PREPARATION OF AMORPHOUS CALCIUM PHOSPHATE HAVING HIGH PURITY FROM AQUEOUS SOLUTION OF PHOSPHORIC ACID CONTAINING IMPURITY

摘要

PURPOSE:To obtain amorphous calcium phosphate having high purity extremely easily by allowing phosphoric ions in an aq. soln. of phosphoric acid contg. impurities to react with Ca ions in a specified pH range. CONSTITUTION:After adjusting a pH of a phosphoric acid soln. contg. impurities to 2-4 with aq. ammonia, disodium ethylenediamine tetracetate is added to the soln., then a soln. (a) of a Ca salt is added thereto. Then, the soln. is dropped into a soln. (b) of Ca salt having a pH held at 6-8, pref. 7. In this case, the whole operation should be cared to be performed at =40 deg.C. A buffer soln. comprising hydrogen diammonium phosphate and aq. ammonia may be useful for the soln. (a) having the adjusted pH. Aq. soln. of CaCl2, or a soln. contg. CaCO3 or Ca(OH)2 dissolved in an acid (hydrochloric acid, HNO3) may be used for the above described aq. soln. of Ca salt (b).