Most of the volumetric apparatus available in the United States are calibrated at 20°, and the National Institute of Standards and Technology (NIST) has adopted 20° as the reference temperature for the calibration of laboratory glassware, although the temperatures generally prevailing in laboratories are usually between 20° and 25°. To minimize volumetric error, the temperature should be the same for the volumetric apparatus, the material being prepared, the solvents being used to prepare the volumetric solutions, the area in which they are prepared, and the final volume adjustment. To attain the degree of precision required in many Pharmacopeial assays involving volumetric measurements and directing that a quantity be “accurately measured”, the apparatus must be chosen and used with care.