Micro-chemical test for chloride
Author: Christine Bläuer
back to Micro-chemical testing
More information on the necessary equipment and materials see the Micro-chemistry article.
The drop to be tested is acidified with a minimum of diluted (2M) nitric acid and then a drop of silver nitrate 1% w/v solution is added. If Cl- is present a white precipitate of AgCl will form instantly. After exposure to light this will turn brown with time(image 1). Detection limit for Cl- = 0.05µg
If sulfate is present typical silver sulfate crystals can be observed in the test drop.
If in addition to chloride, sodium or potassium are present in the solution, typical isotropic cubes of NaCl or isotropic rectangular, cruciform structures of KCl will form near the edge of the drop of the pure salt solution.
Ions that may inhibit the test or affect its sensitivity:
Iodide and bromide also produce white precipitates with silver nitrate solution, but these ions are not likely to be present in salt efflorescence from buildings.