STAINS AND STAINING 57 



proves stains like gentian violet, which are more or less soluble in clove 

 oil. Even in such cases, xylol should follow the clove oil, or the prepa- 

 ration will fade. 



While the anilins are not as permanent as the haematoxyhns, most 

 of them keep fairly well if the staining has been carefully done. Prepa- 

 rations fade if exposed long to bright sunhght. Keep the slides in the 

 box when not in use, and even when in use, do not leave them on the 

 laboratory table, exposed to the sun. We have preparations, made 

 more than 30 years ago, in which the safranin and gentian violet are 

 still bright; and others made more than 15 years ago, in which Mag- 

 dala red and anilin blue have not faded. 



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 from 1 to 20 minutes, but if the 

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

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

 creased 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 botan- 

 ists. The directions apply to solutions made up according to the for- 

 mulas given with the different stains. 



Safranin. — For the botanist, safranin is the most useful of all the 

 anihn stains, and safranin is practically the only safranin he needs. 

 This stain, although certified, still has a certain measure of variability, 

 but is comparatively uniform. In the fourth edition of this book we 

 advised making the stain by mixing equal parts of an alcohol-soluble 

 and a water-soluble safranin. We thought we generally got a better 

 stain and probably we did, sometimes, because the stains were not 

 uniform, and, by this method, we had two chances, instead of only 

 one, for getting a good stain. The certified safranin is equally soluble 

 in water or alcohol. A 1 per cent solution in 50 per cent alcohol, or in 

 water is best for general work and can be diluted when desirable. 



Flemming, who developed the famous triple stain — safranin, gentian 

 violet, orange — dissolved 0.5 g. of alcoholic safranin in 50 c.c. of abso- 

 lute alcohol and, after 4 days, added 10 c.c. of distilled water. 



