Nachweis von Oxoverbindungen. IV

Zusammenfassung Enolisierende Oxoverbindungen, die eine - CH₂-CO- oder eine- CO-NH-NH-Gruppe enthalten, geben mit Diazoniumsalz eine Farbreaktion. Formaldehyd, Benzaldehyd, Nitrobenzaldehyde, Benzoin, Benzophenon usw. reagieren dabei nicht. 1,3-Diketone geben mit diazotiertem p-Nitroanilin zweierlei Färbungen, bei geringer Diazoniumsalzkonzentration eine rote, bei großem Überschuß eine blaue oder grüne Färbung. Die Reaktionsgeschwindigkeit ändert sich auch nach der Art des Diazoniumsalzes. Mit dieser Methode wurden selektive Nachweise für Oxoverbindungen ausgearbeitet. Acetonspuren können in Äthanol bzw. in Wasser oder in Methyläthylketon mit diazotiertem Anilin, 10^–3 % Acetessigsäureäthylester in Äthylacetat mit diazotiertem p-Phenetidin, 10^–5 % Acetylaceton in Aceton mit diazotiertem p-Nitroanilin, außerdem Acetaldehyd neben Formaldehyd, Acetylphenylhydrazin neben Acetanilid, mbzw. o- neben p-Nitroanilin nachgewiesen werden. Nach dem Absorptionsspektrum erwies sich das Reaktionsprodukt von Aceton mit diazotiertem p-Nitroanilin als eine Azoverbindung.

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Detection of Oxocompounds. IV

Summary Enolizing oxo-compounds, that contain a -CH₂-CO- or a -CO-NH-NH-group, yield a color reaction with diazonium salt. Formaldehyde, benzaldehyde, nitrobenzaldehyde, benzoin, benzophenone etc. however do not show this reaction. 1,3-diketones yield two kinds of color reactions with diazotizedp-nitraniline; a slight diazonium salt concentration yields a red coloration, while a large excess gives a blue or green coloration. Selective detections for oxo-compounds were developed with this method. Traces of acetone may be detected in ethanol or water or in methylethyl ketone by means of diazotized aniline, 10^–3% of acetoacetic ester can be detected in ethyl acetate by means of diazotizedp-phenetidine, 10^–5% acetylacetone in aldehyde, acetylphenylhydrazine in the presence of acetanilide,m- oro- in the presence ofp-nitraniline. Judging from the absorption spectrum, the reaction product from acetone and diazotizedp-nitraniline is an azo compound.

     

Eine neue Endpunktindikation der Diazotitration

Zusammenfassung Eine Endpunktindikation bei der Diazotitration primärer aromatischer Amine, die nicht auf Oxydation, sondern auf der Diazotierungswirkung des Natriumnitrits beruht, wird beschrieben. Der Indicator ist ein Azofarbstoff, der eine diazotierbare primäre Aminogruppe enthält und in saurem Medium auch in sehr niedriger Konzentration eine intensive Earbe hat. Im Äquivalenzpunkt wird durch einen Tropfen der zu prüfenden Lösung die Indicatorlösung entfärbt. Als Indicator dient 4-(2-Äthyl-phenylazo)-1-naphthylamin-hydrochlorid.

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Summary A new end-point indication for the diazo titration of primary aromatic amines has been proposed. It is not based on oxidation, but on the diazotising effect of sodium nitrite. The indicator is an azo dye containing a primary amine group and having an intense colour in acid solution, also in very small concentrations. The end-point is determined by bringing a drop of the test solution containing sodium nitrite into contact with the dye solution and is recognised by the diseappearing of the colour. The indicator dye applied is 4-(2-ethyl-phenylazo)-1-naphthylamino hydrochloride.

     

A re-statement of the Hohenberg–Kohn theorem and its extension to finite subspaces

Bearing in mind the insight into the Hohenberg–Kohn theorem for Coulomb systems provided recently by Kryachko (Int J Quantum Chem 103:818, 2005), we present a re-statement of this theorem through an elaboration on Lieb’s proof as well as an extension of this theorem to finite subspaces. Contribution to the Serafin Fraga Memorial Issue.     

