Sulfite, aluminum

Sulfur dioxide is introduced into a suspension of Al(OH) 3 in water until a clear solution is obtained. The latter is then placed in a flask closed with a Bunsen valve. The flask is heated to 78-80 C with constant shaking. A magnetic stirrer may be used. Sulfur dioxide is evolved in the process, a slight positive pressure being maintained by the valve. Crystallization sets in suddenly and is essentially complete after four hours. The solid product is filtered and dried under vacuum. Itconsistsof Al203 2 SOs 3 HgO. Heating to 68 to 90°C under vacuum liberates water until the composition AlgOg 2 SOs 1 HaO is attained. 

Formula weight 248.08. Heating above 100°C causes decomposition with evolution of SO3 and water. 

A concentrated aqueous solution of aluminum sulfite is prepared according to the directions in the preceding method and evaporated 

White powder with variable water content. 

dry aluminum powder (30 g.) is ground together with 50 g. of finely divided, dry precipitated selenium. Then 5 g. of the mixture is transferred into a thick-wall, 200-ml. clay crucible provided with a lid. The crucible is placed in the hood and a small piece of burning magnesium strip is dropped in to ignite the mixture. The crucible is immediately covered again. At intervals of a few seconds the lid is raised a little and about 3 g. of the starting mixture is added until the entire mixture is used up. When the crucible has cooled down, the product is crushed and stored in a closed container. 

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In liquid S02 the basic species is S032 so [(CH3)4N]2S03 gives a basic solution in which aluminum sulfite dissolves by forming a sulfite complex, as shown in the equation... 

Furthermore, the amphoteric behavior of the aluminum ion can be shown in sulfur dioxide as readily as in water. Just as AI(OH), is insoluble in water but dissolves readily in either a strong acid or basic solution, AMS03)3 is insoluble in liquid sulfur dioxide. Addition of either base (SO2-) or acid (SO2 ) causes the aluminum sulfite to dissolve, and it may be reprecipitated upon neutralization. 

The application of the solvent system concept to liquid sulfur dioxide chemistry stimulated the elucidation of reactions such as those of aluminum sulfite. However, there is no direct evidence at all for the formation of S02+ in solutions of thionyl halides. In fact, there is evidence to the contrary. When solutions of thionyl bromide or thionyl chloride are prepared in 3JS-labeled (S ) sulfur dioxide, almost no exchange takes place. The half-life for the exchange is about two years or more. If ionization took place ... 

Ans. ia) aluminum nitrate ib) aluminum nitrite (c) aluminum nitride id) aluminum sulfate (e) aluminum sulfite if) aluminum sulfide ig) antimony(III) sulfide (h) antimony(IV) sulfide. 

Notes A sludge of basic aluminum sulfite is occasionally formed when a developer containing sodium carbonate reacts with a partially exhausted acid-hardening fixing bath. This sludging tendency of certain fixing baths is minimized when developers containing Balanced Alkali are used. 

The best bases in liquid S02 are sulfites of organic amines, for example, tetramethyl ammonium sulfite, [(CH NhSOg (for most of the inorganic sulfites are quite insoluble in this solvent). As expected, the conductivity of liquid S02 increases when either S03 (an acid) or a soluble sulfite (a base) is dissolved in it, but the conductivity drops if one of these solutions is mixed with the other (neutralization). Thionyl chloride, SOCL, also exhibits acidic reactions when dissolved in S02 but does not, as is sometimes supposed, yield the S02+ ion (Exercise 1). It is interesting that aluminum sulfite, Als(SOs)s, is amphoteric in liquid S02, just as aluminum... 

Amphoteric behavior in liquid SO2 is similar to that in other solvents. In liquid S02, aluminum sulfite is relatively insoluble which leads to the reaction... 

Subsequently, aluminum sulfite reacts with an acid such as SOCl2,... 

X atomic mass of aluminum = 54.0 amu 3 X atomic mass of sulfur = 96.2 amu 9 X atomic mass of oxygen = 144.0 amu Formula mass = total = 294.2 amu The formula represents 294.2 amu of aluminum sulfite. 

Ans. The molar mass has the same value in grams that the formula mass has in amu (Problem 7.7). Thus 1.000 mol represents 294.2 g of aluminum sulfite. 

We can tell from the formula of a salt how it can be produced. Write a balanced chemical equation for the production of each of the following salts (a) magnesium sulfate, (b) aluminum sulfite, (c) potassium carbonate, (d) zinc chlorate, (e) lithium acetate. 

VAW Sulfite [Vereinigte AluminiumWerke] Also known as the S-T process. A process for extracting aluminum from clay by sulfurous acid. Basic aluminum sulfite, AljOj 2SOj 5HjO, is crystallized from the purified leachate and thermally decomposed. The process was operated on a commercial scale by Vereinigte AluminiumWerke at Lauterwerk, Germany, during World War II. 

Jander and coworkers used these last definitions to interpret the results of their work with liquid sulfur dioxide as solvent. Thionyl chloride is acidic, tetramethylammonium sulfite is basic, and aluminum sulfite is amphoteric in liquid sulfur dioxide. Ionization of this solvent gives thionyl and sulfite ions ... 

The amphoteric behavior of AI2 (803)3 in sulfur dioxide is analogous to that of A1(0H)3 in water. Each contains the negative ion of the respective solvent. Aluminum sulfite, which is insoluble in sulfur dioxide, dissolves on addition of either thionyl chloride... 

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