48 



F. T. SHUTT AND A. McGILL ON THE QUALITY OF AIR AT OTTAWA. 



(Blyth, Dictionary of Hygiene and Public Health, Griffin & Co., 1876). In parks and open 

 places in London the same investigator found 3-43 volumes per 10,000 (Fox, opus 

 cit. page 230). 



The following table gives our analytical data. 



Cakbonic Acid Estimations by Pettenkofer's Process. 



* Deduct 95 mm. tor residual pressure in aspirator. 



It will be seen that the quantity varied from 3-0682 volumes per 10,000 on 11th .June, 

 to 3-7177 per 10,000 on 13th June. It is to be remarked, however, that in the first estima- 

 tion a simrle Pettenkofer tulie was used, and it is not improbable that the absorption of 

 carbonic acid was incomplete in this instance. This is the more likely since the other deter- 

 minations are closely concordant and are all effected with two Pettenkofer tubes. The 

 check bulbs showed that the absorption was practically complete with the latter arrange- 

 ment of Pettenkofer tubes. 



The mean amount of carbonic acid gas (omitting the first estimation) is 3-5918 volumes 

 per 10,000 volumes of air on Parliament Hill. 



"We employed for the determination of the carbonic acid gas a solution of barium hydrate 

 of known strength (approximately 1/20 normal). The absorption was eftected, as already 

 mentioned, in two Pettenkofer tubes, each about one metre long. The air was aspirated 

 through these at the rate of about 12 litres per hour, and about 50 litres, were as a rule, drawn 

 through in each experiment. A set of Liebig bulbs containing barium hydrate was used as 

 a check to ascertain if there were complete absorption of carbonic acid in the Pettenkofer 

 tubes. 



