PENTOSES. 203 



alcohol solution shows an absorption-band between D and E. The orcin 

 test is better for several reasons than the phloroglucin test (SALKOWSKI 

 and NEUBERG *) . In regard to the use of these tests in urine examina- 

 tion see Chapter XV. 



Many modifications of these tests have been suggested. BRAT 2 performs 

 the orcin reaction by the addition of NaCl and heating to only 90-95. RIAL 3 

 uses a hydrochloric acid containing ferric chloride for the orcin test and claims 

 to get a greater delicacy. On too strong and too long heating (1^-2 minutes), 

 when using this modification, a confusion with sugars of the six carbon series ma 

 occur (BiAL, VAN LEERSUM). 4 According to R. ADLER and 0. ADLER the phi 

 roglucin and orcin tests can be made with glacial acetic acid and a few dro} - 

 hydrochloric acid instead of with the hydrochloric acid alone. These investigator^ 

 also use a mixture of equal volumes of aniline and glacial acetic acid as a reagen*, 

 for pentoses. On the addition of a little pentose to the boiling mixture a beautiful 

 red color of furfurol-aniline acetate is obtained. A. NEUMANN 5 performs the 

 orcin test with glacial acetic acid and adds concentrated sulphuric acid drop 

 by drop. On following the exact instructions not only do the pentoses give 

 this reaction, but also glucuronic acid, dextrose, and levulose give characteristic 

 colored solutions with special absorption-bands which can be made use of in 

 identifying the various sugars. FR. SACHS has tested BIAL'S test and has given 

 special precautions to prevent confusion with glucuronic acid. JOLLES 6 pre- 

 cipitates (from urine) the pentoses as osazones, distills the precipitate with 

 hydrochloric acid, and tests the distillate with BIAL'S reagent. 



In performing the above two tests for pentose it must be borne in 

 mind that glucuronic acid gives the same reactions and also that the 

 colors alone are not sufficient. The spectroscopic examination must 

 therefore never be omitted. Both tests are to be considered as tests of 

 detection rather than definite pentose reactions, and therefore for a 

 positive detection of pentoses we must prepare also the osazones or other 

 compounds. 



Arabinoses. The pentose isolated by NEUBERG from human urine 

 is r-arabinose. It can be isolated from the urine as the diphenylhydra- 

 zone, from which the arabinose can be separated by splitting with for- 

 maldehyde. The inactive r-arabinose seems to be the pentose regularly 

 occurring in pentosuria and thus far, in only one case, has Z-ara,binose been 

 found (R. LUZZATTO). Z-Arabinose is said to pass into the urine after 

 partaking of certain fruits such as plums in large amounts (C. BARS- 

 ZCZEWSKI 7 ) . 



1 Salkowski, Zeitschr. f. physiol. Chem., 27; Neuberg, ibid., 31. 



2 Zeitschr. f. klin. Med., 47. 



3 Deutsch. ined. Wochenschr., 1902 and 1903, and Zeitschr. f. klin. Med., 50. 



4 Bial, Zeitschr. f. klin. Med., 50; van Leersum, Hofmeister's Beitrage, 5. 



5 R. and O. Adler, Pfliiger's Arch., 106; A. Neumann, Berl. klin. Wochenschr., 

 1904. 



8 Fr. Sachs, Biochem. Zeitschr., 1 and 2; Jolles, ibid., 2, Centralbl. f. klin. Med., 

 1907, and Zeitschr. f. anal. Chem., 46. 



7 Neuberg, Ber. d. d. chem. Gesellsch., 33; Luzzatto, Hofmeister's Beitrage, 6, 



