Addition Of NaNO2 Research Articles

Stress response of Salmonella enterica serovar typhimurium to acidified nitrite.

The antimicrobial action of the curing agent sodium nitrite (NaNO2), which is added as a preservative to raw meat products, depends on its conversion to nitric oxide and other reactive nitrogen species under acidic conditions. In this study, we used RNA sequencing to analyze the acidified-NaNO2 shock and adaptive responses of Salmonella enterica serovar Typhimurium, a frequent contaminant in raw meat, considering parameters relevant for the production of raw-cured sausages. Upon a 10-min exposure to 150 mg/liter NaNO2 in LB (pH 5.5) acidified with lactic acid, genes involved in nitrosative-stress protection, together with several other stress-related genes, were induced. In contrast, genes involved in translation, transcription, replication, and motility were downregulated. The induction of stress tolerance and the reduction of cell proliferation obviously promote survival under harsh acidified-NaNO2 stress. The subsequent adaptive response was characterized by upregulation of NsrR-regulated genes and iron uptake systems and by downregulation of genes involved in anaerobic respiratory pathways. Strikingly, amino acid decarboxylase systems, which contribute to acid tolerance, displayed increased transcript levels in response to acidified NaNO2. The induction of systems known to be involved in acid resistance indicates a nitrite-mediated increase in the level of acid stress. Deletion of cadA, which encodes lysine decarboxylase, resulted in increased sensitivity to acidified NaNO2. Intracellular pH measurements using a pH-sensitive green fluorescent protein (GFP) variant showed that the cytoplasmic pH of S. Typhimurium in LB medium (pH 5.5) is decreased upon the addition of NaNO2. This study provides the first evidence that intracellular acidification is an additional antibacterial mode of action of acidified NaNO2.

Persistence of Bacteroides ovatus under simulated sunlight irradiation.

BackgroundBacteroides ovatus, a member of the genus Bacteroides, is considered for use in molecular-based methods as a general fecal indicator. However, knowledge on its fate and persistence after a fecal contamination event remains limited. In this study, the persistence of B. ovatus was evaluated under simulated sunlight exposure and in conditions similar to freshwater and seawater. By combining propidium monoazide (PMA) treatment and quantitative polymerase chain reaction (qPCR) detection, the decay rates of B. ovatus were determined in the presence and absence of exogenous photosensitizers and in salinity up to 39.5 parts per thousand at 27°C.ResultsUVB was found to be important for B. ovatus decay, averaging a 4 log10 of decay over 6 h of exposure without the presence of extracellular photosensitizers. The addition of NaNO2, an exogenous sensitizer producing hydroxyl radicals, did not significantly change the decay rate of B. ovatus in both low and high salinity water, while the exogenous sensitizer algae organic matter (AOM) slowed down the decay of B. ovatus in low salinity water. At seawater salinity, the decay rate of B. ovatus was slower than that in low salinity water, except when both NaNO2 and AOM were present.ConclusionThe results of laboratory experiments suggest that if B. ovatus is released into either freshwater or seawater environment in the evening, 50% of it may be intact by the next morning; if it is released at noon, only 50% may be intact after a mere 5 min of full spectrum irradiation on a clear day. This study provides a mechanistic understanding to some of the important environmental relevant factors that influenced the inactivation kinetics of B. ovatus in the presence of sunlight irradiation, and would facilitate the use of B. ovatus to indicate the occurrence of fecal contamination.

Quenching of tribo- and photoluminescence in a Tb2(SO4)3 · 8H2O + NaNO2 crystalline mixture

It is found that the addition of NaNO2 to Tb2(SO4)3 · 8H2O crystals quenches tribo- and photo-luminescence from the latter. In the case of triboluminescence, the glow of both Tb3+* ions (solid component of triboluminescence) and N2* molecules (gas component) is quenched. The NO2− ion is known to be an efficient quencher of Tb3+ ion luminescence by the mechanism of radiationless energy transfer in solutions. That quenching takes place when a crystalline quencher is in contact with a crystalline phosphor and also with a gaseous (molecular) phosphor seems to indicate that the excitation energy is transferred not only within individual crystals but also between contacting surfaces of the phosphor and quencher and at the gas-solid interface.

