19 
5T,< 
•% 
* -.Table B . — Germicidal results when the B. pyocyaneus was exposed in percentages of zinc 
; chloride prepared in distilled vxder. 
Percentage ZnCL. 
Time of exposure. 
10 min- 
utes. 
20 min- 
utes. 
30 min- 
utes. 
2 
hours. 
3 
hours. 
5 
hours. 
7 18 
hours, hours. 
I 
a 
+ 
-1_ 
+ 
-f 
T- 
10 
+ 
4- 
+ 
+ 
— 
— 
— — 
25 
-e 
+ 
— 
■ 
— 
— 

Table B1 . — Same as Table B, when nutrient bouillon teas used instead of distilled water- 
Percentage ZnCL. 
Time of exposure. 
10 min- 
utes. 
20 min- 
utes. 
30 min- ! 2 
utes. hours. 
3 
hours. 
5 
hours. 
7 
hours. 
18 
hours. 
5 
-U 
+ 
+ 1 + 
-t- 
-f 
+ 
+ 
10 
-i- 
T- 
-f- 1 -r 
-f 
— 
— 
25 
_i_ 
+ 
~ i “ 
— - 
— 
— 
— 
These results, confirmed by repeating several times, show that when 
zinc chloride is prepared in nutrient bouillon its germicidal value is 
not appreciabh" influenced by the organic matter contained therein as 
compared with its value when prepared in distilled water. 
As has already been stated, zinc chloride produces a hea\y white pre- 
cipitate when added to nutrient bouillon. Consequently experiments 
were performed to determine the relative germicidal properties of this 
precipitate as compared with those of the clear transparent portion 
that remains above. A 10 per cent solution of zinc chloride in nutrient 
bouillon was prepared and allowed to settle. The clear supernatant 
portion was then siphoned off and 10 c. c. of it placed in a test tube. 
Ten cubic centimeters of the precipitate was placed in another test 
tube. Beth tubes were then inoculated with a 2T-hours-old agar culture 
of Bacillus pyocyaneus,^ after which plants at definite intervals were 
made from each tube into nutrient bouillon in the usual way. 
The results of the inoculations made eveiy hour show that the 
Bacillus pyocyaneus was killed within 3 hours in the tube containing 
the supernatant portion, and within T hours in the tube containing 
the precipitate, indicating that the supernatant portion has slightly 
greater germicidal powers than the precipitated portion. A similar 
experiment in which Bacillus typhosus was substituted for Bacillus 
- pyocyaneus shows that this organism was killed in both tubes within 
2 hours. 
GERMICIDAL INFLUENCE OF ZINC CHLORIDE ON SEWAGE. 
For this work an average sample of sewage was selected. Definite 
quantities were placed in Erlenmeyer flasks and heavily inoculated 
with a water}^ ‘suspension of a 21:-hours-old agar culture of Bacillus 
pyocyaneus. Various definite percentages of zinc chloride were then 
