It thus possesses the same composition as the hydrocarbon of gutta-percha and as that of oil of turpentine and other terpenes which are the chief components of essential oils.
This work led naturally to the synthesis of many terpenes and members of the camphor group; also to the investigation of various alkaloids and natural colouring matters.
They are closely related to the terpenes, with which they occur in plants and of which they are oxidation products.
To celebrate his seventieth birthday his scientific papers were collected and published in two volumes (Gesammelte Werke, Brunswick, 1905), and the names of the headings under which they are grouped give some idea of the range and extent of his chemical work: (1) organic arsenic compounds, (2) uric acid group, (3) indigo, (4) papers arising from indigo researches, (5) pyrrol and pyridine bases, (6) experiments on the elimination of water and on condensation, (7) the phthaleins, (8) the hydro-aromatic compounds, (9) the terpenes, (io) nitroso compounds, (11) furfurol, (12) acetylene compounds and "strain" (Spannungs) theory, (13) peroxides, (14) basic properties of oxygen, (15) dibenzalacetone and triphenylamine, (16) various researches on the aromatic and (17) the aliphatic series.
Hexahydrocymene (methyl-i-isopropyl-4-cyclo-hexane), C10H20, is important since it is the parent substance of many terpenes (q.v.).