SECTION ONE 



PONCEAU S 



Michrome No. 725. Molecular weight 761. An acid dis-azo dye, 

 pH 8-0*. Solubility at 15° C: water i -35 %, absolute alcohol i -2%. 



SOgNa 



NaOsS 



N=N 



HO SOaNa 



N=N 



SOgNa 



PONCEAU DE XYLIDINE 



Michrome No. 565. Molecular weight 556. An acid dis-azo dye. 

 Solubility at 15° C; water 5%, absolute alcohol o-i %. 



OH 



N=N 



N=N 



SOsNa 



SOsNa 



SCARLET R 



Michrome No. 576. Molecular weight 394. A neutral dis-azo 

 colouring matter. Solubility at 15 °C; water nil, absolute alcohol 

 o-6%. 



CH. 



CH. 



N=N 



OH 



N=N 



CHg 



* 1% in neutral distilled water; see pages 17 and 29. 



SI 



