ISO/DIS 11277

SLOVENSKI STANDARD
01-oktober-2025
Kakovost tal - Določanje porazdelitve velikosti delcev v mineralnem delu tal -
Metoda s sejanjem in usedanjem
Soil quality - Determination of particle size distribution in mineral soil material - Method
by sieving and sedimentation
Qualité du sol - Détermination de la répartition granulométrique de la matière minérale
des sols - Méthode par tamisage et sédimentation
Ta slovenski standard je istoveten z: ISO/DIS 11277
ICS:
13.080.20 Fizikalne lastnosti tal Physical properties of soils
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
International
Standard
ISO/DIS 11277
ISO/TC 190/SC 3
Soil quality — Determination of
Secretariat: DIN
particle size distribution in mineral
Voting begins on:
soil material — Method by sieving
2025-05-23
and sedimentation
Voting terminates on:
2025-08-15
Qualité du sol — Détermination de la répartition
granulométrique de la matière minérale des sols — Méthode par
tamisage et sédimentation
ICS: 13.080.20
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS AND APPROVAL. IT
IS THEREFORE SUBJECT TO CHANGE
AND MAY NOT BE REFERRED TO AS AN
INTERNATIONAL STANDARD UNTIL
PUBLISHED AS SUCH.
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STANDARDS MAY ON OCCASION HAVE TO
This document is circulated as received from the committee secretariat.
BE CONSIDERED IN THE LIGHT OF THEIR
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Reference number
DRAFT
International
Standard
ISO/DIS 11277
ISO/TC 190/SC 3
Soil quality — Determination of
Secretariat: DIN
particle size distribution in mineral
Voting begins on:
soil material — Method by sieving
and sedimentation
Voting terminates on:
Qualité du sol — Détermination de la répartition
granulométrique de la matière minérale des sols — Méthode par
tamisage et sédimentation
ICS: 13.080.20
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENTS 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,
© ISO 2025
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
STANDARDS MAY ON OCCASION HAVE TO
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Published in Switzerland Reference number
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 2
5 Principle . 2
6 Field sampling . 3
7 Sample preparation . 4
8 Dry sieving (material >2 mm) . 4
8.1 General .4
8.2 Apparatus .4
8.3 Procedure .5
8.4 Calculation and expression of results .6
9 Wet sieving and sedimentation (material <2 mm) . 6
9.1 General .6
9.2 Apparatus .6
9.3 Reagents .14
9.4 Calibrations . 15
9.4.1 Sampling pipette (see Figure 4) . 15
9.4.2 Dispersing-agent correction . 15
9.5 Test sample . 15
9.6 Destruction of organic matter .16
9.7 Removal of soluble salts and gypsum .17
9.8 Removal of carbonates .18
9.9 Removal of iron oxides .18
9.10 Dispersion .19
9.11 Wet sieving at 0,063 mm.19
9.12 Sedimentation .19
9.13 Calculation of results for fractions <2 mm . 20
10 Test report .21
Annex A (normative) Determination of particle size distribution of mineral soil material that
is not dried prior to analysis .22
Annex B (normative) Determination of particle size distribution of mineral soils by a
hydrometer method following destruction of organic matter .25
Annex C (informative) Precision of the method .34
Annex D (informative) Ultrasonic bath assisted wet sieving and sedimentation.36
Bibliography .38

iii
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
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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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
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Organization (WTO) principles in the Technical Barriers to Trade (TBT) see www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 190, Soil quality, Subcommittee SC 3, Chemical
and physical characterization.
This fourth edition cancels and replaces the third edition (ISO 11277:2020), which has been technically
revised and the first edition of ISO 11277:2020/Amd 1:2024. The main changes compared to the previous
edition are as follows:
— Incorporation of ISO 11277:2020/Amd 1:2024;
— Document has been editorially revised.
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.

