AGRICULTURAL EXPERIMENT STATION. 205 



summer of 1887 but not published heretofore, has been used. 

 Practically the same method has been suggested and tested by other 

 chemists since that time with good results. 



The method is as follows : — 1 gram finely powdered substance is 

 introduced into a dry digestion flask, 30 c. c. concentrated sulphuric 

 acid containing IJ grams phenol added, shaken until thoroughly 

 mixed and allowed to stand ten minutes at ordinarj^ temperature. 

 One-half to two grams powdered zinc is then added, the flask placed 

 over a very low flame and heated cautiously for 15 minutes, when 

 about 7 grams mercury is added and the flame increased sufHcientlj 

 to boil the acid. The remainder of the process does not diff'er from 

 the regular Kjeldahl method. 



This method has proved very reliable when properly worked. 

 The only precautions necessaiy to secure good results are, to mis 

 the substance with the acid and phenol, thoroughly, before adding 

 zinc or heating, and to have the flame verj^ low on beginning to 

 heat. The following table shows the results obtained with pure 

 nitrates and fertilizers containing nitrates. Samples I to V inclusive 

 were prepared from fertilizers containing only organic nitrogen and 

 ammonium salts. The nitrogen was carefully determined in them 

 and a weighed amount of pure nitrate added to each. A few de- 

 terminations were made with benzoic acid substituted for phenol — a 

 modification of Asboth's method. 



