, addressed to the Managing Director, Kenya Bureau of Standards, are 
welcome.  
© Ken ya Bureau of Standards, 2020  
Copyright. Users are reminded that by virtue of Section 25 of the Copyright Act, C ap. 130 of 2001 of  the Laws of Kenya, copyright subsists 
in all Kenya Standards and except as provided under Section 25 of this Act, no Kenya Sta ndard produced by Kenya Bureau of Standards 
may be reproduced, stored in a retrieval system in any form or tran smitted by any means without prior permission in writing from the 
Managing Director.   KENYA STANDARD  DKS 2927 :2020  
  ICS ##.###  
First  Edition  
 
  Industrial Solvents and Chemicals  —Sodium 
bicarbonate  — Specification  
 
Kenya Bureau of Standards,  Popo Road, Off Mombasa Road,  
P.O. Box 54974 - 00200,  Nairobi, Kenya  
 +254 020 6948000, + 254 722202137, + 254 734600471  
 info@kebs.org  
 @KEBS_ke  
 kenya bureau of standards (kebs)  
  
 
iv © KEBS 2020  – All rights reserved  
 Foreword  
This Kenya Standard was prepared by the Industrial solvents and Chemicals Technical Committee under the 
guidance of the Standards Projects Committee, and it is in accordance with the procedures of the Kenya Bureau 
of Standards  
During th e preparation of this standard, reference was made to the fo llowing document (s):  
IS 2124:2000 - Sodium bicarbonate - specification  
ISO 740 - Sodium carbonate for industrial use - Determination of  total soluble alkalinity - Titrimetric method  
ISO 746 - Sodium  carbonate for industrial use - Determination of  matter insoluble in water at 500C  
Acknowledgement is hereby made for the assistance derived from this (these) source (s)DKS 2927 : 2020    
 
© KEBS yyyy– All rights reserved   
 Industrial Solvents and Chemicals —Sodium bicarbonate — 
Specification  
1 Scope  
This st andard prescribes the requirements, methods of test and sampling for sodium bicarbonate . 
2 Normative refe rences  
There are no normative references in this document.  
3 Terms and definitions  
For the purposes of this document, the following terms and definiti ons apply.  
3.1  
Sodium bicarbonate   
Is a white solid that is crystalline but often appear as a fine powder with a chemical formula NaHCO 3. 
4 Grades   
4.1 There shall be three grades of the material, namely, Pure, Analytical Reagent and Technical  
4.1.2 Pure  Grade — Suitable for the fine chemic al, food application and pharmaceutical industry  
4.1.3 Analytical Reagent Grade —Suitable as a reagent.  
4.1.4 Technical Grade —Suitable for animal feed and detergent application  
5 Requirements  
5.1  Physical Requirement  — The material of all the three grades shall be in the form of small, opaque, 
monoclinic crystals or as a white powder, free from dirt and other foreign matter.  
5.1.1The pure grade material suitable for the manufacture of effervescent powders shall have the particle size 
distribution as agreed to between the purchaser and the supplier.  
5.1.2The material, when tested according to the methods prescribed in Annex es A to P, shall also comply with 
the requirements specified in Table 1.  
5.4 Chemical Requirement  — The material shall comply with the chemical p roperties specified in Table  1 when 
tested according to the method s prescribed in Annexures of this specification.   
 
6 Packaging and Marking  
6.1 Packaging — the material shall be packed in air -tight and moist ure proof containers.  
 KENYA STANDARD  DKS 2927 :2020  
  ICS ##.###  
First  Edition  
 
  6.2 Marking — When supplied in packages, each package shall be securely closed and marked indelibly with 
the following information:   
 (i) Name and grade of the material;  
(ii) Net weight of the content of the package or c ontainer;  
(iii) Manufacturer’s name and/or recognized trade mark if any;  
iv)  Batch/lot number;  
(iv) Date of manufacture/ expiry; and  
  v)  Country of origin.  
When supplied in bulk, a good sized metallic or cardboard label bearing the above information printed with 
suitable paint or ink shall be conspicuously displayed on the carrier and also placed inside.  
 
 
7 Sampling and size sample  
7.1 Sampling  
To test for t he compliance of sodium bicarbonate to the requirements of this standard, a sample of about 500g 
shall be t aken and stored in an air -tight container.  
The method of drawing representative samples of the material from the containers shall be as prescribed in  
Annex  P 
Caution:  in taking samples from a container or package, care shall be taken to exclude portions wh ere caking 
is noticeable (due to absorption of moisture and carbon dioxide). This may be done by removing from the top 
about 20cm of the material in the container and  then taking out sample from the center of the remaining portion.  
 
 
 
 
 
 
 
 
 
 
 
   
iv © KEBS 2020  – All rights reserved  
  
 
 
 
 
TABLE 1.  Requirements for Sodium Bicarbonate  
 
SL 
NO.  
CHARACTERISTICS  Requirements  
 
 METHOD OF TEST  
 
Pure 
Grade  Analytical  
Grade  Technical  
Grade  
 
1  
2  
3   
4 Annex  
i) Total alkalinity (as 
NaHCO 3) percent by mass, 
Min  
99.0 99.8  
98.0 A 
ii Insoluble matte r, percent by 
mass, Max   
0.05 0.010   
0.100  B 
 
iii) pH (1 percent aqueous 
solution), Max   
8.6 8.4  
8.8 pH meter  
iv) Sulphates (as SO 4), 
percent by mass, Max.   
0.05 0.003   
0.07 C 
 
v) Iron (as Fe), percent by 
mass, Max.   
0.0015  0.0005   
0.004  D 
vi) Heavy m etals (as Pb), parts 
per million, Max   0.001   E 
 
vii) Ammonium compounds (as 
NH 4), parts per million, 
Max.   
To pass 
test 5  
A13 F 
 
viii) Chlorides (as Cl-), percent 
by mass, Max   
0.01 0.001   
0.06 G 
 
ix) Substances reducing 
iodine, percent by mass, 
Max - Pass  - H 
 
x) Phosphates (as PO 4). 
percent by mass, Max  - 0.0005  - J 
 
xi) Calcium and magnesium 
(as Ca), percent by mass, 
Max  0.015   K 
 
xii) Nitrates (as NO 3), percent 
by mass, Max   0.001   L 
 
xiii) Potassium (as K), percent 
by mass, Max   0.01  M 
xv) Copper (as Cu), parts per 
million, Max  30 - 30 N KENYA STANDARD  DKS 2927 :2020  
  ICS ##.###  
First  Edition  
 
  nnex  A 
(normative)  
 
