Impurity content in liquid and solid alkalis

It can’t be simply thought of that way. It depends on what kind of impurity you are referring to If it is a carbonate, it cannot be simply considered an impurity, as both solid and liquid strong bases will strongly absorb carbon dioxide from the air, and the amount of carbonate impurities is directly related to the storage conditions of the base, the environment, and the time elapsed. Furthermore, since carbonates have very low solubility in strong alkaline solutions, they tend to settle at the bottom of the container. When sampling the liquid for alkalinity testing, it is likely that the clear portion is taken, and as a result, the measured carbonate content may be low. Solid bases, however, are different; as they come into contact with ambient air, the carbonates formed accumulate on the surface of the base. When testing their purity, these carbonates directly affect the test results, causing it to appear as though there are more impurities (carbonates) in the solid base. It is recommended that for the analysis of strong-base impurities, the focus should be on anions and acid radicals other than carbonate, such as chloride and sulfate. Carbonate is an impurity present in strongly basic samples, and it should not be used as an indicator of low purity.

I checked that solid alkalis are prepared by evaporating liquid alkalis. I’m wondering whether, during preparation, it’s sufficient to simply evaporate the solution, or if other salts need to be added as seed crystals? We believe that the high level of impurities is not determined by the analysis reports, but rather by the consumption figures in the end-of-month statements. If it’s just about absorbing impurities such as heat-generated carbon monoxide from the air, can those be ignored?

During preparation, it is simply evaporated