Types of Bleach

• Bleach is used to remove stains from clothing and make it look whiter or brighter. There are two types of bleach: oxygen-releasing bleach and chlorine-releasing bleach. Chlorine bleaches work best on clothing that is already white and are often used to remove stains from clothing. Oxygen bleaches are considered to be color-safe; according to the Charleston College, oxygen reacts with the "color centers" in dyes to make them appear brighter without eliminating the eye's ability to detect the color altogether.
  
  

Purpose of Titration

• The purpose of titrating bleach is to determine the concentration of the oxidizing agent within the bleach. The oxidizing agent is a compound that releases either oxygen or chlorine when interacting with stains or colored dye. The stronger the concentration, the whiter the bleach will make the clothing.
  
  

Materials for Titration

• The procedure for titrating bleach in an honors chemistry course at Charleston College requires a plastic beaker, analytic balance, 5 mL of bleach, distilled water, a buret, and a volumetric flask to prepare the bleach solution. You will need another buret, a standard acidic solution, an Erlenmeyer flask, a pipette, an indicator such as solid potassium iodine, a stir bar and magnetic stirrer, and starch in order to perform the titration itself.
  
  

Preparing Bleach for Titration

• Charleston College recommends diluting bleach prior to titration in order to make it safer and easier to use. Pure bleach is highly reactive and can be dangerous to exposed skin.
  
  Begin by weighing the empty plastic beaker. As you add bleach to the beaker, subtract the mass of the empty beaker to determine the mass of the bleach. You should add about 5 mL of bleach; the mass of the bleach should be approximately 4 grams. Record the exact mass of the bleach.
  
  Rinse a buret with distilled water. Draw the bleach into the buret a little at a time and transfer it to a 100 mL volumetric flask. Add distilled water to the beaker and carefully pour into the flask. Repeat several times, until the flask is filled to the mark. Put a stopper in the flask and shake it to mix the contents.
  
  

Titrating the Bleach

• Rinse another buret with a standard solution and discard the solution. Fill the buret with the solution and record its volume.
  
  Use the pipette to transfer 25 mL of the diluted bleach into a 125 mL Erlenmeyer flask. Add 50 mL of distilled water, 2 grams of potassium iodine, and 10 mL of .5 M sulfuric acid. Add a stir bar and stir with a magnetic stirrer. Titrate the solution with your standard solution until it turns pale yellow. At this point, you should add 2 percent starch solution, which will turn the solution dark. Continue titrating until the dark color disappears, indicating a chemical reaction has taken place. Record the amount of titrant used.
  
  

Calculating the Concentration

• After titration is complete, you can calculate the mass of the oxidizing agent in the bleach by multiplying the mass found in the titrated sample by the ratio of the volume of diluted bleach to the volume of the sample titrated. Once you have determined this mass, you can calculate the percentage of oxidizing agent in the bleach by dividing this mass by the mass of the bleach and multiplying by 100.