Calibration of Burette

Calibration of Burette

1.0 Purpose: This SOP describes a procedure for the measurement of capacity of burette.

2.0 Scope: This SOP is applicable to all burette of different nominal capacity.

3.0 Responsibility: It is the responsibility of Quality Assurance Manager to ensure that the procedure is followed.

4.0 Materials and Equipment Used:
4.01A weighing balance that is calibrated with traceable weights and regularly maintained.
4.02 A calibrated thermometer.
4.03 A weighing vessel.
4.04 Distilled water.
4.05 Acetone.
4.06 4% Acetic acid solution
4.07 Soap solution
4.08 Burette stand 
4.09 Worksheets or forms to record the raw data.

5.0 Procedure: The determination of capacity of burette is based on weighing water and calculating mass and volume based on the density at the appropriate temperature.
5.01 Clean the burette thoroughly with soap solution and water to remove any adhering dirt or grease. Rinse the volumetric flask with acetic acid solution and then wash with water till free from all acid.
5.02 Dry the burette by rinsing with acetone and clamp it vertically on a burette stand.
5.03 Fill the burette with distilled water at ambient temperature sufficiently above the zero mark. 
5.04 Place a glass vessel below the jet of the burette and open the stopcock fully.
5.05 Stop the outflow when the meniscus is slightly above the zero graduation line, ensuring that no air bubble is entrapped within the burette.     
5.06 Open the stopcock slowly and set the meniscus at the zero graduation line. Remove any drop adhering to the jet by bringing a glass vessel into contact with the jet.
5.07 Setting of the meniscus at any graduation line shall be performed as follows – 
       (a) Set meniscus so that the plane of the top edge of the graduation line is horizontally tangential to the lowest point of the meniscus, the line of sight being in the same plane.
       (b) In order to minimize possible errors the same method of setting shall be used for both zero and other readings.
5.08 Take a tared weighing vessel (W1), place it below the jet of the burette and open the stopcock fully to allow free descent of water meniscus, taking care that jet does not come into contact with the wall of the receiving vessel during the delivery period.
5.09 Stop the outflow when the meniscus reaches a few ml above the graduation line up to which accuracy is to be determined. Allow a ‘waiting time’ of 30 seconds and then make the final setting of meniscus by controlling the outflow and gradually stopping it when the meniscus touches the graduation line.
5.10 After the setting of meniscus at a particular graduation line is done, add any drop, adhering to the jet, to the delivered volume by bringing the inside of the receiving vessel into contact with the jet and weigh the vesel (W2).
5.11 Note the temperature of water and calculate the volume of water delivered by the burette at the reference temperature of 270C.

6.0 Calculation: Calculate the volume of water delivered by the burette  using the following formula – 
                                            V= W2 – W1 / D
V    = Volume of the burette, Cm3 (ml)
W1 = Weight of empty weighing vessel.
W2 = Weight of empty weighing vessel & distilled water.
D    = Density of water at 270C (i.e. 0.9965 g /cc)

7.0 Reporting: Record all the observations in the worksheets or forms. Calculate the correct volume of water delivered by the burette and, the amount by which this differs from the indicated volume, is the volumetric error.                       

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