56 W. H. E M I G 



Class XIII. Quinoline Colouring Matters 



A number of dyes with the property of color-sensitizing photo- 

 graphic plates belong here. Most of them are fugitive and ex- 

 pensive. 



801. Quinoline Yellow is an acid dye, light 2 ; J gram in 95 ml. 

 of distilled water, 5 ml. of £ per cent potassium dichromate, and 1 

 ml. of 1 per cent sulfuric acid. On most plant tissues this stain is 

 too light. A clear bright yellow is obtained more easily with the 

 addition of potassium dichromate. 



806. Cyanine is a basic dye, light 5. It is one of the most ex- 

 pensive as well as one of the most fugitive dyes. Nuclei are stained 

 blue ; the cytoplasm and cell walls have only a faint color. Algae in 

 whole mounts are not stained evenly. The same color and stain- 

 ing reactions can be obtained with Capri Blue, C. I. No. 876. 



Class XIV. Thiazole and Thiobenzenyl Colouring Matters 



To this class belongs Primuline, C. I. No. 812, which is a fugi- 

 tive acid dye that has little value for histological purposes. 



Class XV. Indamine Colouring Matters 



Indamine dyes are of no value as stains ; they are intermediate 

 products used in the manufacture of sulfur dyes. 



Class XVI. Indophenole Colouring Matters 



These substances are used in the manufacture of vat dyes. 



Class XVII. Azine Colouring Matters 



825. Neutral Red, Toluylene Red is a basic dye, light 3. Plant 

 tissues stained a dull red in acid solutions become more intense red 

 with the addition of ammonium alum. This dye is frequently used 

 as a vital stain ; the various parts of the living cell are differentiated 

 in orange or red. It is also used as an indicator. 



826. Neutral Violet is a basic dye, light 4. Plant tissues are 

 stained a fugitive blue-violet. The dye solution decomposes on 

 standing. 



828. Azocarmine GX is an acid mordant dye, light 3 to 4. 

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



