Samarium is a chemical element with symbol
Sm and atomic number 62. It is a moderately
hard silvery metal that slowly oxidizes in
air. Being a typical member of the lanthanide
series, samarium usually assumes the oxidation
state +3. Compounds of samarium(II) are also
known, most notably the monoxide SmO, monochalcogenides
SmS, SmSe and SmTe, as well as samarium(II)
iodide. The last compound is a common reducing
agent in chemical synthesis. Samarium has
no significant biological role but is only
slightly toxic.
Samarium was discovered in 1879 by the French
chemist Paul-Émile Lecoq de Boisbaudran and
named after the mineral samarskite from which
it was isolated. The mineral itself was earlier
named after a Russian mine official, Colonel
Vassili Samarsky-Bykhovets, who thereby became
the first person to have a chemical element
named after him, albeit indirectly. Although
classified as a rare-earth element, samarium
is the 40th most abundant element in the Earth's
crust and is more common than such metals
as tin. Samarium occurs with concentration
up to 2.8% in several minerals including cerite,
gadolinite, samarskite, monazite and bastnäsite,
the last two being the most common commercial
sources of the element. These minerals are
mostly found in China, the United States,
Brazil, India, Sri Lanka and Australia; China
is by far the world leader in samarium mining
and production.
The major commercial application of samarium
is in samarium–cobalt magnets, which have
permanent magnetization second only to neodymium
magnets; however, samarium compounds can withstand
significantly higher temperatures, above 700
°C (1,292 °F), without losing their magnetic
properties, due to the alloy's higher Curie
point. The radioactive isotope samarium-153
is the active component of the drug samarium
(153Sm) lexidronam (Quadramet), which kills
cancer cells in the treatment of lung cancer,
prostate cancer, breast cancer and osteosarcoma.
Another isotope, samarium-149, is a strong
neutron absorber and is therefore added to
the control rods of nuclear reactors. It is
also formed as a decay product during the
reactor operation and is one of the important
factors considered in the reactor design and
operation. Other applications of samarium
include catalysis of chemical reactions, radioactive
dating and an X-ray laser.
== Physical properties ==
Samarium is a rare earth metal having a hardness
and density similar to those of zinc. With
the boiling point of 1794 °C, samarium is
the third most volatile lanthanide after ytterbium
and europium; this property facilitates separation
of samarium from the mineral ore. At ambient
conditions, samarium normally assumes a rhombohedral
structure (α form). Upon heating to 731 °C,
its crystal symmetry changes into hexagonally
close-packed (hcp), however the transition
temperature depends on the metal purity. Further
heating to 922 °C transforms the metal into
a body-centered cubic (bcc) phase. Heating
to 300 °C combined with compression to 40
kbar results in a double-hexagonally close-packed
structure (dhcp). Applying higher pressure
of the order of hundreds or thousands of kilobars
induces a series of phase transformations,
in particular with a tetragonal phase appearing
at about 900 kbar. In one study, the dhcp
phase could be produced without compression,
using a nonequilibrium annealing regime with
a rapid temperature change between about 400
and 700 °C, confirming the transient character
of this samarium phase. Also, thin films of
samarium obtained by vapor deposition may
contain the hcp or dhcp phases at ambient
conditions.Samarium (and its sesquioxide)
are paramagnetic at room temperature. Their
corresponding effective magnetic moments,
below 2µB, are the 3rd lowest among the lanthanides
(and their oxides) after lanthanum and lutetium.
The metal transforms to an antiferromagnetic
state upon cooling to 14.8 K. Individual samarium
atoms can be isolated by encapsulating them
into fullerene molecules. They can also be
doped between the C60 molecules in the fullerene
solid, rendering it superconductive at temperatures
below 8 K. Samarium doping of iron-based superconductors
– the most recent class of high-temperature
superconductors – allows enhancing their
transition temperature to 56 K, which is the
highest value achieved so far in this series.
== Chemical properties ==
Freshly prepared samarium has a silvery luster.
In air, it slowly oxidizes at room temperature
and spontaneously ignites at 150 °C. Even
when stored under mineral oil, samarium gradually
oxidizes and develops a grayish-yellow powder
of the oxide-hydroxide mixture at the surface.
The metallic appearance of a sample can be
preserved by sealing it under an inert gas
such as argon.
