Periodates of Sodium, Potassium, and Barium

The periodates of the alkali metals1 are best prepared by oxidation of iodate by chlorine.2 The oxidation can also be effected by persulfate,3 but this is inferior as a preparative method and is to be recommended only when no ready supply of chlorine is available. 

Sodium Iodate. This compound, from which all of the following are prepared, may be readily obtained by oxida- 

In a 5-1. flask, 125 g. of pure sodium chlorate is dissolved in 500 ml. of water at 45°C. After acidification with 2 ml. of concentrated nitric acid, 100 g. of iodine is added. The mixture is warmed until reaction just begins (at 50°C., if the acidity is correct). To prevent loss of iodine, the mouth of the flask is lightly closed with an inverted beaker. Provision should be made for immersing the flask in cold water in case the reaction becomes too vigorous. Complete disappearance of the iodine ordinarily requires 10 or 15 minutes. The iodate solution is then ready to be oxidized to periodate. 

The best yields are obtained when the alkali concentration is near that expressed by (2). Under these conditions, nearly pure Na3H2I06 is formed although a small amount of the other salt may be present. 

The solution is made slightly alkaline with sodium hydroxide (to change any Na2H3I06 to the less soluble Na3H2I06), cooled, and filtered. The precipitate is washed several times with eold water (below 20°C.) and dried at 

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