The Blood:Breath Partition Ratio. In our previous study of Henry's Law we learned when a volatile chemical (ethanol, for instance) is dissolved in a liquid (blood) and brought into contact with a closed air space (the lungs), an equilibrium is formed and there exists a fixed ratio between the concentration of ethanol in the air space and the concentration in the liquid.
(at a given temperature and pressure) In a closed system the amount of ethanol in the airspace above the liquid is proportional to the amount of ethanol in the liquid. We also learned Henry's Law can only provide an approximation of the ethanol in human breath since the law applies to a closed system at a given temperature and pressure. More On Henry's Law. Earlier this week I posted here about the problems with the Intoxilyzer 5000.
This machine is used nationwide by law enforcement to obtain breath samples from DWI suspects and to analyze the sample for ethanol concentration. More on Henry's Law. The reference sample device on the Intoxilyzer is designed to deliver a sample of vapor containing a known or predicted amount of ethyl alcohol (ethanol). The reference sample device is supposedly used to verify the accuracy and calibration of the machine. Biological Evidence/ Breath Tests for Blood Alcohol Determination: Partition Ratio.