Transcript Volumertic Glassware
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 Cubic centimeter : ml
Ref. temperature 20 °C
To deliver Apparatus is calibrated to accurately transfer the stated volume to another container
.
To contain 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 Thermometer Hygrometer Barometer Calibration Liquid Maximum Error 0.1 °C 5% 1 k Pa Distilled /de-ionized water
Bangladesh BEST Programme
Test Room Conditions
Temperature Humidity
M
Stabilization 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 ±0.5
o C.
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
V
20 (
R L
R E
*
w
1
a
* 1
b a
* 1
t
20 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
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Bangladesh BEST Programme Notations
R L-
is the balance reading of vessel with water reference liquid in grams
R E -
is the balance reading of empty vessel in grams Ρ
a -
is the density of air, in grams per milliliter ρ
b
- when weighing in air as though the density of the weight was 8.0 g/ml.
ρ
w
- is the density of water at t o C, 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 Air Pressure hPa 930 940 950 960 970 980 990 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 1.136 1.148 1.160 1.172 1.183 1.195 21 1.096 1.108 1.120 1.132 1.144 1.155 1.167 1.179 1.191
Bangladesh BEST Programme Density of water
–
Table B4 ISO 4787 Temperature Density (g/ml) °C ρ
w
19 0.99840
20 0.99820
21 0. 99799
Bangladesh BEST Programme Coefficient of Cubical Thermal Expansion Material Coefficient of cubical thermal
expansion ϒ -1 °C 10 -6
Borosilicate glass 3.3 9.9
Borosilicate glass 5.0 15 Soda-lime glass 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
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