Introduction

It is now estimated that there are some 50 million pure chemicals known of which some 20,000 are listed as high–volume, major chemicals by the European Economic Community (Forcheri & de Rijk 1981) some of which may be transported across national borders. For each pure fluid there are approximately 30 properties which are of technological significance of which twelve are functions of temperature and pressure. If just these twelve properties are considered and it is assumed that measurements at only ten pressures and ten temperatures are required then to provide the necessary information for only one pure fluid requires 1200 measurements. If all the pure species and all possible mixtures from among the set of bulk chemicals are included and composition is allowed as a variable then it is rather easy to estimate that, even for a generous estimate of the rate of experimental data acquisition in the world, the total effort required to fulfill the needs identified in Chapter 2 would exceed 100 billion man–years. This figure makes it immediately obvious that industry's needs for physical property data can never be met by measurement alone. It is therefore necessary to replace a complete program of measurements by an alternative strategy designed to meet the same objective. The philosophy and methods for the establishment of such a strategy have been discussed by many authors and have been updated regularly and most recently by Nieto de Castro & Wakeham (1992).