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Thermal analysis of metal complexes, III

Investigation of the thermal decomposition of pyridine halide (pseudohalide) mixed complexes and of their decomposition products

Journal of Thermal Analysis and Calorimetry
Authors: G. Liptay, K. Burger, é. Mocsári-Fülöp, and I. Porubszky
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Cellulose substituted by organosilicon groups represents a new type of modified cellulose. The silylation changes the physical and chemical properties of cellulose drastically. The thermoanalytical investigation of differently trimethylsilylated cellulose derivatives was carried out under static conditions in air atmosphere. The DTA curves of the cellulose used as starting material are different from those of its silylated derivatives. In the latter a new characteristic exothermic peak appears in the range 320–370°. The value of this maximum depends on the grade of silylation, being shifted towards higher temperatures with higher degrees of substitution.

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The thermal decompositions of 8 complexes of the type A · H[Cr(NCS)4(am)2] (A=NH3, pyridine,α-picoline or aniline, andam=NH3 or aniline) and of 14 complexes of the type M[Cr(NCS)4(am)2] (M=K, Ag, Tl, 1/2 Cd, 1/2 Pb or 1/3 Bi, andam=NH3, benzylamine or aniline derivatives) were studied by means of a derivatograph. In the case of the A · H salts the formation of Cr(NCS)3 was observed as a labile intermediate. Characteristic temperatures are discussed in terms of the polarizing effect of the outer sphere cations and of the nucleophilic character of the ligands. The results are compared with those obtained in the thermal decompositions of the analogous salts of the complex acid H3[Cr(NCS)6].

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Abstract  

The ability of some siliconates to hydrophobize and modify the surface of different kinds of asbestos was studied. A 6 wt% aqueous solution of potassium methylsiliconate was used in various quantities. After treatment, the asbestos samples were analysed by IR-spectroscopy, TG-DTA and electron microscopy. Structural changes were found on the asbestos surface, including the appearance of chemical bonds. The studies revealed that the sorption and lyophilic properties of asbestos are lowered, these being the basic preconditions for its injurious action on health.

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Abstract  

Manganese(II) chloride complexes with 3,4- and 3,5-lutidine have been prepared. The crystal symmetry and cell dimensions have been calculated on the basis of powder diffraction data. The compounds were characterised also by FT-IR spectrometry. The thermal decomposition of the complexes has been studied by thermogravimetry and DSC. By plotting densities vs. molar mass, the diagram obtained has correspondence to similar observations in other solid metal-lutidine complex systems.

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Abstract  

14 mixed Co(III) dioximine chelates of the types [Co(DioxH)2(amine)2]X (X = Br, I, NO3, ClO4) and H[Co(DioxH)2(N3)2], respectively (DioxH2-1,2-cyclohexane dione dioxime (nyoxime), 1,2-cycloheptane dione dioxime (heptoxime) 1,2-cyclooctane dione dioxime (octoxime) were obtained and their thermal decompositions were studied in an argon atmosphere. After the dehydration of the crystallohydrates, both types of complexes exhibit 3 decomposition stages. For the [Co(DioxH)2(amine)2]X type complexes (X = Br, I) the first endothermal stage is the substitution of an amine molecule for the external sphere anion and this process is followed by two exothermal decomposition stages. With H[Co(DioxH)2(N3)2] type complexes the first and third processes are relatively slow, but the second process is very fast, corresponding to a vertical portion of the TG curves. From the TG curves kinetic parameters were derived for 11 processes and the validity of a non-linear compensation law was observed.

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