June i6,1923 Azotobacter Flora and Nitrogen Fixing Ability of Soils 911 
Tabi,E III .—Effect on electrode readings of varying the method of saturating the electrode 
and suspension with hydrogen 
Hydrogen run over electrode continuously. 
Soil No. 
Electrode number— 
I 
2 
3 
4 
5 
Average. 
401. 
615 
608 
595 
601 
619 
608 
362. 
557 
550 
552 
553 
554 
553 
378. 
542 
544 
541 
541 
538 
541 
377 . 
S 45 
542 
549 
541 
351 
546 
1,000 cc. hydrogen run over electrode. 
Soil No. 
Electrode number— 
I 
2 
i 
' 3 
4 
5 
Average. 
401. 
“ 597 
! 
« 6II 
1 
0 61I 
a 615 
61I 
609 
7.62 . 
55 ° 
550 I 
550 
550 
550 
378. 
543 
542 i 
530 
540 
538 
539 
377 . 
550 
^ 530 1 
1 
“ 537 
“538 
554 
542 
1,000 cc. hydrogen run over electrode, then run continuously. 
Soil No. 
Electrode number— 
I 
2 
3 
4 
5 
Average. 
401. 
629 
620 
622 
624 
614 
622 
g62. 
553 
553 
557 
555 
554 
378. 
543 
543 
533 
543 
530 
538 
377 . 
555 
554 
550 
552 
552 
553 
“ These samples apparently did not have stifhcient hydrogen passed through to saturate the electrode and 
suspension, as is evidenced by the increased reading when further passage of hydrogen took place. 
Tabl^ IV .—Difference in potential of same soil determined on different dates,'^effect of 
varying ratio of soil to water, and variations in difference in potential as determined 
with five different electrodes 
Soil No. 
Ratio of soil to 
water 
Electrode number— 
I 
2 
3 
4 
5 
Average 
390 ®. 
Ito s. 
534 
544 
541 
539 
532 
537 
390 ^. 
I to 5... 
538 
540 
539 
532 
536 
537 
369. 
Ito 5. 
678 
679 
677 
678 
676 
678 
395 . 
I to 5. 
530 
528 
528 
528 
529 
529 
395 . 
I to 10. 
536 
533 
536 
536 
539 
536 
387. 
I to 5. 
493 
494 
493 
493 
493 
493 
387. 
I to 10. 
495 
494 
494 
495 
494 
494 
384. 
I to 5. 
650 
653 
650 
652 
652 
651 
397 . 
I to 5. 
563 
566 
567 
566 
566 
566 
April 5. 
* May 31. 
