Addition Of Concentrated Sulfuric Acid Research Articles

Optimization of sample preparation conditions in the determination of total arsenic in fish and seafoods by atomic absorption spectrometry with electrothermal atomization

The conditions for sample preparation and determination of total arsenic in fish and seafoods by atomic absorption spectroscopy with electrothermal atomization have been optimized. When using a standard sample preparation procedure (GOST R 53100), a complete decomposition of the organic arsenic compound, arsenobetaine, appeared impossible which leads to underestimated results. A novel sample preparation procedure for the determination of total arsenic, including the addition of concentrated sulfuric acid for complete decomposition of the organic forms of arsenic to inorganic ones is proposed. During the atomization of the sample, an additional stage of drying was introduced with smooth heating from 200 to 250°C, which contributed to a complete removal of sulfuric acid residues from the injected sample volume. The correctness of the proposed methodology was verified using the ICP-MS method and in the analysis of reference samples of fish and seafoods.

Comparison of Alum and Sulfuric Acid to Retain and Increase the Ammonium Content of Digestate Solids during Thermal Drying

Aluminum sulphate (alum, Al2(SO4)3·nH2O) has successfully been used to reduce ammonia loss from poultry litter, cattle feedlots and manure composting, but has not yet been utilized in the thermal drying process of digestate solids. The objectives of the present study were to evaluate the effects of alum addition on ammonium nitrogen (NH4+-N) content and phosphorus (P) solubility in dried digestate solids in comparison to the addition of concentrated sulfuric acid (H2SO4). Manure-based (MDS) and sewage sludge-based (SDS) digestate solids were chosen to conduct a drying experiment at four pH levels (original pH, 8.0, 7.5 and 6.5) and using two acidifying agents (alum, concentrated H2SO4). Alum addition increased the final NH4+-N content significantly from 1.4 mg g−1 in the non-acidified control up to 18 mg g−1 and 10.8 mg g−1 in dried MDS and SDS, respectively, which were higher levels than obtained with the addition of concentrated H2SO4. Moreover, alum considerably lowered the water extractable phosphorus (WEP) in raw and dried SDS by 37–83% and 48–72%, respectively, compared with the non-treated control. In contrast, concentrated H2SO4 notably increased WEP in raw and dried MDS by 18–103% and 29–225%, respectively. The comparison between the two acidifying agents indicated that alum had the potential to be an efficient and easy-handling alternative to concentrated sulfuric acid, resulting in higher NH4+-N content and lower P solubility.

Extraction of platinum and gold from copper anode slimes by a process of chlorinating roasting followed by chlorinating leaching

A novel process of chlorinating roasting followed by chlorinating leaching to extract platinum and gold from copper anode slimes was proposed in this research. Results of thermodynamic analysis and experimental research showed that the platinum was chlorinated into PtCl2 while the gold existed in the form of metallic Au during the roasting process. With the copper anode slime being directly leached using a traditional process, the Pt recovery rate was low and came to 80.72%. After the roasting process with sodium chloride and concentrated sulfuric acid in oxygen atmosphere, the recovery rate of Pt increased to a value around 95%. Moreover, with excessive addition of concentrated sulfuric acid, more H2O (g) was generated and the formation of Cl2 (g) decreased due to the transition from HCl (g) and Cl2 (g), as a result of which the Pt recovery rate decreased. In addition, this chlorinating roasting had little effect on the Au recovery due to its difficulty to be chlorinated.

Scandium extraction from silicates by hydrometallurgical process at normal pressure and temperature

Silicate is an important rock-forming mineral. In this work, a method called “sulfuric acid curing” was proposed, aiming to extract rare earth element scandium from silicates. Sulfuric acid curing refers to the addition of concentrated sulfuric acid to heated silicates at 60–300°C, and subsequently water leaching of the treated silicates at 30–75°C. The effects of sulfuric acid dosage, curing time, curing temperature, pulp density, leaching temperature and stirring speed on scandium leaching were investigated. Under the condition of sulfuric acid dosage with 0.75 times of the theoretical amount, curing time of 15 h, curing temperature of 200°C, pulp density for L/S ratios of 30:1, leaching temperature of 75°C, stirring speed of 100rpm, Sc(III) concentration of 492μg/L in the solution was achieved. XRD analysis shown that major phases of the samples hardly changed after acid curing. However, SEM-EDS examination of the samples demonstrated that morphology and particle size of minerals were changed obviously after being cured and leached. Leaching kinetics was further calculated, which can be described by the shrinking core model. The apparent activation energy for the dissolution was determined to be 55.49kJ.mol− 1.

