Chapter VI 

 BIOLOGICAL STAINS 



A, Synthetic Organic Dyes (Continued) 

 Classes VII to XXVI 



Class VII. Stilbene Colouring Matters 



620. Sun Yellow is a direct dye, light 3 ; J gram in 95 ml. of 

 distilled water, 5 ml. of 5 per cent sodium sulfate, and £ ml. of 

 acetic acid. A few direct dyes react in a manner similar to a 

 mordant; such dyes are not always evident in the finished slide 

 but they assist in the fixation of the more important dye. Because 

 the color of Sun Yellow in combinations with blue dyes changes to 

 green, the relative amounts of yellow, green, and blue can be used 

 as an indicator to show when the proper degree of contrast has been 

 obtained. This dye on both animal and plant materials serves as 

 a mordant in the production of green in combinations with blue 

 counterstains ; this green is more fast to light than Fast Green 

 FCF, C. I. No. 670. 



On whole mounts of invertebrates or on paraffin sections of 

 tissues, use Sun Yellow ten minutes; in mixtures with Orange II, 

 C. I. No. 151, the Crocein Scarlets, or Biebrich Scarlet, C. I. No. 

 280, for five minutes ; in mixtures with Acid Fuchsine, C. I. No. 

 692, try one to five minutes. The contrast dyes include : ( 1 ) Ani- 

 line Blue, C. I. No. 707, 15 to 30 seconds, (2) Niagara Sky Blue, 

 C. I. No. 520, 30 seconds to one minute, (3) New Methylene Blue, 

 C. I. No. 927, one minute, or (4) Erie Violet BW, C. I. No. 387, 

 five to eight minutes. 



Use Sun Yellow or the mixtures containing Sun Yellow for 24 

 hours on mature plant tissues but ten minutes to an hour on meri- 

 stems. The counterstains require 15 seconds to five minutes de- 

 pending on the time given to the lighter stain. 



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