BUREAU OF GEOLOGY


trolled enrichment of the sample in carbon-14. Syn: radiocarbon dating;
carbon dating.

carcinogen A substance which tends to produce a cancer.

cellulose A polymeric carbohydrate composed of glucose units, for-
mula (C6H10Os)x, of which the permanent cell walls of plants are formed,
making it the most abundant carbohydrate.

coalification The alteration or metamorphism of plant material into
coal; the biochemical processes of diagenesis and the geochemical pro-
cess of metamorphism in the formation of coal. See also: carbonization.

COD (Chemical Oxygen Demand) The amount of oxygen required for
the oxidation of all oxidizable compounds in a water body. Cf: biochem-
ical oxygen demand. Var: oxygen demand.

colloidal gel A translucent to transparent, semisolid, apparently
homogeneous substance being elastic and jelly-like (or sometimes more
or less rigid), offering little resistance to liquid diffusion, and containing a
dispersion or network of fine particles that have coalesced to some
degree. Colloidal particles are less than .0000094 inches in size (i.e.
smaller than clay sized).

core A cylindrical or columnar piece of solid rock or section of soil,
usually 1.75 4.0 inch or so in diameter and from an inch up to 50 feet or
so in length, taken as a sample of an underground formation by a special
hollow-type drill bit, and brought to the surface for geologic examination
and/or chemical analysis. It records a section of the rock or soil pene-
trated.

crystal A homogeneous, solid body of a chemical element, com-
pound or isomorphous mixture having a regularly repeating atomic
arrangement that may be outwardly expressed by plane faces.

desiccation A complete or nearly complete drying out or drying up, or
a deprivation of moisture or of water not chemically combined; e.g. the
loss of water from pore spaces of soils or sediments as a result of com-
paction or evaporation.

dewatering Processing which reduces the amount of water within
peat or a peat deposit prior to mining and processing. Ditching and pump-
ing are used prior to mining. Solar, mechanical and thermal drying along
with wet carbonization and wet oxidation can be used prior to or in
conjunction with processing.

dichloroethane A heavy, colorless, flammable liquid, C2H4CI2, a non
polar organic solvent.