Alkali aluminum silicates

These natural minerals are alkali aluminum silicates and have been used as molecular sieves and cation exchangers. Recently they have been used to control some organic photochemical reactions, du Pont chemists1 have prepared lithiated zeolites by treatment of sodium aluminum silicates such as zeolite 13X with LiNO,. These silicates, designated Li-X and Li-Y, can effect rearrangement of a-alkyl-deoxybenzoins top-alkylbenzophenones in nearly quantitative yield. Thus photolysis... 

Dr. Tropsch proposed to open up" feldspar, an alkali aluminum silicate, to produce an alumino-silicate catalyst. He had a reference saying feldspars could be opened" by heating the feldspar with lime and calcium chloride followed by acid leaching. This gave encouraging results and evolved into... 

CAS 1318-02-1 EINECS/ELINCS 215-283-8 Synonyms Aluminosilicates, zeolites Definition Hydrated alkali aluminum silicate Formuia NajO AI2O3 xSiOj yHjO Properties Dens. 0.58-0.75 pH 5-12 Toxicoiogy Irritant mutagen TSCA listed Storage Hygroscopic... 

No aluminum silicates of alkali metals are known in which the A1+3 R+1 ratio is less than 1 1. 

It is further shown that the theory requires that no stable basic silicates of divalent metals exist, and that in aluminum silicates of alkali metals there should be at least one aluminum ion for every alkali ion. 

The mineral petalite was mined as an ore in Sweden. In 1817 Johan August Arfwedson (1792—1841) analyTed this new mineral. After identifying several compounds in the ore, he realized there was a small percentage of the ore that could not be identified. After applying more analytical procedures, he determined it was a new alkali. It turned out that petalite contains hthium aluminum silicate, LiAllSi O lj. In 1818 the first lithium metal was prepared independently by two scientists, Sir Humphry Davy (1778—1892) and W.T. Brande (1788—1866). Lithium was discovered at a time in the early nineteenth century when numerous new elements were discovered and identified by other scientists. Many of these newly named elements were predicted by the use of the periodic table of the chemical elements. 

The term alumen plumosum has had a long association with asbestos. Alumen (= alum) is a general term for naturally occurring hydrous alkali aluminum sulfates. These are efflorescent mineral materials of fibrous, feathery appearance. Confusion with the more durable silicate composition asbestos was not settled until 1741, by Tourneforte following a visit to asbestos deposits in Asia Minor. 

It was noticed in some instances that alkali-metal impurities in alumina, or in the ceramic honeycombs, adversely influence the catalyst activity. For example, spodumene (lithium aluminum silicate) was found unsuitable for use as catalyst support, although it had good thermal properties. 

The natural clay minerals are hydrous aluminum silicates with iron or magnesium replacing aluminum wholly or in part, and with alkali or alkaline earth metals present as essential constituents in some others. Their acidic properties and natural abundance have favored their use as catalysts for cracking of heavy petroleum fractions. With the exception of zeolites and some specially treated mixed oxides for which superacid properties have been claimed, the acidity as measured by the color changes of absorbed Hammett bases is generally far below the superacidity range. They are inactive for alkane isomerization and cracking below 100 °C and need co-acids to reach superacidity. 

Exsolution The unmixing of an initially homogeneous substance into two or more separate crystalline substances. For example, at 1000 °C and one bar pressure, sodium and potassium can readily substitute for each other in the crystalline structure of the aluminum silicate mineral alkali feldspar to form (Na,K)AlSi30g. At much lower temperatures, the sizes of the sodium and potassium atoms are too dissimilar for the crystalline structure to remain stable and the alkali feldspar separates (exsolves) into NaAlSisOg and KAlSisOg components (Klein, 2002), 143. 

Bentonite occurs commercially as powders ranging in colors and tints from off white to pale brown to gray depending on the cations present in natural deposits. It comprises natural smectite clays consisting primarily of colloidal hydrated aluminum silicates of the montmorillonite or hectorite type of minerals with varying quantities of alkalies, alkaline earths, and iron. It is insoluble in water, in alcohol, in dilute acids, and in alkalies. 

