1. Add 2-3 ml of 6 M HNO3 into the sample solution.
2. Then add dropwise 0.2 M AgNO3 to the sample solution with good stirring until AgCl is observed to completely coagulate.
3. Introduce additional 3 ml of 0.2 M AgNO3.
4. Heat the mixture solution to boil.
5. Let the solution stand in the dark until the precipitate coagulates (at least 15 min.).
6. While waiting, prepare the vacuum filtration equipments using a Buchner funnel.
7. After stand for 15 min., filter the precipitate by decanting the supernatant liquid onto the filter paper using suction.
8. Wash the remaining precipitate in the beaker for 3 times with 0.12 M HNO3 and decant the washings onto the filter paper.
9. Transfer the precipitate to the filter paper. Remove the precipitate from the beaker by using water from a wash bottle.
10. Wash the precipitate on the filter with 0.12 M HNO3, 3 times.
11. Place the filter paper on a watch glass.
12. Dry it in the oven (110 C).
13. Allow the precipitate to be cool to room temperature and weigh after it is dried.
14. Calculate the percentage of Cl- in the sample.
15. Calculate the percentage of error