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Notes 2051 tin in boiling acid solution.1 It was assumed that this coloration was due to the formation of ß-(5pyrrolenyl) -isatin or pyrrole blue B. Recently it has been shown,2 however, that pyrrole blue B in glacial acetic acid has a maximum absorption at 680-690 µ while the maximum absorption in the microreaction was observed in the range for 510-560 m/i. For a more exact comparison the absorption spectrum of the color reaction was determined in a Hilger-Nutting spectrophotometer. The resulting curve A in Fig. 1 is quite different from the spectrum of pyrrole blue B, shown in curve B. The logarithm of specific extinction K is calculated per grams of pyrrole per liter. Thus the compound formed in the color reaction is certainly not pyrrole blue B but seems to be its decomposition product which also forms when solutions of pyrrole blue B are standing for some time. It has been indicated2 that the decomposition product has an absorption maximum at 520 µ.The author is greatly indebted to the Chemistry Department of the University of Michigan for the permission to use a spectrophotometer and to Dr. F. F. Blicke for the supply of pyrrole.

Communications to the Editor Vol. 69 a similar procedure and shown to be identical with the higher-melting isomer B from streptomycin B by melting point (161-162°, no depression on admixture of isomer B), rotation ([a]25D -65°( c, 1.1 in chloroform)), and analysis (