“PLANTS AS pH INDICATORS”

A Research Proposal

Presented to

Mindanao State University

Tawi-Tawi College of Technology and Oceanography

SCIENCE HIGH SCHOOL

Bongao, Tawi-Tawi

In Partial Fulfillment for the

Requirements for Graduation

MORENA E. DAIL

PARAMISULI S. AMING

SHEA ISSEY M. ANUDDIN

ALNEEHADA BIANCA A. KAMSA

September 2012

TABLE OF CONTENTS

Title Page

Table of Contents

CHAPTER I – INTRODUCTION

Background of the Study

Statement of the Problem

Significance of the Study

Hypothesis

Scope and Delimitation of the Study

Operational Definition of Terms

CHAPTER II – REVIEW OF RELATED LITERATURE

CHAPTER III – MATERIALS AND METHODS

Research Method

Materials

Equipments/Apparatus

Procedure

Preparation of pH Indicators

Collection and Preparation of Samples

Extraction of Coloring Matter/pH Indicator

Testing Different Items for pH level/Determination of the Color Changes of Different Plants when used as Indicator

Comparing Color Changes

Flow Chart of the Procedures

REFERENCES

CHAPTER I

INTRODUCTION

Background of the Study

pH is a measurement that will denote the level of chemical activity of hydrogen in a

given solution. The lowest possible pH rating is a pure acid at 0, and the highest possible pH

rating is a pure acid at 0, and the highest possible pH is at 14, which is a pure base.

(Litherland, 2009)

Commercial pH indicators are hard to find. Though they are cheap, many people have

trouble finding them. People really don’t have to use them, as nature provides us with pH

indicators in the form of plant pigments known as anthocyanins, which change color over

different pH ranges, depending on source. The plants that have anthocyanins are called

natural pH indicator or plant pH indicators which are cheaper and easier to find than the

commercial ones.

Methods of determining the pH of a solution can be expensive as well as indeed

cumbersome to use. Natural indicators, on the other hand, are relatively inexpensive by

comparison. This cheap cost is what makes them ideal for situations where a large number of

tests will have to be done. Some examples of this could be in a high school or college

chemistry lab. There are schools that lack pH indicators, particularly in some remote areas.

One such is the MSU TCTO Science High School. Sometimes, it is not available in a

specific area. Some are forced to go to other places just to acquire some samples. That is why

this study will focus on the production of the available pH indicator out of different plants as

alternative for the commercial pH indicators.

In recent years, the demand for measuring pH has grown dramatically. This includes

agricultural, wastewater, pharmaceutical, and educational applications, critical measurement

in industries, testing a sample against a legal requirement, and is also of outstanding

importance in water and environmental analysis.

Since almost any highly colored fruits, vegetables, or plants contain anthocyanin, then

it is hypothesized that pH indicators can possibly be produced out of different plants and that

they can be used to identify the color changes of different household and laboratory

chemicals.

Moreover, there has been a growing need to utilize indigenous resources as materials

in the laboratory. The results of this study can be a basis for use of plants that are locally

available in the province and in the country, as a cheaper, alternative, and important aid in

chemistry.

Statement of the Problem/Objectives

This study aims to produce pH indicators out of different plants. Specifically, it will

seek to answer the following questions:

1. What are the colors produced by the household chemicals and the laboratory

chemicals after the addition of each plant extract?

2. What are the colors produced by the laboratory chemicals after the addition of

each plant extract?

Significance of the Study

This study will focus mainly in the production of pH indicators using different plants.

Though there are many commercial indicators in our modern world today, there is still a

possibility that a time of scarcity of indicators may occur. If time of scarcity happens, one

knows how to easily make an indicator out of natural materials.

Scope and Delimitation of the Study

This study will focus on the production of pH indicator out of different plants.

Aluminum sulfate will be used as an additive that will be applied on each test. The household

chemicals that will be used in this study are muriatic acid, calamansi extract, feminine wash,

vinegar, shampoo, distilled water, monosodium glutamate, bath soap and detergent bar

powder solution and household chemicals such as HNO3, H2SO4, CuSO4, K2Cr2O7,

Cr(NO2)3, Pb(NO3)2, Ammonium Hydroxide, Ca(OH)2, and NaOH. The study will be

conducted in the MSU Science High School Laboratory Room.

