In the course of a comparative study of several methods for the determination of sugar in blood, the results of which will be recorded elsewhere, it became desirable to investigate the reaction betsveen copper sulfate and potassium iodide which is concerned in a number of methods for sugar determination (Bang (l), Maclean (2), Scales (3), Lehmann (4), Riegler (4), Peters (4), Kendall (5)). In c...