  The corresponding states principle is an important concept wherein materials
are interrelated. The base state of this principle, however, currently has no
specific physical reality. Instead, it is a definition: a set of conditions at
which the gas state reaches its maximum compression and liquid can not longer
form; namely, the critical point.
  This article shows that a discrete, real-life, 3-D, base state is consistent
with published and new experimental data. The mathematical analyses were
conducted in the same manner for all the materials using literature data, a
simple, consistent liquid state model and a simple, physically definable,
cluster state model at the critical point. The base state described herein has
molecules traveling together in well-defined small-hard or large-soft clusters.
These clusters are dubbed the DELTA state since they occur almost exclusively
in tetrahedral groups of four. From this straightforward, mathematical and
intuitive methodology, the DELTA state emerged as the fourth state of matter:
the base state of the corresponding states. As a result, the universal gas law
requires inclusion of the DELTA state with the monomer state to be accurate.
The critical point is the point at which liquid ceases to form. It is also the
point at which only the DELTA state exists. Hence, the critical point is more
appropriately called the DELTA POINT.
