1897.] PUBLIC DOCUMENT — No. 33. 97 



THE PHLOEOGLUCIN METHOD FOR THE ESTI- 

 MATION OF PENTOSANS. 



J. B. LINDSEY and E. B. HOLLAND. 



Couiicler * has suggested that, instead of phenylhydrazin, 

 phloroglucin be employed for the precipitation and estima- 

 tion of furfurol obtained by the distillation of various sub- 

 stances, with dilute hydrochloric acid. Kruger and Tollens f 

 have further studied and perfected the method, and recom- 

 mended it as reliable for the estimation of pentosans in vari- 

 ous coarse fodders, grains and vegetables. 



The phloroglucin, like the phenylhydrazin method, is 

 based on the fact that the pentosans (araban, xylan, etc.) 

 differ from other carbohydrates in that they yield furfurol 

 instead of levulinic acid upon digestion with moderately 

 dilute hydrochloric or sulphuric acids. The first step neces- 

 sary in both processes for a quantitative estimation is the 

 conversion of the pentosans into furfurol and its separation 

 from the resulting by-products. 



Phloroglucin Method described. 

 Three grammes of the material are brought into a ten- 

 ounce flask, together with 100 c.c. of 12 per cent, hydro- 

 chloric acid (specific gravity, 1.06), and several pieces of 

 recently heated pumice stone. The flask, placed upon wire 

 gauze, is connected with a Liebig condenser, and heat ap- 

 plied, rather gently at first, and so regulated as to distil over 

 30 c.c, in ten to fifteen minutes from the time that boilinsr 

 begins. The 30 c.c. driven over are replaced by a like 

 quantity of the dilute acid, by means of a separatory funnel ; 

 and the process so continued as long as the distillate gives a 

 pronounced reaction with aniline acetate on filter paper (a 



* Chemikerztg, 1894, No. 5L f Zeitsch. far Ang. Chem., 1896, Heft II. 



