Measurement of the corrosion rate of aluminium in sodium hydroxide using holographic interferometry

The application of holographic interferometry to the measurement of the corrosion rate of aluminium in sodium hydroxide is investigated. Details of the fabrication of the corrosion cell and the experimental procedure are given. Thickness loss of aluminium was found for different dissolution times and compared with the conventional weight-loss method using a microbalance.

Potentiometric determination of activities in the two-phase fields of the system Na2O---(α)Al2O3

Three compounds have been found to be stable in the pseudobinary system Na2O---(α)Al2O3 between 825 and 1400 K; two nonstoichiometric phases, β-alumina and β″-alumina, and NaAlO2. The homogeneity of β-alumina ranges from 9.5 to 11 mol% Na2O, while that of β″-alumina from 13.3 to 15.9 mol% Na2O at 1173 K. The activity of Na2O in the two-phase fields has been determined by a solid-state potentiometric technique. Since both β- and β″-alumina are fast sodium ion conductors, biphasic solid electrolyte tubes were used in these electrochemical measurements. The open circuit emf of the following cells were measured from 790 to 980 K: [GRAPHICS] The partial molar Gibbs' energy of Na2O relative to gamma-Na2O in the two-phase regions can be represented as: DELTA-GBAR(Na2O)(alpha- + beta-alumina) = -270,900 + 24.03 T, DELTA-GBAR(Na2O)(beta- + beta"-alumina) = -232,700 + 56.19 T, and DELTA-GBAR(Na2O)(beta"-alumina + NaAlO2) = -13,100 - 4.51 T J mol-1. Similar galvanic cells using a Au-Na alloy and a mixture of Co + CoAl(2+2x)O4+3x + (alpha)Al2O3 as electrodes were used at 1400 K. Thermodynamic data obtained in these studies are used to evaluate phase relations and partial pressure of sodium in the Na2O-(alpha) Al2O3 system as a function of oxygen partial pressure, composition and temperature.

Reduction In Metal-Mold Reactivity In Titanium Castings Through The Use Of Sodium Aluminate As Binder In Zircon Sand Molds

The present work is aimed at evaluating an alternative moulding system, namely, sodium aluminate bonded zircon sand mould and assess its suitability in relation to the much studied sodium silicate bonded zircon sand moulding system. It is described in the study presented here that with regard to metal - mould reaction, sodium aluminate bonded zircon sand mould system is a superior viable system as compared to sodium silicate bonded zircon moulding system at mould firing temperatures of 873 - 1473 K.

Relation between effective atomic charge and chemical shifts in X-ray absorption spectra of transition-metal compounds

Chemical shifts of K absorption discontinuities, Delta E, of several manganese, iron and cobalt oxides with the metal in the formal oxidation states between +2 and +4, have been measured. These data, together with data in the literature on other compounds of these metals, can be fitted into the expression Delta E=aq+bq2, where q is the effective atomic charge on the metal. Theoretical considerations also support this functional relationship between Delta E and q.

The effects of beta-mercaptoethanol and sodium dodecyl sulfate on the Humicola insolens beta-glucosidase

Hydrolysis of p-nitrophenyl-beta-D-glucoside by the beta-glucosidase of a thermophilic and cellulolytic fungus, Humicola insolens was stimulated by two-fold in the presence of high concentrations of beta-mercaptoethanol. This enzyme did not have any free sulfhydryl groups and high concentrations of beta-mercaptoethanol (5% v/v) reduced all of the three disulfide bonds present in the enzyme. In contrast, the hydrolysis of cellobiose and cellulose polymers was inhibited by 50% under the same conditions. Sodium dodecyl sulfate (1% w/v) even in combination with beta-mercaptoethanol did not show any significant effects on this enzyme. These unusual properties suggest that this enzyme may be of significant importance for understanding the structure of the enzyme.

A new general method for the introduction of the aldehyde function in aromatic compounds

Side chain bromination of aromatic amidomethylated compounds yields aldehydes.

