Calibration involves determining an instrument's accuracy by comparing its readings to a standard instrument. Instruments should be calibrated according to the manufacturer's recommendations, after repairs or modifications, periodically, or whenever readings seem questionable. Common laboratory equipment calibrated include volumetric flasks, burettes, and pipettes. The calibration process for each involves taking multiple measurements of known volumes of water and performing calculations to determine accuracy. Class A equipment has tighter tolerances and higher accuracy than Class B. Tolerance is the acceptable range of variation in measurements.

3. What
Is Calibration?

4. • Calibration of an instrument is the process of
determining its accuracy. The process
involves obtaining a reading from the
instrument and measuring its variation from
the reading obtained from a standard
instrument. Calibration of an instrument also
involves adjusting its precision and accuracy
so that its readings come in accordance with
the established standard.

5. Why
To
Calibrate

6. There are three main reasons for having
instruments calibrated:
To ensure readings from an instrument are
consistent with other measurements.
To determine the accuracy of the instrument
readings.
To establish the reliability of the instrument
i.e. that it can be trusted.

7. When
To
Calibrate
?

8. When should you calibrate your measuring device?
A measuring device should be calibrated:
 According to recommendation of the manufacturer.
 After any mechanical or electrical shock.
 Periodically (annually, quarterly, monthly)
 When a specified usage (operating hours) has elapsed.
 After an instrument has been repaired or modified.
 Whenever observations appear questionable.
 Calibrate too often is waste of time & money.
 Calibrate too seldom is waste of product.
 Sudden changes in weather.
 A new instrument.
 Some experiments required calibration certificates.check the
requirements first before starting the experiment.
 Before major critical measurements.

9. Calibration Of Volumetric Glassware

10. Here we talk about three types of glassware typically used
by an analytical chemist.
 Burette.
 Volumetric flask.
 Pipette.

11. Requirements of glassware calibration
Calibrated weighing balance.
Calibrated thermometer, accurate to 0.1 ⁰C
with calibration certificate and values
traceable to NIST.
 Pure distilled or deionized water.
 Stop watch.
Glassware should be clean properly.

12. Volumetric flask
 Also called
measuring flask or
graduated flask.
It is a type of
laboratory flask,
calibrated to contain a
precise volume at a
particular
temperature.

13. Calibration procedure for Volumetric Flasks
Calibration Should be carried out at 25±2 ⁰C.
 Tare the weigh balance.
 Weigh the empty volumetric flask and record
value in gm. And note if this is Class-A or other
grade.
Fill the volumetric flask up to mark with
distilled water , and re-weigh it.
 Measure the temperature of the water used.
Repeat the process minimum five times.

14. Calculation performed for Volumetric Flask
Calibration

15. Burette
 A graduated glass tube
having a tapered bottom
with a valve.
 It is used especially in
laboratories to pour a
measured amount of
liquid from one container
into another.

16. Calibration procedure for Burette
 Calibration Should be carried out at 25±2 ⁰C.
 Use your cleaned 50mL burette. Note if this is a Class A or other grade. Fill the
burette with water. Make sure the tip is free of bubbles. Drain into a waste beaker
until it is at, or just below, the zero mark.
 Allow 10-20 seconds for drainage. Make an initial reading to a precision of at
least 0.01 ml. Test for tightness of the stopcock by allowing the burette to stand
for 5 minutes and then re-reading the volume. There should be no noticeable
change in the reading.
 Once the tightness of the stopcock is assured, refill the burette and again drain
into a waste until it is at, or just below, the zero mark.
 Drain about 5 mL of water from the burette into a clean previously weighed
beaker and weigh the beaker , and read the burette.
 Repeat the process five times for same volume .and repeat this process for
15,25,45 ml also.

17. Calibration form for Burette

18. Calculation performed for Burette Calibration

20. Pipette
A pipette is a
laboratory tool
commonly used
in chemistry, biology
and medicine for
measuring small
volumes of solutions.

21. Calibration Procedure for Pipette
 Weigh a clean and dry 50 mL beaker on a top loading balancing to 1 mg and record
the weight.
 Fill the 10 ml pipette to above the mark and remove any water adhering to the
outside of the pipette.
 Place the tip of the pipette in contact with the inside of beaker and slowly lower
the meniscus to the mark. Do not remove any more water from outside of the
pipette.
 Touch the top to the side of the weighed beaker and dispense the water until
holding the pipette vertically.
 After the water has ceased flowing, wait 2 seconds, and then remove the pipette
from the container.
 Reweigh the beaker, and calculate the weight of water in beaker. Record the water
temperature in your laboratory not-book.
 Repeat the process until you have 5 separate measurements for the same pipette.

22. Calculation performed for pipette calibration

23. Types
Of
Glassware

24. Class “A”
 Economy grade.
 Calibrated to half the
tolerance of class B.
 Have high accuracy.
 Use for quantitative
work.
 It always have a large “A”
prominent near the label.
Class “B”
 Student grade.
 Calibrated to double the
tolerance of class A.
 Have low accuracy.
 Use for qualitative & semi
quantitative work.
 Glassware without “A” label
is class “B”.

25. What
is
Tolerance
?
Tolerance is
the greatest
range of
variation that
can be allowed
for an
instrument or
equipment.

26. How to determine Tolerance Interval
 To determine the tolerance interval in a
measurement, add and subtract one-half of the
precision of the measuring instrument to the
measurement.
For example: if a measurement made with a 10ml
pipette is 5.6 ml and the pipette has a precision
of 0.1 ml, then the tolerance interval in this
measurement is 5.6 plus minus 0.05 ml, or from 5.55
ml to 5.65 ml. Any measurements within this range
are "tolerated" or perceived as correct.

27. Comparison Of Class A & B Tolerances for Volumetric Flask

28. Comparison Of Class A & B Tolerances for Pipettes

29. Comparison Of Class A & B Tolerances for Graduated
Cylinders.

30. Comparison Of Class A & B Tolerances for Burettes.

31. References
 Vogel's of quantitative inorganic analysis.
 David Harvey
 http://studylib.net
 http://www.wikihow.com
 http://camblab.info
 http://www.pharmaguideline.com
 https://msl.irl.cri.nz
 http://pharmapathway.com
 http://www.titrations.info
 http://www.regentsprep.org