iv
Introduction
The physical and chemical behaviour of soils is controlled in part by the amounts of mineral particles of
different sizes in the soil. The subject of this document is the quantitative measurement of such amounts
(expressed as a proportion or percentage of the total mass of the mineral soil), within stated size classes.
The determination of particle size distribution is affected by organic matter, soluble salts, cementing agents
(like iron compounds), relatively insoluble substances such as carbonates and sulfates, or combinations of
these. Some soils change their behaviour to such a degree, upon drying, that the particle size distribution
of the dried material bears little or no relation to that of the undried material encountered under natural
conditions. This is particularly true of soils rich in organic matter, those developed from recent volcanic
deposits, some highly weathered tropical soils, and soils often described as “cohesive” (see Reference [4]).
Other soils, such as the so-called “sub-plastic” soils of Australia, show little or no tendency to disperse under
normal laboratory treatments, despite field evidence of large clay content.
The procedures given in this document recognize these kinds of differences between soils from different
environments, and the methodology presented is designed to deal with them in a structured manner.
Such differences in soil behaviour can be very important, but awareness of them depends usually on local
knowledge. Given that the laboratory is commonly distant from the site of the field operation, the information
supplied by field teams becomes crucial to the choice of an appropriate laboratory procedure. This choice
can be made only if the laboratory is made fully aware of this background information.

v
DRAFT International Standard ISO/DIS 11277:2025(en)
Soil quality — Determination of particle size distribution in
mineral soil material — Method by sieving and sedimentation
WARNING — Persons using this document should be familiar with usual laboratory practice. This
document does not purport to address all of the safety problems, if any, associated with its use. It
is the responsibility of the user to establish appropriate safety and health practices and to ensure
compliance with any national regulatory conditions.
IMPORTANT — It is absolutely essential that tests, conducted in accordance with this document, be
carried out by suitably qualified staff.
1 Scope
This document specifies a basic method of determining the particle size distribution applicable to a wide
range of mineral soil materials, including the mineral fraction of organic soils. It also offers procedures to
deal with the less common soils mentioned in the introduction. This document has been developed largely
for use in the field of environmental science, and its use in geotechnical investigations is something for
which professional advice might be required.
A major objective of this document is the determination of enough size fractions to enable the construction
of a reliable particle-size-distribution curve.
This document does not apply to the determination of the particle size distribution of the organic
components of soil, i.e. the more or less fragile, partially decomposed, remains of plants and animals. It
is also realized that the chemical pre-treatments and mechanical handling stages in this document could
cause disintegration of weakly cohesive particles that, from field inspection, might be regarded as primary
particles, even though such primary particles could be better described as aggregates. If such disintegration
is undesirable, then this document is not used for the determination of the particle size distribution of such
weakly cohesive materials.
