Potassium ferrate sample

An impure sample of potassium ferrate, K2Fe04, may be prepared as follows Dissolve sufficient ferric chloride, FeCl3,6H20, to correspond to 40 g. Fe(OH)3 in 2 1. of hot water and precipitate the hydroxide with potassium hydroxide. Wash the precipitate repeatedly with hot water by decantation until nearly all chlorides have been removed and evaporate the suspended hydroxide to a volume of about 65 cc., bringing it into a porcelain dish that will hold about 250 cc. Break up 25 g. of solid potassium hydroxide into small pieces and add it to the ferric hydroxide, warming the mixture to insure solution. 

Potassium ferrate (VI) has been prepared in an impure state and in low yields by the action of chlorine or bromine on hydrous iron(III) oxide suspended in potassium hydroxide solutions. The procedure described here is a modification of the chlorine oxidation method1 which facilitates the prediction of 5- to 10-g. samples of potassium ferrate (VI) in a fair state of purity and in good yield. 

By this procedure, samples ranging in purity from 90 to 97% potassium ferrate (VI) are obtained in yields as high as 50%. If centrifugation is used instead of filtration, yields up to 75% can be obtained. ... 

If it is desirable to obtain a sample of greater purity than those prepared by the recommended procedure, the sample may be subjected to an additional reprecipitation from 6 M potassium hydroxide solution, using the same procedure as described above. Such additional purifications of samples give products ranging in purity from 98.5 to 99% potassium ferrate (VI) however, a large amount of the potassium ferrate (VI) is lost in the process. 

TABLE 24.3 Hyperfine Parameters and Relative Spectrum Areas of the Mossbauer Spectra of the Potassium Ferrate(VI) Sample ... 

Solid or semi-solid samples may require extraction with an aqueous solution to isolate the ionic components in a form suitable for IC. The actual procedures vary widely, depending on the type of sample. For example, meat and sausage products to be analyzed for nitrate and nitrite are first homogenized mechanically, extracted wth a 5 % borax buffer solution in a hot water bath, and then subjected to a precipitation with strong solutions of potassium hexacyano ferrate and zinc sulfate. The aqueous extracts are diluted further with de-ionized water and filtered through a membrane prior to injection. 

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