18 
The foreo'oing results demonstrate that under the most favorable 
conditions zinc chloride is inefficient as a germicide for practical pur- 
poses. as it will be observed that the pyogenic organism Stcqjhylococcus 
pyogenes aureus lives for 50 minutes in a strength of 10 per cent and 
'20 minutes in a strength of 25 per cent. 
Bacillus coll conirnunis was viable after exposure for 20 minutes in 
a 10 per cent solution and after 8 minutes in a 25 per cent solution. 
The Yiljrio cholerse was killed in a 5 per cent solution within T min- 
utes and within 2 minutes in a 10 per cent strength. This is the only 
organism that was destroyed by a reasonable strength in a reasonable 
time. 
In the experiments for determining the germicidal action of zinc 
chloride on the Bacillus coli cornrnunis it was desired to ascertain 
whether the organisms were really dead in the time and strengths that 
apparently were germicidal or simply overcome and still capable of 
reviving in case the zinc chloride was immediately removed or neu- 
tralized. Consequently some of the organisms were treated with 
ammonium sulphide for a few seconds, washed in distilled water, and 
planted in bouillon. It was not observed, however, that this appre- 
ciably altered the time required for germicidal action, indicating that 
the organisms were really killed. 
To ascertain the germicidal value of zinc chloride in the presence of 
organic matter as compared with its value in distilled water, experi- 
ments were performed with this end in view. 
Equal percentages of zinc chloride were prepared in distilled water 
and nutrient bouillon. I’espectiveh'. and inoculated with diflerent 
organisms, after which the technique was the same as above described. 
The results are shown in the following tables, where comparisons ma}’ 
be made. 
Table A . — Germicidal residts ichen the B. prodigiosus v:as exposed in percentages of zinc 
chloride prepared in distilled icater. 
Percentage 
zncr. 
Time of exposure. 
5 min- 
utes. 
10 min- 
utes. 
20 min- 
utes. 
45 min- 
utes. 
1 2 
hour, hours. 
3 
hours. 
5 
hours. 
! 7 
hours. 
5 
10 
25 
- 
-r 
1 T-l- 
- 
- 
“ 1 
Table A1 . — Same as Table A, when nutrient bouillon was used instead of distilled water. 
Percentage 
ZnCh. 
Time of exposure. 
5 min- lOmin- 20min- 
utes. utes. utes. 
45 min- 1 
utes. hour. 
2 3 
hours, hours. 
5 7 
hours, hours. 
18 
hours. 
5 
10 
25 
1 
- - -i- 
j- - 
- - 
“h 4- 
— 
- - - 
-L — 
- 
- 
- ' 
