Ascorbic Acid is an organic acid with antioxidant properties. The L-enantiomer of ascorbic acid is commonly known as vitamin C.
In 1937 the Nobel Prize for chemistry was awarded to Walter Haworth for his work in determining the structure of ascorbic acid, (It was shared with Paul Karrer, who received his award for work on vitamins), and the prize for Physiology or medicine that year went to Albert Szent-Gyorgyi for his studies of the biological functions of ascorbic acid.
Ascorbic acid is easily oxidized and so is used as a reductant in photographic developer solutions (among others) and as a preservative.
Exposure to oxygen, metals, light and heat destroy ascorbic acid, so it must be stored in dark and cold and not in a metal containment.
Photographers' Formulary 10-0241 100G Specs
L-Ascorbic acid 3-oxo-L-gulofuranolactone (enol form) Vitamin C
As a developing agent, and as a preservative
As a developing agent it acts more vigorously at higher alkalinities. It is slow to get started but gives images with low fog. At low alkalinities, in combination with metol or Phenidone, ascorbic acid is an active, long-lasting developing agent.