Reduction with iron ammonium sulfate

Reduction to the corresponding dediazoniated pyrazoles was achieved by using titanium trichloride or iron(II)ammonium sulfate (79S194). The yields are moderate with ammonium sulfate and higher with titanium trichloride. The exothermic reaction that takes place with development of nitrogen is somehow slower with the iron salt, but can be completed by... 

Oxidation-Reduction Titrations. The extent of reduction resulting from reaction of niobium (V) chloride and bromide with pyridine was determined by indirect titration of crude reaction mixtures with standard ammonium tetrasulfato-cerate(IV) solution. Samples were stirred overnight in a stoppered flask with an excess of iron (III) ammonium sulfate. Any iron (II) formed by reaction with the niobium complex mixture was then titrated with the standard tetrasulfato-cerate(IV) solution using ferroin as indicator. Results of these determinations are given in Table III. 

The separation of uranium from the Ions Interfering with Its analysis Is accoiqpllshed by the adsorption of the uranlum(Vl) sulfate oomplex on a quaternary ammonium anion exchange resin. Interference of such Ions as Iron(lll) and vanadlum(V) Is avoided by their preferential reduction with sulfurous acid so that they, as well as other cations, are not retained by the resin. Uranium Is eluted for analysis by dilute perchloric acid. The method Is applicable to both solutions and ores. 

---