Showing papers on "Potassium dichromate published in 1990"

Contact sensitization of mice to nickel sulphate and potassium dichromate.

Abstract: The ability of nickel sulphate and potassium dichromate to induce contact sensitization in mice has been investigated. Topical exposure of mice to 0.5% potassium dichromate in dimethylsulphoxide (DMSO) under occlusion resulted in specific contact sensitization in each of 7 experiments. Although sensitization to nickel sulphate under the same conditions was weak and somewhat variable, evidence for significant levels of contact allergy was obtained in 4 of 7 experiments. In addition, repeated topical application of both nickel sulphate and potassium dichromate in DMSO was found to result in the induction of lymphocyte proliferative responses in lymph nodes draining the site of exposure. These data indicate that epicutaneous exposure to both metal salts may cause specific contact sensitization in mice.

Risk assessment for selected xenobiotics by bioassay methods with higher plants

Abstract: Different bioassays with higher plants were approved for use in a bioassay procedure for testing of xenobiotics according to the German Chemicals Act. Selected environmental pollutants (atrazine, cadmium chloride, 2,6-dichlorobenzonitrile, pentachlorophenol, potassium dichromate, thiourea), all from a list of reference chemicals, were tested with these methods. Dose-response curves for growth of oats and turnips were evaluated in soil and vermiculite (nonsorptive substrate), and availability to plants was calculated by comparing the EC50 values for one chemical in both substrates. The most active chemical was atrazine, followed by 2,6-dichlorobenzonitrile, pentachlorophenol, potassium dichromate, cadmium chloride, and thiourea. The least available compound to plants was pentachlorophenol, tested with turnips (Brassica rapa var.rapa). The strongest inhibition of germination, demonstrated in an in vitro assay with garden cress (Lepidium sativum), was found with 2,6-dichlorobenzonitrile, the lowest with atrazine. The effect of an extended exposure of the plants to the chemicals was evaluated in a long-term bioassay with oats (Avena sativa) in hydroponic culture. Several dose-response curves during the growing period were derived. It was found that the EC50 values for atrazine and thiourea decreased markedly during the first four weeks; thereafter the changes were much smaller. As an overall conclusion, a bioassay procedure is proposed that can be included in the graduated plan recommended by the German Chemicals Act.

Dose-response relationships for topically applied antigens

Abstract: Patch-test responses to serially diluted nickel sulphate and potassium dichromate solutions in patients with nickel and chrome sensitivity were assessed by pulsed A-scan ultrasound to determine skin thickness and laser-Doppler flowmeter techniques to evaluate blood flow, as well as clinical scoring. There was a relationship between the dose of antigen and the test responses as measured by ultrasound and laser-Doppler flowmeter techniques in both nickel and chrome sensitive patients. Our data suggest that both techniques may be useful in the detection of allergic contact dermatitis in which there is a doubtful patch-test reaction as well as in experimental sensitization studies.

Chemical indicator that includes potassium dichromate and urea and method of using the same to detect hydrogen peroxide

Abstract: The present invention provides a chemical indicator for the detection of hydrogen peroxide. A composition containing an aqueous solution of potassium dichromate is applied to a porous substrate. The reaction between the dichromate and chromate ions present in solution and hydrogen peroxide is accompanied by a dramatic color change which is visible to the naked eye. The initial color of the potassium dichromate solution may be enhanced by adjusting the pH of the solution to be basic. The rate of reaction between the dichromate and chromate ions and the hydrogen peroxide may be increased by the addition of the humectant urea to the potassium dichromate solution.

