Titrimetric microdetermination of solochrome black T: Ceric sulfate as oxidizing agent

Solochrome black T has been quantitatively determined in micro amounts by oxidizing with ceric sulfate in highly acidic medium. The reaction between solochrome black T and ceric sulfate is completed at 16 equivalence resulting in the formation of p-nitrophthalic acid and 1,2-dihydroxy naphthalene as main oxidation products. Maximum error in these experiments has been observed as 1.6%. The method is accurate, gives reproducible results, and is less time consuming.     

Effect of amines on the ceric ion-initiated polymerization of vinyl monomers. I. Polymerization of acrylonitrile by ceric ion–triethylamine catalyst system

The polymerization of acrylonitrile was studied in aqueous solution with ceric ammonium sulfate in the presence of triethylamine as initiator at 30, 40, and 50°C. The rate of polymerization was found to be linear with the concentration of the amine and independent of ceric ion concentration. A reaction scheme involving initial complex formation between ceric ion and the amine and subsequent disproportionation of the conplex to produce free radicals is proposed for the initiation reaction. The termination step is postulated as involving oxidation of the polymer chains by ceric ions. The results have been explained in the light of the proposed reaction scheme.     

The use of redox reactions in the analysis of dyes and dye industry intermediates: III. An indirect determination of brilliant green with ceric sulfate

The stoichiometry of the reaction of brilliant green with ceric sulfate was studied. An indirect determination of brilliant green based on its oxidation with excess ceric sulfate and the ascorbinometric or spectrophotometric determination of the diphenoquinone-(4,4′)-bis(diethylimine) produced has been developed.     

Polymerization of acrylamide with ceric ion–malic acid redox pair

The polymerization of acrylamide (M) in aqueous sulfuric acid medium initiated with ceric ammonium sulfate–malic acid redox pair was investigated at 35 ± 0.2°C under nitrogen atmosphere. The initiation was caused by the free radical generated by the decomposition of the complex formed between ceric ion and malic acid (MA). The rate of monomer disappearance was proportional to the first power of malic acid, ceric ion, and monomer concentrations at lower ceric ion concentrations. However, at higher ceric ion concentrations the rate was independent of [Ce(IV)]. The rate of ceric ion disappearance was proportional to [MA] and [Ce(IV)] but independent of [M] at lower ceric ion concentrations. The activation energy was found to be 57.74 kJ/mol. Sulfuric acid retarded the reaction. Molecular weights increased with increasing [M] and decreasing [Ce(IV)].     

Mode of initiation in ceric salt initiated aqueous polymerization of methylmethacrylate

Summary The basic reaction for the production of initiating radicals in Ceric salt initiated polymerization of methylmethacrylate is strongly dependent on the acidity of the medium and independent of the nature of the anion associated' with the ceric ion. In moderately acid medium the primary reaction is the formation of hydroxyl radicals by ceric ion oxidation of water. When ceric sulfate is used as the initiator these hydroxyl radicals initiate the polymerization and appear as hydroxyl endgroups in the polymers. On the other hand, when ammonium ions are present, as in case of ceric ammonium sulfate initiator or ceric sulfate initiator in the presence of ammonium sulfate, some of the hydroxyl radicals generated in the primary reaction, react with the ammonium ions producing ammonium radicals and both hydroxyl and ammonium radicals act as the initiator giving rise to both hydroxyl and amine endgroups in the polymers. In strongly acid medium the basic initiating reaction changes into one in which the monomer transfers an electron to the ceric ion producing monomer radicals which initiate the polymerization and polymers with no endgroups are formed.

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Zusammenfassung Die Grundreaktion zur Erzeugung von Startradikalen aus Cersalz-initiierter Polymerisation von Methylmethacrylat ist von der Aciditäat des Mediums stark abhängig und unabhängig von der Natur des Anions, das mit den Cerionen assoziiert ist. Im mäßig sauren Medium besteht die primäre Reaktion in der Bildung von Hydroxylradikalen durch das Cerion auf Basis der Oxidation von Wasser. Wenn Cersulfat als Initiator verwendet wird, starten die Hydroxylradikale die Polymerisation und erscheinen als Kettenendgruppen. Andererseits, bei Gegenwart von Ammonium, wie im Falle des Cerammoniumsulfats oder Cersulfats in Gegenwart von Ammoniumsulfat, reagieren einige der Hydroxylradikale in primärer Reaktion mit den Ammoniumionen und erzeugen Ammoniumradikale, und darn geben beide-Hydroxyl-und Ammoniumradikale - als Initiatoren Anlaß für Hydroxyl-und Aminendgruppen der Hydroxylketten. In stark saurem Medium verändert sich die Startreaktion in eine andere, in der Monomere ein Elektron an das Cerion transferieren und hierdurch Monomerradikale erzeugen, die die Polymerisation starten und Polymere ohne Endgruppen bilden.

