20 
bearing organisms, providing that the infection is present on the sur- 
face. If the room is of peculiar construction, so as to impede the dif- 
fusion of the gas, or if the room is a dirty one, or if on account of any 
other condition rendering the germicidal action of the gas more diffi- 
cult, the time of exposure should be proportionately increased, or sup- 
planted by other methods. 
DIFFERENT METHODS OF EVOLVING FORMALDEHYDE GAS.« 
I. FORMALIN-PERMANGANATE METHOD. 
When formalin is poured upon c^stals of potassium permanga- 
nate, a vigorous reaction takes place, accompanied by strong ebulli- 
tion of the. liquid and sufficient heat to produce a large quantity of 
formaldehyde gas, water vapor, etc. The time required for the 
reaction to begin, or at least to become apparent, varies from a. few 
seconds to a minute or two, depending upon the temperature. 
The reaction is apparently over in a comparatively short time 
(about five minutes), and with proper proportion of substances the 
residue in the vessel is almost dry. Evans and Russell used the 
proportion of 100 c. c. of formalin to 37.5 grams- of permanganate, 
but we found that with this proportion considerable formalin 
remained in the residue, as was evidenced bv its wet condition and 
powerful odor of formaldehyde. After some experimenting we 
adopted the proportion of 100 c. c. of formalin to 50 grams of per- 
manganate, which gave a residue fairl} r free from liquid. 
The quantity used to charge the room of 2,000 cubic feet was in 
nearly all cases 600 c. c. of formalin (containing 35.66 per cent of 
formaldehyde by volume). The generator was a galvanized-iron 
pail 10 inches in diameter and 10 inches deep, holding 12 liters (3 
gallons). The pail was placed in the center of the room, the per- 
manganate dropped into it and the formalin quickly poured upon it. 
The ebullition was so vigorous that the frothy mass often reached 
nearly to the top of the pail. 
W T e did not investigate the exact nature of the chemical reaction 
that took place, as for our purposes we were only interested in the 
fact that an abundance of formaldehyde was given off in gaseous 
form. According to Evans and Russell, “analysis of the gas thrown 
out into a room by this reaction showed it to consist of formaldehyde, 
water vapor, carbon dioxide, and a very small amount of formic 
acid. In the generator were found a lower oxide of manganese, a 
little formaldehyde, carbon dioxide, potassium Irpdroxide, and, I 
think, a little potassium formate resulting from the neutralization 
a In the experiments which follow, the quantities of formalin employed for the evolution 
of formaldehyde gas have been in strict accordance with the U. S. Quarantine regulations. 
In the case of the formaldehyde generating lamp, the quantities of methyl alcohol used 
have been less than those prescribed by the regulations; about 10 per cent less in the 
experiments in Pullman cars and about 30 per cent less in the room experiments. 
