5. • Define colorimetry
• Understand color and absorption of light in accordance with colorimetry
• Determine and explain the two fundamental laws of colorimetry
• Explain how to determine the concentration of a solution using colorimetry
• Define colorimeter and determine the parts of a colorimeter
• Explain the principle and working of a colorimeter
• Determine the advantages and disadvantages of colorimeter
• Identify the techniques of colorimetry
• Explain the uses of colorimetry
13. examples of coloured aqueous solution:
Copper sulfate dissolved in water produces
a blue solution [CuSO4(aq)]
Potassium permanganate dissolved in water
produces a purple solution [KMnO4(aq)]
Acid-base indicator solutions come in
a wide range of colours
26. Combined Beer’s-Lambert’s Law
Expressed as the amount of light transmitted through
a colored solution decreases exponentially, with
increases in the concentration of colored solution &
increase in the pathlength of the cuvette or thickness
of the colored solution
27. Beer-Lambert law states that the absorbance of a
substance is proportional to its concentration and the
path length of the sample. The law is expressed as
A = εbc,
where A is the absorbance, ε is the molar absorptivity,
c is the concentration and b is the path length.
32. Step 1:
• Prepare a set of standard solutions of known
concentration of the substance of interest.
Step 2:
• Prepare the unknown solution to be tested. This can be
done by diluting a concentrated solution or by
dissolving a known amount of the substance in a
solvent.
33. Step 3:
• Determine the wavelength of light that is
best absorbed by the substance being
measured.
Step 4:
• Set up the colorimeter, ensuring that it is
calibrated correctly.
34. Step 6:
• Plot the absorbance vs concentration
for each standard solution on a graph.
Step 5:
• Measure the absorbance of each standard
solution and the unknown solution at the
chosen wavelength
35. Step 7:
• Use the graph to determine the concentration of
the unknown solution by comparing its
absorbance to the absorbance of the standard
solutions.
Step 8:
• Draw the line of best fit through the data points.
This is the calibration curve.
36.
37. Step 9:
• Use the calibration curve to
determine the concentration of this
solution.
Step 10:
• Record the concentration of the
unknown solution.
38. Describe how colorimetry can be used to determine the
concentration of an unknown copper II sulphate solution.
• Colorimetry red light from the LED light source
will pass through the solution and strike a
photocell.
• A higher concentration of the colored solution
absorbs more light (and transmits less) than a
solution of lower concentration.
• The colorimeter monitors the light received by the
photocell as percent transmittance.
39. • By locating the absorbance of the unknown on the vertical axis of the
graph, the corresponding concentration can be found on the horizontal
axis.
• The concentration of the unknown can also be found using the slope of
the Beer’s law curve.
50. light after passing through slit
falls on condenser lens which
gives a parallel beam of light
C. LENS
51. - made of colored glass
D. FILTER
- absorbs light of unwanted
wavelength and allow only
monochromatic light to pass
through
- filter used is always
complimentary in color to the
color of solution
52. - Changeable optics filters are used in
the colorimeter to select the
wavelength which the solute absorbs
the most, in order to maximize
accuracy
D. FILTER
55. - also known as sample holder
E. CUVETTE
- made up of special/plastic/quartz
meterial
maybe square/rectangular/round
shape with fixed diameter (usually 1
cm) & having uniform surface
56. - also known as the photo cell
- converts light energy into electrical
energy
- the electrical signal generated is
directed proportional to intensity of
light falling on the detector
F. DETECTOR
- photosensitive elements
57. - the electrical signal generated in
photocell is measured by
galvanometer that displays percent
transmission & optical density
- output may be displayed by an
analogue or digital meter
- will be shown as transmittance (a
linear scale from 0-100%) or as
absorbance (a logarithmic scale from
zero to infinity)
G. OUTPUT
Galvanometer - a device that is
used to detect a small electric
current or measure its magnitude
58. - useful range in absorbance scale is
0-2, above the range of 2 is considered
useless
G. OUTPUT
Galvanometer - a device that is
used to detect a small electric
current or measure its magnitude
59.
60. • A colorimeter measures the intensity of light absorbed or transmitted by a
sample at different wavelengths.
• A colorimeter, also known as a philtre photometer, is an analytical system
that calculates the absorption of a certain wavelength of light as a method
to calculate a solution concentration.
• The measurement is carried out by passing light of a particular
wavelength through the sample and measuring the intensity of the
transmitted or reflected light.
61. • The measurement is then compared to the intensity of the light transmitted
through a reference sample.
• The ratio of the intensities of the two samples is used to determine the
absorbance or transmittance of the sample at that wavelength.
• The amount of light absorbed or transmitted by a colored solution is in
accordance with two laws:
> Beer’s Law > Lambert’s Law
62. • Important Terms
Io= Incident Light or the light being
passed through the solution.
I = transmitted light
A= light absorbed in the solution
• Transmittance (T) ratio of the intensity of
light leaving solution (I) to the intensity of
light entering solution.
75. • This technique used to measure the intensity of
light. It is used to study the color and brightness
of light sources and samples.
Techniques of Colorimetry
• This technique measures the absorption or transmission of
light by a sample. It provides information about the
concentration of a substance in a sample.
SPECTROPHOTOMETRY
PHOTOMETR
Y
76. REFLECTANCE SPECTROPHOTOMETRY
COLOR DIFFERENCE MEASUREMENT
• This technique measures the amount of light reflected from a
surface. It provides information about the color and properties of
surfaces.
• This technique measures the difference between two colors. It is used
to compare the color quality of a sample to a reference material.
77. COLOR MATCHING
COLORIMETRIC TITRATION
• It is a technique used to match the color of a sample to a standard
reference material. It is used in various fields like printing,
manufacturing, and cosmetics.
• It is a technique used to determine the concentration of a
substance in a sample. It is based on the color change that
occurs when a chemical reaction takes place between the
sample and a reagent.
78. FLUORIMETRY
CHROMATOGRAPHY
• This technique measures the fluorescence emitted by a sample when it
is excited by a source of light. It is used to study the properties of
fluorescent materials.
• It is a technique used to separate and analyze the components of a
sample. It is based on the differential migration of the components in a
mobile phase through a stationary phase.
79. How colorimeter is used in real world?
To track the growth of a bacterial or yeast colony,
colorimeters are commonly used. When used for the
evaluation of colour in bird plumage, they have
accurate and extremely detailed results. They are used
in various foods and drinks, including vegetable
products and sugar, to quantify and track colour.
80. Uses of Colorimetry
It is used in laboratories and hospitals to
estimate biochemical samples such as urine,
cerebrospinal fluid, plasma, serum, etc.
It is used in the manufacturing of
paints.
It is used in textile and food
industry.
81. It is used in the quantitative analysis of proteins,
glucose, and other biochemical compounds.
It is used to test water quality.
It is used to determine the concentration of
haemoglobin in the blood.
