92 62. BASES AND ACIDS AVITH REAGENTS. 



glass tube that j^asses through the well-fitting rubber cork 

 in the mouth of the flask, and jiut a clamp, y, on the end 

 of the tube. Fasten this clamp oj)en and boil the water 

 in C until the air is completely expelled from the flask, 

 and, while steam is still escaj)ing from the end of the rnb- 

 ber tube, slip it over the glass tube ^ on the receiver, and 

 at the same moment open the stop-cock h ; the aqueous 

 vapor, from the water that continues to boil in the flask, 

 condenses at first in the neck of the receiver and washes 

 the milk of lime out of the upper part of it and out of 

 the glass tube ; if any milk of lime is carried into C in' 

 the operation that follows, the analysis is worthless. 



Xow, remove the lamp from C, and a current starts in 

 the opposite direction, which carries the nitric oxide into 

 C ; the rapidity of the flow can be regulated by compress- 

 ing the rubber tube between the fingers ; as soon as the 

 milk of lime in the receiver has reached the rim of the 

 rubber tube/, close the stop-cock Tc and conduct 20 or 30 

 c.c. of pure hydrogen into the receiver, oj^en the stop-cock 

 and allow this gas to flow into C ; repeat this two or three 

 times, thus carrying the last traces of nitric oxide from 

 B to 0. Now, close h again and also the clamp y near 

 this end of the tube, connect the rubber tube Avith a 

 small gasometer containing oxygen, open the cOck of the 

 gasometer and the clamp y again, and oxygen will pass 

 into C and convert the nitric oxide into nitric acid ; when 

 all the oxygen has passed into the flask that will, close 

 the gasometer cock, disconnect the rubber tube from it,- 

 and, after about 15 minutes, determine the nitric acid in 

 the liquid in C by means of the ^1^^ standard solution of 

 soda ; each cubic centimetre of the sodic solution, con- 

 taining ^Ijo of an equivalent of sodic oxide (Na.O), will 

 combine with '1^^ of an equivalent of nitric anhydride 

 N^Oj., expressed in milligrammes = 5.4 mgr. or 0.0054 grm. 



h. Nitric acid may be very conveniently estimated in 

 nitrates, as, for example, when it is desired to test the 



