138 /. W. Mallet on the Separation of Lithia and Magnesia. 



ing on the filter most thoroughly washed. This insoluble resi- 

 due consisted mainly of magnesia and the red-brown oxychlorid 

 of mercury (HgCl, 3HgO?), mixed with some free oxyd of mer- 

 ourv. It was cautiously ignited, the filter burntj and the re- 

 maming magnesia weighed. 



(2.) -4890 grm. of MgO was mixed with about '4000 grm. of 

 LiC], and treated in the same way as the above. 



The results of these two experiments were as follows : 



Magnesia. 



Actually used. Found. 



(1.) - - - -3463 -2029 



(2.) - - - 4890 -1931 



or but 58 and 39 per cent of the magnesia employed were ob- 

 tained. 



Hence it appears that chlorid of magnesium is far from being 

 completely decomposed by oxyd of mercury after three evapo- 

 rations therewith at 100°, This fact renders H. Eose's directions 

 for the application of Berzelius's method for the separation of 

 magnesia from the fixed alkalies at least doubtful. We are told 

 in the Ilandworterbuch d. Analyt. Chemie (Ausg. v. 1851, Bd. 

 2j p, 45,) to evaporate the mixture with oxyd of mercury to dry- 

 ness, the temperature not being specified, and then to redissolve 

 in water, filter, etc., the mercury being afterwards driven off from 

 the alkaline chlorids and the magnesia separately. 



Fresenius directs the mixed mass to be ignited before the re- 

 solution of the alkaline chlorid in water. The original paper of 

 Berzelius I have not been able to refer to. 



The other modes of separating lithia and magnesia — namely, 

 the precipitation of the latter base by baryta water or by milk 

 of lime, I have carefully tested, and find them both to succeed 

 well. 



Thus — (1.) '9800 grm. of LiCl was dissolved in water, and 

 mixed with the solution in muriatic acid of '2545 grm. of MgO. 

 (2.) ;4866 grm. of LiO, SO 3, and '3004 grm. of MgO dissolved 

 in dilute sulphuric acid were mixed together. To each of these 

 mixtures an excess of baryta water was added, and, after boil- 

 ing, the precipitated magnesia was filtered off and washed. 

 Baryta having been removed from the filtrate by dilute sulphu- 

 ric acid the solution of sulphate of lithia was evaporated to dry- 

 ness, ignited and weighed. 



The magnesia was redissolved in muriatic acid, baryta precip- 

 itated by sulphuric acid, and magnesia thrown down as iimmo- 

 niacal phosphates, in which state it was weighed. 



The results were 



(1.) LiCl -9800 -9829 



(2.) LiO, SO 3 -4866 -4907 



Present. Found. Present. Found. 



MgO -2545 -2533 

 MgO -8004 -2975 



