Acid Dichromate Research Articles

Digital image colorimetry for determination of ethanol in exhaled breath condensate.

Aim: This study aimed to develop a colorimetric approach for quantifying ethanol using smartphone image analysis. Method: This research presents a straightforward smartphone-based colorimetric sensor that efficiently measures ethanol levels in exhaled breath condensate (EBC) samples. The process involved changing the acidic dichromate color in an ethanolic solution, followed by image analysis. Results: The results showed that this method was able to estimate ethanol concentrations in the range of 300-1500 and 1600-8000μg ml-1 in EBC. Conclusion: This study was a follow-up study on the previous work published for the determination of ethanol in EBC samples and highlights the potential benefits of using digital images and smartphone applications for ethanol determination in biological samples.

Comparison of methods for determining organic carbon content of urban soils in Central Ohio

Reliable methods are key to quantify organic carbon in urban soils. Samples from across the Ohio State University campus were divided into two datasets (a) pH ≤ 7.5 and (b) pH ≥ 7.8. Organic carbon was assessed using multiple methods, including heated acid dichromate digestion (OCDichromate), loss-on-ignition (LOI) at 400 °C and 550 °C, a dry combustion method (OCTC), and an acid pre-treatment (OCacid). Mean organic C, in g kg−1, were OCTC (39.8), LOI550 (39.8), LOI400 (33.2), OCDichromate (31.8) for soils with pH ≤ 7.5. LOI400 and OCDichromate were more accurate than OCTC and LOI550. Mean organic C, in g kg−1, were LOI550 (23.6) > OCacid (20.2) ≥ LOI400 (17.9), OCDichromate (16.0) for soils with pH ≥ 7.8. Similar to pH ≤ 7.5 soils, LOI400 and OCDichromate methods were more accurate measures of OC. The two loss-on-ignition methods and the dichromate method were strongly correlated with each other (r = 0.91) however the two dry combustion methods were weakly correlated with the others (0.45 ≥ r ≤ 0.67). The dichromate oxidation proved to have the lowest variance of the methods tested (29.7 g2 kg−2). Paired t-tests found no significant differences between the loss-on-ignition 400° and the acid-pretreatment methods, and no significant differences between the dichromate and inorganic subtraction method (p < 0.05). Dichromate oxidation method should be implemented to measure soil organic carbon in urban soils that have carbonates present, especially dolomite. The dichromate oxidation method was found to be simple, rapid, and reliably determines SOC without the need to remove SIC.

Investigation onto the Effect of Surface Etching using Chemical Etchants on the Dye-Ability of UHMWPE Fibre

Ultra high molecular weight fibre cannot be dyed using conventional dyeing techniques as they are extremely hydrophobic and do not possess any polar groups. Wet etching of the surface was used as the pre-treatment process to improve the dyeability of the Ultrahigh Molecular Weight Polyethylene (UHMWPE) knitted fabric using potassium dichromate and sulphuric acid as etchants. The surface modified fabric was dyed at 130°C using High Temperature (HT) dyeing technique with disperse dye and evaluated in terms of Color Strength (K/S), washing fastness, rubbing fastness, and tenacity. It has been observed that wet etching improved the colour strength substantially with an overall good fastness to washing and rubbing but the tenacity decreased with an increase in etching time.

Quantification methods of pyrogenic carbon in soil with soil as a complex matrix: comparing the CTO-375 and Cr2O7 methods

ABSTRACT Pyrogenic carbon (PyC) or black carbon (BC), the residue of grassland and forest fires and fossil fuel combustion, plays an important role in carbon storage and pollutant adsorption in soil. To understand its roles in soil, it is necessary to accurately assess the PyC fraction. Soil is, however, a complex mixture of inorganic and organic matter, usually containing humic substances, i.e., non-PyC organic matter, in concentrations one to two orders of magnitude higher than PyC. This engenders difficulty in determining the PyC content in soils; thus, various quantitative methods have been proposed for different research purposes. In this study, the two widely used methods of chemo-thermal oxidation at 375°C (CTO-375) and acid dichromate oxidation (Cr2O7) method were reconsidered in terms of the suitability for determining the PyC content of soil by using model soil. The CTO-375 method was simpler, but the quantified PyC was suggested to be the combustion residue of non-PyC organic matter. By contrast, 29 to 40% of PyC content was determined as non-PyC organic matter by the Cr2O7 method. Therefore, we proposed an improved Cr2O7 method by increasing acidic K2Cr2O7 concentration threefold for quantification accuracy: although time-consuming, it resulted in the lowest overestimation on the PyC content, that is, 16 to 23% from non-PyC organic matter. The application of the improved Cr2O7 method to natural soil was confirmed with 99 to 103% certainty (recovery rate).

