Lessons on Soil

by Edward J. Russell

8. Crumble some of the dried soil as finely as you can with your fingers. Then sift it through a sheet of clean wire gauze. What fraction of the soil is fine enough to go through the gauze? Describe the portion which will not pass through the gauze. Count the number of wires per linear inch in the gauze.

9. Mix some of the soil with water in a flask. Let it stand. How long does it take before the water becomes quite clear again?

10. Mix some more soil with water. Let it settle for 30 seconds only. Pour off the muddy water into a tall glass cylinder. Add more water to the remaining soil, and pour off a second portion of muddy water, adding it to the first, and so on until all the fine mud is removed from the soil. Allow this muddy water ample time to settle.

11. When the fine mud has settled pour off the bulk of the water; stir up the mud with the rest of the water; transfer it to an evaporating basin, and evaporate to dryness.

12. Does this dried mud consist of very tiny grains of sand or of some material different from sand? Can you find out with a microscope?

13. If the mud consists of real clay and not of sand it should be possible to burn it into brick. Moisten the dried mud again. Roll it if you can into a round clay marble. Leave this to dry slowly for a day. Then bake it either in a chemical laboratory furnace or in an ordinary fire.

14. Return to the soil used in Question 10, from which only the fine mud has been washed away. Pour more water on to it, shake it well, and pour off all the suspended matter without allowing it more than 5 seconds to settle. Repeat the process. Collect and dry the poured off material as before. What is the material this time, sand or clay?

15. Wash the remaining portion of the soil in Question 14 clean from all matter which does not settle promptly. Are there any pebbles left? If so, how large are they, and of what kind of stone?

16. Take a fresh sample of the soil. Mix it with distilled water in a flask. Boil the mixture. Allow it to settle. Filter. Divide the filtrate into two portions. Evaporate both, the larger portion in an evaporating basin over wire gauze, the smaller portion in a watch glass heated by steam. Is any residue left after heating to dryness?

17. Take a fresh sample of soil. Spread it on a clean sand bath and heat strongly with a Bunsen flame. Does any portion of the soil burn? Is there any change in its appearance after heating?