The Beer- Lambert Law, the Arrhenius Equation and the integrated first order rate equation were the three interrelated equations used in this experiment.
Beer Lambert law: A= E.c.l, where A is the absorbance, E is the molar extinction coefficient, c is the concentration and l is the path length. From the equation it can be seen that absorbance is directionally proportional to concentration. Being aware of this in the beginning is an advantage. Errors in results can be detected and rectified if this law is not being followed early on in results.
Integrated first order rate equation: k’t = Ln( [Dye]0 / [Dye]t ) where k’ is the rate, t is the time, [Dye]0 is the concentration of malachite green at t=0 and [Dye]t is the concentration of malachite green at time t.
The Beer Lambert law and the integrated first order rate equation are related. This is only if the Beer Lambert law is followed, i.e. Absorbance is directly proportional to concentration. These two equations give a more simple equation:
k’t = Ln( [A]0 /[A]t). Where [Dye] from Integrated first order rate equation is now [A] as the Beer Lambert law has been followed.
Malachite green is the main reagent used in this experiment. It is blue/green in colour. Its colour gradually disappears throughout the experiment indicating it’s being used up and Carbinol is formed. The product Carbinol is a clear colour. Malachite green has two important resonance forms, shown below.
Malachite green has many uses in industry. It also has health risks:
It is widely used as a dye. “Leuco-malachite green (LMG) is used as a detection method for latent blood in forensic science. Aquatic animals metabolize malachite green to its leuco form (4). “In 1992 Canadian authorities determined that eating fish contaminated with malachite green posed a significant health risk” (5) “The substance has been banned in the United States since 1983 in food-related applications. It is banned in the UK also.” (6)