Samarium is quite electropositive and reacts
slowly with cold water and quite quickly with
hot water to form samarium hydroxide:
2 Sm (s) + 6 H2O (l) → 2 Sm(OH)3 (aq) +
3 H2 (g)Samarium dissolves readily in dilute
sulfuric acid to form solutions containing
the yellow to pale green Sm(III) ions, which
exist as [Sm(OH2)9]3+ complexes:
2 Sm (s) + 3 H2SO4 (aq) → 2 Sm3+ (aq) +
3 SO2−4 (aq) + 3 H2 (g)Samarium is one of
the few lanthanides that exhibit the oxidation
state +2. The Sm2+ ions are blood-red in aqueous
solution.
== Compounds ==
=== 
Oxides ===
The most stable oxide of samarium is the sesquioxide
Sm2O3. As many other samarium compounds, it
exists in several crystalline phases. The
trigonal form is obtained by slow cooling
from the melt. The melting point of Sm2O3
is rather high (2345 °C) and therefore melting
is usually achieved not by direct heating,
but with induction heating, through a radio-frequency
coil. The Sm2O3 crystals of monoclinic symmetry
can be grown by the flame fusion method (Verneuil
process) from the Sm2O3 powder, that yields
cylindrical boules up to several centimeters
long and about one centimeter in diameter.
The boules are transparent when pure and defect-free
and are orange otherwise. Heating the metastable
trigonal Sm2O3 to 1900 °C converts it to
the more stable monoclinic phase. Cubic Sm2O3
has also been described.Samarium is one of
the few lanthanides that form a monoxide,
SmO. This lustrous golden-yellow compound
was obtained by reducing Sm2O3 with samarium
metal at elevated temperature (1000 °C) and
pressure above 50 kbar; lowering the pressure
resulted in an incomplete reaction. SmO has
the cubic rock-salt lattice structure.
=== Chalcogenides ===
Samarium forms trivalent sulfide, selenide
and telluride. Divalent chalcogenides SmS,
SmSe and SmTe with cubic rock-salt crystal
structure are also known. They are remarkable
by converting from semiconducting to metallic
state at room temperature upon application
of pressure. Whereas the transition is continuous
and occurs at about 20–30 kbar in SmSe and
SmTe, it is abrupt in SmS and requires only
6.5 kbar. This effect results in spectacular
color change in SmS from black to golden yellow
when its crystals of films are scratched or
polished. The transition does not change lattice
symmetry, but there is a sharp decrease (~15%)
in the crystal volume. It shows hysteresis,
that is when the pressure is released, SmS
returns to the semiconducting state at much
lower pressure of about 0.4 kbar.
=== Halides ===
Samarium metal reacts with all the halogens,
forming trihalides:
2 Sm (s) + 3 X2 (g) → 2 SmX3 (s) (X = F,
Cl, Br or I)Their further reduction with samarium,
lithium or sodium metals at elevated temperatures
(about 700–900 °C) yields dihalides. The
diiodide can also be prepared by heating SmI3,
or by reacting the metal with 1,2-diiodoethane
in anhydrous tetrahydrofuran at room temperature:
Sm (s) + ICH2-CH2I → SmI2 + CH2=CH2.In addition
to dihalides, the reduction also produces
numerous non-stoichiometric samarium halides
with a well-defined crystal structure, such
as Sm3F7, Sm14F33, Sm27F64, Sm11Br24, Sm5Br11
and Sm6Br13.As reflected in the table above,
samarium halides change their crystal structures
when one type of halide atoms is substituted
for another, which is an uncommon behavior
for most elements (e.g. actinides). Many halides
have two major crystal phases for one composition,
one being significantly more stable and another
being metastable. The latter is formed upon
compression or heating, followed by quenching
to ambient conditions. For example, compressing
the usual monoclinic samarium diiodide and
releasing the pressure results in a PbCl2-type
orthorhombic structure (density 5.90 g/cm3),
and similar treatment results in a new phase
of samarium triiodide (density 5.97 g/cm3).
=== Borides ===
Sintering powders of samarium oxide and boron,
in vacuum, yields a powder containing several
samarium boride phases, and their volume ratio
can be controlled through the mixing proportion.
The powder can be converted into larger crystals
of a certain samarium boride using arc melting
or zone melting techniques, relying on the
different melting/crystallization temperature
of SmB6 (2580 °C), SmB4 (about 2300 °C)
and SmB66 (2150 °C). All these materials
are hard, brittle, dark-gray solids with the
hardness increasing with the boron content.
