QUALITATIVE AND QUANTITATIVE ANALYSIS 77 



(d) The residue from the hot water extraction is now treated 

 two or three times with boihng 95 per cent alcohol. The alco- 

 holic solution is evaporated in a weighing bottle and dried to 

 constant weight. 



(e) The residue from the alcohol extraction is treated with 100 

 cubic centimeters of a 2 per cent hydrochloric acid solution and 

 boiled under a reflux condenser for 5 to 6 hours. The solution is 

 filtered off, through dried and weighed filter papers, and the 

 residue is washed with dilute acid, then with distilled water, 

 until free from acid. The filtrate and washings are now analyzed 

 for reducing sugars, by the Bertrand method, and for total 

 nitrogen. The amount of reducing sugar multiplied by 0.9 gives 

 the hemicellulose content of the material. 



(/) The washed residue from the hydrochloric acid extraction 

 is dried to constant weight. Two 1-gram portions of the dry 

 material are placed in 300-cubic centimeter Erlenmeyer flasks 

 and treated with 10 cubic centimeters of an 80 per cent sulphuric 

 acid solution (if the residue is compacted, it should be first well 

 ground; if it is horny, it should have been washed with alcohol 

 and ether, before drying), for 2 hours, in the cold. The acid 

 must be brought in contact with all particles of the material. 

 After 2 hours, 150 cubic centimeters of distilled water is added to 

 each flask and contents autoclaved for 1 hour at 120°C., or 

 boiled for 2 to 3 hours under the reflux condenser. The con- 

 tents are then filtered through small dried and weighed filter 

 papers or through weighed Gooch crucibles. The residue is 

 well washed with water to wash out traces of sulphuric acid. 

 The combined solution and filtrate are analyzed for reducing 

 sugar. The amount of glucose found multiplied by 0.9 gives the 

 cellulose content of the material. Of the four residues for each 

 original material, two are used for ash and two for nitrogen 

 determinations. Weight of -(residue) — (ash + nitrogen X 

 6.25) = lignin content. The cellulose and lignin found in 1 

 gram of residue left from the 2 per cent HCl extraction are 

 now multiplied by the number of grams in this residue to 

 give the cellulose and lignin content in the original 5 grams 

 of material. 



