INTERNATIONAL IS0

STANDARD 99632
First edition
1994-l I-1 5

Water quality - Determination of

alkalinity -
Part 2:
iTeh STANDARD
Determination PREVIEW
of carbonate alkalinity
(standards.iteh.ai)
Qua/it6 ISO I’eau - 06 termination
de 9963-2:1994 de I alcalinit6 -
Partie 2: D6 termha tion de I ‘alcalinit6 carbonate
https://standards.iteh.ai/catalog/standards/sist/e34092fb-d168-4c24-af32-
46234007c351/iso-9963-2-1994

Reference number
IS0 99632:1994(E)
IS0 9963-2: 1994(E)

Foreword

IS0 (the International Organization for Standardization) is a worldwide

federation of national standards bodies (IS0 member bodies). The work
of preparing International Standards is normally carried out through IS0
technical committees. Each member body interested in a subject for
which a technical committee has been established has the right to be
represented on that committee. International organizations, governmental
and non-governmental, in liaison with ISO, also take part in the work. IS0
collaborates closely with the International Electrotechnical Commission
(IEC) on all matters of electrotechnical standardization.

Draft International Standards adopted by the technical committees are

circulated to the member bodies for voting. Publication as an International
iTeh STANDARD PREVIEW
Standard requires approval by at least 75 % of the member bodies casting
a vote.

International Standard IS0

(standards.iteh.ai)
9963-2 was prepared by Technical Committee
lSO/TC 147, Water quality, Subcommittee SC 2, Physical, chemical,
biochemical methods. ISO 9963-2:1994
https://standards.iteh.ai/catalog/standards/sist/e34092fb-d168-4c24-af32-
IS0 9963 consists of the following parts, under 46234007c351/iso-9963-2-1994
the general title Water
quality - Determination of alkalinity:

- Part 1: Determination of total and composite alkalinity

- Part 2: Determination of carbonate alkalinity

Annexes A and B of this part of IS0 9963 are for information only.

0 IS0 1994
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronic or mechanical, including photocopying and
microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case Postale 56 l CH-1211 Geneve 20 l Switzerland
Printed in Switzerland

ii
INTERNATIONAL STANDARD 0 IS0 IS0 9963-2: 1994(E)

Water quality - Determination of alkalinity -

Part 2:
Determination of carbonate alkalinity

1 Scope IS0 385-l :1984, Laboratory glassware - Burettes -

Part 1: General requirements.
This part of IS0 9963 specifies a method for the
titrimetric determination of carbonate alkalinity in IS0 3696: 1987, Water for analytical laboratory use -
natural and drinking water. Using a higher pH value for Specification and test methods.
the endpoint than the iTeh STANDARD IS0
method PREVIEW
specified in
5667-2:1991, Water quality - Sampling -
IS0 9963-1, the influence of other hydrogen ac-
(standards.iteh.ai)
Part
ceptors, such as anions of humic acids, is reduced
2: Guidance
by
on sampling techniques.
the procedure.
IS0 6107-2:1989, Water quality - Vocabulary -
ISO 9963-2:1994Part 2.
The method is intended https://standards.iteh.ai/catalog/standards/sist/e34092fb-d168-4c24-af32-
for samples with a carbonate
alkalinity between 0,Ol mmol/l and 4 mmol/l (as H+
46234007c351/iso-9963-2-1994
IS0 9963-l :l994, Water quality - Determination of
equivalents). For samples containing higher concen-
alkalinity - Part 1: Determination of total and com-
trations of alkalinity, a smaller test portion can be used
posite alkalinity.
for analysis.

In this context, carbonate alkalinity is often called total IEC 746-2:1982, Expression of performance of
alkalinity and usually has nearly the same numerical electrochemical analyzers - Part 2: pH value.
value as methyl orange alkalinity (MO-alkalinity).

The endpoint detection, using a pH-meter is less

prone to interferences than the use of the indicator. 3 Definition

For the purposes of this part of IS0 9963, the follow-

ing definition applies.

