xii. a, 6 Brill and A gcaoili: Kjeldahl Method 265 



The results when sodium sulphate was used are in every case 

 low. Digesting the pyridine for a longer time is conducive to 

 more nearly theoretical yields. Where mercury is used, care 

 must be taken to precipitate it as the sulphide. A loss in nitrogen 

 is liable to arise from this source, because of the difficulty of 

 decomposing the ammonio-mercurial compound. 10 



SUMMARY 



The Kjeldahl method gives low results for nitrogen with pyri- 

 dine, piperidine, quinoline, isoquinoline, oxyquinoline, pyrrole, 

 and in some cases with nicotine. The authors believe this arises 

 from the formation of sulphonic acid derivatives and their resist- 

 ance to decomposition. ' 



The Gunning-Arnold method gives more reliable results with 

 pyridine when heated for a considerable period after the solution 

 has become clear. 



Sodium sulphate is not conducive to good yields and cannot 

 be substituted for potassium sulphate. 



10 Justin-Mueller, Ed., Bull. Sci. Pharm., Paris (1916), 23, 167. Nolte, 

 Otto, Zcitschr. f. anal. Chem. (1916), 55, 185. 