A total of ten (10) indicators will be used. Eight (8) of which are plant indicators:

Red Cabbage, Purple Heart Plant leaves, Areca Nut, Eggplant, Muntingia, Red Onion,

Malabar Nightshade, and Mangosteen; the other two are synthetic: phenolphthalein and

litmus paper.

Operational Definition of Terms

For the purpose of clarification, the following key terms are hereby operationally

defined.

Acid – a compound usually having a sour taste and capable of neutralizing alkalis and

reddening blue litmus paper

Anthocyanin – are water-soluble vacuolar pigments that may appear red, purple, or blue

according to the pH. It may occur in tissues of most ph indicating plants, including

leaves, stems, roots, flowers, and fruits

Base – it is a compound usually having a slight bitter taste and capable of turning blue a red

litmus paper

Strong Acid/Base – an acid or base that completely dissociates into ions

Weak Acid/Base – an acid or base that only partially ionizes in solution

pH – measure of the acidity of a substance; a ph of less than 7 is acidic (lower number=more

acidic) and a pH of greater than 7 is basic, in general the scale goes from 1 (very

acidic) to 14 (very basic)

pH indicator – substances that changes color depending on the pH of the solution it is

mixed with. Indicators are often made from plant extracts

plant indicators – plants that can be used as an indicator. The plant extracts are usually used

as an indicator

CHAPTER II

REVIEW OF RELATED LITERATURE

This chapter presents the review of related literature that provides information about

“Plants as pH Indicators” which also serves as guidance in the research process, formation

of research problem, hypothesis, and definition of terms.

A pH (potential of Hydrogen) measurement reveals if a solution is acidic or alkaline

(also base or basic). If the solution has an equal amount of acidic and alkaline molecules, the

pH is considered neutral. Very soft water is commonly acidic, while very hard water is

commonly alkaline, though unusual circumstances can result in exceptions. (Kayne, 2003)

pH is defined as the negative logarithm of the hydrogen ion concentration. This

definition of pH was introduced in 1909 by the Danish biochemist Soren Peter Lauritz

Sorensen. The pH value is an expression of the ratio of [H+] to [OH-] (hydroxide ion

concentration). Hence, if the [H+] is greater than [OH-], the solution is acidic. Conversely, if

the [OH-] is greater than the [H+], the solution is basic. At pH of 7, the ratio of [H+] to

[OH-] is equal and, therefore, the solution is neutral. pH is a logarithmic function. A change

of one pH unit represents a 10-fold change in concentration of hydrogen ion. (Kohlmann,

2003)

An indicator is a chemical substance that, by being able to change color, provides

visual evidence of the nature of chemical system in which it is placed. Most indicators are

complicated organic molecules that exists in two different color form (sometimes one form is

colorless) in different chemical environments such as acidic and basic solutions. The most

common acid-base indicator is litmus paper – paper that is treated with a chemical that

appear red in acidic solutions (low pH) and blue in basic solutions (high ph). (Knecht, 1996

quoted by Manulon, 2007)

The most common method to get an idea about the pH of solution is to use a pH

indicator, which is also called an acid-base indicator. An indicator is a large organic molecule

that works somewhat like a “color dye”. Whereas most dyes do not change color with the

amount of acid or base present, there are many molecules, known as acid-base indicators,

which do respond to a change in the hydrogen ion concentration. Most of the indicators are

themselves weak acids. (Ophardt, 2003)

Indicators are complicate organic weak acids or bases with complicated structures.

They are also called acid-base indicators or neutralization indicators. Their conjugate sac

indicators and ions for basic indicator. The ionization of acidic indicator in a solution is

represented by the equilibrium. (Khan et al., 2011)

Indicators work because they are weak acids which, when in solution, exist in

equilibrium with their conjugate base. The acid and its conjugate base each have different

colors, and as the equilibrium shifts from one direction to the other, the color of the indicator

solution changes. Some indicators exhibit only two colors and some exhibit wide range. Each

indicator must be individually studied to determine its behavior as a function of pH. (Malapit,

2010)

Chemists pick selective natural dyes to indicate specific pH levels based on their

color changes. For example, a commonly used acid-base indicator, named Bromthymol Blue,

is yellow in acid and blue in base and intermediate in between at pH 7. Yellow form of

Bromthymol Blue, (acid form HBb) when it donates a proton to OH- ions at higher pH

changes to anion, (base-form, Bb) which is blue. The point at which a color changes from

intermediate to blue gives information on the acid strength of the acid-form, HBb. Chemists

test various indicators for their acid strength and choose an indicator for specific pH levels.

