AIR AND VENTILATION 



107 



building from that of fresh outside air. The peculiar smell of 

 animal-vitiated air was used by de Chaumont as a means of gauging 

 the degree of atmospheric impurity, and he constructed the table 

 which is here reproduced. While it is rather doubtful if the table 

 is very trustworthy when used in connection with animal houses, 

 it may be of some assistance. 



Percentage of CO 9 



in the air due to 

 respiratory impurity. 

 When the air smells practically 



as fresh as outside air . . 0.020 



When the air smells rather close . 0.041 



When it smells close . . . 0.067 



When it smells very close . . 0.091 



The percentage of CO 2 in the air can be approximately estimated 

 by the Angus Smith Method, or more accurately by the Lunge- 

 Zeckendorff or Pettenkoffer methods. 



The Angus Smith Method. If CO 2 is passed through lime water 

 it combines with the CaO forming calcium carbonate which, becom- 

 ing precipitated, gives a turbidity to the water; if the addition of 

 CO 2 is continued beyond the point needed for the test, the turbidity 

 vanishes owing to the formation of the bicarbonate of calcium as 

 is shown in the following equations : 



The amount of air required to be passed through a given quantity 

 of lime water before cloudiness appears will indicate the proportion 

 of CO 2 present. The method is as follows : 



Take a series of glass stoppered bottles, 20|, 10, 8, 6 and 4 

 ozs. in capacity, or in c.cs., 580, 300, 230, 185 and 125 c.c. capacity. 

 Into the above series of bottles put -| oz. of clear saturated liquor 

 calcis, or baryta water, and wash the air contents of each by shak- 

 ing, noting carefully which becomes turbid first, then interpret the 

 result from the following table : 



