BORDEAUX RED — BROWN DISCOLORATION 289 



and transparent. This is a useful stain for^aleurone grains, 

 for differentiating cell-contents from cell-walls when the sections 

 are subsequently stained with methyl green, and much used also 

 in the differentiation of the cell-contents of filamentous algae. 



Bordeaux Red. — Used in conjunction with hsematoxylin in 

 staining nuclear figures, particularly where Heidenhain's pla- 

 tinic chloride fixative has been used. The sections are placed 

 in a weak aqueous solution of the Bordeaux until they are in- 

 tensely stained; they are then rinsed and placed in a 2 to 5 per 

 cent, solution of ferric-ammonium sulphate for three hours. 

 If the sections are mounted on a slide, they should be placed 

 upright in this solution, so that any precipitate may not gather 

 on the slide. Then the sections are carefully washed in an 

 abundance of water, and placed for twenty-four hours in a solu- 

 tion of haematoxylin prepared as follows: i gm. of haematoxylin 

 is dissolved in 10 gm. of alcohol and 90 gm. of water. This is 

 allowed to stand for about four weeks and then an equal bulk 

 of distilled water is added. The stain is then ready for use. 

 When the sections are taken from the hsematoxylin, they will 

 be found overstained; they are, therefore, rinsed and placed in a 

 2 . 5 per cent, solution of ferric-ammonium sulphate, where they 

 remain until examination of the sections under the microscope 

 shows the desired intensity of color. Then rinse in water 15 

 minutes, dehydrate in alcohol, and pass through xylol for mount- 

 ing in Canada balsam. 



Borodin's Method.^To determine the nature of a precipi- 

 tate Borodin treats it with a saturated solution of the same sub- 

 stance as the precipitate is supposed to be. Thus, if the pre- 

 cipitate is supposed to be asparagin, it is treated with a saturated 

 solution of asparagin. If the precipitate dissolves by this treat- 

 ment, it is then some other substance than asparagin. This 

 method is not very reliable for substances which are very readily 

 soluble, such as potassium nitrate. Care must be taken that 

 the solution used for the test is entirely saturated. 



Brown Discoloration of Material in Alcohol. — Some 

 plants, such as Monotropa, are apt to become quite brown in 

 19 



