ORDINARY MEETINGS. XXlll 
measured quantity of air, the proportion of carbon dioxid in the air is 
easily calculated. Carbon dioxid is a constituent of all air, but it has 
been shown that in re-breathed air it increases in direct proportion to 
the other, more poisonous, but less easily detected, impurities. We 
shall therefore make no error if we use the amount of carbon dioxid as 
an indicator of the amount of the organic poisons. 
The apparatus is so arranged as to admit into a glass cylinder which 
‘contains a measured amount of the standard solution, the air to be tested. 
When enough has been admitted to neutralize the solution, the propor- 
tion of carbon dioxid may be read off from a scale etched on the glass. 
It should be stated that as checks upon the experiments, samples of 
air were tested by other methods, the results agreeing very closely with 
those obtained by the Wolpert method. This is not as exact as syste- 
matic chemical analysis, but it is sufficiently so for the purpose. 
The instrument is graduated for 0°C and 760mm. of mercury pressure. 
As the air tested was always at a temperature of from 15°C to 20°C, and 
as the average pressure at Truro is 76lmm., there should be about 77/ 
added to the actual observations to correct them for temperature and 
pressure. I give below a table showing a set of observations which 
were made in the Chemical Laboratory at the Provincial Normal School. 
They are corrected for temperature and pressure, and the conditions in 
the room at the time of the various tests are given as accurately as 
possible. 