Evaluation of N-Nitrosopiperidine Formation from Biogenic Amines During the Production of Dry Fermented Sausages

The aim of this study was to determine the role of the precursors cadaverine (CAD) and piperidine in N-nitrosopiperidine (NPIP) formation during the production of dry fermented sausages. The influences of pH (4.9 and 5.3), sodium nitrite (0 and 150 mg/kg), and ascorbate (0 and 500 mg/kg) were investigated by the use of a dry fermented sausage model. The biogenic amines and volatile N-nitrosamines were analyzed by HPLC-UV and GC-TEA. The major biogenic amines were tyramine, putrescine, and CAD, but their accumulation could be inhibited by NaNO2. When no amine precursors were artificially added, no meaningful N-nitrosamine contamination was observed. The artificial addition of 500 mg/kg cadaverine dihydrochloride (CAD·2HCl) could not provoke increased N-nitrosamine formation. In contrast, the addition of PIP (10 and 100 mg/kg) resulted in higher NPIP concentrations. No influence of pH was observed, but the NPIP formation was more pronounced when NaNO2 was added and sodium ascorbate was excluded from the formulation. The role of ascorbate as N-nitrosamine scavenger was only detectable during the early stage of production. In the end products, NPIP was degraded and the levels were no longer influenced by the initial addition of NaNO2 or ascorbate.

Effects of TiO2 nanoparticles on the NO2 − levels in cell culture media analysed by Griess colorimetric methods

The Griess assay has been used to determine the possible changes in the measured NO2− concentrations induced by TiO2 nanoparticles in three types of nitrite-containing samples: aqueous NaNO2 solutions with known concentrations, and two types of cell culture media—Roswell Park Memorial Institute medium (RPMI-1640) and Dulbecco’s Modified Eagle Medium (DMEM-F12) used either as delivered or enriched in NO2− by NaNO2 addition. We have used three types of titania with average particle sizes between 10 and 30 nm: Degussa P25 and two other samples (undoped and Fe3+-doped anatase TiO2) synthesised by a hydrothermal route in our laboratory. The structural, morphological, optical and physicochemical characteristics of the used materials have been studied by X-ray diffraction, transmission electron microscopy (EDX), Mossbauer spectroscopy, Brunauer–Emmett–Teller nitrogen adsorption, UV–Vis reflectance spectroscopy, dynamic light scattering and diffuse reflectance infrared Fourier transform spectroscopy. The opacity and sedimentation behaviour of the studied TiO2 suspensions have been investigated by photometric attenuance measurements at 540 nm. To account for the photocatalytic properties of titania in a biologically relevant context, multiple Griess tests have been performed under controlled exposure to laboratory natural daylight illumination. The results show significant variations of light attenuance (associated with NO2− concentrations in the Griess test) depending on the opacity, sedimentation behaviour, NO2− adsorption and photocatalytic properties of the tested TiO2 nanomaterials. These findings identify material characteristics recommended to be considered when analysing the results of Griess tests performed in biological studies involving TiO2 nanoparticles.

Surface coverage determination of iron-phosphate coatings on steel using voltammetric anodic dissolution technique

In this study, the effect of deposition time and concentration of NaNO2 in the phosphate bath on the surface morphology of iron-phosphate coatings on low carbon steel was investigated using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The composition of iron-phosphate coatings was determined using energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD), while surface coverage was evaluated by the voltammetric anodic dissolution (VAD) technique in the borate solution. The addition of NaNO2 in the phosphate bath significantly increased the surface coverage since better packed crystals of smaller size, which favour the phosphate nucleation, were obtained. It was also shown that prolonged deposition time increased the surface coverage, coating roughness and crystal size in lateral direction, altering also the crystal shape from big platelets nonuniformly distributed on steel surface during initial time, to better packed laminated and needle-like structures during prolonged exposure.

