2912: Aldehyde, its cyclic polymers, paraformaldehyde

291211: Methanal (formaldehyde) 291212: Ethanal (acetaldehyde) 291213: Butanal (butyraldehyde, normal isomer) 291219: Acyclic aldehydes without other oxygen function, nes 291221: Benzaldehyde 291229: Cyclic aldehydes without other oxygen function, nes 291230: Aldehyde-alcohols 291241: Vanillin(4-hydroxy-3-methoxybenzaldehyde) 291242: Ethylvanillin(3-ethoxy-4-hydroxybenzaldehyde) 291249: Aldehydes, derivs with other oxygen function 291250: Cyclic polymers of aldehydes 291260: Paraformaldehyde 2912: Aldehyde, its cyclic polymers, paraformaldehyde