Is it true that Hibiscus, Malaysia’s National Flower,
can be used to indicate the acidity or alkalinity of substances?
Hibiscus had been declared as the national flower for Malaysia in 1960.
The red petals symbolise courage, and the five petals represent the Rukun Negara (National Priniciples).
Let us look into the flower parts in detail..
Commonly used pH indicators are synthetic, however, a hibiscus flower can be used to make a natural indicator.
Which part of the hibiscus flower do you think can be used?
It’s the petals!
Let’s explore this simple experiment on how to produce natural indicator from Hibiscus rosa-sinensis colour extraction.
How do we do it?
Step 1
Remove the stigma, and detach the leaves, to have only the red petals remaining.
Step 2
Put them in a container and pour approximately 6ml of ethanol or surgical spirit; the latter works best.
Step 3
Crush the petals using a mortar and pestle until most of the liquid has been extracted from the petals.
Step 4
Filter the solution, and you have the purple reddish indicator ready!
What will happen?
Here are the results after we mixed the indicator with different substances.
What actually happened?
Various shades of colours
There are various colours of Hibiscus rosa sinensis flowers. The various shades exhibited by the flowers are due to a very small number of different pigments (anthocyanin).
Antocyanins
Antocynanins are coloured water-soluble pigments that are responsible for the colours in plants.
Neutral Solution
The acid salts of these pigments are usually red, their metallic salts usually blue and in neutral solution anthocyanins are violet.
Because of these characteristic, Hibiscus rosa sinensis can be used as an acid-base pH indicator.
What is a pH Indicator?
Example of Hibiscus extracts as an indicator at different PH.
A pH indicator or acid-base indicator is a compound that changes colour in solution over a narrow range of pH values.
The pH values of a neutral solution is 7.0. Solutions with a pH value below 7.0 are considered acidic and solutions with pH value above 7.0 are base (alkaline).
Other examples of natural indicators are turmeric, red cabbage, china rosa and grape juice.
What are the advantages of natural indicator compared to synthetic indicator?
Natural Indicator
- Much cheaper
- Less toxic to users
- Environmentally friendly
Synthetic Indicator
- High cost
- Have toxic effects on users such as diarrhea, pulmonary edema, hypglycemia etc.
- Can cause environmental pollution
Can the use of naturally-deprived compounds from hibiscus help save the environment?
As hibiscus flower contains the colour pigment anthocynanin, not only can it be used as a natural indicator, it can also be used to produce natural dye that is eco-friendly and safe on human skin.
Synthetic textile dye has been known to be toxic and carcinogenic, and as the efflents from the dyeing process enters water bodies, it pollutes the environment and cross the food chains.
Due to the harmful effects of synthetic dye to the environment, there a growing awareness and demand on the production of natural dye. As Malaysia is a biodiversity hotspot, other than hibiscus, there are a myriad of plants can potentially be researched as an alternative to the synthetic dyes.