一. Instruments for heating

Instruments that can be directly heated include test tubes, evaporating dishes, and crucibles; instruments that need to be indirectly heated through asbestos mesh include beakers, flasks (round-bottom flasks and distillation flasks), and conical flasks; common heat sources in chemical experiments are alcohol lamps.

1. test tube

Main uses: ①Used as a reactor for a small amount of reagents. ② Collect a small amount of gas.

Precautions for use:

①When holding the test tube with the test tube clamp or the iron clamp on the iron stand, it should be clamped at 1/3 of the test tube mouth to facilitate heating or observation.

②Before heating, the water on the outer wall of the test tube should be wiped dry to prevent the test tube from being heated unevenly and ruptured.

③ The liquid contained in the test tube should not exceed 1/2 of the test tube when not heated, so as to facilitate vibration, and not exceed 1/3 of the test tube when heated to prevent the liquid from flushing out.

④ When heating the liquid, the test tube should be inclined at 45° to expand the heating surface; when heating the solid, the nozzle should be slightly inclined downward to prevent the condensed water from flowing back and causing the test tube to burst.

⑤ When heating, the nozzle is not allowed to face people, so as to avoid accidents.