Neuroprotection by Minocycline Caused by Direct and Specific Scavenging of Peroxynitrite

Minocycline prevents oxidative protein modifications and damage in disease models associated with inflammatory glial activation and oxidative stress. Although the drug has been assumed to act by preventing the up-regulation of proinflammatory enzymes, we probed here its direct chemical interaction with reactive oxygen species. The antibiotic did not react with superoxide or (•)NO radicals, but peroxynitrite (PON) was scavenged in the range of ∼1 μm minocycline and below. The interaction of pharmacologically relevant minocycline concentrations with PON was corroborated in several assay systems and significantly exceeded the efficacy of other antibiotics. Minocycline was degraded during the reaction with PON, and the resultant products lacked antioxidant properties. The antioxidant activity of minocycline extended to cellular systems, because it prevented neuronal mitochondrial DNA damage and glutathione depletion. Maintenance of neuronal viability under PON stress was shown to be solely dependent on direct chemical scavenging by minocycline. We chose α-synuclein (ASYN), known from Parkinsonian pathology as a biologically relevant target in chemical and cellular nitration reactions. Submicromolar concentrations of minocycline prevented tyrosine nitration of ASYN by PON. Mass spectrometric analysis revealed that minocycline impeded nitrations more effectively than methionine oxidations and dimerizations of ASYN, which are secondary reactions under PON stress. Thus, PON scavenging at low concentrations is a novel feature of minocycline and may help to explain its pharmacological activity.

Acidified nitrite enhances hydrogen peroxide disinfection of Acanthamoeba, bacteria and fungi

In the human innate immune system, stimulated phagocytes release reactive nitrogen intermediates that can react with superoxide to form the powerful oxidant peroxynitrite and other less abundant species. In this study, the efficacy of hydrogen peroxide (H2O2) and acidified nitrite (NaNO2) alone and in combination was compared against a variety of bacteria, fungi and protozoa. Challenge test assays based on the international standard (ISO 14729) were used to determine the antimicrobial activity of H2O2 and acidified NaNO2 at pH 5 alone and in combination against Pseudomonas aeruginosa, Serratia marcescens, Staphylococcus aureus, Mycobacterium aurum, Bacillus subtilis spores, Candida albicans, Fusarium solani conidia and Acanthamoeba polyphaga trophozoites and cysts. When tested alone, both H2O2 (0.4% v/v) and NaNO2 (2 mg/mL, pH 5) produced a >or=4 log reduction in viability after 4 h of exposure for all bacteria and A. polyphaga trophozoites, but not B. subtilis spores, F. solani and A. polyphaga cysts, which gave a <or=1 log kill after 6 h, and M. aurum, which gave a <1 log kill with NaNO2 only. However, the combination of H2O2 and NaNO2 resulted in a >or=4 log kill of all test organisms within 1 h. Addition of NaNO2 also enhanced the antimicrobial efficacy of a H2O2-based contact lens disinfection system. The findings of this study demonstrate that acidified NaNO2 can significantly enhance the antimicrobial activity of H2O2 probably through the generation of peroxynitrite. The addition of acidified nitrite to 3% (v/v) H2O2 solution may represent an improved one-step method for the disinfection of contact lenses, especially against highly resistant cysts of Acanthamoeba spp.

