226 



Biological Stains 



^ Alizarin stains tissues a feeble yellowish red if used on them 

 directly. In the presence of aluminium compounds intense red 

 colors are formed ; bluish violet in the presence of iron ; and brown- 

 ish violet in the presence of chromium. It has been used as a stain 

 for nervous tissue and for the vital staining of protozoa. Geyer 

 (1932) employs it to distinguish cows' from goats* milk. The chief 

 present use of alizarin, however, is as an indicator. 



H r 

 N 



I 



I 



I 



I 



o 



I 



O400 

 o 



I I I • I I I I I I X • I J 

 460 520 580 640 700 

 WAVELENGTH m }X 



Fig. 26. Spectral curve of alizarin red S. 

 b5 alizarin red S C. I. NO. IO34 



Synonyms: Alizarin red, water soluble. Alizarin carmine. 



SOjNa 



CuHyOxSNa; Mol. Wt. 342.253 

 {An acid dye) 

 {Absorption maxima in alkaline solution about 557 [59J!t.-9]) 



Solubility at S6°C: in water 7.69%; in alcohol 0.15% 

 A spectral curve of this dye is given in Fig. 26. 



