Introducing unreacted material back into a process and repeating a chemical reaction is considered to be reprocessing unless it is part of the established process.将未反应的物料返回某一工序，并重复化学反应，这是进行返工返工，除非它已被列入规定的工艺中。
The crude products could be purified by extractions with ethyl alcohol and decalin to remove the unreacted polypropylene glycol and dihydroxy-terminated polystyrene, respectively.粗产物可分别用乙醇及十氢茶萃取，以除去未反应的聚丙二醇及端双羟基聚苯乙烯。
