Showing papers on "Potassium dichromate published in 2010"
TL;DR: Removal of Cr(VI) ions from aqueous solution was investigated using modified palm shell activated carbon and the adsorption data were found to fit well with the Freundlich isotherm model.
184 citations
TL;DR: The study suggests that TRF is effective in preventing K( 2)Cr(2)O(7)-induced acute renal injury, but more studies are needed to confirm the effects of TRF as a nephroprotective agent.
53 citations
TL;DR: In this article, the performance of potassium dichromate and potassium chromate inhibitors on the corrosion of steel rebar in concrete partially immersed in sulfuric acid and sodium chloride medium was investigated.
Abstract: This study investigated the performance of potassium dichromate and potassium chromate inhibitors on the corrosion of steel rebar in concrete partially immersed in sulfuric acid and sodium chloride medium. The open circuit potential corrosion monitoring technique was employed for the acidic and marine simulating environments, and potential readings were taken in accordance with ASTM C 876. Inhibiting quality and uniformity of the inhibitors were then analyzed using an extreme value statistical modeling approach of the Weibull probability density distribution for determining the most efficient inhibitor. In the inhibitor concentrations used, the statistically analyzed experimental results identified 0.145 M potassium chromate as exhibiting the best inhibiting quality in sulfuric acid whereas the synergetic admixture of 0.032 M potassium dichromate and 0.097 M potassium chromate was predicted as showing the lowest probability of corrosion risk in sodium chloride solution. However, the overall probabilistic results rated potassium chromate as the best inhibitor compared to potassium dichromate in most of the other concentrations investigated in the study, especially in concrete structures exposed to saline environments.
37 citations
TL;DR: Contact allergy epidemics to chromate and nickel were addressed in Denmark in 1983 and 1990 by regulatory interventions and need to be addressed again.
Abstract: Background: Contact allergy epidemics to chromate and nickel were addressed in Denmark in 1983 and 1990 by regulatory interventions.
Objectives: To evaluate whether regulatory interventions on nickel and chromate exposure have reduced the proportion of strong patch test reactions.
Methods: 22 506 patients with dermatitis aged 4–99 years were patch tested with nickel sulfate, potassium dichromate, or cobalt chloride between 1977 and 2009.
Results: The proportion of 3+ reactions to nickel sulfate was reduced and almost disappeared after the mid- and late 1980s (P-trend = 0.001). Today, 1+ and 2+ nickel reactions occur equally frequent. Cobalt chloride patch test reactivity reflected the nickel development to some degree. The proportion of 3+ reactions to potassium dichromate was reduced during the 1980s (P-trend = 0.13), whereas the proportion of 2+ reactions to potassium dichromate have increased in recent years.
Conclusions: The decrease in nickel sulfate and cobalt chloride 3+ patch test reactivity began long before the Danish nickel regulation came into effect. This could be because of research activity at the time as well as political attention in Northern Europe. The chromate content in cement regulation may have changed the epidemiology of patch test reactivity; however, in recent years, 2+ reactions to chromate have increased markedly, a development that should be carefully followed.
33 citations
30 Apr 2010
TL;DR: In this article, short-term acute toxicity tests were performed over a period of 96 h providing the medium with various concentrations of potassium dichromate, and the 96 h LC50 value was found to be 91.51 mg l-1.
Abstract: Water pollution by heavy metals, especially chromium pollution from industrial sources can affect aquatic life, all ecosystems and human health directly or through food chain. This study aims to investigate the uptake of hexavalent chromium by a freshwater fish, (Tilapia, Oreochromis aureus). Short-term acute toxicity tests were performed over a period of 96 h providing the medium with various concentrations of potassium dichromate. Then the 96 h LC50 value was found to be 91.51 mg l-1 (Cr6+ as 32.35 mg l-1). Five different concentrations of Cr6+ varying between 10, 15, 20, 25 and 30 mg l-1were implemented for the uptake of this metal. The experiment was carried on for 28 days, meanwhile sampling fish weekly. With continued exposure, the accumulations were increased and fish progressively lost their ability to respond to this increase in exposure period. The chromium concentration in different organs was in the following order gill > skin > muscles tissues (least). The concentration of Cr in the gill range from 3.11 - 45.23 µg g-1 w.w, while the concentration accumulated in the muscle tissue of fish ranged from 0.86 to 12.34 µg g-1 w.w.
