Breathalyzer
- Page ID
- 141678
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Show Demo (D17)
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Required Training |
Required PPE |
|---|---|
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UC Lab Safety Fundamentals |
Lab coat, safety glasses/goggles, nitrile gloves |
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Performers Required: 2 |
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Equipment |
Chemicals |
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Ring Stand with two clamps |
Potassium Dichromate (K2Cr2O7) |
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GC Vials (or other small vials) with septum |
Sulfuric Acid (H2SO4) |
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Needles (1 for ventilation, 1 for bubbling) |
Beverage with minimum 2% alcohol (Should not be stored in lab or around lab chemicals) |
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Balloon |
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Procedure:
1.) In the fumehood put a fraction of a disposable scoopula tip (approx. > 1 mg) worth of potassium dichromate into a small vial. Place a few drops of HCl into the vial, enough to cover the surface of the dichromate crystals. Cap the vial with a septum then repeat to make a total of two vials. The vial can now be taken out of the fumehood, but dispose of gloves, scoopula and anything used when handling dichromate into an appropriately labeled waste container.
2.) Clamp the vial onto a ring stand with one vial above the other. Place one ventilation needle into each vial.
3.) Have one person blow up a balloon as a control. Place the longer, larger gauge needle into the bottom vial so that the point of the needle is inside the dichromate-sulfuric solution. Attached the balloon to the needle and create an air-tight seal with your hands. Push on the balloon to force the exhaled air into the vial. There should be no color change.
4.) Have one person swig a beverage or mouthwash with at least 2% ethanol content. Repeat the above step with different results, the solution should turn a dark green color.
Clean-up: Everything should be disposed of into appropriately labeled waste containers (WASTe). The entire GC vial should go into container for solid waste. All disposable gloves, plastic, balloons, scoopulas should go into a plastic bag. The needles should be disposed of in a sharps container.
Hazards: Potassium dichromate is a carcinogen, strong oxidizer and both toxic and chronically toxic. It should never be handled outside of the fumehood and everything used when handling the loose powder should be disposed of as hazardous waste. There should be a designated area for storing chromate waste that is kept free of flammable materials. When swigging the ethanol solution, the individual should keep at least 10 feet away from the demo.
Principle: The breathalyzer is a redox reaction. When the potassium dichormate reacts with ethanol it loses an oxygen atom (gets reduced), going from the orange dichromate to the green chromium sulfate. At the same time dichromate is being reduced, ethanol gains an oxygen atom (gets oxidized), forming acetic acid. The sulfuric acid helps to remove the ethanol from the exhaled air into the test solution and also provides the necessary acidic conditions.
