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• Richard Willis (Owner)

XML

<?xml version="1.0" encoding="UTF-8"?>
<material name="ALKALI" descrip="" generic="0" rawmineral="1" searchkey="" loi="0.00">
<families>
<family name="Raw Mineral"/>
</families>
<notes>
<note>A term applied to the soluble hydroxides of cesium (Cs), francium (Fr), lithium (Li),&lt;BR&gt;
potassium (K), rubidium (Rb), and sodium (Na) &amp;#151; known as &lt;B&gt;&lt;I&gt;alkali metals&lt;/I&gt;&lt;/B&gt;; or of barium (Ba), beryllium (Be), calcium (Ca), magnesium (Mg), radium (Ra), and strontium (Sr) &amp;#151; known as &lt;B&gt;&lt;I&gt;alkaline-earth metals&lt;/I&gt;&lt;/B&gt;. As well, the term \'alkali\' is applied to ammonium hydroxides (which is to say any salts of the alkali metals or alkaline-earth metals containing NH&lt;FONT SIZE=2&gt;&lt;SUB&gt;4&lt;/SUB&gt;&lt;/FONT&gt;OH).&lt;BR&gt;
The term \'alkali\' was originally applied to the ashes of burned sodium- and/or potassium-bearing plants (&amp;#147;saltwort&amp;#148;, such as kelp of beaches and moss of marshes) from which the oxides of sodium and potassium could be leached (usually by boiling in water to a thick syrupy brine). Earlier still, alkalies were leached from desert earths rich in the alkaline elements. Clay and glaze recipes from antiquity to present times abound which call for exotic ingredients such as finely sifted beach sand, ash o
f seaweed, ash of bog moss, ash of wine lees, soda ash, potash, etc., indicating sources for alkaline substances. &lt;B&gt;&lt;I&gt;&amp;#147;Natural alkali&amp;#148;&lt;/I&gt; &lt;/B&gt;is the mineral form of soda ash, occurring usually as &lt;B&gt;&lt;I&gt;trona&lt;/I&gt;&lt;/B&gt; &lt;B&gt;&lt;I&gt;(Na&lt;FONT SIZE=2&gt;&lt;SUB&gt;2&lt;/SUB&gt;&lt;/FONT&gt;CO&lt;FONT SIZE=2&gt;&lt;SUB&gt;3&lt;/SUB&gt;&lt;/FONT&gt;, NaHCO&lt;FONT SIZE=2&gt;&lt;SUB&gt;3&lt;/SUB&gt;&lt;/FONT&gt;, 2H&lt;FONT SIZE=2&gt;&lt;SUB&gt;2&lt;/SUB&gt;&lt;/FONT&gt;O)&lt;/I&gt;&lt;/B&gt;. Alkalies are the strong bases that turn litmus paper from red to blue and convert acids to neutral salts, and they are su
fficiently caustic that when in concentrated form are corrosive to organic tissues. What this signifies within the context of ceramics is that alkalies are strong fluxing agents (though at distinct temperatures), reacting strongly with silica (an acid-behaving substance) to effectively lower its melting temperature and thereby its fusion point. &lt;FONT SIZE=2&gt;see &lt;B&gt;&lt;I&gt;flux&lt;/I&gt;&lt;/B&gt;&lt;/FONT&gt;&lt;BR&gt;
With respect to clay and glaze recipes, major sources for the water-insoluble forms of the alkali oxides (especially Na&lt;FONT SIZE=2&gt;&lt;SUB&gt;2&lt;/SUB&gt;&lt;/FONT&gt;O, K&lt;FONT SIZE=2&gt;&lt;SUB&gt;2&lt;/SUB&gt;&lt;/FONT&gt;O, and CaO) are commercially graded feldspars, usually labeled simply &amp;#147;soda feldspar&amp;#148;, &amp;#147;pot feldspar&amp;#148;, &amp;#147;cal feldspar&amp;#148;, etc.&lt;BR&gt;
&lt;B&gt;alkali metals&lt;BR&gt;
&lt;/B&gt;The alkali metals are so called because they are the metals which form alkalies (i.e., strong bases capable of neutralizing acids) when they combine with other elements. They are the most chemically active of all metals, reacting rapidly and violently with air and water (i.e., in a strongly oxidizing ambiance) &amp;#151; because of this, they never occur alone in nature, but rather as members of simple and complex molecular compounds, mainly as oxides and minerals (&lt;FONT SIZE=2&gt;see &lt;B&gt;&lt;I&gt;feldspar&lt;/I&gt;&lt;/B&gt;&lt;/F
ONT&gt;). Alkali metals bear little resemblance to the more familiar metals such as iron and copper, since they are silver-white in color, malleable, and soft enough to cut with a knife; and though they serve well as color-enhancers they serve poorly as colorants, and less still for metallic lusters.&lt;BR&gt;
&lt;B&gt;alkaline-earth metals&lt;BR&gt;
&lt;/B&gt;The inclusion of &amp;#147;earth&amp;#148; to designate these metals came about during the Middle Ages when alchemists called &amp;#147;earths&amp;#148; all substances that were insoluble in water and unchanged by fire. Calcium-rich earths, such as lime, and any others that bore a resemblance to soda ash and potash (the then well-known alkalines) were called alkaline earths; and by the early 1800s when it was discovered that the earths, formerly regarded as elements, were in fact compounds of a metal and oxygen (i.e.,
oxides) those metals whose oxides comprise the alkaline earths became known as the &amp;#147;alkaline-earth metals&amp;#148;.&lt;BR&gt;
These earths are greyish white in color, and are malleable but vary widely in hardness &amp;#151; beryllium is hard enough to cut glass; while barium is as soft as lead. Their melting points are generally higher than those of the alkali metals. The elements of these alkaline-earths readily combine with most oxides and many non-metals and thus never occur as pure, isolated, metals in nature. Magnesium and calcium are by far the more abundant alkaline-earth elements in the crust of the Earth. That salt, ergo sodi
um, so dominates designations of alkali as a property/substance is testified to by such often found synonyms as &amp;#147;Alkali Flat&amp;#148; or &amp;#147;Salt Flat&amp;#148; for dry sea beds.&lt;BR&gt;

</note>
</notes>
</material>

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