Sensitized schiff's reagent as an acid-base indicator

The sensitized Schiff's reagent has been used as an indicator in the neutralization of strong acids by means of strong or weak bases. (1) Since the acid to alkali transition is much sharper than the reverse process, the titration is best done by adding alkali to the acid. (2) The results are compared with those of titrations using methyl orange as indicator. (3) The end-point is very sharp with sensitized Schiff's reagent, the transition taking place from a dull red colour to an abrupt rise in intensity. (4) Acids which are comparable in strengths or weaker than H₂SO₃ cannot be titrated with this reagent as indicator.     

Spectrophotometric study of the formaldehyde-leuco-methylene blue reaction

The sensitivity of the reaction between foimaldchyde and Icuco-mcthyleno blue has been found to be increased in the presence of ethyl alcohol, acetone, dicthyl ketone and methyl ethyl ketone. Acetone has been found to be most effective. Sensitisers increase the absorption maximum and stabilise it, while the rate of development of methylene blue colour is slowed down.Sensitivity also depends upon the content of thiosulphate used to prepare the Icuco-base; a smaller amount of thiosulphate increases greater sensitivity.     

Automation in und mit der Analytischen Chemie

Ohne Zusammenfassung

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Automation in and with analytical chemistryV. Classification of working ranges in analytical chemistry with regard to computers

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Teil IV: diese Z. 256, 7 (1971)     

Optimization of firing parameters for ceramic wares by thermal analysis

Aesthetic and utilitarian properties of traditional ceramic wares as well as engineering properties of modern advanced ceramics are attained by maintaining an optimum temperature-time-atmosphere relationship, called firing schedule, in the kiln. The contribution of modern thermal analysis (TA) techniques such as TG/DTG, TG/EGA, TG/MS, DTA, DSC, TDA, etc. in 1) optimizing production steps by raw material quality control, by studying binder burn out, product densification, 2) in simulating appropriate preheating, firing and cooling schedules as well as 3) in developing shorter firing cycles has been extensively reported in recent literature. The paper will first discuss theoretical curves and energy required for ceramic firing and present from the literature selected examples of applications of thermal analysis in ceramic technology.     

Kinetics and mechanism for the aquation of bismalonatoethylenediaminecobaltate(III) ion in acid perchlorate media

Summary The title complex aquates in acid media, first to [Co(mal)-(H₂O)₂(en)]⁺ (1) (Step 1) and subsequently to [Co(H₂O)₄(en)]³⁺ (2) (Step 2). Complex species (1) has been separated and characterised in solution. While Step 1 involves only a second-order acid catalysed path, Step 2 involves both a first-order acid independent path and a second-order acid catalysed path. The rate constants and activation parameters evaluated for these reaction paths have been compared with those for similar carboxylato-cobalt(III) complexes. This, together with an observed isokinetic relation, indicates that the rate-determining step involves opening of the unprotonated (in the spontaneous acid independent path) or the protonated (for the acid catalysed path) chelate ring of the malonate ligand and insignificant solvation of the central metal ion.     

An interesting ring contraction of a class of bromohydrins and trans-dibromides

An efficient ring contraction of stereoisomeric 1,2-benzo-4-bromo-3-hydroxycyclohept-1-ene and their derivatives (1a-e) to (2a-c) is reported, and a probable mechanism for this ring contraction has been suggested.     

Synthesis and characterization of starch-graft-polycaprolactone as compatibilizer for starch/polycarprolactone blends

Polycaprolactone (PCL) was grafted onto starch through introduction of urethane linkages. The grafting reaction was carried out in two steps. The first step was the reaction of hydroxyl-terminated PCL with 2,4-tolylene diisocyanate. The isocyanate terminated PCL was then reacted with starch to obtain starch-graft-polycaprolactone (starch-g-PCL). The grafting reaction was confirmed by FT-IR spectroscopy. The compatibility of the starch/PCL blend was enhanced with a compatibilizer, starch-g-PCL, whose amount was 3 wt.-% of the blend. The tensile strength and morphology of the compatibilized blend were determined. It was found that the compatibilized starch/PCL blend has finer phase domains and an improved interfacial adhesion. Mechanical properties of the compatibilized blend were found to be significantly higher than those of the corresponding uncompatibilized starch/PCL blend.     

New iron(III) complexes with thiosemicarbazones derived from 5-methyl-3-formylpyrazole

New iron(III) complexes of 5-methyl-3-formylpyrazole thiosemicarbazone (HMPzTS) and 5-methyl-3-formylpyrazole-4-phenylthiosemicarbazone (HMPzPTS), namely [Fe(MPzTS)₂]X and [Fe(MPzPTS)₂]X respectively, where X=Cl, NO₃, SCN and ClO₄, have been synthesised and physico-chemically characterised by magnetic measurements (polycrystalline state), electronic, i.r., e.s.r. and Mössbauer spectra. All are cationic complexes containing two monoprotonic tridentate ligands with NNS donor sites and an anionic counterpart; they behave as 1:1 electrolytes in MeOH/DMF. Coordination to central iron(III) via the pyrazolyl nitrogen (²N), the azomethine nitrogen and the thiolato sulphur atom is confirmed in the complexes from i.r. data. E.s.r. data (RT & LNT) reveal the presence of a spin-paired iron(III) cation with d² _xyd² _yzd¹ _xy configuration. The ⁵⁷Fe Mössbauer spectral data (RT) are commensurate with the presence of two iron(III) spin states, the percentage of each being dependent upon the counterion of the species.     

Ternary complexes of substituted catechols and catecholamines

Stability constants of the ternary complexes [CuAL] whereA = 5-Nitro-1,10-phenanthroline, bis(2-pyridyl) ketone (DPK) orbis(2-pyridyl)amine (DPA) andL is the dianion of catechol, tiron, protocatechic acid, pyrogallol, 1,8-dihydroxynaphthalene, catecholaldehyde, 2,3-dihydroxynaphthalene, dopamine or adrenaline have been determined by potentiometric titration in dioxane water (1:1 v/v) medium using a SCOGS computer programme. The observed trend of stability is explained on the basis of the nature of substitution over the ligands, chelate ring size and also the composition of mixed solvent in case of DPK. Structural changes in DPK have also been discussed as a function of pH, composition of medium and coordinating mode of the secondary ligand in the ternary complexes.