Final answer:
The Breathalyzer test measures a person's BAC by oxidizing ethanol in the breath, which causes the testing solution to change color. A BAC of 0.08% is typically the legal limit for intoxication in the US. If a breath sample cannot be provided, blood or urine samples may be used instead.
Step-by-step explanation:
When a person consumes alcoholic beverages, it can impair their ability to perform tasks that require skill and judgment, such as driving. This is why in many jurisdictions, it is illegal to drive with a blood alcohol concentration (BAC) above a certain limit. In the United States, a BAC of 0.08% is typically considered the legal threshold for being intoxicated. Breathalyzer devices are used to measure a person's BAC indirectly by analyzing their breath.
The key reaction in a Breathalyzer involves the oxidation of ethanol by the dichromate ion, which results in a color change from yellow-orange to green in the test solution. The intensity of the green color corresponds to the amount of ethanol present, allowing an estimation of the BAC.
In cases where an individual cannot provide a breath sample, other methods such as drawing blood samples for analysis may be used. Plasma is often obtained from these samples and can be quenched with methanol to preserve it for testing. Urine samples might also be taken for drug and alcohol analysis, often requiring no preparation before the test.