10 



IVAN C. HALL 



alkaline methylene blue solutions in the presence of these certain 

 organic ingredients of culture media is quite independent of the 

 presence or absence of the acid ions mentioned. 



Neutral and n/20 HCl solutions of 1 per cent levulose, glucose, 

 lactose, maltose, sucrose, raffinose, inulin, dextrin, mannitol and, 

 dulcitol, (all Merck's highest purity), with 0.00005 gram meth- 

 ylene blue were tested also for decolorization by heating in a boil- 

 ing water bath for ten minutes, with negative results. Glucose, 



TABLE 1 



Correlalion of Fehlin.g's test and decolorization of methylene blue by alkalinized 



sugar solution 



BEDUcrriON 



N 



feeling's 



TEST* 



Levulose . 

 Glucose. . 

 Lactose . . 

 Maltose.. 

 Sucrose. . , 

 Raffinose. 

 Inulin. . . . 

 Dextrin. . 

 Mannitol. 

 Dulcitol. . 



+ 

 + 

 + 

 + 



* Quoted from Hawk-Practical Physiological Chemistry. Blakiston, Phila- 

 delphia, 1907. 



Reduction indicated by -\-. 



No reduction during ten minutes in boiling water bath indicated by — . 



levulose, lactose, and maltose solutions decolorized methylene 

 blue, however, in one or two minutes in n/1000 NaOH, but 

 raffinose, inulin and dextrin solution required n/100 NaOH 

 while sucrose, mannitol, and dulcitol, failed to decolorize meth- 

 ylene blue in even n/3 NaOH. 



These results with ten representative carbohydrates of repu- 

 table purity suggested the following attempt to correlate meth- 

 ylene blue reduction with that of copper sulphate in Fehling's 

 test as in table 1 . 



There is apparently a well defined correspondence between 

 those carbohydrates whose reducing action is shown in Fehling's 



