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Red Cabbage Juice as an Effective pH Indicator

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Janice Lee

on 13 August 2014

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Transcript of Red Cabbage Juice as an Effective pH Indicator

Results and Observations
From pH 0 -------> pH 14
Strength of Red Cabbage Juice Indicator
Red cabbage juice have the bigger variance in colour compared to other.
Weaknesses of Red Cabbage Juice Indicator
Why is Red Cabbage juice not used
if it is so good ?
What are the example of natural substances with anthocyanins?
What is Anthocyanins ?
How does It Works ?
Anthocyanins are weak Bronsted-Lowry acids. They are proton donors who give up protons to become conjugate bases. Different forms of some molecules (with different proton number) will reflect light differently, causing a color change.
Problem Statement :
Results & Discussion
Red cabbage juice is a sensitive pH indicator with high detection range.
Cheap, convenient and natural pH indicator.
Production of red cabbage pH paper is useful for usage.
Majorly, red cabbage juice indicator is suitable for household usage but not industrial or specific usage.
Red Cabbage Juice as an Effective pH Indicator

Beetroot, blueberries, rose, red cabbage, grape and others.
Can red cabbage juice act as natural pH indicator? What properties in red cabbage allow it to act as pH indicator?
General Objective :
To study the anthocyanins properties in red cabbage which make it act as an
pH indicator.
Specific Objectives :
i) To compare the effectiveness of red cabbage juice as pH indicator compare to
other pH indicator such as methyl orange solution and other edible natural
pH indicator.
ii) To create a natural pH indicator which are environmental friendly, cheap
and convenient.

What is natural acid base indicator ?
Natural substances that contain anthocyanins which are able to act as natural acid base indicato by changing colour.
Anthocyanins are water-soluble vacuolar plant pigments that may appear red, purple, or blue depending on the pH.
*2 proton (red hydrogen) readily to be donated.
*Reflects red light
* pH < 7
*1 proton readily to be donated.
*Reflects blue light
* pH >7
*No proton to be donate
*Reflects yellowish green light
*pH > 12
Why do we carry out this experiment ?
Observation :
High detection range
Big variance in colour
Natural, environmental friendly
Cheap, can be get easily
High sensitivity
Can be made into pH paper which can be stored and use easily
Colour change is only based on approximation.
Colour change can be affected by external condition.
Not able to withstand extreme value of pH.
Red cabbage are rare and recessive.
Only suitable for certain usage but not SPECIFIC USAGE such as laboratory experiment
Full transcript