A product which contains acid magnesium pyrophosphate (magnesium dihydrogen diphosphate) and at least magnesium orthophosphate, producible by removal of water from an aqueous solution or suspension of a magnesium phosphate compound which has a molar ratio of Mg:P of 0.4-0.6:I, wherein the product has a loss on ignition of 7.5 to 13.5% and its method of preparation and its use in a leavening agent for bakery products.