62 
EXPERIMENT NO. 37— Continued. 
[4- means growth; — no growth.] 
* For rooms of this size the U. S. Quarantine regulations require 1440 c. c. of methyl alcohol. 
With this method, under proper conditions of temperature and 
humidity, most of the nonspore-bearing organisms were killed within 
a reasonable time. The time, however, is longer than with the pre- 
vious methods. Spores usually escaped destruction or were killed 
only after a relatively long time. 
As has been stated, the organisms were usually exposed and the 
time of exposure counted from the time of starting the lamp. This 
was not the case with the retort and autoclave methods, which 
required approximately 1 hour for the former and 25 minutes for the 
latter to vaporize the formalin. Therefore, in making a comparison 
of the time required for germicidal efficiency in these three methods 
the time at which the exposures were made must be borne in mind. 
With the lamp the organisms were, of course, subjected to the 
action of the formaldehyde as it was given ’off and probably many of 
them were destroyed before the process of liberation was complete. 
This fact also is to be considered in comparing the time actually 
required to kill the organisms in the three methods. 
The lamp is the only method that raises the temperature to any 
appreciable extent. The humidity is also increased considerably, and 
as it comes principally from evaporation of the water in the lamp, it 
is very probable that it is more like the natural humidity of the atmos- 
phere, and consequently is more potent in formaldehyde disinfection 
than is the moisture given off by the other methods. 
As lias already been stated, the temperature and humidity are of 
paramount importance in disinfecting with formaldehyde. On the 
other hand, its emplo}mient has the objections that have been men- 
tioned in case of the retort and autoclave, namely, that special appa- 
ratus is required and time is consumed in evolving the formaldehyde. 
An important feature of this lamp generator is that there is no poly- 
merization of formaldehyde into paraform following its use. 
VII. FORMALIN-ALUMINUM SULPHATE LIME METHOD. 
This method of liberating formaldehyde gas from formalin was first 
described by Walker, 0 of the department of health, Brooklyn, N. Y. 
a Walker, Henry G. : On a new method of generating formaldehyde gas for fumigating 
purposes. Journ. Am. Chem. Soc., vol. 24, No. 3, March, 1905. 
