双水解.
Na2B4O7 + 2NH4Cl + 5H2O = 2NaCl + 4H3BO3↓ + 2NH3↑
硼酸H3BO3在冷水中溶解度不大,会析出（白色沉淀）.NH3就不一定逸出了,看溶液浓度而定.