DNase activity ofMicrococcal endonuclease insolubilized on corn cob

The endonuclease from S. aureus has been immobilized on ground maize cob, previously activated with tosyl chloride. Pretreatment of the support on acid before tosylation yielded the best insoluble enzyme derivatives. The catalytic activity has been evaluated as percent of total hydrolysis attained in a batch reactor using DNA as a model substrate. The derivatives prepared are very resistant to high temperatures under conditions of catalysis (24 h at 45 degrees C). For these long reaction times, the extent of hydrolysis in the presence of small amounts of organic solvent (dimethyl sulfoxide at 2 percent) is larger than in plain buffer (Tris). This type of derivative could be very useful for the removal of nucleic acids from single-cell protein concentrates.     

Nachweis von Peroxiden,Hydroperoxiden und Persäuren

Zusammenfassung Die Indikatorbase 4-Methoxyphenylazo--naphthylamin wird von p-Nitrobenzoylperoxid in neutralem oder saurem Medium ohne, von p-Nitrobenzopersäure unter Erwärmen oxydiert, gar nicht aber von p-Nitroäthylbenzol--hydroperoxid. Auf der Grundlage dieses Verhaltens können die drei Verbindungen unterschieden und p-Nitrobenzoylperoxid nachgewiesen werden. Die Indikatorsäure 4-Nitrophenylazo-2-amino-5-nitrobenzol wird von p-Nitroäthylbenzol--hydroperoxid oxydiert, nicht aber von p-Nitrobenzoylperoxid und p-Nitrobenzopersäure. Mit dieser Farbreaktion kann p-Nitroäthylbenzol--hydroperoxid nachgewiesen werden. p-Nitrobenzopersäure kann neben p-Nitroäthylbenzolhydroperoxid mit einer Farbreaktion von p- + m-Phenylendiamin nachgewiesen werden. Auch p-Nitrobenzoylperoxid gibt die Reaktion, aber p-Nitroäthylbenzol--hydroperoxid setzt sich nicht um.

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Detection of peroxides, hydroperoxides, and peracids

Summary The indicator base 4-methoxyphenylazo--naphthylamine is oxidized in neutral medium without warming byp-nitrobenzoyl peroxide, and byp-nitrobenzoperacid with warming, but it is not oxidized at all byp-nitroethylbenzene--hydroperoxide. The three compounds may be differentiated on the basis of these behaviors and furthermore it is thus possible to detect and identifyp-nitrobenzoyl peroxide. The indicator acid 4-nitrophenylazo-2-amino-5-nitrobenzene is oxidized byp-nitroethylbenzene--hydroperoxide but not byp-nitrobenzoyl peroxide andp-nitrobenzoperacid.p-Nitroethylbenzene--hydroperoxide may be detected through this color reaction.p-Nitrobenzoperacid can be detected in the presence ofp-nitroethylbenzene--hydroperoxide by a color reaction withp + m-phenylenediamine but no reaction is given byp-nitroethylbenzene--hydroperoxide.

     

Pozzolanic properties of a residual FCC catalyst during the early stages of cement hydration

The catalyst used in fluidized catalytic cracking (FCC) units of refineries after several recovery cycles in regeneration units, reduces its activity and it is partially substituted by new catalyst in the process. As it has a high silicon and aluminum oxides content, the pozzolanic properties of a Brazilian FCC spent residual catalyst, used in different substitution degrees to cement, were evaluated by three thermal analysis techniques during the early stages of hydration of a type II Portland cement. NCDTA curves show in real time that the residual catalyst, accelerates the stages of cement hydration. TG and DSC curves of respective pastes after 24 h of hydration evidence the pozzolanic activity of the waste, respectively, by the lower water mass loss during the dehydroxylation of the residual calcium hydroxide and by the lower dehydroxylation endothermal effect. Within the analyzed period, the higher is the cement substitution degree, the higher is the pozzolanic activity of the residual catalyst.     