Determination of total alkalinity  
A.1 General  
The total alkalinity of a processing solution is defined as the millilitres of standardized 0.1 N sulfuric acid required 
to adjust a speci fied volume of processing solution to pH 4.3  
A1.1  Reagents   
A1.1 .1 Standard Hydrochloric Acid 1.0 N.  
A1.1.2 Standard Hydrochloric Acid 0.1 N  
A1.1.3  Methyl Orange or Bromothymol Blue Indicator  
A.2. Procedure  
Weigh accurately 4.4 g of the material and diss olve in 100 ml of freshly boiled and cooled water in a 250ml 
conica l flask. Add 5 drops of the methyl orange or bromothymol blue indicator and 50 ml of standard hydrochloric 
acid (1 N). Stir the contents thoroughly and further titrate with standard hydroch loric acid (0.1 N) until the colour 
of the indicator solution chang es from orange to red (blue to green in case of bromothymol blue). Calculate the 
total volume in terms of hydrochloric acid (1 N).  
A.3 Calculation  
Total alkalinity (as NaHCO3,), percent by  mass=   
 
8.4𝑉𝑁
𝑀 
Where,  
v = volume in ml of standard hydrochlori c acid (1N) required for titration   
vi © KEBS 2020  – All rights reserved  
 where, V= 50ml 1N HCL + (Titer Value of 0.1N HCL X0.1)  
N = normality of standard hydrochloric acid used, and  
M= mass in g of the material taken for th e test.  KENYA STANDARD  DKS 2927 :2020  
  ICS ##.###  
First  Edition  
 
  Annex  B 
(normative)  
 
Determination of matter insoluble in wate r at 50oC 
B.1Principle  
Dissolution of a test portion and filtration of the solution through a tared filter. Drying of the residue and weighing.  
B.2Procedure  
Weigh accurately about 10 g of the material, transfer it to 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 f rom soluble salts with water. Collect the filtrate and 
washings in a one-litre graduated flask and dilute to mark. Preserve the solution so obtained for the test under 
Annex K. Dry the crucible along with the residue to constant mass at 105 to 110°C.  
B.3Ca lculation  
The matter insoluble in water at 50 0C, expressed as a per centage by mass, is given by the formula  
𝑀1
𝑀0×100 
Where;  
M0=the mass, in grams, of the test portion;  
M1=the mass, in grams, of the filtered and dried insoluble matter.   
viii © KEBS 2020  – All rights reserved  
 Alternate method: Determination of matter insoluble in water using filter 
membrane under Vaccum  
B.1a . Apparatus  
0.45micron  cellulose filter membrane  
Membrane filter assembly  
Vaccum pump  
Oven  
Dessicator  
B.2a. Procedure  
Weigh accurately 5g of the sample. Transfer it into a 400ml beaker, add about 200ml of distilled water and boil 
the solution of about 10min and filter the solut ion through a weighed 0.45 microns cellulose filter membrane, 
using a vaccum pump. Transfer any insoluble matter into the filter assembly with a jet of distilled water. Wash 
the residue five times with 5ml portions of distilled water at room temperature. D ry the filter membrane in an 
oven at 50oC for 1hr, cool in desiccator and weigh.  
B.3a. Calculati on 
Matter insoluble in water, %by mass =   
𝑀1×100
𝑀2 
Where ; 
M1 = mass in grams of the residue; and  
M2= mass in grams of the sample taken for the test.  
 KENYA STANDARD  DKS 2927 :2020  
  ICS ##.###  
First  Edition  
 
  Anne x C 
(normative)  
Determination of Sulphates  
C.1.0 For technical grade  
C.1.0.1 Sodium bicarbonate, an alytical reagent grade.  
C.1.0.2 Barium chloride solution, approximately 10 % (m/v).  
C.1.0.3 Filter paper  
C.1.2. Procedure  
Weigh to the nearest 0.01 g about 1 0 g of the material (m1) in a porcelain dish, add 0.5 g of sodium bicarbonate 
and evaporate to dryness.  Moisten the residue with about 1000 g of the material accurately weighed (m2), add 
200 mL of boiling water and filter if necessary.  Bring the contents  to boil over a low flame and add slowly, with 
stirring, 5 mL of hot barium chlori de solution.  Boil the contents for 2 min and allow the precipitate to settle for 4 
h.  Filter the supernatant liquid through a tared sintered glass crucible (G No. 4) or a t ared Gooch crucible and 
transfer the precipitate carefully into the crucible.  Was h thoroughly with hot water till the washings are free from 
chlorides.  Heat the crucible at 1100 C to constant mass.  
 C.1.3. Calculation  
Sulphates (as H2SO4), % by mass  =    
42.02
𝑚1+𝑚2 
Where; 
m = mass in g of the precipitate.  
m1 = mass in g of the sampl e taken initially; and  
m2 = mass in g of the sample added subsequently   
x © KEBS 2020  – All rights reserved  
 C.2 For analytical reagent grade  
C.2.1 Reagents  
C.2.1.1 Sodium carbonate, analytical reagent grade.  
C 2.1.2 Hydrochloric acid, approximately 1N, sulphate -free.  
 
C 2.1.3 Barium chloride  solution, approximately 10 % (m/v)  
C.2.1.4 Standard sulphate solution, dissolve 0.178 g of potassium sulphate in water and make up the 
volume to 1000 ml.  Dilute 100 mL o f the solution in a graduated flask to 1000 ml.  One milliliter of the 
diluted soluti on contains 0.01 mg of sulphate (as H2SO4).  
C.3 Procedure  
To 20.00 g of the material add 20 mg of sodium carbonate and evaporate to dryness.  Take up the residue with 
5 ml of water and 0.5 mL of hydrochloric acid. Filter, wash with water to make up to 10 ml and add 1 ml of 
barium chloride solution.  Carry out a control test in the same manner using 4 mL of standard sulphate solution 
in place of the material.  Stir the two solutions and compare the turbidity produced.  
The limit prescribed in Table 1 shall b e taken as not having been exceeded if the turbidity produced with the 
material is not greater than that produced in the control test.  KENYA STANDARD  DKS 2927 :2020  
  ICS ##.###  
First  Edition  
 