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 565, Test sieves — Metal wire cloth, perforated metal plate and electroformed sheet — Nominal sizes of
openings
ISO 3310-1, Test sieves — Technical requirements and testing — Part 1: Test sieves of metal wire cloth
ISO 3310-2, Test sieves — Technical requirements and testing — Part 2: Test sieves of perforated metal plate
ISO 11265, Soil quality — Determination of the specific electrical conductivity
ISO 11464, Soil quality — Pretreatment of samples for physico-chemical analysis
3 Terms and definitions
There are no normative references in this document.

4 Symbols
The following symbols are found throughout the text and, where appropriate, units and quantities are as
given below (the SI convention is followed for common units, e.g. g = gram; m = metre; mm = millimetre;
s = second, etc.).
Mg megagram (10 g)
5 Principle
The particle size distribution is determined by a combination of sieving and sedimentation, starting from
air-dried soil (see Reference [4]). A method for undried soil is given in Annex A. Particles not passing a 2 mm
aperture sieve are determined by dry sieving. Particles passing such a sieve, but retained on a 0,063 mm
aperture sieve, are determined by a combination of wet and dry sieving, whilst particles passing the latter
sieve are determined by sedimentation.
The pipette method is preferred. As an alternative, the hydrometer method is given in Annex B. A combination
of sieving and sedimentation enables the construction of a continuous particle-size-distribution curve.
The key points in this procedure are summarized as a flow chart in Figure 2. This document requires that
the proportions of fractions separated by sedimentation and sieving be determined from the masses of such
fractions obtained by weighing. Other methods of determining the mass of such fractions rely on such things
as the interaction of particles with electromagnetic radiation or electrical fields (see Reference [2]). There
are often considerable difficulties in relating the values obtained by these different methods for the same
sample. It is one of the intentions of this document that close adherence to its details should help minimize
interlaboratory variation in the determination of the particle size distribution of mineral soils. Therefore,
the proportions of fractions shall be determined only by weighing. If this is not the method used, then
conformance with this document cannot be claimed in the test report (see Clause 10).
Both the pipette and hydrometer methods assume that the settling of particles in the sedimentation cylinder is
in accordance with Stokes's Law (see References [2], [4] and [7]), and the constraints that this implies, namely:
a) the particles are rigid, smooth spheres;
b) the particles settle in laminar flow, i.e. the Reynolds Number is less than about 0,2; this constraint sets
an upper equivalent spherical particle diameter (see below) slightly greater than 0,06 mm for Stokesian
settling under gravity (Reference [2]);
c) the suspension of particles is sufficiently dilute to ensure that no particle interferes with the settling of
any other particle;
d) there is no interaction between the particle and fluid;
e) the diameter of the suspension column is large compared to the diameter of the particle, i.e. the fluid is
of “infinite extent”;
f) the particle has reached its terminal velocity;
g) the particles are of the same relative density.
Thus, the diameter of a particle is defined in terms of the diameter of a sphere whose behaviour in suspension
matches that of the particle. This is the concept of equivalent spherical diameter. It is the principle upon which
the expression of the diameter of particles, as derived from sedimentation, is based in this document.
Stokes's Law can be written, for the purposes of this document, as in Formula (1):
 
