A white shirt has a yellow stain of curry. When a soap is rubbed on the shirt to clean it, the yellow stain turns reddish-brown. On rinsing, the reddish-brown stain turns back to yellow. Name the natural indicator present in the curry stain.
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Solution
Turmeric is the natural indicator present in curry stain. The yellow stain of curry turns reddish-brown when soap is rubbed on it because soap solution is basic in nature that changes the colour of turmeric in the curry stain to reddish-brown. This stain turns yellow again when the cloth is rinsed with water because then the basic soap gets removed with water.