Derivatives are known with substitutes at various posi-
tions on the ring named a, b, c, d, etc. Heme b, derived
from PROTOPORPHYRIN IX, is the most frequently
occurring heme.
hemerythrin A dioxygen-carrying protein from
marine invertebrates, containing an oxo-bridged DINU-
CLEARiron center.
hemileptic SeeHOMOLEPTIC.
hemochromatosis A genetic condition of massive
iron overload leading to cirrhosis or other tissue dam-
age, attributable to iron.
hemocyanin A dioxygen-carrying protein (from
invertebrates, e.g., arthropods and mollusks), contain-
ing dinuclear type 3 copper sites.
See alsoNUCLEARITY; TYPE1, 2, 3COPPER.
hemoglobin A dioxygen-carrying HEME protein of
red blood cells, generally consisting of two alpha and
two beta SUBUNITs, each containing one molecule of
PROTOPORPHYRIN IX.
Henderson-Hasselbach equation An equation of
the form
pH = pKa–lg([HA]/[A–])for calculation of the pH of solutions where the ratio
[HA]/[A–] is known.
Henry’s law At equilibrium, the concentration of a
gas dissolved in any solvent is proportional to its par-
tial pressure.
herbicide A chemical pesticide that controls or
destroys unwanted plants, weeds, or grasses.
hertz A unit for expressing frequency (f). One hertz
equals one cycle per second.
Herzberg, Gerhard (1904–1999) GermanChemist
Gerhard Herzberg was born in Hamburg, Germany,
on December 25, 1904. He received early schooling
in Hamburg and then studied physics at the Darm-
stadt Institute of Technology, where he obtained a
doctoral degree in 1928. From 1928 to 1930 he con-
ducted postdoctorate work at the University of Göt-
tingen and the University of Bristol. He was married
in 1929 to Luise Herzberg (neé Oettinger) (widowed
in 1971) and had two children. In 1930 he was
appointed Privatdozent (lecturer) and senior assistant
in the physics department of the Darmstadt Institute
of Technology.
After leaving Germany in 1935, he became a guest
lecturer at the University of Saskatchewan (Saskatoon,
Canada) with financial support by the Carnegie Foun-
dation, and he later became research professor of
physics, staying there until 1945.
From 1945 to 1948 he served as a professor of
spectroscopy at the Yerkes Observatory of the Univer-
sity of Chicago, but he returned to Canada in 1948 as
principal research officer and then as director of the
division of physics at the National Research Council.
In 1955 he became director of the division of pure
physics, a position he held until 1969, when he was
appointed as distinguished research scientist in the
recombined division of physics.
Herzberg contributed to the field of atomic and
molecular spectroscopy, where he and his colleagues
determined the structures of a large number of
diatomic and polyatomic molecules, the structures of
free radicals, and the identification of certain molecules
in planetary atmospheres, in comets, and in interstellar
space. In 1971 he was awarded the Nobel Prize in
chemistry “for his contributions to the knowledge of
electronic structure and geometry of molecules, particu-
larly free radicals.”
He served in many organizations and received
several awards. He was vice president of the Interna-
tional Union of Pure and Applied Physics (1957–63),
president of the Canadian Association of Physicists
(1956–57), and president of the Royal Society of
Canada (1966–67). He was elected a fellow of the
Royal Society of Canada (1939) and Royal Society of
London (1951). He was Bakerian Lecturer of the
Royal Society of London (1960) and recipient of their
Royal Medal in 1971. He was George Fischer Baker
Non-Resident Lecturer in Chemistry at Cornell Uni-126 hemerythrin