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Sodium polyacrylate (repeating unit: -CH2-CH(CO2Na)- ) is a crosslinked acrylic acid polymer sodium salt, invented by Robert Niles Bashaw, Bobby Leroy Atkins and Billy Gene Harper in the Basic Research Laboratory of the Dow Chemical Company. Polymers were produced which absorbed up to 1,000 times their weight in distilled water (gel capacity) and are called polyelectrolytes. These polymers are referred to as "Super Absorbents" and "Water Crystals".
When dry, the polymer appears as a white powder and when in gel form it is a transparent slush/gel. It is used in diapers, bed pads, fire control, spray drift control, seed germination, soil conditioning,period pads, and hydroponics. It is hard water and salt sensitive in that dissolved minerals greatly reduce the absorption capacity of the gel. Other high-gelling capacity crosslinked salts of polyacrylic acid include potassium, lithium, and ammonium salts.
Sodium polyacrylate is also used in many industrial applications, as a thickening agent, as an aid for dissolving soaps, as a spill absorbing media in laminated structures from urine test kits to nuclear waste cleanup and in thin tape structures used in cables for longitudinal water blocking.
It is also used, under the colloquial name of water crystals, as a water storage agent for soils, in that it soaks up excess water and discharges it when the soil becomes drier. Its use in dry countries is increasing, as people use it to avoid watering the garden with drinkable water.
One variation can be found for sale online as "Instant Snow." It is also used in the movie industry for set decoration.
Exposure of Sodium Polyacrylate in powder or gel form to Alcohol will turn the chemical a deep magenta color until the Alcohol evaporates.