الفهرس 
Gravimetric MethodsOnly 14 pages are availabe for public view
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Abstract
The larger group of elements in the sexth periodic
table known as the rare earths or lanthanides includes 15
elements: lanthanum (La), cerium (Ce), praseodymium (Pr),
neodymium (Nd), promethium (pm), samarium (Sm), europium
(Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy),holmium
(Ho), erbium (Er},thulium (Tm), ytterbium (rlJ) and lutetium
(Lu). In nature the lantb.anides occur with yttrium (Y)
which has a very si8ilar chemical properties and so both
are often discussed togother. Since their discovery in
1794 in the mineral ytterbite (later renamed gadolinite),
the lanthanides has attra~ted the inteEest of many investigators
for over 138 years.
Many chemical, magnetic and spectroscopic data
on the electronic structure Gf the lanthani~es in the
atomic and ionic states have been reported1 •2 •3. It is
firmely established that the unusual change in the properties
within the lanthanides fgmily is due to the order
of :fillinG of the electron shell. Because of the peculair
nature of the wave function of the lanthanides, the filling
of the 4f shells is energetically more advantageous than
the filling .of the eutermost 5d and 6p shells