MODIFICATION OF WARINGTON 



399 



timeters of 10 per cent, hydrochloric acid and this is allowed to 

 pass, drop by drop, into the flask. When no more nitric oxid is 

 evolved the measuring tube is transferred to a large jar filled 

 with distilled water. 



The solution of the substance to be examined should be used 

 in such quantity as will give about the same quantity of gas 

 as is furnished by the 10 cubic centimeters test nitrate solution 

 before described ; viz., about 70 cubic centimeters. Eight 

 or 10 determinations can be made, one following the other, and 

 finally another determination with normal sodium nitrate 

 solution should be made as a check. At the end of the opera- 



Fig. 22. Warington's Apparatus for Nitric Acid. 



tion of all the measuring tubes are in the large jar filled wtih 

 distilled water. The temperature of the surrounding water will 

 soon be imparted to the contents of each tube and the volume of 

 nitric oxid is read by bringing the level within and without the 

 measuring-tube to the same point. The percentages are calcu- 

 lated for the given temperature and barometer pressure in the 

 usual way ; or to avoid computation, the volume can be com- 

 pared directly with the volume furnished by the normal nitrate 

 solution, which is a much simpler method. 



350. Modification of Warington. The method of procedure 

 and description of apparatus used, as employed by Warington, 

 are as follows : 



The vessel in which the reaction takes place is a small tubu- 

 lated receiver, A (Fig. 22), about four centimeters in diame- 