th=−18ηρ/ ()ρ gd (1)
sw p
 
where
t is the settling time, in seconds, of a particle of diameter d (see below);
p
η is the dynamic viscosity of water at the test temperature (see Table B.2), in millipascals per second;
h is the sampling depth, in centimetres;
ρ is the mean particle density, in megagrams per cubic metre (taken as 2,65 Mg/m ; see note);
s
ρ is the density of the liquid containing the soil suspension, in megagrams per cubic metre (taken
w
as 1,00 Mg/m ; see note);
g is the acceleration due to gravity, in centimetres per second squared (taken as 981 cm/s );
d is the equivalent spherical diameter of the particle of interest, in millimetres.
p
NOTE 1 It is realized that there are considerable differences between the densities of soil particles, but for the
purposes of this document it is assumed that the mean particle density is that of quartz, i.e. 2,65 Mg/m (Reference [8]),
3 3
as this is the commonest mineral in a very wide range of soils. The density of water is 0,998 2 Mg/m and 0,995 6 Mg/m
at 20 °C and 30 °C, respectively (see Reference [6]). Given the effect of the addition of a small amount of dispersant (see
9.3.2), the density of water is taken as 1,000 0 Mg/m over the permitted temperature range of this document (see 9.2.2).
Furthermore, for routine use, it is recommended that the sampling times be converted to minutes and/or
hours, as appropriate, to lessen the risk of error (see Table 3).
Particles within particular size ranges or classes are commonly described as cobbles, gravel, coarse sand,
silt, etc. The meaning of such trivial names differs between countries, and in some cases there are no
exact translations of such words from one language to another; for example, the Dutch word “zavel” has no
equivalent in English. The only fraction for which there appears to be common agreement is clay, which is
defined as material of less than 0,002 mm equivalent spherical diameter (References [4]). Such trivial names
shall not be used in describing the results of particle size determination according to this document. Phrases
such as “. passing a 20 mm aperture sieve .” or “. less than 0,063 mm equivalent spherical diameter .”
shall be used instead. If trivial names shall be used, for example, to cross-reference to another International
or National Standard, then the trivial name should be defined explicitly, so as to remove any doubt as to
the meaning intended, e.g. silt (0,063 mm to 0,002 mm equivalent spherical diameter) (see Clause 4).
Furthermore, it is common to use the word “texture” to describe the results of particle-size-distribution
measurements, e.g. “the particle size of this soil is of clay texture”. This is incorrect as the two concepts are
different, and the word “texture” shall not be used in the test report (see Clause 10) to describe the results
obtained by the use of this document.
6 Field sampling
The mass of sample taken in the field shall be representative of the particle size distribution, especially if the
amount of the larger particles is to be determined reliably. Table 1 gives recommended minimum masses.
Table 1 — Mass of soil sample to be taken for sieving
Maximum size of material forming > 10 % of the soil Minimum mass of sample to be taken for sieving
(given as test sieve aperture, in mm) kg
63 50
50 35
37,5 15
28 6
20 2
14 1
10 0,5
TTabablele 1 1 ((ccoonnttiinnueuedd))
Maximum size of material forming > 10 % of the soil Minimum mass of sample to be taken for sieving
(given as test sieve aperture, in mm) kg
6,3 0,5
5 0,2
2 or smaller 0,1
7 Sample preparation
Samples shall be prepared in accordance with the methods given in ISO 11464.
NOTE For many purposes, particle size distribution is determined only for the fraction of the soil passing a 2 mm
aperture sieve. In this case, the test sample (9.5) can be taken either according to the procedures in ISO 11464 or from
the material passing a 2 mm aperture sieve according to 8.2.
8 Dry sieving (material >2 mm)
8.1 General
The procedure specified in this clause applies to material retained on a 2 mm aperture sieve. Table 2 gives
the maximum mass which shall be retained on sieves of different diameters and apertures. If more than this
amount of material is retained, then it shall be subdivided appropriately and sieved again.
It is common to refer to sieves as having a particular mesh-size or mesh number. These are not the same as
the sieve aperture, and the relationship between the various numbers is not immediately obvious. The use
of mesh numbers as a measurement of particle size is difficult to justify, and shall not be used in reporting
the results of this document.
8.2 Apparatus
8.2.1 Test sieves, with apertures according to ISO 565, and with well-fitting covers and receivers.
The full range of sieves appropriate to the largest particle(s) present should be used (see Table 1 and 9.2.3).
The apertures chosen shall be stated in the test report (Clause 10). The accuracy of the sieves shall be verified
monthly against a set of master sieves kept for this purpose, using an accepted method such as particle
reference materials, microscopy, etc. (see Reference [2]) depending on the sieve aperture. Tolerances shall
meet the requirements of ISO 3310-1 and ISO 3310-2. Sieves that do not meet these specifications shall be
discarded. A record shall be kept of such testing.
Brass sieves are particularly liable to splitting and distortion, and steel sieves are strongly recommended
for the larger apertures.
Special care shall be taken to ensure that covers and receivers do not leak. Sieves shall be inspected weekly
when in regular use, and on every occasion if used less often. A record shall be kept of such inspections.
Round-hole sieves shall not be used.
8.2.2 Balance, capable of weighing to an accuracy of within ±0,5 g.
8.2.3 Mechanical sieve shaker.
It is usually impracticable to sieve mechanically at sieve apertures much greater than 20 mm, unless very
heavy-duty equipment is available. Mechanical sieve shaking is essential to sieve efficiency at smaller
apertures.
8.2.4 A sieve brush and a stiff brush.

