Showing papers on "Potassium dichromate published in 1992"
TL;DR: A detailed study was made of the well-known organic carbon determination that is based on measuring the absorbance of the green chromium(III) complex generated when organic matter is oxidized by potassium dichromate in acidic medium as discussed by the authors.
Abstract: A detailed study was made of the well‐known organic carbon determination that is based on measuring the absorbance of the green chromium(III) complex generated when organic matter is oxidized by potassium dichromate in acidic medium The green chromic colour proved to be unstable, turning slowly to a violet colour It was also found that chromic sulphate exerts a catalytic influence on the decomposition of excess dichromate Based on this work, a modified method was developed which is simple, rapid, and very accurate when working under carefully controlled conditions
106 citations
TL;DR: The % of chromium found in the recipient phase ( recipient phase us chromium VI)increased with increasing total chromium concentration indicating a limned reduction ability of the skin in vitro.
Abstract: Chromium permealation studies were performed on full thickness human skin in diffusion cells. AH samples were analysed for the total chromium content by graphite furnace Zeeman-corrected atomic absorption spectrometry. Some samples were analysed by an ion chromatographic method permitting the simultaneous determination of Cr(VI) and Cr(III) as well. The amounts of chromium found in all skin layers were significantly higher when potassium dichromate was applied lo the skin compared with chromium chloride or chromium nitrate. Chromium could only detected in the recipient phase after application of the dichromate solution. Chromium skin levels increased with increasing concentrations of applied chromium salts up to 0.034 M Cr. The amount of chromium in recipient phase and skin layers increased with increasing pH when the applied solution contained potassium dichromate. This was ascribed to a decreased skin barrier function of the skin. The amount of chromium found in all skin layers after application of chromium chloride decreased with increasing pH due to lower solubility of the salt. The % of chromium found in the recipient phase us chromium VI)increased with increasing total chromium concentration indicating a limned reduction ability of the skin in vitro.
97 citations
TL;DR: In this paper, an efficient and reliable method was developed for the accurate determination of osmium abundance in molybdenite (MoS2) by isotope dilution mass spectrometry.
Abstract: An efficient and reliable method was developed for the accurate determination of osmium abundance in molybdenite (MoS2) by isotope dilution mass spectrometry. The sample solution of molybdenite was prepared by acid decomposition using the microwave digestion technique with addition of potassium dichromate (K2Cr2O7) as oxidizing agent and osmium in the sample solution was purified by distillation. There was no change in the ratios of 187Os derived from molybdenite relative to 192Os of an osmium standard with progress of distillation, indicating that isotopes of osmium derived from the two sources were completely homogenized. The precision of the osmium abundance obtained in the developed method was 1%(1σ). The technique was applied to a natural molybdenite sample for Re—Os age determination and the result was in good agreement with that obtained by the U—Pb method for zircon.
47 citations
TL;DR: Contact sensitivities of three well known metal allergens were examined using the local lymph node assay in CBA/N mice, F344 rats and Hartley guinea pigs and there was no significant difference in stimulation indices among the different culture conditions.
30 citations
TL;DR: Diatoms were generally found to be the most sensitive species in natural marine phytoplankton and five species of marine microalgae and the effects of DCA and DCP on the growth rate of some species were also investigated.
23 citations
TL;DR: In this paper, a synergistic interference has been observed with the determination of aluminium by electrothermal atomic absorption spectrometry when phosphorus is present in the sample along with alkali or alkaline earth metals.
Abstract: Brain tissue is rich in phosphorus and alkali and alkaline earth metals. A synergistic interference has been observed with the determination of aluminium by electrothermal atomic absorption spectrometry when phosphorus is present in the sample along with alkali or alkaline earth metals. For the determination of aluminium in human brain samples, potassium dichromate was found to be an effective chemical modifier. The concentration of aluminium in National Institute of Standards and Technology (NIST) Standard Reference Materials (SRMs) Citrus Leaves (SRM 1572), Oyster Tissue (SRM 1566a) and in National Institute for Environmental Studies (NIES) Certified Reference Material (CRM) No. 6 Mussel were determined. Values of 76.6 ± 4.2, 86.8 ± 0.5 and 55.5 ± 10.1 µg g–1 were obtained before the use of the modifier, and 88.2 ± 6.2, 197.7 ± 6.8 and 215.0 ± 12.5 µg g–1 after the use of potassium dichromate as chemical modifier for Citrus Leaves, Oyster Tissue and Mussel, respectively. The concentrations of aluminium determined with the use of potassium dichromate as chemical modifier are in good agreement with the certified values in the standard samples. The aluminium contents of several human brain samples were also determined. Values ranged from 6.2 to 9.8 µg g–1 of aluminium (dry mass basis).
15 citations
TL;DR: It was evident that the exposure of fish to chromium led to clotting defects that caused internal bleeding.
11 citations
TL;DR: In this article, the effects of oxidation on gel-spun ultra-high-modulus and ultra high-molecular-weight polyethylene (UHMWPE) fibres were investigated.
