Colorimeters

A colorimeter is a device that is used in Colorimetry. It refers to a device which helps specific solutions to absorb a particular wavelength of light. The colorimeter is usually used to measure the concentration of a known solute in a given solution with the help of the Beer-Lambert law. The colorimeter was invented in the year 1870 by Louis J Duboscq.

It is a photometric technique which states that when a beam of incident light of intensity Io passes through a solution, the following occur:

  • A part of it is reflected which is denoted as Ir
  • A part of it is absorbed which is denoted as Ia
  • Rest of the light is transmitted and is denoted as It

Therefore, Io = Ir + Ia + It

To determine Ia the measurement of Io and It is sufficient therefore, Ir is eliminated. The amount of light reflected is kept constant to measure Io and It.

Colorimeter is based on two fundamental laws of photometry. We have discussed them below: