A high purity metaphosphate is characterized in that the concentration of each coloring metal element serving as an impurity is 5 ppm or less. The metaphosphate is an aluminum salt, a barium salt, a calcium salt, a magnesium salt, or a strontium salt. The aluminum salt is suitably produced by means of a production method comprising a first step of producing a reaction mixture containing aluminum biphosphate by reacting an aluminum compound with phosphoric acid by heating, a second step of placing the reaction mixture containing aluminum biphosphate obtained in the first step in a firing vessel on which aluminum metaphosphate powder is spread in advance and subjecting the reaction mixture to firing, and a third step of pulverizing the fired product obtained in the second step.
高纯度的代
磷酸盐的特点在于作为杂质的每种有色
金属元素的浓度都在5ppm或以下。代
磷酸盐是铝盐、
钡盐、
钙盐、
镁盐或
锶盐。铝盐适宜通过生产方法制备,该方法包括第一步,通过加热反应铝化合物和
磷酸制备含铝双
磷酸盐的反应混合物,第二步,在预先铺有铝代
磷酸盐粉末的烧结容器中放置所得的含铝双
磷酸盐反应混合物,并对其进行烧结,第三步,粉碎所得的第二步的烧结产物。