Picric acid is a yellowish crystalline solid. It is used as a high explosive, an oxidant in rocket fuels, in matches and leather processing,
Crotonaldehyde is a colorless or white liquid with a suffocating odor which turns a pale-yellow color on contact with air. It is used as an intermediate for production of sorbic acid and formerly was used in manufacture of n-butyl alcohol. It is formed during fossil fuel combustion.