ISO 4626:2023

Volatile organic liquids - Determination of boiling range of organic solvents used as raw materials

This document specifies a method for determining the boiling range of liquids that boil between 30 °C and 300 °C at normal pressure, and that are chemically stable and do not corrode the apparatus during the distillation. The method is applicable to organic liquids such as hydrocarbons, esters, alcohols, ketones, ethers and similar products. NOTE 1 The method differs from that described in ISO 918 with respect to the volume of the distillation flask, the type of cooler and the distillation receiver. NOTE 2 The method differs from that specified in ISO 3405 with respect to the volume of the distillation flask and the diameter of the hole in the flask support.

Liquides organiques volatils — Détermination de l’intervalle de distillation des solvants organiques utilisés comme matières premières

General Information

• Status: Published
• Publication Date: 30-Jul-2023
• ICS: 87.060.30 - Solvents
• Technical Committee: ISO/TC 35 - Paints and varnishes
• Drafting Committee: ISO/TC 35 - Paints and varnishes
• Current Stage: 6060 - International Standard published
• Start Date: 31-Jul-2023
• Due Date: 09-Feb-2024
• Completion Date: 31-Jul-2023

Relations

• Revises: ISO 4626:1980 - Volatile organic liquids - Determination of boiling range of organic solvents used as raw materials
• Effective Date: 27-May-2023

Overview

ISO 4626:2023 specifies a standardized laboratory method for determining the boiling range of volatile organic liquids used as raw materials. The procedure is intended for chemically stable, non‑corrosive organic solvents with normal‑pressure boiling points between 30 °C and 300 °C. Typical product classes covered include hydrocarbons, esters, alcohols, ketones, ethers and similar solvents. The test is a simple batch distillation using a defined flask size and controlled operating conditions to record initial boiling point, dry point and end point.

Key topics and technical requirements

• Scope and applicability: Liquids boiling 30–300 °C, chemically stable and non‑corrosive during distillation.
• Principle: Distillation of a 100 ml test portion under prescribed conditions equivalent to simple batch distillation; systematic recording of thermometer readings and condensate volumes with correction to standard atmospheric pressure.
• Apparatus: Specified components include a 200 ml heat‑resistant distillation flask, specified condenser and receiver configurations, and approved mercury‑in‑glass thermometers with defined calibration and correction procedures.
• Thermometer and correction rules: Requirements for thermometer aging, thermometer bore and bulb corrections, and barometer correction to report values at standard pressure.
• Procedure details: Assembly, filling of cooling bath, sample preparation, operating conditions for materials above/below 150 °C, and definitions of initial boiling point, dry point and end point.
• Quality and precision: Guidance on repeatability and reproducibility, recovery and distillation loss calculations.
• Safety and notes: Precautions covering peroxide formation, flammability and safe heating methods; informative Annex B includes a peroxide test.
• Normative references: ISO 3165 (sampling safety) and ISO 15528 (sampling for paints/varnishes).
• Differences from related methods: Notes on how ISO 4626 differs from ISO 918 and ISO 3405 in flask volume, condenser/receiver type and flask support details.
• Annexes: Annex A (normative) on thermometer specifications and correction factors; Annex B (informative) on peroxide testing.

Applications and users

ISO 4626 is practical for:

• Quality control laboratories verifying incoming organic solvent raw materials.
• Manufacturers of paints, varnishes and coatings and their raw‑material suppliers (ISO/TC 35 context).
• R&D and formulation labs assessing solvent volatility and batch consistency.
• Organizations preparing Safety Data Sheets (SDS) and regulatory submissions that require standardized boiling‑range data.
• Third‑party testing labs providing conformity and comparative testing.

Using ISO 4626 helps ensure consistent, comparable boiling‑range results, aids process control, supports product specification compliance, and improves safety handling decisions for volatile organic liquids.

