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The breathalyzer test, formerly used by law-enforcement agencies to determine the percentage blood alcohol in suspected DUI cases, is still used in the device FINAL CALL, which is available commercially. The reaction involves the reduction of chromuim(VI) in the orange dichromate ion, Cr2O72- to the green chromium(III) ion, Cr3+ by ethyl alcohol.
8H+ + Cr2O72- (orange) + 3C2H5OH ----> 2Cr3+ (green) + 3C2H4O + 7H2O
FINAL CALL consists of a 10-cm glass tube packed with three bands of silica gel crystals coated with a dilute acidic solution of potassium dichromate to produce a yellow color. A test subject fills a balloon (included with the device) with breath; the filled balloon is attached to the end of the glass tube to allow the sampled breath to flow through the tube for 60 seconds. When ethyl alcohol vapor makes contact with the yellow-coated crystals, the color changes from yellow to green. The number of bands which change color and the intensity of the color indicate the relative amount of alcohol in the breath. To simulate the use of a FINAL CALL device, a few drops of ethyl alcohol are carefully placed in the end of the tube, followed by blowing through the tube.
FINAL CALL is commonly used to monitor patients at alcohol-rehabilitation centers and in other situations where zero tolerance conditions exist (e.g., legal confinement and probation status).
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