Liquid Density Analysis

1
Liquid Density Analysis

• By
• Amanda Stiff
• CH EN 4903
• November 22, 2006

2
Overview

• Objective
• Laboratory Equipment and Procedure
• Densitometer
• Pycnometer
• Results
• Conclusions and Recommendations
• Questions

3
Objective

• Identify the density of an unknown salt solution
  using two different methods
• Densitometry
• Pycnometry
• Determine which method is most accurate

4
Equipment - Densitometer

• Natural frequency or period (T) of a hollow
  U-tube is measured to determine the density of a
  liquid or gas
• Constants A and B in the equation are solved
  using density for water and air.

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Equipment - Densitometer (cont.)

• The unknown liquid was injected into the
  densitometer and the period (T) was read from the
  display
• Using the equation for the densitometer the
  density of the liquid is found
• A 2 molar solution was run for calibration
  purposes

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Equipment - Pycnometer

• Pycnometers utilize the basic equation for
  density
• ? mass/volume
• The volume is known
• and the mass is weighed
• on a scale

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Results - Densitometer
Densitometer _at_ 25.2oC Densitometer _at_ 25.2oC Constants A 0.0706 B 18.3721 B 18.3721
Air Water 2 Molar Unknown
Period (T) 4.2884 5.7023 5.7948 5.7046
  4.2884 5.7022 5.7946 5.7047
  4.2884 5.7021 5.7947 5.7047
Average (T) 4.2884 5.7022 5.7947 5.7047
Density (g/cm3) 0.0013 0.9982 1.0733 1.0002
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Results - Pycnometer
Pycnometer (10 ml) Pycnometer (10 ml)
Empty Water (70oF) 2 Molar Unknown
Average Weight (g) 11.7815 21.9137 22.6935 21.9400
Average - Empty (g)   10.1322 10.9120 10.1585
Density (g/cm3)   1.0132 1.0912 1.0159
Density via SG (g/cm3) Density via SG (g/cm3) 0.9982 1.0750 1.0008
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Results Comparison

• Densitometer results (95 CI)
• ? 1.0002 /- 0.0004 g/cm3
• Pycnometer results (95 CI)
• ? 1.0008 /- 0.014 g/cm3

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Conclusions and Recommendations

• Densitometer was the more accurate method
• Pycnometry is a much easier method
• Know what kind of liquid you put into the
  densitometer
• Happy Thanksgiving

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References and Acknowledgements

• CRC Handbook of Chemistry and Physics. 48th ed.
  Ohio Chemical Rubber Co., 1967-68
• National Institute of Standards and Technology.
  Retrieved August 30, 2006, from
  www.nist.gov/srd/pdf20files/jpcrd196.pdf, Page
  29
• Thanks to my lab partner Randy Pummill

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Questions?