  Annex  D 
(normative)  
Determination of  Iron Content  
D.1 Principle  
The iron present in the sample is reduced to the ferrous state and determined using 1,10 -phenanthroline 
spectrophotometrically; or by Atomic Absorption  Spectroscopy (AAS) method.  
D.2 Spectrophotometric method  
D.2.1  Apparatus  
D.2.1.1  Spectrophotometer with  1 cm cells, or alternatively Nessler cylinders.  
D.2.2.2  Twelve 100 ml volumetric flasks.  
D.2.2.3  250 ml volumetric flask.  
D.2.2  Reagents  
D.2.2.1  Hydrochloric acid, concentrated, d=1.18. free from iron.  
D.2.2.2  Hydrochloric aci d, approximately, N solution  free from iron.  
D.2.2.3  Hydroxyl ammonium chloride, 10 % (w/v) solution.  
D.2.2.4  Ammonium acetate, 20 % (w/v) solution.  
D.2.2.5  Bromine water, saturated.  
D.2.2.6  1,10-phenanthroline, 0.1 per cent (w/v) solution, dissolve 0.1 g of the reagent in 50 mL of w ater 
containing 2 ml of N hydrochloric acid and dilute to 100 ml.  
D.2.2.7  Standard iron solution, dissolve 7.022 g of ammonium ferrous sulphate in a mixture of 600 m l of water 
and 350 ml of concentrated sulphuric acid, d = 1.84.  Dilute to 1000 m l with deio nized water and further dilute 
10 m l of the solution so obtained to 1 000 m l with water. 1 m l of the solution contains 10 micrograms of iron (10 
µg of iron).  
D.2.2.8  Methyl orange indicator, 0.05 % (w/v) solution.  
 
D.2.3  Procedu re  
Preparation of standard iron solutions (color standards)  Into eleven of the 100 -mL volumetric flasks, each 
containing 50 ml of water, and 2 ml of N hydrochloric acid, transfer amounts of the standard iron solution, 
containing from 0 to 100 micrograms o f iron (0 g to 100 g of iron ) increasing by stages 10 micrograms (10 µg) 
and treat each solution as follows:   
xii © KEBS 2020  – All rights reserved  
 Add 2 ml of the hydroxyl ammonium chloride solution and allow to stand for one minute, add 10 ml of the 
ammonium acetate solution and 3 mL of the 1 ,10-phenanthroline solution.   Dilute the contents of the flask to 
100 mL and mix thoroughly.  These standard solutions are used directly for visual comparison of the colour with 
that of the sample.  
If an instrument is to be used, measure the optical densit y of each solution at a wave length of 515 nm and 
prepare a calibration chart.  
D.2.3.2  Determination  
Weigh accurately to the nearest 0.01 g, about 25 g of the sample and transfer to a 400 -ml beaker.  Add 100 ml 
of water one drop of methyl orange indicator a nd acidify with concentrated  hydrochloric acid adding 2 ml in 
excess.  Boil the solution for a few minutes.  Add a few drops of bromine water to destroy the colour of the 
indicator and boil the solution to expel excess bromine.  Cool the solution transfer to the 250 -ml one -mark 
volum etric flask, add 2 ml of the hydroxyl -ammonium chloride solution and allow to stand for 1 min.  Add 10 ml 
of the ammonium acetate solution mix and add 3 ml of the 1,10 -phenanthroline solution, dilute  to 100 ml with 
water and tho roughly mix.  At the same tim e carry out a blank test on the reagents alone.  Measure the optical 
density of the solution at wavelength of 515 nm and read the amount of iron present from the calibration chart 
prepared in F.2.3.1. Alternatively compare the co lour of the sample solution in matched Nessler cylinders with 
the series of the prepared standard iron solutions  
D.2.4  Calculation  
Iron content, as Fe parts per million by mass =  
12 25
mm  
where,  
m2 =   mass in micrograms, of iron found; and  
m1 = mass in grams of sample taken.  
D.3 Atomic absorption spectroscopy method  
 
D.3.1  Apparatus  
D.3.1.1  Atomic Absorption Spectrometer  
D.3.1.2  100 ml beaker  
D.3.1.3  Filter paper No. 1  
D.3.1.4 Analytical balance  
D.3.1.5 100 ml volumetric flask  
D.3.2  Reagent s KENYA STANDARD  DKS 2927 :2020  
  ICS ##.###  
First  Edition  
 
  D.3.2.1  Conc. Nitric acid d= 1.42.  
D.3.3  Procedure  
D.3.3.1  Take 2 g of the sample and add 6 ml of conc. Nitric acid and dissolve.  Filter the solution through filter 
paper No 1, into 100 ml beaker.  Wash the fi lter paper using distilled water.  Transfer the  filtrate to the 100 -ml 
volumetric flask.  Top up to the mark with distilled water.  Use this solution to determine the iron content in sodium 
bicarbonate using AAS.  
 
D.3.4. Calculations  
Fe content, mg/L =      
()
taken sample of Weight any if factor dilution volume  Reading      
  
xiv © KEBS 2020  – All rights reserved  
 Annex  E 
(normative)  
Test for Heavy Metal  (Lead)  
E.1 Outline of the Method (spectrophotometric method ) 
Lead reacts with dithizone (diphenylthio  Carbazone) to form a pink coloured complex in chloroform solution. 
The complex is separated by extraction with chloroform from an aque ous Ammonia -Cyanide Sulphite solution. 
The absorbance of the extracted complex is measured using a spectrophotometer at 5 10 nm wavelength.  
E.2 Apparatus  
 E.3.2.1 Standard Laboratory Apparatus  
E.3.2.2 Separating Funnels 250 ml capacity.  
E.3.2.3 Spectroph otometer or Photocolorimeter  
E.2.1  Reagents  
E.2.1 .1 Standard Lead Solution  
Dissolve 0.799 2 g of Analytical Reagent lead nitrate [Pb(NO3)2] in distilled water in a beaker, transfer 
quantitatively into a 500 -ml  volumetric flask, dilute to the mark and m ix well. One ml of this solution contains 1 
mg lead.  
E.2.1.2  Dilute Standard Lead Solution Transfer 10 ml of t he above solution (G.3.3.1) into a 1000ml volumetric 
flask, dilute to mark and mix well. 1 ml of this solution contains 10 µg of lead.  
E.2.1.3  Chloroform Reagent grade chloroform.  
E.2.1.4  Dithizone Reagent 50 mg/l solution in chloroform. Dissolve 5 mg of  the reagent in 100 ml of chloroform.  
E.2.1.5  Ammonia -Cyanide -Sulphite Reagent  
To 3 ml of 10 percent potassium cyanide solution (CAUTION - Potas sium cyanide is highly poisonous) add 35 
ml of concentrated ammonia and dilute to 100 ml. Add 0.15 g of sodium sulphite and mix well.  
E.2.1.6  Dilute Hydrochloric Acid Solution Approximately 1 mol/l.  
E.2.1.7  Hydrochloric Acid Solution Approximately 6 mol/ l.  
E.3 Procedure  
E.3.1 Calibration Transfer dilute standard lead solution to a series of six 250 -ml separatin g funnels as given 
below:  KENYA STANDARD  DKS 2927 :2020  
  ICS ##.###  
First  Edition  
 
