20 
K. ÜSllIMA AND M. AKIIZUMI. 
water bath at a low temperature, under constant stirrint^, until a syrupy 
solution was obtained. The syrup thus prepared was used for the indenti- 
fication of Creatinin and is desij^natetl as syrup I in the statement beyond. 
Color Reactions. 
The following three reactions were made use of for the determination 
of Creatinin. 
a) Jaffe's reaction. An intensive red color is produced when to the aqueous solution 
of Creatinin are added, first, a little picric acid and, then, a few drops of caustic alkali. The red 
color disappears on adding excess of alkali or on acidifying the solution with acetic acid or with 
hydrochloric acid. The red color appears soon after the addition of caustic alkali even in cold. 
The intensity varies from orange red to dark blood red according to the amount of Creatinin 
present. The characteristic red color will soon change into yellow if too much alkali is used and 
particularly when exposed to light. The presence of glucose does not interfere with this reaction, 
since the similar red color produced by glucose itself appears much more slowly than in the case 
of Creatinin. It should be remembered in this connection that aceton. laevulinic acid and furfurol 
give the Jaffe's reaction. 
b) Weyl's reaction. When a freshly prepared, very dilute solution of sodium 
nitroprusside is added to the aqueous solution of Creatinin until it gives a distinct yellow color, and 
then a few drops of dilute caustic alkali are added, the solution gives a ruby red color. The 
color becomes lighter as the time passes on until after a short time it assumes a straw-yellow 
color. Salkowski i' asserted that ruby red color can not be considered as characteristic because 
this color easily changes into yellow. In the course of our investigation we have observed the 
same fact, in confirmation of Sa Ik ow ski's view. Furfurol gives the same color with sodium 
nitropruside and caustic alkali as in the case of Creatinin, the only difference being that the red 
color given by furfurol remains unchanged for a much longer time. I^aevulinic acid gives a color 
similar to that of Creatinin. Sulphide gives purple color under the same conditions and makes 
the Creatinin reaction obscure if both arc present at the same time. 
c) Salkowski's reaction. If the yellow solution obtained in testing \V e y 1' s 
reaction, is acidified with acetic acid and heated, it turns first green, then blue and finally the 
precipitate of Prussian blue is separated. Hydantoin gives the same reaction but not creatin. 
Laevulinic acid and furfurol give the same final blue color and precipitation, Imt the solution is 
turned purple directly after acidifying with acetic acid and before heating. The reagents alone 
will give the same final color and precipitation if heated before acidifying. 
l) Hoppe-Seyler's Zs. Physiol. Chem., Strassburg, 4, (1880), p. 133. 
