Direct reading thermometric analysis

According to the direct reading thermometric method the concentration of the component to be determined is established from the temperature variation of the sample solution obtained on adding to it an excess of a reagent which reacts selectively with the respective component. Under suitably chosen experimental conditions the concentration of the respective component is determined from a single measured value. Since the established measurement technique requires little manual work and the respective components may be determined from the sample solution directly without any separations, the method in its present form is chiefly suitable for rapid serial analyses.

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Zusammenfassung Bei der thermometrischen Methode mit Direktablesung wird die Konzentration der gesuchten Komponente aus der Temperaturänderung der Probelösung bestimmt, die nach Zugabe eines Überschusses von einem selektiv reagierenden Reagens wahrnehmbar ist.Unter geeigneten Versuchsbedingungen kann man die Konzentration der gesuchten Komponente aus einem einzigen Meßwert, nämlich der Temperaturänderung der Probelösung bestimmen. Da die ausgearbeitete Meßtechnologie wenig Arbeit erfordert und die gesuchten Komponenten ohne jede Trennung direkt bestimmt werden können, ist die Methode in ihrer jetzigen Ausführungsart hauptsächlich zu betriebsmäßigen Serien-Schnellanalysen geeignet.

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Résumé Selon la méthode thermométrique à lecture directe, on détermine la concentration du constituant cherché d'après la variation de température de la solution échantillon que l'on additionne d'un excès de réactif sélectif de celui-ci. Dans les conditions expérimentales appropriées, une seule mesure suffit pour déterminer la concentration du constituant cherché. Comme la technique de mesure qui a été mise au point demande peu de travail et comme on peut doser sans aucune séparation les constituants étudiés, la méthode dans sa forme actuelle se prête en premier lieu aux dosages en séries industriels.

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, , . . . , . .

     

Investigation of Harmattan particulates from Kano and Ife, Nigeria

The size distribution, elemental composition, shape and surface texture of harmattan particulates of distinctly located points have been examined. The characterized particle size ranges are 0.7–16.4 m and 0.6–19.7 m for Kano and Ife, respectively. A total of 12 elements (Al, Si, P, S, Cl, K, Ca, Mn, Ti, Fe, Cu, and Zn) were detected with varying degrees of concentration. The plotted element concentration curves favored micron and submicron particle diameters. The particle shapes exhibit high/low sphericity. The plotted size distribution curves exhibited a marked downward shift in particle diameter from Kano to Ife.     

m-Xylene isomerization/disproportionation selectivity over dealuminated Y zeolite

The conversion of m-xylene over dealuminated zeolite Y with different sodium exchange level has been studied. It has been established that m-xylene isomerization/disproportination selectivity depends on the concentration of the acid centers in the aluminium-deficient faujasite.

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- Y - . - /qd .

     

Catalytic oxidation of carbon monoxide by oxygen and nitrogen oxides on a copper-chromium oxide catalyst

The kinetics of CO oxidation by O₂, NO and NO₂ has been studied on a Cu–Cr-oxide catalyst. A comparison with the kinetics of the CO–N₂O interaction has been made. In all cases the reaction rate is described by the equation:r=k p _CO ¹ P _0x ⁰ . The oxidation of CO has been studied in the presence of different oxidants in the reaction mixture.

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CO , . CO . CO . CO .

     

Catalytic activity of palladium-containing zeolites in the complete oxidation of benzene

The dependence of palladium distribution in zeolites on the temperature of thermal treatment has been established from the data on oxygen chemisorption and the statistical processing of electron micrographs. The influence of palladium distribution in zeolites on their catalytic activity towards the complete oxidation of benzene has been shown.

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- . .

