Paper Chromatography
And Rate of Flow
What is Chromatography?
• Chromatography is a useful method for
separating mixtures.
• The components of a mixture are not
chemically combined (or bonded).
Therefore, they can be separated.
What is Chromatography?
• Many mixtures, such as food coloring and
ink, consist of two or more dyes blended
together.
• After completing a paper chromatography,
you will see a pattern of colors appear.
• Each color or shade of color will be a
single component of the whole mixture.
• These dyes dissolve at different rates.
Why do the Dyes Separate
• These dyes dissolve at different rates
because of their densities and size.
• The smaller the dye size the further it will
travel
• How will these rocks be arranged after the
fireman turns on his hose FULL BLAST?
Direction of Flow
What about the distance traveled?
• The distance that a component travels is a
property of the dye and the solvent (the
liquid that is dissolving the ink).
• This distance is unique for each dye in
each solvent. (as long as you use the same
solvent, the dye will always travel at the same
rate.)
Rate of Travel
• The rate at which the components travel
from the Origin to the Finish Line is call
the Rate of Flow. (It is abbreviated as Rf ).
Finish Line
Origin
How to Calculate Rate of Flow
1. Find the center of each component of
the dye and mark it on the paper.
2. Measure the distance
from the Origin to the
center of each
component of the dye.
3. Measure the distance
from the Origin to the
Finish Line
5
Finish Line
4
3
2
1
Origin
How to Calculate Rate of Flow
• Calculate the rate of flow for each component by using
the following formula:
Rf
=
Distance the component traveled
Distance to the Finish Line
• The Rf will always be less than or equal to one.
• If the component of the dye is found closer to the
Finish line, the Rf will be closer to the number ONE
• If the component of the dye is found closer to the
Origin line, the Rf will be closer to the number ZERO
Practice Problem
Distance from the Origin to the
Center of Dye component = 3.45
Distance from the Origin to
the Finish Line = 5.15 cm
Rf
=
3.45 cm
5.15 cm
=
0.67
cm