Colorimeter

Color science is a captivating discipline at the intersection of science and art. It is particularly relevant for secondary education, opening doors to experimentation and fascinating discoveries. At the heart of this science are technological tools such as the spectrophotometer and colorimeter.

Discover FizziQ

How to measure it in class

Steps:

Open FizziQ and select the colorimeter tool
Point the camera at a colored surface
Record the RGB (Red, Green, Blue) values
Compare colors from different samples
Use the color synthesizer to recreate observed colors

Learn more

Spectrophotometer vs. Colorimeter:

The spectrophotometer is a versatile instrument that analyzes object reflectance or transmittance at different wavelengths, allowing precise color quantification and calibration. It is particularly useful for detailed analysis of spectral properties.

The colorimeter focuses on measuring perceptible color characteristics, conforming to standard human eye responses to different wavelengths. It is essentially used to evaluate color quality and accuracy in various contexts, such as industry and design.

Smartphone as colorimeter:

A smartphone, with its sophisticated light sensors and cameras, can be used as a colorimeter. Cameras capture colors and dedicated applications analyze this information to provide color measurements. Light sensors also adjust measurements based on lighting conditions, making smartphones versatile tools for basic colorimetric analysis.

The FizziQ app transforms any smartphone or tablet into a colorimeter. This tool provides real-time quantities of the three primary colors (red, green, blue) needed to recreate the observed color—essentially a simplified spectral analysis.

Calibration importance:

Calibrating a colorimeter or spectrometer is essential to ensure accuracy and reliability. This corrective step adjusts and harmonizes the instrument, compensating for systematic errors and variations due to external factors like temperature, light, or component wear.

Scientific activities on this topic

Several experiments allow you to use FizziQ’s colorimeter in class.

1: Autumn colors - Understanding why leaves change color: https://www.fizziq.org/en/activities/fall-colors/
2: Comparing and classifying colors - Characterizing colors with RGB components: https://fondation-lamap.org/sequence-d-activites/a-la-decouverte-des-couleurs-comment-comparer-et-classer-des-couleurs
3: Beer-Lambert law - Colorimetric titration of a solution: https://ires.univ-tlse3.fr/sim/wp-content/uploads/sites/35/2019/05/Activité-smartphone-Beer-Lambert.pdf

Formula

For colorimetric titration, the Beer-Lambert law is written as:

A = epsilon x l x c

Meaning:

A: absorbance (no unit)
epsilon: molar extinction coefficient (L.mol-1.cm-1)
l: path length through the solution (cm)
c: concentration of the substance (mol/L)

Examples

Blood glucose measurement by colored reaction
Monitoring chlorine concentration in a swimming pool
Measuring chlorophyll content in leaves
Verifying the color of a food product
Studying reaction kinetics through colorimetric monitoring

FAQ

Q: Can you really use a smartphone as a colorimeter? A: Yes, the smartphone camera analyzes the RGB components of light. FizziQ allows you to quantify these components and use them for simple titrations.

Q: What is the accuracy of a smartphone colorimeter? A: It is sufficient for educational lab work. For precision titrations, a laboratory spectrophotometer is still necessary.

Q: What is the difference between a colorimeter and a spectrophotometer? A: A colorimeter measures overall color, while a spectrophotometer breaks down light into wavelengths and measures absorbance at each wavelength.

Q: Why calibrate the colorimeter? A: Calibration corrects errors due to ambient lighting and sensor characteristics. It ensures reproducible measurements.

Q: How to choose the colored filter for a titration? A: Use a filter with a color complementary to the solution. To titrate a blue solution, measure absorbance with an orange filter.

Absorbance - Beer-Lambert law - RGB additive synthesis - Subtractive synthesis - Spectrophotometer - Titration - Complementary colors