Key words: Heavy metal, Cr toxicity, fish, Tilapia (Oreochromis aureus), accumulation.
26 citations
TL;DR: The study indicates that the ascorbic acid may have the potential to protect thyroid gland from chromium toxicity; however, the study warrants further in-depth experimentation to precisely elucidate this role.
Abstract: Occupational exposure to toxic heavy metals may render industrial workers with thyroid-related problems. Here, we examined the role of ascorbic acid (vitamin C) against hexavalent chromium Cr (VI)-induced damage in rat thyroid gland. Potassium dichromate (K2Cr2O7) and ascorbic acid doses were 60 microg and 120 mg kg(-1) body wt (intraperitoneally [i.p.]) respectively. Treatment regimens were group I rats, saline treated control; group II, only K2Cr2O7; group III, ascorbic acid 1 hour prior K2Cr2O7; group IV, simultaneous doses of ascorbic acid and K2Cr2O7, and group V, a combined premix dose of ascorbic acid and K2 Cr2O7 (2:1 ratio). Blood samples were taken before dosing the animals and 48 hours post exposure to determine the serum thyroid-stimulating hormone (TSH), free triiodothyronine (FT3) and free thyroxine (FT4) concentrations. Toward end of experiment, rats were sacrificed and thyroid glands were processed to evaluate the extent of cellular insult. Results showed significantly increased TSH and decreased FT3 and FT4 concentrations in groups II, III and IV rats as compared to control levels (p < 0.05). In contrast, in group V rats, serum TSH, FT3 and FT4 concentrations neared control concentrations. Histopathologically, protective effect of ascorbic acid was found in group V rats only, where thyroid gland structure neared control thyroid except the follicular size that was decreased (p < 0.05). Follicular density was no different from control. Basal laminae were intact, interfollicular spaces were normal. Colloid retraction and/or reabsorption were reduced maximally. Epithelial cell height was no different from control; epithelial follicular index increased only 1.3 fold, whereas nuclear-cytoplasmic (N/C) ratio was decreased by 14% only. The study indicates that the ascorbic acid may have the potential to protect thyroid gland from chromium toxicity; however, the study warrants further in-depth experimentation to precisely elucidate this role.
25 citations
Journal Article•
TL;DR: It was observed that, the inoculation of Enterococcus casseliflavus reduced the BOD and COD values of tannery effluent, and the chromium adsorption was more significant by the live cells than killed cells at different time intervals.
Abstract: Bioadsorption, bioaccumulation and enzymatic reduction are the processes by which the microorganisms interact with the toxic metals, enabling their removal or recovery. In the present study, a bacterial strain was isolated from tannery effluent and identified as Enterococcus casseliflavus. It showed a high level resistance of 800 µg/ml chromium. The minimal inhibitory concentration of chromium was found to be 512 µg/ml of potassium dichromate in Nutrient broth medium. The chromium adsorption was more significant by the live cells than killed cells at different time intervals. It was observed that, the inoculation of Enterococcus casseliflavus reduced the BOD and COD values of tannery effluent. The maximum adsorption of chromium was at a temperature of 35oC to 45oC and at a pH of 7.0 to 7.5.
18 citations
TL;DR: Under the specified experimental conditions, maximum removal of the hexavalent chromium achieved was approximately 90% of its original value, and the time-concentration data followed a pseudo-first-order kinetic model.
Abstract: Hexavalent chromium, emanating primarily from the tannery and electroplating industries, can be reduced to the less toxic trivalent variety by several methods, including reduction with metallic iron. In the present work, electrolytic-grade iron dust was used to reduce chromium(VI) in the form of potassium dichromate. Loading of iron dust was varied from 0.5 to 1.0 g in 50 mL of solution; the pH of the medium was varied from 1.5 to 3.5; and the initial concentration of the dichromate solution was varied from 50 to 125 mg/L. Under the specified experimental conditions, maximum removal of the hexavalent chromium achieved was approximately 90% of its original value. The time-concentration data followed a pseudo-first-order kinetic model. The conversion and rate of reduction increased with an increase in iron loading and acidity of the medium, whereas an increase in the initial concentration of chromium(VI) caused a decrease in the reduction.