     

Flow injection flame atomic spectrometric determination of iron, calcium, magnesium, sodium and potassium in ceramic materials by using a variable-volume injector

Summary A series of different ceramic materials, such as porcelain, feldspar, kaolin, varnish, clay and stoneware have been analyzed. Iron, calcium and magnesium have been determined in these materials by flame atomic absorption and sodium and potassium by flame emission. The use of a variable-volume injector enables one to carry out these analyses in a flow system (after fusion of samples with lithium metaborate) and does not require different dilutions for the determination of each type of sample considered, nor the use of different flow injection manifolds. The developed procedure provides a limit of detection of 100 g/l for Na, 70 g/l for Ca, 50 g/l for both Fe and K and 8 g/l for Mg. The coefficient of variation obtained for the absorbance measurement is of the order of 0.5–2%. A series of 17 real samples were analyzed by the proposed procedure and the obtained results turned out to be comparable to those found by batch analysis.     

Decomposition of hydrogen molybdenum bronze, H0.30MoO3, upon increasing temperature in various gases

When H_0.30MoO₃ was heated at increasing temperature in H₂, N₂, H₂O, and in vacuum, the total weight loss just corresponded to the weight of 0.15 H₂O in H_0.30MoO₃. On the other hand, when the bronze was heated in CH₃OH vapor, one of the lattice oxygens was removed and the bronze was partly reduced to MoO₂.

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H_0,30MoO₃ H₂, N₂, H₂O , 0,15H₂O H_0,30MoO₃. , CH₃OH, MoO₂.

     

A differential scanning calorimetric study of some phenol derivatives

Differential scanning calorimetry has been applied to derive the fusion enthalpies and entropies of series of mono and dimethylphenols, mono and dichlorophenols, and mono and dinitrophenols.

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Zusammenfassung DSC wurde verwendet zur Ermittlung der Schmelzenthalpie und Entropie der Reihen von Mono- und Dimethylphenolen, Mono- und Dichlorphenolen, Mono- und Dinitrophenolen.

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- , - , - .

     

Some investigations on the photostabilization of polypropylene

The effect of substituted hydroxybenzophenone, benzotriazole and organic metal complexes on the photooxidation of PP films has been studied. It has been established that NiDBTC added in 1.0 wt. % is the most effective photostabilizer.While in the case of other stabilizers there is a slight increase in the Co content even during the induction period, with the application of NiDBTC practically no oxidation can be observed before the stabilizer completely disappears. This means that NiDBTC inhibits the photooxidation of the polymer even in low concentration.

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, - . , Ni, 1,0 . %. . , Ni , . , Ni .

     

Methode d'analyse debitmetrique appliquee a l'etude de reactions de la forme solide 1⇌solide 2+gaz,en fonction de la temperature et de la pression

Résumé Une méthode d'analyse débitmétrique à laquelle peut Être associée ATD est présentée. Elle s'applique à l'étude de réactions de la forme solide 1 solide 2+gaz dans des domaines de températures et de pressions jusqu'à 900 et 150 bar.On décrit le principe de la mesure et les conditions de fonctionnement d'un dispositif expérimental plus particulièrement mis au point pour l'étude de la décomposition thermique de CdCO₃ en atmosphère de CO₂.Cette méthode sensible et précise permet d'obtenir des résultats quantitatifs.

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An experimental device based on the measurement of gas flow rate is described, to which a DTA apparatus can be attached. The method is suited to the investigation of reactions of the type Solid₁Solid₂+gas, in the temperature interval up to 900C and at pressures up to 150 bar. The principle of the measurements is given, as well as the working conditions of an experimental device constructed specially to study the thermal decomposition of CdCO₃ in a CO₂ atmosphere.This sensitive and accurate method enables quantitative results to be obtained.

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Zusammenfassung Es wird eine Methode der Strömungsmessungs-Analyse beschrieben, an die DTA angeschlossen werden kann. Sie eignet sich zum Studium von Reaktionen des Typs: Festkörper 1 Festkörper 2 + Gas im Temperatur- und Druckbereich bis zu 900, bzw. 150 bar.Das Meßprinzip wird beschrieben, sowie die Betriebsbedingungen einer besonders zum Studium der thermischen Zersetzung von CdCO₃ in CO₂-Atmosphäre entwickelten Versuchsvorrichtung.Diese empfindliche und genaue Methode ermöglicht quantitative Ergebnisse.

