STAINING, PRACTICAL AND THEORETICAL 



some seventy years or so before the discovery of the first synthetic 

 organic dye (mauvein or mauve) by a young British chemist, 

 Perkin, in 1856. 



Some examples of anthraquinone dyes are given below: 



ACID ALIZARIN BLUE SWR 



Michrome No. 98. Molecular weight 304. A71 acid dye, pH 9 "45*. 

 Solubility at 15° C; water 1%, absolute alcohol 0-75%. 



HO O OH 



-OH 



HO- 



HO OH 



ALIZARIN RED S 



Michrome No. 23. Molecular weight 342. An acid dye, pH 2-15*. 

 Solubility at 15° C: water 6-5%, absolute alcohol 01 -1%. 



O OH 



CARMINIC ACID 



Michrome No. 214. Molecular weight 492. pH 6-85*. A natural 

 colouring matter. Solubility at 15° C: water in all proportions, 

 alcohol 0-2%. 



H3C O OH 



-CeHiiOs 



Ho-v A A >-0H 



HOOC O OH 



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



38 