  Standard Lead solution, ml                           Corresponding lead content µg,  
0 (Compensation)                                            0  
 2.0                                                                     20  
4.0                                                                       40  
6.0                                                                       60 
8.0                                                                          80 
10.0                                                                        100  
Add to each funnel 75 ml of ammonia -cyanide -sulphite reagent solution and cautiously adjust pH to 9.5 using a 
pH meter (eq uipped with a combined electrode). This operation must be carried out slowly because, if the pH 
of the solution falls below 9.5 even temporarily, HCN gas may be liberated. Use of fume cupboard during this 
operation is necessar y. Then add 7.5 ml of dithizon e reagent to each separating funnel. Maintain time difference 
among each such that the time after addition of dithizone reagent and final absorbance measurement is same 
for all. Then add 17.5 ml of chloroform and shake for one  minute to extract the lead co mplex into the chloroform 
layer, allow the phases to separate. Transfer the chloroform layer (lower one) through a cotton plug (placed in 
the stem of the separating funnel) into a 1 cm cell of the spectrophotometer. Immediatel y replace the lid of the 
cell. Measure absorbance (using chloroform extract of compensation solution, in reference cell) at 510 nm 
wavelength.  Plot a graph using 20 -25 ml of lead (in 25 ml of chloroform) as abscissae and corresponding 
absorbance values as ordinates.  
E.3.2 Determinatio n Weigh accurately correct to 1 mg about 10 g of Sodium bicarbonate sample (the quantity 
to be weighed, should be such that it contains 20 to 100 µg of lead) and transfer to 50 ml beaker dissolve in 
about 20 -25 ml distilled wa ter and transfer quantitativel y into a 250 ml separating funnel and rinse the beaker 
twice with 5 ml portions of distilled water. 75 ml of Ammonia -Cyanide -Sulphite reagent and then by the 
corresponding lead content in micrograms from the cautious addition of dilute hydrochloric acid so lution 
calibration graph. Adjust pH to 9.5. Use a pH meter with combined electrode to adjust pH. This operation must 
be carried out slowly because if the pH of the solution falls below 9.5 even temporarily, HCN gas may be 
liberated. Use of fume cupboard du ring this operation is necessary. Now add 7.5 ml of dithizone reagent to the 
separating funnel followed by 17.5 ml of chloroform. Shake for one minute to extract the lead into the chloroform 
layer. Allow the phase separate. Tr ansfer the chloroform layer th rough a cotton plug (placed in the separating 
funnel stem) into a 1 cm cell of the spectrophotometer and measure the absorbance at 510 nm with chloroform 
in the reference cell. Read the corresponding lead content in micrograms  from the calibration graph.  
E.3.3 Blank Test  
Carry out a blank test exactly as described in G -3.4.2 but excluding the test solution, use distilled water instead. 
Read the corresponding lead content in the blank from the calibration graph.   
xvi © KEBS 2020  – All rights reserved  
 E.4 Calculatio ns  
Calculate the lead content  in the material from the relation given below:  
Heavy metals (as Pb), ppm =    
𝑀1−𝑀2
𝑀0 
Where;  
 M1 = mass of lead in the test solution as obtained from graph in µg,  
M2= mass of lead blank as obtained from graph in µg, and  
M0 = mass of sample taken for analysis in grams  
 KENYA STANDARD  DKS 2927 :2020  
  ICS ##.###  
First  Edition  
 
  Annex  F 
(normative)  
Determination of Ammonium Compounds  
F.1 Reagents   
F.1.1 Sodium hydroxide solution, 5N, ammonia -free. 
 
F.1.2 Standard ammonium solution, dissolve 2.97 g of ammonium chloride in water and dilute to 1000 ml. 1 
ml of this solution contai ns 1 mg of ammonia.  Dilute 1 ml of this solution to 100 ml  with water immediately 
before use to get 0.01 mg of ammonia per ml.  
 
F.1.3 Nessl er’s reagent, dissolve 35 g of potassium iodide and 12.5 g of mercuric chloride in 800 ml of water 
and add a saturated solution of mercuric chloride until a slight permanent pre cipitate is produced.  Then add 
120 g of sodium hydroxide solution and enough w ater up to 1000 ml.  Shake the solution occasionally for 4 
days.  Allow to settle and decant the clear liquid.  
F.2 Procedure  
Dilute 2.8 mL (3.3 g) of the material with water to about 20 mL and add sodium hydroxide solution, until alkaline 
to litmus paper ( about 7 mL is required).  Dilute to 50 mL with water.  Prepare standard by diluting 1 m l of 
standard ammonium solution to 50 mL with water. To both solutions add 2 m l of Nessler ’s reagent and compare 
after 1 min.  
 
F.3 The limit prescribed in Table 1 shall  be taken as not having been exceeded if the yellow colour produced, if 
any, in the test with the material is not deeper than that of the standard.  
 
 
Alternatively, use High Per formance Liquid Chromatography (HPLC) method.  
  
xviii © KEBS 2020  – All rights reserved  
 Annex  G 
(normative)  
Determinatio n of Chlorides ( method A - volumetric method)  
G.1 Principle  
Chlorides are determined by neutralizing the sample with excess silver nitrate with ferric ammonium sulphate.  
G.1.1 F or Pure and Technical Grades  
G.1.1.1  Reagents  
G.1.1.1.1  Concentrated nitric acid  
G.1.1.1.2  Standard silver nitrate solution, 0.1 N.  
G.1.1.1.3  Nitrobenzene, analytical reagent.  
G.1.1.1.4  Standard ammonium thiocyanate solution, 0.1 N.  
G.1.1.1.5  Ferric ammoni um sulphate indicator, 25 % m/v.  
 