3.1 alkalinity (A): The quantitative capacity of

2 Normative references aqueous media to react with hydrogen ions.
[ISO 6107-21
The following standards contain provisions which,
through reference in this text, constitute provisions In this method, the endpoint is chosen in such a way
of this part of IS0 9963. At the time of publication, the as to permit the full neutralization of the carbonate
editions indicated were valid. All standards are subject system.
to revision, and parties to agreements based on this
part of IS0 9963 are encouraged to investigate the A = c(HC0,) + 2c(CO;-) + c(OH-) + c(X) - c(H+)
possibility of applying the most recent editions of the
standards indicated below. Members of IEC and IS0 Usually proton acceptors (X) other than the carbonate
maintain registers of currently valid International system are present in low concentrations and can of-
Standards. ten be disregarded. Examples of such buffering sub-

1
IS0 9963-2: 1994(E) 0 IS0

stances are ammonia, phosphate, and anions of 5 Reagents

humic and other organic acids.
Use only reagents of recognized analytical grade.

Commercially available, ready-made solutions may be

4 Principle used.

Alkalinity is determined by titration with hydrochloric 5.1 Water, grade 2 in accordance with IS0 3696,
acid, with simultaneous removal of carbon dioxide. In free of interfering concentrations of acid or alkali and
this way, a precise endpoint independent of the initial with a conductivity of less than 0,l mS/m.
concentration of alkalinity can be used. The endpoint
preferably needs to be as close to neutrality as poss- 5.2 Gas, free from carbon dioxide, nitrogen or al-
ible but still low enough to allow the removal of car- ternatively a gas free from carbon dioxide obtained by
bon dioxide produced. In this part of IS0 9963, the passing air through a standing tube filled with soda
endpoint is set at pH 5,4, since the pH value can lime or another compound that absorbs carbon diox-
easily be determined with the indicator chosen. The ide. Then pass the gas through a wash bottle con-
induced systematic error is corrected by titrating a taining water and subsequently the gas distribution
blank. tube (see figure 1).

Volume about 75 ml

iTeh STANDARD PREVIEW

(standards.iteh.ai)
ISO 9963-2:1994
Glass wool https://standards.iteh.ai/catalog/standards/sist/e34092fb-d168-4c24-af32-
46234007c351/iso-9963-2-1994 Poros

Soda lime
or equivalent

Air Filter funnel

c

Figure 1 - Principle for absorption of carbon dioxide from air

0 IS0 IS0 9963-2: 1994(E)

5.3 Mixed indicator pH 5,4. where

Dissolve 0,040 g + 0,005 g of methyl red and c(HCI) is the concentration, expressed in
0,060 g + 0,005 g if bromocresol green in 100 ml of moles per litre, of the hydrochloric
ethanol r> 90 % (WV)]. Neutralize the solution with acid solution (5.5);
about 2 ml of 0,l mol/l sodium hydroxide until a
brown colour appears. Check the neutrality of the in- m is the mass, in grams, of sodium
dicator solution by titration to endpoint of one sample. carbonate taken for the preparation
If the brown colour does not remain after the addition of solution 5.4;
of 10 more drops of the indicator, adjust the pH of the is the volume, in millilitres, of sodium
indicator solution. Stored in an amber glass bottle, the carbonate solution (5.4) taken for
solution is stable for at least 6 months. titration (normally 2,0 ml);

is the volume, in millilitres, of

5.4 Sodium carbonate solution, hydrochloric acid solution (5.5) con-
sumed in the titration of the sodium
c(Na*co3J z 0,025 mol/l.
carbonate solution (5.4);
Dry sodium carbonate (Na,CO,) in an oven at
250 “C + 10 “C for 4 h. Allow to cool in a desiccator. is the volume, in millilitres, of
Dissolve I,3 g + 0,l g (weighed to the nearest hydrochloric acid solution (5.5) con-
sumed in the blank titration.
0,001 g) in waterin a 500 ml volumetric flask.

