ASTM E542-01(2007)
(Practice)Standard Practice for Calibration of Laboratory Volumetric Apparatus
Standard Practice for Calibration of Laboratory Volumetric Apparatus
SCOPE
1.1 This practice covers procedures for use in the calibration of volumetric ware, in accordance with Specification E694 such as is in common use in chemical and clinical laboratories. It is based on the gravimetric determination of the quantity of water either contained or delivered, and the conversion of this value to true volume at the standard temperature of 20C by means of suitable equations and standard tables. Calibration using mercury is excluded. Calibration may be performed using alternative gravimetric methodology, provided that it is demonstrated and documented that the results obtained are equivalent to those obtained using the methodology described herein.
1.2 This practice is intended to encompass capacity ware between the limits of 0.1 cm3 and 2000 cm3. Typical products falling within the purview of this practice are burets graduated" to deliver", graduated cylinders, volumetric flasks, specific gravity flasks, measuring and dilution pipets, and transfer and capacity pipets.
1.3 The procedures are not recommended for calibration of apparatus with capacities below 0.1 cm3, such as microglassware.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: E542 − 01 (Reapproved2007)
Standard Practice for
Calibration of Laboratory Volumetric Apparatus
This standard is issued under the fixed designation E542; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope 3. Summary of Practice
1.1 Thispracticecoversproceduresforuseinthecalibration 3.1 This practice is based upon a determination of the
of volumetric ware, in accordance with Specification E694 volume of water either contained in or delivered by the vessel.
suchasisincommonuseinchemicalandclinicallaboratories. Procedures are given for cleaning, setting the meniscus,
It is based on the gravimetric determination of the quantity of manipulating the apparatus, weighing, and converting the
water either contained or delivered, and the conversion of this weight to the appropriate standard volume.
value to true volume at the standard temperature of 20°C by
means of suitable equations and standard tables. Calibration 4. Significance and Use
using mercury is excluded. Calibration may be performed
4.1 The primary purpose of this practice is to provide
using alternative gravimetric methodology, provided that it is
uniform procedures that may be used to accurately calibrate a
demonstrated and documented that the results obtained are
wide variety of volumetric ware. The techniques are simple in
equivalent to those obtained using the methodology described
concept and can provide reliable results, provided the proce-
herein.
dures are followed faithfully.Accordingly, the practice should
1.2 This practice is intended to encompass capacity ware provide a means for checking the original calibration of
3 3
glassware and similar apparatus and for periodic rechecks as
between the limits of 0.1 cm and 2000 cm . Typical products
fallingwithinthepurviewofthispracticeareburetsgraduated“ the need should arise.
to deliver”, graduated cylinders, volumetric flasks, specific
4.2 Borosilicate volumetric glassware will hold its calibra-
gravity flasks, measuring and dilution pipets, and transfer and
tion indefinitely provided that it is not exposed to hydrofluoric
capacity pipets.
acid, hot phosphoric acid, or strong, hot alkalis, and that it is
1.3 The procedures are not recommended for calibration of not heated above 150°C when dry. A frosting of the glass
apparatus with capacities below 0.1 cm , such as microglass- surface (viewed when dry) indicates that chemical attack has
ware. occured, and recalibration may be in order. As a precaution,
however, it is recommended that the glassware be recalibrated
1.4 This standard does not purport to address all of the
after ten years of service regardless of its appearance.
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appro-
4.3 Soda-lime volumetric glassware will become frosted
priate safety and health practices and determine the applica- withtimebecauseofattackfrommoistureintheatmosphereas
bility of regulatory limitations prior to use.
well as from the chemicals mentioned above. In addition, it
shouldnotbeheatedabove90°Cwhendry.Itisrecommended,
2. Referenced Documents
therefore, that it be recalibrated after five years of service
unless frosting (viewed when dry) is observed sooner.
2.1 ASTM Standards:
E694Specification for Laboratory Glass Volumetric Appa-
5. Units of Measurement
ratus
5.1 Capacity—The basic SI unit for volume is the cubic
metre, m . Due to its large size, it is rarely used in volumetric
calibration. Rather, the cubic centimetre, cm , is used and will
This practice is under the jurisdiction ofASTM Committee E41 on Laboratory
Apparatus and is the direct responsibility of Subcommittee E41.01 on Apparatus.
be employed in this practice. The unit, millilitre, mL, may be
Current edition approved Nov. 1, 2007. Published December 2007. Originally
considered as equivalent to the cubic centimetre.
approved in 1979. Last previous edition approved in 2001 as E542–01. DOI:
10.1520/E0542-01R07.
