DRAFT UGANDA STANDARD  
  DUS 1583-2  
First Edition  
2018-mm-dd  
 
 
 Reference number 
DUS 1583-2: 2018 
© UNBS 2018  
  
Sampling and test for sodium hydroxide for industri al use —
Part 2 — Determination of copper content 
 DUS 1583-2: 2018 
ii © UNBS 2018 – All rights reserved
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 Foreword 
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 DRAFT UGANDA STANDARD DUS 1583-2: 2018 
 
© UNBS 2018  – All rights reserved  1
 Sampling and test for sodium hydroxide for industri al use —
Part 2— Determination of copper content  
1 Scope  
This Part of the Draft Uganda Standard describes a method of test for the  determination of the copper content 
of sodium hydroxide  for industrial use.  
The method is applicable to products having copper  contents, expressed as Cu, in the ranges 0.5 mg/kg to  
10 mg/kg and 0.25 mg/kg to 5 mg/kg for the solid  and liquid products, respectively  
2 Normative references  
The following referenced documents are indispensabl e for the application of this document. For dated 
references, only the edition cited applies. For und ated references, the latest edition of the referenc ed 
document (including any amendments) applies. 
DUS ISO 3696:1987 Water for analytical laboratory u se— Specification and test methods 
3 Principle 
The copper present is reduced with ascorbic acid an d a  violet coloured complex is formed by addition of  2,2'-
biquinolyl. This complex is extracted with amyl  alcohol and its colour measured spectrophotometrica lly.  
4. Reagents 
The reagents used shall be of recognized analytical  quality.  Water complying with the requirements of FDUS 
ISO 3696 shall  be used throughout.  
4.1   Sodium hydroxide.  
4.2   Sodium sulphate, anhydrous. 
4.3  Hydrochloric acid solution  
ρ approximately 1.18g/ml,  approximately 36 % (m/m) solution or approximately 11N.  
4.4  Amyl alcohol. 
4.5  (+}- Tartaric acid 
500 g/l solution.  
4.6  Sodium hydroxide 
200 g/l solution.  DUS 1583-2: 2018 
2 © UNBS 2018 – All rights reserved
 4.7  L-Ascorbic acid 
100 g/l solution, freshly prepared.  
4.8  2, 2'-Biquinotyl, 0.5 g/l solution.  
Dissolve 0.25 g of  2,2'-biquinolyl in the amyl alcohol (4.4) and dilut e with  more of the amyl alcohol to 500 ml.  
4.9  Bromine water 
saturated solution.  
4.10   Copper 
standard solution corresponding to 0.1 g of  copper per litre. Dissolve 0.3928 g of copper (II) sulphate  
pentahydrate (CuSO 4.5H 2O) in water in a 1000 ml  one-mark volumetric flask, add 25 ml of approximate ly  6N 
sulphuric acid solution, dilute to the mark and mix .  
1 ml of this standard solution contains 0.100 mg of  Cu.  
4.11  Copper 
standard solution corresponding to  0.01 g of copper per litre. Dilute 10.0 ml of the s tandard  copper solution 
(4.10) to the mark in a 100 ml one-mark volumetric flask and mix.  1 ml of this standard solution contains 10 µg 
of Cu.  
4.12  Narrow range indicator papers 
covering the range  pH 5.5 to pH 7.0.  
4.13  Methyl orange indicator 
0.5 g/l aqueous solution.  
5.  Apparatus  
Ordinary laboratory apparatus and the following are  required.  
5.1   Spectrophotometer, or  
5.2  Photoelectric absorptiometer 
fitted with filters  providing maximum transmission at a wavelength of  about 545 nm.  
5.3  Optical cells 
4 cm optical path length. 
 DUS 1583-2: 2018 
© UNBS 2018 – All rights reserved  3
 6.  Procedure  
6.1  Test portion. 
Weigh, to the nearest 0.01 g in a plastics  weighing bottle fitted with a cover, an amount of t he  sample 
corresponding to about 10 g of sodium hydroxide.  
6.2  Blank test 
Carry out a blank test at the same time as  the determination, following the same procedure and  using the 
same quantities of reagents as specified in 6.4  but using 10 g of the sodium hydroxide (4.1).  
6.3   Preparation of the calibration graph  
6.3.1  Preparation of standard matching solutions.  
Into each of a series of six 500 ml stoppered separ ating  funnels, introduce the volumes of the standard copp er  
solution (4.11) shown in table 1.  
Table 1: Volumes of standard copper solution 
Standard copper 
solution (4.11), mL Corresponding mass  
of copper (Cu), µg 
0* 0 
2.0 20 
4.0 40 
6.0 60 
8.0 80 
10.0 100 
*Compensation solution 
 
