Calibrations, Calibration, and Accuracy

The volumetric marks on volumetric ware are called calibrations. How they were located on the volumetric ware is called calibration. All volumetric ware is calibrated to provide its stated volume at 20°C. The International Standards Organization has recommended that the standard volumetric temperature should be changed to 27 °C. However, so far there has not been any significant movement toward this goal. The ASTM recommends that those labs in temperate climates that are unable to maintain an environment at 20°C should maintain one at 27°C. 

There are many labs that not only are unable to maintain a 20°C temperature, but cannot maintain any temperature consistently. Temperature variations can create problems if you are attempting to do accurate work. The more accurate the work, the greater the need to maintain room temperature at 20°C. Alternatively, include the temperature of the liquid at the time of measurement in your experiment log. Then, at a later time, apply corrections to all measurements made to conform to ASTM 20°C measurements. However, do not waste your time doing unnecessary work. The correction for any given measurement may be irrelevant if either (1) its result is smaller than the tolerances of your equipment (2) it involves 

Another concern for accuracy is based on how accurately the user can read calibrations on the volumetric ware. The reproducibility of an individual user will be more consistent than the reading made by a variety of users. Therefore, if there will be a variety of users on any given apparatus, all who are likely to use it should make a series of measurements. This way, the individual errors can be calculated. The ASTM has analyzed the range of errors made by trained personnel, and the reproducibility of these results are shown in Table 2.9. 

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