AGRICULTURAL, ANALYSIS 



Fig. 38. The lower part of the eudiometer is closed with a rub- 

 ber stopper carrying a glass tube which ends in the pan / as 

 shown at e. The eudiometer is filled to the stop-cock with a 

 solution of potassium ferrocyanid of about 14 per cent, strength. 

 The dish / is also filled up to the height indicated in the figure 

 with the same solution. The solution of nitrite is used in such 



Figure 38. Schaeffer's Nitrous Acid Method. 



quantities that the nitric oxid evolved will occupy a space of about 

 20 cubic centimeters. The whole eudiometer should contain 

 about 57 cubic centimeters. The nitrite solution is added to the 

 eudiometer by means of a funnel a. The vessel containing it is 

 washed out with a little water and with acetic acid and finally 

 with a few cubic centimeters of strong potassium ferrocyanid so- 

 lution. The last fluid flows through the solution of nitrite and 

 acetic acid and thus mixes it with the solution already in the 

 eudiometer. The liquids reacting on each other float together on 

 the strong ferrocyanid solution and each one of them is at once 

 pressed downward by the gases which are evolved. When the 

 evolution of gas becomes slower the apparatus should be shaken 



