<P> A volumetric flask (measuring flask or graduated flask) is a piece of laboratory glassware, a type of laboratory flask, calibrated to contain a precise volume at a particular temperature . Volumetric flasks are used for precise dilutions and preparation of standard solutions . These flasks are usually pear - shaped, with a flat bottom, and made of glass or plastic . The flask's mouth is either furnished with a plastic snap / screw cap or fitted with a joint to accommodate a PTFE or glass stopper . The neck of the volumetric flasks is elongated and narrow with an etched ring graduation marking . The marking indicates the volume of liquid contained when filled up to that point . The marking is typically calibrated "to contain" (marked "TC" or "IN") at 20 ° C and indicated correspondingly on a label . The flask's label also indicates the nominal volume, tolerance, precision class, relevant manufacturing standard and the manufacturer's logo . The volumetric flasks are of various sizes, containing from 1 to 20 000 mL of liquid . </P> <P> Calibration and toleration standards for volumetric flasks are defined in the following standard specifications and practices: ASTM E288, E542, E694, ISO 1042, and GOST 1770 - 74 . According to these specifications, volumetric flasks come in two different classes . The higher standard flasks (Class A, Class 1, USP or equivalent depending on the country) are made with a more accurately placed graduation mark, and have a unique serial number for traceability . Where this is not required, a lower standard (Class B or equivalent) is used for qualitative or educational work . </P>

What is the function of a volumetric flask