Excess Of Nitric Acid Research Articles

Aalnysis of Influencing Factors for the Detection of Total Mercury in Food by Atomic Fluorescence

With the increase of people's attention to nutrition and health, food quality and safety have also become the focus of people's daily attention, among which mercury and its compounds are widely distributed in nature, with high volatility, high toxicity and harmful accumulation. In this paper, the first method of atomic fluorescence spectroscopy in GB5009.17-2021 "National Food Safety Standard - Determination of Total Mercury and Organic Mercury in Food" was comprehensively analyzed in the detection of total mercury in food, and the key points of sample pretreatment, the on-machine detection process and the detection experiment were comprehensively analyzed. The analysis of key points of pretreatment mainly includes: sample weighing, cleaning and use of detection instruments, amount of acid in microwave digestion process, optimization and setting of microwave digestion program, and analysis and research on the elimination method of excess nitric acid after microwave digestion is completed. The analysis of the key parameters of the atomic fluorescence photometer of the detection equipment during the sample testing on the machine includes: the setting and optimization of the instrument parameters, the daily maintenance method of the key components of the instrument, etc.; Through the analysis and study of all aspects of the entire detection process, the main factors affecting the accuracy of the detection results are identified for improvement and solidification implementation, so as to more effectively improve the accuracy of the measurement results.

Using Nitrated Lignosulfonates for the Synthesis of a Water-Based Magnetic Fluid

Nitrated lignosulfonates were used to synthesize a water-based magnetic fluid. Lignosulfonates were nitrated by nitric acid under mild conditions and without further purification were used to synthesize a magnetic fluid. Part of the iron(II) were oxidized with an excess of nitric acid, so that the magnetoactive phase under the condensation by action of sodium hydroxide was formed. Optimum conditions for nitration of lignosulfonates and synthesis of a magnetic fluid were experimentally established. The optimum consumption of iron(II) was 1.3–1.5[Formula: see text]g per 1[Formula: see text]g of sodium lignosulfonate. Unlike the initial lignosulfonates, nitrated lignosulfonates have peptizing properties, due to which the precipitate formed during condensation was dispersed to nanoparticles (15–30[Formula: see text]nm). The resulting magnetic fluid had a high magnetic activity and was stable for a long time.

Nitration of 3-Methylaceperidazines with a Large Excess of Fuming Nitric Acid

Nitration of N-acetyl-3-methylaceperidazine with a 2–3-fold excess of nitric acid (d 1.36, 1.48) in glacial acetic acid results in the exclusive formation of mono- and dinitroderivatives. The nitration of 3-methylaceperidazine and its N-alkyl- and N-acetyl-substituted derivatives with a 6–9-fold excess of fuming nitric acid (d 1.54) in the same conditions results in the formation of both the expected products of mono- and dinitration and a product of the electrophilic addition of nitric acid to a double bond of acenaphthene scaffold of the molecule of nitration product.

Cinética de dissolução de um metacaulim amazônico em ácido nítrico

Abstract The kinetic study of Amazon metakaolin dissolution was performed with the application of the shrinking core model for spherical and ‘flat plate’ particles with constant size. The Amazon kaolin was calcinated at 700 ºC in order to produce metakaolin. This metakaolin was leached with 5% excess nitric acid at 70, 80 and 95±3 ºC for 3 h. Samples were collected every 15 min and subjected to aluminum analysis. The acid leaching was a chemically controlled process. The spherical morphology showed better fit than the flat plate particles when taking into account the regression coefficients. 91.58 kJ/mol of activation energy was found as well as an aluminum leaching reaction of the first order. The results found in this work using 5% excess acid and Amazon kaolin were consistent with previous research results using excess acid above 50% and standard kaolin.

Stoichiometry of water-soluble ions in PM2.5: Application in source apportionment for a typical industrial city in semi-arid region, Northwest China

