Solution can test for a variety of substances, depending on the type of solution used. Some common solutions used for testing include:

- Benedict's solution: Tests for the presence of reducing sugars, such as glucose.

- Fehling's solution: Also tests for the presence of reducing sugars.

- Biuret solution: Tests for the presence of proteins.

- Ninhydrin solution: Tests for the presence of amino acids.

- Phenolphthalein solution: Tests for the presence of alkalis and acids.

- Litmus solution: Also tests for the presence of alkalis and acids.

- Nessler's solution: Tests for the presence of ammonia.

- Silver nitrate solution: Tests for the presence of chloride ions.

- Potassium iodide solution: Tests for the presence of starch.

These are just a few examples of the many solutions that can be used for testing different substances. The specific solution used will depend on the substance being tested for.