294 ISIDOK GREENWALD 



of application for life insurance. It is found to reduce the customary 

 reagents, though more slowly. An apparent glucose content of 0.1 to 1 

 per cent is indicated. 



Neuberg(c) (1902) has explained the delayed reduction as being due to 

 the presence of a part of the pentose as a ureide, or compound with urea. 

 He found that the reducing power of a pentose urine was increased by 

 .boiling with acid and that the reduction was then prompt, that pentose 

 added to normal urine reduced promptly, and that the amount of pentose, 

 as calculated from the amount of furol obtained on distillation with 

 hydrochloric acid, was greater than that obtained by the copper reduction 

 methods on the unhydrolyzed urine. But this explanation and, indeed, 

 the very fact of a delayed reduction have been challenged by others. 



Examination shows that the reducing substance cannot be glucose. 

 It is not fermented by yeast, shows little or no optical activity and yields a 

 phenylosazone of widely different melting point and nitrogen content from 

 phenylglucosazone, but agreeing with those found for pentosazone. 



The orcin test is also useful as indicating the presence of pentose. 

 The urine is heated to boiling with an equal volume of concentrated 

 hydrochloric acid and a little orcin. If pentose is present, the mixture 

 will turn green (red by transmitted light) to blue or violet, depending 

 upon the amount of pentose. If the amount of pentose is considerable, a 

 precipitate will be produced. If the mixture is allowed to cool and is 

 then extracted with amyl alcohol, this will take up a green to blue or 

 violet color. Or, if the mixture is cooled to room temperature, filtered 

 and the precipitate washed with cold water and then dissolved in alcohol, 

 this will be colored blue and show a sharp absorption band at or near 

 the yellow D line of the spectrum. The test should be carefully controlled 

 by using urine and acid without orcin, a normal urine with both reagents 

 and a normal urine with added pentose. 



A similar test with phloroglucin was formerly much used but has 

 since been found to be readily obtained with other sugars and derivatives. 



Variety of Pentose Found. The character of the pentose was first 

 investigated by Neuberg(fr) (1900), who isolated inactive arabinose from 

 the urine of one of the cases reported by Salkowski and by Blumenthal. 

 Because of the usual optical inactivity of the urine and probably also be- 

 cause 1-arabinose is one of the naturally occurring pentoses, it has generally 

 been assumed that the pentose is i-arabinose. But lack of optical activity 

 is usually of little significance because the concentration of the pentose, as 

 determined by a copper reduction method, is too low to permit of a 

 satisfactory polariscopic examination. Of those instances in which the 

 concentration was sufficiently high, dextrorotation has been reported in 

 ten cases and optical inactivity in only five, including the one reported by 

 Neuberg. This is not the place for a complete discussion of the nature 

 of the evidence, but it may safely be concluded from the work of Elliott 



