398 



AGRICULTURAL ANALYSIS 



by dissolving nails or other small pieces of iron in hot hydro- 

 chloric acid and it is kept in glass stoppered flasks, of about 50 

 cubic centimeters capacity, entirely filled. The content of one 

 flask is enough for about 12 determinations and by using the 

 whole content of a flask as soon as possible after opening, any 

 danger of oxidation, which would take place in a large flask 

 frequently opened, is avoided. 



The contents of the flask are boiled until all the air is driven 

 off. The delivery tube is then placed under the measuring 

 tube, which is filled with 40 per cent, potash-lye. The measur- 

 ing tube is previously almost filled with potash-lye and then a 



Fig. 21. Schloesing- Wagner Apparatus. 



few drops of water added and the tube covered with a piece of 

 filter paper. By a careful and quick inversion the measuring 

 tube can be brought into the vessel receiving it without any dan- 

 ger of air entering. The boiling is continued for some time and 

 when no more air escapes, the end of the delivery tube is brought 

 into another freshly filled measuring tube and the estimation is 

 commenced. 



Ten cubic centimeters of a normal saltpeter solution, contain- 

 ing two and a half grams of pure sodium nitrate in 100 cubic 

 centimeters are placed in the funnel and, with continued boiling, 

 allowed to pass, drop by drop, into the flask. When almost all 

 has run out the funnel is washed three times with 10 cubic cen- 



