Titrations indicators

Titration Indicators. Concentrations of arsenic(III) as low as 2 x 10 M can be measured (272) by titration with iodine, using the chemiluminescent iodine oxidation of luminol to indicate the end point. Oxidation reactions have been titrated using siloxene the appearance of chemiluminescence indicates excess oxidant. Examples include titration of thallium (277) and lead (278) with dichromate and analysis of iron(II) by titration with cerium(IV) (279). 

There are approximately one dozen references to azine dyes reported in Chemicaly hstracts traceable literature since 1976. Of these references, all but one refers to titration indicators. One basic dye is reported, but it is not a commercial product (6) ... 

There have been approximately 80 references to oxazine dyes in the past 15 years. Several are references to their use as laser dyes and titration indicators. Thirty of these references are to oxazine dyes for either acryUc fibers or leather (qv) (7) (see Fibers, acrylic). 

There have been approximately 60 references to thiazine dyes in the past 15 years of Chemical Jibstracts. Although most of these references are to titration indicators, photophysical evaluation, and spectral properties, a few refer to stmctures for use as dyes (13). 

The checkers purchased [(COD)RuCl2]n from Fluka (purum quality), BINAP from Aldrich (97 %), and toluene (HPLC grade) and triethylamine (reagent grade) from Fisher Scientific the latter was distilled from CaH2 under Ar prior to use. The submitters dried toluene and triethylamine over 4 A molecular sieves. Karl-Fischer titration indicated <200 pg/mL water. 

EPR redox titrations indicate heterogeneity in the [PeaS4] center. 

Kimura and co-workers have synthesized a series of alkoxide complexes with the alcohol functionality as a pendent arm.447 674 737 A zinc complex of l-(4-bromophenacyl)-l, 4,7,10-tetraaza-cyclododecane was also synthesized by the same workers to mimic the active site of class II aldolases. The X-ray structure shows a six-coordinate zinc center with five donors from the ligand and a water molecule bound. The ketone is bound with a Zn—O distance of 2.159(3) A (Figure 12). Potentiometric titration indicated formation of a mixture of the hydroxide and the enolate. Enolate formation was also independently carried out by reaction with sodium methoxide, allowing full characterization.738... 

From these observations it was concluded that the major products of the reduction of niobium(V) chloride with anhydrous pyridine were tetrachlorodi-(pyridine)niobium(IV) and l-(4-pyridyl)pyridinium dichloride. Oxidation-reduction titrations indicated that this reduction accounted for approximately 70% of the reaction products. In view of the rapid reaction of tantalum(V) halides with pyridine to form 1 to 1 adducts, it was assumed that the remaining 30% of niobium (V) which was not reduced was present in the reaction mixture as pentachloro(pyridine)niobium(V). On this basis the following over-all reaction is proposed ... 

Similarly, it was concluded that in the reduction reaction of niobium(V) bromide with pyridine the major products were tetrabromodi (pyridine )niobium-(IV), pyridinium bromide, and l-(4-pyridyl) pyridinium bromide. Oxidation-reduction titrations indicated approximately 90% reduction. The remaining 10% of niobium was assumed to be present as pentabromo(pyridine)niobium(V). The over-all reaction was indicated to be ... 

The so-called Ling oxalate titration indicates that CCP consists of 80% Ca3(P04)2 and 20% CaHP04, with an overall Ca P ratio of 1.4 1 (Pyne, 1962). However, the oxalate titration procedure has been criticized because many of the assumptions made are not reliable. Pyne and McGann (1960) developed a new technique to study the composition of CCP. Milk was acidified to about pH 4.9 at 2°C, followed by exhaustive dialysis of the acidified milk against a large excess of bulk milk this procedure restored the acidified milk to normality in all respects except that CCP was not reformed. Analysis of milk and CCP-free milk (assumed to differ from milk only in respect of CCP) showed that the ratio of Ca P in CCP was 1.7 1. The difference between this value and that obtained by the oxalate titration (i.e. 1.4 1) was attributed to the presence of citrate in the CCP complex, which is not measured by the oxalate method. Pyne and McGann (1960) suggested that CCP has an apatite structure with the formula ... 

As in acid-base titrations, indicators and electrodes are commonly used to find the end point of a redox titration. 

Oxazine, azine and thiazine dyes are named for the characteristic heterocyclic ring systems 1,4-oxazine, 1,4-diazine, and 1,4-thiazine. The dyes are generally cationic (basic) or acid dyes. They also can be reduced to colorless forms, then oxidized back to the dye, as in vat dyeing. The dyes also have been used to a limited extent in disperse and fiber reactive applications. They are used as titration indicators and may be applied to acrylic fibers and leather. 

Thus, the results of above analyses of aqueous reaction products and salts extracted by hydroxide titration indicate the presence of N202, N02 and NO3 anions in the reaction products. The latter anion can also be obtained in another reaction [173,174] ... 

Viswanathan et al. introduced carbanions onto SWCNT surfaces by treating the tubes with sec-butyllithium, providing initiating sites for the polymerization of styrene [182]. Recently, Chen et al. reported that on treating SWCNTs with sec-butyllithium and reacting the carbanions formed with C02 under oxygen-free and anhydrous conditions, the SWCNTs were alkylated and carboxylated [183] (Scheme 1.30). The so-derivatized SWCNTs could be dispersed in water to give a nearly transparent solution of 0.5 mg mL4 zeta potentiometric titrations indicated a feature similar to a zwitterionic polyelectrolyte [183]. 

Dimethyl tellurium dibromide and boron tribromide formed a thermally unstable 2 1 adduct4. Calorimetric titrations indicated that 1 1 complexes are formed between diphenyl tellurium dihalides and aluminum tribromide or gallium trichloride5 6. 

Four luminescent cyclometallated iridium(III) diimine complexes [Ir(ppy-spacer-biotin)2(NAN)]+ (NAN = Me4-phen, Ph2-phen) (38), each containing two biotin units, have been synthesised and characterised by Lo and co-workers [79], Photoexcitation of these iridium(III) diimine bis(biotin) complexes in fluid solutions at 298 K and in alcohol glass at 77 K results in intense and long-lived 3MLCT (djr(Ir) — ti (NaN))/3IL (ir —> ji ) (Me4-phen) emission. HABA assays and emission titrations indicate that the two biotin moieties of each complex are functional. RET-based emission-quenching experiments, microscopy studies using avidin-conjugated microspheres, and HPLC analysis all reveal that the complexes with a... 

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