Related standards

• ISO 918 (other solvent distillation methods) - differs in flask volume, cooler and receiver.
• ISO 3405 (distillation for petroleum products) - differs in flask volume and flask support design.
• ISO 3165, ISO 15528 - sampling and safety references applicable to implementation.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 4626
Second edition
2023-07
Volatile organic liquids —
Determination of boiling range of
organic solvents used as raw materials
Liquides organiques volatils — Détermination de l’intervalle
de distillation des solvants organiques utilisés comme matières
premières
Reference number
© ISO 2023
All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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
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or ISO’s member body in the country of the requester.
ISO copyright office
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Phone: [phone]
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Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus . 2
6 Sampling . 9
7 Assembly and preparation of apparatus .10
7.1 Assembly . 10
7.1.1 General . 10
7.1.2 Position and choice of thermometer . 10
7.1.3 Support for flask . 10
7.1.4 Connection of flask to condenser . . 10
7.2 Filling of cooling bath . 10
7.3 Adjustment of temperature of sample . 10
8 Procedure .11
8.1 Test portion . 11
8.2 Apparatus assembly . 11
8.3 Operating conditions . 11
8.3.1 General . 11
8.3.2 Materials with boiling point below 150 °C . 11
8.3.3 Materials with boiling point above 150 °C . 11
8.4 Initial boiling point .12
8.5 Distillation .12
8.6 Dry point .12
8.7 End point . 12
8.8 Atmospheric pressure .12
8.9 Recovery .12
8.10 Distillation loss . .12
9 Notes on procedure .13
9.1 Factors causing superheating . 13
9.2 Flame in contact with the flask .13
9.3 Application of heat . 13
9.4 Extraneous heat source . 13
9.5 Condition of equipment. 13
9.6 Use of electric heaters .13
9.7 Safety precautions .13
9.7.1 Peroxide formation . .13
9.7.2 Flammability . 14
10 Calculations .14
10.1 Thermometer bore correction . 14
10.2 Thermometer bulb shrinkage correction . 14
10.3 Barometer correction . 14
10.4 Combined corrections . 15
10.5 Precision . . . 15
10.5.1 General .15
10.5.2 Repeatability, r .15
10.5.3 Reproducibility, R .15
11 Test report .16
iii
Annex A (normative) Thermometer to be used, normal boiling point and boiling point
correction factor .17
Annex B (informative) Test for peroxides .20
Bibliography .21
iv
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
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described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO document should be noted. This document was drafted in accordance with the
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www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 35, Paints and varnishes.
This second edition results from the reinstatement of ISO 4626:1980, which was withdrawn in 2017.
The main changes are as follows:
— the normative references have been updated.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
v
INTERNATIONAL STANDARD ISO 4626:2023(E)
Volatile organic liquids — Determination of boiling range
of organic solvents used as raw materials
1 Scope
This document specifies a method for determining the boiling range of liquids that boil between 30 °C
and 300 °C at normal pressure, and that are chemically stable and do not corrode the apparatus during
the distillation.
The method is applicable to organic liquids such as hydrocarbons, esters, alcohols, ketones, ethers and
similar products.
NOTE 1 The method differs from that described in ISO 918 with respect to the volume of the distillation flask,
the type of cooler and the distillation receiver.
NOTE 2 The method differs from that specified in ISO 3405 with respect to the volume of the distillation flask
and the diameter of the hole in the flask support.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 3165, Sampling of chemical products for industrial use — Safety in sampling
ISO 15528, Paints, varnishes and raw materials for paints and varnishes — Sampling
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
initial boiling point
temperature noted (corrected if required) at the moment when the first drop of condensate falls from
the tip of the condenser during a distillation carried out under standardized conditions
3.2
dry point
temperature noted (corrected if required) at the moment of vaporization of the last drop of liquid at the
