NEW MATERIAL:Bis(9'-acridinyl)-1,4-phenyldihydrazine shown by the formula.

USE: Useful as a dyeing agent for dyeing partially human chromosome, capable of recognizing a specific chromosome, namely capable of confirming and judging position of the specific chromosome, effective for discovering and elucidating various diseases and abnormal diseases.

PREPARATION: For example, 1mol 9-hydrazinoacridine is reacted with 0.5W0.75mol p-phthalaldehyde in a hydrophiic solvent such as methanol, dimethylformamide, etc., usually at 50W60°C to precipitate and to deposit crystal of a compound shown by the formula, which is filtered, washed and dried by conventional procedures. 9-Hydrazinoacridine of a raw material, for example, is synthesized by reacting N-phenylanthranilic acid with phosphorus oxychloride under heating and reacting the reaction product with hydrazine hydrate in an alcoholic solvent under heating.