Step 1.
Pour solution C and D into solution B and mix thoroughly;
Then fully roll stirring (300r/min stirring for 20min).
At the same time, the A solution is roller-stirred until there is no more precipitate (300r/min>20min).
Step 2.
The BCD mixture was poured into solution A and rolled(300r/min) maturation;
Maturation time: Summer: 8h, Winter: 12h.
