Experimental evaluation of different sulphuric acid concentrations in chemical detection of ethanol
Htun Nay Aung.
Date of Issue2009
School of Mechanical and Aerospace Engineering
Detection of blood alcohol level has been routinely done in road traffic practice and forensic toxicology. Many technologies and methods have been applied in estimating blood alcohol level. Infrared, electrochemical cell, gas chromatography, etc have been developed to assist in blood alcohol measurement, but chemical method is still relevant and has been used in many alcohol detector devices because of its simplicity, low cost and high sensitivity. As ethanol is a strong reducing agent, it can reduce some color compound producing an obvious color change. This advantage is the basis of many alcohol detector devices that are based on chemical reaction. The most commonly used chemical reaction is oxidation of ethanol by potassium dichromate in the presence of sulphuric acid solution. This chemical reaction is currently used in breathalyzer which measures blood alcohol level through the breath. Sulphuric acid is the major chemical in this reaction as no color changing will take place without an acid medium. Variations in its concentration and molar ratios greatly influence the rate of chemical reaction as well as the rate of color change. The greater the concentration is, the faster the reaction. However the intimate relationship is complicated. Moreover, its high corrosivity becomes a major problem when fabricated into a device. In this dissertation, sulphuric acid was targeted to determine the effect of its different concentrations and molar ratios on the color changing reaction. In addition to this, effects of potassium dichromate and ethanol on rate of color change were examined, and different methods of alcohol detection were discussed to evaluate the differences between them.
Nanyang Technological University