Dr Daubeny on separating Lime from Magnesia,- 119 
The imperfect manner in which lime is precipitated from its 
solutions by carbonate of ammonia, even where it exists alone in 
"the solution, may be attributed partly to the formation of a su- 
percarbonate of lime, which is to a certain extent soluble in wa- 
ter, and partly to the presence of ammoniacal salts, some of 
which appear to take up a portion of lirrie ^; in addition to 
which, we may probably, in those cases where a magnesian salt 
was present, attribute somewhat to the affinity existing between 
the latter and the calcareous sulphate. 
The first of the causes assigned, is fa,voured by the difference 
of effect produced upon: solutions of sulphate of lime by the bi- 
carbonate and subcarbohate of ammonia. If the former be 
added, the transparency of the solution is not immediately af- 
fected, but the latter renders it instantly turbid. The second I 
infer from the fact, that a solution of muriate of ammonia, after 
having been digested on' carbonate uf lime, is rendered much 
more turbid by oxalate of ammonia than pure water, which had 
been suffered to remain for an equal length of time in contact 
with the same substance, and afterwards filtered. In both in- 
stances the presence of lime was manifest ; but in the case of 
the solution of muriate of ammonia, it was evinced by a preci- 
pitate, whilst in that of the pure water it was indicated by only 
sC slight cloudiness. ■ 
That the solubility of carbonate of lime is also influenced by 
the presence of magnesia, I infer, (independently of the more 
direct evidence to that effect, which will afterwards be adduced), 
from the simple fact that solutions of sulphate of lime, to which 
carbonate of ammonia has been added, do not manifest any 
cloudiness, even after the interval of an hour, if sulphate of mag- 
nesia be present, although solutions similar iii all respects but 
in this become turbid in a much shorter interval, after the ap- 
plication of the same re-agent. 
Owing, however, to the slowness with which carbonate of 
ammonia in all cases operates upon weak solutions containing 
lime, the influence which the presence of magnesia exerts upon 
the effect, may be better seen when the subcarbbnate is employ- 
* I find that Mr Phillips has anticipated me in this remark, although, from 
-having seen originally only some extracts from his paper in the Annals of Philo-^ 
I was not aware of it at the time. 