5.2 Standard Temperature—Volumetric ware is almost uni-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
versally calibrated at 20°C. The procedures described provide
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
for such a calibration. When it is necessary to work at higher
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. ambient temperatures, such as is the case in tropical countries,
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E542 − 01 (2007)
calibration may be required at the International Standards a film of solution will cover the entire interior surface.Abreak
Organization (ISO) recommended temperature of 27°C. Equa- in the film indicates a contaminated area. For filling a buret
tions are given to correct the calibrated volume to other with cleaning solution, it should be held in a vertical position
temperatures as this may be required or desired. and filled by pouring into the top. Open the stopcock to drain.
Regardless of the type of vessel, always rinse thoroughly, first
6. Apparatus
with tap water and then with distilled water. Plastic volumetric
ware should be cleaned in an appropriate manner before
6.1 Balance, having sufficient capacity to weigh the loaded
calibration.
vessel. The sensitivity of the balance will be a limiting factor
in the accuracy of the measurements. Either a single-pan,
7.3 Reading and Setting a Liquid Meniscus:
direct-reading balance or an equal-arm balance of adequate
7.3.1 Reading the Meniscus—Forallapparatuscalibratedby
sensitivityandcapacitymaybeused.Ineithercasetheweights
this procedure, the reading is made on the lowest point of the
must be calibrated with adequate accuracy. Ordinarily, weights
meniscus. In order that the lowest point may be observed, it is
with NBS Class S-1 tolerances are required. The balance must
necessary to place a shade of some dark material immediately
have physical dimensions to accept the size of the vessels
below and behind the meniscus, which renders the profile of
which need to be weighed.
the meniscus dark and clearly visible against a light back-
ground.Aconvenientdeviceforthispurposeisacollar-shaped
6.2 Thermometer, for measuring the temperature of the
section of thick black rubber tubing, cut open at one side and
water. The accuracy of this calibration will depend upon the
of such size as to clasp the tube firmly. Alternatively, black
accuracyrequirementofthevolumetriccalibration(seeSection
paper may be used. “Short line” graduated vessels where the
14 for tolerances).
lines are less than one half of the circumference may be read
6.3 Barometer, capable of providing atmospheric pressure
more accurately by placing a mirror against the rear of the
measurements, consistent with the tolerances given in Section
vessel to reflect the front line.
14. Alternatively, the existing barometric pressure may be
7.3.2 Setting the Meniscus—Settingofthemeniscusshallbe
obtained from the local weather service.
performed by one of the two methods detailed below. Wher-
6.4 Distilled or Deionized Water, suitable for general labo-
ever practical the meniscus should descend to the position of
ratory purposes.
setting.
7.3.2.1 The position of the lowest point of the meniscus
7. General Considerations
with reference to the graduation line is horizontally tangent to
theplaneoftheupperedgeofthegraduationline.Theposition
7.1 This section describes manipulative techniques required
ofthemeniscusisobtainedbyhavingtheeyeinthesameplane
to obtain accurate and reproducible volumetric measurements.
of the upper edge of the graduation line.
7.2 Cleaning Procedures:
7.3.2.2 The position of the lowest point of the meniscus
7.2.1 It is important that volumetric ware be thoroughly
with reference to the graduation line is such that it is in the
cleaned before being tested or used. Glass apparatus must be
plane of the middle of the graduation line. This position of the
sufficiently clean to permit uniform wetting of the surface.
meniscus is obtained by making the setting in the center of the
When clean, the walls will be uniformly wetted and the water
ellipse formed by the graduation line on the front and the back
will adhere to the glass surface in a continuous film.The clean
of the tube as observed by having the eye slightly below the
walls of some plastic apparatus, however, will not be wetted.
plane of the graduation line. The setting is accurate if, as the
(Follow the instructions of the manufacturer. Do not use
eye is raised and the ellipse narrows, the lowest point of the
materials which will attack, discolor, or swell the plasticware.)
meniscus remains midway between the front and rear portions
Lack of cleanliness causes irregularities in capacity by distort-
of the graduation line. By this method it is possible to observe
ing the water surface. The liquids usually used for cleaning
the approach of the meniscus from either above or below the
glassware are sodium dichromatic-sulfuric acid cleaning solu-
line to its proper setting.
