Showing papers on "Potassium dichromate published in 1994"

Reaction of chromium(VI) with ascorbate produces chromium(V), chromium(IV), and carbon-based radicals.

Abstract: Reaction of potassium dichromate with sodium ascorbate was studied by EPR spectroscopy at room temperature, in 0.10 M N-[2-hydroxyethyl]piperazine-N'-[2-ethanesulfonic acid] (HEPES), phosphate, cacodylate, and tris(hydroxymethyl)aminomethane hydrochloride (Tris.HCl) buffers at pH 7.0, in the presence of 0.10 M spin trap [5,5-dimethyl-1-pyrroline 1-oxide or 2-methyl-N-(4-pyridinylmethylene)-2-propanamine N,N'-dioxide]. Chromium(V), ascorbate radical, CO2-, and other carbon-based spin trap-radical adducts were observed. Chromium(V), CO2-, and the carbon-based radicals were observed at low ratios of ascorbate to chromium, and ascorbate radical was observed at high ratios of ascorbate to chromium. The presence of Cr(IV) was detected indirectly by reaction with Mn(II) and a subsequent decrease in the Mn(II) EPR signal. More Cr(IV) was found for the higher reaction ratios of ascorbate to Cr(VI). The only buffer effect observed was a relative decrease of the Cr(V) signal in Tris.HCl vs HEPES, phosphate, and cacodylate buffers, no change in the radical adducts was observed. There was no evidence for reactive oxygen species an intermediates in this reaction. Addition of the singlet oxygen trap 2,2,6,6-tetramethyl-4-piperidone hydrochloride showed no 2,2,6,6-tetramethyl-1-piperidinyloxy radical formation. The Cr(V) species did not react with dioxygen, and dioxygen did not affect the formation of carbon-based radicals. A mechanism consistent with these observations is discussed.

In vivo effects of chromium.

Abstract: The production of reactive oxygen species on addition of hexavalent chromium (potassium dichromate, K2Cr2O7) to lung cells in culture was studied using flow cytometer analysis. A Coulter Epics Profile II flow cytometer was used to detect the formation of reactive oxygen species after K2Cr2O7 was added to A549 cells grown to confluence. The cells were loaded with the dye, 2',7'-dichlorofluorescein diacetate, after which cellular esterases removed the acetate groups and the dye was trapped intracellularly. Reactive oxygen species oxidized the dye, with resultant fluorescence. Increased doses of Cr(VI) caused increasing fluorescence (10-fold higher than background at 200 microM). Addition of Cr(III) compounds, as the picolinate or chloride, caused no increased fluorescence. Electron paramagnetic resonance (EPR) spectroscopic studies indicated that three (as yet unidentified) spectral "signals" of the free radical type were formed on addition of 20, 50, 100, and 200 microM Cr(VI) to the A549 cells in suspension. Two other EPR "signals" with the characteristics of Cr(V) entities were seen at field values lower than the standard free radical value. Liver microsomes from male Sprague-Dawley rats treated intraperitoneally with K2Cr2O7 (130 mumole/kg every 48 hr for six treatments) had decreased activity of cytochromes P4503A1 and/or 3A2, and 2C11. Hepatic microsomes from treated female Sprague-Dawley rats, in contrast, had increased activities of these isozymes. Lung microsomes from male Sprague-Dawley rats had increased activity of P4502C11.

Chromate-allergic patients challenged orally with potassium dichromate.

Abstract: 30 patients who had positive patch tests to potassium dichromate participated in a placebo-controlled oral challenge with 2.5 mg chromium given as potassium dichromate. 17 reacted to chromate but not to the placebo, 2 reacted to both chromate and the placebo, and 4 reacted to the placebo but not chromate. 7 patients had no reaction. A specific reaction to chromate was most common among patients with dermatitis of the hands and/or feet.

Reduction of nickel sulfide stones in a glass melting operation

Abstract: Material selected from the group consisting essentially of molybdenum, arsenic, antimony, bismuth, copper, silver, potassium dichromate and iron chromite, is added during the manufacture of soda-lime-silica float glass to reduce the occurrences of nickel sulfide stone defects. Material is added in sufficient amounts such that the resulting glass is at least 0.010 wt. % selected material. In a preferred embodiment of the invention, molybdenum is added in the form of sodium molybdate such that the resulting glass is at least 0.015 wt. % molybdenum.

Protective Effects of Thiol Compounds on Chromate-induced Toxicity In Vitro and In Vivo

Abstract: The effects of thiol compounds (L-cysteine ethyl ester, 2,3-dimercaptosuccinic acid, or 2,3-dimercapto-1-propanesulfonic acid) on the toxicity induced by chromate (potassium dichromate) were investigated in HeLa cells and mice. Chromate-induced cytotoxicity evaluated by inhibition of cell growth and chromium content of the cells was diminished by all of the thiol compounds tested when the cells were incubated in the medium with both chromate and one of the thiol compounds. In mice injected ip with a thiol compound immediately after injection of chromate, mortality, ornithine carbamyl transferase activity in the serum, and chromium content in the liver were diminished remarkably compared with mice injected with chromate alone. These thiol compounds also caused an increase of urinary chromium excretion. These results suggest that the thiol compounds tested are useful for treating chromate-induced toxicity when they are given immediately after intake of the metal.

Test for glycol in water

Abstract: Disclosed is a method of determining the presence of glycol in an aqueous solution comprising providing a container containing a mixture of potassium dichromate, a catalyst comprised of mercuric sulfate and silver sulfate, the mixture provided in an acidic solution. To the container is added a controlled volume of aqueous solution containing glycol. The mixture is permitted a time sufficient to change color, the time not being in excess of 15 minutes. The color is compared to a set of color standards to determine the presence of glycol in said aqueous solution.

Passivate for tungsten alloy electro-plating

Abstract: PROBLEM TO BE SOLVED: To improve corrosion and deterioration resistances by bringing a tungsten alloy electroplate into contact with a specified amount of CrO 3 in an aq. soln. in a bath having a specified pH to passivate the tungsten alloy electroplate. SOLUTION: A tungsten alloy electroplate is brought into contact with CrO 3 in an amount effective for passivation such as about 1.8 - about 45 g/liter in a bath having a definite parameter, pH of about 3.5 - about 8. At this time, a bath temp is preferably about 38 - about 82°C. As an origin of CrO 3 , there may be cited chromic acid, potassium dichromate, sodium dichromate, sodium chromate, potassium chromate and their mixtures. Control of pH in the bath can be carried out by adding a hydroxyl ion origin, sodium hydroxide, ammonium hydroxide, carbonate and their mixtures. COPYRIGHT: (C)1996,JPO

Hgcdte crystal appreciation etchant

Abstract: PURPOSE:To propose etchant for appreciation of mercury/cadmium/tellumium crystal which enables accurate discrimination of a pit with less surface roughening by one etching treatment without performing a post-treatment. CONSTITUTION:This etchant has a composition consisting of potassium dichromate of 4.1 to 5.6wt%, nitric acid of 15.2 to 21wt%, hydrochloric acid of 5.7 to 7.9wt%, acetic acid of 13.3 to 32.4wt.% and water of the remainder.

Potassium dichromate dosimeter

Abstract: The dosimetry of potassium dichromate dosimeter is investigatedThe linear molar ab-sorbance coefficient at 440 nm of potassium dichromate solution is determined being 4652m￣2/moland the temperature coefficient of the dosimeter during irradiation is-022%/℃, The measuredG value,dose-absorbance conversion factor are 3 91 ×10￣(-8)mol /J and 574 ×10￣4 Gy,respectively,The total unceriainty estimated as 4% (95% confidence)