Water-soluble ions (WSIs) are major components of PM2.5 and it is valuable for understanding physical and chemical characteristics, sources, behaviors and formation mechanism of WSIs. Baotou is a traditionally industrial city in semi-arid region and frequently subjected to dust storms from March to May. In recent years, air pollution has been listed as one of the most important environmental problems in Baotou. To investigate the seasonal variations and sources of WSIs in PM2.5, the WSIs including SO42−, NO3−, Cl−, F−, NH4+, K+, Na+, Ca2+ and Mg2+ were monitored at six urban sites in Baotou. The results showed that high concentrations of Ca2+ and Na+ were found responding to dust storm events, while high concentrations of SO42−, NO3−, NH4+, K+ and Cl− were observed during haze days. The correlations analysis indicated that excess sulfuric and nitric acid was likely neutralized by carbonate minerals such as calcite, aragonite and dolomite in normal days and cations were fully neutralized during all the sampling periods, while cations were excessive in dust storm days. The concentrations of [NH4+ + SO42− + NO3−], [Na+ + Ca2+ + Mg2+] and [Cl− + K+ + F−] indicated the northwest and southeast region of Baotou presented comparatively high contributions of secondary aerosol and crustal dust, respectively, which were mainly related to the industrial distribution and urbanization process. The cluster analysis, ternary diagram and principal component analysis have a good agreement in source apportionment, where crustal dust sources, secondary aerosol source and the mixture of coal combustion, biomass burning and industrial pollution sources were the main sources of WSIs in PM2.5. The seasonal pattern of sulfur oxidation ratio (SOR) was September > April > November > January, while the nitrogen oxidation ratio (NOR) April > January > November > September in Baotou. This work evaluated the seasonal variation, distribution and source of WSIs on the basis of its stoichiometry in PM2.5, which help to explore the potential sources of these inorganic aerosols and provide scientific suggestion for air quality improvement in Baotou.

Spectrophotometric Estimation of Lamotrigine in Tablets

Simple and accurate spectrophotometric methods have been developed for the determination of lamotrigine in tablet formulation. The method A was based on the diazotization of lamotrigine followed by coupling with 4-(dimethylamino)benzaldehyde in acid medium to give greenish yellow product with a λmax of 410 nm. The method B also was based on the diazotization of drug and conversion of phenol into nitrosophenol with excess nitrous acid in acid medium to give brown color with a λmax of 448 nm. Thus, methods A and B were used to determine lamotrigine in the range of 1-10 μg/ml and 2.5-12 μg/ml, respectively in the final measured solution. There was no interference from the ingredients commonly found in lamotrigine tablets with these methods. The results compared favorably with those of reported methods and related analytical parameters were calculated.

Nitration of phenol in 1,4-dioxane

The nitration of phenol with excess nitric acid in aqueous dioxane, in contrast to the nitration in aqueous ethanol, yields exclusively 2,4-dintrophenol, whereas at equimolar ratio of phenol and nitric acid the major reaction products are mononitrophenols (99%), among which the p-isomer prevails.

Room-temperature synthesis of Bi4Ge3O12 from aqueous solution

Single-phase bismuth germanate (Bi4Ge3O12 abbreviated as BGO) powder was successfully synthesized by means of a room-temperature chemical process under atmospheric pressure. This was achieved by mixing ammonia with a homogeneous aqueous solution of bismuth nitrate containing excess nitric acid and ammonium germanate. The resulting BGO powder exhibited a peculiar morphology of nanoscale indentations that gave each particle a flower-like shape. The main peak of its photoluminescence (PL) spectrum was almost the same as that observed with commercial high-purity BGO powder, but additional weak luminescence peaks were observed at about 370 and 820 nm that showed good agreement with the PL peaks of BiGeO2(OH)2(NO3) powder. Furthermore, the synthesized BGO powder was confirmed to be a single BGO phase through X-ray diffraction and Rietveld analysis, and the existence on the adsorbed H2O, HNO3, and chemisorbed NO3 were detected through Fourier transform infrared spectroscopy.

ChemInform Abstract: Cyclization of Substituted 3,4‐Diaminopyridines into 1H‐[1,2,3]Triazolo[4,5‐c]pyridine 2‐Oxide Derivatives During the Nitration Process.

The nitration of pyridine-3,4-diamine, its N,N′-diacetyl derivative, and N4-alkylpyridine-3,4-diamines with excess nitric acid in concentrated sulfuric acid at 60°C was accompanied by cyclization with formation of the corresponding 1-substituted 4-nitro-1H-[1,2,3]triazolo[4,5-c]pyridine 2-oxides. 4-Chloro-1H-[1,2,3]triazolo[4,5-c]pyridine 2-oxide derivatives were obtained under analogous conditions from 2-chloropyridine-3,4-diamine, its N,N′-diacetyl derivative, and 2-chloro-N4-methylpyridine-3,4-diamine. The nitration of these compounds at 80–90°C gave 4-chloro-7-nitro-1H-[1,2,3]triazolo[4,5-c]pyridine 2-oxides.

