The best replacement for carbon dioxide is carbon monoxide.

The best alternatives to carbon dioxide are rated as following:
★★★★★  carbon monoxide
★★★  temperature
★★  oxygen
★★  methane
★  monoxide
★  water vapor
★  carbon monoxide poisoning
  silicon dioxide
  water have a higher boiling point
  nitrogen dioxide
  bicarbonate
  nitrous oxide
  more oxygen
  carbon
  nitrogen
  helium
  oxygen heavier
  man made carbon dioxide

Your alternative for carbon dioxide is not listed? Suggest!
Speaking about carbon dioxide, one probably shouldn't forget about limewater.

Other search terms related to carbon dioxide and their ratings are:
★★★★★ limewater
★★★ sodium hydroxide
★★★ calcium hydroxide
★★★ lime water
★★ hydrogen
★★ grignard reagent
★ global warming
★ lime water reaction
★ potassium hydroxide
calcium oxide
barium hydroxide
grignard
You have in mind a companion for carbon dioxide and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of carbon dioxide in all years. Click on graph for more.
carbon dioxide
carbon monoxide
temperature