23 
This change of state in the formaldehyde, of course, very mate- 
rially reduces the percentage obtained in our determinations, as is 
shown in experiments VI and VII, table 1. In VI, as the tempera- 
ture (62° F.) was close to the point where polymerization seems to 
begin, 25.1 per cent was found; but in VII (temperature 52° F.) only 
11.09 per cent was obtained. 
These results can not be interpreted as positively representing the 
percentage of gas actually existing as such in the air during the time the 
determinations were made, since it is possible that all the paraform or 
other changed formaldehyde was not eliminated from the determina- 
tions, although a small pledget of cotton was placed in the funnel of 
the drawing tube to prevent the paraform, etc., from passing out in 
the air drawn. The cotton pledget was placed in the funnel of the 
drawing tube only when working at a reduced temperature and when 
some polymerization was apparent. 
Germicidal properties . — For the purpose of determining the germi- 
cidal properties of formaldehyde liberated by this method the organ- 
isms were placed in the wire trays in the room before mixing the 
formalin and permanganate, and the time of exposure counted from 
the time the reaction and liberation of the formaldehyde began. 
As most of the gas is given off in the first minute or two, the reason 
for this is evident. 
The method of preparing the organisms, making the exposures, etc., 
have been described. A summary of conditions and results is given 
in each of the following experiments : 
EXPERIMENT NO. 1. 
Formalin-permanganate method. 
Formalin, 400 c. c. 
Permanganate, 200 grams. 
Capacity of room, 2,000 cubic feet. 
Quantity of formaldehyde used per cubic foot, 0.0713 gram. 
Quantity of formaldehyde found per cubic foot, 0.025 gram. 
(Determination made by drawing air from the room, beginning 15 minutes after mixing the 
formalin and permanganate, and consuming 1 hour 12 minutes in the drawing.) 
Yield of formaldehyde, 35.06 per cent. 
Weather: Moderate breeze from west; almost clear. 
Tempera- 
ture. 
Relative 
humidity. 
Absolute 
humidity 
(grams per 
cubic foot). 
Before mixing HCHO and KMnOi 
° F. 
77 
Per cent. 
79 
7.88 
After 10 minutes 
77 
85 
8.46 
After 2 hours 
78 
79 
8. 12 
Note. — In all the experiments with this method the temperature, humidity, and time of exposure of 
organisms are given from the moment of mixing the formalin and permanganate. 
