STAIN TECHNIQUE 63 



in one minute when ferric alum is used as the mordant but the color 

 is not clear and the differentiation is not satisfactory. 



A good brick red may be obtained on plant tissues with the fol- 

 lowing procedure: 15 minutes in turkey red oil solution, rinse in 

 distilled water, 15 minutes in a saturated solution of ammonium 

 alum, rinse in water, five minutes in lime water, rinse, and 12 to 24 

 hours in an alkaline solution of Alizarin. Turkey red oil is sul- 

 fonated castor oil. To 100 ml. of distilled water is added 1 ml. of 

 turkey red oil and two or three drops of ammonium hydroxide to 

 give a clear solution. 



1034. Alizarin Red S, Alizarin Sodium Sulfonate is a direct 

 mordant dye, light 4 ; ^ gram in 95 ml. of distilled water, 5 ml. of 5 

 per cent ammonium alum, and \ ml. of acetic acid. After a plant 

 section has been in the stain 12 to 24 hours, it is rinsed in distilled 

 water and dipped into turkey red oil solution in order to develop the 

 orange-red pigment. 



1037. Purpurin is an acid mordant dye, 3 to 4; 1/10 gram in 80 

 ml. of 5 per cent ammonium alum, boil, cool, filter, and add 20 ml. of 

 95 per cent alcohol which serves as a preservative. Plant tissues 

 are stained a brilliant red within 24 hours. The dye counterstains 

 easily with a large number of basic blue, violet, or green dyes. Un- 

 fortunately, this red is fugitive. 



1048. Acid Alizarin Blue GR is a direct mordant dye, light 2. 

 The dye dissolves either in 1 per cent ammonium acetate or in 5 per 

 cent ammonium alum. The stain is not active until heated to 50° 

 C. ; at this temperature, mordanted sections of plant tissues are 

 stained bright blue. It is difficult to obtain a satisfactory prepara- 

 tion because a precipitate separates from solution soon after the 

 stain is heated. 



1049. Acid Alizarin Green G is a direct mordant dye, light 1 ; 

 1/10 gram in 100 ml. of 1 per cent ammonium acetate. Blue-green 

 and green algae or fungi mordanted in ferric alum become clear 

 green within five to ten minutes at 50° C. The dye is not so good 

 for invertebrates in whole mounts. On paraffin sections of animal 

 tissues mordanted in 1 per cent ferric alum, light green is produced 

 in 30 seconds and clear green in one minute at 50° C. 



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