Samarium diboride is too volatile to be produced
with these methods and requires high pressure
(about 65 kbar) and low temperatures between
1140 and 1240 °C to stabilize its growth.
Increasing the temperature results in the
preferential formations of SmB6.
==== Samarium hexaboride ====
Samarium hexaboride is a typical intermediate-valence
compound where samarium is present both as
Sm2+ and Sm3+ ions at the ratio 3:7. It belongs
to a class of Kondo insulators, that is at
high temperatures (above 50 K), its properties
are typical of a Kondo metal, with metallic
electrical conductivity characterized by strong
electron scattering, whereas at low temperatures,
it behaves as a non-magnetic insulator with
a narrow band gap of about 4–14 meV. The
cooling-induced metal-insulator transition
in SmB6 is accompanied by a sharp increase
in the thermal conductivity, peaking at about
15 K. The reason for this increase is that
electrons themselves do not contribute to
the thermal conductivity at low temperatures,
which is dominated by phonons, but the decrease
in electron concentration reduced the rate
of electron-phonon scattering.New research
seems to show that it may be a topological
insulator.
=== Other inorganic compounds ===
Samarium carbides are prepared by melting
a graphite-metal mixture in an inert atmosphere.
After the synthesis, they are unstable in
air and are studied also under inert atmosphere.
Samarium monophosphide SmP is a semiconductor
with the bandgap of 1.10 eV, the same as in
silicon, and high electrical conductivity
of n-type. It can be prepared by annealing
at 1100 °C an evacuated quartz ampoule containing
mixed powders of phosphorus and samarium.
Phosphorus is highly volatile at high temperatures
and may explode, thus the heating rate has
to be kept well below 1 °C/min. Similar procedure
is adopted for the monarsenide SmAs, but the
synthesis temperature is higher at 1800 °C.Numerous
crystalline binary compounds are known for
samarium and one of the group-14, 15 or 16
element X, where X is Si, Ge, Sn, Pb, Sb or
Te, and metallic alloys of samarium form another
large group. They are all prepared by annealing
mixed powders of the corresponding elements.
Many of the resulting compounds are non-stoichiometric
and have nominal compositions SmaXb, where
the b/a ratio varies between 0.5 and 3.
=== Organometallic compounds ===
Samarium forms a cyclopentadienide Sm(C5H5)3
and its chloroderivatives Sm(C5H5)2Cl and
Sm(C5H5)Cl2. They are prepared by reacting
samarium trichloride with NaC5H5 in tetrahydrofuran.
Contrary to cyclopentadienides of most other
lanthanides, in Sm(C5H5)3 some C5H5 rings
bridge each other by forming ring vertexes
η1 or edges η2 toward another neighboring
samarium atom, thereby creating polymeric
chains. The chloroderivative Sm(C5H5)2Cl has
a dimer structure, which is more accurately
expressed as (η5-C5H5)2Sm(µ-Cl)2(η5-C5H5)2.
There, the chlorine bridges can be replaced,
for instance, by iodine, hydrogen or nitrogen
atoms or by CN groups.The (C5H5)− ion in
samarium cyclopentadienides can be replaced
by the indenide (C9H7)− or cyclooctatetraenide
(C8H8)2− ring, resulting in Sm(C9H7)3 or
KSm(η8-C8H8)2. The latter compound has a
similar structure to that of uranocene. There
is also a cyclopentadienide of divalent samarium,
Sm(C5H5)2 – a solid that sublimates at about
85 °C. Contrary to ferrocene, the C5H5 rings
in Sm(C5H5)2 are not parallel but are tilted
by 40°.Alkyls and aryls of samarium are obtained
through a metathesis reaction in tetrahydrofuran
or ether:
SmCl3 + 3 LiR → SmR3 + 3 LiCl
Sm(OR)3 + 3 LiCH(SiMe3)2 → Sm{CH(SiMe3)2}3
+ 3 LiORHere R is a hydrocarbon group and
Me stands for methyl.
== Isotopes ==
Naturally occurring samarium has a radioactivity
of 128 Bq/g. It is composed of four stable
isotopes: 144Sm, 150Sm, 152Sm and 154Sm, and
three extremely long-lived radioisotopes,
147Sm (half-life t1/2 = 1.06×1011 years),
148Sm (7×1015 years) and 149Sm (>2×1015
years), with 152Sm being the most abundant
(natural abundance 26.75%). 149Sm is listed
by various sources either as stable or radioactive
isotope.The long-lived isotopes,146Sm, 147Sm,
and 148Sm, primarily decay by emission of
alpha particles to isotopes of neodymium.
