| Home Page > | CO2 Test Instructions |
Step 1. In order to determine the amount of dissolved carbon dioxide (CO2) to test your hypothesis about how water temperature affects dissolved gases, you will use a LaMotte test kit. The photos below show the test kit and its contents.
Step 2. Each group will test water samples of cold, room temperature, or hot water THREE times and then average the results. We will combine the results from each group by writing each group's results on the front board. You are responsible for copying these overall results from the board to your lab worksheets.
Your instructor will tell you which water sample your group is responsible for (cold, room temperature, or hot).
Step
3. After obtaining your water sample, use the thermometer to
measure its temperature. Record this temperature on the front board. |
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| Step 4. Pour 20ml of the water sample into the titration tube. |  |
Step 5. Add two drops of the Phenolphthalein reagent to the titration tube and mix by swirling gently.
Step 6. IF the water sample in the titration tube turns pinkish-red AND STAYS pinkish red after 30 seconds go by, then there is NO dissolved carbon dioxide in the water sample. In other words, there is 0 ppm (parts per million) of dissolved carbon dioxide present. If this occurs, skip to Step 15. IF the water sample in the titration tube does not turn pinkish-red (or does not remain pinkish-red after 30 seconds), proceed to Step 7. |
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| Step 7. Cap the titration tube with the small cap with the hole in the middle. |  |
| Step 8. Pick up the Titrator and fully depress the plunger. |  |
| Step 9. Open up the Carbon Dioxide reagent bottle. Insert the red tip of the Titrator into the hole in the top of the opened Carbon Dioxide reagent bottle. |  |
Step 10. Invert (turn upside down) the Carbon Dioxide reagent bottle. Hold the bottle and the Titrator firmly together! Slowly pull out the plunger on the Titrator until the large green ring on the plunger is opposite the zero (0) line on the scale that is printed on the side of the Titrator. The Titrator will fill with Carbon Dioxide reagent.
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Step 11. If an air bubble appears in the Titrator, pump the Carbon Dioxide reagent solution back into the inverted Carbon Dioxide reagent bottle to expel the bubble and go back to Step 10.
Step 12. Turn the Carbon Dioxide reagent bottle right side up and remove the Titrator.
Step 13. Insert the tip of the Titrator into the open hole in the titration tube (which contains 20ml of the water sample). Slowly deperess the plunger to dispense the titrating solution. Gently swirl the tube to mix the solution.
ADD one drop at a time! and wait to see if the solution turns pinkish-red.
If the solution does NOT turn pinkish-red after a few seconds, add another drop.
If the solution DOES turn pinkish-red after a few seconds, wait 30 seconds to see if the pinkish-red color persists or fades away.
If the pinkish-red color fades away, add another drop to the water sample in the titration tube.
If after 30 seconds, the pinkish-red color remains, read the test result directly from the scale where the large ring on the Titrator meets the barrel of the Titrator. This is the amount of dissolved carbon dioxide in parts per million (ppm). If, for example, the large ring is at the 8th tick on the barrel (between the printed 5 and the 10), there is 8 ppm of carbon dioxide dissolved in the water sample.
If you had to refill the Titrator with the Carbon Dioxide reagent solution, don't forget to add that amount to get your final measurement.
Step 14. With the water running in the sink, pour the contents of the titration tube down the drain and rinse out the Titrator.
Step 15. Repeat steps 4 through 14 TWO more times, so that your group obtains a total of THREE dissolved carbon dioxide measurements for your water sample. Average these three measurements by adding them together and dividing by three. Write your average dissolved carbon dioxide measurement in ppm on the front board and don't forget to copy all the results to your lab worksheets.
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