Cerium reactions with phosphorous

Chromates, vanadates, and cerium salts give colour reactions with the reagent and should therefore be absent. Iron salts give a yellow colour with hydrogen peroxide, but this is eliminated by the addition of syrupy phosphoric acid. Fluorides bleach the colour (stable [TiF6]2 ions are formed), and large amounts of nitrates, chlorides, bromides, and acetates as well as coloured ions... 

Detection is carried out with cerium (IV) stdphate (Bgt. No. 37). It cannot be used with layers impregnated with silver nitrate, nor with alumina layers. Iodine vapour or solution (Rgt. No. 143) or para-formaldehyde-phosphoric acid (Rgt. No. 194) can be used also and 2,4-dinitrophenylhydrazine (Rgt. No. 82) with alkaloids containing a keto group. The cerium (IV) sulphate reagent is recommended as a universal detection agent zl -unsaturated compounds yield a colour reaction even in the cold. Iodine vapour permits non-destructive detection of the sterol alkaloids, so that they may be subsequently isolated unchanged. 

Spec determination of the colored complex in a phosphoric acid medium Spec A = 513 nm of the red-colored radical cation formed upon the reaction of PPP with cerium(lV) in a phosphoric acid medium Spec titration of the cerium (IV) complex (pH = 8 to 10)... 

---