Dr Daiibeny on separating Linie frorn Mlrgnesia. 115 
disMved the lime and magnesia in muriatic acid, precipitate 
beth by means of some alkali or alkaliiie carbonate, and ascer- 
tain their weight. Then redissolve them in an acid and fol- 
low the subsequent steps recommended in Mr Phillips’ formula. 
In this manner, provided only that after the ammoniacal salts 
have been driven off by heat, we treat the residuum with such a 
quaiitity of water saturated with sulphate of lime, as will carry off 
the sulphat of magnesia, we may calculate, from the amount of 
sulp^hate of lime left, how much of the precipitate collected in the 
fOriner instance consisted of lime, and therefore what portion of 
it was magnesiav 
Indeed, if this modification of the process be adopted, it will 
be scarcely necessary, unless where great exactnesses required, 
to reduce the sulphate to dryness at all,' as the supernatant li- 
quor, after the addition of the sulphate of ammonia, can only 
cdhtain 1 gr. of’ sulphate of lime in the ounce, and, if in suffi- 
cient quantity, must carry off with it the whole of the magnesian 
and ammoniacal salts: We shMl thus escaipe the risk of apply- 
ing^ such a heat as would drive off a portion of the sulphuric 
aeidy and thereby diminish the solubility of the magnesian salt. 
It has been suggested, however, by Dr Thomson -f-? that the 
presence of magnesia may tend to increase the solvent power of 
water with respect to the calcareous sulphate ; and I felt the 
more desirous of determining this point, as such an idea coin- 
cided with the views which I have found reason to entertain, 
with regard to the influence of the affinity subsisting between 
two bases, in modifying the action of a solvent on one or both 
of them. 
I therefore began by mixing together two solutions, (each of 
S oz.), the one containing about 70 grains of sulphate of mag- 
nesia in the ounce, and the other saturated, or nearly so, with 
sulphate of lime. The mixture was then poured into a long, 
narrow bottle, graduated so as to enable me to observe every suc- 
cessive diminution of volume, and exposed to a gentle but long 
continued heat in a sand-bath. The solution was then slowly 
* Distilled vinegar readily dissolves recently precipitated lime and magnesia, 
but does not act on alumina : it may therefore be conveniently employed in this, 
stage of the process. 
•f* Vide Annals of Philosophy, vol, xv. 
H 2 • 
