32 
A reduction in temperature produces about the same hazy appear- 
ance in the room that is observed in case of the undiluted formalin- 
permanganate, retort, and autoclave methods, but the deposit of 
paraform is less than in the undiluted formalin-permanganate method. 
This result may be due to the decreased percentage of formaldehyde 
which is given off or to the decreased polymerization attendant upon 
the amount of water added. The percentages obtained by the diluted 
formalin-permanganate method are relatively higher, considering the 
temperatures, than is the case with the undiluted formalin-permanga- 
nate method, as will be seen by comparing experiments VIII and IX, 
Table 2, with VI and VII, Table 1. The difference in percentage 
obtained in experiments VIII, temperature 39° F. (15.2 per cent) 
and IX, temperature 41° F. (11.53 per cent), Table 2, is probably due 
to the larger quantity of water added in the latter experiment. 
Germicidal properties . — The method of procedure was the same as 
with the undiluted formalin-permanganate method already described. 
A summary of conditions and results is given in each of the following 
experiments : 
EXPERIMENT NO. 9. 
Dilute formalin-permanganate method. 
Formalin, 600 c. t. 
Water, 600 c. c. 
Permanganate, 450 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, 0.0272 gram. 
(Determination made by drawing air from the room, beginning 17 minutes after mixing the 
formalin and permanganate, and consuming 1 hour 20 minutes in the drawing.'' 
Yield of formaldehyde, 25.4 per cent. 
Weather: Light northerly breeze, clear. 
Tempera- 
ture. 
Relative 
humidity. 
Absolute 
humidity 
(grams per 
cubic foot) . 
° F. 
Per cent. 
Before mixing HCHO and KMn 04 
81 
81 
9.13 
After 10 minutes 
82 
94 
10.92 
After 2 hours 
82.5 
90 
10.62 
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. 
[+ means growth; — no growth.] 
Organism. 
How exposed. 
Time of 
utes 
5 
10 
B. vyocyaneus 
Filter paper 
+ 
B. coli communis 
do 
+ 
B. dysenterise 
do 
+ 
+ 
B. subtilis 
do 
+ 
B. coli communis 
Wilson method 
+ 
B. subtilis r'. . 
do 
+ 
+ 
25 45 60 120 
+ ! 4 - 
