A RAPID METHOD FOR THE ESTIMATION OF SODA IN GLASSES*

A direct determination of alkali is often avoided in glass analysis because of the tedious nature of the method and the estimation by difference is not justifiable because of accumulating errors. The method proposed consists in HF-H₂SO₄ decomposition, removal of MgO and R₂O₃ by lime, conversion of sulfate to carbonates by Ba(OH)₂ and CO₂, boiling to precipitate CaCO₃ and BaCO₃, and titration of Na₂CO₃.     

Effect of different preparation methods on the microstructure and mechanical properties of Si3N4 ceramic composites

In this study, Si₃N₄ ceramic composites were fabricated by using ball-milling, titration preparation and urea preparation methods, respectively. The effect of different preparation methods on microstructure and mechanical properties of the Si₃N₄ ceramic composites was investigated. Obviously, the Si₃N₄ ceramic composite prepared by the urea preparation method (U-SN sample) showed better sintering behavior and higher mechanical properties than that prepared by the other two methods. Compared with the Si₃N₄ ceramic composite by the titration preparation method (T-SN sample), we could avoid the complex titration process or uncontrollable pH value during the preparation process of the U-SN sample. Meanwhile, the coated Y-Al precursor layer in thickness of nanometers was more homogeneous than that prepared by the traditional titration method. B-SN represented the Si₃N₄ ceramic composite prepared by the ball-milling method. These samples were all sintered from room temperature to 1750 °C via hot-pressing sintering. The U-SN specimen showed the optimal flexural strength and fracture toughness of being 817 MPa and 6.90 MPa/m², respectively, which could be attributed to its smallest grain size (0.46 µm) among these three samples.     

Effect of pH, sulfate and sodium on the EDTA titration of calcium

The ethylenediaminetetraacetic acid (EDTA) titration method limits the measurement of calcium concentration to 50 mg/l in water. However, various acids and salt solutions are used in the investigation of the durability of concrete, and the adaptability of the EDTA titration method to determine the calcium in these solutions must be investigated. Hence, the purpose of this study was to investigate the interfering effects of hydrochloric acid, sulfuric acid, sodium chloride and sodium sulfate on measuring the calcium in the aqueous leaching solutions using the EDTA titration method. The calcium standard solutions were prepared using CaCl₂ with initial pH from −0.8 to 7 and calcium concentration up to 160 mg/l. Sulfuric acid and hydrochloric acid were used to prepare calcium solutions with lower pH. Salt solutions with 3% NaCl and 3% Na₂SO₄ were used to evaluate the interfering effects of salt elements such as sulfate and sodium on the EDTA titration. Results indicated that the EDTA titration method was reliable in measuring the calcium up to 160 mg/l, the maximum concentration investigated in this study, in hydrochloric acid with pH higher than zero and 3% sodium chloride solution. Sulfuric acid with pH higher than zero and 3% sodium sulfate solutions showed 3% to 4% less calcium in the solutions. Acid solutions with pH less than zero showed interference with calcium measurement.     

DETERMINATION OF IRON OXIDE AND TITANIA IN CLAY REFRACTORIES1

Customary method of determining iron oxide and titania from ignited R₂O₂ precipitate requires considerable time. Direct titration of fusions with sodium carbonate is impossible because of gelatinous silica. Direct titration of fusions with potassium bisulphate is accurate with clays low in silica and unfired clays. By treating with hydrofluoric and sulphuric acid, and dissolving with dilute hydrochloric and precipitating the R₂O₂ by ammonium hydroxide and then fusing with potassium bisulphate the iron and titanium oxide can with accuracy be titrated. A detail method of procedure is given.     

