206 BLOOD SUGAR 



Michaelis and Eona for the removal of albumin by shaking 

 with a colloidal iron solution, based on the physical-chemical 

 principle that two colloids of different content will precipi- 

 tate each other 40 ; (liquor ferri oxydati dialysati is not in- 

 appropriate for the purpose). The same principle is em- 

 ployed by Mockel and Frank 41 in their method of estimation 

 of sugar in the blood. Ivar Bang and his collaborators 42 

 remove the albumin with alcohol, and get rid of the protein 

 residue by shaking with blood charcoal in the presence of 

 hydrochloric acid. The older approved methods of remov- 

 ing albumin by precipitation by mercuric chloride and 

 mercuric nitrate or phosphotungstic acid are in comparison 

 unquestionably valuable methods 43 ; the author confesses he 

 could not well dispense with them. When the albumin has 

 been separated, there is no further difficulty in the actual es- 

 timation of the sugar in the highly concentrated fluid by some 

 one of the reduction methods, or by polarization or fermenta- 

 tion in the usual way. Comparison of these procedures 

 show that the old Fehling's method and the reduction meth- 

 ods of Bertrand and Kumagawa-Suto give practically the 

 same results, while the hydroxylamine method of Bang yields 

 higher figures. 44 Tachau has proposed a modification of 

 Knapp's method, consisting of adding excess of cyanide of 

 mercury, separating the reduced mercury, then precipitating 

 the mercury which remains in solution and weighing it. 45 

 Attempts have also been made to use various color re- 



40 Cf. P. Rona and L. Michaelis, Biochem. Zeitschr., 16, 60, 1909. 

 41 K. Mockel and E. Frank (Wiesbaden), Zeitschr. f. physiol. Chem., 65, 

 323, 1910; 69, 85, 1910. 



42 1. Bang, H. Lyttkens and J. S'andgren (Lund) , Zeitschr. f. physiol. Chem., 



65, 497, 1910. 



* B. Oppler, Zeitschr. f. physiol. Chem., 64, 393, 1910; J. J. R. Macleod, 

 Jour, of Biol. Chem., 5, 443, 1909; H. Bierry and Portier, C. R. Soc. de Biol., 



66, 577, 1909. 



44 Cf. I. Bang, Biochem. Zeitschr., 7, 327, 1908; D. Takahaschi, Biochem. 

 Zeitschr., 37, 30, 1911. 



46 H. Tachau ( Schwenkenbecher's Clinic and Embden's Lab., Frankfurt 

 a. M.), Deutsch. Arch. f. klin. Med., 102, 597, 1911. 



