Five grams of the monoamino compound were mixed with powdered KOH, heated together until the mixture just melted, and maintained in that state for a few minutes. When the latter had cooled down to room temperature, cold water was poured over the mixture. The filtered solution was acidified until no further precipitate was formed. The precipitate was collected and recrystallized from water, m.p. 121°C. One gram of this solid was placed in a test tube, provided with a cork and a delivery tube, and heated with soda lime; a liquid with the smell of benzene was collected in another test tube cooled with water. When this liquid was treated with a few drops of nitric acid mixture the smell of nitrobenzene was given off. A gram of the crystals was heated with concentrated sulphuric acid and alcohol when the odor of ethyl benzoate was noted. Monacetyl Derivative Five grams of the monoamino selenazole were heated on a water-bath with 10 cc. of acetic anhydride until the solution was clear, which took about two hours. 100 cc. of water were poured into the mixture, which was then neutralized with dilute ammonium hydroxide. The precipitate was filtered, decolorized by animal charcoal, and recrystallized from dilute alcohol. The acetyl compound, 6-acetamino-2-phenylbenzoselenazole, forms colorless crystals, melting at 188.1°-.7°C. (corr.). It is insoluble in ether, benzene, carbon disulphide; slightly soluble in toluene; soluble in alcohol, ethyl acetate, amyl acetate, acetone, and acetic acid. A pure sample was analyzed and gave the following result, Calculated for C₁₅H₁₂N₂SeO Found Nitrogen 8.88% 8.92% 8.68% Monobenzylidene Derivative Five grams of the monoamino compound were dissolved in 200 cc. absolute alcohol with the addition of 3 cc. of benzaldehyde and the clear solution was boiled on a water-bath, with a return condenser, for two hours. After the solution was boneblacked, the yellow precipitate was recrystallized from carbon disulphide. The yield was 90 per cent. It crystallizes in yellow plates, melting at 156.7°-157.6°C., soluble in benzene, ether, ethyl alcohol, carbontetrachloride, acetone, but difficultly soluble in ligroin. An analysis of the crystals showed the following result, Calculated for C₂₀H₁₄N₂Se Found Nitrogen 7.75% 7.92% 7.68% An Azo Dye