CHAPTER ONE

1.0     INTRODUCTION

Distillation is a separating technique in which two liquids are separated at essentially the same temperature and pressure.  It is also the term used to describe the operation where the vaporization of a liquid mixture yields a vapor phase containing more than one constituents and it is desired to recover one or more of this constituents in a nearly pure state.

            It would probably be beneficial to define the terms that describe the process and related properties.  Let us begin by describing the process by which a substance transformed from the condensed phase to the gas phase.  For liquid, this process is called VAPORIZATION and for a solid it is called SUBMIATIN, both processes requires heat.  All substances regardless whether they are liquids or solids are characterized by a vapor pressure.  The vapor pressure of a pure substance is the pressure exerted by the substance against the external pressure which is usually atmospheric pressure.  Vapor pressure is a measure of the tendency to escape.  When the vapor pressure of a liquid substance reaches the external pressure the substance is observed to Boil.  If the external pressure is atmospheric pressure, the temperature at which a pure substance boils is called the NORMAL BOILING POINT.