Formocresol is a mixture consisting of formalin, cresol and glycerine used in dentistry. This reaction occurs at high temperatures in organic solvents including cresol, nitrobenzene, benzonitrile, and sulfolane. It is composed of phenols such as guaiacol, cresol, xylenol, and creosol. CHO/cresol ratio is typically around 15%. It is composed mainly of phenol (phenolic acid) and cresol (cresylic acid). The compound is synthesized by bromination of cresol purple ("m"-cresolsulfonphthalein). Train 192 was transporting chlorine gas, sodium hydroxide and cresol. The name cresol reflects their structure, being phenols, and their traditional source, creosote. Cresol is used for leathery or medicinal flavoring.