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Meaning, examples and advantages of Commercial indicators.

Answer Text:
Commercial indicators.
- Are commercially prepared indicators which are sold in already purified forms.
Advantages of commercial indicators.
- They are relatively pure hence give consistent and reproducible results;
- They are readily available and easy to store in a Chemistry laboratory;
Main examples:
- Phenolpthalein;
- Methyl orange;
- Bromothymol blue;
- Litmus paper;
Note:
- Litmus is a blue vegetable compound which is extracted from “ plants” called lichens;
- Litmus paper is an adsorbent paper which has been dipped in litmus indicator solution then dried;
Colours of various commercial indicators in acids and bases.

The universal indicator.
- Is a full range indicator which gives range of coloursdepending on the strength of the acid or alkali.
- It is prepared by suitable mixing certain indicators;
- It gives a range of colour depending on the strength of acids and bases;
- Each universal indicator is supplied with a chart, to facilitate this classification.