Guide, Part 7: Particle Density
Soil Particle Density
1. A good soil for growing plants should generally contain about 50% pore space and 50% solids. The pore space should consist of half air and half water, and the solids should be made up mostly of minerals (sand, silt, and clay particles) mixed with some organic matter.
2. In the soil, air and water are found within the pore spaces between the particles. If this ideal soil were dried out, and all the pore space were compressed so that there was no more air and no more space, all that would remain would be the solid portion of the soil.
3. To calculate bulk density, we would measure the mass of the total volume of a soil sample.
4. To calculate particle density, we would measure the mass of the volume of only the solids in the soil sample.
5. Weigh out 25g soil and pour Distilled water in squirt bottle.
6. Weigh empty flask without the cap.
7. Place 25g of soil into flask (wipe outside of flask clean) and get their mass without the cap.
8. Using squirt bottle, add approximately 50mL Distilled water into the flask. (Wash any soil on the neck back into the bottom of the flask.)
9. Bring soil and water mixture to a gentle boil for 10 minutes.
10. During this time, agitate the flask for 10 seconds every minute.
11. Remove flask from heat and allow it to cool. Cap flask and let sit for 24 hours. Cap flask and let sit for 24 hours.
12. At 24 hours, remove cap and add enough Distilled H2O to bring volume to 100mL (the bottom of the meniscus should be at 100mL).
13. Weigh the soil and water mixture without the cap.
14. Take temperature reading by placing thermometer into the water in the flask for one minute. (Take out, clean and dry thermometer.)
15. Calculate the soil particle density using the Soil Particle Density Data Sheet.