A test tube is a container used to hold a small amount of medicine,perform a small amount of reagent reaction at room temperature or under heating,and can be used to produce or collect small amounts of gas.Due to the fact that test tubes,like beakers,can be directly heated,they are widely used in laboratories.Below,I will explain the precautions when using test tubes.

When heating a test tube,the outer flame of an alcohol lamp should be used.Since the test tube cannot be directly held by hand during heating,the test tube holder should be used as a tool.When using a test tube clamp to pick up the test tube,the test tube clamp should be placed from the bottom of the test tube to the upper part of the test tube.If the length of the test tube is divided into three parts,it is reasonable to clamp the test tube clamp within one-third of the end near the test tube mouth.But this is not a mandatory rule,there is no need to rigidly copy it during the experiment.

Keep the test tube dry before heating,and preheat it before formal heating to fry.When heating,keep the outer wall of the test tube free of water droplets to prevent uneven heating and bursting.After heating is completed,wait for the test tube to cool before cleaning.

Due to the instability of the experiment,the solution in the test tube should not exceed 1/2 of the capacity of the test tube,and when heated,it should not exceed 1/3 of the capacity of the test tube.When using a dropper to add liquid into the test tube,it should not extend into the mouth of the test tube.