^14 Dr Daubeny on sepa/rating Lime from Magnesia. 
tain the two earths, 1 find, that the addition of fluate of ammo- 
nia will cause a milkiness if lime be present ; but no effect with 
magnesia. 
Should a cloud, therefore, be produced in the acid solution, 
when fluate of ammonia is dropped in, we must continue to add 
the salt so long as any effect continues, then filter the liquor, 
and apply a heat sufficient to expel the acetic acid, when, if any 
magnesia be present, a fresh milkiness may be expected to arise. 
From the foregoing statement, I think we are warranted in 
concluding, that of the methods practised for separating lime 
from magnesia, that founded on the principle of converting the 
two earths into sulphates, is probably the most unexceptionable ; 
and this, accordingly, is the one I have generally pursued in the 
analysis of a magnesian limestone ; although, to ascertain the 
presence of magnesia merely, I have found Dr Wollaston’s by; 
far the easiest and most expeditious. 
The plan, perhaps, which answers best, is the following. 
Dissolve a given portion of the earth in nitric acid, thus se- 
parating the silex, and most of the peroxide of iron, from the 
lime, magnesia, alumine, protoxide of iron, &c. Evaporate the 
solution, and drive off the nitric acid by heat, thus converting 
the iron into a peroxide. Weigh the residuum after calcination, 
and treat it with distilled vinegar, which will only take up the 
lime and magnesia. ' 
Subtract the weight of the undissolved portion from that of 
the residuum after calcination, thus ascertaining the joint weight 
of the lime and magnesia ; then decompose the acetates by sul- 
phate of ammonia ; evaporate the solution nearly to dryness, 
and separate the sulphate of lime from the sulphate of magnesia, 
by repeatedly washing it with water, already saturated with sul- 
phate of lime, as Mr Phillips has recommended. Expose the 
sulphate of lime to a red heat, and ascertain its weight, from 
which the amount of the lime originally present may readily be 
deduced. We may then infer the weight of the m-agnesia from 
the difference between the amount of the lime, and that of the 
whole which the vinegar was found to have dissolved ; or if we 
wish to verify the result, it may be done by precipitating the 
/magnesia by an alkali, or still better, l.)y converting it into a tri- 
iple phosphate. The quantity of sulphate of lime present in the 
