Laboratory glassware -- Pyknometers

This International Standard specifies requirements for a series of pyknometers for general laboratory use for the
determination of the densities of liquids.
Specialized pyknometers for use with particular products, or otherwise not in common use, are excluded. Sufficient
details to define such pyknometers should be included in International Standards which specify or describe their
use.
A device suitable for adjustment of the liquid level in the neck of the Reischauer pyknometer is shown in annex A.

Verrerie de laboratoire -- Pycnomètres

Laboratorijska steklovina - Piknometri

General Information

Status
Published
Publication Date
31-May-2000
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
01-Jun-2000
Due Date
01-Jun-2000
Completion Date
01-Jun-2000

Relations

Effective Date
01-Jun-2000

Overview

ISO 3507:1999 specifies requirements for laboratory pyknometers (pycnometers) used to determine the densities of liquids. It defines a series of standard tube- and flask-type pyknometers for general laboratory use, excludes specialized devices for particular products, and gives construction, marking and measurement requirements to ensure reliable volume calibration and repeatable density determinations. Annex A illustrates an adjustment device for the Reischauer type.

Key topics and technical requirements

  • Types and sizes: Six types are specified (Lipkin, Sprengel, Gay‑Lussac, Reischauer, Hubbard and a ground‑in‑thermometer design) with a defined series of nominal capacities for each type.
  • Reference conditions: The standard reference temperature for capacity verification is 20 °C (27 °C recommended where tropical ambient conditions apply). Actual capacity must be stated with its verification temperature.
  • Material and construction: Pyknometers must be made of glass with suitable hydrolytic resistance (at least HGB3) and appropriate thermal stability (includes borosilicate glass 3.3). Stoppers, caps and taps must have compatible thermal properties. Shapes, neck design and stopper fit are specified to avoid trapped liquid and ensure repeatable filling.
  • Capacity, tolerances and calibration: The standard defines actual capacity (volume of water at the reference temperature) and nominal capacity, and sets maximum permissible differences and measurement‑uncertainty requirements (capacity must be determined at the 95% confidence level).
  • Graduation and markings: Graduation lines must be clean, permanent and ≤ 0.3 mm thick, with defined layouts for each type. Permanent markings required include nominal capacity (or determined capacity to 0.001 ml plus verification temperature), unit of volume, manufacturer, and identification marks to ensure correct stopper/thermometer positioning.
  • Thermometers and accessories: For the ground‑in‑thermometer pyknometer the standard calls for enclosed‑scale thermometers meeting ISO 386 and for a capillary side tube/cap design where applicable.

Applications and users

  • Primary use: Accurate determination of liquid density and specific gravity in analytical and quality control laboratories.
  • Who uses it: Laboratory managers, analytical chemists, calibration laboratories, glassware manufacturers, and instrument suppliers who produce or verify pyknometers and related volumetric apparatus.
  • Practical benefits: Ensures interchangeability, traceable volume calibration, reproducible density measurements, and conformity across labs and suppliers.

Related standards

  • ISO 383 - Interchangeable conical ground joints
  • ISO 384 - Principles for volumetric glassware
  • ISO 386 - Liquid‑in‑glass thermometers
  • ISO 719 - Hydrolytic resistance of glass
  • ISO 3585 - Borosilicate glass 3.3

Keywords: ISO 3507, pyknometer, pycnometer, laboratory glassware, density determination, volumetric calibration, borosilicate glass, ISO standard.

Standard

ISO 3507:1999 - Laboratory glassware -- Pyknometers

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Frequently Asked Questions

SIST ISO 3507:2000 is a standard published by the Slovenian Institute for Standardization (SIST). Its full title is "Laboratory glassware -- Pyknometers". This standard covers: This International Standard specifies requirements for a series of pyknometers for general laboratory use for the determination of the densities of liquids. Specialized pyknometers for use with particular products, or otherwise not in common use, are excluded. Sufficient details to define such pyknometers should be included in International Standards which specify or describe their use. A device suitable for adjustment of the liquid level in the neck of the Reischauer pyknometer is shown in annex A.