11 citations
TL;DR: In this paper, the dissolution of Ni 3 S 2 in sulphuric acid solutions containing potassium dichromate was investigated and the effect of temperature, dichromates ion concentration, sulphur acid concentration and particle size has been examined.
9 citations
Journal Article•
TL;DR: The results suggest that the chelating agents tested may be useful in the treatment of intoxications due to hexavalent chromium, but there is the difference in the therapeutic effects of the che lating agents owing to the time intervals after the administration of the metal.
Abstract: The effects of the chelating agents, L-cysteine ethyl ester (LCEE), L-cysteine methyl ester (LCME), N-acetyl-L-(+)-cysteine (NAC), 2,3-dimercapto-1-propanesulfonic acid (DMPS), N-(2-mercaptopropionyl)-glycine (MPG), and 2,3-dimercaptosuccinic acid (DMSA), on the distribution, excretion and hepatotoxicity of ip injected hexavalent chromium were studied in male mice. The chelating agents (500 mg/kg) were injected iv as single doses given immediately or 30 min after potassium dichromate (20 mg Cr/kg) as hexavalent chromium was administered. When the chelating agents were injected immediately after the metal compound was administered, LCEE, LCME, NAC, DMPS, and MPG reduced the chromium contents in the liver and kidney, and facilitated the urinary excretion of chromium. The liver injury induced by chromium, which was evaluated by serum ornithine carbamyl transferase (OCT) activity, was prevented significantly by LCEE, LCME, DMPS, and MPG. On the other hand, when these chelating agents were injected at 30 min after the chromium administration, only DMSA could prevent the liver injury induced by the metal, and decreased the chromium contents in the liver. However, when DMSA was given at 3 hr after the metal administration, there was no therapeutic effect on them. These results suggest that the chelating agents tested may be useful in the treatment of intoxications due to hexavalent chromium, but there is the difference in the therapeutic effects of the chelating agents owing to the time intervals after the administration of the metal.
8 citations
TL;DR: Chromate-induced cytotoxicity evaluated by inhibition of cell growth at 3 days of incubation was diminished by all of the thiol compounds tested when the cells were incubated in MEM with 2.5 to 10.0 microM chromate and 25 to 100 microM thiol compound.
Abstract: The effects of several thiol compounds on the cytotoxicity induced by chromate (potassium dichromate) were examined. HeLa cells were incubated in Eagle's minimum essential medium (MEM) with or without the chromate alone, or with both chromate and any one of L-cysteine ethyl ester (LCysEE), L-cysteine methyl ester (LCysME), N-acetyl-L-(+)-cysteine, 2,3-dimercaptosuccinic acid (DMSA), 2, 3-dimercapto-1-propanesulfonic acid (DMPS), or dithiothreitol. After a given period of incubation, the number of viable cells was counted using the trypan blue exclusion test and the chromium content of the cells was estimated by atomic absorption spectrophotometry. The results obtained were as follows. 1) Chromate-induced cytotoxicity evaluated by inhibition of cell growth at 3 days of incubation was diminished by all of the thiol compounds tested when the cells were incubated in MEM with 2.5 to 10.0 microM chromate and 25 to 100 microM thiol compounds. 2) All of the thiol compounds produced a concentration-dependent reduction of chromate when a solution of the thiol compound (12.5 to 100 microM) was mixed with a solution of chromate (10 microM) in distilled water. 3) When cells were incubated in MEM with both 10 microM chromate and 25 to 100 microM thiol compounds, the chromium content of the cells at 6 hr of incubation was decreased in a concentration-dependent manner. 4) When these thiol compounds were added to MEM 1 hr before or after chromate, no or little protective effects of these thiol compounds against chromate-induced cytotoxicity and chromium uptake by the cells were observed.(ABSTRACT TRUNCATED AT 250 WORDS)
TL;DR: A simple spectrophotometric method is introduced for the determination of carbimazole in drug formulation and the accuracy of the method was tested by a statistical comparison with the British Pharmacopeia official method.
Abstract: A simple spectrophotometric method is introduced for the determination of carbimazole in drug formulation. The method requires the use of 16mg ml-1 potassium dichromate, 0.5M sulfuric acid and heating at 90°C for 25min. The method is easily applied to the determination of carbimazole in tablet formulations. The accuracy of the method was tested by a statistical comparison with the British Pharmacopeia official method.
TL;DR: In this article, secondary particle mass spectrometry has been used for the first time to determine the oxidation state and depth distribution of chromium on and in wool fibres, and it has been shown that the absolute concentration of the chromium in a surface layer 50 nm thick became enriched with chromium by a factor of two compared with the bulk fibre.
Abstract: Secondary particle mass spectrometry has been used for the first time to determine the oxidation state and depth distribution of chromium on and in wool fibres. Wool tops were dyed with 4% o.w.f. CI Mordant Black 11 and aftertreated with 1% o.w.f. potassium dichromate, and wool samples treated in a blank dyebath aftertreated with 6% o.w.f. potassium dichromate were analysed. It could be shown that the absolute concentration of chromium in a surface layer 50 nm thick became enriched with chromium by a factor of two, compared with the bulk fibre. Chromium in the hexavalent oxidation state was found to be mainly present in the outermost part of the fibres, while trivalent chromium was dominant inside the fibres.
