412 



AGRICULTURAL ANALYSIS 



Meanwhile the ebullition in the flask is continued, and the air 

 bubbles rising in the schiff apparatus are removed, from time to 

 time, by carefully opening h and raising g. When bubbles no 

 longer come over, the cock at e is closed and at b opened, and 

 the steam issuing at a is conducted through a mixture of ferrous 

 chlorid and strong hydrochloric acid to free it, as far as possible, 

 from air. When the contents of the flask have been evaporated 



Fig. 27. Schmidt's Apparatus. 



to about five cubic centimeters, b is closed and the lamp at once 

 removed. 



By carefully opening b about 10 cubic centimeters of a mix- 

 ture of ferrous chlorid and hydrochloric acid are allowed to enter 

 the flask, when b is closed and the flask slowly heated until the 

 positive pressure is restored. The pinch-cock e is then opened 

 and the contents of the flask evaporated nearly to dryness. The 

 cock e is again closed and the flame removed. Another quan- 

 tity (15 cubic centimeters) of ferrous chlorid and hydrochloric 

 acid solution is sucked into the flask and the process of distilla- 

 tion repeated, whereby the whole of the nitric oxid is collected 



