Determination of mercury content of some pharmaceutical products by catalytic titration

Summary Catalytic constant-current potentiometric titration with a cathodically polarized graphite indicator electrode was applied for determination of mercury or organomercuríc compounds in some pharmaceutical products (Exomycol, Unguentum Hydrargyri, Salyrgan and Merthiosal). The Ce(IV)-As(III) system in the presence of sulphuric acid was used as indicator reaction; it is catalysed by the first excess of titrant, potassium iodide. Special attention was paid to sample decomposition. The methods are simple and fast, and can be recommended for determination of mercury or organomercuric compounds. The results are in good agreement with those of other methods.

---

Bestimmung des Quecksilbergehaltes in einigen pharmazeutischen Produkten durch katalytische Titration

Zusammenfassung Die katalytische potentiometrische Titration bei kleinem konstantem Strom mit der kathodischen polarisierten Graphit-Indikatorelektrode wurde zur Bestimmung des Quecksilbers bzw. der Organoquecksilberverbindung in einigen pharmazeutischen Produkten benützt. Das Ce(IV)-As(III)-System in Anwesenheit von Schwefelsäure wurde zur Indikation benützt. Diese Indikatorreaktion wird von dem Überschuß an Kaliumjodid katalysiert. Besondere Aufmerksamkeit wurde der Vorbereitung der Proben zugewandt. Die Ergebnisse stimmen gut mit denen vergleichbarer Methoden überein.

---

---

Presented at the 8th International Microchemical Symposium, Graz, August 25–30, 1980.     

Reactions SRN1 en serie heterocyclique: IV: Reactivite des sels du dimethyl-2,2 nitro-5 dioxanne-1,3

2-Alkyl 2-nitro 1,3-propanediol, 2-alkylidene 1,3-propanediol and 2-dialkylidene 1,3-propanediol are prepared via S_RN1 reactions with salts of 2,2-dimethyl 5-nitro 1,3-dioxane and acid-catalyzed cleavage of the resulting acetals.     

Biamperometric end-point detection with quinhydrone electrodes in coulometric neutralization titrations in nonaqueous media

Some new possibilities for continuous coulometric titration of bases, alone and in mixture, as well as of mineral acids, alone and in mixture, were investigated with acetic anhydride-anhydrous acetic acid as solvents. The titration end point was determined biamperometrically. It was established that quinhydrone electrodes with platinum, palladium, and gold as the metal phase can be equally satisfactorily applied to the end-point determination of both the titrations of bases or acids alone, and of their two-component mixtures. Amounts of 6–10 μequiv. of bases, i.e., 20–47 μequiv. of mineral acids, were determined with the maximal average deviation of 1.4%. Results of biamperometric determinations of bases are compared to those of catalytic thermometric determinations, while those of acids are compared with the results of photometric titrations. The agreement between the methods is satisfactory.     

On the relationship between the structures of Cu(II) complexes and their chemical transformations

The paper deals with the relationship between the crystal and molecular structures of CuSO₄.5 H₂O, CuSO₄.3 H₂O and CuSO₄.H₂O on the one hand, and the stoichiometries of their thermal decompositions on the other. With the use of methods of X ray powder diffractograms, i.r. and electronic spectra, evidence is provided that the intermediates of the thermal decomposition of CuSO₄.5 H₂O have the same crystal and molecular structures as CuSO₄.3 H₂O and CuSO₄.H₂O prepared by other procedures. It is also shown that at temperatures near that of the thermal decomposition, certain, not further identified structural changes take place in CuSO₄.5 H₂O.

---

Zusammenfassung Es wird einerseits der Zusammenhang der Kristall- und Molekularstruktur von CuSO₄ · 5H₂O, CuSO₄ · 3H₂O und CuSO₄ · H₂O behandelt und andererseits die Stöchiometrie ihrer thermischen Zersetzung. Mit der Auswertung der Röntgen-Pulverdiffraktogramme, der IR- und Elektronenspektren wurde der Beweis erbacht, da\ die Zwischen-produkte der thermischen Zersetzung von CuSO₄ · 5H₂O dieselben Kristall- und Molekül-strukturen besitzen, wie auf anderen Wegen hergestelltes CuSO₄ · 3H₂O bzw. CuSO₄ · H₂O. Ferner wurde gezeigt, da\ bei Temperaturen in der NÄhe der thermischen Zersetzungstemperatur gewisse, jedoch noch nicht identifizierte StrukturÄnderungen in dem CuSO₄ · 5H₂O stattfinden.

---

Résumé L'article examine la corrélation entre les structures cristallines et moléculaires de CuSO₄.5 H₂O, CuSO₄.3 H₂O et CuSO₄.H₂O d'une part et la stoechiométrie de leur décomposition thermique de l'autre. En se servant des méthodes des diffraction des rayons X sur poudre et des spectres infra-rouges et électroniques on montre que les produits intermédiaires de la décomposition thermique de CuSO₄.5 H₂O ont les mÊmes structures cristallines et moléculaires que celles de CuSO₄.3 H₂O et de CuSO₄.H₂O préparées par d'autres procédés. On montre également qu'à des températures proches de celle de la décomposition thermique de CuSO₄. 5H₂O des changements structuraux non encore identifiés ont lieu.

---

uSO₄ · 5₂, uSO₄ · ₂ uSO₄ · ₂, — . , , , uSO₄ · 5₂ uSO₄ · ₂ uSO₄ · ₂, . , , uSO₄, · 5₂ , .

     

Generation and use of an equivalent of difluoroacetamide or difluoroacetate anions

Ethers of trifluoroacetaldehyde hemiaminals can undergo dehydrofluorination under basic conditions to provide ethers of difluoroketene hemiaminals. The latter behave as equivalents of difluoroacetamide or difluoroacetate anions towards various electrophiles, yielding a range of difluoromethylcarbonyl products.     

Determination of fluoride with thorium nitrate by catalytic titration

Amperometry, constant-current potentiometry and spectrophotometry were used to follow the course of catalytic titrations of fluoride and silicofluoride with thorium nitrate. The hydrogen peroxide-iodide system was used as the indicator reaction. Titrations were performed in 50% ethanolic acetate buffer, pH 3.6. Amounts of 3.70-6.85 mg of ammonium fluoride, 5.53-10.79 mg of potassium fluoride and 4.34-8.41 mg of sodium silicofluoride were determined with a maximum average deviation of 0.9%. The results obtained are in good agreement with those of comparable methods.     

Contributions to the theory of catalytic titrations-III Neutralization catalytic titrations

Neutralization catalytic titrations of weak monoprotic adds and bases with both volumetric and coulometric addition of the titrant (strong base/acid) have been simulated by taking into account the equilibrium concentration of the catalyst during the titration. The influence of several factors on the shape of the simulated catalytic titration curve has been investigated and is discussed.