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Potassium dichromate is widely used in various laboratory and industrial applications. Vitamin C and melatonin are well-known antioxidants. Study the microscopic and morphometric alterations in the thyroid gland in adult male albino rats after the administration of potassium dichromate for successive 2 months and also to assess the possible protective effect of vitamin C versus melatonin on these changes. Sixty adult male albino rats were randomly divided into four main groups. Group I (The control group). Group II received potassium dichromate (25 mg/kg/day) dissolved in distilled water by intraperitoneal (i.p) injection for 2 months. Group III received the same dose of potassium dichromate with vitamin C (120 mg/kg/day) orally through an intragastric intubation. Group IV received the same dose of potassium dichromate and melatonin (10 mg/kg/day) as an i.p injection. Thyroid gland samples were prepared for light and electron microscopic studies. Potassium dichromate group demonstrated congested blood vessels, follicular hyperplasia, follicular enlargement with degenerated lining cells that were exfoliated in the lumen. The parafollicular cells appeared with darkly stained nuclei. PAS reaction showed weak reaction in the colloid with an abnormal pattern of vacuolization. A highly significant increase in the percentage area of fibrosis was detected in Mallory trichrome sections. Ultrastructurally, follicular cells and parafollicular cells appeared irregular in shape with dark, small heterochromatic nuclei. Small, electron-dense granules in the parafollicular cells were found. Potassium dichromate and vitamin C-treated group III showed partial improvement of the thyroid gland. The PAS reaction showed that nearly all the follicles were more or less similar to those of the control group. A significant decrease in the percentage area of fibrosis in group III was found as compared to those in group II. Potassium dichromate and melatonin-treated group showed that the thyroid gland was nearly similar to that of the control group. Vitamin C and melatonin could partially protect against potassium dichromate induced changes in the thyroid gland and the protective effect of melatonin was better than that of vitamin C. [ABSTRACT FROM AUTHOR]

Methanesulfonic acid was proven to be an alternative lixiviant for copper leaching from chalcopyrite with hydrogen peroxide as an oxidant. Two alternative oxidants, dichromate and nitrate, were studied for the copper dissolution from chalcopyrite, a refractory copper sulfide mineral. During chalcopyrite leaching tests, both oxidants achieved the copper extraction above 90% in 30 g/L methanesulfonic acid at 75oC. The activation energies in dichromate and nitrate leaching systems were 23 and 43 kJ/mol, classified as mass transfer and chemical reaction-controlled mechanism, respectively. The XRD analysis of a leached residue showed a formation of K-Cr-jarosite from methanesulfonic acid-dichromate system. Methanesulfonic acid with nitrate leaching system could be the most effective and sustainable for chalcopyrite leaching based on the comparative investigation. [ABSTRACT FROM AUTHOR]

A new 1,3-distal diphenyl(4-piperidin)methanol-appended calix[4]arene derivative 3 has been successfully synthesized and characterized using FTIR, NMR and elemental analysis techniques. Synthesized 1,3-distal diphenyl(4-piperidin)methanol-appended calix[4]arene derivative 3 has been then grafted onto [3-(2,3-epoxypropoxy)-propyl]-trimethoxysilane-modified Fe3O4 magnetic nanoparticles to produce 1,3-distal diphenyl(4-piperidin)methanol-substituted calix[4]arene derivative-grafted EPPTMS-MN (4). The structure and surface morphology of 1,3-distal diphenyl(4-piperidin)methanol-substituted calix[4]arene derivative-grafted EPPTMS-MN have been determined by a combination of FTIR, transmission electron microscopy (TEM) and thermogravimetric analysis (TGA) techniques. Moreover, anion binding capabilities of 1,3-distal diphenyl(4-piperidin)methanol-substituted calix[4]arene derivative-grafted EPPTMS-MN toward HCr2O7-, and H2AsO4- ions have been evaluated. The results indicate that 1,3-distal diphenyl(4-piperidin)methanol-substituted calix[4]arene derivative-grafted EPPTMS-MN exhibited 80% sorption efficacy toward Cr(VI), whereas ∼8% sorption efficacy for As(V) was obtained. [ABSTRACT FROM AUTHOR]

In the present article a comparative extraction efficiency of dichromate by a calix[4]arene derivative (d) and a newly synthesized calix[4]arene appended Amberlite XAD-4 resin (5) are reported. The liquid and solid phase extraction methods have been applied to ascertain the extraction efficiency of both the calix[4]arene derivative and the resin. Different parameters have been optimized such as pH, dosage, concentration, and temperature. Analysis of experimental data has been carried out by log-log plot analyses and the determination of characteristic parameters of each isotherm model such as Freundlich, Langmuir, and Dubinin-Radushkevich (D-R). The kinetic adsorption experiments show that the adsorption process follows pseudo second order kinetics. The adsorption mechanism has been investigated by Reichenberg (R-B) and Morris-Webster equations. From the thermodynamic parameters it is concluded that the adsorption process is endothermic and spontaneous in nature at higher temperature. The results show that the resin-5 has good capability to efficiently remove dichromate from aqueous media. [ABSTRACT FROM AUTHOR]