This International Standard specifies requirements for a series of pyknometers for general laboratory use for the determination of the densities of liquids. Specialized pyknometers for use with particular products, or otherwise not in common use, are excluded. Sufficient details to define such pyknometers should be included in International Standards which specify or describe their use. A device suitable for adjustment of the liquid level in the neck of the Reischauer pyknometer is shown in annex A.

SIST ISO 3507:2000 is classified under the following ICS (International Classification for Standards) categories: 17.060 - Measurement of volume, mass, density, viscosity; 71.040.20 - Laboratory ware and related apparatus. The ICS classification helps identify the subject area and facilitates finding related standards.

SIST ISO 3507:2000 has the following relationships with other standards: It is inter standard links to SIST ISO 3507:1995. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.

You can purchase SIST ISO 3507:2000 directly from iTeh Standards. The document is available in PDF format and is delivered instantly after payment. Add the standard to your cart and complete the secure checkout process. iTeh Standards is an authorized distributor of SIST standards.

Standards Content (Sample)


SLOVENSKI STANDARD
01-junij-2000
1DGRPHãþD
SIST ISO 3507:1995
Laboratorijska steklovina - Piknometri
Laboratory glassware -- Pyknometers
Verrerie de laboratoire -- Pycnomètres
Ta slovenski standard je istoveten z: ISO 3507:1999
ICS:
17.060 Merjenje prostornine, mase, Measurement of volume,
gostote, viskoznosti mass, density, viscosity
71.040.20 Laboratorijska posoda in Laboratory ware and related
aparati apparatus
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