Reduction and turbulence characteristics in sub-zero temperature range of cationic and zwitterionic surfactants in EG/water solvent

The addition of small amounts of surfactant to a solvent in turbulent flow can reduce friction drag greatly. A new approach to energy savings in district cooling systems is to use surfactant solutions at subzero temperatures as the cooling fluids. In this paper, experiments were conducted to study the drag-reduction performances of a commercial cationic surfactant solution (oleylmethylbiss-hydroxyethyl ammonium chloride) and a newly synthesized zwitterionic surfactant solution (oleyl trimethylaminimide) in a two-dimensional channel. For testing the drag reduction at subzero temperatures, for which little data have been reported and none in channel flow, a 20% ethylene glycol aqueous solution (EG/W) was used as a solvent. The surfactant concentration ranged from 50 to 1000 ppm and the temperatures were –5 and 25°C. The turbulence features of the surfactant drag-reducing flow were measured by using the PIV (particle image velocimetry) technique. It was found that both surfactant solutions showed drag-reducing characteristics, which were affected by concentration and temperature. The maximum drag reduction was 83% at 25°C for the 200 ppm zwitterionic surfactant solution. Compared with EG/W turbulent flow, the addition of surfactant suppressed the turbulent intensities and vortex fluctuations and the Reynolds stresses were zero. The effects of addition of NaNO2 to the surfactant solutions were also investigated.

Carbon-Nanotube-Enhanced Direct Electron-Transfer Reactivity of Hemoglobin Immobilized on Polyurethane Elastomer Film

In this study, we investigate the direct electron-transfer reactivity of immobilized hemoglobin (Hb) on a polyurethane elastomer (PUE) film for biosensor designs. The PUE film synthesized by an additional polymerization possesses good biocompatibility, uniformity, and conformability and is ready for protein immobilization. Electrochemical and spectroscopic measurements show that the presence of multiwalled carbon nanotubes (MWNTs) increased the protein-PUE interaction, varied polymer morphology, improved the permeability and the conductivity of the PUE film, and thus facilitated the direct electron transfer between the immobilized Hb and the conductivity surface through the conducting tunnels of MWNTs. The immobilized Hb maintains its bioactivities and displays an excellent electrochemical behavior with a formal potential of -(334 +/- 7) mV. The addition of NaNO2 leads to an increase of the electrocatalytic reduction current of nitrite at -0.7 V. This allows us to develop a nitrite sensor with a linear response range from 0.08 to 3.6 mM. The proposed method opens a way to develop biosensors by using nanostructured materials mixed with low electrical conductivity matrixes.

Radiochemical determination of 237Np in soil samples contaminated with weapon grade plutonium

The Palomares terrestrial ecosystem (Spain) constitutes a natural laboratory to study transuranics. This scenario is partially contaminated with weapon-grade plutonium since the burnout and fragmentation of two thermonuclear bombs accidentally dropped in 1966. While performing radiometric measurements in the field, the possible presence of 237Np was observed through its 29 keV gamma emission. To accomplish a detailed characterization of the source term in the contaminated area using the isotopic ratios Pu-Am-Np, the radiochemical isolation and quantification by alpha spectrometry of 237Np was initiated. The selected radiochemical procedure involves separation of Np from Am, U and Pu with ionic resins, given that in soil samples from Palomares 239+240Pu levels are several orders of magnitude higher than 237Np. Then neptunium is isolated using TEVA organic resins. After electrodeposition, quantification is performed by alpha spectrometry. Different tests were done with blank solutions spiked with 236Pu and 237Np, solutions resulting from the total dissolution of radioactive particles and soil samples. Results indicate that the optimal sequential radionuclide separation order is Pu-Np, with decontamination percentages obtained with the ionic resins ranging from 98 % to 100 %. Also, the addition of NaNO2 has proved to be necessary, acting as a stabilizer of Pu-Np valences.

Stoichiometric and Catalytic Secondary O-Atom Transfer by Fe(III)−NO2 Complexes Derived from a Planar Tetradentate Non-heme Ligand: Reminiscence of Heme Chemistry

