Inhibition of the growth of bacteria by sodium nitrite is largely dependent on the pH of the substrate upon which they are cultivated. Thus at pH 6.0, 0.02 per cent of sodium nitrite may entirely inhibit or strongly retard growth, while at pH 7.0 little or no inhibition is in evidence. There is a marked variation in the susceptibility of different bacteria to nitrite, and there appears to be no definite relationship between its effect in retarding growth and in inhibiting aerobic respiration.