488 APPENDIX III. 



Picric aniline-blue. To a saturated watery solution of picric acid, about 4 

 per cent, of a saturated watery solution of aniline-blue is added, so 

 that a deep blue-green fluid is produced. 

 nigrosine. See Nigrosine, Picric. 



Potash (Potassium hydrate). Concentrated watery solution. A test for 

 suberin (p. 186). Suberised tissues placed in it become yellow ; if 

 warmed, the colour is much deeper ; if boiled, the suberin is exuded 

 in the form of yellowish drops. 



Dilute watery solution, 5 or 6 per cent. Specially used as a " clear- 

 ing " reagent. 



Acetate of. Concentrated solution in water. Used as a mounting 

 fluid. After covering with the cover-glass, the preparation must 

 riot be sealed for about twenty-four hours. The fluid does not 

 crystallise. See p. 216. 



Alcoholic (Russow's). Rectified spirit is mixed with a concentrated 

 watery solution of potassium hydrate till a slight precipitate is 

 formed. The fluid is frequently shaken, and allowed to stand for 

 twenty-four hours. The resulting weakly yellow fluid is poured off 

 from the sediment, and for use must be diluted with half its volume 

 of distilled water. For the ordinary purposes of dilute potash this 

 is preferable to the watery solution. 



All these potash reagents, especially the watery solutions, must be 

 kept in well-stoppered bottles, and the stopper occasionally 

 anointed with vaseline. 



Bichromate of. 10 per cent, solution in water. Reagent for tannin. 

 Chlorate of. Constituent of Schultze's macerating mixture (q.v.). 

 Nitrate of (Saltpetre). A constituent of Knop's culture-fluid for 

 algse, 251. 



in 10 per cent, solution. An excellent plasmolysing reagent. 

 PJwsplwte of. A constituent of Knop's and Pasteur's nutrient 

 solutions ('/#.). 



(Acid). A constituent of Cohn's normal solution (q.v.). 



Potassio-sodic tartrate. Used in Fehling's sugar reaction, 66. 



Potassium permanganate. Used in the preparation of Diatoms, 259. 



Purpurin (Delta). Sometimes used with " solid green " or with chrysoidin 

 as a double stain, 112. 



R. 



Rosaniline (or Fuchsin) violet (Hanstein's). Equal parts methyl-violet and 

 fuchsin (magenta) mixed and dissolved in alcohol. Shows up strati- 

 fication of cell- walls, and differentiates sections of stems, especially 

 monocotyledons. Stains protoplasm bluish-violet ; amyloid sub- 

 stances, nucleus, and gums different shades of red ; resins, blue ; 

 tannin, foxy-red ; cellulose, pale violet ; lignin, reddish ; bast-fibres, 

 deep-red ; sieve-tubes and bast parenchyma, hardly at all. This is 

 also an excellent stain for chlorophyll-bodies. 



