| Customization: | Available |
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| CAS No.: | 7789--------00-------6 |
| Formula: | Crk2o4 |
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It is an inorganic compound, yellow orthorhombic or hexagonal crystal at room temperature. The relative density is 2.732, the melting point is 968ºC, and it is toxic. Soluble in water, chromate ion hydrolysis solution is alkaline after dissolution, insoluble in alcohol and ether. Adding acid to a yellow solution turns the solution orange, which is the color of dichromate. The conversion between chromate and bichromate in solution has the following equilibrium: when adding acid to solution, the equilibrium moves in the direction of formation, and when adding alkali to solution, the equilibrium moves in the direction of formation. It is oxidizing, and in an alkaline medium it reacts with a reducing agent to reduce itself to tetrahydroxy chromium ion Cr(OH)-4(i.e., chromite ion co-2). Solutions containing barium ion, lead ion and silver ion were added to the it solution to produce the corresponding insoluble chromates: Barium chromate BaCrO4(yellow), lead chromate pbCrO4(yellow), silver chromate Ag2CrO4(brick red). The presence of chromate ions can be proved by the characteristic color of these insoluble chromates. it can be used as analytical reagent, oxidant, mordant, metal rust inhibitor, barium, silver trace analysis, can also be used in tannery, medicine and other raw materials for making other chromium compounds. Using chromite Fe(CrO2)2 powder as raw material, calcined and limestone (dolomite) in the air, and then extracted with potassium sulfate solution, it can be prepared. The above information is edited by Xiaonan of Chemicalbook. it indicator method uses it (K2CrO4) as an indicator and (AgNO3) as a standard solution precipitation titration method (silver measurement), also known as Mohr method (Mohr), mainly used for the determination of chloride ions (Cl-) or ions (Br-). A small amount of K2CrO4 was added as an indicator and titrated with AgNO3 standard solution. After titration begins, white (silver chloride) or light yellow (silver bromide) precipitation is first precipitated, when Cl- or Br- quantitative precipitation, excessive Chemicalbook very little solution will cause a sudden increase in the concentration of silver ions (Ag+) in the solution, and immediately generate brick red silver chromate (Ag2CrO4) precipitation, indicating the titration end point. The amount of indicator and the acidity of the solution are the two main problems of this titration method. The concentration of K2CrO4 is too high, resulting in the color of the titrated solution is too dark, and hinder the observation of the precipitation color of Ag2CrO4 at the end point; The concentration of K2CrO4 is too low, and after the quantitative precipitation of silver halide, a considerable amount of solution must be added to the precipitation of silver chromate to indicate the titration end point, thus increasing the titration error. When the halide of 0.1mol/1 is titrated with 0.1mol/1AgNO3 solution, when the concentration of K2CrO4 is 5×10-3mol/l, the end point error is only +0.06%, which can be considered that the accuracy of the analysis results is not affected. K2CrO4 indicator method can not be carried out in acidic or strongly alkaline solutions, because when the pH value is low, K2CrO4 transforms into (K2Cr2O7), when the pH is too high, Ag+ will be precipitated in the form of (Ag2O), the appropriate acidity range is pH=6.5 ~ 10.5, if there is ammonium salt in the solution, The pH of the solution is 6.5 ~ 7.2. it indicator method can only be used to directly titration Cl- or Br- ions, when the two coexist, titration is their total amount, this method is not suitable for the determination of iodine ion (I-) or thiocyanogen ion (SCN-), because they are easily adsorbed by precipitation and the end point is not clear. This method is also not suitable for Cl- titration of Ag+. To determine Ag+, backtitration can be used, that is, a certain amount of excessive NaCl standard solution is added to the test solution, and then excessive Cl- ions are titrated with AgNO3 standard solution. Any cations that can precipitate with CrO2-4 or anions that precipitate with Ag+ in the solution will interfere with the determination. The potassium chro-mate indicator method is mainly used for the determination of Cl- in very dilute solutions, such as the determination of Cl- in drinking water and Cl- in impurities in industrial products.
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