STAIN 



TECHNIQUE 71 



image. Naphthol Green B is well suited as a counterstain because 

 generally it is applied with iron alum, is fast to light, and does not 

 extract any of the Hematein. After the sections have been stained 

 in iron Haematoxylin and differentiated in iron alum, the material is 

 rinsed a few seconds in distilled water and counterstained in Naph- 

 thol Green B for five minutes. 



1249a. Chlorophyll, Carotene (Carotin), and Xanthophyll are 

 naturally occurring pigments, light 4. In microscopic plants, the 

 green pigment may be fixed with the aid of copper acetate; this 

 fixation is probably a replacement of the magnesium in chlorophyll 

 by copper. 



Fixative, methyl alcohol- formalin-acetic 



Methyl alcohol 100 ml. 



Formalin, 40% commercial 100 ml. 



Acetic acid, 10% 100 ml. 



Copper acetate 1 gram 



Because chlorophyll is soluble in alcohol, fixed materials for perma- 

 nent mounts in their natural colors are washed in water and dehy- 

 drated from 10 per cent glycerin. 



C. Inorganic Colouring Matters 



1288. Prussian Blue, Berlin Blue, Chinese Blue is ferric fer- 

 rocyanide, light 1 to 2. The pigment may be used as a stain for 

 whole mounts of algae, fungi, or invertebrates. The material is 

 placed first in 3 per cent potassium ferrocyanide for 30 minutes, 

 rinsed thoroughly with distilled water, and then covered with a solu- 

 tion of 1 per cent ferric ammonium sulfate. Should the color be 

 too light, staining may be repeated until the desired shade is ob- 

 tained. The 10 per cent glycerin used for dehydration should con- 

 tain a few drops of J per cent potassium dichromate so that the 

 ferric ferrocyanide does not change to the soluble and colorless 

 ferrous ferrocyanide. Prussian Blue is stable in either balsam or 

 glycerin. 



