292 PENTOSURIA 



creased. Confirmation of this work with a refined technic 

 which will permit the possibility of quantitative differentia- 

 tion between pentoses and hexoses, is very much to be 

 desired. 



Detection of Pentoses. Most cases of pentosuria are for 

 a time regarded as diabetics and treated as such ; and yet 

 the diagnosis of pentosuria is not a difficult one. Even with 

 Fehling's test an attentive observer will notice that the fluid 

 at first remains clear and only after considerable boiling is 

 suddenly and fitfully reduced. Neuberg explains this 

 peculiarity upon the supposition that pentose may be in the 

 form of a ureide in the urine : 



CHj.OH- (CH.OH) 3 -COH+ 

 +H 2 0. 



Eeduction can take place only in proportion as such a 

 ureide is split by hydrolytic influences and the aldehyde 

 group thus set free; for which reason it is probable that 

 many statements as to the amount of pentose in urines 

 are too low. 



With special attention it will be found in investigating 

 the urine of a pentosuric individual that the reducing sub- 

 stance of the urine is neither f ermentescible nor is it optically 

 active. The phenylhydrazine test yields beautiful yellow 

 osazone-needles, the melting point of which is, however, dis- 

 tinctly lower than that of glucosazone. Transformation of 

 arabinose into a diphenylhydrazone is, according to Neuberg 

 and Wohlgemuth, also applicable in testing quantitatively 

 for arabinose in the presence of other carbohydrates. 

 Finally, the Tollens tests in their different modifications, the 

 greenish-blue color obtained by heating with orcin and 

 hydrochloric acid and the analogous red color with phloro- 

 glucin, and the spectroscopic behavior of the coloring matter 

 obtained by shaking with amylalcohol, are very useful, even 

 if they are not absolutely distinctive. Jolles recommends 



