QUANTITATIVE SEPARATION OF LITHIUM' 15 



ion of the authors that if the directions are closely followed no such 

 error amounting to 0.029 gram is possible except from gross careless- 

 ness. Ranzoli remarked that all the gravimetric results are liable to 

 be high on account of incomplete separation of the other alkalis from 

 the lithium precipitate, or low because of the solubiUty of the lithium 

 salt when the washing is complete enough to remove the others. 



Kahlenberg and Krauskopf^ devised a separation of lithium by 

 pyridin. They found the clilorids of sodium and potassium to be 

 practically insoluble in pyridin, while Uthium chlorid is quite easily 

 soluble. To make the separation, the mixed clilorids were evaporated 

 to complete dryness with a little hydrocliloric acid and the dry mass 

 extracted once or twice with boiling pyridin which was filtered off. 

 The pyridin was evaporated off from the insoluble residue which 

 was dissolved in a little water, evaporated to dryness from hydro- 

 cUoric acid and the extraction repeated. The pyridin solution was 

 evaporated to dryness, treated with water and sulphuric acid and the 

 htliium weighed as sulphate after evaporation and gentle ignition. 

 The great advantage of the method is the freedom from corrections 

 due to solubility of the other alkalis, which must be allowed for in the 

 method of Gooch and probably should be allowed for in the use of the 

 ether-alcohol extraction as usually carried out. 



Kahlenberg and Krauskopf also mention the advantage of pyridin 

 over amyl alcohol in the extraction of large quantities of Uthium from 

 moderate amounts of sodium salts. The smallest amount of lithium 

 chlorid extracted by them was 0.090 gram from 0.83 gram of sodium 

 chlorid and in another experiment 0.0907 gram from 0.1933 gram of 

 potassium chlorid, 0.2913 gram of sodium chlorid, and 0.1021 gram of 

 barium chlorid. Few natural waters have more than 1 per cent of 

 lithium chlorid in the alkaline chlorids, so that to obtain for extrac- 

 tion a residue of mixed chlorids of which about 10 per cent would be 

 lithium clilorid, it would be necessary to concentrate the lithium by 

 alcohol or by hydrochloric acid extraction from the main bulk of the 

 chlorids. 



The pyridin extraction has been used by the authors on some mixed 

 sulphates obtained by the Gooch method which w^ere thought to con- 

 tain too much sodium and potassium. The sulphate was removed by 

 adding to the solution of the sulphates a sHght excess of barium 

 chlorid and filtering. The filtrate was evaporated to dryness and 

 extracted with pyridin. As a check the material insoluble in pyridin 

 was converted into sulphate and weighed, the sulphate taken up with 

 water, filtered, and the filter paper with the barium sulphate burned 

 in the dish and weighed with the dish to give the weight of the sodium 

 and potassium sulphates. 



' J. Amer. Chem. Soc, 1908, 30: U04. 



