38 
Although the relative humidity in the above experiment was 62 
per cent and the temperature 79.5° F., the spores of B. subtilis were 
not killed within two hours; this was due in all probability to the- 
humidity being insufficient. The other organisms were killed within 
a few minutes. The humidity was increased 25 per cent by the mois- 
ture given off. but this did not seem to answer the purpose in case of 
the spores. 
The following two experiments (Xos. 16 and 17) were done during 
colder weather than the foregoing. The results show a marked de- 
crease in the percentage of formaldehyde obtained, as well as dimin- 
ished germicidal powers. About the same hazy appearance in the 
room was observed as with the undiluted formalin-permanganate 
method under similar conditions of temperature, but the deposit of 
paraform was not so marked. 
Comparing experiments Xos. 7 and 8 (undiluted formalin-permanga- 
nate) with Xos. 16 and 17 it will be observed that, although the tem- 
perature was lower in the latter experiments than in the former, the 
germicidal results are in favor of the latter experiments. 
EXPERIMENT NO. 16. 
Dilute formalin-permanganate method. 
Formalin.. 600 c. c. 
Water, 300 c. e. 
Permanganate, 375 grams. 
Capacity of room, 2,000 cubic feet. 
Quantity of formaldehyde used per cubic foot, 0.107 gram. 
Quantity of formaldehyde found per cubic foot. 0.01626 gram. 
(Determination made by drawing air from the room, beginning 15 minutes after mixing the for- 
malin and permanganate, and consuming 1 hour 5 minutes in the drawing, j 
Yield of formaldehyde, 15.2 per cent. 
Weather: Light clouds, northwest breeze. 
Tempera- 
ture. 
Relative 
humidity. 
Absolute 
humidity 
j (grams per 
cubic foot) . 
Before mixing HCHO and KMnO! 
° F. 
39 
Per cent . 
51 
1.39 
After 10 minutes 
42 
92 
2. 82 
After 3 hours 
40 
S3 
2.36 
See Note, Experiment No. 9. 
[4- means growth; — no growth.] 
Organism. 
How exposed. 
Time of exposure in minutes, 
and results. 
!0 
20 
30 
45 
60 
90 
120 
ISO 
B. coli communis 
Filter paper 
_ 
B. typhosus 
B. subtilis.... 
do 
-s- 
-r 
4- 
+ 
— 
+ 
4- 
B. coli communis 
Wilson method 
+ 
4- 
4- 
4- 
i + 
_L_ 
- 
B. subtilis 
do 
-r 
+ 
+ 
"b 
+ 1 
4- 
4- 
- 
