Different chemicals react differently with other chemicals and may produce color. A chemical will always react with another chemical the same way each time provided that the conditions are the same. This can be used to properly identify what substances are in a certain chemical just by the color change that occurs during the reaction.
Using a pipette I placed 5 milliliters of solution A into a test tube. Then I placed 5 drops of IKI into the test tube with solution A and noted any color changes. For the control I placed 5 milliliters of water into another test tube and put 5 drops of IKI into it and noted any color changes. After cleaning out both test tubes I was ready for the next test. Placing 5 milliliters of solution A into a test tube and 5 milliliters of water into another test tube. I proceeded to put 1 milliliter of Benedict´s solution into the solution A test tube and the test tube containing water. Since this chemical reactant needed to be heated I placed both test tubes in a beaker of boiling water for one minute. After one minute I retrieved the test tubes and noted any color changes. For the next test I cleaned both test tubes and put 5 milliliter of solution A into one test tube and water into another. Then with a pipette I placed one milliliter of Biuret´s solution into the test tube with solution A and I put another milliliter of Biuret´s solution into the test tube containing water, noting and color changes. I repeated this process for each of the other two unknown solutions.
The unknown solutions reacted with the chemical reactants and produced either no color change or a color change. Since some of the solutions and chemicals already had some color to them, I had to set up a control and use my judgement as to whether there was any actual color change. Each of the chemical reactants responded to a certain substance in the solution and changed color. IKI would react with starch and turn a blue-black, Benedict´s solution would react with glucose to turn a muddy orange, and Biuret´s solution would react with protein and turn violet.
| Test Results | ||||
|---|---|---|---|---|
| Chemical Reactants | IKI | Benedict´s Solution | Biuret´s Solution | |
| Unknown Solutions | A | Negative | Positive | Negative |
| B | Negative | Negative | Positive | |
| C | Positive | Negative | Negative | |
This process is a fast and effective way to determine what substances make up a solution. There are many different chemical reactants available to use in the process of identifying substances. There are certain limitations, however; some of these chemicals have color and so does the reactants. If you use a control you can increase your ability to distinguish positive results from the negative results, but you can not always be sure that you are correct.
