68 
Experiments I to XI, inclusive, Table 6, were done during warm 
weather (summer) , and in all but X and XI the proportions used were 
1 part by volume of formalin to 0.5 part by weight of permanganate, 
the same as was used in the experiments in Table 1 . With this propor- 
tion the total amount of formaldehyde found in the air of the bottle 
and in the residue was fairly constant, considering the conditions of the 
experiments. 
Evidently there is an advantage in using permanganate in pow- 
dered form, as is shown by comparing the results of IV, V, VI, VII, 
and VIII, with those of I, II, and III. No doubt the reason for this is 
that action takes place more quickly with production of a higher 
temperature, so that more formalin evaporates from the crucible and 
less remains with the residue. 
The results in experiments I, II, and III, with an average of 33 per 
cent, are lower than the results in Table 1, which refer to experiments 
in charging the room of 2,000 cubic feet. This would be expected 
considering the small quantities used, whereby the quantity of heat 
produced is not so large and the cooling of the generator is more rapid. 
In the experiments where powdered permanganate was used, the per- 
centage yield is higher and in line with the results in Table 1, 
In experiment IX, where only 0.5 c. c. of formalin was used, the 
result is low; but this is probably due to the fact that the quantity of 
formalin is too small to produce as vigorous an action as did the 
other cases. 
In experiment X the proportion of permanganate was increased, 
with the result that the amount of the formaldehyde sent out into the 
bottle was not affected much, but considerably less remained with the 
residue. 
In experiment XI the permanganate was decreased to the propor- 
tion used by Evans (Maine State board of health) in the report on this 
method. The result shows a considerable decrease in the formalde- 
hyde sent out into the bottle and large increase in the amount remain- 
ing in the residue. 
Experiments XII to XV inclusive were performed during cold 
weather (winter) , the results of which demonstrate that the percent- 
age of formaldehyde actually given off during cold weather does not 
differ very materially from that given off during warm weather. 
In these experiments any paraformaldehyde, whether given off as 
such or resulting from polymerization of the formaldehyde after it 
was given off, is included in the percentage of formaldehyde liberated, 
since paraformaldehyde enters into union with the cyanide in the 
same manner as does formaldehyde gas. 
The results of these experiments also show that the reduced yield of 
formaldehyde obtained in the room when working at a cold tempera- 
