Leaching of some lithium silicate glasses and glass-ceramics by HCl

The leaching of some binary and ternary lithium silicate glasses and their respective glass-ceramics by HCl is reported.The leaching rate of lithium silicate glasses gradually decreases with the decrease of the percentage of Li₂O or by the introduction of small amounts of a third component, e.g. Al₂O₃, MgO, ZnO or B₂O₃. With a further increase in the proportions of B₂O₃ or ZnO the rate of leaching increases. The rate of leaching is also substantially modified by the conversion of glasses into glasses-ceramics.The results obtained are discussed in terms of the effects of the different ions on the rate of the interdifussion of the lithium and hydrogen ions in the glass and the leached layer, the phase separation developed in the glass, the type and concentration of crystalline phases developed in glass-ceramics and the composition of the residual glass phase.     

Efficient Synthesis and Reactions of New Functionally Substituted Pyrido[2,3-d]pyrimidine Candidates

Russian Journal of General Chemistry - Pyrido[2,3-d]pyrimidine derivatives were synthesized by the reaction of 2-hydrazinopyrido[2,3-d]-pyrimidin-4(3H)-one with different aryl aldehydes and active...     

Complexometric determination of some toxic mixtures of ions using bromo-cresol orange with visual endpoint indication

A rapid and simple general complexometric method was presented for the determination of lead, cadmium and thallium or mercury or arsenic(V) in laboratory synthesized mixtures similar to those of some ores, minerals and alloys of such metals. The precision and accuracy attainable in successive titrations of Pb(2+), Cd(2+) and Tl(3+) or Hg(2+) or AsO(3-)(4) (As(5+)) with 0.05 and/or 0.01 mol 1(-1) solutions of disodium ethylenediaminetetraacetate (Na(2)EDTA) and standard Pb(NO(3))(2) of the same concentration using Bromo-Cresol Orange (BCO) as a new metallochromic indicator with visual endpoint indication were studied. For the analysis of a three component mixtures of the aforementioned ions, Tl(3+) was at first directly titrated with Na(2)EDTA at pH 0.5-1 (HNO(3)) using BCO as indicator. At the thallium endpoint an excess of Na(2)EDTA was added and the pH was adjusted at pH approximately 4.8 using hexamine-HNO(3) buffer (solution A). The excess EDTA was back-titrated with standard solution of Pb(NO(3))(2). 1,10-Phenanthroline (1,10-phen) was added to release the EDTA combined with Cd(2+), while thiosemicarbazide (TSC) was used to liberate the EDTA from the mercury-EDTA chelate. To determine AsO(3-)(4) ion in such type of mixtures the pH of (solution A) was raised to a value of 10 using ammonia buffer. Excess standard Mg(2+) solution was added and the formed precipitate of MgNH(4)AsO(4) was separated, dissolved and its magnesium content equivalent to AsO(3-)(4) was determined complexometrically using Eriochrome Black-T (EBT) indicator. The interference caused by different anions, cations and organic acids was investigated. A comparison of the indicators BCO and Xylenol Orange (XO) for successive titration of the studied metal ions was carried out. The proposed successive titration method was applied successfully to some real samples of ores, minerals and alloys of the studied metal ions and the results were satisfactory and agreed with those obtained by AAS.     

Back titration with mercuric nitrate in alkaline medium analysis of tertiary mixtures of mercury(II) with some other metals

Summary Tertiary mixtures each containing mercury(II) were analysed by simple procedures involving combination between the recent method of back titration with mercuric nitrate in alkaline medium, and the volumetric methods which make use of masking agents as cyanide. The content of mercury(II) in most mixtures is determined potentiometrically with potassium iodide using the silver amalgam as indicator electrode. End points are attended with fair accuracy within 0.02 ml titrant and with reasonable jumps from 60 to 90 mv per 0.1 ml of mercuric nitrate solution or from 170 to 200 mv per 0.1 ml of potassium iodide solution.     

Synthesis of 2,5-bis(piperidinomethyl)piperidine and 1,5-bis(aminomethyl)-3-azabicyclo[3.2.1]octanones

Schmidt reaction of mono- and bis-Mannich bases1 and2 c derived from cyclopentanone gave the corresponding basically substituted 2-piperidones3 and4, respectively. Reduction of the latter afforded5. DoubleMannich reaction of2 a–c with primary amines gave 3-azabicyclo[3.2.1]octanone derivatives6 a–e and7. The transamination of2 a was investigated.     

