9.9 : 标准溶液

A standard solution is a solution with an accurately known amount of substance. It is prepared from a primary standard—a highly pure, high molar mass, hydrophilic, and stable substance.

The preparation involves accurately weighing the appropriate amount of a primary standard in a weighing boat and transferring it into a volumetric flask using a funnel. The empty weighing boat is reweighed to check for any remaining solid substance.

Add small quantities of distilled water to wash down the solids in the funnel into the flask. The volumetric flask is swirled to dissolve the solid completely. More water is added until its level reaches close to the calibration mark. At this juncture, water is pipetted to increase the solution level exactly to the calibration mark.

The flask is closed and inverted several times to ensure complete mixing. Label the flask with the chemical composition, concentration, and date of preparation.

This primary standard solution is used to standardize secondary standards – less pure and less stable substances.