INTERNATIONAL ISO
STANDARD 3507
Second edition
1999-04-15
Laboratory glassware — Pyknometers
Verrerie de laboratoire — Pycnomètres
A
Reference number
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 3.
International Standard ISO 3507 was prepared by Technical Committee ISO/TC 48, Laboratory glassware and
related apparatus, Subcommittee SC 4, Density measuring instruments.
This second edition cancels and replaces the first edition (ISO 3507:1976) by incorporating the following changes:
a) the title has been modified;
b) Gay-Lussac pyknometers of 1 ml, 2 ml, 5 ml and 100 ml have been added;
c) Reischauer pyknometers of 10 ml and 100 ml have been added;
d) a Hubbard pyknometer of 50 ml has been added;
e) pyknometers with ground-in thermometer and capillary side tube have been added.
.
©  ISO 1999
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 • CH-1211 Genève 20 • Switzerland
Internet iso@iso.ch
Printed in Switzerland
ii
INTERNATIONAL STANDARD  © ISO ISO 3507:1999(E)
Laboratory glassware — Pyknometers
1 Scope
This International Standard specifies requirements for a series of pyknometers for general laboratory use for the
determination of the densities of liquids.
Specialized pyknometers for use with particular products, or otherwise not in common use, are excluded. Sufficient
details to define such pyknometers should be included in International Standards which specify or describe their
use.
A device suitable for adjustment of the liquid level in the neck of the Reischauer pyknometer is shown in annex A.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this International Standard. For dated references, subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements based on this International Standard are encouraged to
investigate the possibility of applying the most recent editions of the normative documents indicated below. For
undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC
maintain registers of currently valid International Standards.
ISO 383, Laboratory glassware — Interchangeable conical ground joints.
ISO 384:1978, Laboratory glassware — Principles of design and construction of volumetric glassware.
ISO 386, Liquid-in-glass laboratory thermometers — Principles of design, construction and use.
ISO 719, ° .
Glass — Hydrolytic resistance of glass grains at 98 C — Method of test and classification
ISO 3585, Borosilicate glass 3.3 — Properties.
3 Basis of adjustment
3.1 Unit of volume
The unit of volume shall be the millilitre (ml), which is equivalent to the cubic centimetre (cm ).
NOTE The term millilitre (ml) is commonly used as a special name for the cubic centimetre (cm ), in accordance with a
decision of the Twelfth Conférence Générale des Poids et Mesures. The term millilitre is acceptable, in general, for references
in International Standards to capacities of volumetric glassware and it is used in this International Standard.
© ISO
3.2 Reference temperature
If the actual capacity is marked on a pyknometer, the verification temperature at which this actual capacity is
determined shall also be marked. Under normal circumstances the standard reference temperature shall be 20 °C.
When it is necessary in tropical countries to work at an ambient temperature considerably above 20 °C, and these
countries do not wish to use the standard reference temperature of 20 °C, a temperature of 27 °C is recommended.
4 Types and series of sizes
Two types of pyknometer tube and four types of pyknometer flask are specified, as listed in Table 1 and illustrated
in Figures 1 to 6. Types 1 and 2, of tubular form, are for suspension; types 3, 4, 5 and 6, of flask form, are free-
standing on flat bases.
Types 1, 3 and 4, and type 2 if provided with caps, shall be used for volatile liquids. Type 5 shall be used for very
viscous materials.
The series of sizes for each type of pyknometer shall be as shown in Table 1.
Table 1 — Types and sizes of pyknometers
Type Designation Nominal capacities
ml
1  Lipkin 1  2  5  10
2  Sprengel 5  10  25
3  Gay-Lussac 1  2  5  10  25  50  100
4  Reischauer 10  25  50  100
5  Hubbard 25  50
6  Ground-in thermometer 10  25  50  100
5 Capacities of pyknometers
5.1 Actual capacity
The actual capacity is the volume, in millilitres, of water at the reference temperature contained by the pyknometer,
which is also at that temperature. The volume, according to type, is defined as follows.
 Type 1: Between zero lines of the two scales;
 Type 2: From tip of jet to graduation line;
 Type 3 and 5: To top of bore of stopper;
 Type 4: To zero line of scale;
 Type 6: To top of capillary side tube.
The recommended reference temperature is 20 °C but other appropriate temperatures may be selected in
accordance with 3.2.
© ISO
5.2 Nominal capacity
The nominal capacity is the actual capacity rounded to the nearest appropriate value given in Table 1.
6 Difference between actual capacity, nominal capacity and accuracy
The difference between the actual capacity and the nominal capacity of a pyknometer shall not exceed the