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, , . = + 900 150 . , CdCO_{3 2}. , , .

     

Structure, activity and selectivity of V2O5-TiO2 catalysts for o-xylene conversion

The formation of needle shaped crystallites of V₆O₁₃ at low V concentrations on V₂O₅-anatase coated catalysts explains the low selectivity for phthalic anhydride during o-xylene oxidation. The (010) plane of V-oxide, most active for selective oxidation of o-xylene, is not accessible and the contact of this plane with the anatase faces promotes the anatase-rutile transformation and the incorporation and blocking of V⁴⁺ ions.

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V₆O₁₃ V , V₂O₅-, -. (010) , -, , - V⁺⁴.

     

Nature of extended defects of CuO

For the first time, using high-resolution electron microscopy, extended defects (twins, screw dislocations and microdistortions) of disperse CuO have been found. Their structure is described.

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CuO -, .

     

Determination of traces of iron and gallium in high-purity aluminium

Summary A procedure is described suitable for determining iron and gallium down to the levels present in 99.999% pure aluminium. Copper, cobalt, manganese, and lanthanum do not interfere. A single determination takes about two hours.The precision of the method is within 0.1g iron at the 2-g iron level and within 0.4g of gallium at the 2-g gallium level per gram of metal.

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Zusammenfassung Ein Verfahren zur Bestimmung von Bisen und Gallium in 99,999%igem Aluminium wird beschrieben. Kupfer, Kobalt, Mangan und Lanthan stören nicht. Eine Einzelbestimmung dauert ungefähr 2 Stunden. Die Genauigkeit des Verfahrens beträgt 0,1g Fe und 0,4g Ga bei Anwesenheit von 2g des betreffenden Elementes pro Gramm Metall.

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Résumé On décrit un procédé permettant le dosage du fer et du gallium jusqu'aux teneurs présentes dans l'aluminium pur à 99,999%. Le cuivre, le cobalt, le manganèse et le lanthane n'interfèrent pas. Un seul dosage demande environ 2 heures.La précision de la méthode est de 0,1g de fer pour 2g de fer présent et de 0,4g de gallium pour 2g de gallium présent par gramme de métal.

     

Thermal decompositions of some transition metal salicylates

The thermal decompositions of divalent cobalt, cadmium, nickel and copper salicylates and intermediates formed during the decomposition processes were investigated by means of thermogravimetry. Two intermediates were identified in each case, except for copper(II) salicylate.

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Zusammenfassung Die thermische Zersetzung von divalentem Kobalt-, Cadmium-, Nickel- und Kupfersalicylat und von während der Zersetzungsprozesse gebildeten Zwischenprodukten wurde thermogravimetrisch untersucht. Mit Ausnahme von Kupfer(II)-salicylat konnten in jedem Falle zwei intermediäre Produkte identifiziert werden.

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, , , , . , , .

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The authors wish to thank Perkin-Elmer for its collaboration     

Conductance of iron(III) laurate solutions in binary liquid mixtures

Summary The specific conductivity of iron(III) laurate solutions in binary liquid mixtures shows that the soap aggregates into micelles and CMC is found to be independent of temperature and concentration of benzene, acetone and tetrachloromethane in 1-butanol. The variation of molecular conductance,, with soap concentration, C, is expressed by the equation: = 10^AC^B. Both constants A and B vary with solvent composition but B remains constant with increase in temperature. Several parameters such as molecular conductance at infinite dilution, , dissociation constant, K, heat of dissociation, H, entropy, S and free energy, G of dissociation of soap have been evaluated and the effect of the nature of solvents has been discussed.     

