ISO 17315:2014

Petroleum products and other liquids - Ethanol - Determination of total acidity by potentiometric titration

ISO 17315:2014 specifies a test method for the determination of total acidity of ethanol by potentiometric titration. The total acidity is reported as acetic acid mass, in milligrams, per ethanol volume, in litres, or as mass percent of acetic acid (% m/m), if the density of ethanol is known.

Produits pétroliers et autres liquides — Éthanol — Dosage de l'acidité totale par titration potentiométrique

General Information

• Status: Published
• Publication Date: 02-Oct-2014
• ICS: 75.160.20 - Liquid fuels
• ICS: 75.160.40 - Biofuels
• Technical Committee: ISO/TC 28/SC 7 - Liquid Biofuels
• Drafting Committee: ISO/TC 28/SC 7 - Liquid Biofuels
• Current Stage: 9093 - International Standard confirmed
• Start Date: 03-May-2023
• Completion Date: 13-Dec-2025

Relations

• Consolidated By: ISO 7438:2016 - Metallic materials - Bend test
• Effective Date: 06-Jun-2022

Overview

ISO 17315:2014 - "Petroleum products and other liquids - Ethanol - Determination of total acidity by potentiometric titration" specifies a laboratory test method to determine the total acidity of ethanol. The method uses potentiometric titration with a standardized NaOH solution and reports acidity as acetic acid mass (mg) per litre of ethanol or as mass percent (% m/m) when the ethanol density is known. The procedure is designed for fuel-grade and industrial ethanol where low acid content is critical to prevent corrosion and ensure product quality.

Key technical topics and requirements

• Scope and purpose: Quantifies titratable acids (reported as acetic acid) in ethanol samples to support quality control and corrosion prevention.
• Sample and reagents:
  • Typical sample volume: 50 mL ethanol.
  • Reagents include deionized water, potassium hydrogen phthalate (KHP) for standardization, LiCl in ethanol as electrode electrolyte, HCl 1.0 mol/L, and NaOH 0.02 mol/L titrant (standardized potentiometrically).
• Apparatus:
  • Automatic volumetric potentiometric titrator, Ag/AgCl reference or combined glass electrode with LiCl internal electrolyte, stirrer, analytical balance, burettes, volumetric flasks.
• Calibration and procedure:
  • Electrode calibration with pH 4 and pH 7 buffers; electrode conditioning if slope < 0.91.
  • Titration parameters: dynamic addition, increments 0.01–0.05 mL, endpoint determined from the first derivative (inflection point) of the titration curve.
  • Minimize sample exposure to air (CO2 can affect acidity); maintain temperature ~20–25 °C.
• Calculations and reporting:
  • Total acidity calculated using the molarity of NaOH, volume of titrant at equivalence, and molecular mass of acetic acid (60.05 g/mol).
  • Report to nearest 0.1 mg/L or 0.0001% m/m.
• Precision:
  • Repeatability: r = 0.94 mg/L (or 0.00012 % m/m).
  • Reproducibility: R = 3.4 mg/L (or 0.00043 % m/m).

Practical applications and users

• Who uses it: fuel ethanol producers, fuel blending plants, QC/analytical laboratories, regulatory agencies, and materials engineers concerned with corrosion in storage and distribution systems.
• Why use it:
  • Ensures ethanol meets acidity limits for blending with gasoline or other fuels.
  • Identifies contamination or degradation (e.g., acetic acid formation).
  • Supports product specification compliance and long-term asset protection.

Related standards (context)

• ISO 17315:2014 is published under ISO/TC 28/SC 7 (petroleum products - laboratory testing). Laboratories should align methods with other ISO fuel analysis standards and any regional regulatory methods for ethanol fuel quality.

