Q. Illustrate Clay content test?

Under this test, the clay content is measured by washing it off the sand sample. The standard dried sand sample (50 gm) is put in a mixing device along with distilled water and 1% NaOH solution. The mixture is stirred for 5 minutes and is then allowed to settle for 10 minutes. The sand settles down at the bottom. The dirty water is siphoned off from the top. The operation is repeated until the water above the sand in the mixture is clean. This water is drained off. The sand is dried and weighed. The loss of weight gives the clay content.