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UDC 542.23
IS0
ORGAN I Z AT I O N FOR STAND A RD I ZATl O N
1 N T ERN AT1 O N A L
IS0 RECOMMENDATION
R 385
BURETTES
1st EDITION
September 1964
COPYRIGHT RESERVED
The copyright of IS0 Recommendations and IS0 Standards
belongs to IS0 Member Bodies. Reproduction of these
documents, in any country, may be authorized therefore only
by the national standards organization of that country, being
a member of ISO.
For each individual country the only valid standard is the national standard of that country.
hinted in Switzerland
Also issued in French and Russian. Copies to be obtained through the national standards organizations.
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BRIEF HISTORY
The IS0 Recommendation R 385, Burettes, was drawn up by Technical Committee
ISO/TC 48, Laboratory Glassware and Related Apparatus, the Secretariat of which is held by
the British Standards Institution (BSI).
Work on this question by the Technical Committee began in 1952 and led, in 1960, to
the adoption of a Draft IS0 Recommendation.
In April 1960, this Draft IS0 Recommendation (No. 348) was circulated to all the IS0
Member Bodies for enquiry. It was approved, subject to a few modifications of an editorial
nature, by the following Member Bodies :
Greece Romania
Australia
Austria India Spain
Belgium Israel Sweden
Italy United Kingdom
Canada
Japan U.S.A.
Chile
Netherlands U.S.S.R.
Colombia
New Zealand
France
Germany Poland
One Member Body opposed the approval of the Draft:
Czechoslovakia.
The Draft IS0 Recommendation was then submitted by correspondence to the IS0 Coun-
cil, which decided, in September 1964, to accept it as an IS0 RECOMMENDATION.
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lSO/R 385 - 1964 (E)
IS0 Recommendation R 385 September 1964
BURETTES
1. SCOPE
This IS0 Recommendation is intended to provide details of an internationally acceptable range
of burettes, adequate for general laboratory purposes.
The details specified are in conformity with IS0 Recommendation R 384, Principles of Construction
and Adjustment of' Volumetric Glassware.
2. BASIS OF ADJUSTMENT
2.1 Unit of volumci
The unit of volume should be the cubic centimetre (cm3), for which the name millilitre (mi)
may be used,
NOTE. - The term millilitre (nil) is commonly used as a special naine for the cubic Centimetre (cm3), in
accordance with a decision of the Twelfth Conférence Générale des Poids et Mesures. The term millilitre is
acceptable, in general, for references in IS0 Recommendations to capacities of volumetric glassware and
it is used, in particular, in the present text.
2.2 Reference temperature
The standard reference temperature, i.e. the temperature at which the burette is intended
to deliver its nominal volume (nominal capacity), should be 20 OC.
NOTE. -- 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, it is recornmended
that they should adopt a temperature of 27 "C.
3. CLASSES OF ACCURACY
Two classes of accuracy should be specified:
Class A for the higher grade,
Class B for the lower grade,
in such a way that in neither class does the permissible tolerance exceed the smallest scale division.
4. SERIES OF CAPACITIES
The series of capacities of burettes should be as shown in Table 1.
NOTE. - If other capacities of burettes are required than those listed in Table 1, it is recoininended that they
should conform, as far as possible, to the essential requirements of this IS0 Recommendation.
TABLE 1. - Range of capacities, divisions and tolerances
Smallest scale ~
Capacity division i Tolerance
Class of
ml
1
10 A 0.05 ~ j, 0.02
10 B 0.05 & 0.05
0.05 j, 0.03
25 A
B 0.05 -I 0.05
25
B o. 1 zt 0.1
I
A o. 1 I rt 0.05
B o. 1 1 Zk 0.1
A 0.2 i 0.1
B 0.2 i 0.2
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ISO/R 385 - 1961 (E)
5. DEFINITION OF CAPACITY
The capacity corresponding to any graduation line should be defined as the volume of water at
20 "C expressed in millilitres, delivered by the burette at 20 "C when emptied from the zero line
to that graduation line, outflow being unrestricted until making the final setting of the meniscus
on the graduation line, and no period being allowed for drainage of liquid adhering to the wall
before making the final setting.
