1 64 THE CARBOHYDRATES 



2. After staining well with iodine, the addition of strong 

 sulphuric acid causes the cellulose walls to swell considerably 

 and to turn blue. 



3. Chlorzinc iodide causes swelling, accompanied by the 

 assumption of a blue colour. 



4. Calcium chloride iodine solution turns pure cellulose 

 dull pink to violet without swelling. 



Zimmermann gives the following directions for making 

 this reagent. A concentrated solution of calcium chloride is 

 made, and for each 10 c.c. of this solution there is added 

 5 gram of potassium iodide and 'I gram of iodine. The 

 mixture is then gently heated and filtered through glass-wool. 



5. Pure cellulose is easily 'soluble in cuprammonia. 



6. The hemi-celluloses give different reactions ; some turn 

 blue with dilute iodine, and either do not dissolve in cupram- 

 monia, or only after prolonged treatment. 



B. Compound Celluloses, 



(a) Lignin. 



1. A brownish-yellow colour is given with iodine. 



2. The addition of strong sulphuric acid, after previous 

 treatment with iodine, turns lignified walls brown. 



3. The same colour is obtained with the use of chlorzinc 

 iodide. 



4. Calcium chloride iodine solution turns lignin yellow to 

 yellow-brown . 



5. Insoluble in cuprammonia. 



6. Aniline sulphate or aniline chloride in aqueous solution 

 and acidified with the appropriate acid turns lignified walls a 

 bright yellow. 



7. If the sections be soaked for about a minute in an 

 alcoholic solution of phloroglucin (or resorcin, hydroquinone, 

 pyrogallol, or pyrrole) and then mounted in a drop of strong 

 hydrochloric acid, the lignified walls are turned a bright red. 



8. A concentrated solution of thallin sulphate in 50 per 

 cent alcohol gives a yellow to orange-yellow coloration. 



The sections should be treated first with alcohol, and the 

 thallin sulphate solution should be freshly prepared. 



The colour-reactions obtained by the use of aniline suk 



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