8.2.5 Ultrasonic bath, able to provide an acoustic power P (W) level in the range of 5 W to 20 W per litre
ac
of water (see Annex D), typically operating at a frequency between 37 kHz to 45 kHz.
8.3 Procedure
Weigh the dry test sample, prepared in accordance with ISO 11464, to the nearest 0,5 g (m ). Place the
weighed material on the 20 mm sieve, and by brushing the material gently over the sieve apertures with the
stiff brush (to remove any adhering soil), sieve the material. Take care not to detach any fragments from the
primary particles. Sieve the retained material on the nest of sieves of selected apertures (8.2.1) and record
the amount retained on each sieve to the nearest 0,5 g. Do not overload the sieves (see Table 1) but sieve the
material in portions if necessary.
Weigh the material passing the 20 mm aperture sieve (m ), or a suitable portion of it (m ) (see Table 2)
2 3
obtained by an appropriate subsampling method (see Clause 6), and place this on a nest of sieves, the
lowermost having an aperture of 2 mm. Shake the sieves mechanically until no further material passes any
of the sieves (see Note). Record the mass of material retained on each sieve and the mass passing the 2 mm
aperture sieve.
The total mass of the fractions should be within 1 % of m or m , as appropriate. If it is not, then check for
2 3
sieve damage and discard sieves as appropriate (see 8.2.1).
NOTE For practical purposes, it is usual to choose a standard sieve shaking time which gives an acceptable degree
of sieving efficiency with a wide range of soil materials. The minimum recommended period is 10 min.
Table 2 — Maximum mass of material to be retained on each test sieve at the completion of sieving
Test sieve Maximum mass
aperture
kg
Sieve diameter
mm
mm 450 400 300 200 100
50 10 8,9 4,5 — —
37,5 8 7,1 3,5 — —
28 6 5,3 2,5 — —
20 4 3,6 2 — —
14 3 2,7 1,5 — —
10 2 1,8 1 — —
6,3 1,5 1,3 0,75 — —
5 1 0,9 0,5 — —
3,35 — — 0,3 0,15
2 — — 0,2 0,1
1,18 — — 0,1 0,05
0,6 — — 0,075 0,037 5
0,425 — — 0,075 0,037 5
0,3 — — 0,05 0,025
0,212 — — 0,05 0,025
0,15 — — 0,04 0,02
0,063 — — 0,025 0,012 5
8.4 Calculation and expression of results
For the material retained by the 20 mm and larger aperture sieves, calculate the proportion by mass retained
by each sieve as a proportion of m . For example (Formula (2)):
Proportionretainedonthem20 msieve=[]mm()20mm / (2)
For the material passing the 20 mm sieve, multiply the mass of material passing each sieve by m /m and
2 3
calculate this as a proportion of m . For example (Formula (3)):
Proportionretainedonthem63,,msieve= mm()63mm []()//mm (3)
23 1
Present the results as a Table showing, to two significant figures, the proportion by mass retained on each
sieve and the proportion passing the 2 mm sieve. The data shall also be used to construct a cumulative
distribution curve (see Figure 1).
9 Wet sieving and sedimentation (material <2 mm)
9.1 General
This clause specifies the procedure (see Figure 2) for the determination of the particle size distribution of
the material passing the 2 mm aperture sieve down to <0,002 mm equivalent spherical diameter (see note).
In order to ensure that primary particles, rather than loosely bonded aggregates, are measured, organic
matter and salts are removed, especially sparingly soluble salts such as gypsum which would otherwise
prevent dispersion and/or promote flocculation of the finer soil particles in suspension (see 9.6), and a
dispersing agent is added (9.3.2). These procedures are required in this document, and their omission shall
invalidate its application. Sometimes iron oxides and carbonates, especially of calcium and/or magnesium,
are also removed. Preferred procedures for the removal of these compounds are given in the note in 9.7. The
removal of any compound shall be recorded in the test report (see Clause 10).
NOTE 1 Gravitational sedimentation can give a value for the total amount of material <0,002 mm equivalent
spherical diameter. However, the method cannot be used to divide this class further with reliability, as particles less
than about 0,001 mm equivalent spherical diameter can be kept in suspension almost indefinitely by Brownian motion
(see Reference [2]).
9.2 Apparatus
The apparatus specified hereafter is sufficient to deal with one sample. Clearly it is more efficient to work in
batches. Experience has shown (see Reference [7]) that one operator can process up to 36 samples in a batch
at a time, given sufficient apparatus and space, especially if calculations are dealt with by a computer.
9.2.1 Sampling pipette or sampling needle, of a pattern similar to that shown in Figure 3 with sideways
openings, the chief requirement being that the smallest practicable horizontal zone of sedimenting
suspension shall be sampled. The pipette shall be of not less than 10 ml volume and shall be held in a frame
so that it can be lowered to a fixed depth within a sedimentation tube (see Figure 4).
NOTE 1 Experience suggests that a pipette with an upper volume of 50 ml is more than sufficient for most purposes.
A 25 ml volume pipette is a convenient compromise for routine analysis, but a smaller volume pipette will be found to
be sufficient for soils with down to about 10 % mass fraction of <0,063 mm equivalent spherical diameter. Below this
amount, greater precision is likely to be obtained with a pipette of larger volume.
NOTE 2 The position of the pipette is adjusted to the new suspension surface after each sampling.
NOTE 3 Automated systems can be used, if the results are proven to be equivalent.

