Colorimeter – Definition, Principle, Parts, Procedure, Applications

Colorimeter is a light sensitive analytical instrument used to measure absorbance and transmittance of light. It measures selected wavelength of light when it passes through a coloured solution. It is mainly used for finding the concentration of coloured solution.

The working of colorimeter is based on Beer-Lambert law. According to this law, the amount of light absorbed by a coloured solution is directly proportional to the concentration of solute present in it. So, more concentrated solution absorbs more light.

In colorimeter, light is passed through absorption filters. These filters may be red, green and blue filters. They select the particular wavelength of light and it works similar to the colour perception of human eye.

The unabsorbed light is received by a photoelectric detector. The detector changes this light into electrical signal. This gives numerical value of colour, absorbance or transmittance.

Colorimeter is used in quality control and concentration analysis. It is used in textile, food and beverage, pharmaceutical and clinical diagnostic fields. It gives more objective result than only visual colour comparison.

The history of colorimeter is related with James Clerk Maxwell. In 1860, he made a primitive colorimeter called colorbox. It used prism for controlling red, green and blue light beams separately for matching sample colour.

Another important development was done by Louis Jules Duboscq. He designed the Duboscq colorimeter around 1854 and showed improved form in 1868. This instrument compared colour intensity of test solution with standard solution.

Later photoelectric colorimetry developed in the mid 1930s. It replaced visual comparison by objective sensors. In 1938, William Henry Summerson introduced a colorimeter using photocell. After World War II, selenium photocell colorimeters were produced commercially and this helped in development of modern digital colorimeters.

Principle of Colorimeter – How does a colorimeter work?

Principle of Colorimeter is based on Beer-Lambert law. In this law, the light absorbed by a coloured solution is directly related with the concentration of the solute and the path of light. When the solution is more concentrated, it absorbs more light.

In colorimeter, the light is first produced by light source. It may be tungsten lamp or LED. The light then passes through a filter. The filter allows only a selected wavelength of light to pass.

This selected light is passed through the sample kept in a cuvette. The cuvette is a transparent tube or small container. The coloured solution absorbs some part of the light.

The remaining light comes out from the solution. This transmitted light is received by photoelectric detector or photocell. The detector changes the light into electrical signal.

The reading is shown as absorbance, optical density or percentage transmittance. The reading is compared with blank solution or calibration curve. From this, the concentration of the coloured substance is determined.

Diagram of Colorimeter

Mathematical Equation of Colorimeter

The mathematical equation of colorimeter is based on Beer-Lambert law. The equation is as follows-

A = εcl

where,
A = Absorbance or optical density.
ε = Molar absorptivity or molar extinction coefficient.
c = Concentration of absorbing substance.
l = Path length of light through the cuvette.

Here, absorbance shows how much light is absorbed by the coloured solution. ε is a constant for a particular substance at particular wavelength. c shows the amount of solute present in the solution. l is the distance travelled by light through the sample.

Absorbance can also be written from the intensity of light. The equation is as follows-

A = -log (I / I₀)

where,
I₀ = Intensity of incident light.
I = Intensity of transmitted light.

Another form of equation is-

A = 2 – log (%T)

where,
%T = Percentage transmittance.

From this equation, absorbance is directly proportional to concentration and path length. So, when concentration increases, absorbance also increases. By using this relation, unknown concentration of coloured solution is determined.

Parts of Colorimeter

The main parts of colorimeter are as follows-

1. Light source
   It gives light for the measurement. The light source may be tungsten filament lamp, LED or halogen lamp. It provides the required light for passing through the sample.
2. Adjustable slit or aperture
   It is used to make the light beam narrow. It also reduces unwanted light or stray light from entering into the system.
3. Condensing lens
   It focuses the light which passes through the slit. It makes the light into a parallel beam before going to the filter.
4. Filter or monochromator
   It selects the required wavelength of light. The filter may be coloured glass filter, dyed gelatin filter, interference filter, prism or grating. It allows only particular light to pass.
5. Cuvette or sample holder
   It is a small transparent tube or rectangular container. It holds the coloured liquid sample. It is made up of glass, quartz or plastic.
6. Photodetector or photocell
   It is a light sensitive part of the colorimeter. It receives the light coming out from the sample. It changes the light energy into electrical signal.
7. Processor or amplifier
   It receives the electrical signal from the photodetector. It amplifies and processes the signal. This helps in getting proper reading.
8. Meter or digital display
   It shows the final reading to the user. The reading may be absorbance, optical density or percentage transmittance. In some colorimeters, galvanometer is used for showing the reading.

