Calibration of Volumetric Equipment

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Calibration of Volumetric Equipment

• Volumetric Flask (TC to contain)
• Buret (TD to deliver)
• Pipet (TD to deliver)
• Volumetric (or transfer)
• Mohr (or graduated) (not calibrated)

Thermometer
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CLEANING GLASSWARE

• Do NOT rinse at de-ionized water taps
• take flask back to own sink to rinse.
• Rinsing with de-ionized water should leave no
  droplets.
• For open and easily rinsed containers, use a
  cleansing powder, rinse with tap water and
  finally with de-ionized water.
• For burets, pipets, volumetric flasks, etc., use
  liquid detergent,
• rinse with tap water and finally with
  de-ionized water.
• NEVER use cleansing powder it is too hard to
  get out and in the case of burets it will usually
  score the Teflon stopcocks.

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Buret
Buret Drainage Times (Buret should drain
within 100-120 seconds)
Time After Delivery Volume Change After Drainage with Different Buret Free Delivery Times Volume Change After Drainage with Different Buret Free Delivery Times
30 sec 100 sec
1 min 0.01 mL 0.00 mL
10 min 0.10 mL 0.02 mL
Check Duplicate Runs by Approximate Method
V W
D V - W Run l 25.15 ml
24.97 g 0.18 Run 2 24.51 ml 24.36 g
0.15

?1 ?2 .03 Run l 35.19 ml
35.03 g 0.16 Run 2 34.47 ml 34.28 g
0.19
etc.
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• Name__________________________________ Lab
  Section________________
• Date Report Submitted___________________
• CALIBRATION OF VOLUMETRIC EQUIPMENT
• 1. Thermometer
• Thermometric Standard, true reading
  (TT) ___________C
• Desk Thermometer, observed reading
  (To) ___________C
• Thermometer Correction (TT - To) ___________C
• 2. Buret
• Series A Observed Mass
  of Corrected True
  Vol. Correction
• T(H2O), C Volume, Vo Water
  Mass Volume, VT
  VT Vo
• __________ ___________ ___________
  ___________ ___________ ___________
• (approximately 0-25mL)
• ___________
  ___________ ___________ ___________
  ___________
• (approximately 0-35mL)
• ___________
  ___________ ___________ ___________
  ___________
• (approximately 0-45mL)

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Archimedess Principle an object immersed in a
fluid is buoyed up by a force equal to the
weight of the fluid displaced. If an object is
larger in volume than the weights that balance
it, then it displaces more air and is buoyed up
by a greater force.
Buoyancy Correction
Mass of air displaced by object
?B daww1/do 1/dw
Mass of air displaced by weights
DB buoyancy correction da 0.00115 g/cm3
(density of air at room temperature) dw 8.0
g/cm3 (density of calibration weights) do
1.00 g/cm3 (density of water to 3 sig. fig.) o
object (water) ww mass read on balance
(mass of weights) wo actual mass of object
ww DB
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Volumetric Pipet Uncertainty of a SINGLE
MEASUREMENT Check the highest-lowest lt 0.03g
Thermometer Quartz thermometer Should be
within 0.5?C
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Storage of buret and pipet

• Fill with de-ionized H20
• Cork in top of buret (if old obtain a new cork)
• Rubber policeman on tips
• Loosen stopcock of buret slightly for storage.
  Remember to retighten when you use buret again.
• Store in buret cabinet