Sorption behavior of Co(II) on γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> in the presence of humic acid

The fate and transport of toxic metal ions and radionuclides in the environment is generally controlled by sorption reactions. The extent of sorption of divalent metal cations is controlled by a number of factors including cosorbing or complexing. In this work, the effects of pH, humic acid HA/Co(II) addition orders, ionic strength, concentration of HA, and foreign cations on the Co(II) sorption on γ-Al₂O₃ in the presence of HA were investigated. The sorption isotherms of Co(II) on γ-Al₂O₃ in the absence and presence HA were also studied and described by using S-type sorption model. The experimental results showed that the Co(II) sorption is strongly dependent on the pH values, concentration of HA, but independent of HA/Co(II) addition orders, ionic strength, and foreign cations in the presence of HA under our experimental conditions. The results also indicated that HA enhanced the Co(II) sorption at low pH, but reduced the Co(II) sorption at high pH. It was hypothesized that the significantly positive influence of HA at low pH on the Co(II) sorption on γ-Al₂O₃ was attributed to strong surface binding of HA on γ-Al₂O₃ and subsequently the formation of ternary surface complexes such as ≡S-OOC-R-(COO⁻) _x Co^2−x . Chemi-complexation may be the main mechanism of the Co(II) sorption on γ-Al₂O₃ in the presence of HA.     

珊瑚中硼的分离及其同位素组成的测定

介绍了用硼特效树脂和阴、阳混合离子交换树脂相结合进行珊瑚中硼的分离和纯化方法，满足了正热电离质谱法测定硼同位素的要求，并且对几个珊瑚样品进行了硼的分离和硼同位素组成的测定，结果满意，为研究珊瑚中的硼同位素示踪古海洋环境变化提供了可能。     

Preconcentration and separation of copper(II), cadmium(II) and chromium(III) in a syringe filled with 3-aminopropyltriethoxysilane supported on silica gel

In this study, a syringe was filled with silica gel loaded with 3-aminopropyltriethoxysilane, for the separation and preconcentration of copper, cadmium and chromium prior to their determination by graphite furnace atomic absorption spectrometry (GFAAS) in seawater. For this purpose, a syringe was filled with 0.5 g of modified silica gel and the sample solution was drawn into the syringe and ejected back again. The analyte elements were quantitatively retained at pH 5. Then, the elements sorbed by the silica gel were eluted with 2.0 M of HCl and determined by GFAAS. At optimum conditions, the recovery of Cu, Cd and Cr were 96-98%. Detection limits (3delta) were 6.6, 7.5 and 6.0 micro g L(-1) for Cu, Cd and Cr, respectively. The elements could be concentrated by drawing and discharging several portions of sample successively but eluting only once. Cu, Cd and Cr added to a seawater sample were quantitatively recovered (>95%) in the range of the 95% confidence level. The method proposed in this paper was compared with a column technique. Optimum experimental conditions, reproducibility, precision and recoveries of both techniques are the same, but the syringe technique is much faster, easier and more practical than the column technique. It is a portable system and allows one to make the sorption process in the source of sample. In addition, the risk of contamination is less than in the column technique.     

Borate adsorption at Pt(111) in acidic medium

The adsorption/desorption process of borate was studied at Pt(111) in acidic solution by cyclic voltammetry. A so-called butterfly wave in the cyclic voltammogram of Pt(111) in HClO₄ shifted to negative direction upon the addition of boric acid with the disappearance of its sharp spikes. The shift in potential was found to be −57 mV with a tenfold increase of boric acid concentration. This illustrates that this anomalous wave is due to borate adsorption/desorption by a one-electron transfer process. The borate adsorption/desorption wave was observed to shift by −63 mV/pH. At pH>3, the anomalous wave splits forming two separate waves, depending on the pH and the scan rate. The appearance of two waves is assigned to the change in the adsorption mode of borate or the participation of OH in the adsorption process.