164 BACTERIOLOGY. 
power of the gas depends not only upon its concentra- 
tion, but also upon the temperature and the condition 
of the objects to be sterilized. As with other gaseous 
disinfectants—viz., sul phur dioxide and chlorine—it has _ 
been found that the action is more rapid and complete 
at higher temperatures—i. ¢., at 35° to 45° C. (95° to 
120° F.)—and when the test objects are moist than at 
lower temperatures and when the objects are dry. Still 
it has been repeatedly demonstrated by actual experi- 
ment in rooms that it is possible to disinfect the surface 
of apartments and articles contained in them, under the 
conditions of temperature and moisture ordinarily 
existing in rooms, by an exposure of a few hours to 
a saturated atmosphere of formaldehyde gas. 
Stahl’ has shown that bandages and iodoform gauze 
can be kept well sterilized by placing in the jars con- 
taining them pieces of ‘‘ formolith,’’ a preparation of 
paraformaldehyde in tablet form containing 50 per 
cent. of formaldehyde. The same experimenter has 
also succeeded in making carpets and articles of cloth- 
ing germ-free by spraying them with 0.5 to 2 per cent. 
solution of formaldehyde for fifteen to twenty minutes 
without the color of the fabrics being in any way 
affected. The investigations of Trillat, Aronson, Pot- 
tevin, and others have shown that a concentration of 
zob75 Of the aqueous solution (40 per cent.), equal to 
zsbo0 Of pure formaldehyde, was safe and sufficiently 
powerful to retard bacterial growth. 
A 2 per cent. watery solution of formalin destroys 
the vegetative forms of bacteria within five minutes, 
In our experiments formalin has upon the vegetative 
1 Pharmaceutische Zeitung, No. 22, 1893. 
