192 PROCEEDINGS OF THE AMERICAN ACADEMY 



excepting the traces, for which correction will be made subsequently. 

 If, however, the weight of lithium chloride present exceeds ten or 

 twenty milligrams, it is advisable at this point, though not absolutely 

 essential to the attainment of fairly correct results, to decant the 

 liquid from the residue, wash the latter a little with anhydrous amyl 

 alcohol, dissolve in a few drops of water, and repeat the separation by 

 boiling again in amyl alcohol. For washing, amyl alcohol previously 

 dehydrated by boiling is to be used, and the filtrates are to be meas- 

 ured apart from the washings. In filtering it is best to make use of 

 the perforated crucible and asbestos felt, and apply gentle pressure. 

 The crucible and residue are ready for the balance after drying for a 

 few minutes directly over a flame turned low. The weight of insolu- 

 ble chlorides actually obtained in this manner is to be corrected by the 

 addition of 0.00041 grm. for every 10 cm.^ of amyl alcohol in the 

 filtrate exclusive of washings if the insoluble salt is entirely sodium 

 chloride, 0.00051 grm. for every 10 cm.^ if potassium chloride con- 

 stitutes the residue, and if both sodium and potassium chloride are 

 present, 0,00092 grm. ; but, as in the experiments described, the entire 

 correction may in any case be kept within narrow limits, if due care 

 be siven to the reduction of the volume of residual alcohol before 

 filtration. The filtrate and washings are evaporated to dryness, 

 treated with sulphuric acid, the excess of the latter driven off, and the 

 residue ignited to fusion and weighed. From the weight thus found 

 the subtraction of 0.00050 grm. is to be made if sodium chloride 

 constitutes the precipitate, 0.00059 grm. if potassium chloride alone 

 is present in the residue, and 0.00109 if both of these chlorides are 

 present, for every 10 cm.^ of filtrate exclusive of washings. 



Amyl alcohol is not costly, the manipulations of the process are 

 , easy, and the only objectionable feature — the development of the 

 fumes of amyl alcohol — is one which is insignificant when good 

 ventilation is available. 



The process has been used for some months frequently and success- 

 fully, by others as well as myself, for the estimation of lithium in 

 waters and minerals. 



In this connection it seems best to include the record of certain 

 experiments looking to the separation of the chlorides of sodium and 

 potassium from the chlorides of magnesium and calcium. The be- 

 havior of magnesium chloride toward amyl alcohol is of interest, both 

 with reference to the problem of separating sodium and potassium 

 from lithium and magnesium when the latter are associated, and as 