NOTE. - Where, exceptionally, the standard reference temperature is 27 "C, this value should be substituted
for 20 "C.
Setting of the meniscus should be performed by one of the two methods detailed below. In
order to minimize possible errors, the same method of setting should be used for both zero and
end readings.
(a) The meniscus is set so that the plane of the upper edge of the graduation line is horizon-
tally tangential to the lowest point of the meniscus, the line of sight being in the same plane.
(6) The meniscus is set so that the plane of the centre of the graduation line is horizontally
tangential to the lowest point of the meniscus. The eye is raised towards the plane and
observes the front and back portions of the line apparently meeting the lowest point siinul-
taneously.
The burette should be filled to a few millimetres above the zero line and the falling meniscus
should be set to the line. Any drop adhering to the jet should be removed by bringing a glass
vessel into contact with the tip of the jet. Delivery should then be made into another glass
vessel with the jet not in contact with the side. After adjustment of the meniscus to the desired
graduation line, the drop of water adhering to the jet should be added to the delivered volume
by bringing the inside of the receiving vessel into contact with the tip of the jet.
6. TOLERANCES ON CAPACITY
Tolerances on capacity of burettes should not exceed the values shown in Table 1, page 5.
The tolerance represents the maximum permissible error at any point and also the maximum
permissible difference between the errors at any two points.
7. CONSTRUCTION
7.1 Material
Burettes should be constructed of glass of suitable chemical and thermal properties, should
be as free as possible from visible defects and should be reasonably free from internal
strain.
7.2 Dimensions
Burettes should comply with the dimensional requirements shown in Table 2, page 7.
7.3 Stopcocks
7.3.1 Stopcocks should be ground to permit easy turning and to prevent a rate of leakage
greater than that specified in clause 7.3.3. Grinding to a taper of 1/10 is preferred.
Suitable devices for retaining the stopcock key should be permitted when required.
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ISO/R 385 - 1964 (E)
TABLE 2. - Dimensions
Scale length
~- ~ ~~~ Overall length
Smallest scale
Capacity
division maximum
Class of minimum maximum
accuracy
~~
ml ni 1 cm cni cm
10 A and B 0.05 25 35 57
25 A and B 0.05 50 I 60 82
25 B o. 1 30 40 62
50 A and B o. 1 50 60 82
100 A and B 0.2 55 65 87
Distance of zero line from top of burette . . . . . . . . . . minimum 5 cm
'3
Distance of lowest graduation line from top of stopcock . . . . 5 cm
9,
Length of tube of uniform bore below lowest graduation line . , 2 cm
9,
Distance of end of jet from underside of stopcock . . . . . . 5 cm
7.3.2 Stopcocks should be either single bore or double oblique bore, the diameter of the bore
being approximately 2 mm in either case. Stopcock dimensions should comply with
the appropriate national or international specification.
7.3.3 Stopcocks should be tested for leakage with the burette clamped in a vertical position,
the stopcock free from grease, the barrel and key wetted with water and the burette
filled initially to the zero line with water. The rate of leakage with the key in either of
the fully shut-off positions should not exceed the smallest scale division in 10 minutes.
Double bore stopcocks, in addition to passing this test, should not show a rate of leakage
greater than that specified above when tested similarly, with the burette empty, the key
of the stopcock in the normal delivery position and the filling tube connected to a
suitable graduated tube filled with water to a level 25 cm above the zero line of the
burette.
In order to ensure a sufficiently accurate determination, the leakage test should be carried
out for a period of at least 30 minutes.
Under conditions of high temperature and low humidity, it may be desirable to have a
loose cap over the top of the burette during the test, to minimize evaporation.
NOTE. - The leakage test described above is suitable for purposes of adjustment. For many other
purposes, a quicker test may be
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