tion (commercially available from laboratory supply houses),
nitricacid,fumingsulfuricacid,alcohol,andwater.Thechoice NOTE 1—The difference between meniscus positions resulting from the
alternativemethodsofadjustmentisthevolumeequivalentofonehalfthe
of cleaning agent to be used depends on the nature of the
thickness of the graduation line. In the case of articles where the capacity
contaminant. After cleaning with the cleaning solution and
is read as the difference between two meniscus readings (for example on
thoroughly rinsing with tap water, the vessel should be rinsed
a buret), then no error results if the article is manufactured using one
with distilled water.
method of adjustment and is later used by the other method.
Eveninthemostunfavorablecasesofsingle-markarticles(forexample
7.2.2 After cleaning, the vessel should be rinsed with ethyl
large flasks), when working to the highest attainable accuracy, the
alcohol and dried with clean air at room temperature. It is not
difference between the two methods of adjustment is unlikely to exceed
necessary to dry any vessel marked “to deliver.” When
30% of the Class A (precision apparatus) limit of error and a correction
cleaning small articles such as pipets, it is usually easier to fill
can be calculated where necessary.
themwithcleaningsolutionbysuction,usingavacuumline,if
8. Calibration Procedure for Burets
available, or a small rubber bulb, but never by mouth. The
solution should be drawn through the pipet several times until 8.1 Clamp the buret vertically on a support stand; also
the entire inside surface is evenly coated. Rinse thoroughly clamp a plain glass test tube, large enough to hold a
with tap water and then with distilled water. For cleaning thermometer, near the buret if the buret is of such a size that it
flasks, pour in enough cleaning solution while rotating so that is not large enough to insert a thermometer in the top for
E542 − 01 (2007)
observing the temperature of the water. Fill the buret from a 10.1.1 After cleaning and drying, weigh the empty flask
reservoir or storage bottle, in which the water has reached including the stopper. Place an appropriate sized funnel or
equilibrium with room temperature, and check to verify that otherfillingdeviceintheflasktodischargethewaterbelowthe
there is neither leakage from the tip nor from the stopcock capacity line. Fill from beaker or supply line taking care to
plug. Drain and record the delivery time. Delivery time is avoid wetting neck above capacity line.
determined by the unrestricted outflow of the water from the 10.1.2 Placetheflaskunderaburetandcompletefillingand
zero mark to the lowest graduation mark with the stopcock setting the meniscus, taking care not to splash water on the
fully open. Refill the buret to approximately 10 mm above the walls, after which place stopper in neck to lessen evaporation
zero mark and fill the test tube that holds the thermometer; and weigh. A pipet or dropper with a finely drawn tip may be
record the temperature. Set the meniscus on the zero mark used to adjust the meniscus instead of the buret. Determine the
usingtheburetstopcocktolowertheliquidlevelandtouchthe temperaturebyplacingathermometerinthefillingbeakerorin
tip with the wetted wall of a beaker to remove any excess one which has been filled from the water supply.The tempera-
water. A weighing flask that has been tightly stoppered and ture may be taken after final weighing by placing a thermom-
weighed empty is placed with the inside of the neck in contact eter directly in the flask, provided the flask is of sufficient size
with the tip of the buret (the flask will be at a slight angle). to accommodate it.
8.2 Fully open the stopcock until the water is only a few
11. Calibration of Flasks (to Deliver)
millimetres above the line being tested and then the stream is
11.1 Do not dry flasks that are calibrated to deliver prior to
slowed so as to make an accurate setting.When the setting has
the test. Fill the flask to approximately the index line and
been completed, move the flask horizontally, breaking the
empty rapidly by gradually inclining the flask so as to avoid
contact with the buret. Recheck the setting.
splashing on the walls as much as possible. When the main
8.3 Then stopper and weigh the flask a second time, after
drainage stream has ceased, the flask will be nearly vertical.
which refill the thermometer tube and test the next interval in
Hold in this position for 30 s and touch off the drop of water
the same manner as the first one—from the zero mark to the
adhering to the top of the flask. Place a watch glass or plastic
next interval needed.
cap on the flask to reduce evaporation and weigh immediately.