Lighter unstable isotopes of samarium primarily
decay by electron capture to isotopes of promethium,
while heavier ones convert through beta decay
to isotopes of europium.The alpha decay of
147Sm to 143Nd with a half-life of 1.06×1011
years serve for samarium–neodymium dating.
The half-lives of 151Sm and 145Sm are 90 years
and 340 days, respectively. All the remaining
radioisotopes have half-lives that are less
than 2 days, and the majority of these have
half-lives that are less than 48 seconds.
Samarium also has five nuclear isomers with
the most stable being 141mSm (half-life 22.6
minutes), 143m1Sm (t1/2 = 66 seconds) and
139mSm (t1/2 = 10.7 seconds).
== History ==
Detection of samarium and related elements
was announced by several scientists in the
second half of the 19th century; however,
most sources give the priority to the French
chemist Paul Émile Lecoq de Boisbaudran.
Boisbaudran isolated samarium oxide and/or
hydroxide in Paris in 1879 from the mineral
samarskite ((Y,Ce,U,Fe)3(Nb,Ta,Ti)5O16) and
identified a new element in it via sharp optical
absorption lines. The Swiss chemist Marc Delafontaine
announced a new element decipium (from Latin:
decipiens meaning "deceptive, misleading")
in 1878, but later in 1880–1881 demonstrated
that it was a mixture of several elements,
one being identical to the Boisbaudran's samarium.
Although samarskite was first found in the
remote Russian region of Urals, by the late
1870s its deposits had been located in other
places making the mineral available to many
researchers. In particular, it was found that
the samarium isolated by Boisbaudran was also
impure and contained comparable amount of
europium. The pure element was produced only
in 1901 by Eugène-Anatole Demarçay.Boisbaudran
named his element samaria after the mineral
samarskite, which in turn honored Vassili
Samarsky-Bykhovets (1803–1870). Samarsky-Bykhovets,
as the Chief of Staff of the Russian Corps
of Mining Engineers, had granted access for
two German mineralogists, the brothers Gustav
Rose and Heinrich Rose, to study the mineral
samples from the Urals. In this sense samarium
was the first chemical element to be named
after a person. Later the name samaria used
by Boisbaudran was transformed into samarium,
to conform with other element names, and samaria
nowadays is sometimes used to refer to samarium
oxide, by analogy with yttria, zirconia, alumina,
ceria, holmia, etc. The symbol Sm was suggested
for samarium; however an alternative Sa was
frequently used instead until the 1920s.Prior
to the advent of ion-exchange separation technology
in the 1950s, samarium had no commercial uses
in pure form. However, a by-product of the
fractional crystallization purification of
neodymium was a mixture of samarium and gadolinium
that acquired the name of "Lindsay Mix" after
the company that made it. This material is
thought to have been used for nuclear control
rods in some early nuclear reactors. Nowadays,
a similar commodity product has the name "samarium-europium-gadolinium"
(SEG) concentrate. It is prepared by solvent
extraction from the mixed lanthanides isolated
from bastnäsite (or monazite). Since the
heavier lanthanides have the greater affinity
for the solvent used, they are easily extracted
from the bulk using relatively small proportions
of solvent. Not all rare-earth producers who
process bastnäsite do so on a large enough
scale to continue onward with the separation
of the components of SEG, which typically
makes up only one or two percent of the original
ore. Such producers will therefore be making
SEG with a view to marketing it to the specialized
processors. In this manner, the valuable europium
content of the ore is rescued for use in phosphor
manufacture. Samarium purification follows
the removal of the europium. As of 2012, being
in oversupply, samarium oxide is less expensive
on a commercial scale than its relative abundance
in the ore might suggest.
== Occurrence and production ==
With the average concentration of about 8
parts per million (ppm), samarium is the 40th
most abundant element in the Earth's crust.
It is the fifth most abundant lanthanide and
is more common than elements such as tin.
