Brill and Agcaoili: Kjeldahl Method 



263 



the nitrogen content of various classes of nitrocarbon com- 

 pounds by means of the Kjeldahl method to determine what type 

 of compounds yields only a part of its nitrogen by this process. 



A sample of approximately 0.2 gram of the pure compound 

 was heated with concentrated sulphuric acid (20 to 30 cubic centi- 

 meters), potassium sulphate (5 grams), and copper sulphate 

 (0.5 gram) for two and one-half to four hours or for one-half 

 hour after the solution had become clear, at the boiling point 

 of the solution. The results of this examination are given in 

 Table I. 



Benzylcyanide and phenylcyanate were included in this inves- 

 tigation, as it was at first thought that the low yields of nitrogen 

 obtained might be due to the breaking down of the molecule with 

 the liberation of hydrocyanic acid. However, it seems more 

 plausible to attribute the low yields of nitrogen from pyrrole, 

 pyridine, piperidine, quinoline, isoquinoline, and oxyquinoline to 

 the formation of sulphonic acid derivatives and their subsequent 

 resistance to decomposition by the sulphuric acid. 



The use of vanadium oxide • has been recommended as a cataly- 

 zer in the Kjeldahl method. The method was employed by us 

 in the determination of the nitrogen of piperidine without satis- 

 factory results. 



Table II. — Nitrogen determination of piperidine by use of the modified 

 Kjeldahl method.* 



No. of analysis. 



Compound. 



Nitrogen. 



Total ni- 

 trogen 

 liberated. 



Theory. 



Found. 







Per cent. 

 16.47 

 16.47 

 16.47 



Per cent. 

 12.23 

 12.15 

 12.96 



Per cent. 

 74.26 

 73.77 

 78.69 





do 





do 







* No 1 was prepared in the manner described by Wunder and Lascar ; No. 2 had 0.5 

 gram of bismuth oxide substituted for the vanadium oxide ; while No. 3 had the same amount 

 cf antimony oxide used as a substitute. 



The results obtained in the experiment using vanadium oxide 

 are no better than where bismuth or antimony oxide was used. 



Dakin and Dudley 7 state that piperidine by prolonged heating 

 with sulphuric acid in the presence of potassium sulphate and 

 copper sulphate gives up all its nitrogen, but that pyridine gives 

 less satisfactory results. In the determination of the nitrogen 



"Wunder, W., and Lascar, O., Journ. Phurm. et Chim. (1914), 19, 329. 

 T Dakin, H. D., and Dudley, H. W., Journ. Biol. Chem. (1914), 17, 275. 



