Essential oil ofArtemisia scoparia
The chemical composition of the essential oil of oriental wormwood growing in Kazathstan has been investigated. Of the components of the oil, 28 have been identified, and the structure of an acetylenic hydrocarbon has been refined.
Essential oils and their constituents : XXXII. Gas chromatography of sesquiterpene hydrocarbons☆
Abstract Characteristic gas chromatographic criteria of identity are reported for 34 authenticated sesquiterpene hydrocarbons, using Reoplex 400, silicone nitrile XE-60 and silicone rubber SE-30 as column substrates and naphthalene, 2-methylnaphthalene and acenaphthene as internal reference standards. The value of the experimental data is demonstrated by application to the analysis of essential oils and correlation with characteristic structural features of some sesquiterpenes. The occurrence of ylangene, α-bergamotene and δ-cadinene in oil of copaiba balsam is reported for the first time.
The crystal structure of stilpnomelane. Part II. The full cell
Summary The structural formula of stilpnomelane averaged from 37 representative literature analyses and based on the determined structure is (Ca,Na,K)4(Ti0·1Al2·3Fe35·5Mn0·8Mg9·3)[Si63Al9](O,OH)216·nH2O. Ferrostilpnomelanes have up to 12 R 3+ cations in the octahedral sheet, ferristilpnomelanes commonly have between 24 and 30 R 3+ cations, rarely up to 37. The two groups can be distinguished by accurate X-ray powder diffraction, ferrostilpnomelanes having d 001 less and a greater than have ferristilpnomelanes. The unit cell is triclinic, a = b∼21·8 Å, γ = 120°, d 001∼12·2 Å, P . Hexagonal groups or ‘islands’ of 24 silicon-oxygen tetrahedra co-ordinate to the octahedral sheet, the centres of the ‘islands’ are displaced by 5a/12, 8b/12 on either side of the octahedral sheet as a result of warping of this sheet to permit articulation with the smaller tetrahedral sheet. The 24-tetrahedra ‘islands’ are linked laterally by 6-member rings of inverted tetrahedra, which in turn link at their apices to like rings connecting the next sheet of ‘islands’. Thus a single tetrahedral layer is 4 tetrahedra thick and has symmetry 6/m. The 6-member rings of tetrahedra act as hinges permitting up to 0·5 Å extension or contraction of the tetrahedral sheet to accommodate variations in the octahedral sheet dimensions with varying R 2+/R 3+ ratio.