44 
EXPERIMENT NO. 21. 
Retort without pressure. 
Formalin, 600 c. c.; glycerin, 6 c. c. 
Capacity of room, 2,000 cubic feet. 
Quantity of formaldehyde used per cubic foot, 0.107 gram. 
Time required to exhaust material in retort, 1 hour. 
Quantity of formaldehyde found per cubic foot, 0.04935 gram. 
(Determination made by drawing air from room, beginning 21 minutes after exhausting retort 
and consuming 1 hour 10 minutes in the drawing.) 
Yield of formaldehyde, 46.12 per cent. 
Weather: Light westerly wind; cloudy. 
Tempera- 
ture. 
Relative 
humidity. 
Absolute 
humidity 
(grams per 
cubic foot) . 
Before beginning to introduce the gas 
O J? 
76 
Per cent. 
82 
7.91 
After 1 hour 
77 
89 
8.87 
After 2 hours 
77 
89 
8. 87 
See Note, experiment No. 18. 
[+ means growth; — no growth]. 
For surface disinfection better results could not be desired than 
were obtained in the above experiments. The temperature and hu- 
midity being comparatively high, the nonspore - bearing organisms 
were killed within five to ten minutes and the spores of B. subtilis 
within one hour, the time varying slightly in the different experi- 
ments. 
Although the humidity in experiment No. 19 was only 60 per cent 
before starting, the results are about as good as in those in which the 
humidity was considerably higher. 
In the following experiment (No. 21 a ) which was done after the 
room in experiment No. 21 had been left closed 72 hours (3 days), 
only 5.95 per cent of formaldehyde was found. Still B. pyocyaneus 
and B. coli communis exposed on filter paper were killed within 1 
hour and B. dysenterisc within 30 minutes. This shows, as has been 
previously mentioned, what a small percentage of formaldehyde will 
kill nonspore-bearing organisms when we have proper temperature 
and humidity. The spores of B. subtilis were not killed within 2 
hours. 