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With 5 tables     

Kinetics and mechanism of the oxidation of a ferrous complex with an α,α′-diimine chelate ligand by ceric sulfate in aqueous acidic medium by UV-vis absorption spectroscopy

Kinetics of the oxidation of tris(2,2′-bipyridine)iron(II) sulfate by ceric sulfate was spectrophotometrically studied in an aqueous sulfuric acid medium. Different methods, including isolation, integration and half-life, were employed to determine the reaction order. The redox reaction was found to be first-order with respect to the reductant, tris(2,2′-bipyridine)iron(II) sulfate, and the oxidant, ceric sulfate. Complex kinetics was observed with an increase in the initial concentration of the oxidant. The influence of the dielectric constant, [H⁺] and [SO₄ ^2-] on the rate was also investigated. The increase in the dielectric constant and H⁺ ion concentration of the medium retard the rate, while an increase in the SO₄ ^2- ion concentration first accelerates the rate, and then retards the reaction. The effect of each factor, i.e., the dielectric constant, H⁺ ions and SO₄ ^2- ions, suggests that Ce(SO₄)₃ ^2- is the active species of cerium(IV). A rate law consistent with the observed kinetic data and the proposed mechanism is suggested to be: {fx631-1     

Polymerization of acrylonitrile initiated by ceric ion–citric acid redox system

Heterogeneous polymerization of acrylonitrile initiated by ceric ammonium sulfate–citric acid (C.A.) redox system is reported at 35 ± 0.2°C under nitrogen atmosphere. The rate of monomer disappearance is found to be proportional to [C.A.]⁰, [Ce⁴⁺]^0.63, and [Monomer]^1.59. The rate of ceric ion disappearance is directly proportional to ceric ion concentration but independent of monomer concentration. The initial rate was independent of [H₂SO₄]. The molecular weight of polyacrylonitrile increases with increasing monomer concentration and decreasing ceric ion concentration. Activation energy was found to be 27.9 kJ/mol.     

Polymerization of Acrylonitrile with Ceric lon-2-Propanethiol as Initiator System

The kinetics of the polymerization of arylonitrile with ceric ammonium sulfate in the presence of 2-propanethiol as the redox initiator system in aqueous solution has been investigated. The rate of polymerization was found to be proportional to the square root of both ceric ion and thiol concentrations, and the monomer exponent was close to 1.5. Spectral studies indicated that there is a complex formation between ceric ion and the monomer acrylonitrile. A kinetic scheme, based on initial formation of this complex and its subsequent reaction with the thiol to produce the free radicals (RS.) responsible for initiation has been postulated to account for the observed results. The activation energy and different kinetic and transfer constants for the system have also been evaluated.     

Titrimetric microdetermination of chromotrope 2R: Ceric sulfate as oxidizing agent

Chromotrope 2R has been quantitatively determined in micro amounts by oxidizing with ceric sulfate in highly acidic medium. The reaction is completed at 40 equivalence; and the rupture of the molecule results in the formation of formic acid as the main oxidation product. Maximum error observed is 1.0%. The method is simple, accurate, and reproducible.     

硫酸铈中铈的价态及其温度依赖性的XPS研究

近年来人们对混合价化合物的研究十分关注,已发现的这类化合物主要是稀土元素的金属化合物。最近笔者在研究稀土化合物的电子能谱时观察到,固态硫酸铈(Ⅳ)也是一种混合价化合物(或称波动价化合物),而且铈的价态与温度有关,还发现硫酸缔的热分解行径与文献报道有很大出入。     

Chemiluminescence determination of ferulic acid by flow-injection analysis using cerium(IV) sensitized by rhodamine 6G

A simple, sensitive and rapid flow-injection chemiluminescence method has been developed for the determination of ferulic acid based on the chemiluminescence reaction of ferulic acid with rhodamine 6G and ceric sulfate in sulphuric acid medium. Strong chemiluminescence signal was observed when ferulic acid was injected into the acidic ceric sulfate solution in a flow-cell. The present method allowed the determination of ferulic acid in the concentration range of 8.0x10(-6) to 1.0x10(-4)moll(-1) and the detection limit for ferulic acid was 8.7x10(-9)moll(-1). The relative standard deviation was 2.4% for 10 replicate analyses of 1.0x10(-5)moll(-1) ferulic acid. The proposed method was applied to the determination of ferulic acid in Taita Beauty Essence samples with satisfactory results.     

