398 Drushel and Brandegee — Hydrochloric Acid in the 



Art. XXV. — The Use of Hydrochloric Acid in the Esti- 

 mation of Certain Forms of Organic Nitrogen ; by W. A. 

 Drushel and M. M. Brandegee. 



(Contributions from the Kent Chemical Laboratory of Yale Univ. — cclxv.) 



Markownikoff,* while studying the preparation of pyrotar- 

 taric acid, observed that nitrogen is quantitatively removed 

 from cyanbutyric acid in the form of ammonium chloride by 

 the action of hydrochloric acid, suggesting that a method of 

 estimating nitrile nitrogen, based upon the action of hydro- 

 chloric acid, might be developed which would be fully as 

 simple as the well-known method of Carius for halogens. 



The purpose of this investigation was to determine the best 

 conditions for effecting the quantitative decomposition of cer- 

 tain forms of nitrogen compounds and determining rapidly the 

 nitrogen obtained in the form of ammonium chloride. To this 

 end members of several classes of nitrogen compounds were 

 selected for study, such as the nitriles, amides, imides, cya- 

 nogen-substituted esters, and amino-acids. In particular the 

 following substances were examined : acetonitrile, proprio- 

 nitrile, proprionamide. succinimide, cyan-acetic ester, ethyl 

 a-cyan-propionate, ethyl a-cyan-butyrate, normal dipropyl 

 a-cyan-acetic ester, and amino-acetic acid. It is well known 

 that when compounds of these types are heated with aqueous 

 mineral acids they are hydrolyzed to the corresponding organic 

 acids and the ammonium salts of the mineral acids used. By 

 using concentrated hydrochloric acid in excess at suitable 

 temperatures it was found that in these compounds the nitro- 

 gen could be fixed quantitatively and could be estimated 

 by titrating the ammonium chloride with standard silver 

 nitrate using potassium chromate as an indicator, after remov- 

 ing the excess of hydrochloric acid. The decomposition of 

 the substances studied, by means of aqueous hydrochloric acid, 

 is represented by the equations on the following page. 



In the cyanogen compounds which on hydrolysis yield malo- 

 nic or substituted malonic acids the decomposition resulted in 

 considerable pressure in the sealed tubes, indicating the further 

 decomposition of the dibasic acids with the formation of car- 

 bon dioxide and monobasic acids. 



The decomposition was effected by heating the compounds 

 in sealed tubes of thick-walled glass, about 25 cm in length and 

 in inside diameter not less than 15 mm . From one tenth to three 

 tenths of a gram of the substance was weighed out, using capil- 

 lary bulbs for weighing out and transferring liquid compounds. 

 The weighed material was placed in a combustion tube and 3 cmS 



* Markownikoff, Ann. der Chem. u. Pharm., clxxxii, 331. 



