What does [CH₂O] represent in the empirical equation of...

By the middle of the nineteenth century the key features of plant photosynthesis were known, namely, that plants could use light energy to make carbohydrates from CO₂ and water. In the empirical equation representing the total process of photosynthesis for oxygen evolving organisms, [CH2O] represented a carbohydrate (e.g., glucose, a six-carbon sugar). A milestone contribution to the understanding of photosynthesis was that made by a microbiologist, Cornelius van Niel (1897-1985), who, based on his studies of purple and green bacteria, demonstrated that photosynthesis is essentially a light-dependent reaction in which hydrogen from a suitable oxidisable compound reduces carbon dioxide to carbohydrates.