(Withers, 2010)

There are hundreds of different acid-base indicators, many of which can be extracted

from common plants. (Malapit, 2010)

Anthocyanins are water soluble pigments found in many plants. These pigments have several

functions in the plant, and they are also of nutritional interest, because they have been linked

with nutritional benefits such as cancer prevention. People eat anthocyanins everyday, and

many people have a diet rich in these pigments. Depending on pH, anthocyanins can be red,

blue, or violet. The bright red color of an apple is due to the presence of anthocyanins, as is

the rich blue of a blueberry. These pigments can be found in fruit, stems, and leaves, and

their levels may fluctuate. (Smith, 2003)

Anthocyanin is probably the most readily available acid/base indicator; it is the plant

pigment that makes red cabbage purple, cornflowers blue, and poppies red. It changes color

from red in acid solution to purplish to green in mildly alkaline solution to yellow in very

alkaline solution. (Senese, 1997)

Many plant pigments act as acid-base indicators, and one can know appreciate why

some of these pigment molecules behave the way they do. The blue and red pigments of

flowers were isolated and extensively studies by R.M. Willstatter, just before the outbreak of

the First World War. Many indicators can be extracted from plants. The substance in the

plant changes at the molecular level which causes their color to be different at different pH

levels. Red cabbage juice a natural pH indicator which is known to contain anthocyanins

which are pigments that react in a different way to acids and bases. (Chandrasekaran, 2001)

The substances in plant products such as tea, red cabbage or grapes react with acids

(or bases) resulting in changes at the molecular level which causes their colors to be different

at different pH levels. All pH indicators, such as litmus paper, change color depending

whether they donate or accept protons, (acids are proton donors and bases are proton

acceptors). Therefore, pH indicators are themselves acids or bases. (Withers, 2001)

Natural indicators have been used for hundreds of years, long before chemists made

synthetic acid-base indicators. The 17th century chemist, Robert Boyle described indicator

extracted from roses and other plant materials in his book “The Experimental History of

Colours”. Boyle included the ability to turn plant juices red among the properties of acids.

Red cabbage is not the only natural indicator that goes through a variety of color changes but

there are some other compound from plant origin that can act as indicators. Many of the

natural dyes have extracted and isolated from different parts of plants which have different

colors at different pH. It is also observed that some extracts exhibit different color at different

pH values. Cherry juice, for example, may be red (pH=7), or green (pH=10). Roses, turnip

skins, violets, plum skins, primroses, radish skins, hydrangeas, rhubarb skins, cherries, blue

berries, red grapes, beets, red wine, curry powder, geranium petals, grape juice concentrate,

etc. are only a few of many that have different colors in acid or base. Almost any highly

colored fruit, vegetable, or flower petal has the potential use as an acid-base indicator. (Khan,

et al., 2011)

CHAPTER III

MATERIALS AND METHODS

This chapter presents the methods, research design, data collection, materials and the

procedures that will be used in the study.

Research Method

The study is a descriptive one but will utilize an experimental design.

Materials

The materials that will be used in the study are the following: household chemicals,

such as muriatic acid, calamansi extract, feminine wash, vinegar, shampoo, distilled water,

monosodium glutamate, bath soap, detergent bar and powder solution, toothpaste, laboratory

chemicals such as HCl, HNO3, H2SO4, CuSO4, K2Cr2O7, Cr(NO3)3, Pb(NO3)2,

Ammonium Hydroxide, Ca(OH)2, NaOH, Aluminum Sulfate and 1000 grams of each plant

indicator such Red Cabbage, Purple Heart Plant leaves, Areca Nut, Eggplant, Muntingia, Red

Onion, Malabar Nightshade, Mangosteen, and synthetic indicators, such as litmus paper

strips, and phenolphthalein.

Equipments/Apparatus and Utensils

Nine beakers (100 mL), 190 test tubes, medicine dropper, knife, pot, strainer, and

stirring rod will be used in the study.

Procedure

Collection and Preparation of Samples

One thousand grams of each plant will be gathered and washed thoroughly.

Each plant may either be placed in a pot to boil or in a blender. In the case of

mangosteen or red cabbage, for example, both of them may just be boiled.

Extraction of Coloring Matter/pH indicator

Each plant will be chopped into smaller pieces and 500 g of each chopped

plant will be placed in a blender with 350 ml distilled water. The plants will be

blended separately. Each plant extract or liquid will then be poured into separate

containers.