bottom of the flask during a distillation carried out under standardized conditions, disregarding any
liquid on the side of the flask and on the thermometer
3.3
boiling range
temperature interval between the initial boiling point (3.1) and the dry point (3.2)
3.4
end point
final boiling point
maximum temperature noted (corrected, if required) during the final phase of a distillation carried out
under standardized conditions
4 Principle
100 ml of a test portion are distilled under prescribed conditions which are equivalent to a simple batch
distillation. Thermometer readings and volumes of condensate are observed systematically and the
results from these data with correction to standard atmospheric pressure are calculated.
5 Apparatus
The apparatus, a suitable form of which is shown in Figure 1 to Figure 4, shall comprise the following
items.
5.1 Distillation flask, of heat-resistant glass, of capacity 200 ml, conforming to the dimensions
shown in Figure 1.
Superheating of liquid in a new flask may be prevented by depositing a small amount of carbon in the
bottom of the flask. This may be accomplished by heating and decomposing a pinch of tartaric acid in
the bottom of the flask. The flask is then prepared for use by washing with water, rinsing with acetone,
and drying.
An exception is made for diacetone alcohol: in order to avoid an erratic value for the initial boiling point,
the distillation flask should be clean and free of any residual carbon deposit.
5.2 Thermometers, mercury-in-glass type, nitrogen-filled, graduated on the stem, enamel-backed,
and conforming to the requirements in Table 1.
The thermometer should have been artificially aged by means of a suitable treatment before graduation,
in order to ensure stability of the lowest point on the scale. This treatment should have been such that,
after the procedure described below, the rise at a fiducial point is not greater than the maximum error
specified, and the accuracy of the thermometer is within the limits specified.
Heat the thermometer to a temperature equal to its highest reading and keep it at this temperature for
5 min. Allow the thermometer to cool, either naturally in still air or slowly in the test bath (at a specified
rate), to 20 °C above ambient temperature or to 50 °C, whichever is the lower, and then determine the
lowest point on the scale. If rapid cooling is used, the lowest point on the scale shall be determined
within 1 h. Heat the thermometer again to a temperature equal to its highest reading, keep it at this
temperature for 24 h. Allow the thermometer to cool to 20 °C above ambient temperature or to 50 °C, at
the same rate as at the start of the test, and re-determine the lowest point on the scale under the same
conditions as before.
Dimensions in millimetres
Key
1 reinforcing bead
2 fire-polished
Figure 1 — Distillation flask
Table 1 — Solvent distillation thermometers
a
Designation 38 C-75 39 C-75 40 C-75 41 C-62 42 C-62 102 C-65 103 C-65 104 C-75 105 C-65 106 C-75 107 C-75
Immersion 100 100 100 100 100 100 100 100 100 100 100
mm
Range 24 to 78 48 to 102 72 to 126 98 to 152 95 to 255 123 to 177 148 to 202 173 to 227 198 to 252 223 to 277 248 to 302
°C
Graduation 0,2 0,2 0,2 0,2 0,5 0,2 0,2 0,2 0,2 0,2 0,2
°C
Longer lines at each 1 1 1 1 1 1 1 1 1 1 1
°C
Figured at each 2 2 2 2 5 2 2 2 2 2 2
°C
0,2 0,2 0,2 0,2 0,5 0,2 up to 0,4 0,4 0,4 up to 0,8 1,0
Scale error not to exceed 150 225
°C 0,3 over 0,6 over
150 225
Overall length 395 ± 5 395 ± 5 395 ± 5 395 ± 5 395 ± 5 395 ± 5 395 ± 5 395 ± 5 395 ± 5 395 ± 5 395 ± 5
mm
Stem diameter 6,0 to 7,0 6,0 to 7,0 6,0 to 7,0 6,0 to 7,0 6,0 to 7,0 6,0 to 7,0 6,0 to 7,0 6,0 to 7,0 6,0 to 7,0 6,0 to 8,0 6,0 to 8,0
mm
Bulb length 15 to 20 15 to 20 15 to 20 15 to 20 15 to 20 15 to 20 15 to 20 15 to 20 15 to 20 15 to 20 15 to 20
mm
Distance from bottom of bulb
—  to 24 °C 48 °C 72 °C 98 °C 95 °C 123 °C 148 °C 173 °C 198 °C 23 °C 248 °C
125 mm to 125 mm to 125 mm to 125 mm to 125 mm to 125 mm to 125 mm to 125 mm to 125 mm to 125 mm to 125 mm to
145 mm 145 mm 145 mm 145 mm 145 mm 145 mm 145 mm 145 mm 145 mm 145 mm 145 mm
—  to 78 °C 102 °C 126 °C 152 °C 255 °C 177 °C 202 °C 227 °C 252 °C 277 °C 302 °C
335 mm to 335 mm to 335 mm to 335 mm to 335 mm to 335 mm to 335 mm to 335 mm to 335 mm to 335 mm to 335 mm to
360 mm 360 mm 360 mm 360 mm 360 mm 360 mm 360 mm 360 mm 360 mm 360 mm 360 mm
Expansion chamber to allow
heating to 105 130 150 180 280 200 225 250 275 300 325
°C
a
These designations correspond to those in ASTM E1.

