INVESTIGATION of OSMOSIS in POTATO TISSUE
RCNUWC, November 2007
INTRODUCTION
Colorimeter; theory
A colorimeter measures the amount of colored light absorbed by or transmitted through a solution. The
amount of light transmitted for each color (wavelength) of light depends on properties of the solution:
on concentration of dissolved or suspended particles.
Typically, a darker colored liquid will absorb a greater amount of light energy (i.e., less light will be
transmitted through it) than a more transparent liquid with similar properties.
This method of analysis can be particularly useful when a subtle color change (one that is difficult to
observe or quantify with the human eye) occurs as a result of a process, in this case osmosis. Our PASCO's Colorimeter shines a light through a solution and measures the percent transmittance. A
two-line LCD display prompts you through the measurement process.
Use of the Colorimeter
A) Calibration: Fill a cuvette with a distilled water and press button “ON”. Then press simultaneously
“Select” and “Start” and you will see on the display when the calibration is done.
B) Measuring: Insert a cuvette with a solution to be investigated and then press “Select” to chose the
color light to be transmitted, and then “Start”. Do the same with other light colors (wave lengths).
Press “Stop” before inserting measuring the next cuvette.
AIM: 1. To investigate the effects of osmosis on potato tissue and on the color of different
sugar solutions mixed with same amount of paint.
2. Find out the solute concentration of potato tissue.
3. Determine which wavelength works best for such an investigation
HYPOTHESIS: 1.
2.
3.

write all three hypotheses (with an explanation) on the sheet with your
results
PROCEDURE:
Materials & equipment : six 05L beakers, six 5ml beakers, 12 cuvettes, spatula, tweezers
(forceps), potato, cork borer, razor blade, craft paint, ruler, water resistant pen, watch, precise
balance, PASCO colorimeter, Petri dish.
Prepared by the SerEnBio dream-team
1. In six 0.5L beakers : 0.0M, 0.2M, 0.4M, 0.6M, 0.8M, 1M solutions of sugar
2.
Added into each solution: 50ml of prepared dissolved blue craft paint
Students in the lab – work in pairs:
3. Collect 6 small (5ml) beakers and 12 small striped colorimetric containers with plugs.
4. Fill each small beaker, exactly to the 5ml line, with each different painted sugar solution
(mark them prior to adding the solution).
5. Take a fresh potato and, using a cork borer, scoop out two or three cylinders of potato
tissue. Cut the cylinders with the razor blade precisely (using a ruler or mm paper) in
3mm thick discs (no blood please!).
6. Fill 6 marked colorimetric cuvettes with all 6 different painted sugar solutions. Measure
the colorimetric value of each solution for blue, green, orange and red light. Record the
results.
7. Weight 6 sets of four potato discs to 0.00 accuracy
8. Put each set of four potato discs in different small beaker with painted sugar solution, in
the same time.
9. Leave for 15min
10. In the meantime: take the rest of the 6 colorimetric containers and mark them for
different solutions.
11. After 15min, take out the first four potato discs from the painted water without sugar
(control!). Using tweezers-forceps, put the discs on a Petri dish), touch each disc quickly
to some tissue paper to remove extra liquid. Weigh them immediately to 0.00g accuracy.
Repeat the same for potato discs from all other solutions.
12. Take the, already marked, second set of 6 colorimetric containers, and fill each one with
a corresponding solution, which remained after the discs were removed. Measure their
colorimetric values for blue, green, orange and red light and record data.


The solutions in steps 1. And 2. have been prepared by the teacher and SerEnBio, in order to allow
enough time for the rest of experiment. Nevertheless, in your lab report, before presenting
results, write down how exactly these solutions should be prepared, introducing a simple table
with different amounts of sugar in grams.
Here you are given only the AIMs and Procedure. The rest is yours (including hypothesis
with an explanation and variables, including units). ATTACH this sheet to your report.