Showing papers on "Potassium dichromate published in 2005"

Determinação de rotina do crômio em fezes, como marcador biológico, pelo método espectrofotométrico ajustado da 1,5-difenilcarbazida

Abstract: This work aims at adjusting the spectrophotometric method of 1,5-diphenylcarbazide for the determination of chromium in feces, as a biological marker. Factors that could interfere with the transformation of chromium (III) into chromium (VI) were tested, as the metal recovery, the sample amount, the amount and the order of use of the oxidant acids of the wet digestion, digestion temperature and digestion time, loss of chromium by volatilization as chromyl chlorid. However the interference of these factors were not statistically determined. In the adjusted method, the sample is classically digested by nitric/perchloric acid mixture leading to the oxidation of chromium (III) to chromium (VI), and an aliquot of the diluted extract is used for reaction with 1,5-diphenylcarbazide; absorbance was measured at 550nm, using 1cm path length optical cuvettes. Potassium dichromate was used as a standard substance to obtain the standard curve ranging from 0.25mg.mL-1 to 2.5mg.mL-1 of Cr2O3 (1mg Cr2O3 o 1.9355mg K2Cr2O7).

Effect of potassium dichromate on renal brush border membrane enzymes and phosphate transport in rats

Abstract: Chromium is widely used in industry but exposure to chromium compounds in the workplace can result in nephrotoxicity. Various nephrotoxicants affect the brush border membrane (BBM) lining the epithelial cells of the proximal tubule, but there have been no studies regarding the effect of potassium dichromate (K2Cr2O7), a hexavalent chromium compound, on renal BBM. In the present work, the effect of administering a single intraperitoneal dose (15 mg/kg body weight) of K2Cr2O7 on rat renal BBM enzymes and inorganic phosphate (Pi) transport was studied. The animals were administered normal saline (control) or K2Cr2O7 and sacrificed 1, 2, 4 and 8 days after treatment. K2Cr2O7 induced reversible damage to the rat kidney function as indicated by serum creatinine (Scr) and urea nitrogen levels. The activities of BBM marker enzymes were significantly decreased in isolated BBM vesicles (BBMV) and homogenates of cortex and medulla on 1, 2 and 4 days after administration of K2Cr2O7 with complete recovery to control values after 8 days. The decrease in the activities of the enzymes was mainly due to changes in maximum velocity (V(max)) values, while the Michaelis constant (Km) remained unchanged. The sodium dependent Pi transport across BBMV was reduced by 50% after treatment with K2Cr2O7. Thus, the administration of a single dose of K2Cr2O7 leads to impairment in the functions of renal BBM. These results suggest that the nephrotoxicity of K2Cr2O7 may be mediated, at least in part, by its effect on renal BBM.

Potassium dichromate initiated polymerization of aniline

Abstract: Potassium dichromate initiated polymerization of aniline in acidified aqueous medium was carried out as a function of parameters such as pH, aniline/oxidant mole ratio, temperature and time. Optimum reaction conditions are outlined for the chemical synthesis of the polymer. Spectral, thermal, electrical and viscosity properties of some selective samples of polyaniline were studied. A reaction scheme has been proposed to elucidate the role of Cr(VI).

Cationic cobaltammines as anion receptors: a convenient synthesis and the X-ray structure of hexaamminecobalt(III) chloride dichromate monohydrate

Abstract: Orange-colored single crystals of hexaamminecobalt(III) chloride dichromate monohydrate, [Co(NH3)6]ClCr2O7·H2O, were prepared by reacting hot aqueous solutions of hexaamminecobalt(III) chloride and potassium dichromate in a 1:1 molar ratio and allowing the mixture to cool slowly to room temperature. The salt was characterized by elemental analyses and spectroscopic studies. A single-crystal X-ray structure determination revealed that the salt crystallizes in space group P21/c with a = 10.0218(9), b = 9.3216(8), c = 16.2203(13) A, β = 112.962(6)°, V = 1395.2(2) A3, Z = 4 and R = 0.0326. In the salt, a strong network of hydrogen bonds (predominantly N–H···O, N–H···Cl–) between the hexaamminecobalt(III) cation, the water molecule, the chloride ion and oxygen atoms of the dichromate ion represents the second sphere coordination and suggests that [Co(NH3)6]3+ may be used as an anion receptor for the dichromate ion.

