Codeine is an alkaloid obtained from opium or prepared from morphine by methylation and occurs as white crystals. Codeine effloresces slowly in dry air and is effected by light. The normal method of application is via codeine phosphate. The chemical name of codeine phosphate is 7,8-Didehydro-4,5alpha-epoxy-3-methoxy-17-methylmorphinan-6alpha-ol phosphate (1:1)(salt) hemihydrate and has the empirical formula of C18H21NO3H3PO41/2H20. Its molecular weight is 406.4.

Codeine Phosphate

Codeine was first isolated from opium by the French chemist Pierre-Jean Robiquet in 1832.

Name Codeine 
Chemical name (5alpha,6alpha)-7,8-didehydro-4,5-epoxy-3-methoxy-17-methylmorphinan-6-ol 
Alternative names methylmorphine, morphine monomethyl ether 
Chemical formula C18H21NO3 
Molecular weight 299.37 
Boiling point 250C (480F) at 22mm/Hg 
Melting point 154-156C (309.2-312.8F) (monohydrate) 
Flash point 75C (167F) 

Name Codeine phosphate 
Chemical name (5alpha,6alpha)-7,8-didehydro-4,5-epoxy-3
-methoxy-17-methylmorphinan-6-ol dihydrogen orthophosphate hemihydrate 
Chemical formula C18H21NO3.H3PO4 
Molecular weight 397.40