A Simple Colorimeter for Measuring the Concentration of Multicomponent Food Coloring

Abstract

Built-in instruments are commonly employed in physics experiments. In this case, students are usually unaware of the instrument’s fundamental physics. Here we constructed a simple and compact colorimeter. A light-emitting diode (LED) was used as a light source. The light detector circuit consists of a photoresistor, a resistor, and a 9-V battery. During the experiment, we illuminated the solution of food coloring. The transmitted light was measured via the voltage in the resistor of the light detector to obtain the absorbance. The value was then used to determine the concentration of the solution. This instrument has been used to measure a mixture of food coloring’s concentration e.g. 1 ml/l Carmoisine and 1 ml/l Ponceau. For this sample, the measurement gave a concentration of 0.97 ml/l Carmoisine and 0.81 ml/l Ponceau. This instrument is simple and appropriate for teaching.