Preparation of γ‐Fe2O3 Catalysts and their deNOx Performance: Effects of Precipitation Conditions

Magnetic γ‐Fe₂O₃ catalysts were prepared by microwave‐assisted coprecipitation utilizing the direct‐titrate and back‐titrate precipitation technique with different precipitants, namely, (NH₄)₂CO₃, NaOH, Na₂CO₃, and NH₄OH, which were evaluated in the selective catalytic reduction of NO_x with NH₃. The optimum γ‐Fe₂O₃ catalyst preparation method was direct titration with NH₄OH as the precipitant, which exhibits high deNO_x efficiency. This direct titration was effective to maintain the proper crystallization degree of γ‐Fe₂O₃, improve the pore structure, and suppress the formation of α‐Fe₂O₃ phase, being advantageous to get tiny and uniform discrete γ‐Fe₂O₃ particles with high activity in selective catalytic reduction. NH₄⁺‐based precipitants in direct titration leads to an increase of the surface O/Fe atom ratio, and more lattice oxygen sites are exposed to the crystal surface.     

Origin of the High Activity and Stability of Co3O4 in Low-temperature CO Oxidation

In this paper, the Co₃O₄ catalysts prepared by the liquid phase precipitation method were investigated with respect to their activity and stability in CO oxidation reaction. The Co₃O₄ catalysts were comparatively investigated by thermal gravimetry analysis (TG-DTG), X-ray powder diffraction (XRD), N₂ adsorption, CO titration and O₂-temperature program desorption (O₂-TPD). The results of XRD show that all the catalysts exist as a pure Co₃O₄ phase with the spinel structure. The high catalytic activity observed at ambient temperature is followed by a gradual decrease. The CO titration experiments show that the Co₃O₄ catalysts possess active oxygen species. The total amount of active oxygen species and the specific surface area decrease with increasing calcination temperature. The O₂-TPD results indicate that O ₂ ^? and O^? are the possible active oxygen species.     

Homogeneously catalyzed hydrogenation and gas-liquid chromatographic analysis of the methyl esters of cyclopropene fatty acids

Various concentrations of cyclopropene fatty acids have been determined down to 0.2% by the use of gas liquid chromatographic (GLC) analysis of the methyl esters of fatty acids that have been quantitatively hydrogenated using a homogeneous transition metal complex catalyst. The effectiveness of the use of bromotris(triphenylphosphine)-rhodium(I), Br(P(C₆H₅)₃)₃Rh, as a homogeneous hydrogenation catalyst to convert the cyclopropene ring to a cyclopropane ring has been evaluated and compared with the analogous chloro- and iodo-complexes. The hydrogenation/GLC method of analysis has been compared with the method of titration with hydrogen bromide in benzene and with the method involving the use of high resolution nuclear magnetic resonance (NMR).     

Analysis of commercial anhydrous tetrasodium pyrophosphate

A titration method of analysis is given for Na₄P₂O₇ in commercial anhydrous tetrasodium pyrophosphate using a modification of the Britske and Dragunov titration method. In the absence of other polyphosphates, a degree of precision is obtained satisfactory for the type of product supplied by the manufacturers. Time required for analysis is much less than for methods relying upon precipitation with subsequent gravimetric treatment. Results of cooperative work are given. During 1939 Committee D-12 on Soaps and Other Detergents of A. S. T. M. formulated specifications for tetrasodium pyrophosphate (anhydrous) which now appear as their specification D 595-42 T. The subcommittee on Analysis of Special Detergents was asked to provide a method of analysis of reasonable accuracy for use on commercial material containing about 95 to 100% Na₄P₂O₇. A search of the literature suggested several possible methods (1,2,3) and various modifications supplied by interested laboratories were considered. Cooperative work was carried out by ten laboratories with the result that the following modification of the Britske and Dragunov method (2) was adopted as a Tentative Standard of the A. S. T. M. (4) in 1941 and has just recently been advanced to Standard. The procedure describes an indirect determination of tetrasodium pyrophosphate by titration of the sulfuric acid liberated by the action of zinc sulfate on an acid pyrophosphate in accordance with the following reactions:

$$\begin{gathered} Na_4 P_2 O_7 + 2HCl = Na_2 H_2 P_2 O_7 + 2NaCl \hfill \\ Na_2 H_2 P_2 O_7 + 2ZnSO_4 = Zn_2 P_2 O_7 + Na_2 SO_4 + \hfill \\ H_2 SO_4 \hfill \\ \end{gathered}$$     

Characterization of Acid Catalysts by Thermometric Titration

Thermometric titration as a method suitable for the characterization of the acidity of catalysts is presented. The determination of the acid strength, the end point of titration and the total heat of neutralization by thermometric titration is tested using samples of benzoic acid, zeolite NaHY and unsupported and supported (TiO₂, SiO₂, SiO₂· Al₂O₃) tungstosilicic acid. The determination of the end point of titration acidity is discussed. The method is recommended for the determination of the total neutralization enthalpy as well as the enthalpy of the neutralization of the strongest acid centers in solid catalysts.     

Preparation and catalytic performance of Co3O4 catalysts for low-temperature CO oxidation

Without use of any surfactant or oxidant, a series of Co₃O₄ catalysts have been prepared from cobalt nitrate aqueous solution via a very simple liquid-precipitation method with ammonium acid carbonate followed by calcination at various temperatures. The catalytic performance of the Co₃O₄ for CO oxidation has been studied with a continuous flowing laboratory microreactor system. The results show that the CO conversion of all the samples can reach 100% at ambient temperature. The catalyst calcined at 300 °C is able to maintain its activity for CO complete oxidation more than 500 min at 25 °C and about 240 min even at −78 °C. High reaction temperature results in a high catalytic stability, while the catalytic stability decreases with further increasing the reaction temperature. Characterizations with X-ray powder diffraction and transmission electron microscopy suggest that all the samples exist as a pure Co₃O₄ phase with the spinel structure, the samples are apt to aggregate and the specific surface area gradually decreases with increasing the calcination temperature, which directly leads to the decrease of catalytic stability. Furthermore, the amount of active oxygen species measured by CO titration experiments appears to be critical for catalytic performance.     

Metal (Co,Mn)-amine-functionalized mesoporous silica SBA-15: synthesis,characterization and catalytic properties in hydroxylation of benzene

Mesoporous silica SBA-15 was synthesized using H₃PO₄ and functionalized with ethylendiaminopropyltrimethoxysilane (H₂N–(CH₂)₂–NH–(CH₂)₃–) by grafting method. A variety of transition metals such as Co and Mn have been coordinated with amine-functionalized silica SBA-15. The materials have been characterized by XRD, FT-IR, BET, TGA, ¹³C-NMR, DR UV–Vis, atomic absorption spectroscopy (AAS) and back titration using NaOH (0.1 N). The catalytic performance of obtained catalyst was determined for hydroxylation of benzene using H₂O₂ as oxidant in the presence of O₂ atmosphere. At optimized conditions, the Mn-amine-functionlized mesoporous silica SBA-15 exhibited high catalytic activity at room temperature in the absence of solvent.     

Effect of precipitants during the preparation of Cu-ZnO-Al2O3/Zr-ferrierite catalyst on the DME synthesis from syngas

The synthesis of dimethyl ether (DME) from biomass-derived model synthesis gas has been investigated on Cu-ZnO-Al₂O₃/Zr-ferrierite bifunctional catalysts. The catalysts are prepared by co-precipitation–impregnation method using Na₂CO₃, K₂CO₃ and (NH₄)₂CO₃ as the precipitants. The catalytic activity tests reveal that the best yield of DME can be obtained on the catalyst precipitated by using (NH₄)₂CO₃. Detailed characterization studies conducted on the catalysts to measure their properties such as surface area, acidity by temperature-programmed desorption of ammonia (NH₃-TPD), reducibility of Cu oxide by temperature-programmed reduction (TPR), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and copper surface area and particle size measurements by N₂O titration method. Increasing the number of moderate acidic sites and facilitation of easily reducible copper species with small particle size are found to be the prime reasons for the superior functionality of the (NH₄)₂CO₃ precipitated catalyst. The usage of (NH₄)₂CO₃ also leaves no residual ions, whereas the presence of residual K⁺ and Na⁺ ions in the case of K₂CO₃ and Na₂CO₃ precipitated catalysts leads to lower activity and selectivity.     

