反应详情

In a dissolving step 30, 22 g of cerium nitrate hexahydrate is dissolved in 500 ml of a distilled water by stirring, for thereby providing a colorless and transparent cerium nitrate solution. Like the tin tetrachloride in the illustrated first embodiment, the cerium nitrate in the solution of this embodiment is ionized into cerium ions Ce3+ and nitric acid ions NO3−. This dissolving step 30 corresponds to the step of preparing the acidic solution. The dissolving step 30 is followed by a stirring step 32 in which 50 ml of 25% ammonia water, for instance, is added by dripping to the prepared solution, so that a cerium hydroxide (Ce(OH)3) is precipitated in the form of a brown deposit according to the neutralization reaction similar to that represented by the above formula (1). The precipitated cerium hydroxide takes the form of nanograins whose average grain size is about several nanometers (nm). This stirring step 32 corresponds to the step of precipitating the metal hydroxide.