Showing papers on "Potassium dichromate published in 1989"

Chromium cross-links glutathione and cysteine to DNA

Abstract: The formation of chromium-DNA adducts, and chromium-mediated peptide-DNA or amino acid-DNA cross-links was measured after treatment of calf thymus DNA and defined DNA polynucleotides in vitro with potassium dichromate in the presence of glutathione or cysteine. The level of chromium bound to DNA after reaction with chromium(VI) in the presence of glutathione increased with increasing glutathione concentration to a level of approximately 1.4 x 10(-2) chromium per nucleotide. Glutathione and chromium were associated with the DNA in a 1:1 ratio. Reaction of chromium(VI) with DNA in the presence of cysteine led to a maximal level of chromium binding that was 10-fold lower than that measured with glutathione, with 2-4 cysteine bound per chromium. The thiol-chromium-DNA complexes were stable to dialysis at room temperature against diethylenetriaminepentaacetic acid, orthophenanthroline and ethylenediaminetetraacetic acid. However, when the chromium-DNA complexes were dialyzed against ethylenediaminetetraacetic acid at 37 degrees C to chelate bound chromium, equivalent amounts of chromium and thiol were lost from the DNA, suggesting that thiol was associated with the DNA-bound chromium. These results suggest that chromium mediates cross-linking of cysteine and glutathione to DNA, to form glutathione-chromium-DNA and (cysteine)2-4-chromium-DNA complexes. In order to probe the DNA base and sequence specificity of glutathione-chromium-DNA adduct formation, chromium and glutathione binding to polynucleotides of defined composition was determined. Preferential binding of chromium to guanine-containing polynucleotides was observed. These results suggest that the interaction of chromium with thiol-containing amino acids and peptides may be important in chromium genotoxicity, and indicate that the thiol-activated chromium may target guanine bases in DNA.

Trial of 0.5% versus 0.375% potassium dichromate

Abstract: photosensitive dermatitis. JAm Acad Derm 1986: 15: 1237-1241. 6. Masuda T, Honda S, Nakauchi Y et a!. Patch test: the data of the Allergy Clinic of the Department of Dermatology of Tokyo University Hospital for the past three years. Jpn J Dermatol Ser B 1970: 80: 133. 7. Rudner E J, Clendenning WE, Epstein E. Epidemiology of contact dermatitis in North America. Arch Dermatol 1973: 108: 537. 8. Hannuksela M, Kousa R, Pirila V. Allergy to ingredients of vehicles. Contact Dermatitis 1976: 2: 205. Contact Dermatitis 1989: 21: 351

Effect of ammonia on cod analysis

Abstract: Chemical oxygen demand (COD) is used as a measure of the organic content of wastewater. In this study, interference of ammonia with COD analysis was observed when chloride was present and when a 0.25-N potassium dichromate solution was used to prepare the COD vials. The interference increased with increases in both ammonia concentration and digestion time. The interference was not observed when COD analysis was performed with the COD vials prepared with a 0.025-N potassium dichromate solution, or when chloride was absent

Induction of SOS response in Escherichia coli strain PQ37 by 16 chemical compounds and human urine extracts

Abstract: The SOS Chromotest on Escherichia coli strain PQ37 was used to detect DNA damage induced by 16 chemical compounds and urine samples from smokers and a non-smoking psoriatic patient treated with mineral coal tar. The results confirmed the strong SOS inducing activity of 2-aminoanthracene and benzo[a]pyrene with metabolic activation and N-methyl-N'-nitro-N-nitrosoguanidine, mitomycin C and 4-nitroquinoline-N-oxide without metabolic activation. A weaker response in the absence of microsomal enzymes was observed with hydroxyurea (only at high doses) and the soluble Cr(VI) compounds potassium chromate and potassium dichromate. No effect was observed with ampicillin, cadmium chloride, cyclophosphamide, griseofulvin, the insoluble Cr(VI) compound lead chromate, the soluble Cr(III) compounds chromium nitrate, chromium chloride, chromium potassium sulphate, and the chelating agent sodium nitrilotriacetate. Among the Cr(III) compounds only chromium acetate produced a low but significant increase of SOS inducing activity. Solubilization by nitrilotriacetate of genotoxic Cr(VI) from insoluble lead chromate was observed, whereas no interaction occurred between nitrilotriacetate and the soluble Cr(VI) and Cr(III) compounds. Using urinary XAD-2 extracts, we found the SOS Chromotest poorly sensitive to the mutagens present in urine from tobacco smokers which, on the other hand, were detected by the gene mutation assay in Salmonella typhimurium (Ames test). A urine sample obtained from a psoriatic patient, therapeutically treated with mineral coal tar, had a significant SOS inducing activity with and even without metabolic activation, whereas in the Ames test it was active only in the presence of metabolic activation.(ABSTRACT TRUNCATED AT 250 WORDS)

Etchant for revealing dislocations in II-VI compounds

Abstract: The invention provides an etchant and a method of using the etchant for revealing dislocations on low index planes in group II-VI compounds such as (Hgx Cd.sub.(1-x))Te. The etchant has a composition proportional to 80 ml water, 10 ml of hydrochloric acid, 20 ml of nitric acid, and 8 gm of potassium dichromate. In another embodiment, the concentration of nitric acid is reduced to 0%. The surface of the compound being examined is exposed to the etchant for about 20 second to 6 minutes depending upon the crystallographic plane being examined. The surface is then rinsed in water. For the {111}B plane, additional rinses in a 0.05% solution of bromine in methanol and methanol are used.