An Fe(III) nitro complex [(bpb)Fe(NO2)(py)] (2) of the tetradentate ligand 1,2-bis(pyridine-2-carboxamido)benzene (H2bpb, H is the dissociable amide proton) has been synthesized via addition of NaNO2 to [(bpb)Fe(py)2](ClO4) (1) in MeCN or DMF. This structurally characterized Fe(III) nitro complex exhibits its nuNO2 at 1384 cm(-1). The reaction of 1 with 2 equiv of Et4NX (X = Cl-, Br-) affords the high-spin complexes (Et4N)[(bpb)Fe(Cl2)] (3) and (Et4N)[(bpb)Fe(Br)2] (4), respectively. The structure of 4 has been determined. The addition of an equimolar amount of Et4NCl, Et4NBr, or Et4NCN to a solution of 2 affords the mixed-ligand complexes (Et4N)[(bpb)Fe(NO2)(Cl)] (5), (Et4N)[(bpb)Fe(NO2)(Br)] (6), and (Et4N)[(bpb)Fe(NO2)(CN)] (7), respectively. These complexes are all low spin with isotropic g values of 2.15. Under anaerobic conditions, the reactions of 5-7 with Ph3P in MeCN afford the five-coordinate {Fe-NO}7 nitrosyl [(bpb)Fe(NO)] (and Ph3PO) via secondary oxygen-atom (O-atom) transfer. The O-atom transfer to Ph3P by 5-7 becomes catalytic in the presence of dioxygen with transfer rates in the range of 1.70-13.59 x 10-3 min(-1). The O-atom transfer rates and turnover numbers (5 > 6 > 7) are reflective of the strength of the axial donors (Cl- > Br- > CN-). The catalytic efficiencies of complexes 5-7 are limited due to formation of the thermodynamic end products [(bpb)Fe(X)2]- (where X = Cl- for 5, Br- for 6, and CN- for 7).

Application of the Bismuth Film Electrode for Catalytic Adsorptive Stripping Potentiometric Determination of Cobalt in Dimethylglyoxime‐Nitrite System

The application of bismuth film electrodes to the determination of cobalt by constant current adsorptive stripping potentiometry with exploitation of a catalytic effect is presented. The addition of NaNO2 to the solution containing ammonia buffer and dimethylglyoxime results in a 25‐fold enhancement of the adsorptive stripping potentiometric cobalt signal. Several key parameters of the potentiometric stripping mode were optimized, including the composition of the supporting electrolyte, the stripping current, the accumulation potential, and the accumulation time. The optimized procedure yields favorable and highly stable stripping responses with good precision (RSD=1.4% for a Co concentration of 2 µg L−1), low detection limit (0.07 µg L−1), and good linearity (up to 10 µg L−1, R2=0.998) with a deposition time of 60 s and a stripping current of 10 µA. The method enables the determination of Co in the presence of high excesses of Ni or Zn.

Study on Catalytic Adsorptive Stripping Voltammetry of Trace Cobalt at Bismuth Film Electrodes

AbstractBismuth film electrodes (BiFE) prepared by plating a glassy carbon support ex situ from a solution containing 0.5 M LiBr and 1 M HCl was tested for the determination of cobalt traces using adsorptive stripping voltammetry (AdSV) and catalytic adsorptive stripping voltammetry (CAdSV). AdSV enables one to determine cobalt as the Co(II)‐dimethylglyoximate (Co‐DMG) complex down to 0.3 μg/L Co. Addition of NaNO2 to the solution containing dimethylglyoxime in ammonia buffer provides a 15‐fold enhancement of the voltammetric signal of cobalt due to the catalytic effect occurring during the reduction of Co(II)‐DMG. Utilization of the bismuth film electrode under optimized conditions assures a stable catalytic adsorptive stripping voltammetric response for Co, with an extremely high sensitivity (1.75 μA/(μg/L)), good precision (RSD=3%), and a low detection limit (0.07 μg/L Co with 60 s of adsorptive accumulation). The results of the measurement of the catalytic cobalt response in the presence of DMG and nitrite under hydrodynamic amperometric conditions have shown the BiFE to be an attractive and suitable tool for the rapid determination of cobalt at low μg/L level in both batch and flow systems.

The acute toxicity and sublethal effects of nitrite on growth and feed utilization of European eel, Anguilla anguilla (L.)

