34 W. H. E M I G 



Thionine, C. I. No. 920, (4) New Methylene Blue, C. I. No. 927, 

 or (5) Victoria Blue B, C. I. No. 729. 



168. Superchrome Garnet Y (NAC) is a mordant dye, light 



3. Paraffin sections of plant tissues are stained orange-yellow to 

 brown. The color becomes darker with an after-treatment in 

 potassium dichromate. Blue-green algae are stained orange-red 

 in an alkaline solution of the dye at 50° C. The pigment gradually 

 disappears in glycerin. 



169. Superchrome Violet B (NAC) is an acid mordant dye, 

 light 3. Paraffin sections of plant tissues appear bright pink ; they 

 are more fast to washing with an after-treatment in 5 per cent 

 ammonium alum. A mordant of potassium dichromate and acid 

 potassium tartrate gives a reddish brown on parenchyma. Blue- 

 green algae in an alkaline bath containing potassium dichromate, 

 heated to 50° C, are dark carmine. The color disappears slowly 

 in 10 per cent glycerin. 



170. Superchrome Black PV (NAC) is an acid mordant dye. 

 Paraffin sections of plant tissues stain a dull bordeaux ; with a mor- 

 dant, the color is bordeaux to brown. Blue-green algae in a hot 

 alkaline bath are violet to blue-black; the pigment is not fast in 

 glycerin. 



175. Naphthylamine Brown is an acid dye, light 3 to 4. 

 Plant tissues stain light brown to rich red-brown ; in the presence 

 of potassium dichromate they are darker brown. 



176. Fast Red A is an acid dye, light 4. This stain does not 

 differentiate well but blends with blue dyes. 



179. Azorubine is an acid dye, light 4. Commercially, Azoru- 

 bine is used as a substitute for the more expensive Acid Fuchsine. 

 Plant tissues are stained brilliant red that contrasts well with blue 

 dyes. Unfortunately, the color fades rapidly. 



184. Amaranth, Naphthylamine Red is an acid dye, light 3 to 



4. This dye is used principally as a food color. 



185. Brilliant Scarlet 3R is an acid dye. Most materials are 

 stained pink which is too pale to be useful. The stain becomes 

 moldy on standing. 