Synthesis, physical and chemical properties of esters of 2-((5-(hydroxy(phenyl)methyl)-4-R-1,2,4-triazole-3-yl)thio)ethanoic and 3-(((5-(hydroxy(phenyl)methyl)-4-R-1,2,4-triazole-3-yl)thio)methyl)benzoic acids

The wide use of 1,2,4-triazole derivatives in medical practice is primarily explained by two most important properties: high biological activity and low toxicity. It is difficult to overestimate the contribution to medical practice, which such medicines as posaconazole and letrozole have made. Many scientists of the pharmaceutical industry pay attention to the search of biologically active substances among this heterocyclic system derivatives. Aim. The aim of our study is purposeful synthesis of new highly effective and low-toxic substances among the derivatives of 2-((5-(hydroxy(phenyl)methyl)-4-R-1,2,4-triazol-3-yl)thio)ethanoic and 3-(((5-(hydroxy(phenyl)methyl)-4-R-1,2,4-triazol-3-yl)thio)methyl)benzoic acids, the study of their physical and chemical properties. Materials and methods. The 2-((5-(hydroxy(phenyl)methyl)-4-R-1,2,4-triazol-3-yl)thio)ethanoic and 3-(((5-(hydroxy(phenyl)methyl)-4-R-1,2,4-triazol-3-yl)thio)methyl) benzoic acids were used as initial substances, which were obtained at the previous stage of synthesis. The esters were synthesized by the esterification of 2-((5-(hydroxy(phenyl)methyl)-4-R-1,2,4-triazol-3-yl)thio)ethanoic and 3-(((5-(hydroxy(phenyl)methyl)-4-R-1,2,4-triazol-3-yl)thio)methyl)benzoic acids in the appropriate alcohol medium with the addition of concentrated sulfuric acid in catalytic amoun. Results. The structure of obtained compounds was established using a complex of modern physical and chemical analysis methods. The experimental determination of the elemental composition of the obtained substances corresponds to the calculated data. The only one peak was detected on the chromatograms of synthesized esters, which corresponds to the calculated molecular weight m/z + of series compound. The IR-spectra of the synthesized compounds have the absorption bands of the C-S groups, absorption bands of the aromatic ring, symmetric and asymmetric absorption bands of the C-O-C groups and they fit with reference data. The 1 H NMR spectra have proton signals of methyl and methylene groups of the obtained compounds. It ultimately confirms the structure of the synthesized compounds. Conclusions. We have developed effective laboratory methods for the preparation of esters of 2-((5-(hydroxy(phenyl)methyl)-4-R-1,2,4-triasole-3-yl)thio)ethanoic and 3-(((5-(hydroxy(phenyl)methyl)-4-R-1,2,4-triazol-3-yl)thio)methyl)benzoic acids during the experimental work. Thirteen new compounds were synthesized which are now the objects of further pharmacological researches.

Color Change of Sudan III against Concentrated Sulfuric Acid in Acetonitrile and Quantification for a Small Amount of Concentrated Sulfuric Acid.

The color-changing phenomenon of hydrophobic bisazo dye, Sudan III in an acetonitrile solution against the addition of concentrated sulfuric acid has been discovered and the chromic properties investigated. Based on observations, a novel quantification method of concentrated sulfuric acid has been developed. Sudan III changes its color from orange to blue against a small volume of sulfuric acid, and the acetonitrile solution of Sudan III is the most suitable for observing the color-change phenomenon. (1)H-NMR and UV-Vis spectroscopic studies showed that the color-change mechanism of Sudan III against sulfuric acid is due to the protonation of the dye by sulfuric acid. This phenomenon is applicable to the quantification of concentrated sulfuric acid by introducing the Hammett acidity function. The proposed method requires only a small amount of the sample, 0.04 mL, and enables rapid quantification.

