What would the name be of the molecule P2O5?

Phosphorus pentoxide is a chemical compound with molecular formula P4O10 (with its common name derived from its empirical formula, P2O5). This white crystalline solid is the anhydride of phosphoric acid. It is a powerful desiccant and dehydrating agent.

The paint symbolizes the savagery which Jack's tribe has descended into. The face paints are, made of earth, real, and their effect is real too. The paint serves to reduce the boys to almost animal like status, concerned with the basic fundamentals of life, killing, eating and shelter from wild beast and enemies. Ralph's desire for smoke is insubstantial and it represents something insubstantial too, the possibility of rescue and the return to a so-called civilised world.