to the air and the mixture contains
hydrogen. The gas is used as a fuel in
some industrial processes.
product See chemical reaction.
progesterone A hormone, produced primarily by the corpus luteum of the ovary but also by the
placenta, that prepares the inner lining of the uterus for implantation of
a fertilized egg cell. If implantation
fails, the corpus luteum degenerates
and progesterone production ceases
accordingly. If implantation occurs,
the corpus luteum continues to secrete progesterone, under the inÛuence of luteinizing hormone and
prolactin, for several months of pregnancy, by which time the placenta
has taken over this function. During
pregnancy, progesterone maintains
the constitution of the uterus and
prevents further release of eggs from
the ovary. Small amounts of progesterone are produced by the testes. See
also progestogen.
progestogen One of a group of
naturally occurring or synthetic hormones that maintain the normal
course of pregnancy. The best known
is *progesterone. In high doses
progestogens inhibit secretion of
luteinizing hormone, thereby preventing ovulation, and alter the consistency of mucus in the vagina so
that conception tends not to occur.
They are therefore used as major
constituents of oral contraceptives.
projection formula A convention for representing the threedimensional structure of a molecule
in two dimensions. See fischer projection; newman projection;
sawhorse projection.
prolactin (lactogenic hormone; luteotrophic hormone; luteotrophin) A
hormone produced by the anterior
pituitary gland. In mammals it stimulates the mammary glands to produce milk and the corpus luteum of
the ovary to secrete the hormone
*progesterone.
proline See amino acid.
promethium Symbol Pm. A soft silvery metallic element belonging to
the *lanthanoids; a.n. 61; r.a.m. 145;
r.d. 7.26 (20°C); m.p. 1080°C; b.p.
2460°C. The only naturally occurring
isotope, promethium–147, has a halflife of only 2.52 years. Eighteen other
radioisotopes have been produced,
but they have very short half-lives.
The only known source of the element is nuclear-waste material.
Promethium–147 is of interest as a
beta-decay power source but the
promethium–146 and –148, which
emit penetrating gamma radiation,
must Ürst be removed. It was discovered by J. A. Marinsky, L. E. Glendenin, and C. D. Coryell in 1947.
A
• Information from the WebElements site
promoter A substance added to a
catalyst to increase its activity.
proof A measure of the amount of
alcohol (ethanol) in drinks. Proof
spirit contains 49.28% ethanol by
weight (about 57% by volume). Degrees of proof express the percentage
of proof spirit present, so 70° proof
spirit contains 0.7 × 57% alcohol.
1,2-propadiene (allene) A colourless gas, CH 2 CCH 2 ; r.d. 1.79; m.p.
–136°C; b.p. –34.5°C. Propadiene may
be prepared from 1,3-dibromopropane (CH 2 BrCHCH 2 Br) by the action of zinc dust. See also allenes.
propanal (propionaldehyde) A
colourless liquid *aldehyde,
C 2 H 5 CHO; m.p. –81°C; b.p. 48.8°C.
propane A colourless gaseous hydrocarbon, C 3 H 8 ; m.p. –190°C; b.p.
–42°C. It is the third member of the
*alkane series and is obtained from
439
propane
p
www.AzShimi.ir www.AzShimi.com
hydrogen. The gas is used as a fuel in
some industrial processes.
product See chemical reaction.
progesterone A hormone, produced primarily by the corpus luteum of the ovary but also by the
placenta, that prepares the inner lining of the uterus for implantation of
a fertilized egg cell. If implantation
fails, the corpus luteum degenerates
and progesterone production ceases
accordingly. If implantation occurs,
the corpus luteum continues to secrete progesterone, under the inÛuence of luteinizing hormone and
prolactin, for several months of pregnancy, by which time the placenta
has taken over this function. During
pregnancy, progesterone maintains
the constitution of the uterus and
prevents further release of eggs from
the ovary. Small amounts of progesterone are produced by the testes. See
also progestogen.
progestogen One of a group of
naturally occurring or synthetic hormones that maintain the normal
course of pregnancy. The best known
is *progesterone. In high doses
progestogens inhibit secretion of
luteinizing hormone, thereby preventing ovulation, and alter the consistency of mucus in the vagina so
that conception tends not to occur.
They are therefore used as major
constituents of oral contraceptives.
projection formula A convention for representing the threedimensional structure of a molecule
in two dimensions. See fischer projection; newman projection;
sawhorse projection.
prolactin (lactogenic hormone; luteotrophic hormone; luteotrophin) A
hormone produced by the anterior
pituitary gland. In mammals it stimulates the mammary glands to produce milk and the corpus luteum of
the ovary to secrete the hormone
*progesterone.
proline See amino acid.
promethium Symbol Pm. A soft silvery metallic element belonging to
the *lanthanoids; a.n. 61; r.a.m. 145;
r.d. 7.26 (20°C); m.p. 1080°C; b.p.
2460°C. The only naturally occurring
isotope, promethium–147, has a halflife of only 2.52 years. Eighteen other
radioisotopes have been produced,
but they have very short half-lives.
The only known source of the element is nuclear-waste material.
Promethium–147 is of interest as a
beta-decay power source but the
promethium–146 and –148, which
emit penetrating gamma radiation,
must Ürst be removed. It was discovered by J. A. Marinsky, L. E. Glendenin, and C. D. Coryell in 1947.
A
• Information from the WebElements site
promoter A substance added to a
catalyst to increase its activity.
proof A measure of the amount of
alcohol (ethanol) in drinks. Proof
spirit contains 49.28% ethanol by
weight (about 57% by volume). Degrees of proof express the percentage
of proof spirit present, so 70° proof
spirit contains 0.7 × 57% alcohol.
1,2-propadiene (allene) A colourless gas, CH 2 CCH 2 ; r.d. 1.79; m.p.
–136°C; b.p. –34.5°C. Propadiene may
be prepared from 1,3-dibromopropane (CH 2 BrCHCH 2 Br) by the action of zinc dust. See also allenes.
propanal (propionaldehyde) A
colourless liquid *aldehyde,
C 2 H 5 CHO; m.p. –81°C; b.p. 48.8°C.
propane A colourless gaseous hydrocarbon, C 3 H 8 ; m.p. –190°C; b.p.
–42°C. It is the third member of the
*alkane series and is obtained from
439
propane
p
www.AzShimi.ir www.AzShimi.com