What is a primary standard solution?
A primary standard is one that can be determined to a high level of precision, and reliability. For instance, a typical acid-base titration can be done to determine the concentration of an unknown HCl solution. When titrated against NaOH there will be some uncertainty because of the lack of reliability of the NaOH concentration. A primary standard is prepared to standardize the NaOH solution, so that the HCl concentration will be both more precise and more accurate. A primary standard is usually an easily dried solid weak acid that can be massed on an analytical balance to a high level of precision. Potassium hydrogen phthalate (aka, KHP) is often used for this.
