912 



nitrogen-fre<.i extract of feeding stuifs, as well as tlie substances asso- 

 ciated with cellulose in wood and in thelijjiiified i)arts of jdants, Itelicv- 

 ing a correct determination of the feeding value of the nitrogen-freo 

 extract of feeding stufts to be possible only after thorough investiga- 

 tion of the individual conii>oiients of the nitrogen-free extract and of 

 so-called crude fiber. Since his own investigations ami the investiga- 

 tions of others have shown the almost universal occurrence of pentji- 

 glucoses in vegetable i)roducts, the elaboration of a method for the quan- 

 titative determination of these substances was believed to be of imjxtr- 

 tance. The nitrogen- free extract and the crude fiber as detennin«'d by 

 the ordinary methods of fodder analysis inclu<lei)entaglucoses, often in 

 cf)nsiderable quantities. Pentaglucoses difter from the true carbohy- 

 diates by yielding furfurol instead of levulinic acid when treated with 

 hydrocliloric acid of a certain concentration, and in certain color 

 reactions. The qualitative determination of the pentaglucoses in vege- 

 table matters is made by lieating the sul)stance for a few minutes with 

 dilute liydrocliloiii- a<'id in a watt-r bath, wiiereby the carbohjdrates 

 and also the pentaglucoses and substances which yield these are dis 

 solved. If the filtered extract is now heated with stiong hydrochhnic 

 acid and |)lilor(»g!ncin a cherry-red colm- is prothiced if arabinose or 

 xylose are ]>resent, while the true sugars only give a brownish cf>lor. 

 This reaction is further chara<-terized by dark lines in the siMM-trum. 

 'I'lie pentaglucoses are determined •|uantitatively by distilling vegeta- 

 ble substances containing them with hydrochloric acifl (»f ceitain »'on 

 centration and determining the furfurol in the distillate. The author 

 has given much time to the perfection of this method (see Experiment 

 Station Kecord, vol. ii, ]>. <IS.~>). The reaction is given as follows: Fur 

 fnrol, <'.,n4()j, is derived from arabinose or xylose, CsHioOft by the 

 sjilitting off (»f three molecules of water. The sulistance is vt)lati]e. 

 and when freed liy hydrochloric acid appeals in the distillate. The 

 formation of furlurol from these substances is a quantitative one. The 

 furfurol in the distillate is (b'termined quantitatively by means of i)he- 

 nylhydra/in, ("„H„X2i Ji leagent for ahlehydes and ket(»nes in general. 

 With this it forms a nearly insoluble compound, furfurol h>(lrazon. 

 The hydrazon separates out when an a(pie<>us solution of phenylhydra- 

 zin and acetic acid is a<lded to the distillate. The hydra/.on can be fil- 

 tered and weighed and the furfurol calculated from the weight: or the 

 furfuiol may be estimate(l by means of titration, determining the amount 

 of phenylhydra/.in of known strength which is re(iuired to i)recipitate 

 all the furlur«»l in the distillate. Both methods have been worked out 

 by the author, the titration method in company with A. Cliinther, and 

 the gravimetric method with de Chalmot.* From the percentage of 

 furfurol which is found in the distillate the calculation of the amount 

 of arabinose or xylose yielded by the substance may be made by use 



* A niotho<t for the qnantitativo cetini.ition of the pent.Tgliiooses has also been 

 publitthed by W. E. Stone in Jour, Anal, and Appld. Chem., 6, So. S. 



