Further data on the preparation of extremely pure sodium chloride crystals

Abstract
The following methods for purification of sodium chloride were compared in relation to their effectiveness: ion exchange, extraction, crystallization from solution, precipitation and distillation. For the purification of sodium chloride the ion exchange followed by a crystallization from solution in a teflon vessel appeared to be the most effective method giving a sodium chloride with an alkaline earth content about 1 × 10−7mole/mole.