17 citations
TL;DR: The results show that alkaline graphite intercalation compounds were prepared when SO(4)(2-) and OH(-) ions were inserted into the spaces between the graphene planes, producing a flake morphology and multilevel structure.
12 citations
TL;DR: In this article, the toxic effect of TCE (trichloroethylene), PCE (tetrachloro methylene), and potassium dichromate (PCE) on P subcapitata was investigated.
Abstract: In this report, the toxic effect of TCE (trichloroethylene), PCE (tetrachloroethylene), and potassium dichromate on P subcapitata was investigated The test was conducted at different concentrations of pollutants, starting from the European Community limit values defined for each analysed contaminant Mixtures of pollutants were also tested to verify the combined effect of algae cells Results suggest that both TCE and PCE were able to reduce P subcapitata growth and metabolism starting from 005 and 002 mg L−1 of contaminant, respectively PCE seems to be substantially more toxic than TCE Chromium produces a clear effect on algae growth and esterase activity only starting from 1 mg L−1 of potassium dichromate; this result confirms the suitability of EU limit value AFLP analysis showed that all tested pollutants produce DNA mutations probably due to oxygen radicals Generally, chromium, at high concentrations, is more toxic and genotoxic that TCE or PCE Test performed with a mixture of pollutants showed a synergic effect of chromium and organic compounds suggesting that the membrane damage induced from organic substances should increase the chromium cellular access
10 citations
Patent•
23 Jun 2010
TL;DR: In this article, a method for measuring the chemical oxygen demand of waste water, which comprises the following steps: preparing standard solution of potassium dichromate, ferroin indicator solution and ammonium ferrous sulfate, solution of sulfuric acid-silver sulfate and mercuric sulfate.
Abstract: The invention discloses a method for measuring the chemical oxygen demand of waste water, which comprises the following steps: preparing standard solution of potassium dichromate, ferroin indicator solution, standard solution of ammonium ferrous sulfate, solution of sulfuric acid-silver sulfate and mercuric sulfate; diluting the mercuric sulfate in a water sample, adding the standard solution of potassium dichromate and a plurality of cleaned glass balls in a certain proportion; adding the solution of sulfuric acid-silver sulfate; heating the solution into an autoclave; after keeping the solution at a certain temperature and under a certain pressure for a period of time, adding water to continuously cool to room temperature; adding the ferroin indicator solution, performing titration through the standard solution of ammonium ferrous sulfate; recording the dosage of the standard solution of ammonium ferrous sulfate according to color changes; performing a blank experiment through distilled water according to the same operating steps; and recording the dosage of the standard solution of ammonium ferrous sulfate in blank titration. The method has the advantages of time conservation, and simple requirements on test conditions.
TL;DR: It was shown that guanine seems to be more readily oxidized by the potassium dichromate than adenine, and it is believed that this is the first report of a simple differential pulse voltammetric genotoxicity assay utilizing dsDNA in free solution.
Abstract: The aim of the current work was to characterize the electrochemical behavior of DNA and its derivatives using screen printed carbon electrodes (SPCEs). Differential pulse voltammetry (DPV) was carried out on guanine, adenine, 8-oxyguanine, 8-deoxygaunosine, deoxyguanosine, deoxyadenosine, adenosine-mono-phosphate, and adenosine-tri-phosphate solutions. Each species gave well defined oxidation peaks and the peak potential was characteristic of the DNA derivative. The effect of different concentrations of potassium dichromate on dsDNA was examined by DPV; three oxidation peaks were obtained which coincided with the peak potentials observed for 8-oxyguanine, guanine and adenine. This suggests that Cr6+ is likely to initially cause DNA damage by inducing double strand breaks that is followed by the breakage of the glycosidic bond between the purine and deoxyribose as well as chemical oxidation of guanine and adenine. It was shown that guanine seems to be more readily oxidized by the potassium dichromate than ...
Journal Article•
TL;DR: In this article, the role of hydroxyl radicals (•OH) on the formation of Cr 6+ in leather was assessed and the effect of adding an •OH scavenger (benzoic acid) was also studied.
