The researchers used different techniques to analyze the properties of two types of coal, vitrinite and inertinite. They found that vitrinite has more hydrocarbon, nitrogen, and sulfur elements, while inertinite has more oxygen. Vitrinite has more aliphatic hydrocarbon side chains, while inertinite has more aromatic rings and oxygen-aliphatic structures. Inertinite contains more carboxyl groups. Nitrogen in the coal is mostly in the form of pyridine, and sulfur is mostly in the form of mercaptan and sulfoether. The molecular formula of vitrinite is C126H99O12N3S2, and the molecular formula of inertinite is C131H98O17.