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INDUSTRIAL A N D ENGINEERING CHEMISTRY
wash water from forty bottles was used, which was plated in the manner already described. The concentrations of the alkali were higher in the second experiment than in the first. (Table 11) Figure 3 is a graphical presentation of this data in which it will be seen there is a close parallel to the experiments with sodium hydroxide, although the germicidal action was less. The 0.5 per cent solution of p H 11 was only slightly germicidal; that of 0.7 per cent was but very little better. The concentrations of 1.0 and 2.0 per cent were quite efficient, although to get sterility the 2.0 per cent solution was needed for periods of 3 to 5 m i n u t e s . The p H v a l u e of t h e s e two solutions was 11.4 and 11.6, r e s p e c t i v e l y . T h e germicidal efficiency was about 85 per cent for the 0.5 per cent solution, 95 per cent for the 0.7 per 0 cent, and better than Tme in minutes Figure 5-Relation between Temperature 99 per cent for the of 0.5 Per C e n t of NaOH a n d T i m e as and 2.0 per Cent SOlUMeasured b y Bacteria Surviving tions. It is thus seen that the less alkaline solutions are not so efficient as the so-
not quite so apparent in Figure 4 as they are in Figure 2.
a n d 54.4' C. The p r o c e d u r e was the same a s outlined above in every other respect. The results are given in Table I11 and in Figures 5 and 6. The relation between t e m p e r a t u r e / / and time is brought out here. The "iso/ I / lethal" lines are again 1 in e6.v i d e n c e in Fig- mJj!-~/id,&4
