A Treatise on Chemistry by Henry Enfield Roscoe Karl Schorlemmer

Author:Henry Enfield Roscoe , Karl Schorlemmer
Language: eng
Format: epub
Publisher: D. Appleton & Co.
Published: 1888-03-25T05:00:00+00:00

ai55 Parasulphobenzoic acid is obtained by the oxidation of poratoluenesulphonic acid; it is not necessary to employ pure material for its preparation, and the mixture of the three isomeric acids which is obtained by dissolving toluene in sulphuric acid may be conveniently made use of. The para-compound is the chief constituent of the mixture, and, together with the meta-acid, is readily oxidized, while the ortho-acid remains unaltered (Remsen).

One hundred grammes of toluene are dissolved in the smallest possible quantity of fuming sulphuric acid, the solution made up to five litres with water, and heated imtil it becomes colourless. Hydrochloric acid and barium chloride are then added to the filtrate and the precipitated acid barium salt purified by re-crystallization ; 200 grammes of it are obtained in this way.^

It is also formed by the action of alcoholic sulphurous acid on paradiazobenzoic acid (Vollbrecht and Wiesinger).

Parasulphobenzoic acid is readily soluble in water, and crystallizes in needles, which are not deliquescent and melt with decomposition at about 200°. On fusion with caustic potash, parahydroxybenzoic acid is formed, while with potas-sitim formate it yields terephthalic acid.

The potassium salt forms transparent needles which easily dissolve.

Normal barium parasiclphobenzoate, CyH^SO^Ba-h 2H2O, cirystallizes in small, tolerably soluble needles. The acid salt, CC7H5S05)2Ba + ^HgO, is slightly soluble in hot water, and forms long, flat, lustrous needles.

.SO2.NH2 ParasulpJuimidobenzoic acid, CflH.^ , is formed by

\CO.OH

tti€ oxidation of paratoluenesulphamide with chromic acid solution. It is almost insoluble in cold, slightly soluble in hot water, and readily in alcohol, crystallizing in long, flat, lustrous prisms.

* Hart, loc. cit.

^'OL. III. — PART IV.

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