Exploring materials locally available to teach chemistry experimentally in developing countries

Chemistry is a basic science and it is present in most aspects of daily life. For being an instrument of human formation, assume a special role that expands cultural horizons and autonomy in the exercise of citizenship. Therefore, it is important that this subject is taught from an everyday life perspective so that it fulfills its transforming role. One of the problems that most developing countries face in science, technology, engineering, and mathematics (STEM) education is the lack of conventional materials and reagents for practical classes and demonstrations. Therefore, the present work aimed to build a breathalyzer simulator to be applied in a teaching class of chemistry. Several steps were followed since the construction of the breathalyzer, tests of its functionality using local alcoholic drinks as a source of ethanol and finally strategies were proposed for its application in the classroom. The results showed that the simulated breathalyzer was constructed using locally available materials, such as chalk, pen tubes and birthday balloons. Furthermore, during the device functional test was possible to observe color changes resulting from the interaction between the ethanol in the drinks and the acidic dichromate solution. Based on the results obtained, strategies were proposed for its usage in the classroom.

Recovery of chromium(VI) in wastewater using solvent extraction with amide

The chromium-containing industrial wastewater, as a type of common widespread hazardous waste, causes many environmental issues. This study aimed to develop a novel amide as extractant and evaluate its recovery of chromium(VI) in aqueous solutions. Comparing nine amides with different alkyl groups and six diluents with different polarity, 40% (v/v) C14H29NO and 60% (v/v) D80 were found to be the best composition of extractant solution. Meanwhile, batch-wise experiments were performed to investigate the influence of various operating variables on the extracting, scrubbing and stripping behavior. The results demonstrated that 99.67% chromium could be extracted after six-stage countercurrent extraction, almost all impurity ions such as Na, V, Al and Mg could be removed from the loaded organic phase after three-stage cross-current scrubbing and 95.72% chromium could be stripped after six-stage countercurrent stripping respectively under the optimum conditions. The Cr2O3 product with 99.01% purity was obtained and total chromium recovery from the chromium(VI) waste solution was 95.40%. Chromic and dichromate acid were extracted by forming neutral and ion association complexation with amide C14H29NO, respectively. Finally, thermodynamics and the possible structure of chromium extraction compounds were elaborated. It is believed that this established method is promising way for the treatment of chromium-containing industrial wastewater.

Effectiveness of treatment methods on polypropylene fibres incorporated in cement mortars

Fibre reinforcements are often used in cementitious materials to provide enhanced strength. However, the surface smoothness and inert chemical nature of polypropylene fibres result in an insufficient fibre–matrix bonding interface and hence lead to poor mechanical properties of these materials. Two distinct treatment methods, namely, porofication method and sulfuric acid–dichromate treatment method, are adopted to assess the effectiveness of these techniques on fibre–matrix interface properties. The paper begins with an investigation on the effectiveness of these methods on polypropylene fibres. The wetting characteristics of these fibres are determined using the water absorption test, contact angle measurements and scanning electron microscopy analysis. The study then focuses on the mechanical properties and durability of cement mortars incorporating treated polypropylene fibres. The void ratio, flexural and compressive strengths and split tensile strength are studied, and microstructural analyses are also carried out to support these measurements. The resistance to impact, freeze and thaw and carbonation of cement mortars incorporating treated polypropylene fibres is investigated. The treatment methods adopted in this study improve the interface between the hydrated cement product and fibres and also significantly enhance the mechanical properties and durability of these mortars incorporating polypropylene fibres.

Performance Improvisation of Bituminous Roads using waste Plastic Material

Utilization of waste plastic as a aggregate in bituminous mix results in weak bonding between the plastic and bitumen. This study reports on the feasibility of using plastic waste and chemical additives to improvise the performance and mechanical properties of bituminous mixtures. The selected recycled waste plastics were used as partial aggregate replacement in bituminous mix product. Strong oxidizing mixture of dichromate and sulphuric acid was used to treat the plastic, while the bitumen was treated with a cross linking agent, polyethylene mine. Three modified bituminous mixtures were prepared and the stiffness results were compared with the control bituminous mixture. It was observed that the stiffness increased by 10% for the chemically modified bituminous mixtures. This improvement is attributed to an increase in the bonding forces between the aggregates and the bitumen. Besides, a mechanism is proposed in order to explain the effect of the chemical additives on the increase in the stiffness of the bituminous mixture.