5.3 Draught screen
5.3.1 For use with a gas burner
The draught screen shall be rectangular in cross-section and open at the top and bottom. It shall have
the dimensions shown in Figure 2 and be made of a sheet of metal, approximately 0,8 mm thick.
In each of the two narrower sides of the draught screen, there shall be two circular holes of diameter of
25 mm, the centres of which are situated 215 mm below the top of the shield, as shown in Figure 2.
In each of the four sides of the draught screen, there shall be three circular holes of diameter 12,5 mm,
the centres of which are situated 25 mm above the base of the draught screen. These holes shall occupy
the positions shown in Figure 2.
At the middle of each of the wider sides, a vertical slot for the condenser tube, dimensioned
approximately as shown in Figure 2, shall be cut downwards from the top of the screen. A removable
shutter of suitable dimensions shall be provided for closing whichever vertical slot is not in use. This
arrangement enables the condenser (5.6) to be placed on either side of the draught screen.
A shelf of ceramic material, of thickness 3 mm to 6 mm and possessing a centrally cut circular hole of
diameter 75 mm to 100 mm, shall be supported horizontally in the screen and shall fit closely to the
sides of the screen, to ensure that hot gases from the source of heat (5.5) do not come in contact with
the sides or neck of the flask (5.1). The supports for this shelf may conveniently consist of triangular
pieces of metal sheet firmly fixed to the screen at its four corners.
A board as described in 5.4 shall rest on this shelf.
In one of the narrower sides of the screen, a door shall be provided, having the approximate dimensions
shown in Figure 2 and overlapping the opening in the screen by approximately 5 mm all round.
Dimensions in millimetres
Key
1 window
2 door
3 tap
4 overflow tube
5 water bath, capacity not less than 5,5 l of cooling medium (approximately 380 mm long, 150 mm deep and
100 mm wide)
6 seamless brass tubing, external diameter 14 mm
7 blotting paper
8 asbestos or ceramic board
9 asbestos or ceramic shelf
a
Approximate dimensions, given for guidance.
Figure 2 — Distillation apparatus using gas burner
5.3.2 For use with an electric heater
When an electric heater is employed, the portion of the draught screen above the shelf shall be as
described in 5.3.1, but the lower portion (including the shelf) may be modified or omitted, provided that
the change does not expose the distillation flask to draughts (see Figure 3). Provision shall be made to
adjust the shelf to facilitate fitting of the flask.
Key
1 thermometer
2 flask
3 ceramic board
4 electric heating mantle
5 flask support platform
6 flask adjusting knob
7 heat adjusting dial
8 switch
9 open bottom shield
10 distillation receiver
11 blotting paper
12 condenser
13 condenser tube
14 shield
Figure 3 — Distillation apparatus using electric heater
5.4 Ceramic boards, of thickness 3 mm to 6 mm, with central holes of diameter 32 mm or 38 mm
respectively, and overall dimensions not less than 150 mm . When a gas heater is employed, this board
shall rest on the shelf described in 5.3.1. When an electric heater is employed, the same arrangement
shall be adopted if the shelf is present. Alternatively, the board may be placed directly on the heater or
it may form the top of the heater. Provision shall be made for adjusting the height of the heater.
Whichever type of heater is employed, direct heat shall only be applied to the flask through the central
hole in the ceramic board.
5.5 Source of heat, comprising either a gas burner constructed so that sufficient heat can be obtained
to distil the product at the uniform rate specified in 8.3.2 (a sensitive regulating valve or governor are
desirable adjuncts) or an electric heater capable of complying with the same requirements. (A heater of
low heat retention, adjustable from 0 kW to 1 kW, has been found satisfactory.) See also 9.6.
5.6 Condenser, of seamless brass tubing, of length 560 mm, outside diameter 14 mm and wall
thickness 0,8 mm to 0,9 mm, surrounded by a metal cooling bath, preferably of copper or brass. The
tube shall be set so that a length of approximately 390 mm is in contact with the cooling medium in the
cooling bath, with about 50 mm outside the cooling bath at the
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