G.1.1.2 Procedure  
Weig h accurately about 20g of the material, dissolve in water and neutralize with concentrated nitric acid and 
then add about 5 ml in excess. Boil the solution to expel any dissolved carbon dioxide gas, c ool and add 10 ml 
of standard silver nitrate solution. A dd 3 ml of nitrobenzene, shake vigorously and titrate  
with standard ammonium thiocyanate solution using ferric ammonium sulphate indicator. At the end point a 
permanent faint reddish -brown colouration  appears.  
 G.1.1.3 Calculation  
Chloride (as Cl) % by mas s =    3.547(10N1−VN2)
M 
Where;  
N1 = normality of standard silver nitrate solution  
v = volume in ml of standard ammonium thiocyanate solution consumed in the titration,  
N2 = normality of standard ammonium thiocyanate solution, and  
M= mass in g of the materi al taken for the test.  
 
G.1.2 For Analytical Reagent Grade  
G.1.2.1 Apparatus and reagents  
G.1.2.1.1 Nessler cylinders 100 ml capacity.  
G.1.2.1.2 Concentrated nitric acid  
G.1.2.1.3 Silver nitrate solution Approximately 4 percent.  KENYA STANDARD  DKS 2927 :2020  
  ICS ##.###  
First  Edition  
 
  G.1.2.1.4 Standard chloride solu tion; Dry sodium chloride at 250°C before making the solution. Dissolve 1.649 
g of sodium chloride in water and make up the volume to 1 000 ml. Pipette out 10 ml from this solution and 
dilute with water to 1 000 ml. One millilitre of the dilut ed solution i s equivalent to 0.01 mg of chloride (as Cl).  
 
G.1.2.2 Procedure  
Dissolve 1.000)g  of the material in 30 ml of water and add slight excess of concentrated nitric acid. Boil the 
solution, cool and add 1 ml of silver nitrate solution. Transfer into a Nessler c ylinder and make up the volume to 
100 ml mark with water. Carry out a control te st using 1 ml of standard chloride solution and the same quantities 
of other reagent in the same total volume of the reaction mixture. Compare the turbidity in both the cylinde rs 
after 5 minutes. The limit prescribed in Table 1 shall be taken as not having  been exceeded if the turbidity 
produced in the test with the material is not greater than that produced in the control test.  
 
G.2 METHOD B (SPECTROPHOTOMETRIC (METHOD)  
G.2.1 O utline of the Method  
To a neutralized solution of sodium bicarbonate, addition o f mercuric thiocyanate and ferric ammonium  sulphate 
produces a highly coloured ferric thiocyanate complex, the intensity of which is proportional to the chloride 
content. The a bsorbance of this colour is measured at 450 nm wavelength.  
G.2.2 Apparatus  
G.2.2 .1 Standard Laboratory Apparatus 4  
G.2.2.2 Spectrophotometer or Photocolorimeter  
G.2.2.3 Platinum Evaporating Dish 60 ml capacity.  
G.2.3 Reagents  
G.2.3.1 Ferric Ammonium Sulpha te Solution (0.25mol/l). Dissolve 49.02 g of Ferric Ammonium Sulphate  
Dodecahydr ate [FeNH4(SO4)2. 12H2O] in 203 ml of dilute nitric acid (about 1.5 mol/l) and dilute to 500 ml  
with distilled water.  
G.2.3.2 Mercury (II) Thiocyanate Solution Saturated soluti on in absolute alcohol.  
G.2.3.3 Standard Sodium Chloride Solution Weigh accurate ly 0.165 0 g of previously dried (at 500°C) and 
cooled A.R. sodium chloride, dissolve in a beaker in distilled water and quantitatively transfer into a one litre 
volumetric fla sk, dilute to mark and mix well 1 ml of this solution = 100 µg of Cl.  
G.2.3.3.1  Dilute Standard Sodium Chloride Solution Transfer 50 ml of standard sodium chloride solution  
into a 500 ml volumetric flask, dilute with distilled water to the mark and mix we ll. 1 ml of this solution = 10 /Lg 
of Cl.  
G.2.3.4 Sulphuric Acid Solution Approx imately 1 mol/l - Pour 56 ml of concentrated sulphuric acid (AR quality) 
into 944 ml of distilled water slowly, mix and cool.  
  
xx © KEBS 2020  – All rights reserved  
 G.2.4 Procedure  
G.2.4.1 Calibration  
Into a series  of six 50 -ml volumetric flasks, transfer standard sodium standard sodium chloride solution as given 
below:  
 
Standard Sodium Chloride Solution ml                Corresponding Mass of Chloride (as Cl) µg  
2               20 
4               40 
6               60 
8               80 
10               100 
Add to each, 2 ml of ferric ammonium sulphate solution and 2 ml of mercury thiocyanate solution in that order. 
Dilute to mark and mix well. Allow to stand for 15 minutes, transfer to the cell of spe ctrophotomete r and measure 
absorbance of 450 nm wavelength with compensation solution in reference cell. Plot chloride content in 
micrograms as abscissa vs. corresponding absorbance values as ordinates.  
G.2.4.2 Determination  
Weigh suitable mass of sodium b icarbonate sa mple containing 50 to 150 µg of chloride (as Cl) correct to 1 mg 
and transfer into the platinum evaporating dish, wet this with 15 to 20 ml of distilled water and slowly  neutralize 
with sulphuric acid solution add a few drops in excess. Evapor ate to nearly  dryness on hot water bath. Add 20 
to 30 ml of distilled water and quantitatively transfer into a 100 ml volumetric flask, cool and make up to the 
mark with distilled water and mix well. Filter through Whatman No. 41 filter paper and discard a  small volume  of 
initial filtrate. Transfer suitable volume (25 to 40 ml) into 50 ml volumetric flask add 2 ml of ferric ammonium 
sulphate solution and 2 ml of mercury thiocyanate solution in that order, dilute to mark with distilled water and 
mix well. Al low to stand for 15 minutes, transfer to the cell of spectrophotometer and measure absorbance at 
450 nm wavelength with distilled water in the reference cell.  
G.2.4.3 Blank Test  
Carry out a blank test using the same procedure as used for determination usin g same quanti ties of all reagents 
but emitting the test solution. Instead of test solution use distilled water.  
G.2.4.4 Calculations  
The chloride content is calculated from the formula:  
Chloride (as Cl) % by mass = 𝑀1−𝑀2
𝑀0×10,000 
Where;  
M1 = mass in mic rograms of  chloride corresponding to absorbance of test solution,  KENYA STANDARD  DKS 2927 :2020  
  ICS ##.###  
First  Edition  
 
