Chemistry: Colorimetric Analysis
Chemistry: Colorimetric Analysis
Basics of Colorimetric Analysis
- Colorimetric analysis is a technique used in chemistry to determine the concentration of a substance by analysing its colour.
- The colour intensity of a solution can give clues about the amount of a particular substance it contains.
- This method depends on the Beer-Lambert Law, which states that the concentration of a solute is directly proportional to its absorbance.
How Does Colorimetric Analysis Work?
- In a colorimeter, light is passed through a sample and the light intensity is measured before and after passing through the sample.
- As the sample absorbs some of the light, the intensity of the light is reduced, and this can be compared to a calibration curve to determine the concentration of the sample.
- A colorimeter can measure both the wavelengths absorbed by the sample and the degree of absorption.
Using the Colorimeter
- To use a colorimeter, first choose a filter that matches the colour of the light that the solution absorbs.
- The device is then calibrated using a control solution known as a blank.
- After calibration, the unknown solution is analysed, and the colorimeter provides an absorbance value.
Preparing Calibration Curve
- Standard solutions with known concentrations are used to establish a calibration or standard curve.
- It’s a plot of absorbance versus concentration.
- The calibration curve is important for interpreting the results from the actual experiment with unknown concentrations.
Safety and Controls in Colorimetric Analysis
- Always wear appropriate safety gear, including gloves and safety goggles.
- Be aware of the specific hazards associated with the chemicals being handled and ensure they are stored and disposed of correctly.
- When establishing a control sample, it’s important to ensure that it’s treated in the same way as the test samples, but without adding the targeted substance.
Variables and Errors in Colorimetric Analysis
- Variables include temperature, volume of solution, and the wavelength of light used.
- Common errors come from inaccurate measurements, equipment calibration errors, and inconsistent experimental conditions, including light intensity and temperature.
- When analysing results, consider the possible impact of these variables and errors and include any observed anomalies in the documentation of the experiment.