On the Influencing Factors on H_3BO_3 Recrystallization

Discusses emphatically some influencing factors on the recrystallization of H3BO3,such as the solution concentration,crystallization temperature/time and stirring speed in the solution of H3BO3-H2O system.The rate of crystallization can be up to over 88% if the crystallization temperature/time is constant and the boric acid concentration is controlled within 28.5%～31.0%.And if the crystallization temperature is selected in the range of 5～10 ℃,the different cooling ways all effect slightly the crystallization rate of boric acid.But, if a quenching is implemented during high temperature with the temperature cooled to a certain extent and then cooled slowly,most of boric acid crystals are provided with a certain grain size.In our lab the proper crystallization time is about 15 h.If the boric acid solution concentration is 28.5%,and final crystallization temperature is 10 ℃ that is held for 15 h,the slow stirring speed benefits the formation of boric acid crystals.