52 
EXPERIMENT NO. 27— Continued. 
[+ means growth, — no growth.] 
Organism. 
B. coli communis . 
B. typhosus 
B. subtilis 
B. coli communis . 
B. subtilis 
How exposed. 
Filter paper 
do 
do 
Wilson method. 
do 
Time of exposure in minutes, 
and results. 
+ 
+ 
+ 
4- 
+ 
20 
30 
45 
60 
120 
180 
+ 
- 
- 
- 
- 
- 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
— 
- 
+ 
+ 
+ 
+ 
+ 
+ 
These results agree rather closely with those of the formalin-per- 
manganate and retort methods and especially with the latter method, 
except that the retort liberates a slightly larger percentage of formal- 
dehyde than does the autoclave. For disinfecting purposes the three 
methods give about the same results, provided the temperature and 
humidity are high. A low temperature affects the autoclave method 
in about the same way that it does the retort method. The disadvan- 
tages of the autoclave are that more or less complicated apparatus is 
required which is cumbersome to handle and that considerable time is 
consumed in vaporizing the formalin, although not half so long as 
with the retort. 
V. SHEET-SPRAYING METHOD. 
Two sheets, about 4^ by 6^ feet, were hung up in the room in a 
slanting position at an angle of about 45°. It was found advantage- 
ous to have them just damp to the touch when hung up, as the for- 
malin was absorbed by the fibers more quickly and had very little 
tendency to run off the sheet. Six hundred c. c. of formalin were 
sprayed uniformly and the door closed. 
Chemical determinations . — Different intervals were allowed to elapse 
after spraying the sheets before beginning to draw air from the room. 
The method of procedure has been described. The results are given 
in the following table : 
Table 5. — Experiments with the sheet-spraying method. 
Number. 
Temperature of room 
before experiment. 
Time between closing 
room and drawing 
air. 
Time required to 
draw air. 
Volume of air drawn, 
in liters. 
Relative humidity 
before experiment. 
Relative humidity 
after closing room. 
Gain in grains of 
moisture per cubic 
foot. 
Abs. formaldehyde 
used per cubic foot. 
Abs. formaldehyde 
found per cubic foot. 
Per cent. 
Condition of wind 
° F. 
h. m. 
h. 
771 . 
Gm. 
Gm. 
Io 
76.5 
1 26 
1 
13 
10 
72 
a 83 
1.6 
0. 107 
0.02576 
24.07 
No wind. 
lb 
3 47 
1 
8 
10 
.107 
.03262 
30.48 
Do. 
Ila 
78 
1 40 
1 
15 
10 
3 
b 85 
.107 
.0252 
23. 55 
Gentle breeze. 
116 
4 5 
1 
7 
10 
.107 
.0305 
28.50 
Do. 
lie 
23 30 
1 
17 
10 
.107 
.02225 
20.80 
No wind. 
III 
43.5 
1 30 
1 
25 
11 
52 
431 
0.05 
.107 
.00345 
3. 16 
Gentle breeze. 
a After 5 hours. b After 3 hours. 
