GLOSSARY - Archaeological Chemistry - page 506

plasticity, water of See water of plasticity .

plate (lithospheric) A slab of rigid, moving crust in the uppermost mantle of the

earth.
plating Formation of an adherent layer of (a usually precious) metal on an object
made from another, usually base , metal; see dipping , metal leaf , amalgamation ,
gilding .
pollen The male sex spores of flowering plants.
pollution The contamination of the environment , atmosphere , water, and/or soil , with
undesirable substances and/or factors that are detrimental to living organisms or
to inorganic mater .
polygenetic dye See dye, polygenetic .
polymer A substance whose molecules are very large and are formed by the bonding
together of many (more than five) monomers .
polymerase Any enzyme that catalyzes the polymerization of small, monomeric mole-
cules , into large polymers .
polymerase chain reaction (PCR) A technique employed to rapidly amplify

segments of DNA .
polymerization

A type of chemical reaction in which monomers combine to form

polymers .
polymorph Any one of various crystalline forms of the same substance.
polypeptide A biopolymer formed by amino acid monomers ; polypeptide molecules are
larger than those of the peptides, but smaller than the molecules of proteins .
porcelain A highly vitrified and translucent ceramic material made when kaolin clay
that is fired at very high temperatures (above 1350°C).
porosity The volume of the voids within a porous solid; it is usually expressed as
a percent of the total volume of the solid.
positron A subatomic particle having the same mass as an electron but a positive
electric charge.
positron decay A form of radioactive decay whereby a proton emits a positron and is
converted to a neutron .
positron emission A form of radioactive decay involving the emission of a positron
from an unstable atomic nucleus .
potash The common name for the basic substance potassium carbonate; it is used
in glassmaking as a modifier , an alternative to soda .
potassium-argon dating (K-Ar dating) See dating, potassium-argon ( K-Ar dating ).
potential, electrochemical See electrochemical potential .
pottery A ceramic material made of fired clay ; see terracotta or earthenware ; the term
is often also used in a loose sense to refer to most types of ceramic objects made
of clay .
pozzolana A siliceous and aluminous material that combines with lime to form
hydraulic cement that sets even under water; natural pozzolanas, derived primarily