How does a Colorimeter Work

A colorimeter is a laboratory instrument that determines the concentration of a substance in a sample by the shade of its color. It can often be confused with the use of a spectrophotometer. This article will discuss what a colorimeter is, how it works, and how it differs from a photometer.

What is a colorimeter?

Colorimeter definition: A colorimeter is a device that precisely measures color intensity and variation in samples.

The colorimeter was invented in 1870 by Louis J Duboscq. The device uses Beer-Lambert's law to quantify the concentration of solutes in a solution based on measuring the shade of color of a liquid. A colorimeter is a device used to measure light waves to determine the concentration level of a specific substance.

Main components of a colorimeter

1. Light source: Often an ordinary low-voltage incandescent lamp

2. Cuvette: A test tube containing the working solution.

3. Standard observer: A second-degree standard observer with a small and specific field of view.

4. Photocell: A system for detecting light passing through the sample.

5. Triple Stimulus Absorption Filter: A filter isolates the specific wavelengths applied to the sample.

Types of colorimeters:

Color densitometers: Measure the density of primary colors.

Color photometers measure the transmission and reflection of colors.

Colorimeters can also be compact and portable for use on the go or larger for use on a laboratory benchtop. Different types of colorimeters are suitable for different application requirements, and choosing the right colorimeter can improve the accuracy and efficiency of your measurements.

Principle of operation of the colorimeter:

The functioning of a colorimeter is based on Beer-Ambert's law, which assumes that the absorbance of a liquid sample is proportional to its concentration. The colorimeter shines light onto the liquid sample to analyze the color according to the available standards. A photocell evaluates the amount of absorption at the wavelength and the device then returns the result on a digital display.

In a colorimeter, a beam of light of a specific wavelength is passed through the solution by a series of lenses that direct the colored light to the measuring device. This analyses the color compared to an existing standard. The microprocessor then calculates the absorbance or percentage transmittance. If the solution is more concentrated, more light will be absorbed.

What do colorimeters measure

Colorimeters measure the intensity and concentration of colors by detecting light absorbance or transmittance in a sample, typically across the red, green, and blue (RGB) or visible spectrum.

Difference between a colorimeter and a spectrophotometer

Like the colorimeter, the spectrophotometer measures the color absorption properties of substances. Although closely related, they each have advantages and disadvantages that make them suitable for different measurements.

The main difference is that spectrophotometers use infrared and visible light to measure the transmittance and reflectance of all light colors. In contrast, colorimeters measure the absorbance of specific colors.

1. Uses: Colorimeters are suitable for rapid, quantitative measurement of the concentration of known substances; spectrophotometers are used to study the spectral properties of substances, analyze unknown substances, and conduct qualitative and quantitative analyses.

2. Accuracy: The measurement accuracy of the colorimeter is low, and the measurement error is large, so it is suitable for measurements with lower accuracy requirements. Spectrophotometers can calculate the exact number of photons at a specific wavelength and determine the three-dimensional coordinates of an object's color.

3. Measurement range: Spectrophotometers have a wider measurement range, allowing more complex color measurements and capturing more color detail

4. The direction of measurement: Colorimeters focus on the color analysis of liquid samples, whereas photometers are more widely used for intensity and characteristic measurements of light.

5. Difficulty of operation: Colorimeters are simple and often suitable for quick tests that do not require complex analyses.

Colourimeter Applications:

Colorimeters are widely used in chemical experiments to monitor the growth of bacterial or yeast cultures, and they provide reliable and highly accurate results. They are commonly used to measure and monitor the color of a wide range of food and beverages, including vegetable products and sugar.

As well as being used for basic research in chemistry laboratories, colorimeters have many practical applications, such as testing water quality by screening for chemicals such as dissolved oxygen, fluoride, cyanide, molybdenum, chlorine, iron, zinc, and hydrazine. They are also used to determine the concentration of plant nutrients such as ammonia, nitrogen, nitrates, and phosphorus in soil or hemoglobin in the blood. Colorimetric methods are also used in color printing, textile manufacturing, and paint manufacturing for accurate quality checks.