When to Use Which Balance

The question of which balance to use under given circumstances, an ordinary balance or an analytical balance, remains. An analyst must be able to recognize when a weight measurement with four or five decimal places is needed (analytical balance) or when one with only one to three decimal places is needed (ordinary balance). 

Second, if the results of a quantitative analysis are to be reported to three or more significant figures, then weight measurements that enter directly into the calculation of the results should be made on an analytical balance so that the results of the analysis can be correctly reported after the calculation is performed. 

if a weight is only incidental to the overall result of an accurate quantitative analysis, then it need not be made on an analytical balance. This means that if the weight measurement to be performed has no bearing whatsoever on the quantity of the analyte tested, but is only needed to support the chemistry or other factor of the experiment, then it need not be measured on an analytical balance. 

Fourth, if a weight measurement does directly affect the numerical result of an accurate quantitative analysis (in a way other than entering directly into the calculation of the results, which is the second case mentioned above), then it must be performed on an analytical balance. 

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