The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Aug. 18, 1981
Filed:
May. 31, 1979
Peter Furrer, Bottmingen, CH;
Harry Beyeler, Basel, CH;
Ciba-Geigy Corporation, Ardsley, NY (US);
Abstract
A novel improved process for separating mixtures of 3- and 4-nitrophthalic acid is described. The said process comprises treating a mixture of 3- and 4-nitrophthalic acid, which mixture is free from inorganic acid residues, in an aqueous-organic medium containing 1-20 percent by volume of water, at a temperature of between 20.degree. and 100.degree. C., stepwise with a base capable of forming salts of 3- and 4-nitrophthalic acid, which salts are essentially insoluble in the reaction medium, the treatment being carried out by adding base until a pH value of about 2.8 is obtained, separating the precipitating product consisting mainly of a 3-nitrophthalic acid mono-salt, subsequently precipitating, by the addition of further base, a product consisting principally of a 4-nitrophthalic acid salt, and finally converting the resulting nitrophthalic acid salts separately into the corresponding free acids, and optionally purifying these. The 3- and 4-nitrophthalic acid can be obtained by the process according to the invention in a simple manner in an isomer-free form and in good to very good yields.