Stannic sulfide, preparation

Stannic sulfide may be prepared as a yellow amorphous precipitate by double decomposition of a stannic salt with hydrogen sulfide. The crystalline modification, known as mosaic gold, may be prepared by sulfurizing stannous sulfide in the following way ... 

Dissolve the stannic sulfide in 0.2 ml of concentrated hydrochloric acid, heat in boiling water and pass a current of air for a few minutes to remove hydrogen sulfide. Dilute to about 1.5 ml and make ammoniacal. Centrifuge off the stannic hydroxide and dissolve it in 0.1 ml of 6M hydrochloric acid. Dilute to 0.3-1 ml as appropriate, and prepare sources on distrene, adding 2 drops of 3M hydrofluoric acid before evaporating to prevent volatilization of tin. 

Besides hydrolysis, one can also utilize other exchange reactions in the preparation of disperse systems. It is, however, important to remember that a substantial amount of electrolyte, which is often present in the solution, may result in a loss of colloidal stability. One can sometimes remove excess electrolyte by washing and subsequent peptization of the precipitate. It is advantageous to prepare disperse systems at high supersaturations, which can be reached upon mixing concentrated solutions of reactants. The sols of Prussian Blue, various sulfides, stannic acid and its compound with colloidal gold (Cassian Purple) are all made by this method. 

Thioglycosides. These glycosides are prepared in high yield by reaction of an alkyl trlbutylstannyl sulfide with peracetyl pyranosyl or furanosyl halides in the presence of stannic chloride. An anomeric mixtufe is usually formed. 

Friedel-Crafts reaction catalysts like anhydrous aluminum chloride are readily soluble in the nitroalkanes. Solutions containing up to 50% aluminum chloride are easily prepared in nitroalkane solvents. These catalytically active complexes, AICI3-RNO2, can be isolated and used in solvents other than the nitroalkane. The reactants in the Friedel-Crafts reaction are often soluble in the nitroalkane reaction medium. Other catalysts like boron trifluoride (BF3), titanium tetrachloride (TiCl4), and stannic tetrachloride (SnCl4) are also soluble in the nitroalkane solvents. Reaction types which use nitroparaffins as solvents include alkylation of aromatics, acetylation of aromatics, halogenations, nitrations, and the reaction of olefins and hydrogen sulfide to yield mercaptans. 

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