Volumertic Glassware

Report
Bangladesh BEST Programme
Calibration of Volumetric Glassware
By
Gravimetric Method
Nihal Gunasekara
Sri Lanka
Bangladesh BEST Programme
Laboratory used Glassware
 Burette
 Single-volume pipette
 Graduated pipettes
One-mark volumetric flasks
Graduated measuring cylinders
Bangladesh BEST Programme
DEFINITIONS
Unit of volume
Ref. temperature
 To deliver
 To contain
Cubic centimeter : ml
20 °C
Apparatus is calibrated to
accurately transfer the stated
volume to another container.
Apparatus is calibrated to an
accurate measure of the volume
contained
Bangladesh BEST Programme
Apparatus Needed
 Balance
 Thermometer
Hygrometer
 Barometer
Water Distilled water /De-ironized
Pipette Sucker
Bangladesh BEST Programme
Recommended Apparatus - Balance
Selected Volume (V)
10 ml < V < 1000 ml
1000 ml < V < 2000 ml
V > 2000 ml
Resolution of
Balance (mg)
Std. Deviation
(mg)
1
1
10
10
100
100
Bangladesh BEST Programme
Recommended Apparatus/Liquids
Apparatus/Liquid
Maximum Error
Thermometer
0.1 °C
Hygrometer
5%
Barometer
1 k Pa
Calibration Liquid
Distilled /de-ionized water
Bangladesh BEST Programme
Test Room Conditions
Temperature
Humidity
Stabilization
M
Maintained at 20 ± 1 °C and during
calibration ± 0. 5 °C stability
Maintained 35% to 85%
Prefer to maintain at 60 ± 10%
Volumetric instruments and test water
1 to 2 hours
Bangladesh BEST Programme
Preparation
Cleaning of volumetric glassware
 Internal surface of volumetric vessels shall be cleaned
sufficiently before the calibration
 Oil or grease is removed by suitable solvent
 The vessel should be nearly filled with an aqueous solution
of a soap less detergent and shaken vigorously. It should
then be repeatedly rinsed with distilled water
 Be sure that vessel is cleaned before commence calibration
Bangladesh BEST Programme
Calibration Procedure
 Prior to any calibration test make sure that all
instruments reached the ambient temperature in
the laboratory
 During the calibration maximum temperature
variation in the laboratory should not exceed
±0.5oC.
 Set or read a meniscus against a reference line or
scale
 Be sure that the vessel or weighing bottle and
the distilled water are at room temperature.
Bangladesh BEST Programme
Calibration Procedure
 Fill distilled water up to the required volume
 Weigh the testing container with distilled water.
 Measure the temperature of distilled water
using the thermometer.
 Repeat the above step three times and record
in the data recording form.
 Repeat the above steps for cylinders at least at
four different volumes
Bangladesh BEST Programme
Calibration Procedure –Flask & Cylinder (contain)
1. Weigh the empty testing container and record the
value
2. Fill distilled water up to the required volume
3. Weigh the testing container with distilled water .
4. Measure the temperature of distilled water using
the thermometer.
5. Repeat the above step 2 through 4 three times and
record in the data recording form.
6. Repeat the above step 2 through 5 for cylinders at
least at three different volumes
Bangladesh BEST Programme
Calibration Procedure – Pipette (deliver)
1. Weigh a empty container and record the value
2. Fill pipette with distilled water up to the index mark
3. Any water on the outside of the tip is removed with
filter paper after the filling is completed
4. Transfer the distilled water to empty vessel,
weighted in step (1)
5. Weigh the vessel with distilled water .
6. Measure temperature of distilled water using the
thermometer
7. Repeat the above steps three times and record in
the data recording form.
Bangladesh BEST Programme
Calibration Procedure – Burette (deliver)
1. Weigh empty container and record the value
2. Fill burettes with distilled water up to the index mark
3. Any water on the outside of the tip is removed with filter
paper after the filling is completed
4. Transfer the distilled water to empty vessel, weighed in
step (1)
5. Weigh the vessel with distilled water
6. Measure temperature of distilled water using the
thermometer.
7. Repeat the above steps three times and record in the data
recording form.
8. Repeat the above steps 1 through 7 for Burettes at least
three different levels
Bangladesh BEST Programme
Principle of calibration - volumetric glass ware
 1   a 
 * 1   * 1   t  20
V20  ( RL  RE  * 
  w  a   b 
Bouncy effect
Temperature effect
Z values are given in Tables B6, B7 and B8 in ISO 4787 : 2010 for different
types of glass at common air pressure Vs temperature
14
Bangladesh BEST Programme
Notations
R L- is the balance reading of vessel with water
reference liquid in grams
RE - is the balance reading of empty vessel in grams
Ρa - is the density of air, in grams per milliliter
ρb - when weighing in air as though the density
of the weight was 8.0 g/ml.
ρw - is the density of water at toC, in grams per
milliliter.
ϒ - is the coefficient of cubical thermal expansion
of the material of which the item of glassware,
tested is made in reciprocal degrees Celsius,
t - is the temperature of the water used in testing
in degrees Celsius.
Bangladesh BEST Programme
Density of Air- Table B3 ISO 4787
Temperature
930
940
950
Air Pressure
hPa
960
970
980
990
1000
1010
19
1.104 1.116 1.1128 1.140
1.152 1.164 1.176 1.188
1.200
20
1.100 1.112 1.124
1.148 1.160 1.172 1.183
1.195
21
1.096 1.108 1.120
1.136
1.132
1.144 1.155 1.167 1.179
Density values in 10 -3
grams per milliliter
1.191
Bangladesh BEST Programme
Density of water – Table B4 ISO 4787
Temperature
°C
19
20
21
Density (g/ml)
ρw
0.99840
0.99820
0. 99799
Bangladesh BEST Programme
Coefficient of Cubical Thermal Expansion
Material
Borosilicate glass 3.3
Borosilicate glass 5.0
Soda-lime glass
Coefficient of cubical thermal
expansion ϒ-1 °C 10-6
9.9
15
27
Bangladesh BEST Programme
Data Recording
Use spread sheet for data recording
Record Temperature, Humidity,
Barometric pressure
Record final data in a data recording
sheet
Review from a third party
Prepare the final calibration certificate
Bangladesh BEST Programme
20

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