Abstract: This study assesses the role of hydroxyl radicals (•OH) on the formation of Cr 6+ in leather. To avoid the complexity of composition of chemicals produced in leather fatliquors, •OH produced from the oxidation of lipids in leather fatliquors was replaced by •OH produced by a Fenton reagent. At room temperature, Fenton reagent was reacted with solutions of CrCl 3 , CrCl 3 - benzoic acid, chrome tanning agent and chrome tanning agent-benzoic acid, respectively. The amount of Cr 6+ in each solution was measured at different time intervals. The effect of •OH on the amounts of Cr 6+ was explored and the effect of adding an •OH scavenger(benzoic acid) on inhibiting the formation of Cr 6+ was also studied. Using ultraviolet spectrometry, the molecular structure of benzoic acid was analysed both before and after oxidation by Fenton reagent or potassium dichromate. The oxidization of Cr 3+ by Fenton reagent was initially explored. The results showed that the •OH group can oxidize Cr 3+ to Cr 6+ in both systems of CrCl 3 and chrome tanning agent and the •OH scavenger can inhibit the production of Cr 6+ . When the amount of benzoic acid was 3wt.% of the chrome the Cr 6+ concentration was decreased by 99.3% in 90 minutes.
Patent•
24 Nov 2010
TL;DR: In this article, a microwave puffing method was used to extract expanded graphite from a nitration mixture, and the product was put in an oven to dry at 60 DEG C after the product is pumped and filtered to obtain directly intercalated expanded graphites.
Abstract: The invention discloses a method for preparing expanded graphite by adopting a microwave puffing method. Potassium dichromate is dissolved in a nitration mixture solution, wherein the weight ratio of the potassium dichromate to concentrated nitric acid to concentrated sulfuric acid is 1:23.3:46; under the continuously stirring condition, 95-mesh nature flake graphite containing 99 percent of carbon is added into the solution, and reacts for 31 minutes at room temperature after even stirring, wherein the weight ratio of the potassium dichromate to flake graphite is 1 to 8.3; and the product is washed with distilled water until pH of the product is 7, and the product is put in an oven to dry at 60 DEG C after the product is pumped and filtered to obtain directly intercalated expanded graphite; and heating the directly intercalated expanded graphite in a microwave oven, and taking out the directly intercalated expanded graphite. The method for preparing the expanded graphite is convenient, energy-saving and efficient, has the advantages of mild reacting conditions and easy chemical production, and can easily regulate and control the whole production process and results by regulating and controlling the microwave power and heating time.
Patent•
22 Sep 2010
TL;DR: In this article, the authors proposed a solution for fast determining chemical oxygen demand, which consists of three prepared solutions: a solution as a catalyst prepared by dissolving 2.00-2.15g of silver sulfate in 500ml of sulfuric acid.
Abstract: The invention provides a digestion solution formula for fast determining chemical oxygen demand, relating to the field of digestion solution formulas of chemical oxygen demand after dissolved substances and suspended substances in a water sample are treated by potassium dichromate oxidation treatment. The digestion solution formula for fast determining chemical oxygen demand comprises the following three prepared solutions: a solution as a catalyst prepared by dissolving 2.00-2.15g of silver sulfate in 500ml of sulfuric acid, a solution as an oxidant prepared by dissolving 2.45g of potassium dichromate dried to constant weight in 100ml of water and 400ml of the sulfuric acid and a solution as a cocatalyst prepared by dissolving 0.80-15.15g of aluminum potassium sulfate, 0.48g of ammonium tetramolybdate and 2.25-5.15g of citric acid in 500ml of concentrated sulfuric acid. The digestion solution formula has the advantages of short reaction time, stable reaction and less silver sulfate dosage.
10 Mar 2010
TL;DR: In this paper, the authors investigated the possible protective effects of quercetin on hexavalent chromium in form of potassium dichromate induced chromosome aberrations in bone marrow and histopathological changes of spleen at the light microscopic level.
