Sodium dichromate

About: Sodium dichromate is a research topic. Over the lifetime, 421 publications have been published within this topic receiving 6202 citations. The topic is also known as: Disodium salt & sodium bichromate.

Gelation behavior as a function of concentration of sodium thiosulfate for PAM gels cross-linked with chromium

Abstract: Existing reducing agents for cross-linking polymers are expensive and toxic and mostly limited for water shut off applications. A gelation study was performed on a safer, cheaper, more soluble, and short-lived gel by cross-linking polyacrylamide and chromium as a cross-linking agent using a rheometer and bead-pack porous media. The effect of concentration of sodium thiosulfate as the reducing agent was investigated to determine conditions for optimum yield strength and the gelation time and behavior which has never been published before. For a fixed minimum concentration (for the gel to form) of polyacrylamide and sodium dichromate, the gel yield strength vs. sodium thiosulfate concentration showed a somewhat bell-shaped curve initially increasing, reaching a peak at 2000 ppm, and then starting to decrease. The gelation formed by sodium thiosulfate was comparatively weak and short lived as compared to the ones formed by other reducing agents. Gel started to form instantaneously, reached a peak in 2 h, began to decrease, and then stabilized at 40 cp. The mobility reduction trends were similar to the yield strength curve. The short-lived gel could be useful to improve the waterflood mobility ratio far away from the wellbore without compromising on ease of injectivity.

Metabolic activation and deactivation of mutagens and carcinogens.

Abstract: The activity of some mutagens has been investigated in the Salmonella test either in the absence or in the presence of fortified rat liver microsomal fractions, together with an NADPH-generating system. With respect to their metabolic reactivity, the compounds tested could be distinguished according to four reproducible trends: (a) conversion of inert compounds into mutagenic metabolites (e.g. 2-aminofluorene and benzo(a)pyrene); (b) further enhancement of mutagenicity (e.g. 1,2-epoxybutane); (c) no effect on mutagenicity (e.g. glycidol, folpet, nitrofurantoin and 2-nitronaphtalene); (d) slight decrease (e.g. 1,1,1-trichlor 2,3-propenoxide), marked decrease (e.g. sodium nitrite, 5-nitro-2-furoic acid and captan) or even complete reversal of mutagenicity (e.g. styrene oxide, sodium azide, sodium dichromate and other Cr6+ compounds). The Salmonella/microsome test was effective in discriminating not only the mutagenic activity but also the metabolic reactivity of structurally related chemicals (e.g. the fungicides captan and folpet). In some cases, mutagens were tested also in the presence of other biological preparations (e.g. rat muscle or lung microsomal preparations, human gastric juice, serum, plasma or erythrocyte lysates). The mutagenic and metabolic properties of largely used products (e.g. an antibacterial drug containing nitrofurantoin and laboratory reagents containing sodium azide) have been also checked. The mechanisms underlying the metabolic behaviour of some of the mutagens tested have been reported. The results obtained have been correlated with the literature data on their carcinogenicity. Although these in vitro findings are only indicative of the possible metabolic fate of mutagens in the whole organism, the observed effects may be useful in order to explain the epidemiological data and the results of animal tests, and to assess the possible health hazards of mutagens.

Method for producing sodium fluosilicate by utilizing waste water containing sodium sulfate

Abstract: The invention discloses a method for producing sodium fluosilicate by utilizing waste water containing sodium sulfate. The method is as follows: generating the sodium fluosilicate by adopting the waste water containing sodium sulfate and fluosilicic acid as a side product for producing hydrofluoric acid as a raw material; and obtaining a sodium fluosilicate product by curing, filtering, cleaning and pneumatic drying. The dilute sulphuric acid as a side product is used for a production line of sodium dichromate. The method provided by the invention has the advantages that the industrial sodiumsulfate waste water is utilized to produce the sodium fluosilicate, and the materials are all industrial waste water. The industrial waste water of the sodium sulfate is from waste water obtained by washing chromium sesquioxide produced by sodium dichromate or waste water generated for producing chromium salt, the fluosilicic acid is from waste water in the process for producing the hydrofluoric acid, the produced sodium fluosilicate is used as a commodity for sales, the dilute sulphuric acid as a side product is used for the production line of the sodium dichromate. By utilizing the method, the cost for treating the waste water treatment of the industrial sodium sulfate in the chromium salt industry is reduced, and the reutilization of water resources is realized.

Understanding Selectivity in the Chlorate Process: A Step towards Efficient Hydrogen Production

Abstract: Chlorate production is a highly energy demanding industrial process, where chlorate formation is accompanied with hydrogen formation on the cathode. To ensure a high cathodic current efficiency, sodium dichromate is added to the chlorate electrolyte to avoid reduction of hypochlorite formed as a reaction intermediate in the process. However, chromate is highly toxic to humans and environment, and therefore a replacement is desired. A model system with ex situ formed chromium oxide/hydroxide films were used to study hypochlorite reduction and hydrogen evolution. The experimental results demonstrate that the hypochlorite reduction is fully blocked while hydrogen evolution readily occurs. However, in the presence of hypochlorite the hydrogen evolution reaction is inhibited. By combining experimental findings with density functional theory (DFT) calculations, the mechanism of hypochlorite reduction was revealed and the reason for inhibition by the deposited chromium(III) film was demonstrated. Based on these results possible replacements for chromate are suggested.

Ultraviolet light absorbing glass

Abstract: 925,507. Coloured glass compositions. OWENS-ILLINOIS GLASS CO. Nov. 18, 1960, No. 39624/60. Class 56. An ultra-violet light absorbing green glass which gives good transmission of visible light comprises a soda-lime silica glass to which is added chromium oxide present in the glass in both the tri-valent and hexavelent state. The preferred composition is 60-75% (by weight) silica, 0.1-9.5% Al2O3, 6-12% CaO, 0-6% MgO, 0-1% BaO, 0-5% B2O3, 10-21% alkali metal oxides, less than 0-3% Fe2O3 and less than 0.3% total chromium oxides, present as both trivalent chromium oxide Cr2O3, and hexavalent chromium oxide Cr2O3, the latter ranging from 0.005 to 0.070%. Cobalt oxide in an amount 0.002-0.005% and copper oxide about 0.07% may be added to control the colour. KNO3 or NaNO3 may be employed as oxidizing agents to ensure the prescribed amount of hexavalent chromium is present in the glass. The batch is melted under carefully controlled oxidizing conditions which may be produced by the introduction of oxygen into the melt by means of an oxygen bubbler. Potassium or sodium dichromate and other chromates or chromites may be used to introduce chromium into the batch. U.S.A. Specification 2,974,052 is referred to.