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1.
(1) Understand the significance of volumetric vessel calibration
(2) Learn how to calibrate glass measuring instruments such as burettes, pipettes, and volumetric flasks
(3) Familiar with the use of burettes, volumetric flasks, pipettes and the weighing operation of analytical balances
2.
Burettes, pipettes, volumetric flasks, etc.
(1) The relative calibration method is to calibrate based on the proportional relationship between the volumes of the two volumetric instruments when they are used in parallel
(2) Absolute correction method (weighing method) Weigh the pure water mass (m) measured in or out of the glass measuring device, and then calculate the water's corrected density (p correction ) at that temperature to calculate when the measuring device is at 20℃ The actual volume
The correction density of water P correction takes into account the increase and decrease of water density and the expansion and contraction of glassware when temperature changes, as well as the influence of air buoyancy when weighing in the air.
Table 1-3 The density value of water after comprehensive correction at different temperatures
For example: 10.
The correction value of the burette volume in this section is △ V =V 20 -V T =10.
(3) Solution volume versus temperature calibration.
Table 1-4 Volume correction value of 1L dilute solution (or water) converted to 20℃ at different temperatures
For example, if the titration operation is performed at 10°C and 25.
3.
(1) Analyze the balance
.
(2) Acid (base) burette: 50mL
.
(3) Volumetric flask: 250mL
.
(4) Pipette: 25mL
.
(5) Conical flask with stopper: 50mL
.
(6) Thermometer: the minimum graduation value is 0.
1℃
.