Carbonate is a salt of carbonic acid, which is an organic compound. It can also refer to carbon dioxide mixed in water containing carbonic acid. Carbonate also refers to the chemical compounds derived from reactions of oxoacid and alcohol groups, more commonly known as esters. Carbonate also refers to carbonation which occurs when carbon dioxide is dissolved in an aqueous solution under high pressure. There are different tests that can be performed to test for carbonate as an ion and for carbonate hardness. Carbonate hardness refers to the ability of water to neutralise an acid, or its ability to act as a buffer.
Rinse a small test tube with distilled water. Take a small amount of baking soda, about the size of a pea, and place it in the test tube.
Add one to two drops of 18 molar (M) sulphuric acid. Make sure you use gloves and a fume hood to handle this chemical. This acid is a strong acid. Add a drop of barium hydroxide solution to the inside side of the test tube. This will cause carbon dioxide bubbles to form, confirming the presence of the carbonate ion.
Repeat the experiment above using vinegar instead of sulphuric acid. Vinegar will also release carbon dioxide gas to confirm the presence of carbonate ions since vinegar contains acetic acid.
Test for carbonate hardness using carbonate hardness analytical test strips. You can apply the test strips to samples of drinking water, mineral water, spring water, well water, industrial water, boiler water, cooling water and even aquarium water.
Place your sample of water into a beaker. Take one test strip and place it into the beaker full of your water sample. Make sure that the test strip is immersed past the reaction zone of the test strip for one second. Remove the strip from the water and shake any water from the strip.
Look at the colour that appears in the reaction zone of the test strip. Match the colour to the colour fields of the label of the strips. Decide which colour compares to the reaction zone and record the results of the given concentration value. Sometimes, the colours may not match exactly. In this case, estimate the closest colour.
Remember to wear gloves when handling acids. In addition, make sure you pour chemicals under a laboratory fume hood.
Tips and warnings
- Remember to wear gloves when handling acids. In addition, make sure you pour chemicals under a laboratory fume hood.
Things you need
- Test tube
- Distilled water
- Baking soda
- 18 molar sulphuric acid
- Fume hood
- Barium hydroxide solution
- Carbonate hardness test strips