Determination of the valence distribution of vanadium in polyolefin catalysts prepared from vanadium trichloride

An electrochemical method has been developed for determining the relative amounts of V(II) and V(III) in polyolefin catalysts prepared using aluminum alkyls and vanadium trichloride. The catalyst, usually obtained as a slurry in n-heptane, is titrated potentiometrically with ceric sulfate using a platinum indicator electrode. Under proper experimental conditions, 2 breaks are obtained, corresponding to the reactions V(II) →V(III) + e and V(III) →V(IV) + e. Interferences from other components of the catalyst are negligible. The method is useful for the analysis of both laboratory catalysts and grab samples taken from pilot plant reactors.     

硫酸铈(Ⅳ)催化合成丁酸丁酯

丁酸丁酯被广泛应用于食品、医药、烟草、日用化学工业 ,目前工业生产方法以浓硫酸催化丁酸和丁醇反应为主[1] 。由于浓硫酸的脱水、氧化作用 ,使得产物色泽深 ,产率低 ;而且硫酸易腐蚀设备 ,产品后处理产生的酸性废水严重污染环境。因此人们在努力寻找浓硫酸催化法的替代方法。用对甲苯磺酸、杂多酸为催化剂[2 4 ] 对合成丁酸丁酯具有很好的催化效果 ,但存在反应时间长、原料用量大等问题。本文以结晶硫酸高铈为催化剂合成了丁酸丁酯。1　实验部分1 .1　仪器与试剂岛津ＧＣ 1 6Ａ气相色谱仪 ,ＦＴＳ 2 1 0 0型红外光谱仪(美国Ｂｉｏ Ｒａ…     

The use of naphthalene derivatives in inorganic analysis : The nitronaphthylamines as new reagents for mercuric mercury and ceric cerium

The use of 4-nitro-1-naphthylamme as a spot test for mercuric mercury and 1-nitro-2-naph-thylamine as a specific spot test for ceric cerium have been observed In each case, the reactions appear to be suitable for general qualitative inorganic analysis The ceric cerium test was specific whereas in the case of mercuric mercury. Ce⁺⁴ was the only on of 51 tested which interfered.     

Determination of iodine in common salt by an automatic reaction-rate method

An automatic reaction-rate method is described for the ultramicro determination of iodine in common salt. The method utilizes the acceleration of the reaction between ceric sulfate and arsenious acid by iodine. The time required for the reaction to consume a fixed amount of ceric ions is measured automatically and related directly to the iodine concentration. Measurements btained in salt samples containing 3 to 7500 μg of iodine per 100g were precise to within 2% or 0.3 μg of iodine, whichever is larger. Measurement times varied from a few sec to about 2min.     

Redox substoichiometric determination of arsenic in biological materials by neutron activation analysis

A redox substoichiometry is proposed for an accurate and precise determination of arsenic. This method is based on the substoichiometric oxidation of trivalent arsenic to pentavalent with potassium bromate or ceric sulfate followed by the separation of these species by thionalide extraction of trivalent arsenic. It was applied to neutron activation analysis of arsenic in the NBS SRM Orchard Leaves and the Shark Powder. The results were obtained with an excellent accuracy and precision.     

