REAGENTS. 803 



ture to stand for several days: (a) one part of a 3.5 per cent. 

 alcoholic (95 per cent.) solution of hsematoxylin and (b) three 

 parts of a 0.4 per cent, aqueous solution of potassium alum. 



Delafield's H.ematoxylin Solution, which is also incor- 

 rectly called " Gre'nacher's Hiematoxylin Solution," is made, by 

 mixing the following solutions : (a) Haematoxylin 4 Gm., alcohol 

 25 c.c. and {b) 400 c.c. of a saturated aqueous solution of ammo- , 

 nia alum ; this solution is exposed, to the light for three or four , 

 days, filtered, and then 100 c.c. each of glycerin and methyl alco- 

 hol are added, the solution allowed to stand for several days and, 

 finally filtered. An excess of the stain is removed from the sec- 

 tions by subsequent washing either with a 2 per cent, alum solu- 

 tion or an acidified alcoholic solution. 



Iodine and Potassium-Iodide Solution consists of iodine, 

 13 Gm. ; potassium iodide, 20 Gm. ; water, 100 c.c. 



Iodine Water is prepared by adding as much iodine to dis-i 

 tilled and sterilized water as it will dissolve (about i : 5,000). 



Chloral-Iodine Solution consists of a saturated aqueous 

 solution of chloral, to which as much iodine is added as it will 

 take up. 



Phloroglucin Solution, used as a test for lignin (p. 182), 

 is a 0.5 to 2 per cent, alcoholic solution of phloroglucin, which is 

 used in conjunction with hydrochloric acid. 



Iron Solutions are aqueous or alcoholic solutions containing- 

 5 to 20 per cent, of ferric acetate or ferric chloride. These are 

 mostly used as tests for tannin, giving either a bluish-black or 

 greenish-black coloration or precipitate. 



Copper-Acetate Solution is a 7 per cent, aqueous solution 

 of cupric acetate (p. 181). 



Schulze's Macerating Solution is prepared by adding' 

 crystals of potassium chlorate from time to time to warm con- 

 centrated nitric acid. It is employed in the isolation of lignified 

 cells. 



Special Reagents comprise all those substances which are 

 employed in the morphological study of the cells, and include solu- 

 tions of the alkalies (o.i to 6 per cent.), solutions of the mineral 

 acids, which may be weak or concentrated, and solutions of 

 organic acids, as acetic and citric. 