Figure 1 — Particle-size-distribution chart

Figure 2 — Flow chart
Dimensions in millimetres
Key
1 bulb capacity: approximately 125 ml

2 pipette and changeover cock capacity at least 10 ml
3 sideways opening
NOTE This design has been found satisfactory, but alternative designs can be used.
Figure 3 — Sampling pipette for sedimentation test

Key
A and B 125 ml bulb funnel with stopcock H sedimentation tube
C safety-bulb suction inlet tube 1 scale graduated in millimetres
D safety bulb 2 clamps
E tap 3 sliding panel
F outlet tube 4 constant-temperature bath
G sampling pipette
a
D, F and G are joined to three-way stopcock E.
NOTE This design has been found satisfactory, but alternative designs can be used.
Figure 4 — Arrangement for lowering sampling pipette into soil suspension
9.2.2 Constant-temperature room or bath, which can be maintained at between 20 °C and (30 ± 1) °C.
If a bath is used, it shall accept a sedimentation tube immersed to the 500 ml or 1 000 ml mark and shall not
vibrate the contents of the tube. Similarly, if a room is used, it, and its furniture, shall be constructed so that
activity does not cause the tubes and their contents to vibrate.
NOTE This temperature range has been chosen to allow for the difficulties of maintaining one specified
temperature in different parts of the world. In addition, the lower temperature gives sedimentation times that fit well
into an average working day, whilst the upper temperature still allows for a sensible settling time for the fraction
0,063 mm equivalent spherical diameter (see Clause 4 and Table 3).
Table 3 — Pipette sampling times and d (for a particle density of 2,65 Mg/m ) at a sampling depth
p
from the surface of (100 ± 1) mm at different temperatures assuming a particle density of 2,65 Mg/
3 3
m and density of water with dispersant of 1,00 Mg/m
Times, after mixing, of starting sampling operation
st a nd rd th
T η 1 sample 2 sample 3 sample 4 sample
°C mPa/s min s min s min s h min s
15 1,139 1 4 5 17 53 11 8 47 45
16 1,109 1 2 5 8 51 47 8 33 51
17 1,081 1 1 5 1 50 29 8 20 53
18 1,053 0 59 4 53 49 10 8 7 54
19 1,027 0 58 4 46 47 57 7 55 52
20 1,002 0 56 4 38 46 46 7 44 5
21 0,978 0 55 4 32 45 39 7 32 55
22 0,955 0 53 4 25 44 34 7 22 16
23 0,933 0 52 4 19 43 33 7 12 4
24 0,911 0 51 4 13 42 32 7 1 58
25 0,891 0 50 4 8 41 35 6 52 37
26 0,871 0 49 4 2 40 39 6 43 21
27 0,851 0 48 3 56 39 43 6 34 5
28 0,833 0 47 3 51 38 53 6 25 44
29 0,815 0 46 3 46 38 2 6 17 24
30 0,798 0 45 3 42 37 14 6 9 31
31 1,781 0 44 3 37 36 27 6 1 39
32 0,764 0 43 3 33 35 42 5 54 11
33 0,749 0 42 3 28 34 58 5 46 57
34 0,734 0 41 3 24 34 16 5 39 58
35 0,719 0 40 3 20 33 35 5 33 12
d (mm) 0,063 0,02 0,006 3 0,002
p
Sampling depth (m) 0,2 0,2 0,1 0,1 0,1 0,1 0,1 0,1 0,1
a Sampling depth (200 ± 1) mm to allow adequate time for the stabilization of the suspension after mixing.

