1,10-Phenanthroline, indicator

Acid blue 9 2-Amino-4,6-dinitrophenol Basic green 1 Basic red 2 1,10-Phenanthroline indicator, acid-base... 

Determination of Azide as NaNt. Pipette a 25 ml portion of the sample into a 500 ml Erin flask and dil with w to 150-200 ml. Titrate with 40% sulfuric acid to just fo the phpht end-point, not overrunning it. Add N/10 ceric sulfate soln in 5 ml portions until the soln becomes deep yel, indicating an excess of ceric sulfate. Record the exact amt used. Add 10 ml of 40% sulfuric acid and 2 drops of o-phenanthroline indicator (prepd by dissolving 14.85 g of o-phenanthroline monohydrate, CiaHsNa HaO in 1 1 of 0.025 M freshly prepd ferrous sulfate... 

G. F. Smith and F. P. Richter, Phenanthroline and Substituted Phenanthroline Indicators. Smith Chem. Co., Columbus, Ohio, 1944. 

Although gravimetric methods have been used traditionally for the determination of large amounts of tellurium, more accurate and convenient volumetric methods are favored. The oxidation of teUurium(IV) by ceric sulfate in hot sulfuric acid solution in the presence of chromic ion as catalyst affords a convenient volumetric method for the determination of tellurium (32). Selenium(IV) does not interfere if the sulfuric acid is less than 2 N in concentration. Excess ceric sulfate is added, the excess being titrated with ferrous ammonium sulfate using o-phenanthroline ferrous—sulfate as indicator. The ceric sulfate method is best appHed in tellurium-rich materials such as refined tellurium or tellurium compounds. 

Wet-Chemical Determinations. Both water-soluble and prepared insoluble samples must be treated to ensure that all the chromium is present as Cr(VI). For water-soluble Cr(III) compounds, the oxidation is easily accompHshed using dilute sodium hydroxide, dilute hydrogen peroxide, and heat. Any excess peroxide can be destroyed by adding a catalyst and boiling the alkaline solution for a short time (101). Appropriate ahquot portions of the samples are acidified and chromium is found by titration either using a standard ferrous solution or a standard thiosulfate solution after addition of potassium iodide to generate an iodine equivalent. The ferrous endpoint is found either potentiometricaHy or by visual indicators, such as ferroin, a complex of iron(II) and o-phenanthroline, and the thiosulfate endpoint is ascertained using starch as an indicator. 

Ethereal methyl1ithiurn (as the lithium bromide complex) was obtained by the submitters from Aldrich Chemical Company Inc. The checkers used 1.19 M methyl1ithiurn-lithium bromide complex in ether supplied by Alfa Products, Morton/Thiokol, Inc. The concentration of the methyllithium was determined by titration with 1.0 M tert-butyl alcohol in benzene using 1,10-phenanthroline as indicator. The submitters report that ethereal methyllithium of low halide content purchased from Alfa Products, Morton/Thiokol, Inc., gave similar results. 

The extent of pitting is estimated by a special microscopical technique, or by the attack on the substrate using an appropriate indicator. Thus in the case of steel 1,10-phenanthroline hydrochloride is added to the electrolyte (solution B) to detect the formation of Fe ions. Alternatively, the specimens can be removed from the corrosion test solution and placed in an indicator solution, i.e. solution C for zinc-base die castings and solution D for steels. 

Procedure. Prepare a standard solution of lead nitrate (0.05M), a 0.05 per cent aqueous solution of xylenol orange indicator, and a 1,10-phenanthroline solution (0.05M) by dissolving 0.90 g of pure 1,10-phenanthroline in 1.5 mL of concentrated nitric acid and 100 mL of water. 

To determine the cadmium content, add 20-25 mL of the 1,10-phenanthroline solution and titrate the liberated EDTA with the 0.05M lead nitrate solution until the colour change from yellow to red-violet occurs — a little practice is required to discern the end point precisely. Introduce further 2-5 mL portions of the 1,10-phenanthroline solution and note whether the indicator colour changes if so, continue the titration with the lead nitrate solution. The consumption of lead nitrate solution corresponds to the cadmium content. 

One of the best oxidation-reduction indicators is the 1,10-phenanthroline-iron(II) complex. The base 1,10-phenanthroline combines readily in solution with iron(II) salts in the molecular ratio 3 base l iron(II) ion forming the intensely red l,10-phenanthroline-iron(II) complex ion with strong oxidising agents the iron(III) complex ion is formed, which has a pale blue colour. The colour change is a very striking one ... 

The standard redox potential is 1.14 volts the formal potential is 1.06 volts in 1M hydrochloric acid solution. The colour change, however, occurs at about 1.12 volts, because the colour of the reduced form (deep red) is so much more intense than that of the oxidised form (pale blue). The indicator is of great value in the titration of iron(II) salts and other substances with cerium(IV) sulphate solutions. It is prepared by dissolving 1,10-phenanthroline hydrate (relative molecular mass= 198.1) in the calculated quantity of 0.02M acid-free iron(II) sulphate, and is therefore l,10-phenanthroline-iron(II) complex sulphate (known as ferroin). One drop is usually sufficient in a titration this is equivalent to less than 0.01 mL of 0.05 M oxidising agent, and hence the indicator blank is negligible at this or higher concentrations. 

Internal indicators suitable for use with cerium(IV) sulphate solutions include AT-phenylanthranilic acid, ferroin [1,10-phenanthroline iron(II)], and 5,6-dimethylferroin. 

Complexes of bulky substituted phenanthrolines [Pt(N-N)LX2] (L, X both monodentate N-N, e.g. 2,9-dimethyl- 1,10-phenanthroline) can be 5-coordinate tbp when a good 7r-acceptor (e.g. C2H4) is present or 4-coordinate with monodentate phenanthrolines. Hartree-Fock calculations indicate that the 7r-acceptors reduce the electron density at platinum so that the metal can accept charge from another donor. Species of this kind may be involved in alkene hydrogenation [138]. 

Butyl lithium in hexane was obtained from Vcntron Corporation and stored in a refrigerator under argon. The solution was titrated with 2-butanol in xylene, using 1,10-phenanthroline as indicator. 

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