  M2, = mass in micrograms of chloride corresponding to absorbance of blank solution,  
M0, = mass in grams of sodium bicarbonate in the test portion of the aliquot used for color development.   
xxii © KEBS 2020  – All rights reserved  
 Annex  H 
(normative)  
Test for substance reducing Iodine  
H.1 REAGENTS  
H.1.1 Starch Solution  
Titrate 5 g of starch and 0.01 g of mercuric iodide with  30 ml of water in a mortar. Pour the resulting paste  
into one litre of boiling water and boil for 3 minutes.  Allow the s olution to cool and decant off the clear liquid.  
H.1.2 Standard Iodine Solution  0.01 N.  
H.2 PROCEDURE  
Dissolve 10 g of the material in 200 ml of freshly boiled  and cooled water. Add 2 ml of starch solution and  
titrate with standard iodi ne solution.  The mat erial shall be taken to have passed the test if  not more than 0.5 ml 
of iodine solution is required to  produce a permanent blue colour.  KENYA STANDARD  DKS 2927 :2020  
  ICS ##.###  
First  Edition  
 
  Annex  J 
(normative)  
Test for Phosphates  
  (SPECTROPHOTOMETRIC METHOD)  
J.1 Outline of the Method  
Silica is eliminated by precipitation and filtration. Formation of phosphomolybdic acid complex in acidic solution 
and reduction of yellow complex to molybdenum blue complex. Measurement of the intensity of the blue colour 
(which is proportional to phosphate c oncentration) using a spectrophotometer or photocolorimeter at 580 nm 
wavelength.  
J.2 Apparatus and reagents  
J.2.1Apparatus  
J.2.1.1 Standard Laboratory Apparatus  
J.2.1.2 Spectrophotometer or Photoelectric Colorimeter  
J.2.1.3 Platinum Evaporating Dish Appro ximately 60 ml capac ity. 
J.2.2 Reagents  
J.2.2.1 Perchloric Acid  
60 to 70% solution (m/m).  
J.2.2.2 Ammonium Molybdate Solution  
Dissolve 10 g of ammonium molybdate tetra hydrate (NH4)6Mo7O24.4H2O in 100 ml of water. Add slowly 220 
ml of sulphuric acid (1:1 s olution) and 70 ml d istilled water. Mix and allow to cool.  
J.2.2.3 Reducing Solution  
Dissolve 0.25 g of 1 -amino 2 -naphthol 4 -sulphonic acid and 0.5 g of anhydrous, sodium sulphite (Na2SO4) in 
about 70 ml distilled water. Dissolve separately 24 g of anhydro us sodium bisulphite  (Na2S2O5) in about 100 
ml distilled water. Mix both solutions and dilute to 200 ml with distilled water, filter, if necessary and store in a 
cool dark place.  
J.2.2.4 Standard Phosphate Solution   
xxiv © KEBS 2020  – All rights reserved  
 Weigh accurately 1.433 g of finely powder ed and dried A.R. po tassium dihydrogen phosphate (KH2PO4)  
dissolve in 100 to 150 ml distilled water in a 250 ml beaker, transfer quantitatively to 1 000 ml volumetric  
flask,  dilute to mark and mix well. Transfer 50 ml of this solution to a 500 ml volumetric flask, dilute to  
mark and mix well. 1ml of this solution contains 100 µg of phosphate (as PO4).  
J.2.2.4.1 Dilute Standard Phosphate Solution  
10 µg PO4 per litre - Transfer  50 ml of standard phosphate solution into a 500 ml volumetric flask,  
dilute to mark and mix well.  
J.2.2.5 Hydrochloric Acid Solution  
Approximately 6 mol/l - Add slowly 535 ml of concentrated hydrochloric acid (specific gravity 1.18) into  
465 ml of distill ed water and mix.  
J.3 Procedure  
J.3.1 Calibration  
Into a series of six 100ml volumetric flasks, transfe r dilute standard phosphate solution as given below:  
Standard Phosphate Solution, ml                 Corresponding Mass of  Phosphate as PO 4, µg 
0 (Compensation)          0 
2            20 
4             40 
6             60 
8            80 
10            100 
Add to each flask 2 ml of perchloric acid, 20 ml of  distilled water, 10 ml of ammonium molybdate  solution and 
finally 5 ml of reducing solution. Ma ke upto the mark and mix well. Place flasks in boiling  water -bath for 15 
minutes,  cool in running water  and me asure absorbance using 2 cm cell in a  spectrophotometer (or 
photocolorimeter) at 620 nm  wavelength using compensation solution in the  reference cell.  Plot a graph with µg 
of PO 4 as abscissae and  corresponding absorbance values as ordinates.  
J.3.2 Determina tion 
Weigh about 1 g of sodium bicarbonate accurately to 1mg (the quantity to be weighed should be such that it 
contains 20 to 100 µg of phosphate) and transfer into a 60 ml platinum evaporating dish, wet it with some distilled KENYA STANDARD  DKS 2927 :2020  
  ICS ##.###  
First  Edition  
 
