Meconic acid.
Meconic acid, also known as acidum meconicum and poppy acid is a dicarboxylic acid found in certain plants of the Papaveraceae (poppy) family such as Papaver somniferum (the opium poppy). Meconic acid constitutes around 5% of opium and can therefore be used as an analytical marker to look for the presence of opium.
Chemistry[]
Meconic acid presents as colorless crystals. It is slightly soluble in water and readily soluble in ethanol. The addition of ferric chloride results in a red colour. The acid forms salts with alkaloids and metals, which (in addition to meconic acid esters) are known as meconates. Examples of naturally occuring meconates would be morphine meconate and codeine meconate, which are both found within opium poppies. Acid-base reactions used in the extraction of morphine from opium typically involve replacing the morphine in morphine meconate with a metal cation; for example, adding calcium chloride to a solution of opium will result in calcium meconate precipitating out of the solution, allowing it to be disposed of and leaving the morphine in solution.