c, peroxidases, catalases, flavoproteins, and pyridin-
proteins, particularly the alcohol dehydrogenases. For
his work on the nature and effects of oxidation
enzymes he was awarded the Nobel Prize for physiol-
ogy or medicine for 1955.
He was a member of numerous scientific organiza-
tions and in 1954 was chief editor of the journal
Nordisk Medicin.He died on August 15, 1982.
theoretical chemistry A branch of chemistry that
deals with structure theory, molecular dynamics, and
statistical mechanics.
theoretical yield The maximum quantity of a prod-
uct that can be formed in a chemical reaction if all the
LIMITING REACTANTreacted to form products.
therapeutic index For a substance used to alleviate
disease, pain, or injury, the therapeutic index is the
ratio between toxic and therapeutic doses (the higher
the ratio, the greater the safety of the therapeutic
dose).
thermal analysis Measurement of the relationship
between the physical and/or chemical properties of a
sample and its temperature. Some methods that are
commonly used are differential thermal analysis (DTA):
temperature difference between the sample and a stan-
dard; differential scanning calorimetry (DSC): heat-
flow difference between the sample and a standard;
thermogravimetric analysis (TGA): mass vs. tempera-
ture; and thermomechanical analysis (TMA): dimen-
sion vs. temperature.
thermal cracking The degrading of heavy oil
molecules into lighter fractions using high temperature
and without using a catalyst. Used in the petroleum
refining industry and used to convert gasoline into
naphtha.
thermal neutron A neutron in thermal equilibrium
within the medium in which it exists. A neutron with
about the same energy as the surrounding matter (less
than 0.4 eV).thermal pollution Excessive raising or lowering of
water temperature above or below normal seasonal
ranges in streams, lakes, estuaries, oceans, or other bod-
ies of water as the result of discharge effluents (hot/cold).thermodynamic control (of product composition)
The term characterizes conditions that lead to reaction
products in a proportion governed by the equilibrium
constant for their interconversion and/or for the inter-
conversion of reaction INTERMEDIATEs formed in or
after the RATE-LIMITING STEP. (Some workers prefer to
describe this phenomenon as “equilibrium control.”)
See alsoKINETIC CONTROL.thermodynamics The study of the energy transfers
or conversion of energy in physical and chemical pro-
cesses.thermogravimetric analysis(TGA) Precise mea-
surement of the weight change of a solid as it is heated
at a controlled rate.thermoluminescence A phenomenon exhibited in
certain minerals in which they give off light, as if glow-
ing, when heated. When heated to high temperatures,
the trapped electrons are released and they give off
energy in the form of light. Used by archaeologists as a
dating technique in pottery and rock that has been pre-
viously fired.thermolysin A calcium- and zinc-containing neutral
protease isolated from certain bacteria.thermolysis An uncatalyzed bond cleavage resulting
from exposure of a compound to a raised temperature.thermonuclear energy Energy created from nuclear
fusion reactions.266 theoretical chemistry