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Chemical Properties of Silica Gel

If you have purchased a new pair of shoes or handbag, you probably noticed a small packet containing small beads. These beads are actually silica gel. This common chemical substance is used in a wide variety of applications as an absorbent material. Silica gel is non-toxic, however it should not be ingested.

  1. Chemical Formula

    • The molecular formula for silica gel is SiO2, comprised of silicon and oxygen. Some forms of silica gel can contain amounts of cobalt, chlorides, sulfates and ammonium compounds. Trace elements can allow the gel to indicate if it has reached its saturation point. Silica gel is widely manufactured and available for purchase. It is not known to be carcinogenic to humans, so safety standards have not been implemented.

    Appearance

    • Silica gel is not actually a gel, as in a gelatinous substance. It is a solid, and most often comes in the form of tiny spheres, or beads. The manufacturers often package the beads into small pouches made out of a porous paper or cloth. To the touch, it feels similar to any common plastic. Silica gel can be white, blue or sometimes pink. The colored forms of silica gel provide an indication of saturation. Generally cobalt chloride is added as an indicator. The indication type of silica gel is generally more expensive, so it is used less.

    Properties

    • Silica gel's pH ranges between 2.3 and 7.4. It has no odor or vapor pressure. It does not evaporate under normal conditions. Silica gel will boil at 4046 degrees Fahrenheit. It's melting and freezing point are 3110 degrees Fahrenheit. These conditions are not reached under normal usage of the chemical. Silica gel cannot be dissolved in water. Chemically, it is stable. However, it's incompatible with strong acids and hydrogen fluoride.

    Uses

    • Silica gel is used in a wide variety of industries for shipping and preserving goods. The surface area of the gel beads is extremely high. This allows the chemical to absorb and retain moisture from the environment. Protecting goods, such as food and medicine, from moisture prevents spoiling and allows them to be shipped longer distances. Silica gel also helps products to retain longer shelf-lives. Silica gel is relatively harmless. The forms with cobalt added may be harmful if swallowed or if the dust from the product is inhaled. As with any chemical, care should be taken when handling. The bags of silica gel found in products should not be opened.

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