Toxicity and Bioaccumulation of Hexavalent Chromium in Green Paramecium, Paramecium bursaria

Abstract: The effects of hexavalent chromium on the cell growth of green paramecium, Paramecium bursaria (P. bursaria), were investigated in this study. Two strains (MB-1 and F1 generation) of P. bursaria were incubated in lettuce media supplemented with different concentrations of potassium dichromate under LL (24 hr light), LD (12 hr light : 12 hr dark) and DD (24 hr dark) conditions, and the IC50 values were obtained. The IC50 7-day value showed that the toxicity of potassium dichromate was light-sensitive in both strains of P. bursaria. The results of the toxic effect of chromium on the cell shape of P. bursaria (BWK-4) showed that the body ratio of P. bursaria increased, even if the cells were incubated for 24 hr with 0.5 µM potassium dichromate solution, indicating that the cell shape of P. bursaria is very sensitive to potassium dichromate. The average amount of chromium accumulated in green paramecium ranged from 1.72 to 15.5 pg Cr/cell in a time- and concentration-dependent manner. This finding indicates the possibility of the use of P. bursaria as a biomonitor and bioaccumulator for chromium contaminants in aquatic environments. The experiment with electrical stimuli into the culture of P. bursaria indicated that cells accumulated at the negative electrode, suggesting that P. bursaria carried a positive charge. Thus, because the positive charge does not cause any significant absorption of chromium into the cells, P. bursaria may develop a variety of mechanisms for chromium accumulation in the cell. Further research studies are required to elucidate the mechanism of chromium uptake in P. bursaria.

Studies on extraction of chromium(VI) from acidic solution by emulsion liquid membrane

Abstract: High molecular weight amines, quaternary salts etc. have the potential of removing heavy metal ions including the toxic ones at low concentrations. In the present work an attempt has been made to extract Cr(VI) through emulsion liquid surfactant membrane (or, emulsion liquid membrane-ELM) from it's acidic solution using alamine-336 and caustic soda as extractant and striping reagents respectively. Around 97% extraction of Cr(VI) from aqueous solutions of potassium dichromate through batch experimentations have been achieved. Being crucial to the overall success of the ELM processes, experiments on emulsion stability have also been performed to arrive at a reasonably stable emulsion composition. Effect of various process parameters such as initial solute concentration, concentration of internal phase etc. as also that of pH on extraction of chromium have been investigated.

Comparison on determining the organic matter contents in the soils by different heating methods in the potassium dichromate-volumetric method

Abstract: The precisions and accuracies of the soil organic matter contents tested by three heating methods including the boiling water bath heating 30 min or 60 min and the dilution heating method were compared with the oil bath heating method as a standard conventional method.The results showed that the oxidation adjusting coefficients for above three heating method were 1.16,1.13,and 1.33,respectively.The precision and accurycy of the boiling water bath heating method were as the same as the oil bath heating method in determining soil organic by the potassium dichromate-volumetric method.Because the boiling water bath heating 30 min method is facility and credibility,it can be applied in measurement of soil organic matter.

Synthesis, spectroscopic characterisation and X-ray structure of [trans-Co(en)2(NO2)2]2(Cr2O7)

Abstract: Dark red crystals of bis[trans-dinitrobis(ethylenediamine)cobalt(III)] dichromate, [trans-Co(en)2(NO2)2]2(Cr2O7) have been obtained by slowly allowing to mix the solutions of potassium dichromate and trans-dinitrobis(ethylenediamine)cobalt(III) nitrate in 1:2 molar ratio in aqueous medium. Elemental analyses and spectroscopic techniques (IR, UV/visible, 1H and 13C NMR) were used for characterizing the complex salt. The complex salt crystallizes in the orthorhombic space group Fdd2 with unit cell dimensions a = 24.778(2) A, b = 30.457(2) A, c = 6.5364(5) A, Z = 8, V = 4932.8(7) A3, R1 = 0.0617 and wR2 = 0.1518. X-ray structure determination revealed an ionic structure consisting of cationic cobaltammine [trans-Co(en)2(NO2)2]NO3 and dichromate anion. It is the first crystal structure of this cation with a dianion.

Ultrasonic energised dyeing of wool with Mirabilis jalpa flowers

Abstract: In our research for screening newer natural colorants we have now attempted to dye wool with Mirabilis flowers. The results are excellent with stannic chloride mordant, however, alum, copper sulphate, potassium dichromate, ferrous sulphate and stannous chloride also give fairly good fastness properties.

Chromate Oxidation of α-Nitro Alcohols to α-Nitro Ketones: Significant Improvements to a Classic Method

Abstract: A series of eight alkyl and aryl α-nitro ketones were prepared by the potassium dichromate oxidation of the corresponding nitro alcohols. Short reaction times allowed for the easy isolation of pure nitro ketones that are devoid of starting materials and/or other oxidation side products.