Sodium Aluminosilicate occurs as a fine, white, amorphous powder, or as beads. It is a series of hydrated sodium aluminum silicates having Na20 Al203 Si02 molar ratios of approximately 1 1 13, respectively. It is insoluble in water and in alcohol and other organic solvents, but at 80° to 100°, it is partially soluble in strong acids and solutions of alkali hydroxides. 

Hydrated magnesium silicate (Talc, 3Mg0 4Si02 H20, CAS No. 14807-96-6) is a magnesium silicate commonly referred to as "soapstone". It is obtained from natural sources and may contain a small amount of aluminum silicate. It is composed of MgO (31.7%), Si02 (63.5%), and H2O (4.8%). It is a crystalline nonhygroscopic, odorless, tasteless powder which is practically insoluble in water, dilute mineral acids, dilute solutions of alkali halides, and alkaline hydroxides but is soluble in hot concentrated sulfuric acid. 

The authors summarized the results of the soda reaction test as follows For the high-silica samples the reaction products were identified as nepheline and sodium aluminum silicate (3 2 4). The amount of nepheline decreased with increasing alumina content, whereas the amount of (3 2 4) compound increased. The lack of silica in the high alumina samples permits the free alumina not tied up as a sodium aluminum silicate to react with the alkali to form beta-alumina. Higher amounts of soda produce sodium aluminates. 

The 90% alumina refractory showed a sharp drop in the amount of alpha-alumina present as the temperature was increased. The depletion of alpha-alumina does not occur unless excess soda is available and the temperature is above 2000°F, or unless the amount of SiOz present is not sufficient to tie up the soda as a sodium aluminum silicate. Finally, the free alumina existent in the lower silica-containing samples is depleted by the formation of beta-alumina and alkali aluminate. 

One of the greatest chemists of the 19th century was Jons Jakob Berzelius (1779-1848) of Sweden. In 1817, Berzelius put one of his assistants, Swedish chemist Johan August Arfwedson (1792-1841), to work analyzing the mineral petalite. Arfwedson could account for 96 percent of petalite s content, but the remaining 4 percent was a mystery. By 1818, Berzelius and Arfwedson had concluded that petalite must contain an unknown alkali metal. Petalite s composition proved to be lithium aluminum silicate, and Arfwedson is acknowledged as lithium s discoverer. The name lithium comes from the Greek word... 

Alkali metal hydroxides, dissolution rate effect, 521-523f Alkoxides, formation of uniform precipitates, 451-464 Aluminum, silicic acid effect on adsorption in food, 612/ 613 Aluminum in biological systems, 604, 605f, 606 Aluminum-modified silica sol, formation, 62, 63/ Aluminum-silicon interactions in biology,... 

Other useful coagulating agents are ferric sulfate and activated silica. Ferric hydroxide is gelatinous like aluminum hydroxide, and the chemistry is analogous. The coagulating effect of activated silica is due to the formation of gelatinous alkali metal silicates (Bunce, 1994). 

Synonyms Aluminosilicic acid, sodium salt Aluminum sodium silicate Silicic acid, aluminum sodium salt Sodium aluminosilicate Sodium aluminum silicate Sodium feldspar Zeolite Zeolites Definition Series of hydrated sodium aluminum silicates produced by reaction of sodium silicate and kaolinite clay Formula NajO AI2O3 SiOa with mole ratio = 1 1 13.2 Properties Wh. fine amorphous powd. or beads, odorless and tasteless insol. in water, alcohol, org. soivs. partly sol. in strong acids and alkali hydroxides 80-100 C pH 6.5-10.5 (20% slurry)... 

It was clear that a new alkali metal had been discovered. Arfwedson investigated and described several of its compounds but failed in his attempts to isolate the element in metallic form. As this new alkali was first found in the mineral kingdom -unhke the common water-soluble sodium and potassium compounds - Berzelius and Arfwedson gave the new element the name lithion, from stone . The mineral petalite is nowadays known as lithium aluminum silicate, liAlJSi OjJ. ... 

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