266 Kreider and Breckenridge — Sej^aration and 



These results prove that the two elements when combined in 

 any proportion may be separated and identified with great 

 delicacy. 



Before applying this method, however, it is necessary to 

 remove certain interfering substances. While potassium may 

 be safely tested for in the presence of other bases and acids, 

 except ammonium, csesium and rubidium, and sulphuric acid* 

 the large number of elements whose chlorides are insoluble in 

 alcohol necessitates their removal before testing for sodium. 

 But among the common alkalies ammonium is the only one 

 whose presence is objectionable. Lithium does not affect either 

 the test for potassium or sodium, as was determined by an 

 experiment in which about 0*1 grm. of lithium chloride was 

 converted into the perchl orate by evaporating with an excess 

 of perchloric acid and treated with 10 cm^ of 97 per cent alco- 

 hol. A perfectly clear solution was obtained, which upon 

 saturation with gaseous hydrochloric acid and cooling, remained 

 clear. The removal of sulphuric acid is necessitated by the 

 insolubility of sodium sulphate in alcohol. 





Table III. 





Bases taken. 









Pb.Cu. Al.Fe.Zn, 



K2O 



Na^O 



Indication Indication 



. Ca . and Mg . as nitrates. 



taken. 



taken. 



for for 



grms. 



grms. 



grms. 



potassium. sodium. 



0-0500 of each 



0-0000 



0-0000 



faintest trace trace 



0-0500 " 



0-0017 



0-0012 



good good 



0-1000 " 



00000 



0-0.000 



faintest trace trace 



0-1000 " 



0-0000 



0-0005 



" '' good 



In the experiments made with potassium and sodium asso- 

 ciated with other acids and bases, the results of which are 

 recorded in Table III, the following treatment was adopted. 

 The several groups of bases were successively removed in the 

 ordinary way : Hydrogen sulphide in ammoniacal solution 

 removed the lead, mercury, copper and zinc. Barium and cal- 

 cium were removed by ammonium carbonate, the final filtrate 

 being evaporated and ignited to the complete volatilization of 

 ammonia. The residue was dissolved and treated with barium 

 hydrate for the removal of magnesium, and after filtering the 

 barium was again removed by ammonium carbonate and the 

 filtrate evaporated and ignited as before. This residue was 

 then treated with 10 cra^ of boiling water and after stirring was 

 filtered in order to remove the organic matter usually found at 

 this stage of the treatment. To the filtrate was added 0*1 to 

 0-5 cm^ of pure perchloric acid, about 1-Y sp. gr., according to 

 the amount of residue, and evaporated over the steam bath 

 until the white fumes of perchloric acid appeared. When the 

 quantity of sodium is large it is safer to evaporate several 

 times in order to secure a complete conversion to the per- 



* Loc. cit. 



