STAIN TECHNIQUE 61 



alum, and i ml. of acetic acid. New Methylene Blue is a constituent 

 of several triple and quadruple stains which are described under the 

 separate acid dyes. These combinations of stains can be used on 

 sections of embryonic animal tissues. For the general staining of 

 plant tissues New Methylene Blue gives better results than either 

 Methylene Blue or Methylene Azure. It may be used as a contrast 

 stain after Acid Fuchsine, C. I. No. 692, Biebrich Scarlet, C. I. No. 

 280, Crocein Scarlet MOO, C. I. No. 252, Orange II, C. I. No. 151, 

 or Sun Yellow, C. I. No. 620. 



931. Brilliant Alizarin Blue is a basic dye, light 3 to 4. This 

 stain is darker than New Methylene Blue. The stain is not so good 

 with the addition of ammonium alum ; with alkalies very little color 

 is produced. 



Class XXI. Sulfur and Sulfide Colouring Matters 



Many of the sulfur dyes are not classified in the Colour Index 

 because their chemical composition at present is unknown. There 

 are no bright red sulfur dyes. 



948. Sulfur Yellow, or Sulfur Orange, and 949. Sulfur 

 Brown 4G differ very little from Sulfur Bordeaux. 



956. Sulfur Direct Blue, Sulfogene Direct Blue BRS (Du 

 Pont) is a direct dye, light 2; 1/10 gram in 95 ml. of 1 per cent 

 sodium sulfide and 5 ml. of 4 per cent sodium hydroxide. Blue- 

 green algae are not stained so intensely nor so brightly as with 

 Sulfur Brilliant Blue. The details of cell structure are presented 

 very clearly. 



957. Sulfur Brilliant Blue, Sulfindone Brilliant Blue CG 

 (NAC), Sulfogene Brilliant Blue 6BS (Du Pont), and Sulfogene 

 Brilliant Blue 3GCF (Du Pont) are direct dyes, light 2 ; 1/10 gram 

 in 95 ml. of 1 per cent sodium sulfide and 5 ml. of 4 per cent sodium 

 hydroxide. Because the stain does not keep over a day, it must be 

 made as needed. These are the best blue sulfur dyes ; the color is 

 nearly violet on algae mounted in glycerin. Algae are placed in the 

 stain one to three hours at 50° C, rinsed with tap water, and then 

 oxidized to a deeper shade as soon as the moist plants are exposed 

 to air, for 15 minutes. Invertebrates such as Obelia, or jelly-fish 