Abstract: Quercetin, in some fruits and vegetables, is a potent oxygen free radical scavenger and a metal chelator. This study was planned to investigate the possible protective effects of quercetin on hexavalent chromium in form of potassium dichromate (K ₂ Cr ₂ O ₇ ) induced chromosome aberrations in bone marrow and histopathological changes of spleen at the light microscopic level. Male Wistar rats were administered hexavalent chromium at doses of 5, 10 and 20 mg/kg BW and quercetin at dose of 100 mg/kg BW before administration of hexavalent chromium 20 mg/kg BW for one hour. All rats were treated by single gavage and killed 24 hours after each treatment. The results demonstrated that the histology of spleen was not changed in all groups of treatment. However, a significant increase in percentage of chromosome aberrations was observed in hexavalent chromium at doses of 5, 10 and 20 mg/kg BW as compared to the control group (p < 0.01 and p < 0.001). The increase of chromosome aberrations was dose-dependent manner of hexavalent chromium. Interestingly, the percentage of chromosome aberrations induced by hexavalent chromium 20 mg/kg BW could be reduced significantly (p < 0.001) by quercetin pretreatment. These results indicated that the antioxidant quercetin might have a protective effect against hexavalent chromium induced chromosome aberrations in rat bone marrow. This study suggested that quercetin might involve at least in part neutralizing free radicals.
Journal Article•
TL;DR: In this paper, a determination method of iron(Ⅱ) in direct reduced iron was developed by iron trichloride decomposition-potassium dichromate titration.
Abstract: A determination method of iron(Ⅱ) in direct reduced iron was developed by iron trichloride decomposition-potassium dichromate titration.The sample was dissolved in irom trichloride solution.The metallic iron in sample was oxidized to ferrous chloride before entering into solution,while the iron(Ⅱ) remained in the sediment,which then was filtered and separated.In vacuum,the sediment was dissolved by hydrochloric acid and potassium fluoride.The solution was titrated with potassium dichromate standard solution with sodium diphenylamine sulfonate as indicator.The effects of concentration and dosage of reagent,time,titration medium and interference elements were investigated.The optimal experimental conditions were obtained: the concentration and dosage of iron trichloride were 100 g/L and 30 mL,and the stirring time was 20 min.This method was applied to the determination of iron(Ⅱ) in direct reduced iron,with the relative standard deviations(RSD) of less than 2 % and the recoveries in the range of 98 %-101 %.
Journal Article•
TL;DR: The mean daily water intake decreasing with the increase of the number of generations exposed, the lowest being found in the case of F2 generation, followed by F1 generation and F0, the differences being insignificant.
Abstract: Material and methods: The study was carried out on three generations of female rats, each generation comprising 28 white Wistar adult female rats, divided in three experimental (E) groups, exposed to 25 ppm Cr – LOAEL (E1), 50 ppm Cr (E2), 75 ppm Cr (E3) and one control (C) group tap water. Results: It pointed out significant decrease of water daily mean consumption in experimental groups comparative to C group, inversely, significantly correlated with the exposure level, in F0, F1 and F2 generations, the mean daily water intake decreasing with the increase of the number of generations exposed, the lowest being found in the case of F2 generation, followed by F1 generation and F0, the differences being insignificant. Also hexavalent chromium intake was calculated, F2 generation having the poorest appetite for water, received the smallest amount of toxic, but yet not undermining the gravity of exposure in F2 generation, due to parental exposure factors.
31 May 2010
TL;DR: The study revealed the presence of congestive and degenerative lesions in genital organs and sexual accessory glands of exposed individuals from F 0 and F 1 generation such as: interstitial edema, epithelial necrosis and atrophy, membrane exfoliation and necrosis.
Abstract: The aim of this study was the evaluation of Cr VI cumulative and differentiate exposure on integrity biomarker of male reproductive system. The objective was evaluation of potassium dichromate intake on genital organs and sexual accessory glands architecture in male rats from two generation. Males and females from F 0 generation were exposed to potassium dichromate three months before mating. F 1 generation was represented by male pups, resulted from F 0 generation, exposed to potassium dichromate in utero , during suckling (via milk and water) period and until sexual maturity. All the animals were divided in one control and three experimental groups, exposed to Cr VI trough drinking water, as followed E 1 : 25 ppm (LOAEL); E 2 : 50 ppm: E 3 : 75 ppm; control group received tap water without chromium content. The experiment was carried out with respecting legislation regarding ethics in animal experiments. The study revealed the presence of congestive and degenerative lesions in genital organs and sexual accessory glands of exposed individuals from F 0 and F 1 generation such as: interstitial edema, epithelial necrosis and atrophy, membrane exfoliation and necrosis. The lesions frequency and intensity were directly correlated to exposure level, the most affected being E 3 group and generation, more pronounced in F 1 generation.
