Ion-exchange separation of magnesium

The ion-exchange method is highly reproducible with a c.v. of 0.03 % but is rather time-consuming. 

The gravimetric determination of potassium as its barely soluble tetraphenylborate is recommended and described here. This method has also been applied to seawater for an ocean-wide survey of the element (see Table 11-1). The procedure is preferred because of its high accuracy and precision and the minimum amount of equipment required to perform the analysis. Basically, the method outlined here is that developed by Wittig (1950) and Raff and Brotz (1951). A brief description of a potentiometric method is presented in Section 11.2.3.6. 

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Table II. Ion-Exchange Separation of Magnesium, Calcium, and Strontium (6)...

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