7» 



The Estimation of Nitrogen 



[109 



the table j find the figure denoting the number of millimetres 

 of pressure in the first column, and glance along this line until 

 you come to the column which is headed by the number of 

 degrees Centigrade which you have read off on the thermometer. 

 Multiply the number of c.c. of gas obtained by the factor here 

 found. The product will be the volume at o° C. and 760 mm. 

 For instance, supposing we found our volume to be 89.2 c.c. 

 at 1 7 and 772 mm., we find the factor for this temperature 

 and pressure in the table to be "9562. We calculate the volume 

 at o° C. and 760 mm. thus : 



89-2 x '9562 = 85-29 



and multiplying this by "000627 we get the weight of N ,in 

 our substance — i.e., '05348 gram. 



109. The second apparatus is shown in fig. 32. The 

 operation is carried on in the flask a, which is of 6-oz. capacity 



Fig. 32. 



and is fitted with an india-rubber stopper in which two holes 

 have been bored. Through one passes the tap funnel b, 

 through the other an evolution tube, c o, which is cut at d and 

 joined with a piece of india-rubber, which can be closed at will 



