428 J.W. Mallet on the Separation of Lithia and Magnesia. 
The opinion has indeed been expressed by L. Troost,* who 
has lately made some experiments upon the salts of lithia in the 
laboratory of M. Sainte-Claire Deville, that the two bases in 
uestion are so closely analogous, that the only means of sepa- 
rating them is by the employment of caustic potash, which pre- 
cipitates magnesia alone. 
I have felt anxious to examine the grounds upon which this 
opinion rests, and in particular to ascertain whether lime or. 
aryta may not be used with as good result as caustic potash, 
since I had depended upon the former of these earths for the 
purification from magnesia of the salt which I used in determin- 
ing the atomic weight of lithium.+ — 
I first examined the chlorid of lithium which had been pre- 
for the experiments on atomic weight, and found that 
caustic potash did not indicate the presence of a trace‘of chlorid 
of magnesium. 
This chlorid of lithium then, and the sulphate of lithia pre- 
pared from it, might be looked upon as pure salts of the alkali, 
and safely used in the subsequent analytical experiments. “ 
Among the methods in use for the separation of magnesia 
from potash and soda, but three appeared worthy of investiga- 
tion with reference to lithia; the employment of oxyd of mer- 
cury as recommended by Berzelius, precipitation with baryta 
water, and precipitation with milk of lime. Ignition of the mix- 
ture af magnesia and the alkalies with carbonate of ammonia 
does not succeed well with lithia, as H. Rose remarks,t since the 
carbonate of lithia formed is with difficulty and imperfectly ex- 
tracted by water. - : 
In order to test the applicability of Berzelius’s method, the use 
of HgO, the following mixtures were prepared. No. 1, * 
grm. of anhydrous LiCl was dissolved in a little water and added 
to ‘0909 grm. of MgO dissolved in muriatic acid. No 2, ‘5942 
grm. of LiCl and ‘2198 grm. of MgO. 3 ee 
To each of the solutions an excess of oxyd of mercury in V 
some time, and the magne: 
pas a washed, ignited, and wei ; : 
orated to a with the addition of a slight excess of sulphu- 
ric acid, and the sulphate of lithia was ignited and weighed. 
.. The mixture No..1 yielded -6067 grm. of LiO, SOs and ‘2387 
grm.of MgO. No 2 gave ‘7108 grm, of LiO, SOs and 3414 
mci a). , Beatin 10 120 By caleadaien, mod eee 
heresultsfor 100 parts, wehave—- sts 
_* Comptes Rendus, Nov. 10, 1856.~Republished in Chemical Gazette, Dec. 15, 
1856. + This Journal, Nov. 1856. ¢ Handb. d. Anal. Chemie, B. 2, 5. 45- 
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