Error in measuring rock porosity by Archimedes method

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SUMMARY

The Archimedes method for measuring rock porosity involves saturating the rock with water, weighing it in air and water, and calculating porosity based on the weight difference. A significant source of error arises from improper drying of the rock's surface, which can lead to inaccurate measurements of pore space. The discussion highlights the need for a reliable source that quantifies the expected error from this drying process. Additionally, there is curiosity about the relevance of mercury porosimeters in contemporary practices.

PREREQUISITES
  • Understanding of Archimedes' principle
  • Knowledge of rock saturation techniques
  • Familiarity with weighing methods for submerged objects
  • Basic principles of porosity measurement
NEXT STEPS
  • Research the accuracy of Archimedes' method in geological studies
  • Explore publications on error analysis in porosity measurements
  • Investigate the use of mercury porosimeters in modern geology
  • Learn about alternative methods for measuring rock porosity
USEFUL FOR

Geologists, materials scientists, and researchers involved in rock analysis and porosity measurement will benefit from this discussion.

Peter Persoff
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The standard way to measure porosity of a rock is to get the pores completely saturated with water, then weigh the rock immersed in water and again in air (there are modified balances for this). Using Archimedes' principle, you then can determine the volume of the rock. Then you dry the rock completely and weigh it again (only in air). The water weight lost gives you the pore space in the rock. Divide this into the total volume and you get the porosity.

A major source of error is that when you weigh the rock after taking it out iof the water you have to blot the outside surface dry. Not dry enough and you are weighing some exterior water. Too dry and you will suck some of the water out of the pores and the rock is no longer saturated.

What I am looking for is a textbook or other publication that tells the amount of error to be expected from this source. Anyone with information or experience with this method is welcome to reply.
 
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The standard way? What ever happened to mercury porosimeters?
 

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