CRC Handbook of Chemistry and Physics, 86th Edition

4-18 The Elements
to have a low acute toxic rating. Natural holmium consists of
one isotope 165 Ho, which is not radioactive. Holmium has 49
other isotopes known, all of which are radioactive. The price
of 99.9% holmium metal is about $20/g.
Hydrogen — (Gr. hydro, water, and genes, forming), H; at. wt.
1.00794(7); at. no. 1; m.p. –259.34°C; b.p. –252.87°C; t c –240.18;
density 0.08988 g/l; density (liquid) 70.8 g/l (–253°C); density
(solid) 70.6 g/l (–262°C); valence 1. Hydrogen was prepared
many years before it was recognized as a distinct substance by
Cavendish in 1766. It was named by Lavoisier. Hydrogen is the
most abundant of all elements in the universe, and it is thought
that the heavier elements were, and still are, being built from
hydrogen and helium. It has been estimated that hydrogen
makes up more than 90% of all the atoms or three quarters
of the mass of the universe. It is found in the sun and most
stars, and plays an important part in the proton-proton reaction
and carbon-nitrogen cycle, which accounts for the energy
of the sun and stars. It is thought that hydrogen is a major
component of the planet Jupiter and that at some depth in the
planet’s interior the pressure is so great that solid molecular
hydrogen is converted into solid metallic hydrogen. In 1973, it
was reported that a group of Russian experimenters may have
produced metallic hydrogen at a pressure of 2.8 Mbar. At the
transition the density changed from 1.08 to 1.3 g/cm 3 . Earlier,
in 1972, a Livermore (California) group also reported on a
similar experiment in which they observed a pressure-volume
point centered at 2 Mbar. It has been predicted that metallic
hydrogen may be metastable; others have predicted it would
be a superconductor at room temperature. On earth, hydrogen
occurs chiefly in combination with oxygen in water, but it
is also present in organic matter such as living plants, petroleum,
coal, etc. It is present as the free element in the atmosphere,
but only to the extent of less than 1 ppm by volume. It
is the lightest of all gases, and combines with other elements,
sometimes explosively, to form compounds. Great quantities
of hydrogen are required commercially for the fixation of nitrogen
from the air in the Haber ammonia process and for the
hydrogenation of fats and oils. It is also used in large quantities
in methanol production, in hydrodealkylation, hydrocracking,
and hydrodesulfurization. It is also used as a rocket
fuel, for welding, for production of hydrochloric acid, for the
reduction of metallic ores, and for filling balloons. The lifting
power of 1 ft 3 of hydrogen gas is about 0.076 lb at 0°C, 760
mm pressure. Production of hydrogen in the U.S. alone now
amounts to about 3 billion cubic feet per year. It is prepared
by the action of steam on heated carbon, by decomposition of
certain hydrocarbons with heat, by the electrolysis of water,
or by the displacement from acids by certain metals. It is also
produced by the action of sodium or potassium hydroxide on
aluminum. Liquid hydrogen is important in cryogenics and in
the study of superconductivity, as its melting point is only a
20°C above absolute zero. Hydrogen consists of three isotopes,
most of which is 1 H. The ordinary isotope of hydrogen, H, is
known as protium. In 1932, Urey announced the discovery of
a stable isotope, deuterium ( 2 H or D) with an atomic weight of
2. Deuterium is present in natural hydrogen to the extent of
0.015%. Two years later an unstable isotope, tritium ( 3 H), with
an atomic weight of 3 was discovered. Tritium has a half-life
of about 12.32 years. Tritium atoms are also present in natural
hydrogen but in much smaller proportion. Tritium is readily
produced in nuclear reactors and is used in the production of
the hydrogen bomb. It is also used as a radioactive agent in
making luminous paints, and as a tracer. On August 27, 2001
Russian, French, and Japanese physicists working at the Joint
Institute for Nuclear Research near Moscow reported they
had made “super-heavy hydrogen”, which had a nucleus with
one proton and four neutrons. Using an accelerator, they used
a beam of helium-6 nuclei to strike a hydrogen target, which
resulted in the occasional production of a hydrogen-5 nucleus
plus a helium-2 nucleus. These unstable particles quickly
disintegrated. This resulted in two protons from the He-2, a
triton, and two neutrons from the H-5 breakup. Deuterium
gas is readily available, without permit, at about $1/l. Heavy
water, deuterium oxide (D 2 O), which is used as a moderator
to slow down neutrons, is available without permit at a cost of
6c to $1/g, depending on quantity and purity. About 1000 tons
(4,400,000 kg) of deuterium oxide (heavy water) are now in
use at the Sudbury (Ontario) Neutrino Observatory. This observatory
is taking data to provide new revolutionary insight
into the properties of neutrinos and into the core of the sun.
The heavy water is on loan from Atomic Energy of Canada,
Ltd. (AECL). The observatory and detectors are located 6800
ft (2072 m) deep in the Creighton mine of the International
Nickel Co., near Sudbury. The heavy water is contained
in an acrylic vessel, 12 m in diameter. Neutrinos react with
the heavy water to produce Cherenkov radiation. This light
is then detected with 9600 photomultiplier tubes surrounding
the vessel. The detector laboratory is immensely clean to
reduce background radiation, which otherwise hide the very
weak signals from neutrinos. Quite apart from isotopes, it has
been shown that hydrogen gas under ordinary conditions is a
mixture of two kinds of molecules, known as ortho- and parahydrogen,
which differ from one another by the spins of their
electrons and nuclei. Normal hydrogen at room temperature
contains 25% of the para form and 75% of the ortho form. The
ortho form cannot be prepared in the pure state. Since the two
forms differ in energy, the physical properties also differ. The
melting and boiling points of parahydrogen are about 0.1°C
lower than those of normal hydrogen. Consideration is being
given to an entire economy based on solar- and nuclear-generated
hydrogen. Located in remote regions, power plants
would electrolyze sea water; the hydrogen produced would
travel to distant cities by pipelines. Pollution-free hydrogen
could replace natural gas, gasoline, etc., and could serve as a
reducing agent in metallurgy, chemical processing, refining,
etc. It could also be used to convert trash into methane and
ethylene. Public acceptance, high capital investment, and the
high present cost of hydrogen with respect to present fuels
are but a few of the problems facing establishment of such an
economy. Hydrogen is being investigated as a substitute for
deep-sea diving applications below 300 m. Hydrogen is readily
available from air product suppliers.
Indium — (from the brilliant indigo line in its spectrum), In; at. wt.
114.818(3); at. no. 49; m.p. 156.60°C; b.p. 2072°C; sp. gr. 7.31
(20°C); valence 1, 2, or 3. Discovered by Reich and Richter, who
later isolated the metal. Indium is most frequently associated
with zinc materials, and it is from these that most commercial
indium is now obtained; however, it is also found in iron,
lead, and copper ores. Until 1924, a gram or so constituted the
world’s supply of this element in isolated form. It is probably
about as abundant as silver. About 4 million troy ounces of
indium are now produced annually in the Free World. Canada
is presently producing more than 1,000,000 troy ounces annually.
The present cost of indium is about $2 to $10/g, depending
on quantity and purity. It is available in ultrapure form.
Indium is a very soft, silvery-white metal with a brilliant lus-