Persistence of chromate in vadose zone and aquifer sediments in Hanford, Washington

This study of vadose zone and aquifer sediments beneath a former dichromate spill site showed that the persistence of CrVI in the sediments and the large differences in released mass and rate was caused by the dissolution of multiple CrVI surface phases. Vadose zone sediments contained numerous 1 to 10 μm high solubility calcium chromate crystals, with lesser amounts of unidentified phases indicated by Ba/Cr association in weathered pyroxenes and Ca/Cr association in weathered Ca-rich plagioclase. Most (>90%) of the CrVI mass in these vadose zone sediments was readily leached in laboratory columns at high concentrations (up to 187 mg/L CrVI) likely from the highly soluble calcium chromate. Additional CrVI associated with other CrVI surface phases was additionally slowly released over 100 s of hours. The source of Ca and Ba for the CrVI precipitates may be from mineral dissolution associated with the historical surface spills of CrVI as an acidic dichromate solution. In contrast, aquifer sediments contained significantly less CrVI, which was slowly released over 100 s of hours. Small-sized CrVI-containing precipitates (<5 μm) were associated with Ca, Fe, and, to a lesser extent, Ba. Leaching with groundwater caused a decrease in ferrous iron surface phases. The observed leaching of CrVI from vadose zone and aquifer sediments has created a continuous source of CrVI to groundwater.

RECYCLING OF Eucalipto cloeziana UNDER BIOCHAR DIFFERENT PYROLISIS TEMPERATURES

In the thermal decomposition of the biomass, products which include carbon compounds are generated. Biochar, a by-product of decomposition, has been efficient in retaining carbon, as well for agricultural and environmental management. Thus, the objective of this research is to evaluate the thermal stability and the recalcitrance of eucalyptus-derived bioburden due to different heating rates and pyrolysis temperatures. To do so, biochar were produced from Eucalyptus cloeziana at nine pyrolysis temperatures and three heating rates, and thermogravimetric analysis, determination of C and functional groups by FTIR were performed. Increasing the aromaticity of the biochromes produced, at higher temperatures, results in an increase in their recalcitrance, as demonstrated by the increase in thermal resistance and the oxidation by acid dichromate.

A Novel Cellulose-Preparation Method

AbstractThe radiocarbon (14C) dating of contaminated old wood has been seen as a challenge requiring many lengthy procedures, often using strong alkali extractions and carbon-containing solvents. Introduced here is a novel protocol called 2chlorOx, a twice-repeated sequence of alkaline hypochlorite and acidic chlorite oxidations, which is shown to work well for 14C and 13C measurements on both &lt;5000 BP and &gt;50,000 BP wood samples, producing results superior to those from conventional acidic chlorite or acidic dichromate oxidations. The 2chlorOx method employs only inorganic reagents, many samples can be completed in less than one day under normal laboratory conditions, and cellulose prepared in this way is usually paper-white in color.

Temperature-dependent schlieren effect in liquid flow for chemical analysis

In flow analysis, such as flow injection analysis, liquid lens is formed at the boundary between two adjacent liquid media which have different refractive indices. Light refraction at the liquid interface gives the so-called ‘schlieren signal’. Schlieren effect is both concentration-dependent and temperature-dependent. In this work, the schlieren signal from temperature difference was quantitatively investigated for application in enthalpimetric measurement. The schlieren phenomena was then exploited for chemical analysis. A thermal insulated single flow line manifold was constructed using deionized water at 23 °C as the carrier. Deionized water at various temperatures in the range of 5–85 °C was injected into the carrier flow. A correlation between the schlieren signal and sample temperature was observed. A heat exchanger unit (HEU), consisting of a small volume glass-reaction chamber with a surrounding water jacket, was constructed. The unit was thermally insulated in a double layer cylindrical PVC unit. For demonstrating the applicability of temperature-dependent schlieren effect in chemical analysis, the exothermic oxidation reaction between acid dichromate and ethanol or ascorbic acid was employed with heat transferring to the surrounding water layer. When an aliquot of water from the HEU is injected into the constant temperature flow line the observed schlieren signal was dependent on the analyte concentration. Linear calibration (r2 > 0.99) were obtained covering the concentration range of ethanol and ascorbic acid as found in samples. The developed flow system provides good precision (RSD < 5%) with sample throughput of 4 sample h−1. The system were applied to the determination of ethanol in Thai white spirit and ascorbic acid in vitamin C tablets, respectively. The quantitative results obtained from the schlieren method were in agreement with the comparative methods.