Solid state reaction between dichromates and oxalates

Abstract: The thermal investigation of the reaction taking place between dichromates and oxalates in the solid state has been done taking two systems of potassium dichromate-potassium oxalate and sodium dichromate-sodium oxalate. The techniques employed include thermogravimetry, differential thermal analysis, infrared spectroscopy and X-ray diffraction studies. The results indicate a stoichiometric reaction of dichromate and oxalate in 1∶1 ratio to give the corresponding chromate as the sole product.

Changing patterns of contact sensitivity in Sofia.

Abstract: 1237 patients with contact sensitization were patch tested five times with the standard patch test series at 3-year intervals. The study was carried out during the period 1975-1987. The results point out the increasing significance of the most common allergens in the industrially developed countries: potassium dichromate, isopropylaminodiphenylamine, formalin, p-phenylenediamine and nickel sulfate.

On Spontaneous Potential Oscillations and Formation of Structures During the Outer-Currentless Dissolution of Copper in Sulfuric Acid Solutions of Potassium Dichromate

Abstract: Bei der Auflösung dünner Kupferiilme in schwefelsauren Kaliumdichromatlösungen tritt ein oszillierendes Ruhepotential auf. Es bilden sich spontan periodische Ätzstrukturen, wenn die Kupferoberflächen in einer chloridionenhaltigen Lösung vorbehandelt werden. Die Auflösung des Kupfers wird durch die Bildung von Cu(I)-chlorokomplexen beschleunigt, wobei angenommen wird, daß die Cu(l)komplexe als chromatreduzierende Spezies fungieren. Die Konservierung dissipativer Strukturen kommt dadurch zustande, daß während der oszillierenden Kupferauflösung die Randbereiche der ätzenden Areale durch Abdiffusion an Chloridionen verarmen.

Determination of microamounts of carbon in metals by wet chemical oxidation and nonaqueous coulometric titration

Abstract: A method for the determination of mcroamounts of carbon in metals which do not achieve complete combustion has been developed. This method is based on wet chemical dissolution with a mixture of 280ml of 5 to 10M sulfuric acid and 16g of potassium dichromate, with and without the addition of a small amount of copper(II) sulfate in a stream of oxygen, and on nonaqueous coulometric photometric titration of the evolved carbon dioxide. The reagents used for the wet chemical method were highly purified in order to lower the blank value. Microamounts of carbon in sucrose could be determined with good precision and accuracy. Trace amounts of carbon (0.8-166ppm) in iron, low-carbon steels, titanium alloy, indium and gallium were determined precisely and accurately. The blank value and determination limit obtained by the proposed method are lower than those previously obtained by wet chemical dissolution and volumetric titrimetry.

A method of forming a glass intended to be transformed into continuous or staple fibers.

Abstract: The invention relates to a method for adjusting the degree of oxidation-reduction of a glass during its production. According to the invention, which aims glass intended to be transformed into continuous or staple fibers, the degree of oxidation of the glass is obtained by incorporating in the mixture of batch materials at least two oxidizers, one of them being an inorganic nitrate, the other being either a oxygenated manganese compound wherein the manganese oxidation state is greater than 2, potassium dichromate and / or ceric oxide. particular, the invention promotes the recycling of waste products based on glass fibers in the glass batch.

Oxidation and Displacement Reactions with Inorganic Nucleophilic Reagents Activated Through Impregnation onto Zeolites.

Abstract: Zeolite-supported inorganic nucleophilic reagents were prepared by impregnation with their aqueous solutions, followed by calcination, and applied to several liquid-phase organic reactions. The reaction between alkyl bromides and potassium chromate was promoted by zeolites to give aldehydes, although residual water adsorbed on the zeolites caused unfavorable hydrolysis reaction to give alcohols. Zeolites also accelerated the oxidation of alcohols with potassium dichromate and displacement reactions of alkyl bromides with alkali iodides. The product yields were dependent on the type of the zeolites and counter cations of the inorganic nucleophiles.

Short-term toxicity (one- and ten-day gavage) of potassium dichromate in male and female rats

Abstract: This study was undertaken to simulate human exposure conditions that might occur after an accident or spill situation resulting in relatively high levels of dichromate in drinking water. Objectives were to identify health effects that would be associated with such an extreme exposure and provide the USEPA with data that could be utilized to deal with such a situation