72 HATCH EXPERIMENT STATION. [Jan. 



3. That the precipitate should be washed with small quan- 

 tities of water, and should not be allowed to become dry 

 during the washing. 



4. That the presence of diresorcol in the phloroglucol 

 does not affect the results.^ 



5. That the precipitate be dried four hours in a water 

 bath, and that the Gooch crucible be kept in a glass bottle 

 diu'ing the drying, and be weighed in the glass-stoppered 

 bottle after cooling, in order to prevent the hydroscopic 

 phloroglucol from taking on water. 



The Association of Official Chemists at its 1902 meeting 

 adopted Krober's formulae and tables for calculating the 

 results . 



While the phloroglucol method has been perfected, it can 

 still be regarded only as a conventional method. Further- 

 more, the fact must not be overlooked that other substances 

 besides pentosans yield furfural. Thus Tollens^ and his 

 earlier pupils have shown that glycuronic, euxanthic and 

 urochloi^alic acids yield furfural on distillation with hydro- 

 chloric acid, and Cross and Bevan^ have obtained furfural 

 from oxycellulose. Widstoe* and others^ have also shown 

 that methyl pentosans C^H''(CH)^0** frequent!}' accompany 

 the true pentosans, and upon distillation yield methyl fur- 

 fural C5H3(CH)302 -I- 2H20 and is likewise precipitated by 

 phloroglucol. Fraps^ finds that the hydrochloric acid dis- 

 tillate from hay yields on standing, besides furfural, a black 

 precipitate and other substances which are precipitated by 

 phloroglucol. These latter he termed furaloids. 



Cross and Bevan '' have applied the term furfuroids in place 

 of pentosans to all furfural-yielding substances. Tollens, 

 on the other hand, as well as Stone, ^ believe it preferable 

 to retain the old name. 



* This statement has been disputed by American chemists (see especially 

 Fraps, Bulletin No. 172, North Carolina Experiment Station). 



'' Loco citato. 



^ Berichte, 27, p. 1061. 



* Berichte, 33, p. 143. 



■> Zeitsch. fiir Angw. Chem., 1902, Heft 20, p. 481. 

 « Am. Chem. Jour., 25, p. 501. 



' Chemical News, 1894; Am. Cliem. Jour., 22, p. 034. 

 » Chemical News, 1895, p. 40. 



