What Is the Function of a Test Tube Holder and a Test Tube Rack?

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A test tube holder's purpose is for holding test tubes in place, but they can also be useful for holding pipettes and stirring rods as well, and a test tube rack holds multiple test tubes in place. Some test tube racks can hold up to 40 test tubes. There are other racks designed for storing test tubes and holding even larger numbers of test tubes during a long period of time.