This solution is stable for at least one month if stored 6 Apparatus

in a refrigerator.
iTeh STANDARD Usual PREVIEW
lowing
laboratory equipment
should be used.
and, in particular, the fol-

5.5 Hydrochloric acid, (standards.iteh.ai)

c(HCI) z 0,020 mol/l.
6.1 Burette, preferably of total capacity 10 ml,
Dilute I,7 ml + 0,l ml of concentrated hydrochloric graduated in divisions of 0,02 ml, and conforming to
ISO 9963-2:1994the requirements of IS0 385-l.
acid (p = 1J&g/ml) tohttps://standards.iteh.ai/catalog/standards/sist/e34092fb-d168-4c24-af32-
1 000 ml with water in a
volumetric flask. 46234007c351/iso-9963-2-1994
6.2 Titration vessel, use either a glass filter funnel
An equivalent, commercially available solution can be with a porosity of 2-3 and a volume of about 75 ml,
or a gas distribution tube for dipping into the titration
vessel (an Erlenmeyer flask with a volume of
Standardize this solution at least weekly as follows. 100 ml).
Pipette 2,00 ml + 0,02 ml of the sodium carbonate
6.3 pH-meter, with a compatible electrode system
solution (5.4) into the titration vessel (6.2) and add
suitable for the measurement of pH to within
40 ml + 5 ml of water (5.1). Titrate according to the
procedure using electrodes (see 8.1) or with indicator -+ 0,05 pH units over the range 3 to 10, for use when
the endpoint determination is to be made using a
(8.2) for the endpoint detection
pH-meter. The equipment shall be set up, calibrated,
Perform at least three titrations, and record the vol- and used according to IEC 746-2.
umes (V2) of hydrochloric acid consumed. The differ-
Alterna tively, a titrator fulfilling these specifications
ence between the highest and lowest volume of
can be used.
hydrochloric acid consumed shall be less than
0,05 ml. Continue until three consecutive titrations
give the required result. Using 50 ml + 5 ml of water 7 Sampling and sample treatment
(5.1), carry out a blank determination in the same
manner and note the volume V& in millilitres, of acid Collect samples in clean polyethylene or borosilicate
consumed. glass bottles with a volume of at least 100 ml. Fill the
bottle completely with the sample and insert the
Calculate the concentration of the hydrochloric acid stopper so that no air remains inside the bottle. Ana-
using the equation lyse the samples immediately after collection. If this
is not possible, store the samples at a temperature
2mV, of 4 “C to 8 “C in order to avoid nitrification or scaling.
c(HCI) =
53,oo(v* - v3) (See IS0 5667-2.)

3
IS0 9963-2: 1994(E)

8 Procedure c(HCI)(V, - Vs>x 1 000

A=
v4
Mount the components according to figure 1.

NOTE 1 Coloured samples interfere with the indicator

endpoint determination. Such samples should be analysed A is the alkalinity of the sample, ex-
using a pH-meter. pressed in millimoles per litre;

c(HCI) is the concentration, expressed in

8.1 Endpoint detection with a pH-meter moles per litre, of the hydrochloric
acid (5.5);
Set the gas flow (5.2) to the titration vessel (6.2) at a
rate that produces abundant bubbles and transfer is the volume, in millilitres, of the
50,O ml & 0,l ml of sample (volume V4)to the vessel. sample;
Insert the pH electrodes and titrate slowly with
hydrochloric acid (5.5) to a pH value of 5,4. The pH is the volume, in millilitres, of
value has to be stable for at least 30 s, if not continue hydrochloric acid (5.5) consumed by
the titration. Note the volume V5, in millilitres, of acid the sample;
consumed.
v6 is the volume, in millilitres, of
If the volume of acid consumed exceeds 10 ml, take hydrochloric acid (5.5) consumed by
a smaller volume of the sample (V4) and dilute to the blank sample (8.3).
50 ml + 5 ml with water (5.1). In this case, the vol-
Report the result, expressed in millimoles per litre, to
ume of acid consumed shall be not less than 3 ml.
two significant digits.

