What is a filter flask commonly used for?

A filter flask is commonly used for TSS (Total Suspended Solids) and total coliform testing because of its design that facilitates the filtration process. When analyzing water samples for TSS, a filter flask, often equipped with a vacuum source, is employed to ensure efficient separation of particulate material from the liquid. This setup allows for the collection of solid particulates on a filter, making it easier to measure and analyze the concentration of suspended solids in the sample.

In the case of total coliform testing, filter flasks help in capturing microbial contaminants from water samples efficiently. The vacuum method employed with the flask aids in drawing the sample through a membrane filter, retaining the coliform bacteria for subsequent analysis.

The other choices do not accurately reflect the primary use of a filter flask. Transferring liquids typically involves standard laboratory glassware like beakers or graduated cylinders, measuring precise volumes requires volumetric flasks or pipettes, and mixing chemical solutions is more suited to flasks or stirrers. Therefore, the function of the filter flask in the context of TSS and total coliform testing is what makes this answer the most appropriate.