262 Dr Turner on Lithion-Mica. 



advisable to describe the method of separating lithia from po- 

 tash which was adopted in all of them. 



To separate lithia from potash. — The mica, after being re- 

 duced to fine powder by friction in an agate mortar, was inti- 

 mately mixed with six times its weight of carbonate of baryta, 

 and then exposed for an hour and a half or two hours to the 

 full white heat of a Blacks furnace. The ignited mass was 

 dissolved in dilute muriatic acid, and evaporated to perfect 

 dryness. The soluble parts were taken up by a consider- 

 able quantity of hot water, pure ammonia was then added 

 to separate alumina, iron and manganese, and these preci- 

 pitates together with the silica were at once collected on a 

 filtre. To the filtered solution, while still hot, an excess of 

 carbonate of ammonia was added, so as to separate all the 

 baryta in the form of carbonate. The clear solution, thus 

 freed from baryta, was evaporated to perfect dryness, and the 

 dry salt ignited to expel muriate of ammonia. A fused mass 

 was always left, which deliquesced rapidly on cooling. It 

 was dissolved by water, mixed with a little solution of muriate 

 of platinum, and evaporated to perfect dryness. The dry 

 mass was now treated with alcohol of moderate strength, 

 which readily took up the muriate of lithia, and the excess of 

 platinum salt, leaving the muriate of platinum and potash un- 

 dissolved. A perfect separation of the two alkalies was thus 

 effected, and they could each be determined in the usual way. 

 It is necessary to convert the muriate of lithia into sulphate, 

 because the former is so deliquescent, that it attracts moisture 

 during the operation of weighing ; and, moreover, its compo- 

 sition is not so well known as that of the sulphate. The con- 

 version was of course easily effected, by adding a neutral sul- 

 phate of ammonia to the alcoholic solution of the muriate of 

 lithia, evaporating to dryness, and igniting. It was found 

 most convenient also to determine the potash by means of the 

 sulphate, since the addition of sulphate of ammonia to the 

 double salt of platinum and potash, facilitated the separation 

 of the platinum. 



I might here mention, that before adding the salt of platinum, 

 the absence of lime was proved by oxalate of ammonia ; and 

 bv way of precaution, a little hydrosulphuret of ammonia was 



