Colorimetry is the use of the human eye to determine the concentration of coloured solution Spectrophotometry is the use of instruments to make the same measurements It extends the ID: 560856
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Slide1
COLORIMETRY AND SPECTROPHOTOMETRYSlide2
Colorimetry
is the use of the human eye
to determine the concentration of coloured solutionSpectrophotometry is the use of instruments to make the same measurements. It extends the range of possible measurements beyond those that can be determined by the eye alone.
Useful TerminologySlide3
Visual Observations – Because colorimetry is based on inspection of materials with the human eye, it is necessary to review aspects of visible light.
Visible light
is the narrow range of electromagnetic
waves with the wavelength of
400-700 nm
.
ColorimetrySlide4
Colour
Wheel(ROYGBIV)
Compl
e
mentary colors
lie across the diameter on the
colour
wheel
and combine to form
“white light”
, so the color of
a
compound seen by the eye is the complement of
the color
of light absorbed by a colored
compound; thus it
completes
the color. Slide5
Observed Color of Compound
Color of Light Absorbed
Approximate Wavelength of Light Absorbed
Green
700
nm
Blue-green
600
nm
Violet
550
nm
Red-violet
530
nm
Red
500
nm
Orange
450
nm
Yellow
400
nmSlide6
Observed Color of Compound
Color of Light Absorbed
Approximate Wavelength of Light Absorbed
Green
Red
700
nm
Blue-green
Orange-red
600
nm
Violet
Yellow
550
nm
Red-violet
Yellow-green
530
nm
Red
Green
500
nm
Orange
Blue
450
nm
Yellow
Violet
400
nmSlide7Slide8
Copper Sulphate: Standard solutions that are 0.1, 0.2, 0.3 and 0.4 M CuSO
4
will yield a good Beer’s law curve at 635 nm (red LED). Prepare a stock solution by adding 10g of NH4NO3 to 10mL of 0.1 M CuSO4 and 90 mL of 0.20 M NH3 (forms the Cu(NH3)42+ complex ion) and dilute to obtain standard solutions.