GB336111A - Improvements in the manufacture and production of thiourea - Google Patents

Abstract

336,111. Johnson, J. Y., (I. G. Farbenindustrie Akt.-Ges.). Oct. 19, 1929. Thiourea is produced by treating calcium cyanamide with hydrogen sulphide in the absence of liquids or in the, presence of small quantities of liquid sufficient to give a paste. The thiourea i.s extracted from the reaction mixture by means of organic solvents. In forming the paste, there may be used water or aqueous liquids, or organic liquids capable of dissolving hydrogen sulphide, such as alcohols, e.g. methyl and ethyl alcohols, or amines, e.g. aniline and alkylamines, or esters, e.g. ethyl acetate, or pyridine, or hydrocarbons and their halogen derivatives, e.g. benzene or mixtures of organic liquids may be used during the conversion. In some cases it is advantageous to add alkaline substances such as ammonia and gaseous amines to the liquids. Frequentlythe hydrogen sulphide is caused to react at high pressures and while stirring. The temperature should not normally exceed 100‹ C. For the extraction, liquids are chosen which dissolve the thiourea but not the lime compounds, as for example ketones, e.g. acetone, also pyridine and its homologues, but especially mixtures of organic liquids such as mixtures of alcohols and ethers, or of alcohols and benzene, or of alcohols and chloroform, carbon tetrachloride, or benzene, and in some cases mixtures of organic liquids with water, e.g. aqueous alcohols. When water is present during the reaction it is often advantageous to dry the mass resulting from the reaction before the extraction. It is preferable to extract with hot solvents; the thiourea may then be recovered by cooling, and the mother liquor used again for extraction. The thiourea may also be obtained by evaporation of the solvent. In the examples, a paste is made with ethyl alcohol or aqueous ammonia, or the cyanamide is treated with gaseous ammonia before the introduction of hydrogen sulphide.