appropriate maximum value shown in Table 2, 3 or 4.
The actual capacity of a pyknometer shall be determined at the 95 % confidence level (k = 2) with an uncertainty of
measurement which does not exceed the following values:
Type 1 Lipkin ± 5 ml
Type 2 Sprengel ± 5 ml
Type 3 Gay-Lussac ± 10 ml
Type 4 Reischauer ± 5 ml
Type 5 Hubbard ± 50 ml
Type 6 Ground-in thermometer ± 15 ml
7 Construction
7.1 Material
Pyknometers shall be made from glass of hydrolytic class not lower than HGB3 according to ISO 719, with a
–6 –1
coefficient of thermal expansion not exceeding 3,3 ´ 10 °C .
NOTE This includes borosilicate glass 3.3 according to ISO 3585.
Pyknometers shall be as free as possible from visible defects and reasonably free from internal strain. Stoppers or
taps shall be made from glass having similar thermal properties to that used for the pyknometers to which they are
fitted.
7.2 Mass
The mass of a pyknometer shall not exceed the appropriate maximum value shown in Tables 2, 3 and 4.
7.3 Dimensions
Pyknometers shall comply with the appropriate toleranced dimensional requirements shown in Tables 2, 3 and 4.
The additional dimensions which are specified by nominal values without tolerances are for the guidance of
manufacturers.
7.4 Shape
7.4.1  The shapes of the six types of pyknometer shall be generally as shown in Figures 1 to 6 and shall comply
with the detailed requirements given in 7.4.2 to 7.4.8.
All tapered portions of pyknometers shall be smoothly formed so as to avoid sharp shoulders which could entrap air
bubbles.
© ISO
7.4.2  Pyknometers of type 1 shall have an oval bulb, as illustrated in Figure 1, which merges gradually into the
tubes at each end.
The left arm of the pyknometer shall be bent as shown in Figure 1, the distance from the end to the outside of the
bend being (20 – 2) mm and the included angle being 50° to 55°.
The two ends of the pyknometer shall be finished square with the axis of the tubes and smoothly fire-polished
without constriction.
7.4.3  Pyknometers of type 2 shall have a cylindrical bulb with tapered ends which merge gradually into the
adjoining tubes.
The two arms shall be bent at an angle of approximately 75° to the vertical and shall lie in the same plane as the
U-portion of the pyknometer. One arm shall be drawn down to a smooth tapered jet, the end of which shall have a
bore of approximately 0,5 mm and shall be ground smooth at right angles to the axis of the tube and slightly
bevelled on the outside.
The end of the other arm of the pyknometer shall be finished square with the axis of the tube and smoothly
firepolished without constriction.
7.4.4  Pyknometers of type 2 that are fitted with ground-on caps at the ends of the side arms shall comply with the
following additional requirements.
a) The ground zones of the joints shall be such that the two caps are interchangeable, and the joints comply with
the requirements for size 5/9 of ISO 383.
b) The cones of the joints shall be formed with a minimum distortion of the bore of the tube, and such distortion
shall be smoothly tapered. The tip of the jet shall project beyond the small end of the ground zone and
c) The caps shall be smoothly ground to a good fit on the cones and shall be of sufficient size to clear the tip of
the jet.
7.4.5  Pyknometers of types 3, 4, 5 and 6 shall stand vertically without rocking or spinning when placed on a level
surface. They shall not topple when placed empty, with the stopper inserted, on a surface inclined at an angle of 15°
to the horizontal.
7.4.6  Pyknometers of types 3, 4 and 6 shall have a body shape similar to that shown in Figures 3, 4 and 6, in
which the plane of maximum diameter is at approximately one-third of the distance from the base to the bottom of
the neck.
7.4.7  Pyknometers of type 5 shall have a body shape as shown in Figure 5, in which the upper end of the conical
portion merges smoothly with the neck without a sharp shoulder. The radius of curvature between the lower end of
the conical portion and the base shall not be less than 5 mm.
7.4.8  Pyknometers of type 6 shall have a capillary side tube smoothly fitted to the body at an angle of
approximately 90°. The upper part of the capillary side tube shall be positioned parallel to the vertical axis of the
pyknometer body. The outer diameter of the capillary side tube shall be approximately 6 mm and the upper end
shall be ground to a flat surface of approximately 6 mm.
7.5 Necks
7.5.1  For types 3 and 5, the top of the neck of the flask shall be reconstructed so that there is no channel in which
liquid can lodge between the stopper and the neck of the bottle. The outer edge of the top of the neck shall be
slightly bevelled.
The ground zone of the neck shall extend below the bottom of the stopper when the latter is in position and there
shall be no ridge at the lower end of the grinding.
NOTE This can be a manufactured tool process or a grinding process.
© ISO
7.5.2  For type 4, the portion of the neck bearing the graduated scale shall be cyl
...


