DETERMINATION OF ALKALIES IN MINERALS. 215 



(b) Five hundred milligrammes of chloride of sodium treated 

 in the same way yielded one half of a milligramme to the liquid. 



(c) A mixture of chlorides of potassium, sodium, and lithium, 

 in which the latter constituted two per cent, of the mass, was 

 acted on by the ether and alcohol, filtered and evaporated to 

 dryness; the residue was equal to 2.53 per cent. The quantity 

 used was CI K and CI Na each 200 milligrammes, CI Li 0.8 

 milligramme. 



(d) A similar mixture containing 18.10 per cent, of chloride 

 of lithium furnished a residue of 17.65 per cent. 



(e) A similar mixture containing 67.20 per cent, of chloride 

 of lithium gave a residue of 68.40. 



44. By these results it may be seen that this method of sep- 

 arating lithia from the other alkalies may be perfectly relied 

 on. It only remains to detail the precautions to be taken in 

 order to insure accurate results. 



45. The solution of alcohol and ether must be made of abso- 

 lute alcohol mixed with its volume of pure ether. The chlorides 

 must be dried thoroughly at 212° or a little above; if they have 

 at any time been heated much higher, a drop or two of hydro- 

 chloric acid must be added to the chlorides, that are subsequently 

 dried at the temperature just mentioned. The desiccation is 

 best carried on in a small-sized capsule. To the dry mass a 

 small quantity of the mixture of alcohol and ether is added 

 and stirred with a small glass rod ; the chlorides soon disinte- 

 grate; the capsule and its contents are placed on a glass plate 

 and covered with a small bell-glass (a common tumbler answers 

 the purpose very well, especially if the edge be ground); this 

 is left to digest for twenty-four hours, and then thrown on a 

 filter and washed with the alcohol-ether solution; the chlorides 

 of sodium and potassium remain on the filter. These last can 

 be dissolved off the filter by means of water, and separated in 

 the ordinary way. 



46. The alcohol-ether solution of chloride of lithium is evap- 

 orated to dryness, converted into sulphate, and weighed. The 

 results thus obtained far exceed in accuracy those of any other 

 method for separating lithia. The indirect method, by ascer- 

 taining the quantity of sulphuric acid contained in the mixed 

 sulphates, is the next best, but like all indirect methods of an- 

 alysis should never be employed except when it is absolutely 

 necessary. 



