56 METHODS OF ANALYSIS. 



three hours, and weigh. Multiply mucic acid by 1.33, which gives galactose, 

 and multiply this product by 0.9 which gives galactan. 



11. Crude Fiber. Official, 

 (a) PREPARATION OF REAGENTS. 



Prepare solutions of sulphuric acid and sodium hydroxid of exactly 1.25 per 

 cent strength, determined by titration. 



(b) DETEBMINATION. 



Extract a quantity of the substance representing about 2 grams of the dry 

 material with ordinary ether, or use residue from the determination of the 

 ether extract. To this residue in a 500 cc flask add 200 cc of boiling 1.25 per 

 cent sulphuric acid; connect the flask with an inverted condenser, the tube of 

 which passes only a short distance beyond the rubber stopper into the flask. 

 Boil at once and continue the boiling for thirty minutes. A blast of air con- 

 ducted into the flask may serve to reduce the frothing of the liquid. Filter 

 through linen, asbestos, or glass wool, wash with boiling water until the wash- 

 ings are no longer acid ; rinse the substance back into the flask with 200 cc of 

 a boiling 1.25 cc per cent solution of sodium hydroxid free, or nearly so, of sodium 

 carbonate ; boil at once and continue the boiling for thirty minutes in the same 

 manner as directed above for the treatment with acid. Filter at once rapidly, 

 wash with boiling water until the washings are neutral, dry at 110 C until 

 it ceases to lose weight; weigh, incinerate completely, and weigh again. The 

 loss of weight is considered to be crude fiber. 



