HOME＞Experiments＞For Kitchen＞EH011 Water Purification
When an acidic aqueous solution containing iron ions becomes alkaline, a colloid called “iron(III) hydroxide” is formed. Let’s observe this process using an aqueous solution of iron(III) chloride, known as “corrosion liquid,” and baking soda.
This experiment should be conducted under the supervision of a guardian.
Wear gloves during the experiment to prevent the aqueous solution from coming into contact with your skin. In case it does, wash it off immediately with water.
If the solution comes in contact with clothing in large amounts, remove the clothing right away, sprinkle baking soda on it to neutralize, and then rinse it off.
Since the solution has the potential to corrode metals, avoid using metal objects. Also, make sure to follow the instructions for “cleaning” carefully.
Requires
equipments
・large plastic cup×5
・marker
・ｍeasuring cup (200 mL or more)
・scale
・gloves (other than cloth)
reagents
・iron(III) chloride (aq)
・baking soda
Preparation
Lay down cardboard or a blue tarp beforehand to prevent the desk or floor from getting dirty.
Methods
1.
Measure out 20 mL of the corrosion liquid and dilute it with water to a total volume of 200 mL.
2.
Pour 40 mL of the aqueous solution from step 1 into each of the five plastic cups.
3.
Add 1 g to 5 g of baking soda in 1 g increments.
*Do not look directly down into the cups from above at this time.
4.
After leaving the cups for one hour, what do you think will happen to the aqueous solution in the cups?
Clearing
Add baking soda to all the cups until no more bubbles are produced. Then, filter the solution using a plastic bottle and kitchen paper. For the remaining corrosion liquid, add baking soda in the same way and filter it. Once filtration is complete, dispose of the filtered liquid in the sink and throw the plastic bottle with the kitchen paper into the burnable trash.
Principle
When an acidic aqueous solution containing iron ions becomes alkaline, a colloid called “iron hydroxide” is formed. This colloid adheres to the surface of undissolved baking soda, accumulating at the bottom, while the water at the top becomes colorless. This phenomenon can sometimes be observed with substances other than baking soda (the photo shows an example with calcium carbonate).
Now, in the five cups, there are some with colored water and others with colorless water. Do they each contain iron ions? Let’s use a salicylic acid glycol patch to check.