400 APPENDIX. 



Potassium Bichromate is used in dilute (1 to 5 per cent.) 

 aqueous solution as (1) a test for tannin ; (2) a fixing and hardening 

 reagent ; (3) a liquid allowing transmission of orange and red light, 

 when placed in a double -walled bell- jar. 



Potassium Chlorate is used, together with nitric acid, as a 

 macerating fluid and a test for suberin. 



Potassium Ferricyanide is used to demonstrate the structure 

 of pyrenoids, especially in Algae. Place the specimen in a mixture 

 of equal parts of 10 per cent, aqueous solution of potassium ferri- 

 cyanide, and 50 per cent, solution of acetic acid, then treat as 

 described under Dahlia. 



Safranin. Make a saturated solution in alcohol, and dilute with 

 equal volume of water. This is a good general stain, and is also 

 used along with haematoxylin, etc., in double staining. It gives 

 good results with Spirogyra and other Algae. Place the material, 

 after fixing with chromic acid or other fixative, in the safranin 

 solution for several hours, then in 50 per cent, alcohol, to which 

 strong alcohol is added drop by drop so as to reduce the intensity 

 of the colour ; then transfer the specimen to dilute glycerine, or 

 pass it through clove oil or xylol into balsam. 



Schultze's Maceration Fluid. See Maceration. 



Silver Nitrate. A 5 per cent, aqueous solution of silver nitrate 

 is used to bring out the striations in fibres and in starch grains. 

 (1) Sections containing fibres are allowed to dry, then placed in the 

 solution for an hour, and transferred to 1 per cent, solution of 

 common salt ; they are then placed in water and exposed to light 

 for an hour, allowed to dry again, then moistened with strong 

 alcohol and examined in clove oil. (2) Dry starch, or sections 

 containing starch grains, are placed in the solution for an hour, 

 then allowed to dry on a slide, then treated with 1 per cent, solu- 

 tion and exposed to light for an hour. 



Sodium Chloride (Common Salt) is used (1) in 1 to 5 per cent, 

 solution to induce plasmolysis ; (2) in 10 per cent, solution as a 

 solvent for protein crystals. 



Sodium Salicylate, dissolved in an equal weight of water, is 

 used as a clearing agent, and is almost as good as chloral hydrate. 

 With the addition of iodine, this solution makes starch grains, 

 included in tissues, swell and turn blue. 



Sulphuric Acid has a variety of uses. (1) The strong acid 

 dissolves starch and cellulose, but suberised and cutinised walls 

 resist its action ; (2) it is used with cane sugar as a test for 

 proteins a red colour is given ; (3) it dissolves crystals of calcium 

 oxalate ; (4) it causes cellulose walls, previously saturated with 

 iodine solution, to become blue. 