Standardization of the Boehm titration. Part I. CO2 expulsion and endpoint determination

The various steps required in the Boehm titration (CO₂ removal, agitation method, endpoint determination, etc.) are carried out in different ways by different research groups, making a comparison of the results between these groups difficult. Herein, the methods of CO₂ expulsion and endpoint determination for the Boehm titration were standardized. Blank samples of the three Boehm reaction bases, NaHCO₃, Na₂CO₃ and NaOH, were examined for complete CO₂ expulsion through sparging with an inert gas (N₂ or Ar), heating, or utilizing a N₂-filled glove box. Boehm titrations using NaOH as the reaction base were studied through direct titration and back-titration. It was found that to minimize errors both the NaOH titrant and HCl should be standardized prior to titration and that a back-titration is preferable for all three reaction bases. Additionally, the titration should be performed immediately after degassing for 2 h with N₂ or Ar, and degassing should continue during the titration. This is found to be particularly true of the NaOH reaction base, where the effects of dissolved CO₂ are the most noticeable and persistent. With sufficient CO₂ removal, there is no significant difference between pH electrode or colour indication endpoint determination, and either is satisfactory.     

EFFECT OF ANIONS ON THERMODYNAMICS OF EXTRACTION OF Am(III) AND Eu(III) WITH OCTYL(PHENYL)-N,N-DIISOBUTYL-CARBAMOYLMETHYLPHOSPHINE OXIDE

The extraction of Am(III) and Eu(III) by octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO) in xylene from aqueous media containing 1.0 M NH₄NO₃, NH₄SCN, NH₄ClO₄ or a mixture of 0.3 M NH₄NO₃ + 0.7 M NH₄ClO₄ at pH 2.70 and at the temperatures of 15, 25, 35 and 45±0.1 °C has been studied. At all the temperatures, the species extracted were ML₃ · 3CMPO (M = Am(III) or Eu(III), L = NO₃ ^?, SCN^? or ClO₄ ^?) and M(NO₃)(ClO₄)₂ · 3CMPO. The thermodynamic parameters of the extraction reactions have been evaluated using the temperature coefficient method. The ?ΔG values follow the order SCN^? > NO₃ ^? + ClO₄ ^? > NO₃ ^? ≈ ClO₄ ^?, whereas the ?ΔH values an order NO₃ ^? + ClO₄ ^? > SCN^? > NO₃ ^? ≈ ClO₄ ^?. The effect of these anions on the thermodynamic parameters have been discussed employing compensation effects and also on the basis of the energy associated with the transfer of these anions from aqueous to the extractant phase.     

SOME METHODS FOR ANALYSIS OF SOLVENT EXTRACTION DATA AND THEIR APPLICATIONS

Abstract

Three programs develpoed to analyze data for liquid-liquid extraction of metal have been applied to the calculation of the stability constants of aqueous cadmium(II)-thiocyanato complexes by using the data for the extraction of tricaprylmethylammonium salt in benzene. The resulting stability constants of the aqueous thiocyanato complexes determined were: for the trial and error method log β₁ = 2·97, log β₂ = 3·70, log β₃ =3·50 and log β₄ =3·28; for the Gauss method log β₁ = 2·91, log β₂ = 3·70, log β₃ =3·35 and log β₄ = 3·29; for the Newton-Gauss method for log β₁ = 2·47, log β₂ =3·24, log β₃ =2·29 and log β₄ = 2·85     

Chemical analysis of electrical-engineering periclase

Conclusions Methods involving the photometric determination of Al₂O₃ with anthrazochrome, the complexometric back titration of CaO, and the direct complexometric titration of MgO have been developed. The possibility of using o-phenanthroline for the photometric determination of Fe₂O₃ in electrical-engineering periclase has been checked.The accuracy and reproducibility of the results of the determination of the components in periclase have been studied for artificial mixtures.Translated from Ogneupory, No. 5, pp. 52–55, May, 1980.     

