21 
of the potassium hydrate by formic acid.” It seems highly proba- 
ble that the decomposition takes place essentially according to the 
following reaction : 4KMn0 4 + 3HCHO + H 2 0 = 4MnO ( OH) 2 + 2K 2 C0 3 
+ C0 2 (C0 2 ), and that the heat resulting from this reaction causes the 
liberation of formaldehyde gas from the remaining portion of the 
formalin. 
r « 
The reaction is more rapid the more finely powdered the perman- 
ganate crystals are, but in our experiments we used the small needle 
crystals of commerce without further powdering. 
The temperature and relative humidity of the air in the room 
were recorded before as well as at definite intervals after mixing the 
formalin and permanganate. This showed a considerable amount 
of moisture given off by the process. 
Many variations and conditions might have been tried, such as 
covering the pail with sheet asbestos to retain the heat, heating the 
pail before the experiment or placing it in hot water, powdering the 
permanganate crystals, etc., but as time is a factor we adopted those 
conditions which are least difficult to execute in disinfecting rooms. 
Before a new charge was put into the room all formaldehyde of 
the previous experiment was got rid of b}^ opening the doors and 
windows until no odor of formaldehyde was perceptible. 
Chemical determinations . — In making these determinations approx- 
imately fifteen minutes were allowed to elapse after mixing the form- 
alin and permanganate before beginning to draw air from the room. 
This seemed ample time for the reaction to cease and for the formal- 
dehyde gas to diffuse through the air of the room. The results are 
shown in the following table: 
Table 1. — -Experiments with the formalin-permanganate method. 
Number. 
Temperature of room 
before experiment. 
Formalin (35.66 per 
cent by volume). 
o 
G 
S 
M 
Time between mixing 
and drawing air. 
Time required to 
draw air. 
Volume of air drawn, 
in liters. 
Relative humidity be- 
fore experiment. 
Relative humidity 10 
minutes after mixing. 
Increase in grains of 
moisture per cubic 
foot. 
Abs. formaldehyde 
used per cubic foot. 
Abs. formaldehyde 
found per cubic foot. 
Per cent yield. 
Condition of 
wind, etc. 
°F. 
c. c. 
gm. 
tl. TO. 
•h. to. 
gm. 
gm. 
I 
71 
600 
300 
a 14 
1 10 
10 
72 
86 
1.47 
0. 107 
0. 04035 
37. 70 
Moderate wind. 
5 3 38 
1 21 
10 
. 107 
.0243 
22. 7 
Do. 
II 
69 
800 
400 
a 12 
1 32 
10 
63 
86 
2.0 
.1426 
.0505 
35. 41 
Slight breeze. 
b 22 17 
1 10 
11 
. 1426 
. 01722 
12.07 
Very slight 
breeze. 
III 
77 
400 
200 
15 
1 12 
10 
79 
85 
0.58 
.0713 
.025 
35.06 
Moderate wind. 
IV 
79 
600 
300 
17 
1 21 
10 
79 
94 
1.72 
.107 
.0419 
39.15 
Practically no 
wind; windows 
and doors of 
room pasted 
up. 
V 
62 
600 
300 
15 
1 15 
10 
55 
74 
1.17 
.107 
. 02685 
25.1 
No breeze. 
VI 
52 
600 
300 
15 
1 20 
10 
63 
78 
.54 
.107 
. 01186 
11.09 
No wind. 
