Platinum catalyst for reductions

The platinum black by reduction of the oxide may sometimes be used a second, third or even more times in the reduction of certain compounds merely by reactivating (Note 8) with air or oxygen. A spent catalyst must be reworked (Note 9) 

If a considerable quantity of platinum oxide is desired it is more satisfactory to prepare several runs of the size indicated than one large run, since spattering and the evolution of gases make large amounts inconvenient to handle. The activity of the catalyst appeared in certain cases to decrease after standing for several weeks and therefore the oxide should preferably be prepared as required. 

Commercial C.p. chloroplatinic acid varies somewhat in its purity. In this work that from the Mallinckrodt Chemical Works, St. Louis, was used and gave very satisfactory results. Since small amounts of impurities in the catalyst are important factors in the rate of reduction of certain types of compounds, this question of impurities in the chloroplatinic acid must be taken into account (Note 13). In a large proportion of the reductions studied, platinum oxide prepared from the chloroplatinic acid mentioned gave as good results as that from spectroscopically pure chloroplatinic acid made according to the directions of Wichers.1 

If only platinum metal is available this is dissolved in aqua regia and evaporated to dryness several times with hydrochloric acid, until free from nitrates (Note 9) and the product purified according lo the method of Wichers. 

sodium nitrate could probably be used in place of the c.p. grade in most instances, but in one type of reduction at least (that of aminophenols to cyclic amino alcohols) the small amount of impurities in the u.s.p. gtade affected the activity of the catalyst. 

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Platinum Catalyst for Reductions (Coll. Vol. i, 452) Preparation from platinum black by heating with oxygen underpressure. Laffiteand Grandadam, Compt. rend. 200, 456 (193s). 

Platinum Catalyst for Reductions (CoU. Vol. i, 452) Directions are given for the preparation of a colloidal platinum (or palladium) catalyst in an anhydrous, alkaline medium. This catalyst is said to be particularly valuable for the reduction of nitriles, oximes, and nitrostyrenes to pure prinaary amines. Skiia and Keil, Ber. 63, 424 (r932). 

Platinum catalyst for reductions, 15, 89 Potassium acetate, 13, 36 Potassium bichromate, 12, 64 Potassium ferricyanide, 16, 41... 

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