건조 직후에 침전물이 형성되는 것을 관찰하고, 상기 용액을 여과하고 불순물을 씻어내기 위해 아세톤으로 세척하였다.
It was observed that a precipitate was formed immediately after drying, and the solution was filtered and washed with acetone to wash off impurities.