United States Coast Guard does NOT require the life preserver to bemade_
A. with as few strings as possible
B. capable of being worn on both sides
C. according to each wearer s size
D. confortable and light to we ar
查看答案
洗涤沉淀是为了洗去表面吸附的杂质及混杂在沉淀中的母液()
氨水沉淀分离法中,常加入NH4CL等铵盐,其作用是为了控制溶液的PH()