Inhibition of rat liver mevalonate pyrophosphate decarboxylase and mevalonate phosphate kinase by phenyl and phenolic compounds.

1. Mevalonate pyrophosphate decarboxylase of rat liver is inhibited by various phenyl and phenolic acids. 2. Some of the phenyl and phenolic acids also inhibited mevalonate phosphate kinase. 3. Compounds with the phenyl-vinyl structure were more effective. 4. Kinetic studies showed that some of the phenolic acids compete with the substrates, mevalonate 5-phosphate and mevalonate 5-pyrophosphate, whereas others inhibit umcompetitively. 5. Dihydroxyphenyl and trihydroxyphenyl compounds and p-chlorophenoxyisobutyrate, a hypocholesterolaemic drug, had no effect on these enzymes. 6. Of the three mevalonate-metabolizing enzymes, mevalonate pyrophosphate decarboxylase has the lowest specific activity and is probably the rate-determining step in this part of the pathway.

A Study of copper-compounds by x-Ray Absorption-spectroscopy

Chemical shifts, ΔE, of the K-absorption discontinuity in several compounds of copper possessing formal oxidation states between 0 and III have been measured. The shifts show a parabolic dependence on the formal oxidation state as well as on the effective atomic charge, q, on copper. Anomalous chemical shifts shown by some of the compounds are discussed in terms of the bonding in these compounds. The ΔE values have also been correlated with the core electron binding energies obtained from X-ray photoelectron spectroscopy.

Chemical Shift of the X-Ray K-Absorption Edge of Cu in Some of Its Compounds, Complexes and Superconductors

Chemical shifts, ΔE, of the X-ray K-absorption edge in several compounds, complexes of copper including its superconducting oxides possessing formal oxidation states +1 and +2 have been measured. It has been shown that the chemical shift is primarily governed by the effective ionic charge on the absorbing ion and the nature of the atoms in the first coordination shell around the absorbing ion. The relation between the chemical shift, ΔE , and the effective charge q on the absorbing ion is found to be ΔE=Aq+Bq2+Cq3+Dq4 (A, B, C and D are constants). The effects of electronegativity, atomic number, oxidation state, crystal structure, the valence d-orbital electrons, etc. on the X-ray absorption chemical shift have been discussed. ©1990 The Physical Society of Japan

Singlet quenching of tetraphenylporphyrin and its metal derivatives by iron(III) coordination compounds

The quenching of fluorescence of the free-base tetraphenylporphyrin, H2TPP, and its metal derivatives, MgTPP and ZnTPP by diverse iron(III) complexes, [Fe(CN)6]3−, Fe(acac)3, [Fe(mnt)2]−, Fe(Salen)Cl, [Fe4S4(SPh)4]2−·, FeTPPCl and [Fe(Cp)2]+ has been studied both in homogeneous medium (CH3CN) and micellar media, SDS., CTAB and Triton X-100. The quenching efficiencies are analysed in terms of diffusional encounters and it has been possible to separate static quenching components. The quenching constants are dependent on the nature of the ligating atoms around iron(III) and also on the extent of π-conjugation of the ligands. The quenching mechanism has been investigated using steady-state irradiation experiments. Evidence for oxidative quenching by iron(III) complexes was obtained, though the spin multiplicities of the excited electronic states of iron(III) complexes permit both energy and electron transfer mechanisms for quenching of the singlet excited state of the porphyrins.

Crystal Structure of Sodium Deoxyinosine Monophosphate

The crystal and molecular structure of sodium deoxyinosine monophosphate (5'-dIMP) has been determined by x-ray crystallographic methods. The crystals belong to orthorhombic space group P212121, with a = 21.079(5) Aring, b = 9.206(3) Aring and c = 12.770(6) Aring. This deoxynucleotide shows common nucleotide features namely anti conformation about the glycosyl bond, C2' endo pucker for the deoxyribose sugar and gauche-gauche orientation for the phosphate group. The sodium ion is directly coordinated to the O3' atom, a feature observed in many crystal structures of sodium salts of nucleotides.