D. TJ. Hill — Separation of Potassium and Sodium. 75 



Art. VII. — The Separation of Potassium and Sodium by 

 the Use of Aniline Perchlorate, and the Subsequent Esti- 

 mation of the Sodium ; by D. IT. Hill. 



[Contributions from the Kent Chemical Laboratory of Yale Univ. — cclxviii.] 



The chief purpose of the experiments to be described was 

 to determine the availability, as a method for estimating sodium 

 quantitatively, of the precipitation of sodium chloride from 

 solution in alcohol by means of gaseous hydrogen chloride, 

 after the removal of potassium as perchlorate. Kreider and 

 Breckenridge* have determined the delicacy of the qualitative 

 test for sodium made in this way, and have found that "even 

 in 40 orr: ' O0002 grm. of sodium oxide can be seen distinctly ; 

 from which fact," they conclude, "it is evident that this 

 method can be applied to the quantitative determination of 

 sodium." 



The possibility of substituting aniline perchlorate for per- 

 chloric acid as precipitant of the potassium has, also, been 

 tested in the present investigation. Aniline perchlorate forms 

 crystals of definite composition, without water of crystalliza- 

 tion, so that the amount to be used can be readily determined 

 by weighing. A greater advantage which it was thought the 

 use of the aniline salt would have over the acid, viz., that it 

 could be more easily prepared, proved to be illusory. Aniline 

 expels the ammonia from ammonium perchlorate when the 

 two substances are boiled together, but the reaction is slow and 

 during the boiling the aniline develops a dark color. No con- 

 venient way of getting rid of this color could be found. Other 

 methods for preparing aniline perchlorate, starting with the 

 ammonium salt, suggest themselves, as, for instance, the con- 

 version of ammonium perchlorate into barium percholate by 

 boiling with barium hydroxide, and then into aniline perchlo- 

 rate by dissolving in dilute alcohol, adding aniline, precipitat- 

 ing the barium as chloride by hydrochloric gas and ether, and 

 evaporating off the excess of hydrochloric acid ; or by mixing 

 exactly equivalent amounts of barium perchlorate and aniline 

 sulphate. f But all of these methods are more laborious than 

 the preparation of perchloric acid by Willard's^: method, i. e., 

 the oxidation of ammonium perchlorate to perchloric acid by 

 dilute aqua regia. Indeed, the easiest way to prepare the ani- 

 line perchlorate is to make the acid first by this very simple 

 method, and then to add aniline to a, water solution of the acid 

 until some of the oil remains after shaking, and boil vigor- 



* This Journal (4), ii, 263-8, 1896. 



t Spallino, Ann. Chim. applicata, i, 435; Chem. Abs. viii, 2701. 1914. 



jjour. Am. Chem. Soc, xxxiv, 1480-5, 1912. 