In the case of mangosteen or red cabbage, the pieces will be placed in separate

container with enough boiling water to cover for at least 10-30 minutes. The contents

of the bowl will then be gently tipped into a sieve to drain it into another bowl. Coffee

filter will be used to remove the smaller pieces. The liquid will then be poured into

separate containers.

Testing Different Household/Laboratory Chemicals for pH level/Determination

of the Color Changes of Different Plants when used as Indicators

Twenty test tubes will be labeled for each plant extract (ten for household

chemicals and another ten for the laboratory chemicals). 5 ml of each household or

laboratory chemical will be poured into each test tube.

In the case of powdery ingredients such as the washing powder, we will be

mixed with water to form the solution, just like liquid chemicals.

Drops of each plant extract will be added into each test tube. Each mixture

will be stirred very well to see if there are any color changes in each solution. The

procedure will be the same for all plants and synthetic indicators (like litmus paper of

phenolphthalein) will also be used to determine the acidity or basicity of the

chemicals.

Comparing Color Changes

The results will be recorded to compare the color changes of the household

chemicals when treated with each plant indicator and with synthetic ones.

REFERENCES

Books

Kohlmann, Frederick J. “What Is pH and How is it Measured?” Hach Company, 2003; 3-6

Ophardt, Charles E. “Virtual Chembook: Acid and Base Indicators,” Elmhurst College. 2003

Theses and Journals

Chandrasekaran, Jayanthi. “Chemistry of Colours,” Jawaharlal Nehru Center for Advanced

Scientific Research Bangalore, India. 2001.

Khan, Pathan Moh’d Arif et al, “Journal of Advanced Scientific Research, Mumbai India.

2011; 2(4):20-27

Malapit, Christian, “Plant Extracts as Acid-Base Indicators,” Ateneo de Manila University:

Department of Chemistry. 2010

Manulon, Yusuf Khan N. et al, “Mangosteen Rind (Garcinia Mangostana) : A Potential pH

Indicator,” an Investigatory Project, a Requirements for Graduation, MSU TCTO

Science High School, Bongao, Tawi-Tawi. 2009

Tangkusan, Denzy Rose I. and Alih, Raisha T. “Red Onion (Allium Cepa Linn): A Potential

pH Indicator,” an Investigatory Project, a Requirements for Graduation, MSU

TCTO Science High School, Bongao, Tawi-Tawi

Vedad, Jamela R. “Cassava Leaf Extract as Acid Base Indicator,” an Investigatory Project,

Philippine Science High School Bicol Region Campus, 2005-2006

Internet Sources

Helmenstine, Anne Marie, Ph.D. “How to make Red Cabbage Indicator”

<http://chemistry.about.com/od/acidsbase1/a/red-cabbage-ph-indicator.htm >

Kayne, R. “WiseGeek: What is pH?” ed. Wallace, O. Conjecture Corporation. 2003

<http://www.wisegeek.com/what-is-pH.htm>

Litherland, Meal. “What are the advantages of pH paper?” 2011.

<www.ehow.com/list_5841280_advantages-pH-paper_.html>

Senese, Fred. “What are some natural acid/base indicators?” Rev. 2010

<http://antoine.frostburg.edu/chem/sense/101/acidbase/faq/naturalindicators.shtml>

Smith, S.E. “WiseGeek: What are Anthocyanins?” ed. Wallace, O. Conjecture Corporation.

2003 <http://www/wisegeek.com/what-are-anthocyanins.htm>

Withers, Gayathri. “NATURAL INDICATORS: HOW DO THEY WORK?”. GIPSE. 2001

<http://www.cmu.edu/gipse/materials/pdf-2001/natural_pH_indicators.pdf >

PLANT PROFILE

PLANT LOCAL NAME SCIENTIFIC NAME

Red Cabbage Pulang Repolyo Brassica oleracea var. capitata f. rubra

Purple Heart Plant ? Trandescantia pallida

Areca Nut ? Areca catechu L.

Eggplant Talong Solanum melongena L.

Muntingia Aratilis Muntingia calabura L.

Red Onion Pulang Sibuyas Allium Cepa L.

Malabar Nightshade Alugbati Brasella

Flow Chart of the Procedure

Collection of the Plants

Cleaning

Chopping

Blending

Plant Extract

Add drops to

Household Chemicals Laboratory Chemicals

Color Outcome/Color Change

Color Outcome/Color Change