SODIUM PERBORATE AS A REPLACEMENT FOR SODIUM PEROXIDE IN THE CHEMICAL LABORATORY C . F. H. ALLEN and J. H . CLARK fistman Kodak Company, Rochester, New York
WHEN a vigorous oxidizing action is required in the chemical laboratory, sodium peroxide is one of the more useful reagents. Its drawbacks are well known, especially its hygroscopicity and tendency to start fires when in contact with readily inflammable materials. While sodium perborate has long been known and readily available, it seems to have escaped notice that it can be successfully substituted for sodium peroxide in many oxidation reactions. This is probably due to the emphasis placed on its use in textile chemistry; practically all the abstract references are in this field. In the chemical laboratory sodium perborate offers nearlv all the advantages of sodium peroxide with none -of its drawbacks. The two principal uses of the peroxide are: (a) in the inorganic analytical laboratory, where it is used in the analysis of the iron-aluminum goup, and ( b ) in the organic laboratory for cleavage of or-diketones. Sodium perborate gives equally satisfactory results in both these instances, as shown in the examples below. Sodium perborate has the formula NaBOr4HtO; the reagent grade has 9.5 per cent active oxygen. Thus, it requires twice the weight of the equivalent amount of sodium peroxide. The cost is in line, if the reagent is purchased in large enough quantities to secure the advantages of bulk buying. The solubility is somewhat less than that of sodium peroxide, but so much less than that of hydrogen peroxide that it cannot ordinarily be substituted for the latter in the organic laboratory. Further, i t fails to replace sodium peroxide in the preparation of epoxides from u,,%uusaturated ketones.'
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EXPERIMENTAL WORK
Inorganic.-In the separation of the iron and aluminum groups, the usual procedure is to oxidize the sodium chromite to chromate by cautiously adding solid peroxide to the cold solution. (It reacts explosively, if hot.) By the substitution of sodium perborate, the procedure is altered in but two respects: (a), use twice the weight of peroxide specified, and (b), heat the solution; the solid dissolves with vigorous evolution of gas. The perborate is equally satisfactory when substituted for the peroxide in the separation of zinc, cobalt, and nickel. Organu. Cleavage of B e n d to Benzoic Acid.-Ten grams of benzil were dissolved in 100 cc. of hot methanol. To this was added a suspension of 10 g. of sodium perborate suspended in 100 cc. of 5 per cent aqueous sodium hydroxide. The mixture was heated on a steam bath and stirred mechanically; after about fifteen minutes all the solid had dissolved. This solution was then transferred to a hot plate, evaporated to about half its volume to remove most of the methanol, cooled, and acidified to Congo Red with concentrated hydrochloric acid. The beuzoic acid, which partially separated out as a white solid, was extracted with two 250-cc. portions of ether and the extracts were dried over sodium sulfate. Evaporation of the ether gave 9 g. (77 per cent) of benzoic acid, m. p. 120' to 121'.
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213 (1931).
RIEHT~R AND , HESTER,1.Am. Chem. Soc.. 53,
