Potassium aluminum sulfate-dodecahydrate

KA1(S04)2-12H20 potassium aluminum sulfate dodecahydrate (alum)... 

HfSi2 hafnium silicide 12401-56-8 25,00 7.6000 1 1961 KAIH24O20S2 potassium aluminum sulfate dodecahydrate 7784-24-9 25.00 1.7200 1... 

The picture of the closest sphere packing for the alum crystal (see Fig. 4.4) correlates to a rough educational reduction. The expert knows that the substance potassium aluminum sulfate dodecahydrate is composed of hydrated potassium ions, whose octahedral and tetrahedral interstices are filled with aluminum ions and with sulfate ions. This model concept may be introduced later and can be used in future lessons. Nevertheless, it is considered reasonable, at first, to introduce the alum particles and to choose reduced concrete models. 

In this experiment you will prepare potassium aluminum sulfate dodecahydrate, KAl(804)2 121120, a double salt, starting with aluminum metal. Aluminum metal reacts rapidly with a hot aqueous solution of potassium hydroxide, KOH, to produce a soluble potassium aluminate salt. 

Rubidium is recovered from its ore lepidolite or pollucite. Mineral lepidolite is a lithium mica having a composition KRbLi(OH,F)Al2Si30io. The ore is opened by fusion with gypsum (potassium sulfate) or with a mixture of barium sulfate and barium carbonate. The fused mass is extracted with hot water to leach out water-soluble alums of cesium, rubidium, and potassium. The solution is filtered to remove insoluble residues. Alums of alkali metals are separated from solution by fractional crystallization. Solubility of rubidium alum or rubidium aluminum sulfate dodecahydrate, RbAl(S04)2 I2H2O falls between potassium and cesium alum. 

Figure 2.38 Effect of flow rate on the growth rate of single crystal of potassium aluminum sulfate to dodecahydrate.

Cube alum Kalinite Potash alum Potassium alum Potassium aluminum sulfate Sulfuric acid, aluminum potassium salt (2 1 1), dodecahydrate... 

For the student interested in crystal growth, potassium aluminum sulfate, also called alum, is a salt available in most pharmacies. It will form single crystals relatively easily from a supersaturated solution. Alum crystals are octahedral in shape and colorless. The related compound, chromium aluminum sulfate dodecahydrate, called chrome alum, forms dark-purple octahedral crystals. Mixing various proportions of supersaturated alum and chrome alum solutions allows the growth of mixed crystals that resemble amethysts in color. (The more alum in the mix, the lighter the purple color of the crystal.) Take the powder patterns of crnshed pnre alum and crushed pure chrome alum, and a mixture of the two compounds. After yon have grown some mixed crystals, crush some and take their powder pattern. Is it different from the two pure materials and from the mixture Explain your observations. 

Aluminum potassium sulfate (uh-LOO-min-um po-TASS-see-um sul-fate) is also known as aluminum potassium sulfate dodecahydrate, potash alum, potassium alum, and kalinite. It normally occurs in the form of the dodecahydrate, meaning that each molecule of the compound is associated with twelve molecules of water. The formula of the hydrate is KAl(S04)2-iaH20. In this form, it occurs as white odorless crystals. The compound gradually loses its water of hydration when heated, giving up the first nine molecules of water at 64.5°C (i48°F), and the remaining three molecules of water at about 20o°C (392°F). 

Alum. See Potassium alum dodecahydrate Potassium alum anhydrous Sodium alum Aluminum sulfate Aiumaiux 39. See Alumina Alum, ammonium. See Ammonium alum Alum carmine. See Carmine (Coccus cacti)... 

Alum (aluminum potassium sulfate dodecahydrate) is prepared from the mineral bauxite, a hydrated aluminum oxide, and sulfuric acid. Ammonium alum is predominant in the market due to its low cost. It is a powerfid astringent in acidic solutions, and is slightly antiseptic. As an astringent it is used in concentrations ranging fium 0.5% to 5.0%. 

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