8.4 For burets with a specified waiting time, use the Take a water temperature reading, fill the flask, and make the
following procedure: after adjustment to the zero mark, fully meniscus setting on the index line, taking care not to splash
open the stopcock until the meniscus has reached a position a water on the walls. Place the same cap or watch glass on the
fewmillimetresabovethegraduationlineforcalibration.After filled flask and weigh. The reverse of this procedure may be
the specified waiting time (for example, 30 s), adjust the used, if desirable.
meniscus to the graduation line, remove the flask, a
...
This document is not anASTM standard and is intended only to provide the user of anASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation:E 542–00 Designation: E 542 – 01 (Reapproved 2007)
Standard Practice for
Calibration of Laboratory Volumetric Apparatus
This standard is issued under the fixed designation E 542; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope
1.1 This practice covers procedures for use in the calibration of volumetric ware, in accordance with Specification E694 such
as is in common use in chemical and clinical laboratories. It is based on the gravimetric determination of the quantity of water
either contained or delivered, and the conversion of this value to true volume at the standard temperature of 20°C by means of
suitable equations and standard tables. Calibration using mercury is excluded. Calibration may be performed using alternative
gravimetric methodology, provided that it is demonstrated and documented that the results obtained are equivalent to those
obtained using the methodology described herein.
3 3
1.2 This practice is intended to encompass capacity ware between the limits of 0.1 cm and 2000 cm .Typical products falling
withinthepurviewofthispracticeareburetsgraduated“todeliver”,graduatedcylinders,volumetricflasks,specificgravityflasks,
measuring and dilution pipets, and transfer and capacity pipets.
1.3 The procedures are not recommended for calibration of apparatus with capacities below 0.1 cm , such as microglassware.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
E1Specification for ASTM Thermometers
SI10Standard for Use of the International System of Units (SI) (the Modernized Metric System) ASTM Standards:
E694Specification for Volumetric Ware Specification for Laboratory Glass Volumetric Apparatus
3. Summary of Practice
3.1 Thispracticeisbaseduponadeterminationofthevolumeofwatereithercontainedinordeliveredbythevessel.Procedures
are given for cleaning, setting the meniscus, manipulating the apparatus, weighing, and converting the weight to the appropriate
standard volume.
4. Significance and Use
4.1 Theprimarypurposeofthispracticeistoprovideuniformproceduresthatmaybeusedtoaccuratelycalibrateawidevariety
of volumetric ware. The techniques are simple in concept and can provide reliable results, provided the procedures are followed
faithfully.Accordingly,thepracticeshouldprovideameansforcheckingtheoriginalcalibrationofglasswareandsimilarapparatus
and for periodic rechecks as the need should arise.
4.2 Borosilicate volumetric glassware will hold its calibration indefinitely provided that it is not exposed to hydrofluoric acid,
hot phosphoric acid, or strong, hot alkalis, and that it is not heated above 150°C when dry.Afrosting of the glass surface (viewed
when dry) indicates that chemical attack has occured, and recalibration may be in order. As a precaution, however, it is
recommended that the glassware be recalibrated after ten years of service regardless of its appearance.
4.3 Soda-lime volumetric glassware will become frosted with time because of attack from moisture in the atmosphere as well
as from the chemicals mentioned above. In addition, it should not be heated above 90°C when dry. It is recommended, therefore,
that it be recalibrated after five years of service unless frosting (viewed when dry) is observed sooner.
This practice is under the jurisdiction of ASTM Committee E41 on Laboratory Apparatus, and is the direct responsibility of Subcommittee E41.01 on Apparatus.
Current edition approved Nov. 10, 2000.1, 2007. Published November 2000.December 2007. Originally published as E542–79.approved in 1979. Last previous edition
E542–94(1999).approved in 2001 as E542–01.
ForreferencedASTMstandards,visittheASTMwebsite,www.astm.org,orcontactASTMCustomerServiceatservice@astm.org.For Annual Book of ASTM Standards
, Vol 14.03.volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E 542 – 01 (2007)
5. Units of Measurement
5.1 Capacity—The basic SI unit for volume is the cubic metre, m . Due to its large size, it is rarely used in volumetric
calibration. Rather, the cubic centimetre, cm , is used and will be employed in this practice. The unit, millilitre, mL, may be
considered as equivalent to the cubic centimetre.
