Ferric nitrate solution is made by dissolving iron in a diluted nitric acid solution until a brown to reddish-purple color is achieved. More specifically, you need to use a nitric acid solution with a specific gravity of 1.3, diluted with water.
Here's a breakdown of the process:
-
Prepare the Diluted Nitric Acid Solution: Obtain nitric acid with a specific gravity of 1.3. Then, carefully dilute it with water. The exact dilution ratio will depend on the concentration of the starting nitric acid. Use appropriate personal protective equipment (PPE) such as gloves and eye protection, and work in a well-ventilated area when handling nitric acid. Always add acid to water, never water to acid, to avoid dangerous splattering.
-
Dissolve the Iron: Slowly add iron (e.g., iron filings or small pieces of iron) to the diluted nitric acid solution. The iron will react with the nitric acid, producing ferric nitrate and releasing nitrogen oxides. This reaction can be vigorous and produce heat, so add the iron gradually.
-
Monitor the Reaction: The solution will change color as the ferric nitrate forms. Continue adding iron until the solution develops a brown to reddish-purple hue.
-
Adjust the Solution (If Necessary): You may need to add more nitric acid or water to achieve the desired concentration and color. You can use a hydrometer to verify the specific gravity.
-
Filter the Solution (Optional): If there are any undissolved iron particles or other impurities, filter the solution.
Important Considerations:
- Safety: Nitric acid is a corrosive and dangerous substance. Always wear appropriate personal protective equipment (PPE), including gloves, eye protection, and a lab coat. Work in a well-ventilated area.
- Reaction Products: The reaction between iron and nitric acid produces nitrogen oxides, which are toxic gases. Ensure adequate ventilation to prevent inhalation of these gases.
- Concentration: The concentration of the ferric nitrate solution will depend on the amount of iron dissolved and the concentration of the nitric acid used.
- Alternative method: Sometimes ferric nitrate can be obtained through the reaction of iron(III) oxide (Fe2O3) with nitric acid. This reaction is slower than the reaction with metallic iron.
- Reference: JM Ordway et al is an example source for how ferric nitrate can be obtained.