L-ascorbic acid, which is often equated with vitamin C (Marks, 1975), has much in common with its precursor, D-glucose. The empiric formula is C6H8O6, and in its pure form it is a white odourless, crystalline substance with a melting point of 192°C. It is a very powerful reducing agent, reducing silver nitrate, potassium permanganate, iodine, and many organic substances. It is freely soluble in water, slightly soluble in ethanol, and quite insoluble in most non-polar lipid solvents. In crystalline form, kept dry and not exposed to light, it is stable for a considerable length of time. In an aqueous solution it is attacked by atmospheric oxygen, other oxidizing agents, high pH, high temperature and metallic ions.
L-ascorbic acid is reversibly converted to dehydroascorbic acid, which together constitute the active form of vitamin C (Hodges, 1980). Dehydroascorbic acid can be oxidized further both rapidly and irreversibly at a pH above 4 where traces of heavy metal ions, e.g. copper, act as catalysts. The end products are oxalic acid and L-threonic acid.