INTERNATIONAL ISO
STANDARD 3507
Second edition
1999-04-15
Laboratory glassware — Pyknometers
Verrerie de laboratoire — Pycnomètres
A
Reference number
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 3.
International Standard ISO 3507 was prepared by Technical Committee ISO/TC 48, Laboratory glassware and
related apparatus, Subcommittee SC 4, Density measuring instruments.
This second edition cancels and replaces the first edition (ISO 3507:1976) by incorporating the following changes:
a) the title has been modified;
b) Gay-Lussac pyknometers of 1 ml, 2 ml, 5 ml and 100 ml have been added;
c) Reischauer pyknometers of 10 ml and 100 ml have been added;
d) a Hubbard pyknometer of 50 ml has been added;
e) pyknometers with ground-in thermometer and capillary side tube have been added.
.
©  ISO 1999
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 • CH-1211 Genève 20 • Switzerland
Internet iso@iso.ch
Printed in Switzerland
ii
INTERNATIONAL STANDARD  © ISO ISO 3507:1999(E)
Laboratory glassware — Pyknometers
1 Scope
This International Standard specifies requirements for a series of pyknometers for general laboratory use for the
determination of the densities of liquids.
Specialized pyknometers for use with particular products, or otherwise not in common use, are excluded. Sufficient
details to define such pyknometers should be included in International Standards which specify or describe their
use.
A device suitable for adjustment of the liquid level in the neck of the Reischauer pyknometer is shown in annex A.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this International Standard. For dated references, subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements based on this International Standard are encouraged to
investigate the possibility of applying the most recent editions of the normative documents indicated below. For
undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC
maintain registers of currently valid International Standards.
ISO 383, Laboratory glassware — Interchangeable conical ground joints.
ISO 384:1978, Laboratory glassware — Principles of design and construction of volumetric glassware.
ISO 386, Liquid-in-glass laboratory thermometers — Principles of design, construction and use.
ISO 719, ° .
Glass — Hydrolytic resistance of glass grains at 98 C — Method of test and classification
ISO 3585, Borosilicate glass 3.3 — Properties.
3 Basis of adjustment
3.1 Unit of volume
The unit of volume shall be the millilitre (ml), which is equivalent to the cubic centimetre (cm ).
NOTE The term millilitre (ml) is commonly used as a special name for the cubic centimetre (cm ), in accordance with a
decision of the Twelfth Conférence Générale des Poids et Mesures. The term millilitre is acceptable, in general, for references
in International Standards to capacities of volumetric glassware and it is used in this International Standard.
© ISO
3.2 Reference temperature
If the actual capacity is marked on a pyknometer, the verification temperature at which this actual capacity is
determined shall also be marked. Under normal circumstances the standard reference temperature shall be 20 °C.
When it is necessary in tropical countries to work at an ambient temperature considerably above 20 °C, and these
countries do not wish to use the standard reference temperature of 20 °C, a temperature of 27 °C is recommended.
4 Types and series of sizes
Two types of pyknometer tube and four types of pyknometer flask are specified, as listed in Table 1 and illustrated
in Figures 1 to 6. Types 1 and 2, of tubular form, are for suspension; types 3, 4, 5 and 6, of flask form, are free-
standing on flat bases.
Types 1, 3 and 4, and type 2 if provided with caps, shall be used for volatile liquids. Type 5 shall be used for very
viscous materials.
The series of sizes for each type of pyknometer shall be as shown in Table 1.
Table 1 — Types and sizes of pyknometers
Type Designation Nominal capacities
ml
1  Lipkin 1  2  5  10
2  Sprengel 5  10  25
3  Gay-Lussac 1  2  5  10  25  50  100
4  Reischauer 10  25  50  100
5  Hubbard 25  50
6  Ground-in thermometer 10  25  50  100
5 Capacities of pyknometers
5.1 Actual capacity
The actual capacity is the volume, in millilitres, of water at the reference temperature contained by the pyknometer,
which is also at that temperature. The volume, according to type, is defined as follows.
 Type 1: Between zero lines of the two scales;
 Type 2: From tip of jet to graduation line;
 Type 3 and 5: To top of bore of stopper;
 Type 4: To zero line of scale;
 Type 6: To top of capillary side tube.
The recommended reference temperature is 20 °C but other appropriate temperatures may be selected in
accordance with 3.2.
© ISO
5.2 Nominal capacity
The nominal capacity is the actual capacity rounded to the nearest appropriate value given in Table 1.
6 Difference between actual capacity, nominal capacity and accuracy
The difference between the actual capacity and the nominal capacity of a pyknometer shall not exceed the
appropriate maximum value shown in Table 2, 3 or 4.
The actual capacity of a pyknometer shall be determined at the 95 % confidence level (k = 2) with an uncertainty of
measurement which does not exceed the following values:
