Chromic acid, a strong oxidizing agent that is utilized in various industries, comprises a chromium atom surrounded by four oxygen atoms. In its structure, two oxygen atoms each form single bonds with the chromium atom and a hydrogen atom individually, while the remaining two oxygen atoms create double bonds with the chromium atom.
Chromic acid is produced when chromium trioxide reacts with water. Chromium trioxide is crystalline, light red or brown in color, deliquescent, and fully soluble in water. Chromic acid is a very weak acid, and its salts can be dissociated even by acetic acid. It has a powerful oxidizing effect and is itself reduced to CrO3, which is why it should never be combined with alcohol or formalin. However, chromic acid is used in combination with formalin in some fixing fluids, where the reducing action is slow, allowing for the completion of fixation before the acid is fully reduced.
Technical Characteristics
| Chemical formula | H2CrO4 |
| CAS Number | 7738-94-5 |
| Other names | Chromic(VI) acid, Dihydroxidodioxidochromium, tetraoxochromic acid, Dichromic acid |
| Molecular Weight | 118.01 g/mole (chromic acid) |
| Appearance | Odorless dark purplish-red sand-like crystalline solid or powder |
| Density | 1.201 g/cm³ |
Applications
Chromic acid was once commonly used as a strong oxidizing agent for cleaning laboratory glassware, eliminating any stubborn organic residues that were otherwise difficult to remove. However, due to significant health concerns, its use has been prohibited in many institutions.
Other than that chromic acid finds applications in various industries and processes due to its unique properties.
Metal Finishing: Chromic acid is used in metal finishing processes where surfaces of objects are coated. It plays a crucial role in chromium plating.
Wood Preservation: Chromic acid is involved in wood preservatives to protect wood from bacteria and insects.
Plastic Production: Chromic acid plays a role in the production of plastic products.
Textile Industry: It is used as a mordant in the textile industry, facilitating the reaction between dyes and fabrics.
Musical Instrument Repair: Chromic acid was widely used in the musical instrument repair industry to brighten raw brass, leaving a bright yellow patina on the brass.
Photography: It is used as a bleach in black and white photographic reversal processing.
Other Applications: Chromic acid is also utilized in the oxidation of organic compounds in organic chemistry reactions, in laboratories, instrument repair, and in the metal industry.
Environmental impact and sustainability of Chromic acid
Chromic acid’s environmental impact and sustainability are major concerns due to its toxicity and carcinogenic properties. It has been extensively used in various applications, such as cleaning lab glassware, metal finishing, wood preservation, plastic production, ceramic glazes, and colored glass manufacturing. However, due to its dangerous nature, its use has been prohibited in many places, and eco-friendly alternatives have been developed.
Packing and Storage
Chromic acid is provided by a variety of distributors and manufacturers like Chemicals Global, Wego Chemical Group, and Vishnu Chemicals. These suppliers offer chromic acid in various forms and quantities, including chromium trioxide, a key component of chromic acid. Typically, the acid is delivered in steel drums equipped with locking rings, available in sizes ranging from 25 kg to 250 kg. Proper storage of chromic acid is advised in a cool, dry, and well-ventilated area, away from flammable materials.