Volumetric glassware precision

Instrument/Equipment Effects Examples include the calibration and precision of an analytical balance, the specified tolerance for volumetric glassware and a temperature controller that maintains a mean temperature which is different (within specification) from its indicated value. 

Some volumetric glassware products have a large A imprint on the label. This designates the item as a class A item, meaning that more stringent calibration procedures were undertaken when it was manufactured. Class A glassware is thus more expensive, but it is most appropriate when highly precise work is important. This imprint may be found on both flasks and pipets. 

TABLE 1 Capacity tolerances of precision (class A) volumetric glassware... 

Using information on the purity of the material used to prepare the spiked sample, and the accuracy and precision of the volumetric glassware and analytical balance used, the uncertainty in the concentration of Cl solvent red 24 in the sample, (CRM), was estimated as 0.05 mg l-1.1 The uncertainties associated with the concentration of quinizarin and Cl solvent yellow 124 were estimated as 0.025 mg 1 1 and 0.062 mg 1 1, respectively. The relevant values are ... 

Q8.5 Based on the precision of an analytical balance and volumetric glassware, what is the precision of the calculated stock concentration ... 

We commonly measure liquid volumes with precision volumetric glassware such as burets, pipets, and volumetric flasks. The National Institute of Standards and Technology in the United States has established specifications for Class A glassware two examples are listed in Table 2.2 on the next page. We may accurately determine the volume of a vessel at one temperature from the mass of a liquid of known density, such as water, that fills the vessel at this temperature. 

Figure 3.5 Volumetric glassware. The beaker is only for estimating volumes. The taU graduated cylinder is used to measure volume more accurately. The flask with the tall neck (volumetric flask) and the pipet are used to obtain samples of fixed but precisely measured volumes. The buret is used to dispense variable volumes with high precision. 

On the other hand, it would be foolhardy to use the cheapest volumetric glassware and generally poor laboratory practice, and then expect to realize the full beneHts of a sophisticated measurement technique such as precision colorimetry. ... 

Titrimetric analysis is sometimes called volumetric analysis because it is characterized by the frequent measurement of solution volume utilizing precision glassware. 

A volumetric flask is a precision piece of glassware with a single calibration line in a narrow neck An Erlenmeyer is not a precision piece of glassware and has graduation lines on it only as a rough indication of volume. 

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