Sodium aluminium phosphate (SAlP) describes the inorganic compounds consisting of sodium salts of aluminium phosphates. The most common SAlP has the formulas NaH₁₄Al₃(PO₄)₈·4H₂O and Na₃H₁₅Al₂(PO₄)₈.Klaus Schrödter, Gerhard Bettermann, Thomas Staffel, Friedrich Wahl, Thomas Klein, Thomas Hofmann "Phosphoric Acid and Phosphates" in ''Ullmann’s Encyclopedia of Industrial Chemistry'' 2008, Wiley-VCH, Weinheim. These materials are prepared by combining alumina,

phosphoric acid Phosphoric acid (orthophosphoric acid, monophosphoric acid or phosphoric(V) acid) is a colorless, odorless phosphorus-containing solid, and inorganic compound with the chemical formula . It is commonly encountered as an 85% aqueous solution, w ...

, and sodium hydroxide."Phosphoric Acids and Phosphates" David R. Gard, 2005, Wiley-VCH. In addition to the usual hydrate, an anhydrous SAlP is also known, Na₃H₁₅Al₂(PO₄)₈ (CAS#10279-59-1), referred to as 8:2:3, reflecting the ratio of phosphate to aluminium to sodium. Additionally an SAlP of ill-defined stoichiometry is used (Na_''x''Al_''y''(PO₄)_''z'' (CAS# 7785-88-8). The acidic sodium aluminium phosphates are used as acids for

baking powder Baking powder is a dry chemical leavening agent, a mixture of a carbonate or bicarbonate and a weak acid. The base and acid are prevented from reacting prematurely by the inclusion of a buffer such as cornstarch. Baking powder is used to increas ...

s for the chemical

leavening In cooking, a leavening agent () or raising agent, also called a leaven () or leavener, is any one of a number of substances used in doughs and batters that cause a foaming action (gas bubbles) that lightens and softens the mixture. An altern ...

of baked goods. Upon heating, SAlP combines with the baking soda to give

carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...

. Most of its action occurs at baking temperatures, rather than when the dough or batter is mixed at room temperature. SAlPs are advantageous because they impart a neutral flavor. As a food additive, it has the E number E541. Basic sodium aluminium phosphates are also known, e.g., Na₁₅Al₃(PO₄)₈. These species are useful in cheese making.

References

{{reflist Sodium compounds Aluminium compounds Phosphates E-number additives