In order to cope with the increasing number of publications on the separation of enantiomers by chromatography on a chiral stationary phase, the graphical molecular database CHIRBASE was created. In the present state, the database package covers information (structural, bibliographic, and chromatographic data) on liquid-, supercritical fluid-, and gas chromatography; other methods will follow. CHIRBASE, running on the MDL software Chembase, meets the requirements of contemporary information management in the chemical and pharmaceutical industry. (Detailed information including a demo-version of each part of CHIRBASE can be obtained from the authors on request).

The Tb3+ activated oxyorthosilicates of the system Y2−‐xGdxSiO5 crystallize in the X2 (x ≦ 1.2) or the X1 type (x = 1.6). The CL and PL properties are strongly influenced by the crystal structure. The X1 type is more efficient in PL and the X2 structure in CL. The influence of the Gd3+ content on the CL and PL properties is studied and discussed.

Cathode ray excitation of X2–Y2SiO5:Eu3+ results in a moderate red emission. The efficiency is enhanced considerably (≈ 700%) by the simultaneous introduction of a high Tb3+ concentration (e.g. YTbSiO5:Eu3+). An enhancement of the photoluminescence emission is observed as well. The luminescence properties are studied as a function of the Tb3+ content. The mechanism of energy transfer in cathodo‐ and photoluminescence are discussed.

The properties of praseodymium zircon yellow and of corresponding samples with a nominal substitution of Ce4+ for Zr4+ as well as Ti4+ for Si4+ (system ZrSiO,: Pr,Ce,Ti,) are investigated by X-ray methods, diffuse reflectance, and vibrational spectroscopy. From the present results follows that the ZrSiO, structure does not tolerate a significant substitution level on either Zr4+ or Si4+ regular lattice positions by the larger foreign ions Ce4+, Pr4+, and Ti4+. Thus, the yellow colour is the result of the usual colour-centre formation, charge compensated by Pr3 + ; whereas the highly forbidden 4f -+. 4f transitions of Pr3+ are practically without influence on the coloration. Die Eigenschaften von Zirkon-Praseodym-Gelb sowie von entsprechenden Proben mit einer nominellenSubstitution von Ce4+ fur Zr4+ bzw. Ti4+ fur Si4+ (System ZrSiO,: Pr,Ce,Ti,) werden mit rontgenographischen Methoden sowie durch diffuse Reflexionsspektroskopie und Schwingungsspektroskopie untersucht. Die erzielten Ergebnisse zeigen, daB die Zirkon-Struktur weder einen bedeutenden Substitutionsgrad auf regullren Zr4+-noch auf Si4+-P1atzen durch die groBeren Ionen Ce4+, Pr4+ oder Ti4+ zulal3t. Daher ist die gelbe Farbe das Resultat einer gewohnlichen Farbzentren-Bildung, der Ladungsausgleich erfolgt durch Pr3 +. Dagegen uben die stark verbotenen 4f + 4f-Ubergange von Pr3 + praktisch keinen EinfluR auf die Farbung aus.