Colorimeter Operating Procedure

1. The colorimeter is first switched on. It is kept for warm up for about 5 to 15 minutes. This is done for stabilizing the light source and detector.
2. The proper wavelength or filter is selected. It is selected according to the test or assay which is to be done.
3. A blank solution is prepared in a clean cuvette. The cuvette is filled about two-third or three-fourth. Distilled water or pure solvent is generally used as blank.
4. The outer side of cuvette is wiped with lint free tissue. Any water drop, dust or finger mark should not present on it. These can scatter light and give wrong reading.
5. The blank cuvette is placed inside the sample chamber. It is kept properly in the path of light. The cover is then closed.
6. The instrument is adjusted to 100% transmittance or 0.00 absorbance. This is called zeroing of the instrument. It gives the baseline reading.
7. The blank cuvette is removed. Another clean cuvette is filled with the unknown sample solution. The outside of this cuvette is also wiped properly.
8. The sample cuvette is placed inside the chamber. The lid is closed. The absorbance or percentage transmittance value is then read from the display.
9. The reading is recorded. After the test, the sample cuvette is removed. The solution is discarded safely and cuvettes are cleaned properly. The instrument is also cleaned to prevent scratch and chemical damage.

Types of Colorimeter

The types of colorimeter are as follows-

1. Tristimulus colorimeter
   This type of colorimeter uses three optical filters. These are red, green and blue filters. It works similar to colour perception of human eye. It detects the intensity of primary colours and is used for routine quality checking.
2. Spectral colorimeter
   Spectral colorimeter measures light absorbance at different optical wavelengths. It uses prism instead of simple limited filters. It gives more accurate result and is useful in biochemical and environmental research work.
3. Densitometer colorimeter
   This colorimeter uses single filter. It is used to measure darkness, density or particular light intensity of a material. It is also used for semi-transparent materials and for checking bacterial and yeast growth.
4. Photometer
   Photometer is used for measuring the transmission and reflection of colour by a sample. It mainly checks how much light is passed or reflected from the sample.
5. Benchtop colorimeter
   Benchtop colorimeter is large and stable instrument. It is used in laboratory condition. It is used for research work and high precision reference measurement.
6. Portable colorimeter
   Portable colorimeter is small and light weight. It is mostly battery operated. It is used for field testing like water quality analysis and factory production line checking.
7. Visual colorimeter
   Visual colorimeter is a traditional type of colorimeter. In this type, the colour of sample is compared with standard solution by human eye. It depends on visual observation.
8. Photoelectric colorimeter
   Photoelectric colorimeter uses photocell instead of human eye. It detects the intensity of light automatically. From this, the concentration of coloured solution is calculated.
9. Analog colorimeter
   Analog colorimeter has a physical scale and moving arrow. The upper number shows transmittance and the lower number shows absorbance. It gives reading by pointer movement.
10. Digital colorimeter
    Digital colorimeter is modern type of colorimeter. It has microprocessor and LED screen. It gives fast numerical reading and may have data storage, calibration record and computer connection.

Calibration Procedure for a Colorimeter

1. The colorimeter is first switched on. It is allowed to warm up for about 5 to 15 minutes. This helps the light source and detector to become stable.
2. The proper wavelength is selected. The wavelength knob is adjusted or suitable optical filter is selected. It is done according to the chemical test which is performed.
3. The blank solution is prepared in a clean cuvette. The blank may contain distilled water or same solvent and reagents. But the analyte is not present in blank.
4. The outer surface of cuvette is wiped with lint free tissue. Finger marks, dust and water drops should not present on it. These may scatter light and give wrong reading.
5. The blank cuvette is inserted into the sample chamber. It is placed in proper alignment with the light path. Then the calibration button is pressed or knob is adjusted.
6. The instrument is adjusted to 100% transmittance or 0.000 absorbance. This is called zeroing of the colorimeter. It removes the effect of cuvette and solvent from the reading.
7. For quantitative analysis, standard solutions are prepared. About 3 to 10 standard solutions of known concentration are taken. Their concentration should cover the test range.
8. The absorbance of each standard solution is measured. Then absorbance is plotted against concentration. This gives the calibration curve.
9. The blank cuvette is removed. The cuvette containing unknown sample is then inserted. The absorbance of the unknown sample is read from the display.
10. The concentration of unknown sample is found by comparing its absorbance with calibration curve. This gives the amount of substance present in the sample solution.

