2. Caution: many chemicals are corrosive. You should wear gloves and be sure your skin is not exposed. Discard the gloves after use, and wash your hands. Chemical exposure may result in an itchy sensation. If you have any sensation of itching, burning, or tingling, thoroughly flush the area with water. Continue flushing until several minutes after the sensation has subsided. Inform your lab instructor. 3. Never raise containers of solution, especially corrosive solutions, to eye level or above. In particular, avoid this when filling a buret. 4. Never weigh chemicals directly on a balance pan. Use weighing paper, glassware, or other secondary container. 5. Waste solutions and solids from this experiment should be disposed of in the waste containers designated by your lab instructor. PROCEDURE Part A: Preparing to take absorbance readings, preparing Kool-Aid® solutions 1. Plug-in and turn on the Vernier LabQuest, plug the colorimeter into the first slot on the LabQuest, and allow them to warm up (at least 10 minutes) while preparing your solutions. The instructor should also warm up a LabQuest with the spectrophotometer attachment (which uses one of the USB ports) for use by the entire class, in groups. 2. Your instructor may want to demonstrate how to find a matching set of cuvets. One cuvet will serve as the BLANK (to set “zero” absorbance at each wavelength), while the other will be used to determine the absorbance of each solution at each wavelength. Ensure that your team has an optically-matched pair of disposable cuvets, as follows: (a) Set the colorimeter to the desired wavelength using the <> keys above CAL. (b) Three-quarters fill a cuvet with deionized water (DI), wipe the outside of the cuvet with a lint-free cloth, and inspect to ensure that there aren’t air bubbles or streaks. Gently tapping the bottom of the cuvet on the bench top may dislodge an air bubble. (c) Open the thumb latch below, “Vernier,” place the cuvet in the colorimeter with a clear side aligned with the white arrow within, and snap the door closed. (d) Press the calibrate button once, firmly, wait for the red light to stop blinking, and confirm that the absorbance reading is 0.000. (e) Place the other cuvet, ¾-filled with DI water as in 2.(b) above, into the calorimeter. Its reading should also be 0.000. (f) Because less absorbance than the “blank” isn’t displayed as a negative value on the colorimeter, again press calibrate, wait for the red light to stop blinking, and confirm that the reading is, yet again, 0.000. (g) Replace the second cuvet in the colorimeter with the original one. Do not press calibrate this time! The reading should again be 0.000. If so, you have a matched set of cuvets. If not, recheck both cuvets for air bubbles, fingerprints, and streaks, fix the problem, or choose two other cuvets, and repeat steps 2.(a)-(g).
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