In a recent study of the utilization of the nitrogen of hydroxylamine and of oximes by Azotobacter vinelandii, Novak and Wilson (1948) observed that, although this organism would not grow in the presence of free hydroxylamine, the inhibition disappeared after 2 to 3 days of incubation. Preliminary investigation indicated that this response arose from decomposition of the free base to nontoxic products presumably including ammonia rather than from adaptation of the organism to the source of

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... gen. Quantitative study of the properties of hydroxylamine in aqueous solution has verified this interpretation and has allowed investigation of the possible utilization of the free base or its salts when present in noninhibitory concentrations. METHODS Essentially the same methods as those described by Novak and Wilson (1948) were used except that when total cell nitrogen was less than 50 micrograms per sample the microdiffusion technique of Conway and Byrne (1933) was employed. Although hydroxylamine in moderate concentration reduces the mercury in Nessler's solution, if the concentration is 20 ;g per ml or less it does not interfere but reacts quantitatively with the reagent. To determine ammonia in the presence of hydroxylamine, free hydroxylamine is reduced to the noninterfering level; then total ammonia plus hydroxylamine is estimated by the reaction with Nessler's reagent. Free hydroxylamine is determined by Blom's (1928) method and the ammonia by difference. If the concentration of the hydroxylamine is too high, either in absolute value or in relation to ammonia (the ammonia to hydroxylamine ratio should be at least 5), it is reduced by the addition of pyruvic acid to form the oxime. RESULTS AND DISCUSSION Stability of hydroxylamine. Although previous investigators, for example Blom (1928), comment on the instability of hydroxylamine, few results are available for physiologically significant conditions. Table 1 supplies such data, which show that the decomposition depends both on pH and temperature. Decomposition appeared to be somewhat more extensive in Burk's N-free medium than in water, but this effect may arise from differences in the buffering capacity of the two. Further trials established that the decomposition was not materially in-