The carbonyl group draws electrons away from the alkene, and the alkene group is, therefore, deactivated towards an electrophile, such as bromine or hydrochloric acid.
Moreover, the calcite alabaster, being a carbonate, effervesces upon being touched with hydrochloric acid, whereas the gypsum alabaster, when thus treated, remains practically unaffected.
The second and more common method uses potatoes or sweet potatoes as the starch source, and added acid, such as hydrochloric, sulfuric or nitric acids.
