Separation of unsaturated and aromatic hydrocarbons on capillary columns packed with barium sulphate

Summary Isomeric hydrocarbons with molecules having similar geometry but differing in the electron density distribution were separated on capillary columns packed with barium sulphate, a non-porous ionic adsorbent. Samples of BaSO₄ were washed free of foreign ions and modified by solutions of alkaline metal halides. The selectivity of the separation of unsaturated and aromatic hydrocarbons can be controlled by varying the conditions of the BaSO₄ treatment. Capillary columns packed with the ionic adsorbent were successfully used to separate all xylene and butene isomers, as well as isomers of cis and trans octene-2.     

Separation of lead sulphate from barium sulphate in their determination in glass

The conventional method for separation of lead from a combined lead and barium sulphate precipitate by extraction with ammonium acetate has been critically studied. The results show that quantitative separation of lead is possible only when the molar concentration ratio of barium to lead is 4.2 or above, but at ratios below 4.2 the method fails because of the formation of a solid solution of lead and barium sulphates which is maximal at initial mole-ratio 0.42. The lead in the solid solution, however, forms a strong soluble complex with EDTA and can be quantitatively separated. Based on this, a gravimetric method has been worked out for determination of lead and barium in glass.     

DTA studies on the barium sulphate—Calcium sulphate eutectoid mixture

Samples of a nearly eutectoid mixture of 60 mole% BaSO₄–40 mole% CaSO₄, a highly effective system for the selective sorption of strontium, were studied using the DTA method. The effects of the time of thermal treatment and the number of thermal cycles of two different types on the homogenisation degree and thus on the formation of the metastable barium—calcium sulphate were examined. The conditions of the thermal decomposition of the metastable sulphate, the activation energy and the heat released during this process were estimated.

---

Zusammenfassung Eine durch ihre selektive Fähigkeit zur Sorption von Strontium ausgezeichnete, beinahe eutektische Mischung von 60 Mol% BaSO₄ und 40 Mol% CaSO₄ wurde differentialthermoanalytisch geprüft. Der Einfluß der Zeit der thermischen Behandlung und von zwei verschiedenen thermischen Zyklen auf den Homogenisierungsgrad, und so auch auf die Bildung des metastabilen Barium-Kalzium Sulfates wurden untersucht. Die Bedingungen der thermischen Zersetzung des metastabilen Sulfats, die Aktivierungsenergie und die während des Vorgangs freigesetzte Wärme wurden ermittelt.

---

Résumé Etude par ATD d'échantillons provenant d'un mélange BaSO₄ 60 moles% -CaSO₄ 40 moles %, de composition voisine de celle de l'eutectoide et très efficace pour la sorption sélective du strontium. Etude de l'influence de la durée du traitement thermique et du nombre de cycles thermiques (de deux types différents) sur le degré d'homogénéisation, c'est-à-dire sur la formation de sulfate de baryum-calcium métastable. On a estimé les conditions de la décomposition thermique du sulfate métastable, l'énergie d'activation et la quantité de chaleur dégagée par le processus.

---

, 60 % BaSO₄—40 % CaSO₄. . . , .

---

---

Thanks are due to Dr. L. Berák for the provision of results of dilatometric measurements, for useful assistance and continual encouragement.     

Redox reactions on columns

In a study of redox reactions on columns, the work of Cerrai and Testa has been extended. It has been shown that insolubility of the redox compound is the most important factor and that adsorptive forces play little or no part. A useful redox column method for the determination of iron and vanadium, which compares favourably with that using a Jones reductor column, has been developed. The redox potentials of several substituted hydroquinones have been measured.     

Electrodeposition mechanism of nickel films on polycrystalline copper from dilute simple sulphate solutions

In this paper, we have studied the mechanism of nucleation and growth of nickel from a simple sulfate bath on polycrystalline copper (Cu) substrate. Cyclic voltammetry technique and current transients recorded during electrodeposition of nickel on Cu were used to evaluate the electrochemical deposition of nickel on copper. Results show that nickel starts to grow on copper from a typical potential of −0.7 V vs. Ag/AgCl. Increasing scan rate of cyclic voltammograms shifts the reduction peaks towards a more negative values. We plotted non-dimensional graphs according to the Scharifker-Hills theory and concluded an instantaneous nucleation and growth mechanism for nickel elecrodeposited on copper based on our experimental conditions.     

Extraction of sulphuric acid from technological solution of hydroxylamine sulphate

The extraction of sulphuric acid from solutions containing hydroxylamine sulphate and ammonium sulphate with Cyanex 923 and the acid stripping from loaded Cyanex 923 are studied at 20 and 50°C. The effect of the numbers of extraction and stripping stages and the volume phase ratios in extraction and stripping upon sulphuric acid recovery is discussed. The process can be design to obtain a high or low recovery of sulphuric acid but with its low or high concentration, respectively.     

