TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Composition: The mineral salt is an alkali metal salt or alkali metal sulfate. The concentration of mineral salt in aqueous solution is 1 weight% to saturated concentration.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Composition: The hydrophobic organic solvent is aromatic hydrocarbon solvent. The monoalcohol having 4C atoms or more is 4-6C monovalent solvent. The hydrophilic organic solvent is hydrophilic ether solvent, hydrophilic nitrile solvent or hydrophilic ketone solvent. The alcohol solvent is obtained by mixing water with methanol, ethanol, 1-propanol, 2-propanol, ethylene glycol or propylene glycol. The ratio of alcohol and water in mixed solvent of alcohol and hydrophobic organic solvent is 30-95 weight%. Preferred process: The dihalo biphenyl compound is obtained by mixing diazo compound of formula (2), copper halide of formula: CuX1 (3) aqueous solution containing mineral salt and dihalo biphenyl compound, and water. Preferred Component: The content of dihalo biphenyl compound and water in organic layer is adjusted, and crystallized. The solvent and water in concentration solution are removed by distillation process. The concentration solution is diluted with alcohol having boiling point lower than hydrophobic organic solvent. Preferred Compound: A biphenyl disulfonate is obtained by reacting dihalobiphenyl compound with chlorination agent and alcohol in organic solvent. EXAMPLE - Water (in weight parts) (700.5), benzidine 2,2-disulfonic acid (350), aqueous solution of sodium nitrite (460.1), hydrochloric acid (327.3) and copper chloride (166) were added and reacted at 10 degrees C for 1 hour to obtain solution (B). Then, aqueous solution (C) containing 4,4-dichloro biphenyl-2,2-disulfonic-acid disodium and sodium chloride was obtained (2604), 4,4-dichlorobiphenyl-2,2-disuonic-acid disodium (313), sodium hydroxide (50-450) and sodium chloride (93) were added and reacted to obtain aqueous solution (D). Toluene (315), 2-propanol (1258), obtained aqueous solution (D), water layer (2403), organic layer (2289), 4,4-dichlorobiphenyl-2,2-disuonic-acid disodium (231.4) and toluene (377) were added, reacted and isolated to obtain dihalobiphenyl compound. A dihalobiphenyl compound had stability.