EXPERIMENT NO. 4— Continued. 
[+ means growth; — no growth.] 
Organism. 
How exposed. 
Time of exposure in 
minutes, and results. 
5 
10 
20 
30 
60 
B. coli communis 
Glass 
— 
— 
— 
— 
B. subtilis 
do 
B. pyocyaneus 
Filter paper 
+ 
+ 
- 
B. typhosus . . 
do 
B. coli communis 
do 
B. subtilis 
do 
B. coli communis 
Wilson method 
+ 
- - 
The minimum temperature and relative humidity in the foregoing 
experiments were 77° F. and 72 per cent, respectively; under these 
conditions the .germicidal results were very satisfactory. The non- 
spore-bearing organisms exposed on slips of filtered paper and pieces 
of glass were killed within a few minutes. The spores of B. subtilis 
exposed in the same manner were likewise killed within a compara- 
tively short time. The time required to kill the same organisms 
exposed the ‘Wilson was more than twice as long as that required 
with the other methods of exposure. 
Although only 400 c. c. of formalin were used in Experiment No. 1, 
the results are about the same as with the other experiments in which 
600 c. c. were used. Comparing this same experiment (No. 1) with 
the following one (No. 5) in which 800 c. c. of formalin were used, the 
germicidal results of exposures on filter paper are in favor of the 
former experiment, due to the higher temperature and humidity in 
this experiment; the results of exposures by the Wilson method are 
in favor of the latter experiment, due in all probability to the increased 
percentage of formaldehyde in the air, favoring penetration. 
EXPERIMENT NO. 5. 
Formalin-permanganate method. 
Formalin, 800 c. c. 
Permanganate, 400 grams. 
Capacity of room, 2,000 cubic feet. 
Quantity of formaldehyde used per cubic foot, 0.1426 gram. 
Quantity of formaldehyde found per cubic foot, 0.0505 gram. 
(Determination made by drawing air from the room, beginning 12 minutes after mixing the 
formalin and permanganate, and consuming 1 hour 32 minutes in the drawing.) 
Yield of formaldehyde, 34.41 per cent. 
Weather: Light, westerly wind; almost clear. 
Tempera- 
ture. 
Relative 
humidity. 
Absolute 
humidity 
(grams per 
cubic foot) . 
Before mixing HCHO and KMn 04 
° F. 
69 
Per cent. 
63 
4. 86 
After 10 minutes 
70 
88 
6. 86 
After 1 hour 
70 
81 
6. 46 
See Note, Experiment No. 1. 