Influence of solvent structure on the aquation of <Emphasis Type="BoldItalic">trans</Emphasis>-[Ru(3-MePy)<Subscript>4</Subscript>Cl<Subscript>2</Subscript>] complex in mixed aqueous solvents

The kinetics of the solvolytic aquation of trans-[Ru (3-Me Py)₄Cl₂] was studied spectrophotometrically in water – isopropanol in the range (30–90% v/v), and water acetonitrile in the range (10–70% v/v), and in the temperature range 50–65 °C. Plots of log k versus the reciprocal of the relative permittivity and Grunwald–Winstien gave non-linear plots. This non-linearity is derived from a large differential effect of solvent structure between the initial and transition states. The plot of log k versus water concentration was also non linear; evidence for the presence of a S _N ¹ mechanism. However, extrema in the variation of enthalpy ΔH* and entropy ΔS* of activation correlate well with the extrema in physical properties of the mixtures which are related to changes in solvent structure. Linear plots of ΔH* versus ΔS* were obtained and the iso- kinetic temperature indicates that the reaction is entropy controlled.     

The influence of solvent structure on the solvolysis of a ruthenium(II) complex in water–acetonitrile mixtures

The solvent effect on the rate of aquation of trans-[Ru(py)₄Cl₂] has been investigated by u.v. spectroscopy in the 40–55 °C range in MeCN–H₂O media. The thermodynamic activation parameters are calculated and discussed in terms of solvation effects. Log k was correlated with the reciprocal of the dielectric constant. A non-linear correlation was obtained and is discussed on the basis of specific solvation.     

Reactions with heterocyclic β-enaminoesters: A novel synthesis of 2-amino-3-ethoxycarbonyl-(4H)-pyrans

The reaction of ethyl cyanoacetate with -cyanochalcone (1) leads to the formation of -enaminoesters (3) viaMichael addition. Compound3 reacts with phenylmagnesium bromide to give the -enaminoketone5. Acetylation of3 gives the acetyl product4. Each of compounds1 and3 reacts with malononitrile to give -enaminonitrile6. Phenylhydrazine reacts with3 to give the hydrazone7. Similarly 3-phenyl-5-aminopyrazole reacts with3 to give theSchiff base8.

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Reaktionen mit heterocyclischen -Enaminoestern: Eine neue Synthese von 2-Amino-3-ethoxycarbonyl-(4H)-pyranen

Zusammenfassung Die Reaktion von Ethylcyanacetat mit -Cyanchalcon1 führt über eineMichael-Addition zum -Enaminoester3.3 gibt mit Phenylmagnesiumbromid das -Enaminoketon5. Acetylierung von3 gibt das Acetylderivat4.1 und3 reagieren mit Malodinitril zum -Enaminonitril6.3 gibt mit Phenylhydrazin das Hydrazon7; 3-Phenyl-5-aminopyrazol reagiert mit3 zurSchiff-Base8.

     

Radiation effects on polymers—VI. Enhancement of radiation vulcanization of styrene-butadiene rubbers mixes using two-component sensitizers

Different combinations of various multifunctional monomers and halogen co-agents were used to sensitize the radiation vulcanization of styrene-butadiene rubber (SBR). It was found that combinations of various vinyl compounds with hexachloroethane give rise to vulcanizates with considerably better physico-mechanical properties than those obtained in the presence of one of the two components. The enhancement of vulcanization depends upon the type of the vinyl co-agent used and on the concentrations of the sensitizers. The dose required to achieve vulcanizates with satisfactory physico-mechanical properties was reduced to 3–5 Mrad. Infra-red spectrophotometric analysis, supported by swelling and solubility tests, indicated that the co-agent most probably became a part of the vulcanized rubber. The mechanism of vulcanization in the presence of the two-component co-agent system is suggested.     

Spectrophotometric determination and titration of trivalent chromium with cyclohexane diamino tetraacetic acid (disodium salt)

Summary The reaction between trivalent chromium and disodium cyclohexane diamino tetra acetate (CDTA) at the boiling temperature has proved to be a suitable one for the spectrophotometric determination of small amounts of Cr^III covering the range 10–120 ppm in purely aqueous solutions. The variation of absorbancy with concentration conforms satisfactorily with Beer's law throughout the whole range. A variety of cations and anions do not interfere with such a determination. A procedure is given for the spectrophotometric titration of Cr^III with CDTA.

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Zusammenfassung Die Reaktion zwischen dreiwertigem Chrom und Dinatriumcyclohexandiamintetraacetat (CDTA) bei Siedetemperatur wird zur spektrophotometrischen Bestimmung von kleinen Mengen Chrom (III) benutzt. Das Beersche Gesetz wird im Bereich zwischen 10 und 120 ppm erfüllt. Eine größere Anzahl verschiedener Kationen und Anionen stört die Bestimmung nicht. Die spektrophotometrische Titration wird ebenfalls beschrieben.

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on leave from University of Massachusetts, Amherst, Mass., USA.