sentences: a potassium is a mean of celestial preposition
docs: potassium_bromide is salt. potassium is mineral. potassium_phosphate is salt. atelic_directional_preposition is spatial_preposition. potassium is element. potassium_32 is potassium. locative_preposition is spatial_preposition. directional_preposition is spatial_preposition. spatial_preposition is preposition. telic_directional_preposition is spatial_preposition.