What is the term used to describe a 99.95% purified chemical that can be precisely measured?

The term that describes a 99.95% purified chemical that can be precisely measured is known as a primary standard. Primary standards are highly pure chemical substances that have been thoroughly characterized and can be used to determine the concentration of a solution through precise measurements. Their high level of purity allows for accurate calculations and reliable laboratory results, making them essential in analytical chemistry, particularly in titration processes.

Primary standards are often stable compounds that do not absorb moisture from the air and have well-defined properties, such as molar mass and reactivity. This reliability makes them the preferred choice for calibrating measurement instruments and for quantitative analysis.

In contrast, secondary standards are typically solutions whose concentration is determined by comparison to primary standards, making them less pure or less accurately defined. Calibration standards are used to adjust the accuracy of instruments and measurements, while reference standards serve as a benchmark for comparison but may not meet the strict criteria of primary standards regarding purity.