9.2.3 Glass sedimentation tubes, without pouring lips, of internal diameter approximately 50 - 60 mm,
and overall length of approximately 350 mm – 450 mm, graduated at 500 ml or 1 000 ml volume, and with
either rubber bungs to fit or a stirrer.
9.2.4 Stirrer, of non-corrodible material.
9.2.5 Weighing vessels, inert material, with masses known to the nearest 0,000 1 g.
9.2.6 Mechanical shaker, capable of keeping 30 g of soil in suspension in 150 ml of liquid.
NOTE For keeping the soil in suspension, a suitable device could be an end-to-end type of shaker (e.g. 10 to
30 revolutions/min) or a stirrer.
9.2.7 Test sieves, complying with ISO 565, ISO 3310-1 and ISO 3310-2, having apertures of 2 mm and
0,063 mm, plus two intermediate sieves. The test report shall state which apertures are used. Round-hole
sieves shall not be used.
NOTE The choice of the sieve of aperture 0,063 mm given here is for illustration but accords with the widespread
use of this particle size to define the upper boundary of the silt fraction. Local requirements can specify another
aperture. The choice of apertures for the intermediate sieves is a matter for local knowledge, but experience suggests
that sieves of aperture close to 0,2 mm and 0,1 mm are useful for a very wide range of soils.
9.2.8 Suitable sampledivider (see Clause 6).
9.2.9 Balance, capable of weighing to an accuracy of within ±0,000 1 g.
9.2.10 Drying oven, capable of maintaining a temperature between 105 °C and 110 °C.
9.2.11 Stop clock, readable to 1 s.
9.2.12 Desiccator, containing anhydrous silica gel (preferably of the self-indicating type), capable of
holding the five weighing vessels. The desiccant shall be inspected daily and dried at between 105 °C and
110 °C when it is no longer effective.
9.2.13 Glass beaker, of capacity 650 ml with a cover glass to fit, or a 300 to 500 ml centrifuge bottle with
a leak proof cap.
NOTE This apparatus is used for chemical pre-treatment during which a constant problem is the adhesion of very
fine particles to glass. The problem is much reduced if the treatment is carried out in a polycarbonate or polysulfone
centrifuge bottle. Both materials will withstand repeated heating to 120 °C and are resistant to hydrogen peroxide
and common dispersing agents. Their use can also save significant amounts of operator time.
9.2.14 Centrifuge, capable of holding the 300 to 500 ml centrifuge bottles (see 9.2.13).
9.2.15 Measuring cylinder, of capacity 1 000 ml.
9.2.16 Pipette, of capacity between 10 to 50 ml (25 ml recommended) (see 8.2.1).
9.2.17 Glass filter funnel, capable of holding the 0,063 mm sieve.
9.2.18 Wash bottle containing water (see 8.3).
9.2.19 Rod, of glass or strong plastic, 150 mm to 200 mm long and at least 4 mm in diameter, with a rubber
sleeve at one end.
9.2.20 Electric hotplate, capable of maintaining a temperature between 105 °C and 110 °C or Water bath,
capable of maintaining a temperature between 90 °C and 95 °C.
NOTE A hotplate is essential if polymer centrifuge bottles are used for the chemical pretreatment, but a Bunsen
burner, gauze and tripod are sufficient if glass beakers are used.
9.2.21 Suction device, similar to that shown in Figure 5 is useful, but not essential.
Key
1 flexible tube
2 pasteur pipette or similar
3 reservoir (5 l or 10 l)
a
To vacuum.
Figure 5 — Sketch of suction device
9.2.22 Sieve brush.
9.2.23 Electrical conductivity meter, accurate to 1 mS/m.
9.3 Reagents
All reagents shall be of recognized analytical grade. Use water having an electrical conductivity no greater
than 10 mS/m at 25 °C at the time of use.
9.3.1 Hydrogen peroxide solution, 30 % volume fraction.
NOTE A 30 % volume fraction solution is one which will yield 30 ml of gaseous oxygen from 100 ml of solution
(under standard conditions of temperature and pressure) upon reduction to water, either by chemical means or by
boiling.
9.3.2 Solution of a dispersing agent.
As a dispersing agent, dissolve 33 g of sodium hexametaphosphate and 7 g of anhydrous sodium carbonate
in water to make 1 l of solution. Store away from strong sunlight and preferably in a dark bottle. Record the
date of preparation on the bottle. The solution is unstable and shall be replaced after one month.
Another suitable dispersant is 0,1 M sodium pyrophosphate solution (tetrasodiumdiphosphate decahydrate
Na P O · 10 H O).
4 2 7 2
The sodium carbonate buffers the solution and the suspension of the soil, to about pH 9,8. The described
dispersing agents have been found successful with a very wide range of soils. However, if there are signs that
dispersion is ineffective, consider firstly that flocculating salts might be present (see 9.7). If dispersion is still
unsuccessful after removal of salts, then other dispersing agents should be considered. A very effective but
less widely used dispersing agent is prepared by replacing the sodium carbonate with 20 % volume fraction
ammonia solution, in the ratio of 5 ml ammonia solution to 150 ml of the hexametaphosphate solution. There
are many other dispersing agents (see Reference [3]). Whichever is chosen, considerable investigation will
be required to establish
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