Supramolecular helical fluid columns from self-assembly of homomeric dipeptides

Herein, we demonstrate that with the widespread theme of residue patterning and stereochemical restraints of self-complimenting proteinogenic amino acids, a new and rich class of homomeric dipeptides exhibiting two-dimensional fluid aggregates with hierarchical ordering can be obtained. In particular, a simple way of achieving a class of functional dipeptides, wherein the first and the second residues chosen are L-/D-alanines and L-/D-leucines, has been accomplished. The supramolecules synthesized can be regarded as intermediates between polycatenars and taper-shaped amphiphiles because they possess two lipophilic segments interlinked by a peptide unit (spacer). Two pairs of enantiomers and their respective diastereomers derived from these amino acids are evidenced to self-organize into a helical columnar phase through hydrogen bonding by means of FTIR, UV/Vis, and chiroptical circular dichroism (CD) spectral analyses as well as by optical, calorimetric, electrical switching, and X-ray studies. The CD and X-ray studies have revealed that the form chirality (handedness) and the magnitude of out-of-plane fluctuations of the lattice planes of the fluid supramolecular columnar structures are solely directed by the stereochemistry encoded in the spacer. Of special significance, the less frequently found oblique helical columnar phase formed by a pair of enantiomers derived from L-/D-alanines, unlike those derived from other amino acids, exhibit ferroelectric behavior; the measured spontaneous polarization is as high as 440 nC cm(-2). Besides, all these supramolecules form stable organogels in ethanol and the CD and SEM studies on a representative gel suggest the presence of helical structures.     

Supramolecular helical columns from the self-assembly of chiral rods

Chiral-bridged rod molecules (CBRs) that consisted of bis(penta-p-phenylene) conjugated to an opened or closed chiral bridging group as a rigid segment and oligoether dendrons as flexible segments were synthesized and characterized. In the bulk state, both molecules self-assemble into a hexagonal columnar structure, as confirmed by X-ray scatterings and transmission electron microscopy (TEM) observations. Interestingly, these structures display opposite Cotton effects in the chromophore of the aromatic unit in spite of the same chirality (R,R) of the chiral bridging groups. The molecules were observed to self-assemble into cylindrical micellar aggregates in aqueous solution, as confirmed by light scattering and TEM investigations, and exhibit intense signals in the circular dichroism (CD) spectra, which are indicative of one-handed helical conformations. The CD spectra of each molecule showed opposite signals to each other, which were similar to those in the bulk. Notably, when the opened CBR was added to a solution of closed CBRs up to a certain concentration, the CD signal of the closed CBR was amplified. This implies that both molecules co-assemble into a one-handed helical structure because the opened chiral bridge is conformationally flexible, which is inverted to co-assemble with the closed CBR. These results demonstrate that small structural modifications of the chiral moiety can transfer the chiral information to a supramolecular assembly in the opposite way.     

Applications of heart cutting from packed to capillary columns

The power of capillary gas chromatography can be enhanced by selective fractionation of the sample. One way of doing this is heart cutting from a packed gas chromatographic column. This paper describes modification of a commercial instrument for such separations. Components of the system include an automated Deans switch and an electrically heated trap. The benefits of this arrangement are illustrated with chromatograms of naphtha, urinary aromatic acids, and wine volatiles.     

Preparation and characterisation of magnesium sulphate heptahydrate from Kimberlite tailings

Weathered Kimberlite tailings of Panna Diamond Mines were characterised by DTA and XRD techniques. The XRD pattern shows the presence of serpentine, quartz, calcite, hematite, magnetite and anatase phases. DTA curve indicates first endothermic peak at 125C due to dehydration of the mineral and second endo peak at 670C due to dehydroxylation of serpentine closely followed by an exothermic peak at 810C associated with the formation of forsterite. XRD and DTA studies of sulphuric acid leach residue of the Kimberlite shows the disappearance of serpentine phase with the appearance of CaSO₄·2H₂O phase. The product MgSO₄·7H₂O obtained after purification and crystallisation. From the optical emission spectroscopic analysis, the product was found to contain Ca, Fe and SiO₂ as trace impurities.

---

Zusammenfassung Mittels DTA und Röntgendiffraktion wurden verwitterte Kimberlit-AbgÄnge aus Diamantbergwerken in Panna charakterisiert. Das Röntgendiagramm zeigt die Gegenwart von Serpentin-, Quarz-, Kalzit-, HÄmatit-, Magnetit- und Anatas-Phasen. Die DTA-Kurve zeigt einen ersten endothermen Peak bei 125C (Dehydratation des Minerales) und einen zweiten endothermen Peak bei 670C (Dehydroxylierung von Serpentin), eng gefolgt von einem exothermen Peak bei 810C (Bildung von Forsterit). Röntgendiffraktionsund DTA-Untersuchungen an einem schwefelsauren Extraktionsauszug von Kimberlit zeigen das Verschwinden der Serpentin-Phase, aber das zusÄtzliche Auftreten einer CaSO₄·2H₂O-Phase. Nach Reinigung und Kristallisation wurde MgSO₄·7H₂O als Produkt erhalten, dessen optische emissionsspektroskopische Untersuchung in Spuren Verunreinigungen mit Ca, Fe und SiO₂ zeigten.

     

Formation of hydrated titanium dioxide from seeded titanyl sulphate solution

The paper analyses the influence of various kinds and amounts of titanium dioxide nuclei addition to a solution of titanyl sulphate on the conversion degree of TiOSO₄ to hydrated titanium dioxide and sulphuric acid. An industrial solution of titanyl sulphate used to produce titanium white was used in the present investigations. It was found that the course of hydrolysis clearly depended on the investigated parameters. The anatase nuclei calcined at 373 K and 333 K and rutile nuclei increased the degree of titanyl sulphate hydrolysis as compared to non-nucleation hydrolysis. The final degree of hydrolysis was by 1–2 % higher than that achieved without any nuclei addition. The constant rates of both colloidal intermediate and final crystalline products formation were higher in the hydrolysis process with both anatase nuclei after heat treatment at lower temperature and rutile nuclei in comparison to the same processes conducted in the absence of these nuclei. Presented at the 35th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 26–30 May 2008.