The Effect of Chromium and Boron on the Lipid Peroxidation and Antioxidant Status (in Experiment)

Current anthropogenic factors have a destructive effect on the environment. In this connection, it becomes necessary to study the negative effects of substances on living organisms and ways to reduce them. This article evaluated the impact of potassium dichromate (K2Cr2O7) and boric acid (H3BO3) on the status of lipid peroxidation (LPO) and antioxidant system. The work is performed on 24 male rats of Wistar weighing 180-220 g, were grown in the vivarium of the Central research laboratory of West Kazakhstan state medical University named after Ospanov. An experiment on Wistar rats: 1st - warning; 2nd - received K2Cr2O7; 3rd – H3BO3; 4th – K2Cr2O7 and H3BO. The introduction of K2Cr2O7 intensified LPO and reduced activity of catalase, glutathione peroxidase and superoxide dismutase, the number of sulfhydryl groups. The results of the study allow asserting that the H3BO3 in the conditions of joint use with K2Cr2O7 has an antioxidant effect, which leads to inhibition of LPO and activation of antioxidant system. Therefore, we first established the antioxidant effect of boric acid in the combined effects of potassium dichromate and boric acid.

Characterization and Treatment of Sulfochromic Residues Generated from Soil Analysis

Research and routine analysis laboratories produce sizeable amounts of residues as a result of experiments and by-products of chemical reactions. An example of that is soil analysis, in which a sulfochromic solution is used for the determination of organic matter content. This solution contains sodium dichromate and sulfuric acid, reagents that oxidize the soil’s organic fractions and contribute to the presence of chromium in laboratory residues discharged into the environment. In an attempt to find solutions to environmental problems, the aim of the present study was to quantitatively and qualitatively characterize chromium-contaminated residues generated during soil analysis. Therefore, management methods were proposed in order to recover chromium in its trivalent form (Cr3+) by precipitation. The use of biochemical oxygen demand, chemical oxygen demand, nitrogen, phosphorus, and metals to characterize the samples revealed the presence of 16.76 g L−1 of total chromium, with 4.19 g L−1 of Cr(VI). By means of ozonation, 68 % of the chromium was converted to liquid form and, after being reduced with bisulfite, it was turned into chromium sulfate (III). The remainder, 32 %, was kept with the other metals present in the solid form (sludge).

Halogenated Symmetrical Tetraazapentacenes: Synthesis, Structures, and Properties.

We herein describe the synthesis and property evaluation of several brominated and chlorinated tetraazapentacenes. The targets were obtained by thermal condensation of 2,5-dihydroxyquinone with 4,5-dichloro-, 2,6-dichloro-, and 4,5-dibromo-1,2-phenylenediamine, followed by oxidation with hot acidic dichromate. Double alkynylation, reductive deoxygenation, and subsequent oxidation using MnO2 furnishes the target compounds. Absorption spectra, electrochemistry, and single crystal structures of the targets are reported. The 1,4,8,11-tetrachlorotetraazapentacene (1,4,8,11-tetrachloroquinoxalino[2,3-b]phenazine) carrying its chlorine atoms in the peri-positions packs in a herringbone type arrangement, while the isomer (2,3,9,10-tetrachloroquinoxalino[2,3-b]phenazine, with the chlorine atoms in the east and west positions) packs in one-dimensional stacks. In all cases, the reduction potentials and the calculated LUMO-positions are decreased by the introduction of the halogen atoms.

Saccharification and Single Step Fermentation of Cassava Peel by Mixed Culture of Saccharomycopsis fibuligera NCIM 3161 and Zymomonas mobilis MTCC 92

The main objective of this study was to utilize the cassava peel by saccharification and single step fermentation (SSF) by mixed culture of Saccharomycopsis fibuligera NCIM 3161 and Zymomonas mobilis MTCC 92. Single step fermentation was performed in conical flasks with various concentrations of cassava peel (30, 50, 70 and 90 g/L), pH (3.5, 4.5 and 5.5), temperature (37, 47 and 57° C), reaction time (72, 720 and 168 h), inoculum size (5, 10 and 15 % v/v) and agitation speed (50, 100 and 150 rpm). Cell growth was identified by measuring optical density at 660 nm. The total reducing sugars were determined by centrifuging at 5000 rpm for 10 min by 3,5-dinitrosalicylic acid method. Starch concentration was estimated by anthrone method. Ethanol concentration was determined by acid dichromate method. The optimum process conditions were substrate concentration of 70 g/L, pH of 4.5, temperature of 37° C, reaction time of 120 h, inoculum size of 10 % (v/v) and agitation speed of 100 rpm. Under these conditions, the highest ethanol concentration of 26.46 g/L was obtained for cassava peel (93.75 % of theoretical yield).