Type 1 Lipkin ± 5 ml
Type 2 Sprengel ± 5 ml
Type 3 Gay-Lussac ± 10 ml
Type 4 Reischauer ± 5 ml
Type 5 Hubbard ± 50 ml
Type 6 Ground-in thermometer ± 15 ml
7 Construction
7.1 Material
Pyknometers shall be made from glass of hydrolytic class not lower than HGB3 according to ISO 719, with a
–6 –1
coefficient of thermal expansion not exceeding 3,3 ´ 10 °C .
NOTE This includes borosilicate glass 3.3 according to ISO 3585.
Pyknometers shall be as free as possible from visible defects and reasonably free from internal strain. Stoppers or
taps shall be made from glass having similar thermal properties to that used for the pyknometers to which they are
fitted.
7.2 Mass
The mass of a pyknometer shall not exceed the appropriate maximum value shown in Tables 2, 3 and 4.
7.3 Dimensions
Pyknometers shall comply with the appropriate toleranced dimensional requirements shown in Tables 2, 3 and 4.
The additional dimensions which are specified by nominal values without tolerances are for the guidance of
manufacturers.
7.4 Shape
7.4.1  The shapes of the six types of pyknometer shall be generally as shown in Figures 1 to 6 and shall comply
with the detailed requirements given in 7.4.2 to 7.4.8.
All tapered portions of pyknometers shall be smoothly formed so as to avoid sharp shoulders which could entrap air
bubbles.
© ISO
7.4.2  Pyknometers of type 1 shall have an oval bulb, as illustrated in Figure 1, which merges gradually into the
tubes at each end.
The left arm of the pyknometer shall be bent as shown in Figure 1, the distance from the end to the outside of the
bend being (20 – 2) mm and the included angle being 50° to 55°.
The two ends of the pyknometer shall be finished square with the axis of the tubes and smoothly fire-polished
without constriction.
7.4.3  Pyknometers of type 2 shall have a cylindrical bulb with tapered ends which merge gradually into the
adjoining tubes.
The two arms shall be bent at an angle of approximately 75° to the vertical and shall lie in the same plane as the
U-portion of the pyknometer. One arm shall be drawn down to a smooth tapered jet, the end of which shall have a
bore of approximately 0,5 mm and shall be ground smooth at right angles to the axis of the tube and slightly
bevelled on the outside.
The end of the other arm of the pyknometer shall be finished square with the axis of the tube and smoothly
firepolished without constriction.
7.4.4  Pyknometers of type 2 that are fitted with ground-on caps at the ends of the side arms shall comply with the
following additional requirements.
a) The ground zones of the joints shall be such that the two caps are interchangeable, and the joints comply with
the requirements for size 5/9 of ISO 383.
b) The cones of the joints shall be formed with a minimum distortion of the bore of the tube, and such distortion
shall be smoothly tapered. The tip of the jet shall project beyond the small end of the ground zone and
c) The caps shall be smoothly ground to a good fit on the cones and shall be of sufficient size to clear the tip of
the jet.
7.4.5  Pyknometers of types 3, 4, 5 and 6 shall stand vertically without rocking or spinning when placed on a level
surface. They shall not topple when placed empty, with the stopper inserted, on a surface inclined at an angle of 15°
to the horizontal.
7.4.6  Pyknometers of types 3, 4 and 6 shall have a body shape similar to that shown in Figures 3, 4 and 6, in
which the plane of maximum diameter is at approximately one-third of the distance from the base to the bottom of
the neck.
7.4.7  Pyknometers of type 5 shall have a body shape as shown in Figure 5, in which the upper end of the conical
portion merges smoothly with the neck without a sharp shoulder. The radius of curvature between the lower end of
the conical portion and the base shall not be less than 5 mm.
7.4.8  Pyknometers of type 6 shall have a capillary side tube smoothly fitted to the body at an angle of
approximately 90°. The upper part of the capillary side tube shall be positioned parallel to the vertical axis of the
pyknometer body. The outer diameter of the capillary side tube shall be approximately 6 mm and the upper end
shall be ground to a flat surface of approximately 6 mm.
7.5 Necks
7.5.1  For types 3 and 5, the top of the neck of the flask shall be reconstructed so that there is no channel in which
liquid can lodge between the stopper and the neck of the bottle. The outer edge of the top of the neck shall be
slightly bevelled.
The ground zone of the neck shall extend below the bottom of the stopper when the latter is in position and there
shall be no ridge at the lower end of the grinding.
NOTE This can be a manufactured tool process or a grinding process.
© ISO
7.5.2  For type 4, the portion of the neck bearing the graduated scale shall be cylindrical and the internal diameter
shall be uniform over the entire scale length. The internal diameter of the neck above this portion shall not be
constricted. The upper end of the neck shall be ground either as a socket with a strengthening bead above as
shown in Figure 4, or as a cone. In either case the grinding shall comply with the requirements of ISO 383, for the
joint sizes liste
...

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