1. The problem statement, all variables and given/known data My textbook states that one of the safety precautions to be taken in the fractional distillation of petroleum(in school laboratory) is using a small flame to heat the rocksil(rocksil is soaked with petroleum),and avoil using stationary flame for heating. Can anyone explain? 2. Relevant equations 3. The attempt at a solution I guess the reason of using a small flame is to avoid the breaking of test tube(test tube is used to hold the rocksil)?But I have no idea on why shouldn't we use a stationary flame for heating.