Process for the preparation of isolated 3,4-diaminobenzenesulphonic acid
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United States of America Patent
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Sep 7, 2004
Grant Date -
Mar 25, 2004
app pub date -
Sep 16, 2003
filing date -
Sep 17, 2002
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Abstract
Described herein is a process for the preparation of 3,4-diaminobenzenesulphonic acid, characterized in that 1,2-diaminobenzene is reacted with anhydrous sulphuric acid which optionally comprises SO.sub.3 in up to stoichiometric amount, at a temperature in the range from 100 to 160.degree. C. with stirring for a reaction time of from 1 to 20 hours; water or ice is added to the reaction mixture, optionally with cooling, up to a sulphuric acid concentration in the range from 30 to 75% by weight, based on the total mixture; the 3,4-diaminobenzenesulphonic acid precipitated out of the reaction mixture is filtered off, optionally washed with dilute sulphuric acid and worked up.
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