Patent GB-382372-A (GB)
Title: Improved extraction process for obtaining substances in purified condition
IPC: C10K1/32
Filed: 1931-09-10
Abstract: Pure substances are obtained in crystalline form from natural or synthetic products by extraction with a volatile solvent, or a mixture of such solvents, to which is added, before or after the extraction, a less volatile organic liquid of smaller solvent power for the desired substance, or a mixture of such liquids; the solvent is distilled off from the extract thereby causing a precipitation of the extracted substance from the organic liquid. The extraction may be carried out under pressure and the volatile solvent be removed from the extract by reduction of pressure.  The solvent and organic liquid are chosen in each case so as to dissolve as little of the impurities present as possible and to retain in solution in the less volatile liquid such impurities as are extracted.  Alternatively an impurity may be similarly extracted leaving the desired substance in purified form.  One of the examples given relates to the separation of anthracene and carbazole by treating crude anthracene with a mixture of sulphur dioxide and acetone under pressure leaving a residue of comparatively pure anthracene, and the carbazole separating from the acetone after evaporation of the sulphur dioxide; the mother liquor still containing carbazole and traces of anthracene is resaturated with sulphur dioxide and again used in the process. Ammonia may replace sulphur dioxide in the process according to this example.  Various other volatile solvents specified for use in accordance with the general invention are amines, hydrocyanic acid and carbon dioxide.  A mixture of methyl and ethyl alcohols may be used as a less volatile organic liquid.ALSO:Pure substances are obtained in crystalline form from natural or synthetic products by extraction with a volatile solvent, or a mixture of such solvents, to which is added, before or after the extraction, a less volatile organic liquid of smaller solvent power for the desired substance, or a mixture of such liquids; the solvent is distilled off from the extract thereby causing a precipitation of the extracted substance from the organic liquid. The extraction may be carried out under pressure and the volatile solvent be removed from the extract by reduction of pressure.  The solvent and organic liquid are chosen in each case so as to dissolve as little of the impurities present as possible and to retain in solution in the less volatile liquid such impurities as are extracted.  Alternatively an impurity may be similarly extracted leaving the desired substance in purified form. Examples are given relating to (1) the extraction of sodium nitrate from caliche using ammonia as the solvent and methyl alcohol as the less volatile liquid, extraction being conducted under pressure and sodium nitrate being obtained as a precipitate leaving sodium iodate in solution in the alcohol; (2) the extraction of alkali cyanides or cyanates from calcium cyanamide-alkali melts, using ammonia and alcohol; (3) the extraction of sodium cyanide obtained by heating briquettes of soda and carbon in an atmosphere of nitrogen, or obtained according to Specification 301,565, [Class 1 (ii), Inorganic compounds, other than &c.], or German Specification 51562, using a mixture of ammonia and alcohol; (4) the extraction of sulphur from spent gas-purifier mass or from crude Silician sulphur, using a mixture of hydrogen bisulphide or carbon bisulphide and ethyl alcohol; (5) the separation of anthracene and carbazole by treating crude anthracene with a mixture of sulphur dioxide and acetone under pressure leaving a residue of comparatively pure anthracene, and the carbazole separating from the acetone after evaporation of the sulphur dioxide; the mother liquor still containing carbazole and traces of anthracene is re-saturated with sulphur dioxide and again used in the process.  Ammonia may replace sulphur dioxide in the process according to this example. Various other volatile solvents specified for use in accordance with the general invention are amines, hydrocyanic acid and carbon dioxide.  A mixture of methyl and ethyl alcohols may be used as a less volatile organic liquid.ALSO:Pure substances are obtained in crystalline form from natural or synthetic products by extraction with a volatile solvent, or a mixture of such solvents, to which is added, before or after the extraction, a less volatile organic liquid of smaller solvent power for the desired substance, or a mixture of such liquids; the solvent is distilled off from the extract, thereby causing a precipitation of the extracted substance from the organic liquid. The extraction may be carried out under pressure and the volatile solvent be removed from the extract by reduction of pressure.  The solvent and organic liquid are chosen in each case so as to dissolve as little of the impurities present as possible and to retain in solution in the less volatile liquid such impurities as are extracted.  Alternatively an impurity may be similarly extracted leaving the desired substance in purified form. Examples are given relating to (1) the extraction of sodium nitrate from caliche using ammonia as the solvent and methyl alcohol as the less volatile liquid, extraction being conducted under pressure and sodium nitrate being obtained as a precipitate leaving sodium iodate in solution in the alcohol; (2) the extraction of alkali cyanides or cyanates from calcium cyanide-alkali melts, using ammonia and alcohol; (3) the extraction of sodium cyanide obtained by heating briquettes of soda and carbon in an atmosphere of nitrogen, or obtained according to Specification 301,565, [Class 1 (ii), Inorganic compounds, other than &c.], or German Specification 51562, using a mixture of ammonia and alcohol; (4) the extraction of sulphur from spent gas-purifier mass or from crude Silician sulphur, using a mixture of hydrogen bisulphide or carbon bisulphide and ethyl alcohol; (5) the separation of anthracene and carbazole by treating crude anthracene with a mixture of sulphur dioxide and acetone under pressure leaving a residue of comparatively pure anthracene, and the carbazole separating from the acetone after evaporation of the sulphur dioxide; the mother liquor still containing carbazole and traces of anthracene is re-saturated with sulphur dioxide and again used in the process.  Ammonia may replace sulphur dioxide in the process according to this example. Various other volatile solvents specified for use in accordance with the general invention are amines, hydrocyanic acid and carbon dioxide.  A mixture of methyl and ethyl alcohols may be used as a less volatile organic liquid.ALSO:Pure substances are obtained in crystalline form from natural or synthetic products by extraction with a volatile solvent, or a mixture of such solvents, to which is added, before or after the extraction, a less volatile organic liquid of smaller solvent power for the desired substance, or a mixture of such liquids; the solvent is distilled off from the extract thereby causing a precipitation of the extracted substance from the organic liquid. The extraction may be carried out under pressure and the volatile solvent be removed from the extract by reduction of pressure.  The solvent and organic liquid are chosen in each case so as to dissolve as little of the impurities present as possible and to retain in solution in the less volatile liquid such impurities as are extracted.  Alternatively an impurity may be similarly extracted leaving the desired substance in purified form. Examples are given relating to (1) the extraction of sodium nitrate from caliche using ammonia as the solvent and methyl alcohol as the less volatile liquid, extraction being conducted under pressure and sodium nitrate being obtained as a precipitate leaving sodium iodate in solution in the alcohol; (2) the extraction of alkali cyanides or cyanates from calcium cyanide-alkali melts, using ammonia and alcohol; (3) the extraction of sodium cyanide obtained by heating briquettes of soda and carbon in an atmosphere of nitrogen, or obtained according to Specification 301,565, [Class 1 (ii), Inorganic compounds, other than &c.], or German Specification 51562, using a mixture of ammonia and alcohol; (4) the extraction of sulphur from spent gas-purifier mass or from crude Silician sulphur, using a mixture of hydrogen bisulphide or carbon bisulphide and ethyl alcohol.