Magnesium and magnesium alloy chemical oxidation process

Abstract: The chemical magnesium and magnesium alloy oxidizing process includes the technological steps of dehydrogenation, chemically deoiling, washing with hot water, washing with cold water, polishing, washing with cold water and chemical oxidization. The chemical oxidizing solution consists of methyl tetrahydroxyl phthalic anhydride, potassium sulfate or aluminum acetate, boric acid, potassium dichromate or sodium dichromate or sodium tripolyhosphate or sodium sulfite, ammonium molybdate or diammonium biphophate, ammonium nickel sulfate, deionized water and optional dithio dipropyl sulfonate in certain proportion. The present invention can obtain chemical oxide film with corrosion rate not more than 3.739 mm/a. In different chemical oxidizing conditions, oxide films of different colors may be prepared. The present invention may be applied in aeronautics, astronautics, electronics, communication, building, automobile and other industry.

Hologram formation reconsidered in dichromated polyvinylalcohol: polymer cross-linking around chromium (V)

Abstract: The photochemical behavior of dichromated polyvinylalcohol (DCPVA) films was analysed upon exposure at 365 nm in connection with the hologram quality recorded in such a photosensitive material. The evolution of both involved species, chromium and polyvinylalcohol, were quantified by implementing an innovative approach. This approach combines the monitoring of the structural modification of the polymeric matrix and the fate of the various chromium species ((VI), (V) and (III)). For the first time, it was established that chromium (V) was at the origin of the cross-linking implied in the hologram formation by acting as a bridge between hydroxyl groups of the polymeric chains. A second unanswered question was also elucidated. The improvement brought by ammonium dichromate with respect to potassium dichromate involves amide groups as additional chelating sites for chromium (V) resulting in the increase of the matrix cross-linking.

Study on Electrokinetic Remediation of Soils Polluted by Chromium

Abstract: A laboratory study was conducted to investigate elec-trokinetically remediation of soils contaminated by chromium. Potassium dichromate was chosen as the pollutant with initial concentration of 100 mg/kg. A constant voltage gradient of 1 DCV/cm was applied and the experiment was operated for 48h. Results showed chromium can be removed by electrokinetic remediation with efficiency up to 81%.

Spectrophotometric Determination of Chromium in Water, and Pharmaceutical Samples Using 1-Naphthol

Abstract: Facile and sensitive spectrophotometric methods for the determination of trace and ultra trace amounts of chromium (VI) are described. 4-aminoantipyrine (APP) reacts with 1-naphthol (NPL) in presence of oxidising agent potassium dichromate in acidic medium to produce red coloured product having λmax of 485 nm. The molar absorptivity and Sandell's sensitivity were 2.07x104 l mol-1 cm-1 and 0.00240 μg/cm2 respectively. The colour is stable for more than 6 h. The system obeys Beer's law in the range, 2-18 μg for determination of chromium (VI). The detection limits of chromium (VI) is 0.048 μg mL-1. The method is highly reproducible and has been applied to the analysis of chromium in synthetic, natural water samples and pharmaceutical preparations and the results compared favourably with the reported method.

Production method of potassium dichromate

Abstract: The invention relates to a production method of potassium dichromate for preparing potassium bichromate K2Cr2O7 from potassium chromate crystal K2CrO4 which comprises, acidifying the potassium chromate slurry, refining through iron and aluminium impurity substance removal, cooling the obtained potassium hydrogen carbonate solution, and recovering potassium chromate. The invention realizes the reuse of potassium carbonate.

Spectrophotometric Estimation Of Sildenafil Citrate In Tablets

Abstract: Two simple, accurate, rapid and sensitive methods have been developed for the estimation of sildenafil citrate in health care medicines. The method A is based on reduction of ferric ions to ferrous ions by the drug, which further in presence of potassium ferricyanide as oxidizing agent produces blue colored complex measured at 715 nm against reagent blank. The chromogen obeyed linearity over the range of 10 to 70I¼g/ml of drug. The method B is based on reduction of ferric ions to ferrous ions by the drug, which further in presence of potassium dichromate as oxidizing agent produces greenish blue colored complex measured at 700 nm against reagent blank. The chromogen obeyed linearity over the range of 50 to 130 I¼g/ml of drug.

Synergistic effects of some other ingredients on liquid sodium aluminate accelerated agent

Abstract: Some other synergistic ingredients were used to advance the performance of the liquid sodium aluminate accelerated agent. It is found that partial hydrolysis polyacrylamide, triethanolamine and potassium dichromate all can form an even and stable solution with the liquid sodium aluminate, and the synergistic ingredients can obviously enhance the effect of the liquid accelerated agent.

Method for producing super conducting heat pipe

Abstract: The production process of superconductive heat pipe includes the following steps: mixing any two of sodium superoxide, potassium dichromate or sodium, and strontium chromate, adding hydrochloric acid to react, adding water while heating to dissolve, cooling to crystallize, adding mercurochrome and dissolving in distilled water to prepare No. 1 medium; mixing any two of sesqui manganese hydride potassium dichromate or sodium, monocrystal silicon, beryllium oxide, barium oxide and sodium peroxide, adding titanium trichloride or butyl Rodan solution, letting stand to laminate, centrifuging to obtain crystal, diluting with absolute ethanol to obtain No. 2 medium; heating the No. 1 medium in metal pipe to exhaust air; adding No. 2 medium into the No. 1 medium, further heating and sealing metal end. Thus prepared superconductive pipe can meet the requirement of large heat supplying system.