TL;DR: The kinetics of the reaction of tungsten and potassium dichromate has been studied by thermal analysis in this paper, showing that the activation energy is an order of magnitude greater than that determined by combustion studies.
Patent•
26 Nov 1992TL;DR: In this article, the clogging of the oxide layer, obtained by chromic anodization, was carried out under the following conditions: Composition of the bath: base: demineralized water, potassium dichromate or sodium: 8 to 12 grams per liter, pH adjusted to: 4.5 to 6.5 by a suitable addition of caustic soda.
Abstract: To simultaneously obtain good corrosion resistance and good adhesion of the paint, the clogging of the oxide layer, obtained by chromic anodization is carried out under the following conditions: Composition of the bath: base: demineralized water, potassium dichromate or sodium: 8 to 12 grams per liter, pH: adjusted to: 4.5 to 6.5 by a suitable addition of caustic soda. Bath temperature: 75 to 85 ° C. Immersion time: sufficient to ensure a hydration rate of the alumina coating of between 8 and 15%.
TL;DR: In this paper, the reaction rate is first-order with respect to Cr(VI) and depends linearly on the HClO{sub 4} concentration in the aqueous phase, but reaction rate decreases with the amount of alcohol in the reverse micelles.
Abstract: Oxidation with potassium dichromate in perchloric acid medium of the alkanols 1-butanol, 1-hexanol, and 1-octanol, components of sodium dodecyl sulfate reverse micelles in alkanols, has been studied. The reaction rate is first-order with respect to Cr(VI) and depends linearly on the HClO{sub 4} concentration in the aqueous phase, but the reaction rate decreases with the amount of alcohol in the reverse micelles. To explain the kinetic results it is necessary to consider the intermicellar exchange of the reactants, which could depend on the thickness of the layer where the surfactant and the alcohol are located.
Patent•
08 Jul 1992
TL;DR: The tripterygium wilfordii lactone alcohol that is richly contained in a plant, triperygium wilfordii as discussed by the authors, is used to prepare a tripteryga wilfordi lactone ketone having high medicinal value through oxidation.
Abstract: The tripterygium wilfordii lactone alcohol that is richly contained in a plant, tripterygium wilfordii, is used to prepare a tripterygium wilfordii lactone ketone having highter medicinal value through oxidation The technological steps include dissolving raw material in the solvent of ethyl ether or acetone, addition of oxidant such as CrO3 or potassium dichromate or sodium dichromate, or the complex of pyridine-chromium trioxide under the existance of assistant of pyridine or sodium acetate, washing the reaction resultant with the solution of sodium carbonate and water in turn, drying it with anhydrous sodium sulfate, concentration, and lamino-educing separation or recrystallization to abtain the product
TL;DR: In this paper, a chemical means to quantitatively measure mustiness in stored grains is proposed based on the observation that the fungi Aspergillus flavus, A. glaucus, and A. niger produced ethanol in direct relation to the increase in the mustiness odor produced.
Abstract: A chemical means to quantitatively measure mustiness in stored grains is proposed. It is based on the observation that the fungi Aspergillus flavus, A. glaucus, and A. niger produced ethanol in direct relation to the increase in the mustiness odor produced. A small glass cylinder is filled with silica gel coated with potassium dichromate. When a measured volume of air from the storage bin is passed through the cylinder the ethanol present reduces the orange dichromate to green chromium (III). The length of the green portion is proportional to the amount of ethanol and hence the mustiness present. A portable and inexpensive instrument is proposed.
TL;DR: Brains of small, adult laboratory animals, fixed by formalin-perfusion, and cut into pieces usually 2-3 mm thick X 3-5 mm2 are placed into a solution containing 7% aqueous solution of potassium dichromate, giving high quality impregnation and it takes about one week to complete.
Abstract: Brains of small, adult laboratory animals, fixed by formalin-perfusion, and cut into pieces usually 2-3 mm thick X 3-5 mm2 are placed into a solution containing: 7% aqueous solution of potassium dichromate 100 ml, 995% ethyl alcohol 40 ml, concentrated formalin 10 ml, distilled water 50 ml, for 24 hours The process is repeated with a freshly prepared solution for another 24 hours The pieces are then transferred to a 35% aqueous solution of potassium dichromate for 48 hours, and then to a 1% aqueous solution of silver nitrate for 48 hours Frozen or celloidin sections 70-100 microns in thickness are put into 90% and then into 100% ethyl alcohol for 30 minutes respectively, creosote-benzene (1:1), benzene and mounted with or without cover glass applying Entellan neu This procedure gives high quality impregnation and it takes about one week to complete
TL;DR: In this article, the authors make a comparison between the use of thermal analysis and spectrophotometry for the determination of extent of reaction, which is the starting point for kinetic investigations.