Forensic utility of isotope ratio analysis of the explosive urea nitrate and its precursors

Urea nitrate (UN) is an improvised explosive made from readily available materials. The carbon and nitrogen isotope composition of UN and its component ions, urea and nitrate, could aid in a forensic investigation. A method was developed to separate UN into its component ions for δ 15N measurements by dissolving the sample with KOH, drying the sample, followed by removal of the urea by dissolution into 100% methanol. UN was synthesized to assess for preservation of the carbon and nitrogen isotope compositions of reactants (urea and nitric acid) and product UN. Based on nitrogen isotope mass balance, all UN samples contained varying amounts of excess nitric acid, making the ionic separation an essential step in the nitrogen isotope analysis. During UN synthesis experiments, isotopic composition of the reactants is preserved in the product UN, but the urea in the product UN is slightly enriched in 15N (<1‰) relative to the reactant urea. Published isotopic compositions of UN reactants, urea and nitric acid, have large ranges (urea δ 15N = −10.8 to +3.3‰; urea δ 13C = −18.2 to −50.6‰; and nitric acid δ 15N = −1.8 to +4.0‰). The preservation of isotopic composition of reactants in UN, along with a significant variability in isotopic composition of reactants, indicates that isotope ratio analysis may be used to test if urea or nitric acid collected during an investigation is a possible reactant for a specific UN sample. The carbon and nitrogen isotope ratios differ significantly between two field-collected UN samples, as well as the lab-synthesized UN samples. These observed variations suggest that this approach is useful for discriminating between materials which are otherwise chemically identical.

Cyclization of substituted 3,4-diaminopyridines into 1H-[1,2,3]triazolo[4,5-c]pyridine 2-oxide derivatives during the nitration process

The nitration of pyridine-3,4-diamine, its N,N′-diacetyl derivative, and N4-alkylpyridine-3,4-diamines with excess nitric acid in concentrated sulfuric acid at 60°C was accompanied by cyclization with formation of the corresponding 1-substituted 4-nitro-1H-[1,2,3]triazolo[4,5-c]pyridine 2-oxides. 4-Chloro-1H-[1,2,3]triazolo[4,5-c]pyridine 2-oxide derivatives were obtained under analogous conditions from 2-chloropyridine-3,4-diamine, its N,N′-diacetyl derivative, and 2-chloro-N4-methylpyridine-3,4-diamine. The nitration of these compounds at 80–90°C gave 4-chloro-7-nitro-1H-[1,2,3]triazolo[4,5-c]pyridine 2-oxides.

Isolation, structure, and properties of quinone-aci tautomer of a phenol-nitro compound related to eugenoxyacetic acid

Treatment with excess nitric acid in acetic acid revealed that eugenoxyacetic acid underwent an unexpected ether cleavage, a normal nitration, and then an unexpected electrophilic addition to the double bond of the side chain that led to the formation of a dinitro compound which subsequently converted to a sensitive, reactive quinone-aci compound. The structure of the quinone-aci compound ( 1) and its derivatives ( 2– 6) was established by 1D- , 2D NMR, MS spectra, and chemical methods. In addition, the XRD structure of compound 2 derived from 1 was established. A double tautomerization of 1 in solution was studied by the LC–UV–MS method.

Synthesis and characterization of coordination polymers of a carboxylato cyclophane with metal [Zn(II) and Cd(II)]-2,2′-bipyridines

N,N′,N′′,N′′′-Tetrakis(3-carboxy-propionyl)-1,6,20,25-tetraaza-[6.1.6.1] paracyclophane, H 4cp has been complexed with metal (Zn(II) and Cd(II)) 2,2 ′ -bipyridyls. The resulting complexes of the composition [{Zn(2,2 ′-bpy)} 2(cp)] n ·4H 2O 1 and [{Cd(2,2 ′-bpy)} 2(cp)] n ·5H 2O 2 (2,2 ′-bpy = 2,2 ′-bipyridine) have been characterized using spectroscopic (IR, solid state UV–Vis), elemental analysis and single-crystal X-ray diffraction measurements. In these complexes the cyclophane coordinates in different modes, and in complex 2, Cd(II) is hepta-coordinated. However, under harsh reaction conditions (using excess nitric acid and a longer reaction time) debranching of the cyclophane is observed in the reaction of Zn(2,2 ′-bpy)(NO 3) 2 with H 4cp, and a complex of the composition [Zn(2,2 ′-bpy)(Suc)] n 3 (suc = succinate) is isolated. Using non-covalent interactions, complexes 1 and 2 provide 3D supramolecular structures, whereas an infinite 1D chain structure is observed for complex 3. The thermal and photoluminescence properties of the complexes have also been studied.

Nitration of Alkyl Benzoates with Mixed Acid

AbstractThe nitration of (substituted) benzoic acid esters is usually performed in fed‐batch operation. The ester is solved in sulfuric acid charged first. The nitric acid dosed keeps the reaction temperature under control. The safety regarding uncontrolled reaction conditions was investigated under variation of the ratio of nitric acid to charged aromatic compound. A significant decrease in thermal stability of the reaction mixture was observed with excess of nitric acid. Safe operation cannot be assumed in general when the acid is close to or exceeds 10 % molar ratio. The investigation was restricted to aromatic carboxylic acid alkyl esters which form homogeneous mixtures with sulfuric acid. The thermal stability was investigated by differential thermal analysis (closed systems), adiabatic storage tests, and dynamic calorimeters. The reaction products were analyzed by means of NMR and mass spectrometry. The experiments showed that the formation of dinitro compounds cannot cause the thermal instability alone. The formation of dinitro compounds starts at temperatures above the reaction conditions. Another component is responsible for the thermal instability which accumulates in the presence of an ester group at excess nitric acid. It could be deduced that the decomposition reaction is primarily caused by the reaction of surplus nitryl cation (NO2+ ion) with the nitrated carboxylic acid ester in the presence of sulfuric acid. The decomposition temperature of the reaction mixture depends on the nature of the ester group and the type and number of further substituents on the aromatic ring.