The reaction of the common pain reliever acetaminophen (paracetamol, 4-acetamidophenol) with dichromate was investigated over time under conditions that simulate wastewater disinfection. The occurrence of the acetaminophen in the water bodies, especially in drinking water resources, has received considerable attentions. In situ chemical oxidation is a promising cost-effective treatment method to remove acetaminophen from water body as it degrades the drug to large extent. Experimental results indicate that the reaction is second order overall and first order with respect to both dichromate and acetaminophen, and has activation energy of 14.1 kJ/mol. The second-order rate constant ranges from 1.56 × 10-3 to 13.4 × 10-3 min-1 at temperature from 35 to 65°C. The acetaminophen degradation rates can be accelerated through increasing reaction temperature and oxidant concentration. The reaction under acid conditions was slightly faster than under alkaline or neutral conditions. Two of the products were unequivocally identified as the toxic compounds 1,4-benzoquinone and ammonium ions. These results demonstrate that acetaminophen is likely to be transformed significantly into toxic product if dichromate is used as an oxidizing agent during wastewater treatment. [ABSTRACT FROM AUTHOR]

The reaction of tris(ethylenediamine)nickel(II) dichloride dihydrate with potassium dichromate or potassium chromate results in the formation of mixed metallic compounds tris(ethylenediamine)nickel(II) dichromate [Ni(en)3][Cr2O7] (1) (en = ethylenediamine) and tris(ethylenediamine)nickel(II) chromate [Ni(en)3][CrO4] (2). Both compounds were characterized by analysis, spectra, magnetic susceptibility, and the structure of 1 was determined. [Ni(en)3][Cr2O7] (1) crystallizes in the centrosymmetric monoclinic space group P2(1)/c and its structure consists of a [Ni(en)3]2+ dication and a dichromate dianion, with all the atoms situated in a general position. Two carbons of one coordinated (en) in 1 and the hydrogens attached to the amine nitrogen in the same ligand are disordered over two positions. In the crystal structure, tris(ethylenediamine)nickel(II) cations are linked to the [Cr2O7]2- anions with several weak hydrogen bonding interactions resulting in an extended network. The χ versus T plots of 1 and 2 reveal simple paramagnetic behavior. [ABSTRACT FROM AUTHOR]

Two new calix[4]arene-based polymeric resins were synthesized via nucleophilic substitution reactions involving 5,11,17,23-tetrakis(N-piperidinomethyl)-25,26,27,28-tetrahydroxycalix[4]arene ( 2 ) and 5,11,17,23-tetrakis[4-carboethoxy-N-piperidino]-25,26,27,28-tetrahydroxycalix[4]arene ( 4 ) as precursors with Merrifield resin. Extraction studies were performed by liquid–liquid extraction and solid–liquid adsorption procedures. The monomeric compounds showed excellent extraction ability toward dichromate in liquid–liquid extraction systems. Polymeric resin 3 with calixarene moieties exhibited high adsorption properties, while resin 5 showed lower adsorption of dichromate in solid–liquid extractions. [ABSTRACT FROM AUTHOR]

A wide variety of sulfides are efficiently oxidized to their corresponding sulfoxides and sulfones in excellent yields using n-butyltriphenylphosphonium dichromate (BTPPDC) in the presence of aluminium chloride in acetonitrile solution and under microwave irradiation. In addition, selective oxidation of sulfides in the presence of functional groups such as a carbon–carbon double bond, ketone, oxime, aldehyde, ether, and acetal can be considered as a noteworthy advantage of this method. [ABSTRACT FROM AUTHOR]

The article studies the promotion of wool dyeing with chrome dyes at temperature levels of 90 degrees Celsius. Glucose is used in the chroming stage to save energy and minimize wool damage without affecting the dyed wool's fastness properties. The pros and cons of the dyeing process is also discussed.

A variety of aliphatic, aromatic, and heteroaromatic thiols were rapidly and cleanly converted to their corresponding disulfides in excellent yields using n-butyltriphenylphosphonium dichromate (BTPPDC) in acetonitrile solution under solvent-free conditions and microwave irradiation. Selective oxidation of thiols in the presence of other oxidizable functional groups, such as alcohol and sulfide, is a noteworthy advantage of this method. [ABSTRACT FROM AUTHOR]

This article describes an efficient and easy method for oxidation of sulfides 1 to their corresponding sulfoxides 2 with 1-butyl-4-aza-1-azoniabicyclo[2.2.2]octane dichromate (BAAOD) under nonaqueous conditions in high yields. [ABSTRACT FROM AUTHOR]