A chemical test can be defined as a quantitative or qualitative procedure that has been designed in order to accomplish one of the following:
- Identify a specific chemical compound which is present in a given analyte
- Quantify the amount of a specific chemical compound in a given analyte
- Characterize the presence of a specific chemical compound in a given analyte
Some important chemical tests in the field of analytical chemistry such as the ninhydrin test, Molisch’s test, and Benedict’s test are described in this article.
Ninhydrin Test
The ninhydrin test is a specific chemical test which can be employed to check for the presence of alpha-amino acids or amines in a given analyte. This test involves the use of ninhydrin (also known as 2,2-dihydroxyindane-1,3-dione, denoted by the chemical formula C9H6O4) to trigger the formation of a deep blue coloured compound in the analyte (if it contains amines or alpha-amino acids).
Molisch’s Test
Molisch’s test is a chemical test which is named after the Czech-Austrian botanist Hans Molisch. It can be used to check for the presence of carbohydrates in a given analyte. It involves the dehydration of the carbohydrate with the help of hydrochloric acid or sulfuric acid that results in the formation of an aldehyde. This aldehyde is made to undergo condensation with two phenol molecules, forming a violet coloured ring in the process. This chemical test has a fairly simple procedure – a few drops of Molisch’s reagent are mixed with the test solution in a test tube before the addition of concentrated sulfuric acid to the mixture.
Benedict’s Test
Benedict’s test is a chemical test that involves the use of Benedict’s solution (a complex mixture of sodium citrate, sodium carbonate, and the pentahydrate of copper sulfate, also referred to as Benedict’s qualitative solution) to check for the presence of reducing sugars in a given analyte. If the analyte does contain reducing sugars, it forms a brick-red precipitate when exposed to Benedict’s reagent.
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