9 
cars and a number of experiments conducted with various methods of 
liberating the gas. 
As our studies progressed it became evident that changes in climatic 
conditions caused a wide variation in our results. Consequently our 
work was continued through the different seasons of the year in order 
to observe the influence of temperatures, humidity, wind, etc.; but as 
the germicidal power of the gas during cold weather was ver}^ unsatis- 
factory, only a limited number of experiments were necessary during 
the winter season. 
A number of experiments with the formalin-permanganate method 
were performed in large glass bottles. In this manner it was possible to 
control or eliminate some of the atmospheric conditions with which 
we had to contend in the room and cars. Particular attention was 
given to the influence of humidity upon the bactericidal power of 
formaldehyde, as well as to the percentage of formaldehyde liberated 
and that remaining in the residue. 
Our bacteriological experiments were carried out with the purpose 
principally of determining the properties of formaldehyde gas as a 
surface disinfectant, it being taken for granted that formaldehyde 
possesses only slight penetrating power. 
In the following pages the work is given under three headings, 
namely — 
1. Experiments in a special room. 
2. Experiments in a large bottle with the formalin-permanganate 
method. 
3. Disinfection of sleeping cars with formaldehyde gas. 
EXPERIMENTS IN A SPECIAL ROOM. 
DESCRIPTION OF ROOM. 
The room into which the formaldehyde gas was liberated contained 
2,000 cubic feet of air space. The walls, floor, and ceiling were of 
ordinary tongue and groove construction, and in addition to this the 
room was lined throughout, except over the windows, with sheet zinc, 
closely nailed at the joints. There were two windows and two doors, 
all of which were made to fit closely. The windows were on opposite 
sides and the doors opened into adjoining rooms, so that the experi- 
ment room was freely exposed to the winds on two sides. While 
comparatively close, it was of course not air-tight. 
One wall was pierced b}^ three horizontal rows of zinc tubes about 
2 \ inches in diameter, one row being about a foot from the floor, one 
midway between the floor and the ceiling, and one about a foot from 
the ceiling. Each tube was provided with a sliding wooden frame 
carrying a small wire tray for the purpose of making the bacteriological 