5.2 Standard Temperature—Volumetric ware is almost universally calibrated at 20°C. The procedures described provide for
suchacalibration.Whenitisnecessarytoworkathigherambienttemperatures,suchasisthecaseintropicalcountries,calibration
may be required at the International Standards Organization (ISO) recommended temperature of 27°C. Equations are given to
correct the calibrated volume to other temperatures as this may be required or desired.
6. Apparatus
6.1 Balance, having sufficient capacity to weigh the loaded vessel.The sensitivity of the balance will be a limiting factor in the
accuracy of the measurements. Either a single-pan, direct-reading balance or an equal-arm balance of adequate sensitivity and
capacity may be used. In either case the weights must be calibrated with adequate accuracy. Ordinarily, weights with NBS Class
S-1tolerancesarerequired.Thebalancemusthavephysicaldimensionstoacceptthesizeofthevesselswhichneedtobeweighed.
6.2 Thermometer, for measuring the temperature of the water. The accuracy of this calibration will depend upon the accuracy
requirement of the volumetric calibration (see Section 14 for tolerances).
6.3 Barometer, capable of providing atmospheric pressure measurements, consistent with the tolerances given in Section 14.
Alternatively, the existing barometric pressure may be obtained from the local weather service.
6.4 Distilled or Deionized Water , suitable for general laboratory purposes.
7. General Considerations
7.1 This section describes manipulative techniques required to obtain accurate and reproducible volumetric measurements.
7.2 Cleaning Procedures:
7.2.1 Itisimportantthatvolumetricwarebethoroughlycleanedbeforebeingtestedorused.Glassapparatusmustbesufficiently
clean to permit uniform wetting of the surface. When clean, the walls will be uniformly wetted and the water will adhere to the
glasssurfaceinacontinuousfilm.Thecleanwallsofsomeplasticapparatus,however,willnotbewetted.(Followtheinstructions
of the manufacturer. Do not use materials which will attack, discolor, or swell the plasticware.) Lack of cleanliness causes
irregularities in capacity by distorting the water surface. The liquids usually used for cleaning glassware are sodium
dichromatic-sulfuric acid cleaning solution (commercially available from laboratory supply houses), nitric acid, fuming sulfuric
acid, alcohol, and water. The choice of cleaning agent to be used depends on the nature of the contaminant. After cleaning with
the cleaning solution and thoroughly rinsing with tap water, the vessel should be rinsed with distilled water.
7.2.2 After cleaning, the vessel should be rinsed with ethyl alcohol and dried with clean air at room temperature. It is not
necessary to dry any vessel marked “to deliver.” When cleaning small articles such as pipets, it is usually easier to fill them with
cleaning solution by suction, using a vacuum line, if available, or a small rubber bulb, but never by mouth. The solution should
be drawn through the pipet several times until the entire inside surface is evenly coated. Rinse thoroughly with tap water and then
with distilled water. For cleaning flasks, pour in enough cleaning solution while rotating so that a film of solution will cover the
entireinteriorsurface.Abreakinthefilmindicatesacontaminatedarea.Forfillingaburetwithcleaningsolution,itshouldbeheld
in a vertical position and filled by pouring into the top. Open the stopcock to drain. Regardless of the type of vessel, always rinse
thoroughly, first with tap water and then with distilled water. Plastic volumetric ware should be cleaned in an appropriate manner
before calibration.
7.3 Reading and Setting a Liquid Meniscus:
7.3.1 Reading the Meniscus—For all apparatus calibrated by this procedure, the reading is made on the lowest point of the
meniscus.Inorderthatthelowestpointmaybeobserved,itisnecessarytoplaceashadeofsomedarkmaterialimmediatelybelow
and behind the meniscus, which renders the profile of the meniscus dark and clearly visible against a light background. A
convenient device for this purpose is a collar-shaped section of thick black rubber tubing, cut open at one side and of such size
astoclaspthetubefirmly.Alternatively,blackpapermaybeused.“Shortline”graduatedvesselswherethelinesarelessthanone
half of the circumference may be read more accurately by placing a mirror against the rear of the vessel to reflect the front line.
7.3.2 Setting the Meniscus—Setting of the meniscus shall be performed by one of the two methods detailed below. Wherever
practical the meniscus should descend to the position of setting.
7.3.2.1 Thepositionofthelowestpointofthemeniscuswithreferencetothegraduationlineishorizontallytangenttotheplane
oftheupperedgeofthegraduationline.Thepositionofthemeniscusisobtainedbyhavingtheeyeinthesameplaneoftheupper
edge of the graduation line.
