SECTION TWO 



PERIODIC ACID - SCHIFF REACTION (PAS) 

 For polysaccharides 



A. 



B. 



Solutions required 

 Periodic acid 

 Distilled water . . 

 Sodium acetate M/5 



Distilled water . . 

 Periodic acid 

 Sodium acetate M/5 

 Absolute alcohol 



0-4 gm. 

 45 ml. 

 5 ml. 



10 ml. 

 0-4 gm. 

 5 ml. 

 35 ml- 



Note: This solution, which deteriorates after a few 

 days, should be kept in an amber bottle. 



C. Reducing rinse: 

 Potassium iodide 

 Sodium thiosulphate 

 Distilled water . . 



I gm. 

 I gm. 

 20 ml. 



Dissolve; then add with stirring: 



Absolute alcohol . . • • 30 ml. 



Hydrochloric acid 2N . . . . 0-5 ml. 



Note: A percipitate of sulphur is slowly formed and 

 this may be allowed to settle out, or the solution may be 

 used immediately. 



The solution loses its acid reaction on keeping for 

 some time, and it should be tested with litmus paper; 

 if the reaction is no longer acid a few drops of N/2 hydro- 

 chloric acid should be added until an acid reaction is 

 obtained. 



D. Schiff's reagent 



E. Sulphite wash water: 

 Distilled water . . 

 Hydrochloric acid, pure, cone. 

 Potassium metabisulphite 



351 



45 '5 ml. 

 0-5 ml. 

 0-2 gm. 



