Chromium Trioxide

Chromium oxide physical property data

1. Traits: dark red or dark purple orthorhombic crystals, easy to deliquesce.

2. Melting point (°C): 190~197

3. Boiling point (°C): decomposition

4. Relative density (water = 1): 2.70

5. Solubility: soluble in water, sulfuric acid, nitric acid, ethanol, ether, acetic acid, acetone.

Chromium trioxide folding editing this paragraph storage method:

Storage Precautions: Store in a cool, dry, well-ventilated warehouse. The temperature of the reservoir does not exceed 30 ° C, and the relative humidity does not exceed 80%. The package must be sealed and not exposed to moisture. It should be stored separately from easy (combustible) fuel, reducing agent, active metal powder and food chemicals. The storage area should be provided with suitable materials to contain spills.

Chromium trioxide folding editing this paragraph synthesis method:

1. Sulfuric acid method The sodium dichromate is heated and melted with sulfuric acid to react, and after the reaction is finished, it is allowed to stand, and sodium hydrogen sulfate is separated, and then cooled, discharged, and packaged to obtain chromic anhydride. Its reaction formula is as follows:

2. The chrome ore is co-heated with soda ash and limestone, and then treated with concentrated sulfuric acid to obtain the product.

3. Sulfuric acid method, nitric acid method, fluorosilicic acid method and electrolysis method. The sulfuric acid process is mainly used in the industry. The anhydrous sodium dichromate and sulfuric acid are mixed in a reaction vessel, and then heated to 200 ° C to carry out a melting reaction to obtain a molten product of chromic anhydride and sodium hydrogen sulfate, which are allowed to stand for cooling and then cooled.

4. 100 g of dehydrated anhydrous sodium dichromate was dissolved in 250 mL of water and filtered, and 400 mL of concentrated sulfuric acid was slowly added to the transparent filtrate under stirring. Because it is very dangerous to add too much too quickly, you must pay attention to the rate of temperature rise when adding acid. When heated after the addition, the purple-red CrO3 began to precipitate. After standing for 24 hours, the precipitated crystals were filtered, washed repeatedly with concentrated nitric acid several times until there was no adsorbed sulfuric acid, and then dried.

5. Potassium dichromate can also be used instead of sodium dichromate. 10 g of potassium dichromate was dissolved in 100 mL of water, and 50 mL of 95% sulfuric acid was slowly added. At this time, heat was rapidly generated, and purple-red CrO3 was gradually precipitated. After standing for 24 h, most of the needle crystals were precipitated, filtered through a glass sand core funnel, washed several times with nitric acid to remove sulfuric acid, sufficiently dried, and placed in a glass bottle for storage.