What is a characteristic property of the primary standard that distinguishes it from secondary standards?

The primary standard is distinguished by its consistently stable nature, which is crucial for ensuring accurate and reliable measurement in laboratory settings. A primary standard is a highly pure chemical substance that can be used to calibrate measuring instruments and perform quantitative analyses because it retains its properties over time and can be precisely quantified. This stability allows for reproducible results in experiments and ensures that the standard can serve as a reliable reference point.

In contrast, secondary standards may not possess the same level of stability or uniformity. While they can be useful in various applications, their reliability can be affected by factors such as exposure to environmental conditions and degradation over time. Thus, the primary standard's characteristic of being consistently stable is what sets it apart and makes it essential in laboratories for accurate measurements and standardization.