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Inherent Safer Chemistry for Accident Prevention
Published in Aidé Sáenz-Galindo, Adali Oliva Castañeda-Facio, Raúl Rodríguez-Herrera, Green Chemistry and Applications, 2020
M. Andrade-Guel, C. Cabello-Alvarado, Carolina Caicedo, Leticia Melo, C. Ávila-Orta
Chromium (Cr VI): Chromium trioxide, Sodium chromate, Sodium dichromate, Potassium dichromate and Chromium compounds are used in the textile industry as mordants (to fix dye colors in fabrics), as well as in pigments manufacturing. They can cause respiratory disorders, skin ulceration and cancer in respiratory airways by inhalation (Sueker, 2006).
Oxidation Reactions
Published in Michael B. Smith, A Q&A Approach to Organic Chemistry, 2020
What is the structure for each of the following: chromic acid, sodium dichromate, potassium dichromate?
Characterization of the Cr(VI)/Cr(III) Ratio in Aerosols
Published in Jacques Buffle, Herman P. van Leeuwen, Environmental Particles, 2019
Rob F.M.J. Cleven, Jan L.M. deBoer, Anton van der Meulen
The use of chromium has increased dramatically in the 20th century. About 108 kg chromium were yearly emitted to the atmosphere in the 1970s from antropogenic sources.25 Emissions from primary production to the air diminished substantially during the last decade, as a result of improved production techniques and pollution control measures. For the production of chromium metal and chromium compounds, chromite (FeO·Cr2O3) is generally used. The main industrial compounds of chromium made directly from chrome ores are sodium chromate, sodium dichromate, potassium chromate and potassium dichromate, ammonium dichromate, and chromic acid, all Cr(VI) species.
Direct determination of a new mode-dependent cohesive zone model to simulate metal-to-metal adhesive joints
Published in The Journal of Adhesion, 2019
M. R. Gheibi, M. H. Shojaeefard, H. Saeidi Googarchin
Surface preparation of all adherends is done through Forest Products Laboratory (FPL) etching a mixture of sodium dichromate and sulfuric acid. This process is performed to maximize the degree of intimate molecular contact and attain the cohesive failure in the adhesive joint. After this crucial step, the resin and hardener of the adhesive with a weight ratio of 50/50 are mixed and applied on the adherends. In order to achieve the constant adhesive thickness along the bondline of the specimens, steel spacers are placed between adherends. It is noteworthy that to prevent a blunt crack in DCB and ENF specimens, the pre-crack, with a length of 1–2 mm, is induced by a 12 μm thick non-stick polyethylene film. The curing process according to the adhesive manufacturer catalogue takes place at room temperature for 24 hrs.
An overview of simultaneous saccharification and fermentation of starchy and lignocellulosic biomass for bio-ethanol production
Published in Biofuels, 2019
In the spectrophotometric analysis technique, sodium dichromate based colorimetric method is well known for ethanol estimation. The method is consist of five sequential stages: preparation of ethanol stock solution, preparation of sample solution, preparation of sodium dichromate reagent, preparation of acetate buffer (pH 4.3) and preparation of sulfuric acid. In this process, standard stock solution of 1.6 mg/mL, 5 mL of sodium dichromate solution, 5 mL of acetate buffer pH 4.3 and 25 mL of 1N sulfuric acid ware mixed all together in a 50 mL volumetric flask. The mixture was shaken gently for 1 min and allowed to incubate it at room temperature for 120 minutes. It leads to the formation of green color reaction product. After the incubation period, absorbances of the samples were measured at 578 nm to estimate ethanol concentration [81]. Another method is the specific gravity method. The method was related to the measurement of the specific gravity of the solution using a hydrometer. Specific gravity is the ratio of the density of the liquid to the density of water. Because the density of ethanol is less than that of water, the specific gravity of a solution will decrease as the amount of ethanol in that solution increases. These measurements allowed for a relative estimation of the amount of ethanol produced. However, the sugar content of a solution also affects the specific gravity as both sugar levels were decreasing with increasing level of ethanol concentration.
Chemical Industry, the Environment, and Russian Provincial Society: The Case of the Kokshan Chemical Works (1850–1925)
Published in Ambix, 2018
Andrei Vinogradov, Stanislav Petriashin
It was two years after Gay’s visit to the plant that Petr Ushkov hired Nikolai Walberg, as mentioned earlier, to introduce sodium dichromate production in addition to that of potassium dichromate. Walberg was probably the only chemical technologist in Kokshan who paid attention to the sanitary side of the production process. In his article in the “Industrial Bulletin” (Vestnik Promyshlennosti), Walberg pointed out that the preparation of chromium alkali is a production that is very harmful to the health of workers. Almost all of them after working a few months at the plant suffered perforation of the nasal septum. Moreover, if a small amount of the chrome salt solution falls on small ulcers, these ulcers, insignificant before, become so bad that sometimes we had to resort to operations.41