The D'Ans - Lax is a standard work for natural scientists; it provides important numerical data for daily work. The fourth edition has been completely revised, and all values are now presented in SI units. The first volume contains general physical-chemical information, while the third volume will be dedicated to inorganic chemistry. The topics covered have not changed; however, some conversion tables have been omitted, as calculators are now widely available. Data for modern spectroscopic methods have also been included.