Use in fertilizers Superphosphate fertilizers are produced by treatment of "
phosphate rock" with acids ("acidulation"). Using
phosphoric acid,
fluorapatite is converted to Ca(H2PO4)2: This solid is called
triple superphosphate. Several million tons are produced annually for use as
fertilizers. Using
sulfuric acid,
fluorapatite is converted to a mixture of Ca(H2PO4)2 and CaSO4. This solid is called
single superphosphate. Residual HF typically reacts with silicate minerals co-mingled with the phosphate ores to produce
hexafluorosilicic acid (H2SiF6). The majority of the hexafluorosilicic acid is converted to
aluminium fluoride and
cryolite for the processing of aluminium.
Use as leavening agent Calcium dihydrogen phosphate is used in the food industry as a
leavening agent, i.e., to cause baked goods to rise. Because it is acidic, when combined with an alkali carbonate ingredient, commonly
sodium bicarbonate (baking soda) or
potassium bicarbonate, it reacts to produce
carbon dioxide and a
salt. Outward pressure of the carbon dioxide gas causes the rising effect. When combined in a ready-made
baking powder, the acid and alkali ingredients are included in the right proportions such that they will exactly neutralize each other and not significantly affect the overall
pH of the product. AMCP and MCP are fast acting, releasing most carbon dioxide within minutes of mixing. It is popularly used in
pancake mixes. In double-acting baking powders, MCP is often combined with the slow-acting acid
sodium acid pyrophosphate (SAPP). ==See also==