Eels cultured in recirculation systems are regularly confronted with high concentrations of nitrite, a well-known toxicant for fish. In this study, the acute toxicity of nitrite to European eel, Anguilla anguilla (L.), was assessed by determination of a 96-h LC50. The 96-h LC50 measured for eels was 143.7 ± 2.3 gm-3 NO2-N (mean SD), which is high compared with the LC50 for other fish species. The sublethal effects of nitrite on growth and feed utilization were evaluated in a feeding trial lasting 77 days, divided into an acclimation period and two experimental periods. Eels of 24 g on average were divided over 20 aquaria, connected to five separate recirculation systems. In each system, the desired nitrite concentration level was maintained by water suppletion and continuous addition of NaNO2. Fish were continuously exposed to levels of 0, 1, 5, 10 or 20 g m-3 NO2-N. Half of the experimental groups were fed ad libitum to study effects on feed intake, while the other half were fed a restricted ration to study effects on feed utilization. At the start and end of each experimental period, nitrite in the blood plasma, haemoglobin and methaemoglobin were measured. Fish weight and body composition were used to calculate specific growth rate and conversion efficiencies. In the range of concentrations studied, no significant effect of nitrite on maximum growth rate or feed utilization could be demonstrated. At the start of the experiment, low concentrations of nitrite were detected in the blood plasma, which suggests an ability of the eel to adapt to environmental nitrite. Nitrite, in the range normally encountered in intensive eel farms (max. 15 g m-3 NO2-N), can therefore be considered a factor of little significance.

Development of a chitin assay for the quantification of fungus.

Chitin, a unique structural polysaccharide found in fungi and arthropods, is not produced by vertebrates. Thus, the potential applications of a specific and sensitive assay for chitin are numerous, including the evaluation of the extent of fungal keratitis. Chitin is a homopolymer of beta (1, 4) linked D-N-acetylglucosamine. We have developed a simple and reproducible assay for chitin and applied it to Candida albicans cultures. The assay involves homogenization of the culture and treatment with 21.1 M KOH to remove soluble materials, including proteins. This base treatment also deacetylates the chitin to the glucosamine polymer, chitosan. Chitosan is hydrolyzed by 0.5 M H2SO4 to glucosamine monomers which are then deaminated by the addition of NaNO2 to the acid solution. The resulting 2,5-anhydromannose is reduced by NaB[3H]4 to 1-[3H] 2,5-anhydromannitol. This radiolabelled sugar is isolated by paper chromatography and quantified via liquid scintillation. The sensitivity of this assay is assessed by comparison of colony forming units (CFU's) with a glucosamine standard. A typical run of the assay detects 53.1 CFU/c.p.m., and 356,000 c.p.m. per nanomole of N-acetylglucosamine. The specificity of the assay is very high because of the unique nature of chitin. This method of chitin determination may be a useful alternative method for future investigations involving the study of fungal infections in mammalian tissues.

Catalytic spectrofluorimetric determination of copper using aerial oxidation of ascorbic acid in the presence of o-phenylenediamine

Copper-catalysed aerial oxidation of L-ascorbic acid to dehydroascorbic acid (DAA) was sensitively monitored by fluorimetric detection (λex= 350 nm; λem= 425 nm) of quinoxaline derivatives (QX) formed by the successive reaction of DAA with o-phenylenediamine. The fluorescence intensity (I) was proportional to the square of the reaction time (t) in the initial reaction at pH 6.9 and 25 °C. Using the slope of the I versus t2 graph, a calibration graph for copper was constructed with a linear range from 0 to 8 µg l–1. The detection limit was 0.06 µg l–1. The interference from HgII, CrVI, SnIV and VV was tolerable at 3–10 µg l–1 and that from FeII and FeIII at 50 µg l–1 in the determination of 4 µg l–1 of copper. The interference from FeIII up to 500 µg l–1 was eliminated by addition of NaNO2. The proposed method was applied to the determination of copper in river and rain waters.