Keywords: ISO 17315:2014, ethanol acidity, potentiometric titration, total acidity determination, acetic acid mg/L, fuel quality control, NaOH titration.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 17315
First edition
2014-10-01
Petroleum products and other
liquids — Ethanol — Determination
of total acidity by potentiometric
titration
Produits pétroliers et autres liquides — Éthanol — Dosage de l’acidité
totale par titration potentiométrique
Reference number
©
ISO 2014
© ISO 2014
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail [e-mail]
Web www.iso.org
Published in Switzerland
ii © ISO 2014 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Terms and definitions . 1
3 Reagents and materials . 1
4 Apparatus . 3
5 Apparatus calibration . 3
6 Procedure. 3
7 Calculation . 4
8 Expression of results . 5
9 Precision . 5
9.1 General . 5
9.2 Repeatability, r .5
9.3 Reproducibility, R .6
Bibliography . 7
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO 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.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical Barriers
to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 28, Petroleum products and lubricants,
Subcommittee SC 7, Liquid biofuels.
iv © ISO 2014 – All rights reserved

Introduction
Diluted hydrous solutions of organic acids, e.g. acetic acid, can corrode many materials. Thus, it is
necessary to determine and keep at low values the acid content in the final product.
An ethanol sample can have organic acids from the productive process, from its handling, contained in
additives, or due to sample degradation or contamination. The relative content of those components can
be determined by titration with a strong alkaline solution.
The numeric result of total acidity is a measure of the amount of acid components in the sample. Total
acidity is used as a quality control parameter of final product to prevent long-run corrosion problems.
For this reason, final product obtained from a blend of ethanol and other fuels has to have a limited
acidity.
INTERNATIONAL STANDARD ISO 17315:2014(E)
Petroleum products and other liquids — Ethanol —
Determination of total acidity by potentiometric titration
WARNING — The use of this International Standard can involve hazardous materials. This
International Standard does not purport to address all the safety problems associated with its
use. It is the responsibility of the user of this International Standard to establish appropriate
safety and health practices and determine the applicability of regulatory limitations prior to use.
1 Scope
This International Standard specifies a test method for the determination of total acidity of ethanol by
potentiometric titration. The total acidity is reported as acetic acid mass, in milligrams, per ethanol
volume, in litres, or as mass percent of acetic acid (% m/m), if the density of ethanol is known.
NOTE 1 For the purposes of this International Standard, the terms “% m/m” and “% v/v” are used to represent
the mass fraction and the volume fraction of a material, respectively.
NOTE 2 This method was evaluated with ethanol samples with different water contents (0,7 % m/m and 7 %
m/m) and acidity values (5 mg to 50 mg HAc per litre of sample).
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1
total acidity
amount of acids contained in the ethanol sample, calculated as acetic acid, determined by potentiometric
titration with a strong alkaline solution, as given in this International Standard
3 Reagents and materials
3.1 Deionized water, with a maximum conductivity of 1 μS/cm, Grade 2 or equivalent.
3.2 Potassium hydrogen phthalate (KHC H O ), standard grade.
8 4 4
3.3 Solution of lithium chloride (LiCl) in ethanol, 1 mol/l to 3 mol/l.
3.4 Buffer solution, with pH 4 and pH 7.
NOTE The above values of pH are only indicative. The values shown on the buffer certificates are those which
are intended to be used in the analysis.
3.5 Hydrochloric acid solution (HCl), 1,0 mol/l, a solution prepared in accordance with the following
or a commercially available standardized hydrochloric acid solution of equivalent concentration.
— In order to prepare HCl, 1,0 mol/l, transfer (84,0 ± 0,5) ml of concentrated hydrochloric acid
(37 % v/v) to a 1 000 ml volumetric flask containing about its half capacity of water (3.1). Complete
the volume and homogenize the solution. Stock the solution in an amber flask at a temperature
below 25 °C.
— This solution has a 6 mo shelf life.
3.6 Sodium
...

DRAFT INTERNATIONAL STANDARD ISO/DIS 17315
ISO/TC 28/SC 7 Secretariat: DIN
Voting begins on Voting terminates on

2013-05-03 2013-08-03
INTERNATIONAL ORGANIZATION FOR STANDARDIZATION  •  МЕЖДУНАРОДНАЯ ОРГАНИЗАЦИЯ ПО СТАНДАРТИЗАЦИИ  •  ORGANISATION INTERNATIONALE DE NORMALISATION

Ethanol — Determination of total acidity by potenciometric
titration
Éthanol — Dosage de l'acidité totale par titration potentiométrique
ICS 75.160.20
To expedite distribution, this document is circulated as received from the committee
secretariat. ISO Central Secretariat work of editing and text composition will be undertaken at
publication stage.
Pour accélérer la distribution, le présent document est distribué tel qu'il est parvenu du
secrétariat du comité. Le travail de rédaction et de composition de texte sera effectué au
Secrétariat central de l'ISO au stade de publication.