Graft copolymerization of cellulose initiated by ceric salts: Effect of reaction conditions on the consumption of ceric ion

A soluble monomer [methyl acrylate (MA)] and an insoluble monomer [butyl methacrylate (BMA)] were grafted onto cellulose by three types of ceric salts under both oxygen-free conditions and in the presence of oxygen. For comparison, Ce(IV) consumption during cellulose oxidation was also determined under similar reaction conditions. Slightly more Ce(IV) was consumed during cellulose oxidation in the presence of oxygen. During graft copolymerization of MA under oxygen-free conditions, the consumption of Ce(IV) was much lower than during cellulose oxidation regardless of the type of ceric salt employed. The opposite was observed in the presence of oxygen: much more Ce(IV) was consumed during grafting than during cellulose oxidation. The consumption of Ce(IV) in the graft copolymerization of BMA by ceric sulfate was nearly independent of reaction conditions and it was approximately the same as in cellulose oxidation. In the reaction initiated by ceric ammonium nitrate under oxygen-free conditions, less Ce(IV) was once again used up during grafting than during cellulose oxidation. However, the difference was much smaller than in the case of MA.     

Vinyl polymerization initiated by ceric ion reducing agent systems in sulfuric acid medium

Polymerization of the monomers, methyl acrylate (MA) and methyl methacrylate (MMA) was carried out in sulfuric acid medium at 15°C. With the redox initiator system, ceric ammonium sulfate–malonic acid. There was no induction period, and a steady state was attained in a short time. There was found to be no polymerization even after 1 hr. in the absence of the reducing agent R. The initiation was by the radical produced from the Ce⁴⁺–malonic acid reaction. The rate of monomer disappearance was proportional to [M]^1.5, [R]^0.5, and [Ce⁴⁺]^0.3–0.5, and the rate of ceric disappearance was directly proportional to [R] and [Ce⁴⁺]. Chain lengths of the polymers were directly proportional to [M] and inversely to [R]^1/2 and [Ce⁴⁺]^1/2. The experimental results were explained by a kinetic scheme involving the following steps: (a) oxidation of the substrate to give the primary radical which reacts with Ce⁴⁺ to give the products, (b) initiation by the primary radical, (c) propagation, and (d) termination of the growing polymer radicals by the mutual type. For the polymerization of acrylonitrile (AN) by the redox system, ceric ammonium sulfate–cyclohexanone (CH), in sulfuric acid at 15°C., the scheme was modified to include linear type of termination by Ce⁴⁺, along with the mutual termination to explain the results especially under conditions with [Ce⁴⁺] ≥ [CH].     

Effect of amines on the ceric ion-initiated polymerization of vinyl monomers. II. Polymerization of acrylonitrile by ceric ion in presence of various substituted amines

The effect of various substituted amines on the polymerization of acrylonitrile initiated by ceric ammonium sulfate has been studied in aqueous solution at 30°C. It was found that the secondary and tertiary amines considerably increased the rate of polymerization, whereas the primary amines seemed to have no effect at all. From the kinetic studies it was found that the overall polymerization rate R_p is independent of ceric ion concentration and can be expressed by the equation: R_p = k₁ [amine] [monomer] + k₂[monomer]², where k₁ and k₂ are constants (involving different rate constants). The accelerating effect of the amines was attributed to a redox reaction between the ceric ion and the amine involving a single electron transfer, the relative activity of the different amines being thus dependent on the relative electron-donating tendency of the substituents present in the amine. The mechanism of the polymerization is discussed on the basis of these results, and various kinetic constants are evaluated.     

A flow injection biosensor system for highly sensitive detection of 2,4,6-trichlorophenol based on preoxidation by ceric sulfate.

A flow injection biosensor system was proposed for the highly sensitive detection of 2,4,6-trichlorophenol (2,4,6-TCP). The system is based on the preoxidation by ceric sulfate to the corresponding benzoquinone (2,6-dichloro-1,4-benzoquinone: 2,6-DC-1,4-BQ), which was characterized using cyclic voltammetry, hydrodynamic voltammetry, and UV-vis spectrophotometry. The laccase-based biosensor used in this analytical system responded sensitively to 2,4,6-TCP after the preoxidation by ceric sulfate. The response could be based on the bioelectrocatalytic recycling of oxidation product (2,6-DC-1,4-BQ) between laccase membrane and the electrode, because the oxidation product (2,6-DC-1,4-BQ) of 2,4,6-TCP was an electrochemically reversible redox species. The signal current was linearly related to the 2,4,6-TCP concentrations in a dynamic range of 2 nM - 2 microM; the slope and the y-intercept of the straight line were 1150 nA microM(-1) and 0.88 nA, respectively. The detection limit was 1.2 nM (S/N = 3) for a 20 microl injection. Among a variety of chlorophenols and some phenolic compounds, the only interferent was 2,4-dichlorophenol.