DETERMINATION OF IRON IN GLASS SAND*

The 0-phenanthroline method for the colorimetric determination of iron has been adapted to the analysis of glass sand. The sample taken for analysis was decomposed by treatment with HF and H₂SO₄, followed by fusions of any insoluble material with Na₂CO₃ and finally with K₂S₂O₇. An aliquot was then adjusted to the proper pH by a simple procedure, the iron reduced by hydroxylamine hydrochloride, the 0-phenanthroline complex formed, and the transmittancy of the solution measured spectrophotometrically. The method is simple and rapid, and compares favorably in precision and accuracy with other available methods.     

A Study of Cerium–Manganese Mixed Oxides for Oxidation Catalysis

Cerium–manganese mixed oxides with compositions of Ce_0.5Mn_0.5O_1.75 and Ce_0.8Mn_0.2O_1.9 were prepared by the citric-acid (Pechini) method and their catalytic properties were compared to CeO₂ and Mn₂O₃. The mixed oxides exhibited higher specific rates than either CeO₂ or Mn₂O₃ for oxidation of both methane and n-butane. While XRD measurements of the mixed oxides suggested that the materials had primarily the fluorite structure, oxygen isotherms, measured by coulometric titration at 973 K, exhibited steps associated with MnO–Mn₃O₄ and Mn₃O₄–Mn₂O₃ equilibria, implying that manganese oxide must exist as separate phases in the solids. The P(O₂) for the MnO–Mn₃O₄ equilibrium is shifted to lower values in the mixed oxides, indicating that the manganese-oxide phase is affected by interactions with ceria.     

Acid–base properties of ion exchangers. I. Optimising of potentiometric titration of ion exchangers exemplified by carboxylic acid resins

The aim of this work was to determined conditions for fast titration the ion exchanger in the one-sample experiment allowing obtaining its equilibrium titration curve. Carboxylic acid ion exchangers KB-4 and Dowex MAC-3 were taken as examples. They were titrated under different conditions with NaOH, KOH and Ba(OH)₂. The forward and backward titration of concentrated immersions of finely ground ion exchanger in the electrolyte solutions with 20-min intervals between additions of the titrants of high concentration gave close results, identical to the results of the batch experiment if concentration of the supporting electrolyte was sufficiently high (1 M). It appeared possible to obtain equilibrium potentiometric titration curves in one working day and use this method for express control of properties of ion exchangers.     

Characterization of oxygen functional groups on carbon surfaces with water and methanol adsorption

We propose a new method, using the ambient temperature adsorption of methanol in the Henry law region as a molecular probe, to determine the concentration of surface oxygen functional groups (C_α) on carbon adsorbents. Two adsorbents: porous A5 and non-porous Carbopack F have been chosen here as experimental examples. The theoretical Henry constant (K_α) is the product of the intrinsic interaction between a methanol molecule and one functional group, α, having a concentration (C_α) and is estimated by carrying out a volume integration of the Boltzmann factor for methanol interacting with the functional group. Our results show that C_α determined with methanol for A5 compares well with that determined previously with water as the molecular probe (Nguyen, 2014 [1]); and both are in good agreement with results from Boehm titration. For Carbopack F, we find that C_α, determined by methanol adsorption, gives more realistic concentrations than those obtained by Boehm titration, which are subject to large errors because of the very low concentration of the functional groups. The method proposed here is fast and easy to implement, and serves as an alternative to the Boehm titration technique.