Facile synthesis and electrochemical properties of α‐MnO2 as electrode material for supercapacitors

ABSTRACTMnO2 as the electrode material for supercapacitors has attracted much interest in recent years. However, there are still some restrictions for its application. In this paper, to improve the capacitive properties of MnO2, material was synthesized by a facile and efficient low‐temperature reduction reaction between KMnO4 and Cu foil in sulfuric acid solutions. The results showed that the initial concentrations of KMnO4 and the addition of concentrated sulfuric acid have distinct influence on the structure, morphology and electrochemical properties of the as‐prepared MnO2. Particularly, morphological characterization displayed that the sample synthesized in 0.05 mol L−1 KMnO4 and 16 mL concentrated sulfuric acid is composed of urchins with the average diameter of 0.7 µm. The product exhibits a discharge specific capacitance of 288.03 F g−1 at the constant current density of 65 mA g−1. The capacitance remains about 50% of the initial capacitance at 250 mA g−1, and is 100.06 F g−1 after the 100th cycle. © 2013 Curtin University of Technology and John Wiley & Sons, Ltd.

Isolation of Lipophilic Persistent Organic Pollutants From Human Breast Milk

Background: Lipid removal from biological samples can be achieved by addition of concentrated sulfuric acid. However, certain persistent organic pollutants (POPs) such as chlorophenols are decomposed by sulfuric acid treatment and, thus, a more gentle lipid reduction method is needed for extraction of many environmental contaminants from biological samples. Membrane dialysis extraction (MDE) is a non-disruptive method to extract POPs from biological matrices. Methods: Human breast milk samples were spiked with radiolabelled p,p′-dichlorodiphenyl trichloroethane ([C-14]-DDT) as a POP proxy and extracted using solid phase extraction (SPE). The extracts obtained were dialyzed by MDE in low-density polyethylene tubings containing a mixture of n-hexane and dichloromethane for 24 h, 48 h, or 72 h. Results: The lipid content was reduced by 86.2% after one dialysis cycle of 24 h using MDE, and 87.1% recovery of the [C-14]-DDT standard was obtained. The DDT recovery could be further increased up to 96.3% and 98.1% by repeating the dialyses for one or two more cycles, respectively. However, the increased [C-14]-DDT recovery includes a concomitant increase in lipid carryover from 13.8% with one dialysis cycle to 22.1% with three cycles. Conclusion: An SPE procedure for extracting POPs from breast milk and dialytic conditions for isolation of the extracted POP with minimal lipid carryover was established. The method is nondestructive and acceptable recoveries can be obtained within a single solvent shift as demonstrated by spiking standards. The lipid carryover was minimized, and the method may be considered for lipid removal before HPLC or GC analysis of environmental contaminants.

Base/acid-catalyzed FAEE production from hydroxylated vegetable oils

In this study was developed a new methodology to produce fatty acid ethyl esters from castor oil. The base-catalyzed transesterification step was followed by on pot addition of sulfuric acid. That addition implicated the successful separation of FAEEs/glycerin phases due to soap breaking. The study was carried out through an experimental design where the variables studied in the first step were the molar ratio alcohol:oil and the catalyst amount in the transesterification process. As expected, the on pot addition of concentrated sulfuric acid yields FFAs that increase the acid value in the FAEEs phase. A second step esterification of these free fatty acids from FAEE raw mixture was investigated. The esterification of FFA was carried out in 60:1 and 80:1 M ratios (alcohol:free fatty acids) and concentrated sulfuric acid 5% and 10% w/w (based on free fatty acids). Consequently, these two steps yielded more fatty ethyl esters and assure that the following important requirements in the FAEEs production process from castor oil are satisfied: complete reaction, best separation of FAEEs/glycerin phases, removal of catalyst, limpid glycerin, and absence of free fatty acids.

Destruction of Peroxide Explosives

Chemicals containing multiple peroxide functionalities, such as triacetone triperoxide (TATP), diacetone diperoxide (DADP), or hexamethylene triperoxide diamine (HMTD), can be explosive. They are impractical and are not used by legitimate military groups because they are shock and heat sensitive compared to military explosives. They are attractive to terrorists because synthesis is straightforward, requiring only a few easily obtained ingredients. Physical removal of these synthesis products is highly hazardous. This paper discusses methods to degrade peroxide explosives chemically, at room temperature. A number of mixtures containing metals (e.g., zinc, copper) and metal salts (e.g., zinc sulfate, copper chloride) were found effective, some capable of destroying TATP solutions in a few hours. Strong acids proved useful against solid peroxide materials; however, on a 1 g scale, addition of concentrated sulfuric acid caused TATP to detonate. Thus, this technique should only be used to destroy small-laboratory quantities.

Generating Water-Soluble Noxious Gases: An Overhead Projector Demonstration

A simple, inexpensive apparatus to generate and collect water-soluble noxious gases as an overhead projector demonstration can be made from two small beakers and a Petri dish. The detection and generation of sulfur dioxide and nitrogen dioxide are described. Sulfur dioxide dissolved in water is detected using an acid-base indicator, decolorizing of anthocyanin, or reduction of permanganate. The SO2 is generated by addition of sulfite or bisulfite to a strong acid or by the addition of concentrated sulfuric acid to sugars. Nitrogen dioxide is generated by mixing copper and nitric acid and detected using an acid-base indicator.

Interaction of some steroids with inorganic species in the presence of concentrated sulfuric acid: Kinetic-fluorometric study

The influence of 30 ionic species added previously to the addition of concentrated sulfuric acid on three steroids was studied. It has been proven that in the presence of some ionic species (Mg(II), Cr(III), Ce(IV), …) formation of fluorescent products occurs to a higher extent, permitting the establishment of methods for their determination. This process was investigated and the experimental variables and interference in each determination were reported.

A novel method for the determination of iodide in table salt by X-ray fluorescence

A novel HI generation technique was developed and evaluated for the determination of iodide in table salt. HI was generated from the samples by the addition of concentrated sulfuric acid and adsorbed onto an ion-exchange resin loaded paper disk. The disk was then measured by X-ray fluorescence. The method compared favorably to the cellulose pellet technique, being more sensitive and reproducible and requiring less time per analysis. The method was applied to six samples of table salt and one of sea salt.

The Effect of Bacterial Contamination and Aging on the Volatility of Mercury in Urine Specimens

Abstract The effect of specimen aging on the recovery of mercury from urine samples was investigated. It was found that in some aged specimens the addition of concentrated sulfuric acid to the urine without cooling resulted in a large loss of mercury. This phenomenon is presumed to be due to enhanced volatility of the mercury caused by bacterial action. This loss can be avoided by adding a suitable preservative to the urine, by chilling the urine while the concentrated sulfuric acid is being added, or, most conveniently, by using 50% (V/V) sulfuric acid in place of the concentrated acid. It was also found that the use of a reflux condenser is unnecessary when urine is being oxidized by heating with sulfuric acid and potassium permanganate.

A SIMPLE QUANTITATIVE COLORIMETRIC METHOD FOR ESTROGENIC STEROIDS

MANY colorimetric methods for determining natural estrogens have been described, most widely used of which is the reaction described by Kober (1931) (4). Although supposedly specific for estrogenic steroids, this reaction has been shown by Mather (1940) (6) to give similar positive tests with five times as much androsterone. Kober (1931) (4) noted that a red color was obtained upon the addition of concentrated sulfuric acid to estrone, heating, diluting with water and reheating. However, an intense greenish fluorescence was also present which interfered with the quantitative colorimetric determination by visual methods. He found that addition of phenol quenched the fluorescence and permitted a more accurate determination of the red color. The Kober test is a two phase reaction. The first is heating with phenolsulfonic acid, which produces a yellow colored solution, and the second phase is dilution with water or dilute sulfuric acid and reheating, which produces a red colored solution. Various modification...