Pectocelluloses and Mucocelluloses 



223 



throw light upon the problems discussed in the earlier sections 

 of this treatise. 



(2) SALEP MUCILAGE was prepared from the tubers pre- 

 viously pulped by grinding in a mortar, the details of pre- 

 paration being exactly as for the above. The mucilage was 

 precipitated by alcohol in white threads which hardened under 

 further treatment with alcohol (dehydration). 



The dry substance (retaining i -5 p.ct. mineral constituents) 

 gave on analysis numbers approximately those of cellulose 

 (C 6 H 10 5 ), viz. : 



C . 44*58 



H . 6-63 



The hydrolysis of the product, by boiling with dilute acid 

 (1*25 p.ct. H 2 SO 4 ), was investigated in relation to the influence 

 of the time factor upon the three products, cellulose, gum, 

 and glucoses : the former being estimated by direct weighing ; 

 the latter, in terms of dextrose, by titration with Fehling's solu- 

 tion ; the result, subtracted from the total dissolved products, 

 giving the yield of gum. 



It will be noted that the sum of the percentages in some 

 cases exceeds TOO, and in some is in defect. 



These observations are explained by the attendant phe- 

 nomena of hydration and dehydration ; and the disappearance 

 of * glucose ' after the fourth hour, when it reaches a maximum, 

 is evidently due to condensation of aldehydic groups. 



