Creosote removed; the "heavy oil", which sinks; and the "anthracene oil", which when cold is mostly solid and greasy, of a buttery consistence. Creosote refers to the portion of coal tar which distills as "heavy oil", typically between 230–270 °C, also called "dead oil"; it sinks into water but still is fairly liquid. Carbolic acid is produced in the second fraction of distillation and is often distilled into what is referred to as "carbolic oil". Commercial creosote will contain substances from six groups. The two groups occur in the greatest amounts and are the products of the distillation process—the "tar acids",
Disulfuric acid acid is strong enough to protonate "normal" sulfuric acid in the (anhydrous) sulfuric acid solvent system. There are salts of disulfuric acid, commonly called pyrosulfates, e.g. potassium pyrosulfate. There are other related acids with the general formula HO·(SO) though none are isolable. Disulfuric acid Disulfuric acid (alternative spelling disulphuric acid) or pyrosulfuric acid (alternative spelling pyrosulphuric acid), also named oleum, is an oxyacid of sulfur. It is a major constituent of fuming sulfuric acid, oleum, and this is how most chemists encounter it. It is also a minor constituent of liquid anhydrous sulfuric acid due to the equilibria: The acid