  water and neutralize with hy drochloric acid solution and add a few drops in excess. Evaporate to nearly dryness 
and add 2 ml of perchloric acid and again evaporat e to nearly dryness. Add a few drops of hydrochloric acid 
solution and about 20 ml of distilled water and transfer quantit atively into a 100 ml volumetric flask. Cool and  
dilute to mark and mix well.  Filter through a Whatman No. 4 1 filter paper, discard  a small volume of initial filtrate 
and then transfer  50 ml of filtrate into 100 ml volumetric flask and  develop colour as d escribed under calibration  
(J.3.1). 
Measure absorbance at 620 nm wavelength using same size cell as used for calibration, with distill ed water in 
the reference cell . 
J.3.3 Bl ank Test  
Carry out a blank test using the same procedure and  same quantities of al l reagents as in the case of  
determination (K -3.4.2) except omitting the sample  solution. Use distilled water instead of sample solution.  
J.4 Calculations  
Phosp hate (as PO 4), percent by mass =𝑀1−𝑀2
𝑀𝑜×10,000 
Where ; 
M1= mass in micrograms of phosphate  corresponding to the absorbance of the test  portion,  
M2, = mass in micrograms of phosphate  corresponding to the absorbance of the  blank, and  
Mo = mass in grams of the sodium bicarbonate  conten t corresponding to &e test portion  of the aliquot solution 
used for colour  development.   
xxvi © KEBS 2020  – All rights reserved  
 Annex  K 
(normative)  
Determination of Calcium and Magnesium  
K.1 REAGENTS  
K.1.1 Standard C alcium Solution  
Weigh 1.000 g of calcium carbonate dried at 120°C and dissolve it in the minimum quantity of dilute hydrochloric 
acid. Dilute the solution to one litre in a graduated flask. One ml of this solution is equivalent to 0.400 08 mg of 
calcium ( as Ca).  
K.1.2 Standard EDTA Solution  
Dissolve 3.72 g of disodium ethylene diamin e tetra -acetate dihydrate in water and dilute in a graduated flask to 
one litre. The solution shall be standardized frequently against the standard calcium solution, following the 
procedure given in K.2.1. 
K.1.3 Eriochrome Black -T Indicator Solution  
Dissol ve 0.1 g of the dye in 20 ml of rectified spirit. This solution shall be prepared fresh every week.  
K.1.4 Ammonium Chloride -Ammonium Hydroxide Buffer Solution  
Dissolve 67.5 g o f ammonium chloride in a mixture of 570 ml of ammonium hydroxide (sp gr 0.90) an d 
2.50 ml of water. Also dissolve separately a mixture of 0.931 g of disodium ethylene diamine tetra -acetate  
dihydrate and 0.616 g of magnesium sulphate (MgS04.7H2O) in about 5 0 ml of water. Mix the two  
solutions and dilute to one litre.  
NOTE -Five millilit res of the 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.  
K.2 PROCEDURE  
K.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 EDTA solution to a pure blue end point.  
K.2.2 Titrate 25  ml of the buffer solution with EDTA solution using Eriochrome black -T indicator. Subtract  
the buffer correction for 10 ml (usually, it will be 0.1 ml) from the reading obtained in K.2.1 and note  the final 
titre value. Calculate the calcium equivalent of 1  ml of EDTA solution (say A).  
K.2.3 Transfer exactly 100 ml of solution preserved in B .2 into a 250 ml conical flask. Add 20 ml of ammonium 
chloride -ammonium hydroxide buffer solution, 5 drops of Eriochrome black -T indicator solution and titrate 
against st andard EDTA solution till wine red colour of the solution changes to pure blue endpoint . Note the 
volume of EDTA solution used in the titration.  
K.3 CALCULATION  KENYA STANDARD  DKS 2927 :2020  
  ICS ##.###  
First  Edition  
 
  Calcium and magnesium (as Ca), percent by mass          =𝐴𝑉1
𝑀×100 
where A = calcium equivalent calculated in g of 1 ml of EDTA solution determined in K.2.2,  
V1 = volume in ml of sta ndard EDTA solution used in K.2.3, and  
M = mass in g of the material taken for the test in B.2.  
xxviii  © KEBS 2020  – All rights reserved  
 Annex  L 
(normative)  
Test for Nitrates  
L.1 REAGENTS  
L.1.1 Dilute Sulphuric Acid  
Approximately 5 N.  
L.1.2 Concentrated Hydrochloric Acid  
L.1.3 Potassium Nitrate Solution 0.001 N.  
L.1.4 Concentrated Sulphuric Acid  
L.1.5 Standard Indigo Carmine Solution  
Dissolve 0.20 g of indigo carmine i n 400 ml of dilute sulphuric acid and add 20 ml of concentrated hydrochloric 
acid and sufficiently dilute sulphuric 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 addin g 13 ml of concentrated  sulphuric acid and 
heating to boiling. One millilitre of this solution is equivalent to 0.02 mg of n itrate  (as NO3).  
L.2 PROCEDURE  
Dissolve 2.000 g of the material in 10 ml of dilute sulphuric acid, and 10 ml of standard indigo carm ine solution 
followed by 10 ml of concentrated sulphuric acid and heat to boiling. The limit prescribed in Table 1 shall be 
taken as not having been exceeded if the blue colour produced in the test with the material does not entirely 
disappear.  
  KENYA STANDARD  DKS 2927 :2020  
  ICS ##.###  
First  Edition  
 
  Annex  M 
(normative)  
Determination of Potassium  
M.1 APPARATUS  
 M.1.1 Flame Photometer Equipped with interference filter.  
M.2 REAGENTS   
M.2.1 Standard Potassium Solution  
Weigh exactly 1 g of potassium chloride, dissolve in distilled water and dilute to one liter wi th distilled water in a 
measuring flask. This solution contains 0.1 g KCl per 100 ml.  
M.3 PROCEDURE  
M.3.1 Calibration Graph  
Take 10, 20,40, 60 and 80 ml of standard potassium solution and dilute to 100 ml with distilled water in different 
measuring flas ks Each flask now contains 0.01, 0.02, 0.04, 0.06 and 0.08 g KCl per 100 ml. Use these dilute 
solutions  to obtain a corresponding galvanometer reading as given in M.3.2.1 and plot the concentration against 
galvanometer reading in a rectangular co -ordinatio n graph. Draw a smooth curve over the points which gives a 
calibration graph in the range 0.01 to 0.1 p ercent KCl. M.3.2 Sample Solution Dissolve approximately 10 g of 
the sample in minimum quantity of distilled water and dilute to 100 ml in measuring flas k with distilled water.  
M.3.2.1 Determination  
Use a flame photometer equipped with atomizer, burner, optical selective device consisting of the reflectors, 
lenses  and diaphragms; and measuring instrument consisting of photocell, amplifier and sensitive 
galvanometer. The galvanometer scale ranges from 0 to 100 divisions which measures the intensity of the 
radiation transmitted by the element. Insert the potassium filter corresponding to wavelength 767 nm, light the 
Burner fed by illuminating gas (laborator y gas), adjust the specified air pressure between 0.5 to 0.6 kg/cm2 and 
maintain the above air pressure  constant, such that flame is non -luminous by turning the control knob. First 
spray distilled water and adjust the pointer to zero in galvanometer scale by zero adjustment knob. Then spray 
the KCl standard solution and adjust the deflection to maximum 100 by using sensitivity control knob. Again,  
spray water to see that the pointer comes to zero; then spray a standard solution reads 100 with same 
adjustmen t during both the operations. A reading zero by water and with the same adjustment 100 by standard 
solution indicate that the instrument has bee n made ready for measurement.   
xxx © KEBS 2020  – All rights reserved  
 Without altering the earlier adjustment of the instrument spray various diluted s olutions prepared in M.3.1 and 
obtain a calibration graph in the range 0.0 1 to 0.1 percent KCl. After washing with distilled water, spray the 
sample solution and obtain the galvanometer reading. From the graph, read out the corresponding concentration 
of KC1 in the solution (say A).  
 
