Stains and Staining 51 



Preparations fade rapidly if exposed to bright sunlight. Keep the 

 slides in the box when not in use, and, even when in use, do not leave 

 them scattered over the laboratory tables, exposed to bright light. 



Some of the anilins are acid, some basic, and some are neutral. 



The rapidity with which sections must be transferred from one 

 fluid to another makes many of them more difficult to manage than 

 the haematoxylins or the carmines, but the stains are so valuable 

 that even the beginner should spend most of his time with the anilins. 



Many anilins stain quite deeply in 1 to 20 minutes, but if the 

 stain washes out during the dehydrating process, stain longer, even 

 10 to 24 hours if necessary. Often the brilliancy of the stain can be 

 increased by leaving the slide for 5 minutes in a 1 per cent solution of 

 permanganate of potassium before staining. The permanganate 

 acts as a mordant. 



The following are the more important anilins now in use by 

 botanists. The directions apply to solutions made up according to 

 the formulae given with the different stains. 



Saf ranin.- -Two safranins are sold by dealers, one soluble in 

 water and the other soluble in alcohol. The alcoholic is somewhat 

 soluble in w r ater and the aqueous is somewhat soluble in alcohol, 

 but both make better solutions when used with their intended 

 solvents. 



The best aqueous solution is simply a* 1 per cent solution in 

 distilled water. 



The alcoholic solution is made by dissolving 1 g. of the alcoholic 

 safranin in 100 c.c. of 95 per cent or absolute alcohol and, after the 

 safranin is completely dissolved, adding 50 c.c. of distilled water. 



According to Flemming, dissolve 0.5 g. of alcoholic safranin in 

 50 c.c. of absolute alcohol, and after 4 days add 10 c.c. of distilled 

 water. 



A method which w r e have used for more than ten years with good 

 results is to make a 1 per cent solution of the aqueous safranin in 

 distilled water; then make a 1 per cent solution of the alcoholic 

 safranin in 95 per cent alcohol; then mix equal volumes of the two 

 solutions. This makes a strong solution of safranin in about 50 per 

 cent alcohol. 



