EXPERIMENT STATION REPORTS. 



177 



TABLE 6. 



Sets 6a, 6b and 6c, table 6, were Smith's fermentation tubes run in triplicate and treated according to procedures A. B. and C. 



TABLE 7. 



Set 1, table 7, was soft glass test tubes filled with conductivity water and autoclaved for thirty minutes at 15 pounds pressure 

 This procedure was repeated six times and the pH reading taken after each time autoclaved. Set 2, table 7, was hard glass test 

 tubes treated the same as Set 1, table 7, while Set 4, table 7, was Erlenmeyer flasks treated the same as Set 1, table 7. All sets 

 were run in triplicate. 



DISCUSSION. 



It is very evident in comparing the results of the experiments set forth in 

 the preceding tables that there is a decided difference in the hydrogen-ion 

 concentration of the buffered and non-buffered solutions after these solutions 

 have been added to glassware and the glassware autoclaved for thirty minutes 

 at fifteen pounds pressure. This shows that there is alkali in the glassware 

 sufficient to affect the hydrogen-ion concentration of non-buffered solutions 

 to a considerable extent. It also shows that the glassware used still gives off 

 some free alkali even after it has been autoclaved for several times. In the 

 case of the buffered solution the effect of the alkali given off from the glass- 

 ware on the hydrogen-ion concentration was negligible. In fact, the broth 

 in most eases showed an acid reaction. This is entirely in accord with the 

 recent findings of Foster and Randall (4) who showed that broth in the 

 neutral range (6.6 — 7.4) undergoes but slight changes in hydrogen-ion con- 

 centration. The maximum change being about 0.4 pH and in the majority 

 of. cases not over 0.2 pH. The experiments also show that more alkali is 

 given off from soft glassware than from hard glassware. 



Treating the glassware with cleaning solution before autoclaving with the 

 buffered and non-buffered solutions had no noticeable effect on the hydrogen- 

 ion concentration of either solution. In each case the hydrogen-ion concen- 

 tration of the glassware that had been treated with cleaning solution and of 

 glassware that had not been so treated was practically the same. In other 

 23 



