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T H E JOURNAL OF INDUSTRIAL A N D ENGINEERING CHEMISTRY
Vol. 13. No. 12
Benzenedisulfonic Acid from Benzenemonosulfonic Acid'iz By C. E. Senseman COLOR INVESTIGATIONLABORATORY, BUREAUOB CHEMISTRY, WASHINGTON, D. C .
Of the several methods described in the literature for the preparation of benzenedisulfonic acid but few are specific in all details, such as concentration of acid, amount of acid, temperature, and time of heat,ing. Barth and Senhofer3 in 1875 described a method of sulfonating the monosulfonic acid by heating for 2 hrs. with an equal volume of fuming sulfuric acid. They neglected to record the strength of acid and proper temperature for carrying out the reaction. Koerner and Monselise4 prepared the disulfonic acid by heating four volumes of an acid mixture, resulting from sulfonating benzene, 3 to 5 hrs. with three volumes of fuming sulfuric acid at 200" to 245". Binschedler and Busch6 described a method in which 24 kg. of benzene are added in a thin stream to 90 kg. of fuming sulfuric acid. The temperature is raised to the boiling point of benzene and continued for 2 to 3 hrs., during which time the mono-acid is formed. The temperature is then raised to 275" and continued for 20 min. Lambert's patent5 specifies the heating of sodium benzene sulfonate with 1 . 5 times its weight of NaHS(SO& 2 $0 3 hrs. at 200" to 240'. None of these investigators have reported either the yield of disulfonic acid or its ratio to the mono-acid. I n 1910 Polak' found that by heating 10 g. of barium benzenesulfonate with 24 cc. of 98 per cent acid at 209', disulfonatjon was complete by the end of 4 hrs. The disulfonation was complete at the end of 3 hrs. when 10 g. of the barium monosulfonate were heated to 233" with 20 cc. of 12.5 per cent fuming acid.
t'o dry these salt mixtures completely it has been found necessary to dry them at a temperature of 190" for 72 hrs. Because of the indirect method of determining the disulfonic acid, inherent analytical errors may be responsible for differences of 1.5 per cent.
Time
EXPERIMENTAL The benzenemonosulfonic acid used in this work is obtained in a crude form and purified by converting it into the barium salt by almost neutralizing with barium hydroxide and finishing off with an excess of barium carbonate.8 After filtering, this solution is evaporated in steam evaporators and the drying completed in an electric oven at 190' for about 96 hrs. Thus prepared, the salt analyzes 99.9 per cent barium benzenemonosulfonate, the analysis being made by determining the barium present in 3 g. of the dried salt. The apparatus used is an enameled kettle equipped with a metal bath and mechanical stirrer which has a speed of 36 revolutions per minute. An open peephole in the cover serves as an escape for steam and fumes, and also for inserting a thermometer into the sulfonating mass. About 0.5 hr. is required to bring the mixture to the desired temperature. This is not considered as a part of the total sulfonating period. I n oxder to determine the progress of the reaction, samples are removed in most cases at intervals of 1 hr. The sample is dissolved in water and neutralized with barium hydroxide and carbonate. From the amounts of soluble salts and barium found in an aliquot part of this solution the ratio of the disulfonic acid to the monosulfonic acid is found. I n order Presented before the Sect:on of Dye Chemistry a t the 59th Meeting of the American Chemical Society, St. Louis, Mo., April 12 to 17,1920. *Published as Contribution No. 52 of the Color Investigation Laboratory, Bureau of Chemistry, Washington, D. C . * Ber., 8 (1875), 1477. 4 Gar. chim.