Applications of Colorimeter

• Colorimeter is used in medical and clinical diagnosis. It is used for testing biological samples like blood, urine, cerebrospinal fluid and plasma.
• It is used for estimation of biochemical substances. Hemoglobin, glucose, urea and cholesterol can be measured by colorimeter.
• It is used in some advanced tests for detection of disease markers. Colorimetric sensors can also be used for detecting some disease biomarkers from exhaled breath.
• In water and environmental analysis, colorimeter is used for checking water purity. Chemicals like chlorine, fluoride, iron, ammonia and phosphate are measured by this instrument.
• It is also used in agriculture. Soil nutrients are tested by colorimeter. Plant health can also be measured by estimation of chlorophyll.
• In food and beverage industry, colorimeter is used for checking freshness of food. It is used to find ripeness of fruits and vegetables and baking condition of food.
• It is used for maintaining colour uniformity in beverages, ingredients and processed foods. It can also be used in smart packaging for detecting food spoilage.
• In textile industry, colorimeter is used for checking dye and fabric colour. It helps in shade matching from raw yarn to finished garment.
• It is used for colour fastness testing. This shows how the fabric colour remains after light, washing and rubbing.
• In paints, coatings and plastics, colorimeter is used to maintain pigment stability and colour accuracy. It is used in automotive parts, architectural coatings and plastic packaging.
• In pharmaceutical industry, it is used for checking colour of medicines. It helps to identify inferior or degraded products.
• In cosmetic industry, colorimeter is used for maintaining same shade in makeup and skin care products. It can also measure UV protection level of some formulations.
• In displays and electronics, colorimeter is used for checking colour contrast and brightness of screens. It is used in television, mobile phones and computer monitors.
• In printing industry, it is used for measuring ink density. It is also used for checking printing paper quality and maintaining brand colour standard.
• It is also used in special works. Diamond dealers use it for checking visual characters of stones. Researchers use it for measuring bacterial and yeast growth density. It is also used for finding counterfeit luxury goods.

Advantages of Colorimeter

• Colorimeter is less costly instrument. It is cheaper than advanced instruments like spectrophotometer. So it can be used for basic colour analysis in many laboratories.
• It is simple to operate. Only few manual steps are needed. Very much technical training is not required for routine testing.
• It gives result very fast. In many cases, reading is obtained within very short time. So it is useful in production line and quick testing work.
• It is small and easy to carry. Many colorimeters are battery operated. So it can be used for field testing and outdoor analysis.
• It gives focused colour data. It mainly works with red, green and blue colour values. Full spectral data is not needed when only simple colour comparison is required.
• It is useful for quantitative analysis. Coloured chemicals and solutions can be measured by it. The concentration of unknown solution can be found from absorbance reading.
• It is useful for unstable coloured samples. Some coloured complexes change quickly. In such cases, colorimeter can take photometric reading in short time.

Limitations of Colorimeter

• Colorimeter cannot detect metamerism. Two colours may look same in one light source but different in another light source. Colorimeter cannot identify this properly.
• It does not give full spectral data. It mainly uses red, green and blue filters. So small colour differences may not be detected.
• It is not suitable for complex colour formulation and deep research work. For this, more advanced instrument is needed.
• Colorimeter works only in visible range. The range is about 400 nm to 700 nm. It cannot measure in ultraviolet and infrared region.
• It cannot measure colourless substance directly. If the solution is clear, then reagent has to be added. This forms coloured complex for measurement.
• It has less sensitivity and precision than spectrophotometer. At very high concentration, accuracy becomes less. When absorbance is more than 1.0, the result may not follow Beer-Lambert law properly.
• The reading may be affected by physical interference. Ambient light, stray radiation, turbidity, scratched cuvette and reflecting surface can give wrong reading.
• Chemical interference may also occur. If other compounds of similar colour are present, then error may come in result.
• Temperature change and instability of sample can affect the reading. Some samples may change during measurement.
• The light source should be stable. If the light intensity changes, then the measurement becomes incorrect.
• It generally needs more sample volume than spectrophotometer. So it is not suitable when very small amount of sample is available.

