How to distinguish various fertilizers using four tests
name: Tests for mineral fertilizers with various reagents
Wear eye protection and lab gloves.
Avoid contact of sodium hydroxide solutions and concentrated sulfuric acid with skin.
Don't inhale nitrogen dioxide, formed in the reaction of sodium nitrate, concentrated sulfuric acid and copper.
Always follow general safety
recommendations. Please note that conducting chemistry
experiments you must comply with the relevant legal procedures in
SO42- + BaCl2 → BaSO4↓+ 2Cl-
NH4+ + NaOH → NH3 ↑ +Na+ + H2O
2NO3- + 2H2SO4 + Cu → 2NO2 ↑ + CuSO4 + SO42- + 2H2O
PO43- + 3AgNO3 → Ag3PO4↓ + 3NO3-
AgNO3 + Cl- → AgCl ↓ + NO3-
- Dissolve some of each fertilizer in water and pour the obtained solutions into unlabeled flasks. The purpose of this experiment is to determine what fertilizer is in which flask.
- For tests prepare water solutions of barium chloride, sodium hydroxide and silver nitrate.
- Pour samples of the first fertilizer solution into four test-tubes.
- Add some concentrated sulfuric acid and a piece of copper into the first test-tube.
- Add the barium chloride solution into the second test-tube.
- Pour the sodium hydroxide solution into the third test-tube and heat it with a burner. Put indicator paper to the opening of the test-tube.
- Add the silver nitrate solution into the fourth test-tube.
- Do steps 3-7 with other fertilizer solutions.
Ammonium sulfate forms a white precipitate with barium chloride. In the reaction of ammonium sulfate and sodium hydroxide under heating ammonium gas is formed. It can be detected with wet indicator paper, which turns blue.
Copper and concentrated sulfuric acid react with nitrate ions and form brown nitrogen dioxide gas. This reaction proceeds with sodium nitrate.
Superphosphate reacts with silver nitrate and forms a yellow precipitate of silver phosphate.
Sylvinite consists of sodium and potassium chlorides. Silver ions (from the silver nitrate solution) form with chloride ions a white precipitate.
These characteristic reactions allow distinguishing each of fertilizers.