Measurements and correlation of vapour-liquid equilibria of 2-butanone and hydrocarbons binary systems at two different pressures

Consistent isobaric vapour-liquid equilibrium data have been measured for 2-butanone + n-hexane, 2-butanone + n-heptane, and 2-butanone + 2,2,4-trimethylpentane at two different pressures. All binary systems present a minimum boiling azeotrope at both pressures, and show that the azeotropic compositions are weakly dependent on pressure. The equilibrium data were correlated using the Wilson, NRTL, and UNIQUAC models for which the parameters are reported.     

Synthesis and Crystal Structure of Dichlorobis(dimethylsulfoxide)oxoperoxo Molybdenum(VI)

Hydrogen peroxide reacts with [MoO₂Cl₂(dmso)₂] to produce orange crystals of the title complex, [MoO(O₂)Cl₂(dmso)₂]. The structure is orthorhombic with distorted pentagonal bipyramidal geometry around the molybdenum ion. A short O‐O bond length suggested the presence of a superoxide, but electron paramagnetic resonance measurements definitely supported the peroxo structure.     

New (k; r)-arcs in the projective plane of order thirteen

A (k;r)-arc $\cal K$ is a set of k points of a projective plane PG(2, q) such that some r, but no r +1 of them, are collinear. The maximum size of a (k; r)-arc in PG(2, q) is denoted by m _r (2, q). In this paper a (35; 4)-arc, seven (48; 5)-arcs, a (63; 6)-arc and two (117; 10)-arcs in PG(2, 13) are given. Some were found by means of computer search, whereas the example of a (63; 6)-arc was found by adding points to those of a sextic curve $\cal C$ that was not complete as a (54; 6)-arc. All these arcs are new and improve the lower bounds for m _r (2, 13) given in [10, Table 5.4]. The last section concerns the nonexistence of (40; 4)-arcs in PG(2, 13).     

The Effects of Supply on Mazzaella laminarioides (Rhodophyta,Gigartinales) from Southern Chile

The effects of nitrate supply on growth, pigments, mycosporine‐like amino acids (MAAs), C:N ratios and carrageenan yield were investigated in Mazzaella laminarioides cultivated under solar radiation. This species is economically important in southern Chile where an increase of nitrogen in coastal waters is expected as a consequence of salmon aquaculture activity. Apical segments were cultivated in enriched seawater with five different concentrations (0, 0.09, 0.18, 0.38 and 0.75 mm ) during 18 days. Although phycoerythrin and phycocyanin content, as well as C:N ratios, were reduced in the control treatment (without supply), when compared to treatments, total MAA concentration, carrageenan yield and growth rates were similar in all tested conditions. Nevertheless, during the experiment, an important synthesis of mycosporine‐glycine took place in a nitrate concentration‐dependent manner, with accumulation being saturated around 0.18 mm of nitrate. These results indicate that exposure to high concentration of more than 100 times the values observed in the nature did not impair the photoprotection system, as determined by MAAs, nor did it have a deleterious effect on growth or carrageenan yield of M. laminarioides, a late successional species from Chile.     

An intelligent flow analyser for the in-line concentration, speciation and monitoring of metals at trace levels

An intelligent and versatile flow system is proposed for the in-line speciation and/or concentration of metal ions at a wide range of concentrations without requiring manifold reconfiguration. On one hand, sample enrichment strategies are accomplished using packed-bed reactors, on the other hand speciation procedures are readily performed exploiting the selective complexation of the different oxidation states with the appropriate chromogenic reagents.

The potentials of the automated methodology were evaluated using the spectrophotometric monitoring of iron as a model of chemistry. Under the optimised physical and chemical variables, linear analytical curves over the ranges 0.025–0.5 or 2.0–40 mg l⁻¹ Fe were attained. The 3σ detection limit, the repeatability at the 0.5 mg l⁻¹ level, the enrichment factor for a sampling volume of 10 ml, and the maximum injection throughput were 8.4 ng ml⁻¹ Fe, 2.5%, 58.6 and 22 h⁻¹, respectively. The flowing system was applied to the speciation analysis of iron in waters, pharmaceutical formulations and agricultural products, using ICP-OES detection as an external reference method for total iron determination.

A remarkable feature of the expert system hereby presented is the ability to decide by itself if the pre-concentration and/or oxidation of the sample zone is required.     

Thermogravimetric Analysis for Acidity Determination in Pillared Clays

Thermogravimetric analysis of pyridine adsorption was applied to study the acidity at different temperatures of clays pillared with Al pillars and mixed Al-Ga pillars, in relation to the starting montmorillonite. These results were compared with those obtained by means of a pulse-chromatographic technique. The pillaring process produces a large number of acid centers in the samples. Al-Ga-PILC has a higher acidity than Al-PILC. This revised version was published online in July 2006 with corrections to the Cover Date.     

Diagram,a drawing program for logarithmic concentration/pH plots

DIAGRAM provides graphic display of acid-base equilibria based on logarithmic concentrations of the species involved. Various subroutines facilitate calculation of α and concentration values of the different species in a system and successive protonations can be superimposed on the output.     

Band gap tuning of Cu(In,Ga)Se2 thin films by electrodeposition and their subsequent selenization using a rapid thermal annealing system

Journal of Solid State Electrochemistry - Band gap tuning of electrodeposited Cu(In1-x,Gax)Se2 thin films through varying In3+ and Ga3+ concentrations in the electrolytic bath is demonstrated....