What is the primary function of a test tube brush?

The primary function of a test tube brush is to clean test tubes. These brushes are specifically designed with bristles that can effectively reach the curved surfaces and narrow openings of test tubes, allowing for thorough cleaning. Cleaning test tubes is crucial for ensuring that no residual substances interfere with subsequent experiments or contaminations occur between different samples. Proper cleanliness in laboratory equipment is essential for maintaining the integrity of experiments and obtaining valid results.

The other options, while relevant to laboratory tasks, do not accurately describe the main purpose of a test tube brush. Measuring liquids involves the use of graduated cylinders or pipettes; stirring solutions typically requires a stirring rod or magnetic stirrer; and holding samples securely can be accomplished with test tube holders or racks. Each of these tasks is essential in the lab, but they are distinctly different from the cleaning function of a test tube brush.