Published 1982
13
Lithium, Sodium, and Potassium
D. KNUDSEN AND G. A. PETERSON
University of Nebraska
Lincoln, Nebraska
P.F.PRATT
University of California
Riverside, California
13-1 GENERAL INTRODUCTION
13-1.1 Properties of Alkali Metals
The elements Li, Na, and K belong to group IA of the periodic table and are
part of the group known as the alkali metals. They are characterized by a
single electron in their outermost shell. This electron is easily lost, and they
readily form stable monovalent ions. Table 13-1 shows the general properties of Li, Na, and K.
Most salts of these metals are readily soluble in water. This has made
chemical separation in quantitative procedures relatively difficult and tedious. Certain complex compounds of each have been used in developing
quantiative analytical techniques. These compounds include sodium zinc
uranyl acetate [NaZn(U0 2MOAc)go6H 2 0], which is a yellow precipitate
that is insoluble in water, and hexanitrocobaltate(III) [K 2 Na[Co(N0 2)6]], a
K salt that also precipitates in aqueous solution. Other complex agents, including chloroplatinates, have been used to separate Li, Na, and K compounds when they are present in the same solution.
13-1.2 Mineralogy of Lithium, Sodium, and Potassium in Soils
Compounds of Na and K are widely distributed in nature, and the
amounts found in soils depend on the parent material composition and the
weathering state of the soil in question. Lithium-containing minerals are
much rarer than either Na or K minerals in soils.
There are at least six Li-containing minerals that could be present in
soil materials. None of them are abundant and are generally present in only
trace amounts. Some of them are silicates, such as spodumene [LiAl(Sb06)]
and lepidolite [K 2Li J AI J (AISi J O,oMOH,F)4]' Lithiophorite, which has
Copyright 1982 © ASA-SSSA, 677 S. Segoe Rd., Madison, WI 53711, USA. Methods of Soil
Analysis, Part 2. Chemical and Microbiological Properties-Agronomy Monograph no. 9
(2nd Edition).
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