Substances ammonium persulphate

Davis and Ashdown devised methods for detecting these substances in powder. If the alcoholic extract from powder contains diphenylamine it forms a blue colour with ammonium persulphate N-nitrosodiphenylamine gives no coloration with this reagent. The intensity of the colour developed by a mixture of both substances evidently depends upon the concentration of diphenylamine. On the other hand N-nitrosodiphenylamine gives an intense blue coloration to concentrated sulphuric acid. 

About 0 5 gm. of the substance is weighed accurately into a 500 ml. flask and 10 ml. water and 5 ml. nitric acid are added. The mixture is then heated, ammonium persulphate being added until the solution becomes clear. If the liquid persistently remains yellow, showing that the substance is refractory, it is boiled for several minutes with a few ml. water and several gm. of ammonium persulphate. 

In practice, eluents of widely varying polarity have been used. Very weakly polar steroids (oestrenols) can be quantitatively eluted with hydrophobic solvents like methylene dichloride (cf Table 14) [217], whereas difficulties are reported in the elution of the more polar progesterone under the same conditions [691]. Chloroform has been used to elute dinitrophenylhydrazones from silica gel and opium alkaloids from alumina [470, 535]. Methanol and ethanol are often used for elution of substances of all types of compound class from silica gel [213, 215, 259, 434] or alumina [122, 437]. Butyl acetate has been chosen as the most suitable eluent for penicillin V [486]. Acetone has proved suitable for recovering ubiquinones [733]. Polar neutral, acid and basic aqueous eluents have also been employed, e.g., water for mucic acid derivatives [451] (cf Table 14), 1% Tween 80 solution for cobalamin [128], 0.2 N sulphuric acid for Vitamin Bg factors [702], 34% ammonium persulphate solution for nicotinic acid [702] and ammonium hydroxide for azo dyes [638]. Nitro-4-acetaminophenetoles have been extracted from alumina with the highly polar dimethylformamide [489]. 

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