Samarium concentration in soils varies between
2 and 23 ppm, and oceans contain about 0.5–0.8
parts per trillion. Distribution of samarium
in soils strongly depends on its chemical
state and is very inhomogeneous: in sandy
soils, samarium concentration is about 200
times higher at the surface of soil particles
than in the water trapped between them, and
this ratio can exceed 1,000 in clays.Samarium
is not found free in nature, but, like other
rare earth elements, is contained in many
minerals, including monazite, bastnäsite,
cerite, gadolinite and samarskite; monazite
(in which samarium occurs at concentrations
of up to 2.8%) and bastnäsite are mostly
used as commercial sources. World resources
of samarium are estimated at two million tonnes;
they are mostly located in China, US, Brazil,
India, Sri Lanka and Australia, and the annual
production is about 700 tonnes. Country production
reports are usually given for all rare-earth
metals combined. By far, China has the largest
production with 120,000 tonnes mined per year;
it is followed by the US (about 5,000 tonnes)
and India (2,700 tonnes). Samarium is usually
sold as oxide, which at the price of about
30 USD/kg is one of the cheapest lanthanide
oxides. Whereas mischmetal – a mixture of
rare earth metals containing about 1% of samarium
– has long been used, relatively pure samarium
has been isolated only recently, through ion
exchange processes, solvent extraction techniques,
and electrochemical deposition. The metal
is often prepared by electrolysis of a molten
mixture of samarium(III) chloride with sodium
chloride or calcium chloride. Samarium can
also be obtained by reducing its oxide with
lanthanum. The product is then distilled to
separate samarium (boiling point 1794 °C)
and lanthanum (b.p. 3464 °C).Domination of
samarium in minerals is unique. Minerals with
essential (dominant) samarium include monazite-(Sm)
and florencite-(Sm). They are very rare.Samarium-151
is produced in nuclear fission of uranium
with the yield of about
0.4% of the total number of fission events.
It is also synthesized upon neutron capture
by samarium-149, which is added to the control
rods of nuclear reactors. Consequently, samarium-151
is present in spent nuclear fuel and radioactive
waste.
== Applications ==
One of the most important applications of
samarium is in samarium–cobalt magnets,
which have a nominal composition of SmCo5
or Sm2Co17. They have high permanent magnetization,
which is about 10,000 times that of iron and
is second only to that of neodymium magnets.
However, samarium-based magnets have higher
resistance to demagnetization, as they are
stable to temperatures above 700 °C (cf.
300–400 °C for neodymium magnets). These
magnets are found in small motors, headphones,
and high-end magnetic pickups for guitars
and related musical instruments. For example,
they are used in the motors of a solar-powered
electric aircraft, the Solar Challenger, and
in the Samarium Cobalt Noiseless electric
guitar and bass pickups.
Another important application of samarium
and its compounds is as catalyst and chemical
reagent. Samarium catalysts assist decomposition
of plastics, dechlorination of pollutants
such as polychlorinated biphenyls (PCBs),
as well as the dehydration and dehydrogenation
of ethanol. Samarium(III) triflate (Sm(OTf)3,
that is Sm(CF3SO3)3), is one of the most efficient
Lewis acid catalysts for a halogen-promoted
Friedel–Crafts reaction with alkenes. Samarium(II)
iodide is a very common reducing and coupling
agent in organic synthesis, for example in
the desulfonylation reactions; annulation;
Danishefsky, Kuwajima, Mukaiyama and Holton
Taxol total syntheses; strychnine total synthesis;
Barbier reaction and other reductions with
samarium(II) iodide.In its usual oxidized
form, samarium is added to ceramics and glasses
where it increases absorption of infrared
light. As a (minor) part of mischmetal, samarium
is found in "flint" ignition device of many
lighters and torches.
Radioactive samarium-153 is a beta emitter
with a half-life of 46.3 hours. It is used
to kill cancer cells in the treatment of lung
cancer, prostate cancer, breast cancer, and
osteosarcoma. For this purpose, samarium-153
is chelated with ethylene diamine tetramethylene
phosphonate (EDTMP) and injected intravenously.