A New Method for the Oxybromination of Aromatic Compounds with Copper(II)bromide and Potassium Dichromate

Abstract: A new and mild method for oxybromination of aromatic compounds with CuBr 2 and K 2 Cr 2 O 7 in HOAC is reported.

Method for making glass antifogging agent

Abstract: The invention relates to a method for preparing an anti-fog agent for glass, using polyvinyl alcohol (PVA) as the raw material, by modifying and adding load to the make the anti-fog agent with outstanding effect. Dissolve polyvinyl alcohol (PVA) in hot water to be the indoor temperature and add into isopropyl alcohol (muriatic acid and formaldehyde), agitate for 4h and add into potassium dichromate (ethylsilicate, gama- KH560, muriatic acid), agitate for 8h to make A solution; mix potassium dichromate (ethylsilicate, gama- KH560, muriatic acid) and alcohol by a certain volume, back flow for 6h in 60deg.C to make B solution; place an and B solution for 14days, add B solution into A solution while agitate it, generating anti-fog agent for glass of C solution. The anti-fog agent for glass made by the invention has stable performance, good effect of fog resistance, safety, no pollution, no harm and low cost.

Process for chemically aging certain wood species

Abstract: A process for accelerating the natural aging and darkening of certain reddish-brown tropical wood products. The process uses a chemical solution of potassium dichromate in isopropyl alcohol, which is applied to the surfaces of the wood products. After the chemical reaction has occurred the wood is dried. The resulting wood color is both stable and permanent.

Studies on newer chemical passivation treatment for stainless steel

Abstract: An attempt has been made to develop a chemical passivation treatment for AISI 304 stainless steel based on nitric acid in the presence of various oxidising agents such as sodium molybdate, potassium dichromate and potassium permanganate. The stability of the passive film formed through different chemical passivation treatments has been studied by potential–time measurement in 0·5 M sulphuric acid and the operating parameters of chemical passivation have also been optimised by this technique. Results of the study show that chemical passivation of stainless steel in nitric acid shifts the open circuit potential in the positive direction. Increase of concentration of nitric acid, treatment time and temperature further ennobles the potential. Addition of either dichromate or permanganate ions to nitric acid helps in forming a more stable passive film whereas molybdate, even at higher concentrations does not have any beneficial effect on passive film formation.

Onion shaped fullerene purification process

Abstract: The invention discloses an onion shaped fullerene purification process comprising the steps of acid liquor thermal treatment, potassium dichromate oxidization, extraction thermal treatment, purification through vacuum heat treatment and ball grinding.

Effect of alkali salts on the viscosity of 'kahu' grass black liquor

Abstract: A kahu grass thick black liquor (TBL) produced in the paper manufacturing process causes serious handling problems due to its high viscosity. In the present study, the viscosity of this black liquor (having 50% solid content) has been decreased significantly in acidic medium by the addition of small concentrations (<0.1 M) of various alkali salts such as potassium bromide, potassium thiocyanate, potassium dichromate and potassium permanganate respectively. Parameters related to viscous flow, like temperature and salt concentration were evaluated and the activation energy of the viscous flow was calculated. It is believed that the protonated phenolic hydroxyl groups of the lignin macromolecule, responsible for the elevated viscosity of the black liquor, are prevented from association by the alkali salts that result in reduction of its viscosity.

Temporal limitations in the use of potassium dichromate as a blood preservative for the analysis of organohalogenated contaminants including polybrominated diphenyl ethers, dioxins and PCBs

Abstract: Previous studies described the use of potassium dichromate (K2Cr2O7) to successfully preserve whole blood for up to 34 days at room temperature (20–22°C) for analysis of chlorinated dioxins, dibenzofurans and PCBs. Potassium dichromate has been successfully employed as a preservative for cows’ milk and in a World Health Organization study of human milk. The use of two 100 mg tablets in 40 to 100 mL of whole blood in anticoagulant was found to provide almost identical levels of dioxins, dibenzofurans, PCBs and lipids as found in frozen comparison blood at −70°C which is generally regarded as the gold standard for blood preservation. Potassium dichromate was found to be preferable to 20 and 40% ethyl alcohol for this preservation. This finding opens opportunities for preservation under field conditions in developing countries where neither electricity nor dry ice is available. Not having to use dry ice for shipping also allows more flexibility in the choice of commercial carriers for transporting blood to a...