My brother had some leftover oxygen and carbon dioxide indicator solution for one of his take-home experiments from school, so he let me have them. I want to use them for an experiment and write out some reactions, but I don't know what compound is in the indicators that gives them their color.

The oxygen indicator is green and comes with a color chart which says the following in regards to concentration of oxygen: 2ppm is red, 4ppm is purple, 6ppm is yellow, 8ppm is light green, 10ppm is dark green/teal, and 12ppm is either very dark green/blue or black.

The carbon dioxide indicator is orange and comes with a color chart saying low CO2 concentration gives a red color, medium is orange, and high is yellow.

A few websites said that you could make a bicarbonate indicator with thymol blue and cresol red, but I don't know how that makes sense if the color chart only ranges from red to yellow. As for the oxygen indicator, I have no idea what the compound(s) can be.

Thanks in advance!


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