 
 
 
M.4 CALCULATION  
Potassium (as K), percent by mass = 52.35𝐴
𝑀 
Where;  
 A = concentration of KCl in the sample s olution, And  
M=mass of dried sample taken for the test.  KENYA STANDARD  DKS 2927 :2020  
  ICS ##.###  
First  Edition  
 
  Annex  N 
(normative)  
Test for copper  
N.1 Outline of th e Test Method  
The material is neutralized with hydrochloric acid. The copper in the soluble form is treated with 
diethyldithiocarbamate solution t o produce a colored copper complex. This is extracted with carbon 
tetrachloride. The absorbance of the C Cl4 extracts measured at 440 n m using a spectrophotometer or a 
photocolorimeter.  
N.2.0 Apparatus  
N.2.0.1 Spectrophotometer or a Photocolorimeter Suita ble for measuring absorbance at 440 nm.  
N.2.0.2 Standard Laboratory Glass Apparatus  
N.2.0.3 Platinum Dish, o f about 60 ml capacity.  
N.2.1 Reagents  
N.2.1 .1 Distilled Water  
N.2.2.2 Hydrochloric Acid Approximately 6 mol/l -Dilute 500 ml con c HCl (sp gr 1.19) with 500 ml distilled water.  
N.2.2.3 EDTA Solution 5 percent solution - Dissolve 50 g Ethylene diamine t etra-acetic acid, disodium salt 
(C10H14 O8Na2. 2H 2O) in distilled water, dilute to 1 000 ml and keep the solution in a polyethylene bottle.  
N.2.2.4 Sodium Diethyldithiocarbamate Solution (DEDTC) Dissolve 0.1 g of DEDTC  
[(C2H5 )2N.CS 2Na.3H 2O] in 100 ml of  distilled water and keep the solution in a dark b ottle.  
N.2.2.5 Standard Copper Solution Dissolve 0.100 g pure copper metal in the smallest possible quantity nitric 
acid in a 1 000 ml volumetric flask, cool and dilute to mark. One millilitre of this solu tion contains 100 µg copper. 
Transfer 10 ml aliquo t of this solution (M -3.3.5) in to 100 ml volumetric flask, dilute to mark and mix. One millilitre 
of this solution is equivalent to 10 µg of copper.  
N.2.2.6 Ammonium Hydroxide Solution Concentrated.  
N.2.2.7 Carbon Tetrachloride Reagent grade C Cl4.   
xxxii © KEBS 2020  – All rights reserved  
 N.2.2.8 Phenolphthalein Solution Dissolve 0.5 g phenolphthalein powder in 500 ml of 50 -70 percent ethanol or 
methanol. Neutralize the solution by adding 0.1 mol/l NaOH until a faint p ink color appears and then remove 
this color with a drop or two of 0.1 mol/l hydrochloric acid.  
N.2.2.9 Hydrochloric Acid So lution Approximately 1 mol/l.  
N.3 Procedure  
N.3.1 Calibration Into a series of six 250 -ml separatory funnels, transfer standard dilute copper solution as giv en 
below:  
Standard Copper Solution, ml                                          Corresponding Mass of Copper, µg 
0 (Compensation)                                                                0.0  
2.0                                                                                           20.0 
4.0                                                                                            40.0  
6.0                                                                                             60.0  
8.0                                                                                              80.0  
10.0                                                                                             100.0  
 
 
Add to  each 20 ml hydrochloric acid solution,10 ml EDTA sol ution and then 5 drops of phenolphthalein solution 
and mix well. Neutralize each with concentrated ammonium hydroxide solution to a faint pink color and cool to 
room temperature. Add distilled water to e ach to a final volume of 45 ml. Then add to each 5 ml DEDTC solution 
mix well and add 20 ml carbon tetrachloride.  Shake the funnel vigorously for at least 3 minutes and allow the 
phases to separate. Filter C Cl4 phase (the lower phase) through a cotton plug  inserted in the outlet stem of the 
separatory funnel into photometer cells. Apply the lid of the cell and measure absorbance at 440 nm with extract 
of copper free solution (compensation solution) as reference. Plot copper content ( µg/20 ml) as abscissae ‘ vs 
corresponding absorbance values as ordinates.  
N.3.2 Determination Weigh accurately correct to 1 mg an amount of sodium bicarbonate sample containing 200 
to 1 000 µg of copper and transfer into a platinum dish.  Wet it with minimum amount of distilled wa ter and 
neutralize with 6 mol/l hydrochloric acid solution and add a few drops in excess. Evaporate to dryness on a 
water -bath. Wet it with a few drops of dilute hydrochloric acid solution and then dissolve in 20 to 30 ml of distilled 
water and quantitativ ely transfer into a 100 ml one mark volumetric flask, cool, make upto the mark and mix 
well. If the solution is turbid, filter through a Whatman No. 541 filter paper discarding 10 to 15 ml of initiate 
filtrate. Transfer 10.0 ml of the aliquot volume (or th e filtrate if filtered) into a 250 -ml separatory funnel and 
proceed further exactly as described under calibration.  
N.3.3 Blank Test  
Carry out a blank test exactly as described in M.3.4.2 but excluding the test solution, use distilled water instead. 
Read t he corresponding lead content in the blank from the calibration graph.  
N.4 Calculations  
By means of the calibration graph determine the mass of copper in micrograms corresponding to the absorbance 
value of the test solution.  KENYA STANDARD  DKS 2927 :2020  
  ICS ##.###  
First  Edition  
 
  Copper (as Cu), parts per mill ion = 𝑀1−𝑀2
𝑀0 
Where;  
M1 = mass of copper in micrograms in the test portion,  
M2=mass of copper in micrograms in the blank, and  
M0= mass of the sodium bicarbonate content in grams in the test portion used.  
  
xxxiv  © KEBS 2020  – All rights reserved  
 Annex  P 
(normative)  
Sampling  
 
Table E.1 — Number of  containers to be selected for sampling  
  
Sl No Lot size  No. of containers t o be 
Selected  
 N 11 
(1) (2) (3) 
i) Up to 15  2 
ii) 16 to 25  3 
iii) 26 to 50  4 
iv) 51 to 100  5 
v) 101 to 300  6 
vi) 301 to 500  7 
vii) 501 to 800  8 
viii) 801 to1 000 9 
ix) 1 001 and above  10 
 
The containers shall be selected at random from a lot . In order to ensure randomness o f selection random 
number tables shall be used .  
 
 KENYA STANDARD  DKS 2927 :2020  
  ICS ##.###  
First  Edition  
 
    
xxxvi  © KEBS 2020  – All rights reserved