Production of micron‐size monodisperse polymer particles by seeded polymerization utilizing dynamic swelling method with cooling process

AbstractMonodisperse polystyrene particles (6.6 μm diameter) were produced by seeded polymerization utilizing the dynamic swelling method with cooling process as follows. Monodisperse polystyrene seed particles (1.8 μm diameter) were dispersed in ethanol/water (3/4 w/w) medium containing styrene monomer, benzoyl peroxide as initiator and poly(vinyl alcohol) as stabilizer at 65d̀C. By lowering the temperature to −5d̀C at a speed of −1d̀C/min the polystyrene seed particles were swollen from 1.8 to 7.7 μm by the absorption of styrene monomer, keeping the high monodispersity. An appropriate amount of water was then added to the dispersion at −5d̀C to depress the redissolution of styrene from the swollen particles into the medium. By elevating the temperature the seeded polymerization was carried out at 70d̀C. The production of submicron‐size polystyrene new particles as a by‐product was depressed by the addition of NaNO2 to the medium.

Autocatalytic dissolution of Pb in HNO3

The reaction between Pb and HNO3 has been investigated using the thermometric technique. Weight-loss measurements on the reaction were also obtained. As the HNO3 concentration is increased from 5×10−2 to 4mol l−1, the corrosion rate increases. This is shown thermometrically by a substantial increase in the maximum temperature attained, T m, as well as a decrease in the time, t, required for reaching T m. Dissolution of Pb in HNO3 is proposed to take place according to an autocatalytic mechanism. Passivation sets were detected in solutions ≥11 mol l−1 HNO3. A parallel indication between the thermometric technique and weight-loss measurements was obtained. The rate-determining step of the autocatalytic process involves HNO2 in dissolution of Pb in HNO3. This is supported by the results of addition of hydrazine to the solution. This additive raises the maximum measured temperature, without affecting the corresponding time necessary to reach it. The effect of addition of NaNO2, NaNO3, NaCl, Na2SO4, NaH2PO4 and NaClO4 on the reaction number, RN, of Pb in 4 mol l−1 HNO3 was examined. Only NaNO2 accelerates the dissolution reaction while the other salts show as inhibition effect. It was found that these additives inhibit dissolution due to the displacement of some cathodic depolarizing components, as NO2, from the active sites on the metal surface. The effect of addition of HCl, H2SO4, HClO4 and H3PO4 on the reaction number, RN, of Pb in 4 mol l−1 HNO3 was also investigated. The observed acceleration and retardation of the dissolution of Pb was found to be dependent on both the concentration and nature of anions of the extra acids added.

The Phenomenon of Conglomerate Crystallization. XXII. Synthesis and Structural Characteristics of H-Carbonato(O,O')-trans-[CO(2,3,2-tet)(NO2)]2Cl2.3H2O

Abstract The unique, dinuclear, symmetrically μ-CO3 bridged compound, μ-carbonato(O,O')-trans-[Co(2,3,2-tet)-(NO2)]2C12.3H2O (I), was prepared by hydrogen peroxide oxidation of Co+2 in the presence of the 2,3,2-tet polyamine ligand, followed by addition of NaNO2. (I) crystallizes in the racemic space group P21/n with cell constants a = 9.187(1) A, b = 23.520(2), c = 14.201(1), β = 103.87(9), V= 2978.90 A3 and d(Z = 4 mol/cell) = 1.599 g cm−3. Data were collected in the range 4° ≤ 20 ≤ 50°, for a total of 5361 reflections, of which 3285 were independent and had I ≥ 3σ(I). These were used in the solution and refinement of the structure. The F(hkl)abs were corrected for absorption (μ = 13.540 cm−1) using Psi scan curves of eight suitable reflections, leading to transmission coefficient adjustments ranging from 0.9049 to 0.9967. The structure was solved by Patterson methods. Convergence of the refinement using anisotropic thermal parameters for the heavy atoms and idealized hydrogens (fixed B = 5.00 A2) gave ...