380 
Journal of Agricultural Research 
Vol. XXVI, No 8 
in sterile normal salt solution and then passed through filter paper to 
prevent the addition of organisms in large masses. After standing at 
room temperature till next morning it was placed in the incubator at 
37 0 C. until 2 p. m. 
In this test the plates of each dilution were run in duplicate as in the 
others, but in this case one plate of each dilution was plated out on Bacto- 
purple lactose agar. This is a medium prepared by the Digestive Fer¬ 
ments Co. and contains 0.0025 part dibromcresolsulphonephthalein as 
an indicator. When neutral this medium is a beautiful purple, but the 
least formation of acid turns it yellow. If but a few colonies of acid- 
producing organisms are present, they will appear as yellow colonies 
on a background of purple. An abundance of acid colonies turns the 
entire medium yellow. 
No count was made of the colonies on these plates, there being hun¬ 
dreds of thousands from the untreated milk. All of the plates to which 
chlorin had been added showed considerable decrease in bacteria. In 
only two plates did the medium remain purple. In the 1 riooo dilution 
of chlorin water and of sodium hypochlorite all of the B. coli were killed, 
but in the 1:1000 of calcium hypochlorite and in the dilutions of 3000, 
6000, and 10000 from all three sources, enough B. coli remained alive and 
viable to change the purple medium to yellow. 
A series of tests involving a change in the time of action of the three 
sources of active chlorin was then undertaken. The milk used was inocu¬ 
lated with about half of a 24-hour culture of B. coli communis and incu¬ 
bated for six hours at 37 0 C. before the chlorin was added. 
Table IX .—Time factor in germicidal action of chlorin water , sodium hypochlorite, and 
calcium hypochlorite 
Source of chlorin. 
Time 
acting. 
Active chlorin. 
Bacteria. 
Bactose purple 
lactose agar. 
Chlorin water. 
Hours. 
X 
I:IOOO 
7, OOO 
Unchanged. 
> Do. 
X 
1:3000 
160, OOO 
Yellow. 
Do. 
X 
i:6000 
350, OOO 
Do. 
Do. 
X 
i:10000 
630, OOO 
Do. 
Sodium hypochlorite. 
I X 
Untreated. 
1:1000 
1, 500, OOO 
140, OOO 
Do. 
Unchanged. 
Do. 
I X 
1:3000 
525,000 
Yellow. 
Do.. 
J X 
1:6000 
777, 000 
Do. 
Do. 
*X 
1:10000 
770, OOO 
Do. 
Calcium hypochlorate. 
IX 
Untreated. 
1:1000 
1, 500, OOO 
I, OOO, OOO 
Do. 
Yellow. 
Do. 
iX 
1:3000 
450, OOO 
Do. 
Do. 
IX 
1:6000 
577 )5oo 
Do. 
Do. 
i X 
1:10000 
630, OOO 
Do. 
Do. 
*9 
Untreated. 
1:1000 
1, 500, OOO 
4, 000 
Do. 
Unchanged. 
Do. 
19 
1:3000 
721, OOO 
Yellow. 
Do. 
T 9 
1:6000 
1, 610, OOO 
2, 625, OOO 
Do. 
Do. 
*9 
1:10000 
Do. 
Untreated. 
10, 920, OOO 
Do. 
The time factor in these tests is most noteworthy, showing an agree¬ 
ment with the results stated in Table V, in that chlorin water produces 
fully as good effects in 45 minutes as sodium hypochlorite does in 1 hour 
and 30 minutes and calcium hypochlorite in 19 hours. 