TL;DR: In this article, a flow injection system incorporating electromagnetic induction heating oxidation for on-line determination of chemical oxygen demand (COD) was proposed, with acidic potassium dichromate acting both as an oxidant and as a spectrometric reagent.
Abstract: A flow injection system incorporating electromagnetic induction heating oxidation for on-line determination of chemical oxygen demand (COD) was proposed. The procedure utilised electromagnetic induction heating instead of conventional reflux heating, with acidic potassium dichromate acting both as an oxidant and as a spectrometric reagent. The elevated temperature and pressure inside the reaction coil contributed to the improvement of on-line sample oxidation, and hence, sample oxidation time was reduced to ca. 8 min (as compared to 2 h required for conventional method). The sampling frequency was 10 h−1, along with a quantification limit of 4.0 mg L−1 COD and a linear range of 4–200 mg L−1 COD (potassium hydrogen phthalate, r = 0.9958). Relative standard deviation was evaluated to be 3.5% at 100 mg L−1 COD and the results were comparable to those obtained by the standard method.
31 May 2010
TL;DR: The chromium toxicity impact on erythrocyte membrane was shown by the progressive decrease of osmotic resistance even from the first generation and by the increase of the haemolysis degree in hypotonic solutions.
Abstract: The aim of the experiment was to highlight the toxicity of the CrVI, administered during three generations, on the haemoglobin and on the osmotic resistance of the erythrocyte membrane in female rats. The determinations have been carried out on rat blood collected from female rats that reached sexual maturity, from F 0 , F 1 , F 2 generation, exposed to LOAEL, of CrVI, as potassium dichromate, in drinking water (3 months). F 1 and F 2 were obtained from female rats from generation F 0 and respectively F 1 exposed for 3 months to chromium dose, mated with male rats exposed to the same dose for three months, before mating. The results of the experiment indicated a high significant decrease of haemoglobin, (p<0,01) under to the control lot and under physiologic limits, in the three generations. The decrease of hemoglobin, registered also high significant differences (p<0,01) as well between generation F 0 and respectively generation F 1 and F 2 . The chromium toxicity impact on erythrocyte membrane was shown by the progressive decrease of osmotic resistance even from the first generation and by the increase of the haemolysis degree in hypotonic solutions. The exposure to LOAEL CrVI during three generations produces toxic effects on erythrocytes inducing hemolytic effect.
TL;DR: In this article, a potentiometric Ultramicrotitration of ammoniacal ferrous sulfate with three different oxidants (potassium dichromate, potassium permanganate and ceric sulfate) was compared to the conventional potentimetric titration of the above reagent.
31 May 2010
TL;DR: In male rats, from F 0 and F 1 generation, exposure to Cr VI determined: significant decrease of testosterone and significant increase of LH seric level in all experimental groups comparative to control one, indirectly, respectively, directly correlated to exposure level.
Abstract: The aim of this study was the evaluation of potassium dichromate impact on biochemical biomarkers for testicular function (serum testosterone and LH level) (two generations experiment). Males and females from F 0 generation were exposed to potassium dichromate three months before mating. F 1 generation was represented by male pups, resulted from F 0 generation, exposed to potassium dichromate in utero , in suckling period (via milk and water) and until sexual maturity. All the animals were divided in four groups: three experimental and one control, exposed to Cr VI trough drinking water, as follows E 1 : 25 ppm (LOAEL); E 2 : 50 ppm: E 3 : 75 ppm; control group received tap water without chromium content. The study was performed in compliance with national and international law regarding animal welfare and ethics in animal experiments. In male rats, from F 0 and F 1 generation, exposure to Cr VI determined: significant decrease of testosterone and significant increase of LH seric level in all experimental groups comparative to control one, indirectly, respectively, directly correlated to exposure level. Comparative to F 0 generation, in F 1 generation seric testosterone level was lower, significantly only in E 1 and E 3 groups, and LH seric level was significantly higher.
Journal Article•
01 Jan 2010-Scientific Works - University of Agronomical Sciences and Veterinary Medicine, Bucharest. Series C, Veterinary Medicine
TL;DR: In this article, an efficient procedure for the oxidation of benzoins to corresponding benzils using potassium dichromate under viscous conditions at room temperature is described, which can overcome the problems existed in the common solvent-free reactions of the difficulty for the solid molecular collision to react.