8.2 Endpoint detection iTeh STANDARD

with indicator PREVIEW
9.2 Precision
Set the gas flow (5.2) to the titration vessel (standards.iteh.ai)
(6.2) at a Two interlaboratory tests performed in 1988 and 1992
rate that produces abundant bubbles and transfer gave the results shown in table 1.
50,O ml + 0,l ml of sample (volume V4)to the vessel.ISO 9963-2:1994
In two international interlaboratory
Add three drops of indicator https://standards.iteh.ai/catalog/standards/sist/e34092fb-d168-4c24-af32-
and titrate slowly with calibrations this
method was used by one laboratory, with the results
hydrochloric acid (5.5) until the colour changes 46234007c351/iso-9963-2-1994
to grey
with a trace of red. The colour has to remain for at shown in table2.
least 30 s, if not continue the titration. Note the vol-
ume Vi, in millilitres, of acid consumed. At one laboratory, a control solution with a concen-
tration of 0,200 mmol/l gave a mean value of
If the volume of acid consumed exceeds 10 ml, take 0,201 mmol/l and a coefficient of variation of 2,0 %
a smaller portion of the sample and dilute to (number of measuring values = 49).
50 ml & 5 ml with water 15.1). In this case, the vol-
ume of acid consumed shall be not less than 3 ml. 10 Test report
The test report shall include the following information:
8.3 Blank sample
a) a reference to this part of IS0 9963;
Titrate 50 ml of water (5.1) in the same way as for the
sample. Perform at least three titrations and calculate b) precise identification of the sample;
the mean value (volume V&
c) the result, expressed in millimoles per litre to two
significant digits;
9 Expression of results
d) the endpoint detection used;
9.1 Calculation
e) any departure from the procedure specified or any
Calculate the concentration of alkalinity, expressed in other circumstance that may have affected the
millimoles per litre, using the equation results.

4
 IS0 9963=2:1994(E)

Table 1 - Precision data

Mean Coefficient of
Number of
concentration variation
laboratories outliers
mmol/l
2 2,984 3,6
Drinking water 3 4,480 33
4 0,933

2 1,142
I 0,884 3,4
Natural water
1 1,406 3,O
1 1,188

Table 2 - Comparison of results using this method with other methods for the determination of
alkalinity
\
Number of Number of Concentration, mmol/l
Type of water Reference
laboratories outliers This method All methods
I
9105
Sample A NIVA 1991 20 1 0,298 0,300
Sample B 20 1 0,358 0,358

9206
Sample A
iTeh STANDARD
NIVA 1992 20
PREVIEW
13 0,042 0,047
Sample B (standards.iteh.ai)
20 13 0,151 0,155

ISO 9963-2:1994
https://standards.iteh.ai/catalog/standards/sist/e34092fb-d168-4c24-af32-
46234007c351/iso-9963-2-1994

5
IS0 9963-2: 1994(E)

Annex A
(informative)

Information on factors for the conversion of alkalinity values to alternative

units

Alkalinity values may be expressed in alternative units. Factors for the conversion from millimoles per litre are
given in table A.1.

Table A.1

Alternative unit for the expression of

Conversion factor
results

mmol/l CaCO, 0,50

mg/l CaCO, 50
English degree (= 1 Clark degree) 3,50
German degree 2,80

iTeh STANDARD
French degree
U.S. degree
PREVIEW
5,O
2,90
(standards.iteh.ai)
ISO 9963-2:1994
https://standards.iteh.ai/catalog/standards/sist/e34092fb-d168-4c24-af32-
46234007c351/iso-9963-2-1994
 IS0 9963=2:1994(E)

Annex B
(informative)

Bibliography

[I] Convention on long-range transboundary air pol- [4] ITM 1993. Comparison of testing 1992-I. Ion
lution, Intercaljbration 9105. Programme Centre, balance. (In Swedish with English summary.)
Norwegian Institute for Water Research, Oslo. Institute of Applied Environmenta Research,
University of Stockholm, Sweden.
[2] Convention on long-range transboundary air pol-
lution, Intercalibration 9206. Programme Centre, [5] SNV 3535. Intercalibration 1988-l. Chemical
Norwegian Institute for Water Research, Oslo. analysis of drinking water. (In Swedish with
English summary.) Swedish National Environ-
[3] STUMM, W. and MORGAN, J.J. Aquatic Chemis- mental Protection Agency.
try. J. Wiley (1981).

iTeh STANDARD PREVIEW

(standards.iteh.ai)
ISO 9963-2:1994
https://standards.iteh.ai/catalog/standards/sist/e34092fb-d168-4c24-af32-
46234007c351/iso-9963-2-1994