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Basics of Indicators

Chemistry

definition

Indicator

Chemical indicator, any substance that gives a visible sign, usually by a colour change, of the presence or absence of a threshold concentration of a chemical species, such as an acid or an alkali in a solution. An example is the substance called methyl yellow, which imparts a yellow colour to an alkaline solution.

definition

Synthetic indicators

Indicators that are synthesized in laboratory are known as synthetic indicators.
For example:  phenolphthalein, methyl orange, etc.

definition

China rose as an indicator

China rose is a  type of natural indicator. A solution of china rose turns green in a basic solution, and bright pink or magenta in an acidic solution.

example

Process of identification of acids and bases through litmus paper

if a solution turns red litmus paper blue, it indicates that it is basic.
if a solution turns blue litmus paper red, it indicates that it is acidic.

definition

litmus (natural dye) and its source

Litmus is a natural dye extracted from lichens. It is the most commonly used natural indicator.

definition

Indicator

An indicator is any substance that gives a visible sign, usually by a colour change, of the presence or absence of a threshold concentration of a chemical species, such as an acid or an alkali in a solution. For example, a substance called methyl yellow imparts a yellow colour to an alkaline solution.

law

Process of identification of acids and bases through litmus paper

if a solution turns red litmus paper blue, it indicates that it is basic.
if a solution turns blue litmus paper red, it indicates that it is acidic.

definition

Natural Indicators

Indicators obtained from natural sources are called 'Natural Indicators'. The colour of a natural acid-base indicator depends on pH. One of the most well-known effects of natural indicators in plants occurs in the hydrangea or snowball plant. Hydrangea flowers are blue when grown in acidic soils and pink or red in basic soils.
Other common examples of Natural indicators include Turmeric, Beetroot juice etc. 

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