Abstract: An efficient procedure for oxidation of benzoins to corresponding benzils using potassium dichromate under viscous conditions at room temperature is described. The procedure can overcome the problems existed in the common solvent-free reactions of the difficulty for the solid molecular collision to react. The present oxidations are completed within 3 hours with the yield between 86–97%.
01 Jan 2010
TL;DR: In this article, the authors studied the chromic chromic oxidation of voachalotine and showed that the reaction proceeds in two steps, in the first step it is transformed into VOACHALITTE N-oxide and in the second stage it is further oxidized to VOACHalITTE oxindole.
Abstract: The study of the chromic oxidation of voachalotine (I) shows that the reaction proceeds in two steps. In the first step, (I) is transformed into dehydrovoachalotine (2), voachalotine oxindole (3) and 6-oxovoachalotine (5). In the second step which occurs in the presence of acetic acid, (2) is further oxidized to dehydrovoachalotine pseudoindoxyl (7), dehydropolyneuridine pseudoindoxyl (6) and dehydrovoachalotine oxindole (8). The structure of each of these compounds is discussed and a scheme for their formation is proposed.
The oxidation of voachalotine N-oxide without added acetic acid gives the same reaction mixture containing (2), (3) and (5).
Finally the oxidation of dehydroxymethylvoachalotine (12) in dilute acetic acid gives 6-oxodehydroxymethylvoachalotine (13). dehydroxymethylpolyneuridine oxindole (14) and dehydroxymethylvoachalotine oxindole (15). No pseudoindoxyl derivatives could be detected in this case.
01 Jan 2010
TL;DR: The study carried out on 28 white Wistar adult female rats, exposed for 6 months to tap water, pointed out significant decrease of total protein seric level below the bottom value of the physiologic limits, inversely correlated with the exposure level.
Abstract: The study carried out on 28 white Wistar adult female rats, divided in 3 experimental (E) groups, exposed for 6 months to 25ppmCr – LOAEL(E1), 50 ppm Cr (E2), 75 ppm Cr (E3) and one control (C) group tap water, pointed out: significant decrease of total protein seric level below the bottom value of the physiologic limits, inversely correlated with the exposure level; significant decrease of albumin and globulin seric level, inversely correlated with the exposure level; significant increase of urea and creatinine seric level (each exceeding the maximum physiological limit), directly correlated with the exposure level.
Patent•
08 Dec 2010
TL;DR: In this article, an all glass heat tube type vacuum solar heat collection pipe, which belongs to solar energy heat utilization technology field, is presented, which is safety, reliable, unease damage in installing and transportation process.
Abstract: Present invention relates to a all glass heat tube type vacuum solar heat collection pipe, belongs to solar energy heat utilization technology field. Said invention includes all glass vacuum solar heat collection pipe, opposite joint pipe, enclosed space heat transfer working medium. It features heat transfer working medium volume occupied enclosed space volume ratio greater than 0.03 per cent and less than 0.1 per cent, said heat transfer working medium being 0 to 30 per cent propylene glycol water solution or 0 to 20 per cent mineral acid, brine solution, said mineral acid, brine solution being potassium dichromate, potassium sulfate, sulfuric acid and phosphatic water solution, or potassium dichromate, potassium sulfate, ammonium sulfate and ammonium phosphate water solution, or potassium dichromate, potassium sulfate, sulfuric acid, phosphoric acid, ammonium sulfate and ammonium phosphate water solution, inner glass tube outer wall outer wall of said all glass solar heat collection tube having one or more than one support ring along axial direction. Said invention is safety, reliable, unease damage in installing and transportation process.
TL;DR: In this article, the phase field boundaries for individual salts and ammonium dichromate solid solutions, monovariant lines, and invariant points were determined for the first time.
Abstract: Solubility in the Na2Cr2O7-(NH4)2Cr2O7-K2Cr2O7-H2O four-component water-salt system at 25, 50, and 75°C was studied for the first time. Phase field boundaries for individual salts and potassium and ammonium dichromate solid solutions, monovariant lines, and invariant points were determined. Experimental data were used to optimize the looped isohydric process of potassium dichromate preparation involving additional salts.