THIS DOCUMENT IS A DRAFT CIRCULATED FOR COMMENT AND APPROVAL. IT IS THEREFORE SUBJECT TO CHANGE AND MAY NOT BE
REFERRED TO AS AN INTERNATIONAL STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS BEING ACCEPTABLE FOR INDUSTRIAL, TECHNOLOGICAL, COMMERCIAL AND USER PURPOSES, DRAFT
INTERNATIONAL STANDARDS MAY ON OCCASION HAVE TO BE CONSIDERED IN THE LIGHT OF THEIR POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN NATIONAL REGULATIONS.
RECIPIENTS OF THIS DRAFT ARE INVITED TO SUBMIT, WITH THEIR COMMENTS, NOTIFICATION OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPORTING DOCUMENTATION.
©  International Organization for Standardization, 2013

ISO/DIS 17315
©  ISO 2013
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any
means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission.
Permission can be requested from either ISO at the address below or ISO’s member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail [e-mail]
Web www.iso.org
Published in Switzerland
ii © ISO 2013 – All rights reserved

ISO/NP 17315
Contents Page
Foreword . iv
0 Introduction . iv
0.1 Warning . iv
0.2 Significance and use . iv
1 Scope . 1
2 Term and definition . 1
2.1 Total acidity . 1
3 Reagents and materials . 1
4 Apparatus . 2
5 Apparatus calibration . 3
6 Procedure . 3
7 Calculation. 4
8 Expression of results . 4
9 Repeatability, r . 5
10 Reproducibility, R . 5

ISO/
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
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. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO/NP 17315 was prepared by Technical Committee ISO TC 28/SC 07/WG4.
0 Introduction
0.1 Warning
The use of this Standard may involve hazardous materials. This Standard does not purport to address all the
safety problems associated with its use. It is responsibility of the user of this Standard to establish appropriate
safety and health practices and determine the applicability of regulatory limitations prior to use.
0.2 Significance and use
Diluted hydrous solutions of organic acids, e.g. acetic acid, can corrode many materials. Thus, it is necessary
to determine and keep at low values the acid content in the final product.
An ethanol sample may have organic acids from the productive process, from its handling, contained in
additives, or due to sample degradation or contamination. The relative content of those components may be
determined by titration with a strong alkaline solution.
The numeric result of total acidity is a measure of the amount of acid components in the sample. Total acidity
is used as a quality control parameter of final product to prevent long-run corrosion problems.
For this reason, final product obtained from a blend of ethanol and others fuels must have a limited acidity.
iv © ISO 2012 – All rights reserved

ISO/NP 17315
Ethanol — Determination of total acidity by potenciometric
titration
1 Scope
This Standard specifies a test method for the determination of total acidity of ethanol by potentiometric titration.
The total acidity is reported as acetic acid mass (in mg) per ethanol volume (in l), or as mass percent of acetic
acid (% m/m), if the density of ethanol is known.
2 Term and definition
For the purposes of this Standard the following definition applies:
2.1 Total acidity
Amount of acids contained in the ethanol sample that can be titrated with a strong alkaline solution.
NOTE In this Standard total acidity is reported as acetic acid mass (in mg) per ethanol volume (in l), or as mass
percent of acetic acid (% m/m), if the density of ethanol is known.
3 Reagents and materials
3.1 Deionized water with a maximum conductivity of 1 μS/cm.
3.2 Potassium hydrogen phthalate (KHC H O ), reagent grade.
8 4 4
3.3 Solution of lithium chloride (LiCl) in ethanol, 1-3 mol/l.
3.4 Buffer solution with pH 4 and pH 7.
NOTE The above values of pH are only indicative. It shall
...