ON THE CARBONIC ACID, ORGANIC MATTER, ETC., IN AIR. 
87 
matter in air, whereas a burning oil lamp has a very marked effect in this respect (see 
Carnelley and Mackie, loc. cit.). 
3. Respiration .— Carnelley and Mackie {loc. cit.) have also shown that the 
quantity of organic matter in the air of a room becomes greater as the period of 
vitiation by respiration increases. In this connexion we have made a set of experiments 
with the object of determining the amount of organic matter in undiluted expired breath. 
For this purpose the observer inspired the air of the room through his nose, and 
expired through the mouth into a closed bottle of about 3^ litres capacity, and provided 
with a small outlet tube for the escape of the excess of expired air. This bottle was 
maintained at a temperature of about 45° C. by immersion in warm water, in order to 
prevent condensation of moisture from the breath. When the bottle was full of 
expired air, for which 50 expirations were considered sufficient, the temperature of the 
enclosed air was observed, the inlet and outlet tubes closed, and the bottle removed 
from the bath and allowed to cool down to the temperature of the room, when the 
inlet tube was opened and air allowed to enter to fill the partial vacuum. The 
temperature of the enclosed air was again observed, and the amount of organic matter 
determined in the usual way. A determination of the organic matter in the air of 
the room was likewise made at the same time. The proportion of expired and 
unrespired air of the room in the bottle could be found by calculation. Then, by 
deducting from the total organic matter that present in the known proportion of 
unrespired air, the difference gave the amount of organic matter in undiluted breath. 
Care was taken to breathe as nearly as possible in a natural manner. The results 
obtained were as follows :— 
Observer A. 
Observer B. 
Total in 
In air 
Excess in 
Total in 
In air 
Excess in 
expired air. 
of room. 
expired air. 
expired air. 
of room. 
expired air. 
3-3 
T6 
1-7 
6'5 
3-0 
3-5 
12-4 
3-2 
9-2 
12-2 
i-6 
10-6 
5-8 
1-6 
4-2 
133 
4-7 
8-6 
11-8 
2-2 
9-6 
13-1 
T9 
11-2 
15-6 
2-0 
13-6 
104 
2-3 
7-8 
Average per litre 
7'6 
Average per litre 
8-3 
The above determinations were mostly made on different days. According to these 
experiments the amount of oxidisable organic matter in breath is by no means 
constant, but varies from time to time, nor is the quantity so great as one might have 
expected. It is possible, however, that the organic matter in freshly expired breath 
is not in a condition to readily reduce permanganate, but after exposure for some time 
in the air it may undergo such a change as will render it more readily oxidisable. 
