Hydrogencarbonate Indicator

Increasing CO2 in indicator

Decreasing CO2 in indicator

Atmospheric CO2 level

Hydrogencarbonate indicator is used to measure carbon dioxide levels.It is red in equilibrium with atmospheric air.It becomes more orange/yellow with increased carbon dioxide levels.It changes from red through magenta to deep purple as carbon dioxide is removed.

yellow orange red magenta purple pH 7.6 pH 7.8 pH 8.0 pH 8.2 pH 8.4 pH 8.6 pH 8.8 pH 9.0 pH 9.2

Carbon dioxide released from a burning candle or a terrestrial organism can be added to hydrogen carbonate indicator.

Start point Respiration or Combustion

pH 8.4 (cherry red);0.04% CO2 in atmosphere

pH 8.0 (yellow); more yellow because of increased CO2 produced in respiration or combustion (creates carbonic acid).

How can we show that plants use carbon dioxide in photosynthesis?

Result in bright light

Start point Photosynthesis

pH 8.4 (cherry red);0.04% CO2 in atmosphere

pH 9.2 (purple); more purple because CO2 is being removed from the indicator for use in photosynthesis. This reduces the amount of carbonic acid in the solution so it becomes more alkaline