Mr Purvis, The conversion of saiv-dust into sugar 259 



The conversion of saw-dust into sugar. By J. E. PuRViS, M.A. 

 [Read 17 February 1919.] 



The production of sugar from wood is well known. In the 

 Classen process, saw-dust is digested in closed retorts with a weak 

 solution of sulphurous acid under a pressure of between six and 

 seven atmospheres. The products contain about 25 °/^ of dextrose, 

 and other substances are pentose, acetic acid, furfurol and formal- 

 dehyde. Cellulose material can also be converted into sugar by 

 other acids. 



The following results were obtained by digesting saw-dust 

 from ordinary deal with different acids of varying concentrations ; 

 estimating the amount of sugar in the liquid in the usual way 

 from the amount of cuprous oxide precipitated from Fehling's 

 solution, and converting this oxide of copper to cupric oxide. The 

 numbers were then calculated in terms of dextrose. 



(1) 25 grams of saw-dust were digested with 300 c.c. distilled 

 water and 50 c.c. strong H2SO4 (1 c.c. H2S04 = 1*78 grms. H2SO4) 

 for 5^ hours in a sand bath at a temperature just below the 

 boiling point and the mixture was constantly stirred. This was 

 then filtered ; the residue well washed and the filtrate made up to 

 a litre ; 10 c.c. of the filtrate were neutralised with sodium 

 carbonate and the cuprous oxide from Fehling's solution was 

 precipitated, filtered, dried and ignited to cupric oxide. This gave 

 0"215 grm. CuO which is equivalent to 39 °/^ of dextrose on the 

 original amount of saw-dust. 



(2) 25 grams of saw-dust to which were added 500 c.c. of 

 distilled water and 25 c.c. of strong H2SO4 of the same strength as 

 in experiment (1) and digested for 5 hours under the same 

 conditions. This gave 13 °/^ of dextrose. 



(3) 50 grams of saw-dust were digested with 500 c.c. of 

 distilled water and 50 c.c. of the strong H2SO4 for 5f hours. The 

 yield was 11 "5 % dextrose. 



(4) 25 grams of saw-dust were digested with 250 c.c. of tap 

 water and 10 c.c. of strong H2SO4 for 2 hours. This yielded 10*5 7o 

 dextrose. 



(5) 25 grams of saw-dust were digested with 720 c.c. of tap 

 water and 10 c.c. strong H2SO4 for 2 hours. This produced 3*35 "/^ 

 dextrose. 



(6) 50 grams of saw-dust were digested with 500 c.c. water 

 and 50 c.c. N/1 HCl (= 1-825 grms. HCl) for 3 hours. This gave 

 3-35 % dextrose. 



