The residue, after being heated with boiling water, is filtered, and the clear liquor is mixed with phosphate of soda, and evaporated to dryness.

On adding water as there is an excess of phosphate of soda the resulting phosphate of soda and lithia, will be quite inso- luble, and may be removed.

This double phosphate consists of an atom of phosphoric acid, combined with three atoms of fixed base : it dissolves in 1,400 parts water, at 59, and 951 parts at 212 But soda, and lithia, being isomorphous, more, or less, of the base may be lithia : its constitution, therefore, is variable.

Hence, after being dissolved, its phosphoric acid is removed with nitrate of silver ; and the excess of nitrate, with hydro- chloric acid.

The soda and lithia are then changed to chlorides : the liquor containing them is evaporated to dryness : and the chloride of lithium (LCI) is separated from the chloride of sodium, by a mixture containing equal parts absolute alcohol and ether which dissolves the chloride of lithium, and but a trace of the chloride of sodium.