Effects of Toxic Substances on Natural Bacterial Assemblages Determined by Means of [3H]Thymidine Incorporation

Abstract: The effects of 3,5-dichlorophenol, 2,4-dinitrophenol, and potassium dichromate on natural bacterial assemblages were examined by means of [3H]thymidine incorporation into trichloroacetic acid-insoluble material. Results from a large number of coastal marine and freshwater samples suggest the following. (i) The effects of the three toxicants included reductions in the bacterial cell number as well as changes in rates of [3H]thymidine incorporation and in [3H]thymidine incorporation per cell. The concentrations that inhibited [3H]thymidine incorporation by 50% ranged from 3 to 11 mg liter−1 for 3,5-dichlorophenol, 6 to 10 mg liter−1 for 2,4-dinitrophenol, and 21 to 123 mg liter−1 for potassium dichromate, with a tendency to higher values in bacterial assemblages from more eutrophic environments. (ii) The effects of 3,5-dichlorophenol and potassium dichromate determined by [3H]leucine incorporation into bacterial protein were similar or larger than those obtained from [3H]thymidine incorporation. (iii) Two to four hours of exposure to the toxicants was necessary before stable maximum effects were found in [3H]thymidine incorporation. (iv) Storage of natural environmental samples should be avoided, since tests with water stored for 1 to 3 days sometimes produced results different from results obtained from in situ tests. (v) The effects of 3,5-dichlorophenol, 2,4-dinitrophenol, and potassium dichromate on natural bacterial assemblages were relatively constant during periods with different growth rates in the assemblages, during various periods of the year, and between samples from freshwater and marine localities. With some precautions, [3H]thymidine incorporation can be used as a quick and sensitive method for determining the effects of toxicants on aquatic bacterial assemblages from natural environmental samples.

Hypersensitivity to dichromate among asymptomatic workers in a chromate pigment factory.

Abstract: Hypersensitivity to chromate, as well as nickel and cobalt, salts can present as bronchospasm (!) or acute asthma (2), in addition to allergic contact dermatitis or urticaria (1, 2). Not all sensitized persons are symptomatic, though they may become so on increased exposure (3). We attempted to determine the chromium sensitivity level, independent of clinical symptoms, among workers in a chromate pigment factory. This plant produces chromium yellow: lead sulfochromate, lead chromate, basic lead chromate (lead sulfochromate enriched with molybdenum). The workers are exposed to chromium salts by inhalation and by skin contact. The most heavily exposed persons are supposed to wear gloves and a face mask. The study was performed on 29 male volunteers in the factory, of various ages. No respiratory or dermatologic symptoms were observed prior to the tests. We applied the following patch tests recommended in the European standard series: potassium dichromate (0.5% pet.), cobalt chloride (I% pet.), nickel sulfate (5% pet.). Patch tests were applied on the back at the end of the working week (Friday afternoon), and removed after 48 h. A 1st reading was made then and a 2nd one 24 h later. 6 persons showed positive reactions to dichromate and 6 others to nickel. 3 of these 12 individuals

Observations on the contrasting reaction of some electron dense stains applied on epoxy-embedded tissue sections.

Abstract: Epon sections from glutaraldehyde-fixed rat bone marrow were treated with aqueous solutions of the following electron contrasting agents: uranyl acetate, ruthenium red, potassium permanganate, potassium dichromate, stannous chloride, palladium (II) chloride, sodium molybdate, phosphomolybdic acid, molybdenum heteropolyblue, phosphotungstic acid, iron(II)-phenanthroline, aluminium-hematoxylin, mercurochrome, cuprolinic blue, and sirius light turquoise blue. At the ultrastructural level, a high degree of electron opacity was always observed in mast cell granules and the crystalline inclusion (internum) of eosinophil granules. The chromatin revealed a somewhat lower and variable contrasting reaction, while the matrix (externum) of eosinophil granules appeared with scarce or no contrast. This pattern of electron opacity showed no correlation with the type of agent used; therefore, it can be assumed that binding processes based on the own chemical reactivity of the compounds are rather of secondary importance. The differential epoxy resin embedding of cell structures and the variable access of aqueous reagents through the non-polar plastic could be the predominant factors which account for these contrasting reactions.