Precautions of Colorimeter

• The cuvette should be cleaned properly before use. The outer side is wiped with lint free tissue. Finger marks, water drops, oil and dust should not present on it.
• The clear side of the cuvette should not be touched. It is the side through which light passes. Scratches on this side may scatter light and give wrong reading.
• Air bubbles should not present in the solution. If bubbles are present, they should be removed before reading. Bubbles can block light path and affect the result.
• Solid particles and precipitates should be removed from the sample. The solution is filtered if needed. Clear solution gives more proper reading.
• The cuvette should be filled with proper volume of solution. It is generally filled two-third or three-fourth. In some cuvettes, it is filled up to the triangular mark.
• The cuvette should be placed in same direction every time. Change in position may give error due to small difference in shape of cuvette. The cuvette should be closed with cap to prevent spilling.
• Blank calibration should be done before sample reading. Blank solution contains solvent without analyte. It gives zero absorbance base line.
• Correct wavelength should be selected before blanking. Wrong filter or wavelength gives wrong absorbance value.
• The colorimeter should be kept in dry and cool place. Humid place, water mist and flashing light should be avoided.
• The power supply should be steady. Voltage stabilizer may be used. The instrument should not be kept near vibrating machines like centrifuge.
• Liquid, powder or any solid particles should not enter into the measuring chamber. It may damage the instrument and also affect the reading.
• Some space should be kept around the colorimeter. At least 3 inches space is kept for proper ventilation. This helps to remove heat from the instrument.
• Reference standards or white calibration tiles should be kept clean. Scratched, dirty or discoloured standard can give error in every measurement.

Colorimeter vs Spectrophotometer

• Colorimeter uses three optical filters. These are red, green and blue filters. It works like the colour perception of human eye. Spectrophotometer uses prism or diffraction grating. It separates light into full spectrum.
• Colorimeter gives basic colour value. It may give RGB or CIE Lab value. Spectrophotometer gives detailed spectral reflectance or transmittance data.
• Colorimeter generally works in visible light range. The range is about 400 to 700 nm. Spectrophotometer works in wider range. It can measure UV, visible and IR region.
• Colorimeter uses simple light source like tungsten lamp or LED. Spectrophotometer may use hydrogen, deuterium or halogen lamp.
• Spectrophotometer gives more accuracy and sensitivity. It can detect small colour differences. Colorimeter gives moderate accuracy and is used for simple colour comparison.
• Spectrophotometer can detect metamerism. It can check colour under different light conditions. Colorimeter cannot detect metamerism properly because it uses fixed light source.
• Colorimeter is used for quick checking and routine quality control. It is also used in simple field tests. Spectrophotometer is used for colour formulation, spectral analysis and research work.
• Colorimeter is less costly and easy to use. It is often portable. Spectrophotometer is more costly and more complex instrument. It is mostly used as benchtop instrument.
• Spectrophotometer can test more types of samples. Solids, powders and liquids can be analysed by it. Colorimeter is mainly used for coloured solution and usually needs more sample volume.
• Colorimeter is useful when fast and simple result is needed. Spectrophotometer is useful when detailed and exact result is needed.

