16 THE DETERMINATION OF LITHIUM. 



The follo^ving is a tabular statement of the results obtained: 



Separation of lithium from sodivm and potassium by pyridin. 



The weights of sodium and potassium sulphates were calculated 

 for the amyl-alcohol extractions, using the corrections obtained as 

 described later for the solubility of sodium and potassium chlorids in 

 this solvent. The sodium and potassium sulphates in the pyridin 

 extraction, however, were directly determined. Here the amount of 

 lithium cldorid was greater than that of the sodium and potassium 

 chlorids, though probably less than that of barium chlorid. The 

 insolubility of barium clilorid in pyridin makes the Kahlenberg 

 method especially useful for such checking of the mixed sulphates. 



Tlie unpleasant odor of pyridm and the difhculty of preparmg and 

 keeping it sufficiently free from water are objections to the use of 

 the method which are not quite so strong in the case of the amyl 

 alcohol. The chief objection to the use of the pyridin method in 

 water analysis is the fact that usualty very small quantities of lithium 

 clilorid are to be separated from large quantities of sodium and potas- 

 sium clilorids. 



To extract the lithium from the dried crj^stalline mixed chlorids is 

 much more difficult than is the extraction with amyl alcohol, the 

 advantage of the latter method lying in the fact that the extraction 

 is made from a solution of the chlorids; hence there is not the danger 

 of loss from occlusion. 



Lecco ^ suggested the recovery of the lithium from the filtrate 

 obtained in the regular course of anal3"sis after the precipitation of 

 the calcium and magnesium. He added sodium hydroxid, evapo- 

 rated to dryness, volatilized the ammonium salts and proceeded 

 according to Mayer's method. He gave results showing the recovery 

 of a trace, 0.0243 gram, and 0.0115 gram of lithium oxid from solu- 



J Zts. anal. Chem., 1910, J,9: 286-287. 