7.3.2.2 The position of the lowest point of the meniscus with reference to the graduation line is such that it is in the plane of
themiddleofthegraduationline.Thispositionofthemeniscusisobtainedbymakingthesettinginthecenteroftheellipseformed
bythegraduationlineonthefrontandthebackofthetubeasobservedbyhavingtheeyeslightlybelowtheplaneofthegraduation
line. The setting is accurate if, as the eye is raised and the ellipse narrows, the lowest point of the meniscus remains midway
between the front and rear portions of the graduation line. By this method it is possible to observe the approach of the meniscus
from either above or below the line to its proper setting.
E 542 – 01 (2007)
NOTE 1—The difference between meniscus positions resulting from the alternative methods of adjustment is the volume equivalent of one half the
thicknessofthegraduationline.Inthecaseofarticleswherethecapacityisreadasthedifferencebetweentwomeniscusreadings(forexampleonaburet),
then no error results if the article is manufactured using one method of adjustment and is later used by the other method.
Even in the most unfavorable cases of single-mark articles (for example large flasks), when working to the highest attainable accuracy, the difference
between the two methods of adjustment is unlikely to exceed 30% of the ClassA(precision apparatus) limit of error and a correction can be calculated
where necessary.
8. Calibration Procedure for Burets
8.1 Clamp the buret vertically on a support stand; also clamp a plain glass test tube, large enough to hold a thermometer, near
the buret if the buret is of such a size that it is not large enough to insert a thermometer in the top for observing the temperature
of the water. Fill the buret from a reservoir or storage bottle, in which the water has reached equilibrium with room temperature,
and check to verify that there is neither leakage from the tip nor from the stopcock plug. Drain and record the delivery time.
Delivery time is determined by the unrestricted outflow of the water from the zero mark to the lowest graduation mark with the
stopcockfullyopen.Refilltheburettoapproximately10mmabovethezeromarkandfillthetesttubethatholdsthethermometer;
recordthetemperature.Setthemeniscusonthezeromarkusingtheburetstopcocktolowertheliquidlevelandtouchthetipwith
the wetted wall of a beaker to remove any excess water.Aweighing flask that has been tightly stoppered and weighed empty is
placed with the inside of the neck in contact with the tip of the buret (the flask will be at a slight angle).
8.2 Fully open the stopcock until the water is only a few millimetres above the line being tested and then the stream is slowed
soastomakeanaccuratesetting.Whenthesettinghasbeencompleted,movetheflaskhorizontally,breakingthecontactwiththe
buret. Recheck the setting.
8.3 Thenstopperandweightheflaskasecondtime,afterwhichrefillthethermometertubeandtestthenextintervalinthesame
manner as the first one—from the zero mark to the next interval needed.
8.4 For burets with a specified waiting time, use the following procedure: after adjustment to the zero mark, fully open the
stopcock until the meniscus has reached a position a few millimetres above the graduation line for calibration.After the specified
waiting time (for example, 30 s), adjust the meniscus to the graduation line, remove the flask, and weigh.
9. Calibration Procedure for Pipets (One Mark)
9.1 Fill the pipet with distilled water by suction to the index mark and measure the delivery time with the tip in contact with
the glass surface of the internal side of a beaker. Refill by suction slightly above the index line. Record the temperature of the
distilled water in the beaker from which the pipet is filled. Remove any water on the outside of the tip by a downward wipe with
filter paper after the filling is completed. Then slowly lower the meniscus to the index using either a stopcock or hose clamp for
“fine control.”The tip must be in contact with the wet wall of a beaker while the setting is made on the index line. Do not remove
any water remaining on the tip at this time. Hold the pipet in a vertical position and deliver water into a previously weighed
weighing flask with the tip in contact with the inside wall of the neck of the flask. After the water has ceased to flow, wait 2 s,
then remove the pipet from contact with the flask. The flask is now stoppered and weighed with its contained load.
10. Calibration of Flasks (to Contain)
10.1 After cleaning and drying, weigh the empty flask including the stopper. Place an appropriate sized funnel in the flask to
discharge the water below the stopper. Fill from beaker or supply line, maneuvering the funnel so as to wet the entire neck below
the stopper. Let stand for about 2
...
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