References

1. ResearchGate. (n.d.). (PDF) A Smartphone-Based Automatic Measurement Method for Colorimetric pH Detection Using a Color Adaptation Algorithm. [URL]
2. ResearchGate. (n.d.). (PDF) Determination of phosphorus by phosphorus molybdenum blue spectrophotometry by bismuth antimony sensitization. [URL]
3. ResearchGate. (n.d.). (PDF) Nessler Method Verification for Determining Ammonia in Shrimp Pond Wastewater and Its Application in the Ammonia Adsorption Test with Lampung Natural Zeolite. [URL]
4. Avila, I. (2022, January 24). 3.3: Determination of Phosphate by a Colorimetric Method. Chemistry LibreTexts. [URL]
5. HunterLab. (2023, February 8). 6 Uses of Colorimetry in Real Life. [URL]
6. Linshang Technology. (2025, September 2). A Fabric Colorimeter in the Textile Industry. [URL]
7. Habibah, N., Dhyanaputri, I. G. A. S., Karta, I. W., Sundari, C. D. W. H., & Hadi, M. C. (2018). A simple spectrophotometric method for the quantitative analysis of phosphate in the water samples. Jurnal Sains dan Teknologi, 7(2), 198-204. [PDF]
8. Kim, S. D., Koo, Y., & Yun, Y. (2017). A Smartphone-Based Automatic Measurement Method for Colorimetric pH Detection Using a Color Adaptation Algorithm. Sensors, 17(7), 1604. MDPI. [URL]
9. Zhang, G., Song, S., Panescu, J., Shapiro, N., Dannemiller, K. C., & Qin, R. (2023). A novel systems solution for accurate colorimetric measurement through smartphone-based augmented reality. PLoS ONE, 18(6), e0287099. [URL]
10. GAO Tek. (n.d.). Applications of Colorimeters in Food and Beverage. [URL]
11. Edinburgh Instruments. (2021, July 8). Beer-Lambert Law | Transmittance & Absorbance. [URL]
12. FindLight. (2024, December 18). Beer-Lambert’s Law: Principles and Applications in Daily Life. [URL]
13. RevisionDojo. (2025, November 21). Beer–Lambert Law Explained Simply. [URL]
14. PatSnap. (2025, July 15). CIE standards vs ASTM colorimetry methods: Which is more suitable for your application? [URL]
15. Sandha, S. V., & Kuldeep, T. (n.d.). COLORIMETER AND LAMBERT’S-BEER’S LAW. [PDF]
16. UKEssays. (2018, November). Calorimetry Steps and Analysis. [URL]
17. PMC – NIH. (n.d.). Cell Phone based Colorimetric Analysis for Point-of-Care Settings. [URL]
18. HunterLab. (2023, January 3). Color Measurement of Wine – HunterLab Horizons Blog. [URL]
19. Ranjan, V. (2026, May 5). Color Testing for Materials: Measurement Methods, Standards & Instrumentation. Infinita Lab. [URL]
20. Wikipedia. (2026, May 12). Colorimeter (chemistry). [URL]
21. Malhotra, V. (2025, May 16). Colorimeter Explained: How It Works, Types, and Uses in Industries. Presto Group. [URL]
22. Critchley, L. (2017, May 24). Colorimeter Principles and Applications. AZoM. [URL]
23. Vernier. (n.d.). Colorimeter User Manual. [URL]
24. Hinotek. (n.d.). Colorimeter VS Spectrophotometer. [URL]
25. Torontech. (2026, April 13). Colorimeter vs Spectrophotometer: Key Technical Insight. [URL]
26. Mishra, R. (2025, October 3). Colorimeter vs Spectrophotometer: Understand the Difference. Testronix. [URL]
27. Karki, P. (2023, January 13). Colorimeter- Definition, Principle, Parts, Uses, Examples. Microbe Notes. [URL]
28. BioScience.com.pk. (n.d.). Colorimeter: Principle, Uses, and How It Works. [URL]
29. Linshang Technology. (2025, August 25). Colorimeters for Accurate Fabric Color Measurement. [URL]
30. Konica Minolta Sensing Europe. (n.d.). Colorimeters vs. Spectrophotometers – Measuring Instruments. [URL]
31. ResearchGate. (n.d.). Colorimetric Evaluations and Characterization of Natural and Synthetic Dyes/Pigments and Dyed Textiles and Related Products. [URL]
32. UNSW. (n.d.). Colorimetric Sensors for Food & Health Monitoring | Scientia Program. YouTube. [Youtube]
33. Wikipedia. (2026, February 16). Colorimetric analysis. [URL]
34. PMC. (n.d.). Colorimetric sensing for translational applications: from colorants to mechanisms. [URL]
35. Schaefer, S. (2014). Colorimetric water quality sensing with mobile smart phones (Master’s thesis). UBC Library Open Collections. [URL]
