Chemical Analysis

TESTING FOR IONS

NEGATIVE IONS:

The flame test - A cleaned, moistened flame test wire is dipped into a solid sample of the compound. It is then put into the edge of a blue Bunsen flame. The flame colour produced indicates which alkali metal ion is present in the compound.

• Lithium (Li+) - Turns crimson when put into flame
• Sodium (Na+) - Turns yellow when put into flame
• Potassium (K+) - Turns lilac when put into a flame
• Calcium (Ca2+) - Turns orange when put into a flame
• Copper (Cu2+) - Turns green when put into a flame

POSITIVE IONS:
Halide ions in solutions are detected using silver nitrate solutions. The test solution is acidified using a few drops of dilute nitric acid, and then a few drops of silver nitrate solution are added. Different coloured silver halide precipitates form, depending on the halide ions present:

• Chloride (Cl-) ions - white precipitate
• Bromide (Br-) ions - cream precipitate
• Iodide ions (I-) - yellow precipitate 

NEGATIVE IONS:

The flame test - A cleaned, moistened flame test wire is dipped into a solid sample of the compound. It is then put into the edge of a blue Bunsen flame. The flame colour produced indicates which alkali metal ion is present in the compound.

• Lithium (Li+) - Turns crimson when put into flame
• Sodium (Na+) - Turns yellow when put into flame
• Potassium (K+) - Turns lilac when put into a flame
• Calcium (Ca2+) - Turns orange when put into a flame
• Copper (Cu2+) - Turns green when put into a flame

POSITIVE IONS:
Halide ions in solutions are detected using silver nitrate solutions. The test solution is acidified using a few drops of dilute nitric acid, and then a few drops of silver nitrate solution are added. Different coloured silver halide precipitates form, depending on the halide ions present:

• Chloride (Cl-) ions - white precipitate
• Bromide (Br-) ions - cream precipitate
• Iodide ions (I-) - yellow precipitate 

NEGATIVE IONS:

The flame test - A cleaned, moistened flame test wire is dipped into a solid sample of the compound. It is then put into the edge of a blue Bunsen flame. The flame colour produced indicates which alkali metal ion is present in the compound.

• Lithium (Li+) - Turns crimson when put into flame
• Sodium (Na+) - Turns yellow when put into flame
• Potassium (K+) - Turns lilac when put into a flame
• Calcium (Ca2+) - Turns orange when put into a flame
• Copper (Cu2+) - Turns green when put into a flame

POSITIVE IONS:
Halide ions in solutions are detected using silver nitrate solutions. The test solution is acidified using a few drops of dilute nitric acid, and then a few drops of silver nitrate solution are added. Different coloured silver halide precipitates form, depending on the halide ions present:

• Chloride (Cl-) ions - white precipitate
• Bromide (Br-) ions - cream precipitate
• Iodide ions (I-) - yellow precipitate