Optimizing rate of colour change of a breathalyzer

• Main Author: Lim, Yi Siong.
• Other Authors: Lim Chu Sing
• Format: Final Year Project
• Language: English
• Published: 2010
• Subjects: DRNTU::Engineering::Mechanical engineering::Control engineering
• Online Access: http://hdl.handle.net/10356/40558
• Institution: Nanyang Technological University

The principle of the measurement of a breathalyzer is based on the following chemical reaction: During this reaction, the reddish-orange dichromate ion changes colour to green chromium ion when it reacts with alcohol. The degree of the colour change is directly related to the level of alcohol used in this project, which is 35.4μL in volume. This project aims to investiagte and obtain an optimum value of chemical concentrations and molar ratios for an effective and fast rate of colour change with the help of Design of Experiment (DOE) principles. Experiments are conducted with a consistent expansion factor of 20 for all volumes. From the analysis of the observed results, it was found that the best concentrations to use are 0.4M and 5M for potassium dichromate and sulfuric acid respectively. In addition, it was also found that the best combination of low molar ratio of 0.5 for potassium dichromate and high molar ratio of 45 for sulfuric acid is excellent for achieving a fast rate of colour change.