ABSTRACT
Samples
of Pride of Barbados flower were extracted and analysed for its indicator
properties in acid-base titration. Acetone, ethanol and acetone/ethanol
mixtures were used for the extraction. The results of the indicator extracts
showed greenish to amber colour in basic medium and pink at the end point for
all the extracts. The results of statistical analysis were compared with that
of the standard indicator (phenolphthalein) for precision. Extracts X showed
calculated FR value (1.0) < the critical FR value
(6.3) for (P = 0.05) and calculated Td (0.4) < critical Td
(1.27) for (p = 0.05). Extract Y gave calculated FR (2.0) <
critical FR (6.3) and calculated Td (0.2) < critical Td
(1.27) and extract Z gave calculated FR (1.0) < critical FR
(6.3) and calculated Td (1.0) < critical Td (1.27)
respectively. In all, the results showed that there is no significant difference
between the extracts X, Y, Z and the standard indicator (phenolphthalein).
Therefore, it is recommended that Pride of Barbados flower extract should be
used for standardization in acid base titration.
CHAPTER ONE
1.0 INTRODUCTION
1.1 Background of the
Study
In Nigeria, factors militating against science education are
the increasing unavailability and high cost of conventional science teaching
materials (Along, 2001 and Garba, 2001). This has threatened the potential for
the increase in students’ scientific knowledge for National development. The
use of local materials has been the subject of cost oriented study by
scientists over the years. Flower is one of such local (non-conventional)
material that could be used in place of standard indicator in science
(chemistry and integrated science) teaching.
Indicators are dyes or
pigments that are isolated from a variety of sources, including plants, fungi,
and algae. Almost any flower that is red, blue, or purple in colour contains a
class of organic pigments called rose that change colour with pH (Whitney and Smith, 2001).
The use of natural dyes as acid–base indicators was first reported in 1664 by
Sir Robert Boyle in his collection of essays Experimental History of colours.
Indeed, Boyle made an important contribution to the early theory of acids and
bases by using indicators for the classification of these substances. The idea,
however, may actually have originated much earlier—medieval painters used
natural dyes treated with vinegar and limewater to make different colour water
colour paints.
Rose pigments in flowers are
responsible for the red, purple and blue colours of many fruits, vegetables,
cereal grains and flowers. They are members of a class of water soluble,
terrestrial plant pigments that are classified as phenolic compounds
collectively named flavonoids. The difference in
chemical structure that occurs in response to changes in pH is the reason that Pride
of Barbados flower extracts can be potentially used as pH indicator, as they
change from red in acids to blue in bases. The unique property of these
pigments has been exploited as pH indicator (Chatterjee and Prakashi, 2006). Application of Pride of
Barbados flowers in the study
Commercial indicators are
expensive and some of them have toxic effects on users and can also cause
environ-mental pollution (Nwosu et al;, 2004).
For these reasons, there has been an increasing interest in searching for
alternative sources of indicators from natural origins. These alternatives
would be cheaper, more available, simple to extract, less toxic to users and
environmentally friendly. Volumetric analysis is one of the key quantitative
techniques used to analytically determine both inorganic and organic acid
interaction with strong or weak acids and bases in raw materials, intermediates
and finished products for quality assurance purposes (Nwosu et al., 2004). This is accomplished via
the use of appropriate weak organic dyes or acids pH indicators. Most pH
indicators are either weak organic acids or bases dyes which accept or donate
electrons. The change in Colour at a marginal range is attributed to their
acidity or basic properties. Although there are automated titration apparatus
that determine the equivalent points between reacting species, indicators are
still needed for teaching and research laboratories for simple titration (Nwosu
et al., 2004).
This present research therefore is to determine the
effectiveness of Pride of Barbados flower extracts as an indicator in an acid
base titration.
1.2 Statement of the
Problem
Indicators are frequently employed in acid-base
titrations, in analytical chemistry and biology to determine the extent of a
chemical reaction. Because of this, different indicators are used to measure
the pH of solutions. Commonly used pH indicators are the various commercial
indicators that are made synthetically, such as phenolphthalein, methyl red and
methyl orange. These commercial pH indicators are usually of high cost and some
of them have toxic effects on the users and can also cause environmental
pollution. Thus, leads to unavailability or limited quantity in the
laboratories. For these reasons, there has been an increasing interest in
searching for alternative sources of indicators from natural origins such as
plants in order to measure the pH of a solution other than using commercial pH
indicators. These alternatives would be cheaper, more available, simple to
extract, less toxic to the users and environmentally friendly.
1.3 Objectives of the
Study
The
research study aimed to form a natural pH indicator sourced from rose pigment
in Pride of Barbados flower petals extract. Specifically, the study seeks to
answer the following questions:
1. What is
the pH of the acidified methanol rose pigments extracted from Pride of Barbados flower and water rose flower
extract?
2. What colour change does the Pride of
Barbados flower extracts exhibit during pH indicator application?
3. Is there any significant
difference between the results of the application of the extracted pH
indicators with methyl-orange pH indicator in determining the equivalence point
in different types of titrimetric analysis?
1.4Justification of the
Study
In this study, the potential of some flowers as
indicator in acid - base titration was assessed. The results of the study would
enrich teaching and learning instruction in science, especially integrated
science and chemistry. It would also enhance students’ at understanding the
diversity of the natural environment in science and motivate teachers’ interest
toward improvisation of teaching / learning materials.
It is hoped that through a successful result of this research study, it will give
benefit to the following:
1. To
the students. They will be able to use
the Pride of Barbados flower extract as an effective and safe
substitute to those expensive commercial indicators in measuring the pH of a solution.
2. To
the institution. They can introduce
the Pride of Barbados flower extract in their science laboratories
as an effective substitute to the frequently used commercial indicators such as
phenolphthalein, provided that these Pride of Barbados flower extracts sourced from rose pigments in Pride of
Barbados is less
expensive and safe to use.
3. To
the community. The study will give great value to the common
flower. Thus, the study will give the needed interest to the people of the
community to become motivated in cultivating Pride of Barbados flowers.
4. To
the researchers. The success of the
study would bring a sense of fulfillment
and accomplishment to
the researchers.
1.5Scope and Duration of
Study
The
research consisted of field sample collection, laboratory analysis of pride of
Barbados pigment content, an acid base titration experiment and comparison with
international minimum standard by F.A.O. and W.H.O. The research work lasted
for five months (March to July 2017).
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