58 METHODS OF ANALYSIS. 



ing. The volume of alumina cream to be added must be taken into account in 

 determining the amount of water used for the extraction. After the extraction 

 filter immediately, pouring back upon the filter the first portions of cloudy 

 filtrate until the filtrate is clear. To free from soluble impurities add sufficient 

 normal lead acetate solution to 200 cc of the filtrate to precipitate all impurities, 

 make up to 250 cc, and filter. Remove the excess of lead by means of anhydrous 

 sodium carbonate or anhydrous sodium sulphate, followed in the latter case by 

 a small amount of anhydrous sodium carbonate, care being taken not to use an 

 excess. Filter again and use the clear filtrate for the following determinations : 



(b) REDUCING SUGAR. 

 (Calculated as dextrose, or invert sugar.) 



Determine dextrose in a 50 cc aliquot of the clear filtrate by Allihn's method 

 ("VI. General Methods," p. 49). Multiply the amount of dextrose by the 

 factor 1.044 to obtain the equivalent in invert sugar. 



(c) SUCROSE. 



Invert a 50 cc aliquot of the clear filtrate according to one of the methods for 

 the inversion of sucrose given under optical methods for determining sucrose 

 ("VI. General Methods," p. 40). Determine the total reducing sugar and 

 calculate as invert sugar according to (b). The total invert sugar less the 

 invert sugar determined under (b) gives the true invert sugar from sucrose, and 

 this multiplied by 0.95 gives sucrose. 



7. Starch. 



Determine according to the directions given under " VI. General Methods," 

 page 53, section 8. 



8. Pentosans. 



Determine according to the directions given under " VI. General Methods," 

 page 54, section 9. 



9. Galactan. 



Determine according to the directions given under "VI. General Methods," 

 page 55, section 10. 



10. Crude Fiber. 



Determine in 2 grams of the air-dry material according to the directions 

 given under " VI. General Methods," page 5G, section 11. 