4,4′,4′′-(1,3,5-Triazine-2,4,6-triyl)tripyridinium trinitrate

Reaction of 2,4,6-tris(4-pyridyl)-1,3,5-triazine (tpt) with excess nitric acid in an aqueous solution affords the title compound, C18H15N6 3+·3NO3 −. The torsion angles between adjacent aromatic rings are much larger than those of neutral tpt. All three pyridine N atoms are protonated.

Facile and Efficient Selective Mono‐Nitration of Phenols under Solvent‐Free Conditions.

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Synthesis of nanocrystalline 8 mol% yttria stabilized zirconia powder from sucrose derived organic precursors

An organic precursor synthesis of 8 mol% yttria stabilized zirconia (YSZ) powder from Zr–Y composite nitrate solution and sucrose has been studied. Oxidation of sucrose in Zr–Y composite nitrate solution containing excess nitric acid in situ generates hydroxy carboxylic acids that forms a white sol which showed peaks at 1640 cm −1 and 1363 cm −1 in IR spectrum corresponding to hydroxy carboxylic acid complexes of Zr and Y. Precursor mass obtained by drying the sol on calcinations at 600 °C produced loosely agglomerated particles of cubic YSZ. Deagglomerated YSZ contain submicron particles with D 50 value of 0.5 μm and the particles are aggregates of nanocrystallites of nearly 10 nm size. Compacts prepared by pressing the YSZ powder sintered to 96.7% TD at 1450 °C. The sintered YSZ ceramic showed an average grain size of 2.2 μm.

Regiospecific Aryl Nitration of meso-Tetraarylporphyrins: The Directive Effect of para-Substituent

Regiospecific nitration of single p-substituted tetraphenylporphyrins with excess nitric acid is reported. The directive effects of different p-substituents, including nitro, acetamido and hydroxy groups, were demonstrated. The electron-withdrawing p-nitro group was found to lead to predominant nitration at the neighboring phenyl ring, and the electron-releasing p-acetamido and p-hydroxy groups lead to adjacent nitration at the same phenyl ring.

Hexazonium pararosaniline as a fixative for animal tissues

Hexazonium pararosaniline is a valuable reagent that has been used in enzyme activity histochemistry for 50 years. It is an aqueous solution containing the tris-diazonium ion derived from pararosaniline, an aminotriarylmethane dye, and it contains an excess of nitrous acid that was not consumed in the diazotization reaction. Other investigators have found that immersion for 2 min in an acidic (pH 3.5) 0.0015 M hexazonium pararosaniline solution can protect cryostat sections of unfixed animal tissues from the deleterious effects of aqueous reagents such as buffered solutions used in immunohistochemistry, while preserving specific affinities for antibodies. In the present investigation hexazonium pararosaniline protected lymphoid tissue and striated muscle against the damaging effects of water or saline. The same protection was conferred on unfixed sections treated with dilute nitrous or hydrochloric acid in concentrations similar to those in hexazonium pararosaniline solutions. Model tissues (solutions, gels or films containing gelatin and/or bovine albumin) responded predictably to well known cross-linking (formaldehyde) or coagulant (mercuric chloride) fixatives. Hexazonium pararosaniline solutions prevented the dissolution of protein gels in water only after 9 or more days of contact, during which time considerable swelling occurred. It is concluded that there is no evidence for a “fixative” action of hexazonium pararosaniline. The protective effect on frozen sections of unfixed tissue is attributable probably to the low pH of the solution.

Thermal hazards evaluation for sym-TCB nitration reaction using thermal screening unit (TSU)

A set of experiments was conducted in an HEL thermal screening unit with synthetic mixtures of raw materials in various proportions to evaluate the potential thermal hazards at normal and offset process conditions for nitration of symmetrical trichlorobenzene (TCB). The experiments were carried out in the adiabatic condition. The onset temperatures of the exotherms along with maximum temperature and pressure rise data for the desired and undesirable reactions were obtained. In the presence of excess nitric acid and oleum, the reaction shows a severe thermal runaway at the onset temperature of 138°C with a rapid rise in temperature and pressure leading to a potential explosion.