concentration. Glass electrodes are
used in pH measurement.
glassÜbres Melted glass drawn
into thinÜbres some 0.005 mm–0.01
mm in diameter. TheÜbres may be
spun into threads and woven into
fabrics, which are then impregnated
with resins to give a material that is
both strong and corrosion resistant.
It is used in car bodies, boat building,
and similar applications.
glauberiteA mineral consisting of
a mixed sulphate of sodium and cal-
cium, Na 2 SO 4 .CaSO 4.
Glauber’s salt *Sodium sulphate
decahydrate, Na 2 SO 4 .10H 2 O, used as
a laxative. It is named after Johann
Glauber (1604–68).
GLC(gas–liquid chromatography)
See gas chromatography.
global warming See greenhouse
effect.
globin See haemoglobin.
globular protein See protein.
globulinAny of a group of globular
proteins that are generally insoluble
in water and present in blood, eggs,
milk, and as a reserve protein in
seeds. Blood serum globulins com-
prise four types: α 1 -, α 2 -, and β-
globulins, which serve as carrier pro-
teins; and γ-globulins, which include
the immunoglobulins responsible for
immune responses.
glove boxA metal box that has
glovesÜtted to ports in its walls. It is
used to manipulate mildly radio-
active materials and in laboratory
techniques in which an inert, sterile,
dry, or dust-free atmosphere has to
be maintained.
glow discharge An electrical dis-
charge that passes through a gas at
low pressure and causes the gas to
become luminous. The glow is pro-
duced by the decay of excited atoms
and molecules.gluconic acidAn optically
active hydroxycarboxylic acid,
CH 2 (OH)(CHOH) 4 COOH. It is the car-
boxylic acid corresponding to the al-
dose sugar glucose, and can be made
by the action of certain moulds.
glucosanAny one of a class of
*polysaccharide compounds that can
be converted to glucose by hydroly-
sis. Glucosans include dextrin, starch,
and cellulose.glucose(dextrose; grape sugar)A
white crystalline sugar, C 6 H 12 O 6 , oc-
curring widely in nature. Like other
*monosaccharides, glucose is opti-
cally active: most naturally occurring
glucose is dextrorotatory. Glucose
and its derivatives are crucially im-
portant in the energy metabolism of
living organisms. Glucose is also a
constituent of many polysaccharides,
most notably starch and cellulose.
These yield glucose when broken
down, for example by enzymes dur-
ing digestion.
glucuronic acid A compound,
OC 6 H 9 O 6 , derived from the oxidation
of glucose. It is an important con-
stituent of gums and mucilages. Glu-
curonic acid can combine with
hydroxyl (–OH), carboxyl (–COOH), or
amino (–NH 2 ) groups to form a glu-
curonide. The addition of a glu-
curonide group to a molecule
(glucuronidation) generally increases
the solubility of a compound; hence
glucuronidation plays an important
role in the excretion of foreign sub-
stances.
glucuronide See glucuronic acid.glutamic acidSee amino acid.glutamineSee amino acid.
glutaric acidSee pentanedioic
acid.247 glutaric acid
g