The chelation prevents accumulation of radioactive
samarium in the body that would result in
excessive irradiation and generation of new
cancer cells. The corresponding drug has several
names including samarium (153Sm) lexidronam;
its trade name is Quadramet.Samarium-149 has
high cross-section for neutron capture (41,000
barns) and is therefore used in the control
rods of nuclear reactors. Its advantage compared
to competing materials, such as boron and
cadmium, is stability of absorption – most
of the fusion and decay products of samarium-149
are other isotopes of samarium that are also
good neutron absorbers. For example, the cross
section of samarium-151 is 15,000 barns, it
is on the order of hundreds of barns for 150Sm,
152Sm, and 153Sm, and is 6,800 barns for natural
(mixed-isotope) samarium. Among the decay
products in a nuclear reactor, samarium-149
is regarded as the second most important for
the reactor design and operation after xenon-135.Samarium
hexaboride, abbreviated SmB6, has recently
been shown to be a topological insulator with
potential applications to quantum computing.
=== Non-commercial and potential applications
===
Samarium-doped calcium fluoride crystals were
used as an active medium in one of the first
solid-state lasers designed and constructed
by Peter Sorokin (co-inventor of the dye laser)
and Mirek Stevenson at IBM research labs in
early 1961. This samarium laser emitted pulses
of red light at 708.5 nm. It had to be cooled
by liquid helium and thus did not find practical
applications.Another samarium-based laser
became the first saturated X-ray laser operating
at wavelengths shorter than 10 nanometers.
It provided 50-picosecond pulses at 7.3 and
6.8 nm suitable for applications in holography,
high-resolution microscopy of biological specimens,
deflectometry, interferometry, and radiography
of dense plasmas related to confinement fusion
and astrophysics. Saturated operation meant
that the maximum possible power was extracted
from the lasing medium, resulting in the high
peak energy of 0.3 mJ. The active medium was
samarium plasma produced by irradiating samarium-coated
glass with a pulsed infrared Nd-glass laser
(wavelength ~1.05 µm).The change in electrical
resistivity in samarium monochalcogenides
can be used in a pressure sensor or in a memory
device triggered between a low-resistance
and high-resistance state by external pressure,
and such devices are being developed commercially.
Samarium monosulfide also generates electric
voltage upon moderate heating to about 150
°C that can be applied in thermoelectric
power converters.The analysis of relative
concentrations of samarium and neodymium isotopes
147Sm, 144Nd, and 143Nd allows the determination
of the age and origin of rocks and meteorites
in samarium–neodymium dating. Both elements
are lanthanides and have very similar physical
and chemical properties. Therefore, Sm–Nd
dating is either insensitive to partitioning
of the marker elements during various geological
processes, or such partitioning can well be
understood and modeled from the ionic radii
of the involved elements.The Sm3+ ion is a
potential activator for use in warm-white
light emitting diodes. It offers high luminous
efficacy due to the narrow emission bands,
however, the generally low quantum efficiency
and insufficient absorption in the UV-A to
blue spectral region hinders commercial application.In
recent years it has been demonstrated that
nanocrystalline BaFCl:Sm3+ as prepared by
a co-precipitation can serve as a very efficient
x-ray storage phosphor. The co-precipitation
leads to nanocrystallites of the order of
100-200 nm in size and their sensitivity as
x-ray storage phosphors is increased an astounding
∼500,000 times because of the specific arrangements
and density of defect centres in comparison
with microcrystalline samples prepared by
sintering at high temperature. The mechanism
is based on the reduction of Sm3+ to Sm2+
by trapping electrons that are created upon
exposure to ionizing radiation in the BaFCl
host. The 5 DJ-7 FJ f-f luminescence lines
can be very efficiently excited via the parity
allowed 4f6 →4f5 5d transition at around
417 nm. The latter wavelength is ideal for
efficient excitation by blue-violet laser
diodes as the transition is electric dipole
allowed and thus relatively intense (400 l/(mol⋅cm)).
The phosphor has potential applications in
personal dosimetry, dosimetry and imaging
in radiotherapy, and medical imaging.
== Biological role ==
Samarium salts stimulate metabolism, but it
is unclear whether this is the effect of samarium
or other lanthanides present with it. The
total amount of samarium in adults is about
50 µg, mostly in liver and kidneys and with
about 8 µg/L being dissolved in the blood.
Samarium is not absorbed by plants to a measurable
concentration and therefore is normally not
a part of human diet. However, a few plants
and vegetables may contain up to 1 part per
million of samarium. Insoluble salts of samarium
are non-toxic and the soluble ones are only
slightly toxic.When ingested, only about 0.05%
of samarium salts is absorbed into the bloodstream
and the remainder is excreted. From the blood,
about 45% goes to the liver and 45% is deposited
on the surface of the bones where it remains
for about 10 years; the balance 10% is excreted
