112 
A small quantity of formaldehyde A efficient for surface disinfection, 
provided the temperature and humidity are high. A large quantity 
assists penetration, as also do high temperature and humidity: but 
even then the penetrating power of formaldehyde is so Iimi:ed that it 
shoni i not be empi : yed for disinfection purposes requiring any marked 
degree of penetration. 
Depending upon the conditions as stated, the quantity of formalin 
may vary from 200 to 500 c. c. per 1,000 cubic feet of air space. As 
sleeping cars have many ventilators etc. the leakage >f formalde- 
hyde gas from them is quite rapid, so that it is necessary to use a rela- 
tively larger quantity of formalin than is usually required in room 
disinfection. 
The length of exposure depends upon circumstances, mo hours 
tinder favorable conditions ~er- usually sufficient in ur experiments. 
In the car experiments very little formaldehyde gas mas found the 
car at the end of this time. Consequently very little would ham been 
gamed by a longer exposure . In a well -closed r : >m a longer ext osure 
would doubtless te of advantage, although our conclusions are that in 
surface -disinfection with formaldehyde the organisms are mostly 
keied within, the hrst hour of exposure A they are destroyed at all 
F :r simplicity and rapidity the formalin-perm auigan a te meth: i is 
far superior to any if the ither methods tried. It liberates the for- 
maldehyde ras almost instantaneously and in almcst as large quanti- 
ties as the retort and autoclave methods. 
Better disinfection is aeconit Ashed by having a comparatively 
large quantity of formaldehyde gas and a short exposure than a small 
quantity and long ext osure. The form a lin-perm amgana :e method is 
more applicable than any of the other methods for disinfecting an 
inclosure which is not comparatively tight. With this method a 
larger percentage :f exposures if B fi:--vi.im< were killed than with 
any of the other methods. 
The formalin and permanganate should oe used in about the pro- 
portion of 1 e. c. of the former to 0.5 gram of the latter. Xo obvious 
advantage is gained by adding water to the formalin before mixing 
with the permanganate. 
The retort, autoclave, and generating damp are efficient methods 
under favirable conditions, but they require more :>r less complicated 
apparatus as well as considerable time to evolve the f irmaliehyue 
^as. 
The sheet -spraying meth A is rather simple and economical and is 
especially applicable for disinfection purposes requiring Ling exposure. 
The formalin-aluminum sulphate-lime method is nc t s : simple and 
efficient as some of the other methods but under favorable conditions 
it may be used with vezw good results. 
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