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Preparation of Methyl Red-Methyl Blue Indicator (Mixed Indicator)

1. - Weigh out 0.1 g of methyl red (as sodium salt) and dissolve completely in 50 ml of ethanol (ethyl alcohol).
2. - Weigh out 0.05 g of methylene blue and dissolve completely in 50 ml of water.
3. - When both are thoroughly dissolved, mix them together and store a portion in a dropping bottle for use.

alternatively

1. - Weigh out 0.1 g of methyl red and 0.05 of methylene blue and place in a 100 ml beaker.
2. - Prepare a 50% ethanol solution consisting of 50ml ethanol and 50 ml water.
3. - Dissolve completely the methyl red and methylene blue with some of the ethanol solution and bring up to a volume of approximately 100ml using the ethanol solution.
4. - Store a portion in a dropping bottle for use.