On crystal growth of ammonium and potassium dichromate. A study of the shubnikov effect

Abstract: Growth and equilibrium forms of ammonium (A2/a) and potassium dichromate (P 1) have been calculated by means of the Fourier transform method of crystal morphology. Twin laws of potassium dichromate and heteroepitaxial intergrowth of both substances can be explained by partitions of space. According to Shubnikov the (001) planes of potassium dichromate crystals grown in aqueous solutions are always smooth, the parallel opposite planes, however, roughened. Wagner observed that this effect only occurs at temperatures shortly above or below 25 °C. The present investigation has shown that roughening of (001) appears at 25 °C after addition of potassium chromate to the potassium dichromate solutions. This means that the one-sided intergrowth can be explained by a stereospecific adsorption of polychromates. Solution additions like potassium permanganate and Chromotrope 2B generate roughenings on both {001} faces. X-Ray diffraction investigations can be interpreted in such a way that the intergrown plates are mirror symmetric oriented to two planes being normal to the a- and b-axes. This is in accordance with repeated formation of intergrown plates. Theoretische Wachstums- und Gleichgewichtsformen von Ammonium- (A2/a) und Kaliumdichromat (P 1) wurden mit Hilfe der Fouriertransformationsmethode der Kristallmorphologie berechnet. Die bekannten Zwillingsgesetze von Kaliumdichromat und die heteroepitaktischen Verwachsungen beider Substanzen lassen sich aus dreidimensionalen Wirkungsbereichsteilungen ableiten. Nach Schubnikow ist die (001)-Flache von Kaliumdichromatkristallen stets glatt, die parallele Gegenflache immer aufgerauht. Dieser Effekt wird nach Wagner allerdings nur unterhalb bzw. oberhalb 25 °C beobachtet. Nach Zugabe von Kalumchromat zu Kaliumdichromatlosungen treten die Aufrauhungen auch bei 25 °C auf. Die einseitigen Aufwachsungen beruhen offensichtlich auf einer stereospezifischen Adsorption von Polychromaten. Verunreinigungen wie Kaliumpermanganat bzw. Chromotrop 2B fuhren zu Aufrauhungen beider Flachen. Rontgenbeugungsuntersuchungen lassen den Schlus zu, das die Aufwachsungen auf (001) spiegelbildlich zu Ebenen orientiert sind, die senkrecht zu den a- und b-Achsen verlaufen. Dies steht nicht im Widerspruch zu der wiederholten Plattchenbildung.

Bleached Holograms Produced by Fixation-free Method; Recording and Reconstruction at 442 nm Using Kodal 649F Plates

Abstract: Properties of bleached phase holograms using Koak 649F spectroscopic plates have been investigated. Recording and reconstruction is done at 442 nm. The diffraction efficiency has been increased by using four known different developers and four bleaches suitable for fixation-free method. Plots are given of the diffraction efficiency and scattering vs exposure (relative units). Maximum diffraction of about 8.7% has been achieved using Kodak D-19 developer with potassium dichromate plus concentrated sulphuric acid and potassium iodide bleach. Kodak HRP developer with potassium sulphuric acid and potassium iodide bleach. Kodak HRP developer with potassium dichromate plus concentrated sulphuric acid bleach process also gives nearly the same results.

[18] – Silver Impregnation Method for Frozen Sections of Human Nervous Tissue Using Ammoniacal Silver–Dichromate Solution

Abstract: Publisher Summary This chapter describes a new silver impregnation method for nervous tissue in frozen sections of the human central nervous system in which ammoniacal silver-dichromate solution is used. The procedure of this method involves frozen sections that are 20-30 μm thick and are obtained from tissue blocks fixed in formalin. These are placed in ammoniacal silver-dichromate solution, 10% (w/v) aqueous solution of silver nitrate, and ammoniacal silver solution, which is then reduced in 20% (v/v) formalin, toned in 1% (w/v) aqueous solution of gold chloride, fixed in 5% (w/v) aqueous solution of sodium thiosulfate, dehydrated, and mounted. In this procedure, chromium (Cr) and silver (Ag) ions can be applied simultaneously to tissue sections and fine fibers display colors ranging from purple to dark purple on an almost colorless background. Gold treatment may be omitted. This procedure has given good results for the tissues that have been fixed in formalin for several years. The principal steps in common Golgi-type silver impregnation methods involve aldehyde fixation, immersion of tissue blocks in potassium dichromate, and subsequent immersion in silver nitrate to deposit precipitates in tissue blocks.