Construction and Characterization of a Compact, Portable, Low-Cost Colorimeter for the Chemistry Lab

A low-cost and portable colorimeter was constructed featuring a low-voltage programmable color light sensor-to frequency converter, a CMOS 8-bit microcontroller, and an LCD display. The instrument has successfully facilitated the introduction and application of spectroscopy to groups of middle school, high school, and undergraduate students. A series of tried and tested laboratory experiments that demonstrate the utility and capabilities of the colorimeter have been developed. These laboratories not only help characterize the colorimeter but also feature challenging problems that allow students to realize the limitations of analytical instruments. The accompanying laboratories enable students to determine the concentration of a mixture of food dyes using simultaneous equations, quantify inorganic phosphate in various aqueous-based agricultural samples, calculate the concentration of salicylic acid in facial acne medication, and elucidate the stoichiometry of an iron salicylate reaction.