Effects of Sodium Nitrite, Sodium Dichromate and Benzoic Acid as Inhibitors in the Protection of Mild Steel in Water

In Petrobrás SA refineries, there are thousands of heat exchangers in which cooling water is treated for recycling, often by outsourced companies. In all of these refineries there happens shutdown for corrective maintenance of the exchangers by problems related to corrosion caused by the cooling water, requiring about four days to repair a unit. The shutdown of a production line results in loss of revenue between U$ 200,000.00 and U$ 300,000.00 per day. To control the cooling water quality, it is used coupons for corrosion analysis. Tests are limited to visual inspection and by mass loss analysis. In this work, inhibitors such as sodium nitrite, sodium dichromate and benzoic acid are used to protect metals immersed in water in order to avoid the corrosion and consequently the shutdown of the exchanger for corrective maintenance.

The Influence of Etching Time on the Surface Morphology of Electroless Nickel Plated Acrylic Resins Microsphere

The metallization of polymer microsphere has attracted attention in recent years due to its wide range of technological applications. In this study, chemical etching with concentrated sulfuric acid and potassium dichromate bichrome (K2Cr2O7) was used to prepare acrylic resin microspheres’ surfaces for high polymer/metal adhesion. Meanwhile, the influence of etching time and temperature on the surface morphology of electroless nickel plated acrylic resin microsphere was investigated. The optimal etching process conditions were identified in this test as follows: etching temperature of 70°C and etching time of 60 ~ 90min. Specular reflection FTIR and scanning electron microscopy was employed to observe the morphology of the nickel plated films and the Ni/polymer interfacial structures. As the results shown, the effect of etching process conditions on the coating thickness and the surface topography of the film was obviously.

Dissolution behaviour of freibergite-tetrahedrite concentrate in acidic dichromate solution

Asgat ore sample with estimated content of 431g/t silver was concentrated by using floatation method and obtained freibergite-tetrahedrite concentrate with 9050g/t Ag, 35.75% Cu, 28.5% Sb and 10.6% Fe, respectively. The dissolution of concentrate in acidic potassium dichromate solution has been investigated with respect to the sulfuric acid and potassium dichromate concentrations and by changing leaching temperature and time. Leaching freibergitetetrahedrite concentrate in dichromate acidic solution (K2Cr2O7-0.1M, H2SO4-0.4M leaching time 4h, leaching temperature 95°С) resulted total amount of leaching of 95.65 % silver, 93.85% copper, 99.86 % antimony and 30.18% iron. DOI: http://dx.doi.org/10.5564/mjc.v14i0.196 Mongolian Journal of Chemistry 14 (40), 2013, p36-40

Technical approaches of a natural dye extracted from Phytolacca americana L.-berries with chemical mordants

Phytolacca americana L. is a large semi-succulent herbaceous plant which reaches three meters in height. It is native to eastern North America, the Midwest, and the Gulf Coast, with more scattered populations in the far West. It is imported into Korea and has been frequently used as a traditional natural drug for diseases such as systemic edema and nephritis. Its berries, that is, fruits are shiny dark purple held in racemous clusters on pink pedicels with a pink peduncle. They are round with a flat indented top and bottom. Immature berries are green, maturing into white and then blackish purple. It is not well known how the berries are used for a natural staining yet. In this study, using Phytolacca americana L.-berries, a natural staining was analyzed. Moreover, due to the broad use of chemical mordants, five different mordants including copper acetate, aluminum potassium sulfate, sodium tartrate plus citric acid, Iron II sulfate and potassium dichromate were combined. Extracted dye from the berries stained silk fabrics with ivory. The original purple color from the berries disappeared and transformed into ivory. Although the silk fabrics were differentially stained by the berries that were combined with mordants of aluminum potassium sulfate, sodium tartrate plus citric acid and potassium dichromate, only differences in lightness and darkness were observed. Interestingly, the combination of the dye from the berries with a mordant of copper acetate and Iron II sulfate induced the staining of the silk fabrics into khaki and dark khaki, respectively. This study is the first systemic report on staining silk fabrics with Phytolacca americana L.-berries and chemical mordants and suggests application of natural products to the fiber industry.