Dr Daubeny m separating Lime from Magnesia. 807 
monia, the lime alone will Have precipitated ; but that after stand- 
ing a longer time, successive portions of magnesia fall down, 
until the whole is deposited. 
Supposing this statement correct, I should view with some 
suspicion a mode of analysis, which was dependent for it success 
upon the nicety with which we timed the succession of our che- 
mical manipulations, and should conceive that the proportion 
which the precipitant might bear to the substances acted on 
(to say nothing of other contingencies), might alter materially 
the length of lime which was to intervene before the deposition 
of the magnesia. 
The experiments, too, that are detailed above, shew that the 
effect of this re-agent is considerably influenced by the propor- 
tion which the two earths bear to each other, and even lead to 
thefconclusion, that solutions of the sulphates of lime and mag- 
nesia might be mixed in such a proportion with this re-agent, 
as should render both altogether proof against its influencOi 
In order, however, to ascertain this point more fully, I dis- 
solved equal parts of muriate of lime and muriate of magnesia 
in distilled water, and, after adding subcarbonate of ammonia, 
carefully separated within an hour the precipitant which had 
fallen down. 
On examining it, I certainly found that lime was the princi- 
pal ingredient, but very distinct traces of magnesia were afford- 
ed by the application of phosphate of soda. 
On the other hand, a precipitate which afterwards fell, con- 
sisted chiefly of magnesia, with some admixture of lime. 
IV. I cannot, therefore, recommend this last method to the 
adoption of chemists, but shall proceed to consider another for- 
mula for separating the two earths, namely, that of first getting 
rid of the lime by oxalate of ammonia, and afterwards precipi- 
tating the magnesia by the alkalies, or the phosphoric acid with 
' excess of ammonia. 
Confining ourselves to the mode of throwing down the lime, 
we may observe, that one objection to it has been already sug- 
gested, by an experiment which I have detailed in a former part 
of this paper, where the presence of a large proportion of mag- 
nesian salt appeared to diminish the precipitate obtained from a 
