43 
EXPERIMENT NO. 22 — Continued. 
[+ means growth; — no growth]. 
Organism. 
How exposed. 
Time of exposure in minutes, 
and results. 
10 
20 
30 
45 
60 
120 
180 
B. typhosus 
Filter paper 
+ 
+ 
+ 



B. coli communis 
do 
+ 
4- 
+ 
+ 
— 
— 
— 
B. subtilis 
do 
+ 
+ 
+ 
+ 
+ 
- 1 - 
+ 
B. coli communis 
Wilson method 
+ 
+ 
+ 
+ 
+ 
+ 
— 
B. subtilis 
do 
+ 
+ 
+ 
+ 
+ 
What has been said in regard to temperature, humidity, and per- 
centage of formaldehyde with the formalin-permanganate method 
practically applies to this method also. This method might be em- 
ployed when the temperature is a few degrees lower than is permissible 
with the formalin-permanganate method; but the difference is not 
sufficient to be of much practical importance. Apparently poly- 
merization does not take place quite so markedly, but about the 
same comparative reductions in the percentage of formaldehyde 
obtained are observed with the two methods when the temperature is low. 
The time required to destroy microorganic life is about the same in 
the two methods. The principal objections to the retort method are 
that special apparatus is required and considerable time is con- 
sumed in vaporizing the formalin. 
IV. THE AUTOCLAVE UNDER PRESSURES 
Six hundred c. c. of formalin, 60 c. c. of glycerin, 120 gm. of cal- 
cium chlorid, and water sufficient to make a volume of 1,000 c. c. con- 
stituted the charge for each experiment. The pressure was raised to 
between 50 and 60 pounds, when the cock was opened and injection 
continued till the pressure had fallen to about 40 pounds. Then the 
pressure was raised and vapor again injected. 
This process was repeated until the pressure arose very slowly and 
vapor ceased to escape from the nozzle of the autoclave, which was 
inserted through a suitable hole in the door. After each experiment 
there was very little liquid left in the autoclave. 
The time required to vaporize the quantity of formalin, etc., used 
varied from 22 to 28 minutes in the different experiments, depending 
upon the temperature of the atmosphere. 
Chemical determinations . — The method of procedure has been de- 
described. 
The results are shown in the following table : 
a The one used is the Kinyoun-Francis autoclave, manufactured by the Kensington 
Engine Works (Limited), Philadelphia, Pa. 