36. Konica Minolta Sensing Europe. (n.d.). Colour measurement solutions for the food industry. [URL]
37. Dash Asia. (n.d.). Colourimeter vs. Spectrophotometer: What’s the Difference? [URL]
38. Comprehensive Analysis of Colorimetric Instrumentation: Theoretical Principles, Engineering Architecture, and Multi-Sectoral Applications. (n.d.). [Markdown]
39. Hydro Instruments. (n.d.). DPD Method: Chlorine & Chemical Measurements. [URL]
40. The Department of Chemistry, UWI, Mona, Jamaica. (n.d.). Experiment 36. The colourimetric determination of phosphate. [URL]
41. Shrestha, Y. K., & Shrestha, S. K. (2023, October 20). Fundamentals of Colorimetry. IntechOpen. [URL]
42. Higgins, C. (2005, July). Hemoglobin and its measurement. Acutecaretesting.org. [URL]
43. Hach Support. (2022, August 6). How is a calibration curve prepared in a colorimeter or spectrophotometer? [URL]
44. Lee, J. (n.d.). Industrial Colorimeter: Everything You Need to Know. Threenh. [URL]
45. Erun Environmental Protection. (2025, August 8). Measuring Ammonia Nitrogen in Water: The Nessler Reagent Photometric Method and Portable Solutions. [URL]
46. ETS Labs. (2025, September). Measuring wine color. [URL]
47. National Environmental Methods Index. (1974). NEMI Method Summary – 350.2 (Nesslerization). [URL]
48. Wisdom Library. (n.d.). Nessler’s Method: Significance and symbolism. [URL]
49. Performing Colorimetry QA/QC in Beverage Production Using Spectrophotometers. (n.d.). [URL]
50. Abrams, E. (n.d.). Phosphate Analysis. Water Quality Analysis. [URL]
51. ACCP. (n.d.). REFERENCE VALUES FOR COMMON LABORATORY TESTS1. [PDF]
52. Werner, P. (n.d.). Setting up the Colorimeter and establishing a blank. YouTube. [Youtube]
53. HunterLab. (2026, February 4). Spectrophotometer vs. Colorimeter: What’s the Difference? – HunterLab Horizons Blog. [URL]
54. Konica Minolta Sensing Europe. (n.d.). Spectrophotometers vs. Colorimeters: Tools for traceable measurement of colour. [URL]
55. Analytik Jena. (2024, June). Spectrophotometric Determination of Chromatic Characteristics According to Compendium of International Methods of Wine and Must. [PDF]
56. Harrill, A. H., Borghoff, S., Zorrilla, L., et al. (2018, June). Table 3, Reference Ranges for Clinical Chemistry Parameters. NTP Research Report on Baseline Characteristics of Diversity Outbred (J:DO) Mice Relevant to Toxicology Studies, NCBI. [URL]
57. LaMotte. (n.d.). Test Techniques for Colorimetric Meters. [URL]
58. X-Rite Spectrophotometers and Software. (n.d.). Textile & Fabric Color Measurement. [URL]
59. Eppendorf US. (2019, November 3). The Blank in Photometry. [URL]
60. Admesy. (n.d.). The Working Principle of a Colorimeter for Display Applications. [URL]
61. YSI. (n.d.). Total Chlorine DPD Reagent Set. [URL]
62. USING A SPECTROPHOTOMETER. (n.d.). userhome.brooklyn. [PDF]
63. Metro Dyeing. (n.d.). Understanding ΔE: The Science of Color Matching in Textile Dyeing. [URL]
64. Thomas Scientific. (n.d.). Water Quality. [URL]
65. ALWSCI. (2025, April 24). What Is Colorimetry And Why Is It Widely Used in Chemical Analysis? – News. [URL]
66. HunterLab. (2026, February 3). What Is a Colorimeter, and How Does It Work? [URL]
67. Malhotra, V. (2025, October 9). What Is a Colorimeter? Definition, Working & Key Advantages. Presto – Testing Instruments. [URL]
68. Malhotra, G. (2025, March 3). What is a Colorimeter? A Complete Guide to Color Measurement. Presto Group. [URL]
69. Mishra, R. (2019, December 31). What is a Colorimeter? Principle, Diagram, Types, and Uses. Testronix. [URL]
70. sisco.com. (2023, July 3). What is the Calibration Process for Colorimeters? [URL]
71. Hach Support. (2022, August 6). What is the scientific principle of colorimetry? [URL]
72. Reagecon. (n.d.). Why do I need to perform a ‘blank’ before measuring my samples in my photometer. [URL]
73. Filo. (2026, February 15). Why is a blank solution used to set the instrument for performing experiment of determination of copper by colorimeter. [URL]