Determining Contact Angles of Powders by Liquid Penetration

The wettability of a powder is important, especially in chemical and pharmaceutical technologies when considering the manufacturing process and the properties of the final product. However, contact angle methods for powders are problematic. The common measurement techniques are the sessile drop method and the liquid penetration method. In this work the determination of contact angles of powders by liquid penetration is considered. In particular, we investigated the influence of the sample preparation and sampling device on the wetting process. A bulk with constant properties during the measurement must be guaranteed. We postulate a packing procedure to obtain reproducible measurements by ensuring constant powder properties.     

Catalytic and stoichiometric reduction of ketones and aldehydes by the hydridotetracarbonyl ferrate anion

Acetone is catalytically reduced to isopropyl alcohol by carbon monoxide and water in the presence of iron carbonyls and triethylamine at 100°C and 100 bar. Use of NaOH in place of triethylamine gives a much less efficient catalyst system. The Et₃NH·HFe(CO)₄ system also catalyses the reduction of n-butyraldehyde to n-butyl alcohol at room temperature in a fast stoichiometric reaction, whereas NaHFe(CO)₄ is inactive under the same conditions. The Et₃NH⁺ cation is necessary for the transfer of a proton to the carbonyl group, while the HFe(CO)₄^? anion carries out nucleophilic attack on carbonyl group and supplies the hydride ion.     

The use of cyclic voltammetric measurements for the determination of kinetic constants in enzyme-based electrocatalysis. The case of the redox mediated dihydronicotinamide adenine dinucleotide oxidation catalyzed by flavoproteins

On the basis of simulated voltammetric curves used as testing data, practical methods to extract the bimolecular rate constant for a mediated enzymatic catalysis with an excess of the substrate are examined. The evaluation criteria are the simplicity of treatment and the agreement between the expected and the obtained values of the rate constants. The results obtained indicate that the different approaches examined are equivalent.     

IMPUTING MISSING NATURAL RESOURCE INVENTORY DATA AND THE BOOTSTRAP

Gathering information on natural resource inventories is expensive, but lack of data inhibits resource sector modeling and policy analysis. Most work has focused on drawing broader inventory estimates from small survey samples. Other studies have used simple forward forecasting equations to project missing values. This research develops a method to impute missing inventory and growth observations when annual survey observations are not available. A one-way error component model is estimated and missing inventory values are imputed using an optimally weighted combination of forward and backward projections. This method ensures conformity of imputed observations with beginning and ending inventories. Confidence intervals for imputed inventory estimates are formed using the bootstrap method. Empirical results for estimated softwood and hardwood inventories in Louisiana are presented.     

Mittlere Schwingungsamplituden des Fluorosulfinat-Ions

The mean amplitudes of vibration of the SO₂F^– ion have been calculated using known spectroscopic data. The results are analyzed in comparison with those obtained for otherXO₂F species, and some general features related with the bond properties of such systems are also discussed.     

1,3-dipolar cycloaddition of nitrones to sugar enlactones

It was found that 1,3-dipolar cycloaddition of nitrones derived from formaldehyde and acetaldehyde to sugar enlactones proceeds regio- and stereospecifically to afford anti - endo adducts.     

Continuous-flow/stopped-flow system for determination of ascorbic acid using an enzymatic rotating bioreactor

The high sensitivity that can be attained using an enzymatic system and mediated by hydroquinone, has been verified by on-line interfacing of a rotating bioreactor and continuous flow/stopped-flow/continuous-flow processing. Horseradish peroxidase, HRP, [EC 1.11.1.7], immobilized on a rotating disk, in presence of hydrogen peroxide catalyses the oxidation of hydroquinone to p-benzoquinone, whose electrochemical reduction back to hydroquinone is detected on glassy carbon electrode (GCE) surface at −0.15 V. Thus, when l-ascorbic acid is added to the solution, this acid is reduced chemically (p-benzoquinone to hydroquinone) and acts as mediator of HRP, decreasing the peak current obtained proportionally to the increase of its concentration. The recovery of l-ascorbic acid from four samples ranged from 99.09 to 101.10%. This method could be used to determine l-ascorbic acid concentration in the range 12 nM-3.5 μM (r = 0.998). The determination of l-ascorbic acid was possible with a limit of detection of 6 nM in the processing of as many as 25 samples h⁻¹. The method was successfully applied for the analysis of l-ascorbic acid in pharmaceutical formulations.     

Structure of crystal violet tetraphenylborate

The crystal structure of crystal violet tetraphenylborate has been determined. C₂₅H₃₀N₃·C₂₄H₂₀B is orthorhombic, Pn2₁a, witha=9.497(6) Å,b=16.474(5) Å,c=25.894(9) Å,V=4051 ų,M _r =691.77,D _calc =1.13 g cm^–3 forZ=4,F(000)=1480, finalR=0.045, andR _w =0.044 for 1842 observed reflections [F ₀5(F ₀)]. The compound was crystallized from acetone. It was found to conduct poorly in either the crystalline state or as a pressed pellet although it serves well as a solution electrolyte.     

Kristallographische Daten und IR-Spektrum von AlVO4

The unit cell parameters of AlVO₄ have been determined from powder diagrams. The compound pertains to the triclinic system and is isostructural wi7h FeVO₄. The infrared spectra of AlVO₄ and FeVO₄ and of a series of solid solutions in the system AlVO₄/FeVO₄ has also been recorded and discussed.

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20. Mitt. der Reihe Orthovanadate und verwandte Verbindungen. 19. Mitt.:E. J. Baran, Z. anorg. allg. Chem., im Druck; 18. Mitt.:E. J. Baran, J. Less-Common Met.46, 343 (1976).