COLORIMETER – PRINCIPLE, COMPONENTS, WORKING & APPLICATIONS

COLORIMETER – PRINCIPLE, COMPONENTS, WORKING & APPLICATIONS

PRINCIPLE OF COLORIMETER:

⇒ Colorimeter is based on the photometric technique which states that When a beam of incident light of intensity I₀ passes through a solution, a part of the incident light is reflected (I_r), a part is absorbed (I_a) and rest of the light is transmitted (I_t)

The mathematical relationship between the amount of light absorbed and the concentration of the substance can be shown by the two fundamental laws of photometry on which the colorimeter is based.

Beer’s Law

⇒ This law states that the amount of light absorbed is directly proportional to the concentration of the solute in the solution.

Lambert’s Law

⇒ The Lambert’s law states that the amount of light absorbed is directly proportional to the length and thickness of the solution under analysis.

PARTS OF COLORIMETER:

There are 5 essential parts in a calorimeter.

⇒ Light Source – The most common source of light used in colorimeter is a tungsten filament.

⇒ Monochromator – To select the particular wavelength filter or monochromators are used to split the light from light source.

⇒ Sample holder – Test tube or Cuvettes are used to hold the color solutions they are made up of Glass at the visible wavelength.

⇒ Photo Detector System – when light falls on the detector system, an electric current is generated, this reflects the Galvanometer reading.

⇒ Measuring device – The current from the detector is fed to the measuring device, the Galvanometer, shows the meter reading that is directly proportional to the intensity of light.

WORKING OF THE COLORIMETER:

⇒ When using a colorimeter, it requires being calibrated first which is done by using the standard solutions of the known concentration of the solute that has to be determined in the test solution.

⇒There is a ray of light with a certain wavelength that is specific for the assay is directed towards the solution. Before reaching the solution the ray of light passes through a series of different filters and lenses.

These lenses are used for navigation of the colored light in the colorimeter and the filter splits the beam of light into different wavelength and allows the required wavelength to pass through it and reaches the cuvette containing the standard or Test solutions.

It analyzes the reflected light and compares with a predetermined standard solution.

⇒ The galvanometer measures the electrical signals and displays it in the digital form. That digital representation of the electrical signals is the absorbance or optical density of the solution analyzed.

⇒ If the absorption of the solution is higher than there will be more light absorbed by the solution and if the absorption of the solution is low then more lights will be transmitted through the solution which affects the galvanometer reading and corresponds to the concentration of the solute in the solution.

APPLICATIONS OF THE COLORIMETER:

⇒ The colorimeter is commonly used for the determination of the concentration of a colored compound by measuring the optical density or its absorbance.

⇒ It can also be used for the determination of the course of the reaction by measuring the rate of formation and disappearance of the light absorbing compound in the range of the visible spectrum of light.

⇒ By colorimeter, a compound can be identified by determining the absorption spectrum in the visible region of the light spectrum.