Chemists form disodium phosphate by mixing sodium hydroxide with phosphoric acid, creating a chemical compound referred to as a sodium salt of phosphoric acid. The chemical formula, NA2PO4, reflects the name, showing two sodium ions attached to a phosphate group. Other names for this compound are dibasic sodium phosphate, disodium hydrogen phosphate and disodium acid phosphate. The physical properties of disodium phosphate make it a useful chemical for a variety of applications.
Physical Properties
Disodium phosphate comes in a variety of forms. The anhydrous, meaning without water, form appears as a white, odorless powder. The dehydrate, with two water molecules attached, forms a white crystalline odorless solid. Disodium phosphate dissolves easily in water. Scientists classify disodium phosphate as a base substance because of its pH of 9.0 to 9.6. The high pH makes it react violently with acid solutions, according to the International Programme on Chemical Safety.
Buffer
In chemistry, a buffer is a chemical solution that resists pH changes when a small quantity of acid or base is added to it. Disodium phosphate may be added to foods to act as a buffer. An example is non-dairy creamer; disodium phosphate is added to help the creamer, a basic solution, mix smoothly into the coffee, a slightly acidic solution.
Sequestrant
Food manufacturers add disodium phosphate to foods to function as a sequestrant -- a substance that improves the quality and stability of the food. Sequestrants serve as a kind of preservative, helping to ensure metal ions don't react with the food to cause oxidation. Disodium phosphate helps stabilize the proteins in foods like canned milk, cheese powders, pudding and ice cream. Stabilization also prevents the formation of bacterial cultures in foods like cheese starter cultures.
Emulsifier
A substance that acts as an emulsifier helps to keep two different substances, like water and oil, mixed together in one uniform solution. In buttermilk, disodium phosphate keeps the proteins evenly dispersed between the fatty, or butter-like, portion of the solution and the watery or milk-like portion. Disodium phosphate also helps keep cheese dips, cheese slices and sauces uniform.
Cooking Enhancement
Adding disodium phosphate to some foods alters their texture and enhances cooking, which decreases the cooking time. Cereal with disodium phosphate cooks in less time. Pasta products with disodium phosphate also cook in less time.
Saline Laxative
A saline laxative is a salt solution taken orally to induce rapid emptying of the lower intestine and bowel, according to the Mayo Clinic. These laxatives work by drawing in water from the surrounding tissues to soften stool and increase bowel movement. Disodium phosphate is one type of saline laxative doctors administer to patients prior to a diagnostic procedure such as a colonoscopy. It should not be used on a long-term basis to treat constipation.
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