Electrogravimetry

Electrogravimetry is an analytical technique used in chemistry for the quantitative determination of a specific substance by the process of electrodeposition on an electrode. This method is a type of electroanalytical method that relies on the measurement of mass change of an electrode as a function of the electrical current applied. The principle behind electrogravimetry is the controlled deposition of a metal (or any electroactive species) from its solution onto a pre-weighed electrode, followed by the weighing of the electrode after the deposition process. The difference in mass gives the amount of the substance deposited.

Principles of Electrogravimetry

Electrogravimetry operates on the principles of electrochemistry, specifically the laws of electrolysis as stated by Faraday's laws of electrolysis. According to these laws, the amount of substance deposited or dissolved at an electrode during electrolysis is directly proportional to the quantity of electricity (charge) passed through the electrolyte. The process involves the reduction of ions at the cathode to form a solid metal or the oxidation of ions at the anode.

Procedure

The typical procedure for an electrogravimetric analysis involves several steps:

1. A solution containing the analyte is prepared.
2. A pre-weighed electrode is immersed in the solution.
3. A constant current or potential is applied to induce the deposition of the analyte on the electrode.
4. After deposition, the electrode is removed, washed, dried, and re-weighed.
5. The increase in mass of the electrode corresponds to the mass of the analyte deposited.

Applications

Electrogravimetry is primarily used for the determination of metals in solution, especially heavy metals like copper, lead, and nickel. It is a highly accurate and sensitive method for the quantitative analysis of metals in various samples, including environmental, biological, and industrial materials.

Advantages and Limitations

The main advantages of electrogravimetry include high accuracy, specificity, and the ability to analyze small amounts of sample. However, the technique has limitations such as being time-consuming due to the slow deposition process and the requirement for a stable power supply to maintain constant current or potential.

Related Techniques

Electrogravimetry is closely related to other electroanalytical techniques such as voltammetry and coulometry, which also measure the relationship between the electrical properties and the concentration of analytes in a solution.