What is the main function of a weigh boat?

The main function of a weigh boat is to serve as a container that holds a substance when being massed on a balance. This provides a clean and convenient way to measure the mass of a sample without contaminating it or the balance. The use of weigh boats helps ensure accuracy in weighing by preventing the sample from coming into direct contact with the balance pan, which can be affected by residue or moisture from previous materials. This is particularly important in laboratory settings where precision is critical.

The other options describe functions that are not related to the weighing process. For instance, filtering liquids requires a different type of apparatus, typically a filter or funnel. Mixing solid substances would involve containers or tools designed for creating a homogeneous mixture, such as mortar and pestle or mixing bowls. Measuring pH levels is done using a pH meter or pH indicator solutions, which are entirely different from the purpose of a weigh boat.