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Expired
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GB11614/24A
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Publication of GB223192ApublicationCriticalpatent/GB223192A/en
Organic Low-Molecular-Weight Compounds And Preparation Thereof
(AREA)
Abstract
The process of the parent Specification for producing 1-phenyl-2 : 3-dimethyl-4-dimethylamino-5-pyrazolone, by reduction of 1-phenyl-2 : 3-dimethyl-4-nitroso-5-pyrazolone in the presence of formaldehyde or its polymers, is modified by treating 1-phenyl-2 : 3-dimethyl-5-pyrazolone with nitrous acid and treating the reaction mixture, without separation of the nitrose body, according to the parent Specification. In an example a solution of 1-phenyl-2 : 3-dimethyl-5-pyrazolone in dilute sulphuric acid is treated while cooling and stirring with sodium nitrite and the product reduced until colourless with zinc dust, sulphuric acid, and a small quantity of copper sulphate, after which formaldehyde and a further quantity of reducing agent are added. The mixture is filtered, made alkaline, and the dimethylaminopyrazolone extracted with benzene and purified by crystallization.
GB11614/24A1923-04-101924-05-10Improvements in the manufacture of 1-phenyl-2.3-dimethyl-4-dimethylamino-5-pyrazolone
ExpiredGB223192A
(en)
Improvements in and connected with the production of solutions containing oxides of chromium, and with the electrolytic separation of chromium from such solutions