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LETTER TO THE EDITOR

mobile free fatty acids, produced from the salts by the ascending acetic acid f r o n t o f the developing solvent mixture, resulting in a sharp trailing edge. The original solvent system of benzene, diethyl ether, ethyl acetate, acetic acid (80:10:10:0.2) has been replaced by toluene, diethyl ether, ethyl acetate, and acetic acid (80:10:10:0.75). The greater proportion of acetic acid is necessary with the sodium bicarbonate impregnated silica gel layers to achieve similar Rf values to the original thin layer system. The positions of separated lipids are identified under UV light after spraying the plates lightly with a methanolic solution containing 0.025% dichlorofluorescein and 0.005% rhodamine B. This spray reagent is a simplification

ERRATUM In "Effects of Different Culture Media and Oxygen upon Lipids of Escherichia coli K-12" by William F. Naccarato, John R. Gilbertson, and Rose A. Gelman (Lipids 9:322 [19741), an error occurred in the third sentence in the second paragraph of the " I n t r o d u c t i o n . " The word anaerobically should be changed to aerobically. The sentence should read: "If this were true, 2-alkanols should disappear when E. coli are grown aerobically in media with glucose as the only carbon source."

LIPIDS, VOL. 9, NO. 7

of that proposed by Jones, et al. (J. Chromatogr. 23:172 [ 1 9 6 6 ] ) and gives good contrast between lipid and background in UV light (366 nm). Glass troughs originally used for holding the developing solvent have been replaced by ones of stainless steel. These measure 22 cm long, 4 cm wide at the base, tapering to 1.7 cm at the open top, and are made from welded stainless steel sheet (22 gauge, 18/8 quality). B. TUCKLEY J.E. STORRY National Institute for Research in Dairying Shinfield Reading, England RG2 9AT [ Received January 16, 1974]