Fluorine is not directly detected in a sodium extract using AgNO3 solution. Silver nitrate (AgNO3) is commonly used to test for the presence of chloride (Cl-) ions in a solution by forming a white precipitate of silver chloride (AgCl). Fluoride ions (F-) do not react with AgNO3 in a similar manner to produce a visible precipitate.

While fluorine may be present in a sodium extract, the AgNO3 test specifically targets chloride ions. To detect fluoride ions, different analytical methods or reagents specific to fluoride detection would need to be employed.