The bite or grit test is a quick and useful method that is used to identify sand silt, or clay. In this test, a small pinch of solid material is ground lightly between the teeth. The soils are identified as follows:

. SANDY SOILS. The sharp, hard particles of sand grate harshly between your teeth and are highly objectionable. This is true even of the fine sand.

. SILTY SOILS. The silt grains are so much smaller than sand grains that they do not feel nearly so harsh between your teeth. They are not particularly gritty although their presence is still easily detected.

. CLAYEY SOILS. The clay grains are not at all gritty, but feel smooth and powdery like flour between the teeth. Dry lumps of clayey soils stick when lightly touched with your tongue.

The slaking test is used to assist in determining the quality of certain soil shales and other soft rocklike materials. To perform this test, place the soil in the sun or in an oven to dry. Then allow it to soak in water for at least 24 hours. After this, examine the strength of the soil. Certain types of shale disintegrate completely and lose all strength.

The acid test is used to determine the presence of calcium carbonate. It is performed by placing a few drops of hydrochloric acid on a piece of soil. A fizzing reaction (effervescence) to this test indicates the presence of calcium carbonate. The degree of reaction gives an indication of the concentration. Calcium carbonate normally is desirable in a soil because of the cementing action it adds to the stability. (Some very dry noncalcareous soils appear to effervesce after they absorb the acid. This effect can be eliminated in all dry soils by moistening the soil before applying the acid.) This cementing action normally develops only after a long curing period and cannot be counted upon for strength in most military construction. The primary use for this test is to give abetter value of fine-grained soils that you have tested in place.

The shine test is another means of measuring the plasticity characteristics of clays. A slightly moist or dry piece of highly plastic clay has a definite shine when rubbed with a fingernail, a pocketknife blade, or any smooth metal surface. On the other hand, a piece of lean clay does not display any shine, but remains dull.

The feel test is a general-purpose test that requires experience and practice before reliable results can be obtained. Two characteristics you can determine by the feel test are consistency and texture.

The natural moisture content of a soil is of value as an indicator of the drainage characteristics, nearness to the water table, or other factors that may affect this property. A piece of undisturbed soil is tested by squeezing it between the thumb and forefinger to determine its consistency. The consistency is described by such terms as hard, stiff, brittle, friable, sticky, plastic, or soft. Remold the soil by working it in your hands. Observe changes, if any. You can use the feel test to estimate the natural water content relative to the liquid or plastic limit of the soil. Clays that turn almost liquid on remolding are probably near or above the liquid limit. If the clay remains stiff and crumbles upon being remolded, the natural water content is below the plastic limit.

The term texture, as applied to the fine-grained portion of a soil, refers to the degree of fineness and uniformity. The texture is described by such expressions as floury, smooth, gritty, or sharp, depending upon the sensation produced by rubbing the soil between the fingers. Sensitivity to this sensation may be increased by rubbing some of the material on a tender skin area such as the wrist. Fine sand feels gritty. Typical dry silts will dust readily and feel relatively soft and silky to the touch. Clay soils are powdered only with difficulty but become smooth and gritless like flour.