6o 



The Estimation of Nitrogen 



[89 



After placing the tube in the furnace, turn on and light the two 

 taps nearest the open end. Gas will be seen to bubble through 

 the bulbs. As soon as this ceases turn on the next tap. The 

 bubbles will start again. When they have ceased, or nearly so, 

 turn on another. Continue turning on the taps in this way 

 until the whole tube is red hot. 



The last few taps will, of course, only heat the mixture of 

 soda lime and sugar which was introduced first of all. This 

 gives off various gases which expel the last traces of ammonia 

 from the tube. 



When all bubbling has ceased, hold the tube firmly with a 

 pair of glass pliers, and carefully draw the bulbs out. (The glass 



Fig. 27. 



tube will come away, leaving cork adhering to the iron tube.) 

 Empty the acid into a large beaker. Wash out the bulbs 

 twice with distilled water, pouring the washings into the beaker 

 which already contains the acid. Add a few drops of methyl 

 orange solution, and titrate with the quinquinormal alkali, 

 using burette e, fig. 25. 



89. Calculation. — Divide the number of c.c. of potash 

 run into the acid by 2*5, which gives the number of c.c. of acid 

 which have been neutralised by it. Subtract this from 20, and 

 you have the number of c.c. of acid which have been neutralised 

 by ammonia. 



