This article describes how to construct a simple, inexpensive, and robust colorimeter from a few Lego bricks, in which one light-emitting diode (LED) is used as a light source and a second LED as a light detector. The colorimeter is suited to various grades and curricula.

This article describes how to construct a simple, inexpensive, and flexible UV-photometer using one LED (355 nm) as the light source and another (355 nm) as the detector, one resistor, some wiring, a few Lego bricks, and a millivolt meter. The photometer is used to explore several aspects of molecular absorption spectrometry. As practical applications, the amounts of folic acid in folic acid tablets and cinnamaldehyde in cinnamon were found. The results were in accordance with those obtained using a commercial spectrophotometer.

This article describes a combined UV-photometer and fluorimeter constructed from 3 LEDs and a few wires, all held in place with Lego bricks. The instrument has a flexible design. In its simplest version, two UV-LEDs (355 nm) are used as light source and to detect absorption, and a third LED, in the visible spectrum (e.g., 525 nm), is used to detect fluorescence. Various experiments are described: fluorescence as a function of concentration and light source intensity; quantitative measurements of quinine in tonic water, using absorption and fluorescence measurements, with results in line with those obtained on scientific instruments; a demonstration of the inner filter effect reducing fluorescence at higher concentrations; investigation of the effect of drinking tonic water on the fluorescence of quinine in urine; temperature effects on fluorescence; chloride-ion quenching of fluorescence with result comparable to those previously reported; and, finally, a demonstration of phosphorescence.

This correction incorporates a relevant reference, "A Concept of Dual Optical Detection Using Three Light Emitting Diodes", to a work on a combined UV-photometer and fluorimeter constructed from three LEDs, wires, and LEGO bricks, featuring a flexible design for various experiments.