The author's classical work on the ring analysis of mineral oils has been developed into a complete new system of investigation methods which have a specific character and are suitable for general application. The research field has become a very extensive one, and comes into contact with many branches of chemical industry.The methods discussed may assist in gaining more insight into many natural products handled in industry and products prepared in factories. The applications of these methods are numerous; the purpose of this treatise is to enable everybody to become acquainted with them.