6.3.2  Colour development.  
Treat the contents of each  funnel (6.3.1) as follows.  
Dilute with water to approximately 400 ml, then add  2 ml of the tartaric acid solution (4.5). Adjust th e pH  of the 
solution to about 6.by addition of the sodium  hydroxide solution (4.6) using the narrow range  indicator paper 
(4.12) externally. Add 2 ml of the  ascorbic acid solution (4.7), shake so as to mix  thoroughly and allow to 
stand for 5 min. Add 10 ml  of the 2,2'-biquinolyl solution (4.8) and shake wel l for  about 2 min. Extract the 
copper complex with two  20 ml portions of the amyl alcohol (4.4), and trans fer  the extracts to a 100 ml beaker. 
Add about 2 g of the  anhydrous sodium sulphate (4.2) to the combined  extracts and stir thoroughly to remove 
traces of water.  
Filter the dried extract into a 50 ml one-mark  volumetric flask, wash the residual sodium sulphate  twice with 2 
ml portions of the amyl alcohol (4.4).  Transfer the washings to the flask; dilute to the  mark with the amyl 
alcohol (4.4) and mix.  
6.3.3  Photometric measurements.  
Carry out the photo-metric measurements either with  the spectrophoto-  meter (5.1) at the wavelength of 
maximum absorption  (about 545 nm), or with the photoelectric absorptio -meter (5.2), fitted with suitable filters, 
after having  adjusted the instrument to zero absorbance against the  amyl alcohol (4.4).  DUS 1583-2: 2018 
4 © UNBS 2018 – All rights reserved
 6.3.4  Plotting the calibration graph.  
Deduct the  absorbance of the compensation solution (6.3.1) fro m  those of the standard matching solutions 
(6.3.1). Plot a  graph having, for example, the copper content expre ssed  in micrograms per 50 ml of standard 
matching solution,  as abscissae and the corresponding values of absorb ance  as ordinates.  
6.4  Determination  
6.4.1  Preparation of the test solution.  
Transfer the test  portion quantitatively to a 400 ml beaker. Add abou t  100 ml of water and 1 drop of the methyl 
orange  indicator solution (4.13). Neutralize the solution with  the hydrochloric acid solution (4.3), then add 5 ml  
in  excess and add 10 ml of the bromine water (4.9).  
Boil the solution until free from bromine and allow  to  cool. Transfer the contents of the beaker quantitat ively  to 
a 500 ml separating funnel fitted with a stopper.  
6.4.2  Colour development. 
Treat the test solution in the  separating funnel (6.4.1) as specified in 6.3.2.  
6.4.3  Photometric measurement. 
Carry out the photo-metric measurement on the test solution (6.4.2) and on  the blank test solution (6.2) 
following the procedure  described in 6.3.3, after having adjusted the instr ument  to zero absorbance against 
the amyl alcohol (4.4).  
NOTE. If the absorbance exceeds the maximum of the calibration  graph, repeat the determination using a smaller amo unt 
of the test  portion (6.1) and modifying the calculation accordi ngly.  
7.  Expression of results  
By means of the calibration graph (6.3.4), determin e the  quantity of copper (Cu) corresponding to the value of  
the photometric measurement.  The copper content, expressed as milligrams of copp er  (Cu) per kilogram, is 
given by the following formula:  
02 1
02 1 1000 
1000 mmm
mxm m−=− 
Where  
m0 is the mass of the test portion (in g) 
m1 is the mass of copper in the test solution (in µg)  
m2 is the mass of copper in the blank test solution  (in µg)  
 
 DUS 1583-2: 2018 
© UNBS 2018 – All rights reserved  5
 Bibliography 
[1] BS 6075: Part 12: 1981 Sampling and test for so dium hydroxide for industrial use Part 12: 
Determination of copper content 
 DUS 1583-2: 2018 
© UNBS 2018  – All rights reserved  7
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 DUS 1583-2: 2018 
 
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