DTA determination of the anhydrite content in rock salts

The DTA method was used to determine the phase diagram of the NaCl-CaSO₄ system over the range 0.55 wt.% of CaSO₄ in air atmosphere. The effects of SiO₂, CaCO₃ and Fe₂O₃ on the melting temperatures of pure NaCl and the eutectic were determined. On the basis of the above temperatures, a method of quantitative determination of the anhydrite content in rock salts has been developed.

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Zusammenfassung DTA wurde benutzt, um in Luft im Bereich 0 bis 55,0 Gew.% CaSO₄ das Phasendiagramm des Systemes NaCl-CaSO₄ zu bestimmen. Es wurde auch der Einfluß von SiO₂, CaCO₃ und Fe₂O₃ auf die Schmelztemperatur von reinem NaCl bzw. des Eutektikums bestimmt. Auf der Grundlage obiger Temperaturen wurde eine Methode zur quantitativen Bestimmung des Anhydritgehaltes in Steinsalzen entwickelt.

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- 0–55,0 . , . , ( ) .

     

Role of high temperature hydrogen treatment in n-hexane aromatization over Pt/Al2O3 catalyst. Temperature programmed reaction study

Ultrazet zeolites (Polish counterparts of the ZSM-5 zeolite) with SiO₂/Al₂O₃ ratios ranging from 40 to 186, have been studied to elucidate the correlation of SiO₂/Al₂O₃ ratio with transformation of the orthorhombic into monoclinic symmetry in the zeolite (during preparation), cracking reaction of n-hexane and 3-methylpentane and zeolite acidity.

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( ZSM-5) SiO₂/Al₂O₃ 40 186 SiO₂/Al₂O₃ ( ), - - .

     

Carbon monoxide hydrocondensation on iron catalysts prepared from metal carbonyl compounds

The iron/alumina catalysts prepared by the impregnation of Fe(CO)₅ on the support have properties quite different from those of the conventional catalysts in the CO+H₂ reaction. However, the preparation procedure or the activation of the solid has a decisive effect on the activity, selectivity and stability.

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Fe(CO)₅ , , CO+H₂. , , .

     

Kinetics of ligand exchange of aminoacid anions in the ternary complexes of copper(II) and hydroxyethyldenediphosphonic acid

The kinetics of the chemical exchange of some aminoacid anions in ternary complexes of copper(II) and hydroxyethylidenediphosphonic acid has been studied by a nuclear magnetic relaxation method. Rate constants of the chemical exchange have been determined and some suggestions concerning the structure of the complexes have been made.

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(II) . .

     

Equilibrium Particle Distribution in the Disperse System with Coagulation and Aggregate Disintegration

Kinetic equations were formulated, which describe coagulation–fragmentation process in a low concentrated suspension flow at a low shear rate. In such a system dispersed phase divided into fine and coarse fractions as the system is brought to equilibrium. Kinetic equations of two-fraction model were formulated. An approximate solution and, in one particular case, the exact solution of these equations were obtained for the equilibrium state. Detailed analysis of equilibrium particle distribution over the mass m was performed for an exponential coagulation kernel = ₀ m and an degenerated disintegration kernel = ₁₂, in which the disintegration frequency is an exponential function of aggregate mass ₁ = ₀ m ⁺ , and the probability of the fragment detachment from an aggregate is independent ofm and decreases exponentially with an increase in mass of a fragment: ₂ = ₀ ^–1exp(–/₀). The equilibrium distribution was shown to exist only at > 0, and in particular, it is described at = = 1 by the f() = ₀₀ ^–1exp(–/₀) and F(m) = Cx ^–1(x + 1)^{2 – 1} e ^–x functions for the particles of fine and coarse fractions (x = m/m ₀, = m ₀/₀, m ₀ and ₀ are the characteristic masses of coarse and fine fractions, respectively). The particle distribution for the fine fraction at 1 is well approximated by the Gaussian distribution exp[–(m – m ₀)²/(4^–1 m ₀₀)].