This research was conducted to test the feasibility of cassava (Manihot esculenta) leaf extracts as acid-base indicator. There is a growing need to utilize indigenous resources as materials in the laboratory. The results of this study can be a basis for use of cassava, a locally available plant in the country, as an important aid in chemistry.
The crude leaf extracts obtained from homogenized cassava leaves were added to chemical compounds with varying strengths in acidity and basicity (strong and weak acids and bases). Color changes were observed and recorded after the application of the extracts. A pH meter was used to determine the ability of the extract to promote color transformation in the different solutions of acids and bases. It was found that extracts from the said plant have the ability to indicate the basicity of a particular chemical substance.
Chemical compounds can be classified as acidic, basic, or neutral substances based on several conditions. One factor considered is the color reaction which can be observed through the use of indicators. An indicator is a substance that changes color, depending on whether it is placed in an acidic solution or basic solution. Acid-base indicators are dyes that are themselves weak acids and weak bases. One indicator that almost everyone associates with acids and bases is the litmus, which has the ability to change color in response to an acid or base. Phenolphthalein is another common indicator used by beginners in Chemistry because its color change is very obvious, making it easy to use. There are many other indicators that change color at different pH levels, and so are useful for different purposes. Another commonly used indicator, the pH paper, contains a mixture of different indicators that change colors at different pH levels. For convenience, many laboratories opt to use pH meters or pH pens.
Many plant pigments found in nature can be used quite effectively as acid-base indicators. The dyes in blueberries and red cabbages belong to a family of molecules called anthocyanins. This family of molecules is responsible for the color found in radishes, eggplants, and numerous flowers. The anthocyanins are water-soluble and have colors that are dependent upon the pH of the reacting solution. In this study, the researcher tested the feasibility of Cassava leaf extract as an acid-base indicator. Cassava leaves contain hydrocyanic acid, which is a weak acid.
Materials & Equipment
Petrucci, R.H. and Hardwood W.S. 1997. General Chemistry: Principles and Modern Applications.7th ed. New Jersey, Prentice Hall Inc.
Further clarification of the procedures and results should be directed to the researchers and adviser.
Jamela R. Vedad
Ms. Marie Christine W. Merca
Philippine Science High School
Bicol Region Campus